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Chemical characteristics of rainwater collected at a western site of Jordan
Atmospheric Research 91 (2009) 53–61
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Atmospheric Research j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / a t m o s
Chemical characteristics of rainwater collected at a western site of Jordan Omar Ali. Al-Khashman ⁎ Department of Environmental Engineering, College of Mining and Environmental Engineering, Al-Hussein Bin Talal University, P.O. Box (20) Ma'an, Jordan
a r t i c l e
i n f o
Article history: Received 23 August 2007 Received in revised form 21 May 2008 Accepted 29 May 2008 Keywords: Rainwater chemistry Chemical elements Statistical analysis Acidity Jordan
a b s t r a c t A comprehensive study on the chemical composition of rainwater was carried out from October 2006 to May 2007 in Ghore El-Safi area western side of Jordan nearby the Dead Sea. Rainwater samples were analyzed for major ions (Ca2+, Mg2+, K+, Na+, NH+4, HCO−3, Cl−, NO−3 and SO2− 4 ) and trace metals (Fe, Al, Zn, Pb, Cu, and Cd). The highest concentration of elements is observed at the beginning of the rainfall season when large amounts of dust accumulated in the atmosphere scavenged by rain. The majority of rainwater had a neutral or alkaline character as a result of neutralization caused by the alkaline local dusts which contain large amount of CaCO3. The pH ranged from 4.8 to 8.2 with a mean value of 6.9 ± 0.65 which was in alkaline range considering 5.6 as the neutral pH of cloud water with atmospheric CO2 equilibrium. In the total 35 rain events, only three events were observed in acidic range (b 5.6) which occurred after continuous rains. The equivalent concentration of components followed the order: Ca2+ N HCO−3 N Cl− N Mg2+ N NO−3 N SO2− 4 N NH+4 N Na+ N K+. Rainwater chemistry was analyzed using Factor Component Analysis to find the possible sources of the measured species. Three components that accounted for 84% of the total variance were extracted sea salts spray (Na+, Cl− and Mg2+), and soil particles (natural origin), (Mg2+, Ca2+ and HCO−3) and biomass burning (NH+4). The results obtained in this study are compared with those other studies conducted at different sites in the world. In general, the results of this study suggested that rainwater chemistry is strongly influenced by local anthropogenic sources (potash factory and agricultural activities in Ghore El-Safi area) rather than natural and marine sources. The pollutants in rainwater samples were mainly derived from long distance transport, local industry and traffic sources. © 2008 Elsevier B.V. All rights reserved.
1. Introduction Rainwater chemistry is an intricate result of a complex interaction between cloud dynamics and the microphysical processes as well as series of rainout and washout atmospheric chemical reactions. The acidity and chemical concentration in rain depend on the source strength of the constituents their physical properties into hydrogeological, chemical transformation during cloud formation and below cloud scavenging (Mouli et al., 2005; Kulshrestha et al., 1999). The study of chemical elements in wet and dry precipitation has increased in the last two decades because of their adverse environmental and human health effect (Baez et al., 2007). Rainwater composition plays an important role in scavenging soluble components from the atmosphere and helps us to understand the relative ⁎ Tel./fax: +962 3 2179000. E-mail address: [email protected]. 0169-8095/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.atmosres.2008.05.007
contribution of different sources of atmospheric pollutants (Kulshrestha et al., 2003). The composition of rainwater actually reflects the composition of the atmosphere through which it falls. The study of composition of wet deposition encourages to evaluate the relative importance of the different sources for gases and particularly matter (Demirak et al., 2006).Wet precipitation constituents are the most effective scavenging factor removing particulate and organic and in organic gaseous pollutants from the atmosphere. The scavenging of the atmospheric pollutants affects the chemical composition and the pH of rainwater. The acidic precipitation is primarily caused by incorporation of anthropogenic sources such as SOx, NOx and other acid precursors (Das et al., 2005; Migliavacca et al., 2005). On the other hand, neutralization of acidity in rainwater can be either due to CaCO3 in airborne dust (Munger, 1982; Al-Momani et al., 1995) and or ammonia released from industrial, agricultural and other natural sources (Schuurkes et al., 1988). Chemical composition of rainwater in the Mediterranean region
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and factor affecting these compositions are fairly well established through studies performed since 1980s. There are two main sources that strongly affect the composition of atmospheric particles and precipitation in the Mediterranean basin. The first is the eolian dust transported from North Africa (Kubilay and Saydam, 1995) while the second is the pollution of aerosol transported from Europe (Bergametti et al., 1989; Gullu et al., 1998; Tuncer et al., 2001; Al-Khashman, 2005). Jordan is situated 80 km to the east of the Mediterranean Sea; the climate of Jordan is predominantly of the Mediterranean with hot and dry summers and cold wet winters with two short transitional periods in autumn and spring. During these short transitional periods most convective activity occurs produces producing thunderstorms. Rainfall decreases from north to south and from west to east and from higher to lower elevation (Shehdeh,1991; Al-Khashman, 2005). The aim of the present study is to gain an initial understanding of rainwater chemistry and to identify possible sources of the various constituents of precipitation in the study area. The results obtained in this study are compared with other studies at various places in the world. 2. Materials and methods 2.1. Study area and sample collection Ghore El-Safi area is located in the western part of Jordan nearby the Dead Sea. It is bounded by longitude 35° 28′ N and latitude 31° 2′ E about −350 m above sea level and about 8 km
east from Dead Sea (Fig. 1). It can be classified as mixed between rural/industrial and agricultural surrounding. Ghore El-Safi average rainfall was 77 mm/year and the daily mean humidity was 54.8% with the temperature ranging from the minimum of 10.4 °C to maximum of 22.2 °C. The winter season in Jordan is the principle season of rainfall, the water year starts in early October to May. The prevailing wind direction is from southeast to southwest in winter season, but in the summer season the prevailing wind direction is from northwest, this wind bringing cold wet air during winter and spring from Europe and Mediterranean sea and from the east and south bringing hot dry air during summer and autumn from Saudi Arabia, Africa and India (Shehdeh, 1991). Geologically, the southern part of the investigated area is composed of Precambrian basement complex of metamorphic and a plutonic rock exposed along the eastern rim of Wadi Araba (Bender, 1974). Cambrian overlies the Proterozoic basement to tertiary sediments, but the lower cretaceous sediments are exposed along the eastern side of the Dead Sea– Wadi Araba section of the rift province. Two units are distinguished in the lower cretaceous sequence a lower unit of massive, white sandstones and an upper one of varicolored sandstone. The upper Cretaceous strata were not found in outcrops in the investigated area. Thick bed of conglomerate Neogene related to the tectonic activities unconformable unconformably overlies the basalt and Quaternary sediments beside superficial sediments of Holocene to recent sediments (Bender, 1974).
Fig. 1. Location map of the studied area.
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The investigated area is surrounded by areas almost exclusively devoted to agriculture and has low residential density. Ghore highway lies about 1.5 km from the sampling site, while the Potash factory lies nearby the investigated area. The rainwater samples were collected on event basis with wet only collectors, for a period of one rainy year (October 2006 to May 2007) in Ghore El-Safi station located almost in the central part of the study area. The station is surrounded uniformly by almost all activities that exist in the investigated area. Samples were collected on the roof of the station building about 8 m from ground level and 1 m from the floor of the roof. Sampling was done manually on an event basis, using only wet collector, which were fitted with a polyethylene bottle and polyethylene funnel 26-cm in diameter (Mouli et al., 2005). Sample collection equipment used on an event basis were was washed with detergent and HNO3 and then rinsed with double deionized water (DDW). The collectors (bottles and funnels) were deployed as soon as the rain began and were retrieved immediately after they were filled up or after the rain stopped. 2.2. Sample analysis A total of 35 samples had sufficient volume for analysis of the studied parameters, which represented about 85% of the total rainfall of the season in the study area. Rain collected by the funnel was gravity filtered through a 0.45 µm pore size membrane filter to remove the insoluble particles, and then collected in the collection bottles. The funnel was stored in a clean plastic bag and was brought out to be mounted on the stand (2.5 m height) just before the rain. Each sample was divided into two bottles; the first part was used to collect + samples for Cl−, NO−3, SO2− 4 , NH4 and pH measurements. The receiving bottle connected to this part was rinsed several times by deionized water and dried before use. The other part was connected to an acid-washed bottle. These bottles were soaked in 20% HNO3 for about one day and rinsed several times with deionized water and dried before use. After that, samples collected in acid-washed bottles were acidified by adding 1 ml (5%) reagent-grade HNO3 to prevent adsorption of the metals by the surface of the polyethylene bottles and to adsorb them out of the dust particles (Al-Khashman., 2005; Al-Momani, 2003; Al-Momani et al., 2000). Rainwater from this sampler was used for the determination of major cations and trace metals. The rainwater samples were collected soon after each rainfall, and kept in a refrigerator at 4 °C until subjected for ion and metal analysis, which was usually performed within two days after collecting samples. The pH values of the collected samples were measured for unacidified samples using 370 JENWAY pH meter equipped with a combination glass electrode. Calibration was always carried out before measurement using standards buffer solutions of pH 4.00 and 7.00. To avoid junction potential errors due to low ionic strength of rain samples, pH measurements were carried out after adjusting samples to 0.02 M with respect to KCL (Nguyen and Valenta,1987). Conductivity measurements were carried out with 470 JENWAY conductivity meter with temperature compensation (Al-Khashman., 2005). The concentration of NH+4 was determined spectrophotometrically using the Nessler method. Major cations (Na+, K+, Ca2+ and Mg2+) were measured by 800 Varian Flame Atomic Absorption Spectrophotometer (Table 1). The concentrations of cations were
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Table 1 Analytical method used to determine rainwater parameters Lab parameter
Analytical method
pH value Conductivity (µs/cm) Bicarbonate (HCO−3)
370 JENWAY pH meter 470 JENWAY conductivity meter Titration with 0.01 hydrochloric acid using methyl orange 100 Dionex Ion Chromatography instruments 800 Varian Flame Atomic Absorption Spectrophotometer Nessler method Graphite Furnace Atomic Absorption Spectrophotometer
F−, Cl−, NO−3 and SO2− 4 Na+, K+, Ca2+ and Mg2+ NH+4 Trace metals (Fe2+, Al3+, Mn2+, Cu2+, Ni2+, Zn2+ and Pb2+)
determined using a CS12 analytical column, CG 12 guard column, using 20 µm CH4SO−3. The concentration of bicarbonate was determined by titration with 0.01 hydrochloric acid using methyl orange as indicator. Major anions (F−, Cl−, NO−3 and SO2− 4 ) were analyzed by 100 Dionex Ion Chromatography instruments equipped with AG4A-SC guard column, AS4ASC separating column, SSR1 anion self regeneration suppresser and conductivity detector. The samples were injected through 25 MI sample loop and eluted at 2.0 ml min-I using 1.7 µm NaHCO3 and 1.8 µm Na2CO3. The system was calibrated with a certified standard from Dionex. Trace metals (Fe2+, Al3+, Mn2+, Cu2+, Ni2+, Zn2+, and Pb2+) were analyzed with Graphite Furnace Atomic Absorption Spectrophotometer (GF-AAS) using a Varian model GTA 100 instrument. The GF-AAS was calibrated using the method of the standard addition. The standard solution of the anions, cations and trace metals as well as blank samples was prepared with different concentrations. All standard solutions were made daily by diluting the stock solutions with 0.01 M HNO3 (Virkutyte and Sillanpåå, 2006), which was prepared from analytical grade HNO3 solution obtained from Merck. Analysis of field blanks showed that contamination during the sampling procedure transport and analysis was negligible. The sampling water bottles were removed immediately and processed in the same manner as the precipitation samples. Detection limits of the ions, concentrations corresponding to three times the standard deviation of ten replicate blank level measurements were 0.04 µg ml− 1 for Cl−, 0.09 µg ml− 1 for Na+, 0.03 µg ml− 1 for K+, and 0.06 µg ml− 1 for Mg2+, 0.11 µg ml− 1 for Ca2+, 0.04 µg ml− 1 for Cd2+, 0.06 µg ml− 1 for Cu2+, 0.05 µg ml− 1 for Fe2+ and below 0.21 µg ml− 1 for the rest of the trace metals. A quality control procedure, including, recalibration of the instruments, analysis of triplicate samples and recovery test of standard reference material was used to control data quality. All chemicals and reagents used in this study were of analytical grade unless otherwise stated. Deionized water (Milli-Q 8.2 µs/ cm) was used for all dilutions. Standard solutions were prepared by diluting the stock solutions. To prevent the sample contamination with trace metals, all the glassware, Pyrex and plastic containers were washed several times with soap, deionized water and treated with 0.01 M HNO3 and finally rinsed with ultra-pure water. 3. Results and discussion The chemical composition of 35 rainwater samples collected from Ghore El-Safi area from October 2006 to May
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Table 2 The mean concentrations of major ions in rainwater at selected sites worldwide Parameters
This study
Italy a
Galilee b, Israel
Tirupati c, India
Mexico d, USA
Melle e, Belgium
Spain f
Tibetan China g
pH EC Ca2+ Mg2+ Na+ K+ NH+4 HCO−3 Cl− NO−3 SO2− 4
6.91 ± 0.65 95.00 ± 97.11 165.32 ± 0.79 93.12 ± 0.51 130.56 ± 0.31 85.21 ± 0.28 75.36 ± 0.82 133.65 ± 0.18 142.36 ± 0.24 67.31 ± 0.63 112.36 ± 0.58
5.18 – 70.00 77.00 252.00 17.00 25.00 – 322.00 29.00 90.00
– – 44.70 28.00 166.00 3.70 24.30 – 176.30 28.00 150.30
– – 150.66 55.51 33.08 33.89 20.37 – 33.91 40.84 127.96
– – 34.60 3.69 4.52 2.04 95.00 – 9.29 42.86 76.67
5.19 – 26.87 9.25 36.98 1.96 65.65 – 33.37 31.26 47.32
6.40 – 57.50 9.80 22.30 4.00 22.90 – 28.40 20.70 46.1
6.59 19.70 65.58 7.43 15.44 14.49 18.13 72.34 19.17 10.37 15.50
Concentrations were in µeq/l, except EC (µs/cm− 1) n = 35. a Le Bolloch and Guerzoni (1995). b Herut et al. (2000). c Mouli et al. (2005). d Baez et al. (2007). e Staelens et al. (2005). f Avila and Alarcon (1999). g Li et al. (2007).
The analysis consists of chemical composition including ions and trace metals in addition to pH and conductivity. The highest number of events in a month were was seen during February (18.6) followed by January (8.20), and less amount of
rainfall was seen in September, while the monthly average rainfall during the study period is depicted in Fig. 2. The ratio of total cations to that of anions (∑cations/∑anions) is an indicator for the completeness of measured parameters. The average equivalent sum of cations to that of anions ((∑cations/ ∑anions) was 0.86 ± 0.19. The less than unity ratio suggests that a major anion was not measured. The soil in the region is calcareous, indicating that the observed anion deficiency is more likely due to exclusion of bicarbonate from the measurement (Al-Momani et al., 1995; Al-Momani, 2003; AlKhashman, 2005). After computing the concentration of bicarbonate (Granat, 1972), assuming that the concentration of CO2 in the atmosphere is 350 ppm, the average ((∑cations/ ∑anions)) ratio was raised to 0.92 ± 0.22. The average volume weighted concentrations of ions in the investigated area are shown in Table 2 together with those found by others in areas around the world. The concentration of HCO−3 concentration is estimated by ionic balance of the total cations and anions, assuming that the CO2− 3 concentration is negligible. The sulfate concentration (112.36 µeq/l) was found to be very high when compared with those in the literature for similar sampling sites on the world except for the Galilee in Israel (150.30 µeq/l) and in Tirupati in India (127.96 µeq/l). The nitrate value (67.31 µeq/l) was also found to be one of the highest concentrations. The high sulfate
Fig. 2. The monthly rainfall in the study area during the period (1974–2004), (WAJ, 2006).
Fig. 3. Frequency distribution of pH in rainwater samples.
2007 was utilized in this study. The mean ion concentrations for all samples are presented in Table 2. The pH of rainwater samples ranged from 4.81 to 8.24, with an averaged 6.9 ± 0.65 which is in the alkaline range. The pH of rainwater in a clean atmosphere is generally around 5.6 due to the dissolution of CO2 in rain droplets (Boubel et al., 1994; Bayraktar and Turalioglu, 2005). As to pH data, the distribution of pH revealed that the largest fraction 77.2% of all samples had a pH N 5.6, while about 22.8% of rainwater samples had a pH b 5.6. Most pH values ranged between 7.5 and 8.5 (42.8%), while only 22.8% of the rainwater samples had pH values between 5.5 and 4.5. The highest pH (8.2) was observed in the samples collected in the months of April and May and coincided with sulfate, chloride and nitrate concentrations of 3.35 meq/l, 3.71 meq/l and 3.91 meq/l respectively. On the other hand, the lowest pH was associated with the highest value of sulfate (8.69 meq/l) and an average nitrate value of 3.71 meq/l, while the pH increases slightly from winter to summer. 3.1. Major ion concentrations
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Fig. 4. Contribution of ions to total ion mass.
and nitrate concentrations produce medium pH value in some events. The concentration of Ca2+ is higher than those reported from Italy, Galilee, Triupati, Mexico, Melle and Spain. The higher concentration is due to the large contribution of the Saharan soil dust, which contains large fraction of calcite (Basak and Alagha, 2004; Al-Momani, 2003). The high contribution of Ca2+ and HCO−3 is mainly due to the influence of the continental dust rich in carbonate materials (Li et al., 2007). The concentration of marine elements (Cl−, Na+ and SO2− 4 ) were was much higher in Tirupati in India, Mexico in USA, Melle in Belgium and Spain. NH+4 was much higher in precipitation in USA compared to Jordan. The high values of NH+4 in Ghore area were due to the high level of fertilizer use in agricultural activities, in addition to the contribution of other human activities (Al-Momani et al., 1995; Mouli et al., 2005; Al-Khashman., 2005). 3.2. Chemical composition of rainwater The mean pH value of rainwater has been observed to be 6.9 which is in the alkaline range. The highest acidity was observed on the 8th of December 2006 with a pH of 4.81, while, the lowest was on the 7th of March 2007 with a pH of 8.24. Fig. 3 shows the percent frequency distribution of pH for the rain water samples collected during the rainy season. The observed alkalinity of precipitation is due to high loading of carbonate, bicarbonate of calcium particulate in the atmosphere commonly abundant in the region conditions. The suspended
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particulate material which is rich in carbonate/bicarbonate of calcium buffers the acidity of wet precipitation (Kulshrestha et al., 2003). The concentration of ions in different rainwater samples is shown in Fig. 4. The chemical composition of major ions in rainwater was listed in Table 2. It clearly shows that the mean concentration of ionic species in rainwater follows the + + + order of: Ca2+ N HCO−3 N Cl− N Mg2+ N NO−3 N SO2− 4 N NH4 N Na N K . Among all the ions, Ca2+ ion makes the highest contribution to the total mass of the ions. It accounts for (17%) followed by HCO−3 (15%), while the Na+ ion makes a relatively moderate contribution compared to Cl− and NH+4 ions. The contributions of Mg2+ and Cl− were 12% and 13% respectively. The sulfate and nitrate ions make a relatively moderate contribution compared to other ions. Bicarbonate ion represents 31% of the total anion mass which was the highest anion contribution, while the highest value of carbonate was measured during warmer dusty storms. The lowest value of bicarbonate was measured during the coldest month of the rainy season, high intensity of precipitation and low dust in the atmosphere (Fig. 5). The contribution of chloride accounts 27% of the total mass of anions in rainwater samples. The highest values of Cl− in rainwater samples were due to the Khamasini wind, in which the region was affected during the spring season and sea salts spray (marine source). However, the Mg2+ ion makes 24% of the total cation mass, which was the highest contribution after Ca2+. The observed Mg2+ values in rainwater samples are generally affected by both sea salt and dust particles in the atmosphere. The contribution of marine sources on observed Mg2+ concentrations is approximately 30%, and the rest being crustal source. The mean concentrations of Na+ and K+ ions account for 16% and 8%, respectively of the cation mass. However, the origin of Na+ and K+ were was mainly derived from the dust sea salts, and the aerosols of the Dead Sea, Mediterranean Sea and polar depressions affected Jordan during the rainy seasons (AlKhashman., 2005). However, NO−3 ion makes a relatively medium contribution compared to Cl− and SO2− 4 . The main sources of NO−3 in the rainwater samples are industries located beside the investigated area such as; potash factory, cement factory and phosphate mines in south Jordan and airborne fertilizer particles. However, motor vehicle emissions make a significant contribution during the dry season when transport
Fig. 5. The monthly mean concentrations of some ions.
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and tourist vehicles traffic increases (Al-Momani et al., 1995). The agricultural activities in Ghore area beside the intense thunderstorms caused higher concentrations of nitrate in rainwater samples. The SO2− 4 ion makes 23% of the total mass of anions, which was the highest contribution after bicarbonate and chloride. The high concentration of sulfate in rainwater samples in the study area in air masses originating from sea salt and from soil dust comes from North Africa and deserts around the country which contain a large fraction of calcite, dolomite, gypsum and halite and clay minerals (Foner and Ganor, 1992). On the other hand, the possible source of SO2− 4 in the atmosphere can be derived from SO2 in the air as well as dry deposition of particles over the study area, as a large amount is produced through fuel combustion during the cold winter months (Al-Khashman., 2005). The monthly mean values of 2+ − + SO2− ions in rainy season found in collected 4 , NO3, NH4 and Ca samples were given in Fig. 5. 3.3.
Table 4 Correlation matrix between ions in rainwater samples; cells show the Pearson correlation coefficient and the corresponding P-value Variables Ca Mg2+ +
Na K+
NH+4 HCO−3 Cl− NO−3 SO2− 4
− SO2− 4 /NO3
− The calculated SO2− 4 /NO3 ratio may indicate that the anthropogenic sources in the atmospheric rainfall of industrial areas and the result obtained in the study area were compared to those from other studies (Table 3). They show that this ratio was lower than the ratios found in other studies such as Guaiba, Figueira, Singapore, Galilee, Erzurum, Mexico and Spain. It was, however, higher than the ratio found in Mexico. This might be due to the fact that the locations are − located near or in industrialized urban areas. SO2− 4 and NO3 are ions usually found in rainwater samples and their contribution to the acidity of precipitation is found. The relative contribution by these ions in the acidity of rainwater is variable for event to event. It is estimated that the contribution of H2SO4 in rainwater samples is 60–70 and that of HNO3 is 30–40% (Al-Momani et al., 1995; Tuncer et al., 2001; Migliavacca et al., 2005; Al-Khashman., 2005). Therefore, the contribution of H2SO4 to the acidity of rainwater has decreased compared to HNO3. This is directly related to the control of emitting sources, as well as to the reduction of sulfur contents in oil by-products, in contrast to less stringent controls on NOx emissions, especially in the US and Europe (Byron et al., 1991; Khawaja and Husain, 1990; Al-Momani et al., 1995).
3.4. Statistical analysis 3.4.1. Ionic correlation In order to identify the possible relationship between the various ionic species in rainwater samples, linear regression Table 3 − SO2− 4 /NO3 comparison ratio at various locations in the world Locations
− SO2− 4 /NO3
References
Present study Guaiba Figueira Singapore Galilee Erzurum Mexico Spain
1.20 8.70 5.30 3.50 5.37 11.60 0.75 2.22
Migliavacca et al. (2005) Flues et al. (2002) Balasubramanian et al. (2001) Herut et al. (2000) Bayraktar and Turalioglu (2005) Baez et al. (2007) Avila and Alarcon (1999)
Ca2+
Mg2+
Na+
K+
NH+4
HCO−3
Cl−
NO−3
0.80 0.00 0.50 0.00 0.33 0.00 0.51 0.00 0.76 0.00 0.77 0.00 0.53 0.00 0.75 0.00
0.71 0.00 0.25 0.00 0.76 0.00 0.71 0.00 0.74 0.00 0.33 0.00 0.44 0.00
0.59 0.00 0.70 0.00 0.59 0.00 0.79 0.00 0.30 0.00 0.28 0.00
0.72 0.00 0.61 0.00 0.72 0.00 0.16 0.00 0.02 0.01
0.22 0.00 0.61 0.00 0.63 0.00 0.58 0.00
0.76 0.00 0.29 0.00 0.44 0.00
−0.20 0.01 0.68 0.00
0.85 0.00
2+
analysis was carried out. Table 4 gives the Pearson correlation coefficients computed from 35 samples. Strong correlation 2 − was seen between SO2− 4 and NO3 (R = 0.85) indicating their origin from similar sources. This was due to similarity in their behavior in precipitation and the co-emission of their precursors NOx and SO2. The reason for nitrate and sulfate might be due to accumulation of these ions in the upper atmosphere being washed down with rains during the cold season. Besides, anthropogenic sources and agricultural activities in the study area may contribute more concentrations of these ions during summer and autumn (Al-Khashman, 2005). Ca2+ showed strong correlation with Mg2+ (R2 = 0.80), suggesting the common source of these ions from natural source (crustal origin). This was due to calcareous nature of the soil and the frequent input of Saharan soil dust during the spring season. Other relative good correlations were observed between Ca2+ 2+ and SO2− and Cl− and Mg2+ and Cl−, Mg2+ and NH+4, Mg2+ 4 , Ca − and HCO3 (Table 4). Significantly good correlation was seen between Na+ and Cl− (R2 = 0.79) and also, both showed good correlations with Mg2+ (R2 N 0.70), indicating towards a common sea sea-salt origin (marine source). However, moderate correlation was found between sodium, chloride and sulfate and calcium indicate indicating towards the existence of sea sea-salt particles that are deposited on the local soil (Safai et al., 2004). The ammonium ion was correlated with SO2− 4 (R2 = 0.64), on the other hand, other relatively good correlations noticed between NH+4 and Cl−, and between NH+4 and NO−3 were R2 = 0.61 and 0.58, respectively. The ammonium compounds applied to soil can escape into the atmosphere by means of gaseous NH3 or as NH4NO3 and (NH4)2SO4 particles. When NH4NO3 and (NH4)2SO4 particles were incorporated in precipitation, they change NO−3 and SO2− 4 values, but do not
Table 5 Ratio values of the major ion components of rainwater samples and the corresponding values for sea water
Rainwater Seawater
Cl−/Na+
K+/Na+
Mg2+/Na+
Ca2+/Na+
+ SO2− 4 /Na
1.09 1.80
0.65 0.037
0.71 0.038
1.30 0.12
0.68 0.25
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affect the pH. However, when ammonium was incorporated in the rain, it can neutralize the acidity of rainwater (Al-Momani et al., 1995). However, in order to determine the marine contribution in the composition of rainwater the ratio of sea salts were was calculated considering the sodium as sea sea-salt tracer, assuming that all sodium to be of marine origin. The calculated ratios for rainwater deviated considerably from the seawater ratios (Table 5), indicating a modification of the sea sea-salt constituents along the trajectory of the air masses. The observed Cl−/Na+ ratio (1.09) is much lower to that of seawater ratio (1.8) suggesting either a fractionation of Cl− or enrichment of Na+ (Eriksson, 1959; Mouli et al., 2005). The + elevated K+/Na+, Mg2+/Na+, Ca2+/Na+ and SO2− ratios 4 /Na (Table 4) indicate the possible contribution of other components probably from the soil dust affecting the study area. 3.4.2. Principle component analysis (PCA) Statistical analyses were performed with SPSS for window; 10.0.5 data were log-transformed prior Principle Component Analysis (PCA) to reduce the influence of high data (Moller et al., 2005). PCA was applied to assist in the identification of the source of ions in the rainwater samples by using factor extraction with an Eigenvalue larger than 1 after varimax rotation. The result of statistical analysis was given in Table 6. The loadings having a greater value than 0.70 are marked bold in the table. Factor 1 accounts for 28.5% of total variance and has high 2+ 2+ loading for Cl−, NO−3 and SO2− and Na+ in decreasing 4 , Ca , Mg order; good positive correlations among the ions are found in the correlation matrix analysis. The results of correlation analysis are given in Table 3. For example, the correlation coefficient between Cl− and Ca2+ is 0.77, between Cl− and Mg2+ is 0.74 and between Cl− and SO2− 4 is 0.68. This factor is associated with soil and sea-salt sources. The association sodium and chloride in factor 1 indicates the presence of sea salts arriving in masses of polar sea air (Lee et al., 2000; Mello, 2001). Mg2+ and Ca2+ probably originate from natural sources (soil) and they contribute to neutralization reactions that occur in atmospheric precipitation (Saxena et al., 1996; Migliavacca et al., 2005; Ganor et al., 1991). However, factor 1 shows high loadings for sulfate, chloride and nitrate and this may be related to long-range transport of anthropogenic origin, deriving from human activities from industrial countries (AlKhashman., 2005). The second factor, with 24.3% of the total
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Table 7 Mean mass contribution from identified sources for rainwater Source
Mean contribution
Percentage of total predicted mass
Soil dust (natural) Anthropogenic Sea spray (marine) Total predicted mass Total estimated mass R (predicted/observed)
442.1 ± 35.2 138.6 ± 13.4 125.7 ± 17.6 706.4 ± 49.1 708.1 ± 34.5 0.99
62.6 19.7 17.7 – – –
(meq/l for the rainwater parameters).
variance, showed Mg2+, Na+, HCO−3 and Ca2+ in decreasing order. This factor is associated with soil source (natural origin). There is a good correlation among the ions, which belong to the second factor, the correlation coefficient between HCO−3 and Ca2+ is 0.76 and between HCO−3 and Mg2+ is 0.71. The high concentration of carbonate materials in rainwater samples is due to large contribution of Saharan soil dust, which contains large fractions of CaCO3, MgCO3 and MgSO4. The third factor, explaining only 15.9% of the total variance, showed the ions K+ and NH+4 with higher values, suggesting biomass burning. The ammonium found atmospheric wet deposition might come from several sources, including the volatilization of animal manure, human excrements, natural loss by plants, fertilizers and agricultural activities (Migliavacca et al., 2005). Based on the statistical analysis, factor 1 represents the contribution of ions from local anthropogenic activities, but the factor 2 represents the contribution of ions from a natural source. On the other hand, factor 3 suggests biomass burning and anthropogenic source. The mean mass contribution from identified sources for rainwater samples is presented in Table 7. In Table 7, the data from the PC analysis with respect to mean mass contribution from identified by PCA sources is presented. It could be seen that for rainwater samples the marine origin delivers the dominant quantity of potassium, sodium and chloride; the anthropogenic source emitters deliver mainly ammonium and nitrate with additional contribution of chlorides and sulfates. Soil dust (Saharan soil dust) contribution is mainly calcium, magnesium and bicarbonate with additional contribution of sulfate and chloride in rainwater samples. 3.5. Trace metals The statistical analysis of metal values in rainwater samples at Ghore El-Safi area during the rainy season were was presented in Table 8. The mean values for Fe, Al, Zn, Pb,
Table 6 Factor analysis of chemical constituents in precipitation Parameters
Factor 1
Factor 2
Factor 3
Communities
pH EC Ca Mg Na K NH4 HCO3 Cl NO3 SO4 Total variance %
−0.84 −0.21 0.51 0.61 0.31 0.17 0.12 0.19 0.85 0.95 0.94 28.5
0.27 0.45 0.45 0.71 0.81 0.31 −0.21 0.82 0.40 0.11 −0.18 24.3
−0.17 −0.31 −0.14 0.33 0.41 0.76 0.66 −0.28 0.12 −0.12 0.18 15.9
0.822 0.876 0.783 0.913 0.931 0.809 0.952 0.740 0.948 0.931 0.947
Table 8 Concentrations of trace metals in rainwater samples (ppb) Element
Mean
Standard deviation
Fe Al Zn Pb Cu Cd Ni Cr
430 324 210 66 73 52 3.5 3.1
75.51 61.74 44.21 33.25 23.10 19.13 2.24 2.01
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atmospheric pollution and the soil dust which affect the composition of wet atmospheric deposition. 4. Conclusion
Fig. 6. The contribution of metals in different rainwater samples.
Cu, and Cd were 56, 40, 18, 22, 20, 12, µg− 1, respectively. The variation of concentration of these metals in rainwater samples can be explained by the scavenging of pollutants (Al-Khashman., 2005). The variation in the values of trace metals between different rainfall events could be related to the source of pollutant emissions. The high concentrations of metals were measured in wet deposition after periods of dryness, while low values of metals were measured when rain continued for several days. The values of each metal in rainwater are shown in Fig. 6. The relative abundance in rainwater (µg− 1) observed were was Fe N Al N Pb N Cu N Zn N Cd depending upon their evaporation rate, relative concentration of metals in rainwater samples and solubility of their metals. The maximum concentration value appeared in the beginning of the rainy season, because of the fact that there is a large amount of pollutants soluble in less solvent (Fig. 7). Metal concentrations in rainwater had a great variability according to the direction of atmospheric depression, metrological conditions and the amount of rainfall. In this study, the highest concentration of metals was shown during the period from January to March (Fig. 7). Moderate correlation between anthropogenic elements Cr and Zn (R2 = 0.61), Cr and Cu (R2 = 0.66) and Zn and Cu (R2 = 0.69). Strong correlation was observed between lead and copper (R2 = 0.81) and lead and zinc (R2 = 0.78) in samples indicating their origin from similar sources. The high values of metals in rainwater samples may be due to long-range atmospheric transport of anthropogenic activities from other parts of Europe and local point sources of
Investigation of chemical composition of rainwater was carried out in the western side of Jordan (Ghore El-Safi area) nearby the Dead Sea during the period (October 2006 to May 2007). This study is essential for establishing a data base about the rainwater quality around one of the most important watersheds in the south region of Jordan. The mean pH of rainwater was 6.91 ± 0.65 well above 4.8, which is the reference pH of rainwater while pH ranged between 4.8 and 8.2. The study revealed that rainwater in the area is alkaline, while the acidity in the rainwater is largely neutralized by Ca2+ and Mg2+ whereas NH+4 played a minor role. The major ions and their concentrations in rainwater followed the order + + + of: Ca2+ N HCO−3 N Cl− N Mg2+ N NO−3 N SO2− 4 N NH4 N Na N K . Sulfate and nitrate were the major acidifying ions in rainwater of the study area. The chemical composition of rainwater in the study area is influenced by either local condition such as; the Dead Sea, agricultural activities in the Ghore area or remote sites associated with depressions rich in calcite, dolomite and gypsum and polar and Mediterranean depressions rich in sulfate and nitrate ions. There was a strong correlation between Ca2+ and Mg2+, Ca2+ and HCO−3, Ca2+ and 4+ Cl−, Ca2+ and SO2− and SO2− 4 and NH 4 . Other moderate correlations were observed between NH+4 and Cl− and between 2+ NH+4 and NO−3 and SO2− makes the 4 . Among the ions, Ca − − highest contribution followed by HCO3, Cl and SO2− 4 indicating the incorporation of soil dust into the rain samples, which reflects a major crustal influence. The relatively moderate concentration of NH+4 observed at the study area is suspected to be due to the surrounding agricultural activity. This agricultural activity has been found to be effective not only in winter and spring, but also in summer, and autumn to cause the neutralization of the rainwater. The use of factor analysis facilitates the interpretation of the rainwater chemistry characterization, highlighting the influence of the anthropogenic sources in the study area. The results of this study are related to various sources, such as soil dust, sea salts, agricultural and biomass burning. The concentration of trace metals (Fe, Al, Zn, Pb, Cu, and Cd) that were determined in the rainwater samples was relatively low. The main source of trace metals in rainwater were was anthropogenic sources.
Fig. 7. The monthly mean concentrations of metals in rainwater samples.
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Acknowledgements The author would like to acknowledge Dr. Abdelaziz L. AlKhlaifat (Director of Prince Faisal Center for Dead Sea, Environmental and Energy Research at Mutah University) for his help and critical reviewing of the text.
References Al-Khashman, O., 2005. Ionic composition of wet precipitation in the Petra region, Jordan. Atmos. Res. 78, 1–12. Al-Momani, I.F., 2003. Trace elements in atmospheric precipitation at northern Jordan measured by ICP-MS: acidity and possible sources. Atmos. Environ. 37, 4507–4515. Al-Momani, I., Tuncel, S., Eler, U., Ortel, E., Sirin, G., Tuncel, G., 1995. Major ion composition of wet and dry deposition in the eastern Mediterranean basin. Sci. Total Environ. 164, 75–85. Al-Momani, I.F., Jaradat, Q.M., Al-Momani, K., 2000. Chemical composition of wet precipitation in Irbid, Jordan. J. Atmos. Chem. 35, 47–57. Avila, A., Alarcon, M., 1999. Relationship between precipitation chemistry and metrological situations at a rural site in NE Spain. Atmos. Environ. 33, 1663–1667. Baez, A.P., Belmont, R.D., Garcia, R.M., Torres, M.C., Padilla, H.G., 2007. Rainwater chemical composition at two sites in Central Mexico. Atmos. Res. 80, 67–85. Balasubramanian, R., Victor, T., Chun, N., 2001. Chemical and statistical analysis of precipitation in Singapore. Water Air Soil Pollut. 130, 451–456. Basak, B., Alagha, O., 2004. The chemical composition of rainwater over Buyukcekmece Lake, Istanbul. Atmos. Res. 71, 275–288. Bayraktar, H., Turalioglu, F.S., 2005. Composition of wet and bulk deposition in Erzurum, Turkey. Chemosphere 59, 1537–1546. Bender, F., 1974. Geology of Jordan, Gerbruder Borntraeger, Berlin. Germany. Bergametti, G., Dutot, A.L., Buart-Menard, P., Losno, R., Remoudaki, E., 1989. Seasonal variability of elemental composition of atmospheric aerosol particles over the north western Mediterranean. Tellus 41B, 353–361. Boubel, R.W., Fox, D.L., Tuner, D.B., Stern, A.C., 1994. Fundamentals of Air Pollution. Academic Press, San Diego, CA. Byron, E.R., Axler, R.P., Goldman, C.R., 1991. Increased precipitation acidity in the central Sierra Nevada. Atmos. Environ. 21, 271–275. Das, R., Das, S., Misra, V., 2005. Chemical composition of rainwater and dust fall at Bhubaneswar in the east coast of India. Atmos. Environ. 39, 5908–5916. Demirak, A., Balci, A., Karaoglu, H., Tosmur, B., 2006. Chemical characteristics of rainwater at urban site of south western Turkey. Environ. Monit. Assess. 123 (1–3), 271–283. Eriksson, E., 1959. The yearly circulation of chloride and sulfur in nature: meteorological, geochemical and pedological implications, part 1. Tellus 11, 375–403. Flues, M., Hamma, P., Lames, M.J.L., Dantas, E.S.K., Fornaro, A., 2002. Evaluation of the rainwater acidity of a rural region due to a coal-fired power plant in Brazil. Atmos. Environ. 36, 2397–2404. Foner, H.A., Ganor, E., 1992. The chemical and mineralogical composition of some urban atmospheric aerosols in Israel. Atmos. Environ. 26, 125–133. Ganor, E., Foner, H.A., Brenner, J., Neeman, E., Lavi, N., 1991. The chemical composition of aerosols setting in Israel following dust storms. Atmos. Environ. 25A, 2665–2670.
61
Gullu, G., Olmez, I., Aygun, S., Tuncel, G., 1998. Atmospheric trace elements concentrations over the eastern Mediterranean Sea: factors affecting temporal variability. J. Geophys. Res. 103, 21943–21954. Herut, B., Starinsky, A., Katz, A., Rosenfeld, D., 2000. Relationship between the acidity and the chemical composition of rainwater and climatological conditions a long a transition zone between large deserts and Mediterranean climate. Israel. Atmos. Environ. 34, 1281–1292. Khawaja, H.A., Husain, L., 1990. Chemical characterization of acid precipitation in Albany, New York. Atmos. Environ. 24A, 1869–1882. Kubilay, N., Saydam, A.C., 1995. Trace elements in the atmospheric particulates over eastern Mediterranean; concentrations, sources and temporal variability. Atmos. Environ. 29, 2289–2300. Kulshrestha, U., Monika Jain, T., Prabhat, K., Sarkar, A., 1999. Measurements of atmospheric aerosols at New Delhi during INDOEX Pre-Campaigns. Curr. Sci. 76 (7), 968–972. Kulshrestha, U., Monika, T., Kulshrestha, M., Sekar, R., Vairamani, M., 2003. Chemical Characteristics of rainwater at an urban site of south central India. Atmos. Environ. 37, 3019–3026. Le Bolloch, O., Guerzoni, S., 1995. Acid and alkaline deposition in precipitation on the western coast of Sardinia, central Mediterranean (40 °N, 8 °E). Water air soil pollut. 85, 2155–2160. Lee, B.K., Hong, S.H., Lee, D.S., 2000. Chemical composition and wet deposition of major ions on the Korean peninsula. Atmos. Environ. 34, 563–575. Li, M., Kang, S., Zhang, Q., Kaspari, S., 2007. Major ionic composition of precipitation in the Nam Co region, Central Tibetan Plateau. Atmos. Res. 85, 351–360. Mello, W.Z., 2001. Precipitation chemistry in the coast of the Metropolitan region of Rio de Janeiro. Brazil. Environ. Pollut. 114, 235–242. Migliavacca, D., Teixeira, E.C., Wiegand, F., Machado, A., Sanchez, J., 2005. Atmospheric precipitation and chemical composition of an urban site, Guaiba hydrographic basin, Brazil. Atmos. Environ. 39, 1829–1844. Mouli, P., Mohan, S., Reddy, S., 2005. Rainwater chemistry at a regional representative urban site: influence of terrestrial sources on ionic composition. Atmos. Environ. 39, 999–1008. Moller, A., Muller, H.W., Abdullah, A., Abdelgawad, G., Utermann, J., 2005. Urban soil pollution in Damascus, Syria: concentrations and patterns of heavy metals in the soils of the Damascus Ghouta. Geoderma 124, 63–71. Munger, J., 1982. Chemistry of atmospheric precipitation in north-central United States: influence of sulfate, nitrate, ammonia and calcareous soil particulate. Atmos. Environ. 16, 1633–1645. Nguyen, V.D., Valenta, P., 1987. Electrometric determination of the pH of atmospheric precipitation. Frez. Z. Anal. Chem. 327, 253–260. Safai, P.D., Rao, P.S.P., Momin, G.A., Ali, K., Chate, D.M., Praveen, P.S., 2004. Chemical composition of precipitation during 1984–2002 at Pune, India. Atmos. Environ. 38, 1705–1714. Saxena, A., Kulshrestha, U.C., Kumar, N., Kumari, K.M., Srivastava, S.S., 1996. Characterization of precipitation at Agra. Atmos. Environ. 30 (20), 3405–3412. Schuurkes, J., Maenen, M., Roelofs, J., 1988. Chemical characteristics of precipitation in NH-3 affected areas. Atmos. Environ. 22, 1689–1698. Shehdeh., N., 1991. The Climate of Jordan. Al-basher press, Amman, Jordan. Staelens, J., Schrijver, A.D., Avermaet, P.V., Genouw, G., Verhoest, N., 2005. A comparison of bulk and wet-only deposition at two adjacent sites in Melle. Atmos. Environ. 39, 7–15. Tuncer, B., Bayer, B., Yesilyurt, C., Tuncel, G., 2001. Ionic composition of precipitation at the central Anatolia, Turkey. Atmos. Environ. 35, 5989–6002. Virkutyte, J., Sillanpåå, M., 2006. Chemical evaluation of potable water in Eastern Qinghai Province, China: human health aspects. Environ. Int. 32, 80–86. WAJ Files, 2006. Water Authority of Jordan Files, Amman, Jordan.
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Atmospheric Research j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / a t m o s
Chemical characteristics of rainwater collected at a western site of Jordan Omar Ali. Al-Khashman ⁎ Department of Environmental Engineering, College of Mining and Environmental Engineering, Al-Hussein Bin Talal University, P.O. Box (20) Ma'an, Jordan
a r t i c l e
i n f o
Article history: Received 23 August 2007 Received in revised form 21 May 2008 Accepted 29 May 2008 Keywords: Rainwater chemistry Chemical elements Statistical analysis Acidity Jordan
a b s t r a c t A comprehensive study on the chemical composition of rainwater was carried out from October 2006 to May 2007 in Ghore El-Safi area western side of Jordan nearby the Dead Sea. Rainwater samples were analyzed for major ions (Ca2+, Mg2+, K+, Na+, NH+4, HCO−3, Cl−, NO−3 and SO2− 4 ) and trace metals (Fe, Al, Zn, Pb, Cu, and Cd). The highest concentration of elements is observed at the beginning of the rainfall season when large amounts of dust accumulated in the atmosphere scavenged by rain. The majority of rainwater had a neutral or alkaline character as a result of neutralization caused by the alkaline local dusts which contain large amount of CaCO3. The pH ranged from 4.8 to 8.2 with a mean value of 6.9 ± 0.65 which was in alkaline range considering 5.6 as the neutral pH of cloud water with atmospheric CO2 equilibrium. In the total 35 rain events, only three events were observed in acidic range (b 5.6) which occurred after continuous rains. The equivalent concentration of components followed the order: Ca2+ N HCO−3 N Cl− N Mg2+ N NO−3 N SO2− 4 N NH+4 N Na+ N K+. Rainwater chemistry was analyzed using Factor Component Analysis to find the possible sources of the measured species. Three components that accounted for 84% of the total variance were extracted sea salts spray (Na+, Cl− and Mg2+), and soil particles (natural origin), (Mg2+, Ca2+ and HCO−3) and biomass burning (NH+4). The results obtained in this study are compared with those other studies conducted at different sites in the world. In general, the results of this study suggested that rainwater chemistry is strongly influenced by local anthropogenic sources (potash factory and agricultural activities in Ghore El-Safi area) rather than natural and marine sources. The pollutants in rainwater samples were mainly derived from long distance transport, local industry and traffic sources. © 2008 Elsevier B.V. All rights reserved.
1. Introduction Rainwater chemistry is an intricate result of a complex interaction between cloud dynamics and the microphysical processes as well as series of rainout and washout atmospheric chemical reactions. The acidity and chemical concentration in rain depend on the source strength of the constituents their physical properties into hydrogeological, chemical transformation during cloud formation and below cloud scavenging (Mouli et al., 2005; Kulshrestha et al., 1999). The study of chemical elements in wet and dry precipitation has increased in the last two decades because of their adverse environmental and human health effect (Baez et al., 2007). Rainwater composition plays an important role in scavenging soluble components from the atmosphere and helps us to understand the relative ⁎ Tel./fax: +962 3 2179000. E-mail address: [email protected]. 0169-8095/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.atmosres.2008.05.007
contribution of different sources of atmospheric pollutants (Kulshrestha et al., 2003). The composition of rainwater actually reflects the composition of the atmosphere through which it falls. The study of composition of wet deposition encourages to evaluate the relative importance of the different sources for gases and particularly matter (Demirak et al., 2006).Wet precipitation constituents are the most effective scavenging factor removing particulate and organic and in organic gaseous pollutants from the atmosphere. The scavenging of the atmospheric pollutants affects the chemical composition and the pH of rainwater. The acidic precipitation is primarily caused by incorporation of anthropogenic sources such as SOx, NOx and other acid precursors (Das et al., 2005; Migliavacca et al., 2005). On the other hand, neutralization of acidity in rainwater can be either due to CaCO3 in airborne dust (Munger, 1982; Al-Momani et al., 1995) and or ammonia released from industrial, agricultural and other natural sources (Schuurkes et al., 1988). Chemical composition of rainwater in the Mediterranean region
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and factor affecting these compositions are fairly well established through studies performed since 1980s. There are two main sources that strongly affect the composition of atmospheric particles and precipitation in the Mediterranean basin. The first is the eolian dust transported from North Africa (Kubilay and Saydam, 1995) while the second is the pollution of aerosol transported from Europe (Bergametti et al., 1989; Gullu et al., 1998; Tuncer et al., 2001; Al-Khashman, 2005). Jordan is situated 80 km to the east of the Mediterranean Sea; the climate of Jordan is predominantly of the Mediterranean with hot and dry summers and cold wet winters with two short transitional periods in autumn and spring. During these short transitional periods most convective activity occurs produces producing thunderstorms. Rainfall decreases from north to south and from west to east and from higher to lower elevation (Shehdeh,1991; Al-Khashman, 2005). The aim of the present study is to gain an initial understanding of rainwater chemistry and to identify possible sources of the various constituents of precipitation in the study area. The results obtained in this study are compared with other studies at various places in the world. 2. Materials and methods 2.1. Study area and sample collection Ghore El-Safi area is located in the western part of Jordan nearby the Dead Sea. It is bounded by longitude 35° 28′ N and latitude 31° 2′ E about −350 m above sea level and about 8 km
east from Dead Sea (Fig. 1). It can be classified as mixed between rural/industrial and agricultural surrounding. Ghore El-Safi average rainfall was 77 mm/year and the daily mean humidity was 54.8% with the temperature ranging from the minimum of 10.4 °C to maximum of 22.2 °C. The winter season in Jordan is the principle season of rainfall, the water year starts in early October to May. The prevailing wind direction is from southeast to southwest in winter season, but in the summer season the prevailing wind direction is from northwest, this wind bringing cold wet air during winter and spring from Europe and Mediterranean sea and from the east and south bringing hot dry air during summer and autumn from Saudi Arabia, Africa and India (Shehdeh, 1991). Geologically, the southern part of the investigated area is composed of Precambrian basement complex of metamorphic and a plutonic rock exposed along the eastern rim of Wadi Araba (Bender, 1974). Cambrian overlies the Proterozoic basement to tertiary sediments, but the lower cretaceous sediments are exposed along the eastern side of the Dead Sea– Wadi Araba section of the rift province. Two units are distinguished in the lower cretaceous sequence a lower unit of massive, white sandstones and an upper one of varicolored sandstone. The upper Cretaceous strata were not found in outcrops in the investigated area. Thick bed of conglomerate Neogene related to the tectonic activities unconformable unconformably overlies the basalt and Quaternary sediments beside superficial sediments of Holocene to recent sediments (Bender, 1974).
Fig. 1. Location map of the studied area.
O.A. Al-Khashman / Atmospheric Research 91 (2009) 53–61
The investigated area is surrounded by areas almost exclusively devoted to agriculture and has low residential density. Ghore highway lies about 1.5 km from the sampling site, while the Potash factory lies nearby the investigated area. The rainwater samples were collected on event basis with wet only collectors, for a period of one rainy year (October 2006 to May 2007) in Ghore El-Safi station located almost in the central part of the study area. The station is surrounded uniformly by almost all activities that exist in the investigated area. Samples were collected on the roof of the station building about 8 m from ground level and 1 m from the floor of the roof. Sampling was done manually on an event basis, using only wet collector, which were fitted with a polyethylene bottle and polyethylene funnel 26-cm in diameter (Mouli et al., 2005). Sample collection equipment used on an event basis were was washed with detergent and HNO3 and then rinsed with double deionized water (DDW). The collectors (bottles and funnels) were deployed as soon as the rain began and were retrieved immediately after they were filled up or after the rain stopped. 2.2. Sample analysis A total of 35 samples had sufficient volume for analysis of the studied parameters, which represented about 85% of the total rainfall of the season in the study area. Rain collected by the funnel was gravity filtered through a 0.45 µm pore size membrane filter to remove the insoluble particles, and then collected in the collection bottles. The funnel was stored in a clean plastic bag and was brought out to be mounted on the stand (2.5 m height) just before the rain. Each sample was divided into two bottles; the first part was used to collect + samples for Cl−, NO−3, SO2− 4 , NH4 and pH measurements. The receiving bottle connected to this part was rinsed several times by deionized water and dried before use. The other part was connected to an acid-washed bottle. These bottles were soaked in 20% HNO3 for about one day and rinsed several times with deionized water and dried before use. After that, samples collected in acid-washed bottles were acidified by adding 1 ml (5%) reagent-grade HNO3 to prevent adsorption of the metals by the surface of the polyethylene bottles and to adsorb them out of the dust particles (Al-Khashman., 2005; Al-Momani, 2003; Al-Momani et al., 2000). Rainwater from this sampler was used for the determination of major cations and trace metals. The rainwater samples were collected soon after each rainfall, and kept in a refrigerator at 4 °C until subjected for ion and metal analysis, which was usually performed within two days after collecting samples. The pH values of the collected samples were measured for unacidified samples using 370 JENWAY pH meter equipped with a combination glass electrode. Calibration was always carried out before measurement using standards buffer solutions of pH 4.00 and 7.00. To avoid junction potential errors due to low ionic strength of rain samples, pH measurements were carried out after adjusting samples to 0.02 M with respect to KCL (Nguyen and Valenta,1987). Conductivity measurements were carried out with 470 JENWAY conductivity meter with temperature compensation (Al-Khashman., 2005). The concentration of NH+4 was determined spectrophotometrically using the Nessler method. Major cations (Na+, K+, Ca2+ and Mg2+) were measured by 800 Varian Flame Atomic Absorption Spectrophotometer (Table 1). The concentrations of cations were
55
Table 1 Analytical method used to determine rainwater parameters Lab parameter
Analytical method
pH value Conductivity (µs/cm) Bicarbonate (HCO−3)
370 JENWAY pH meter 470 JENWAY conductivity meter Titration with 0.01 hydrochloric acid using methyl orange 100 Dionex Ion Chromatography instruments 800 Varian Flame Atomic Absorption Spectrophotometer Nessler method Graphite Furnace Atomic Absorption Spectrophotometer
F−, Cl−, NO−3 and SO2− 4 Na+, K+, Ca2+ and Mg2+ NH+4 Trace metals (Fe2+, Al3+, Mn2+, Cu2+, Ni2+, Zn2+ and Pb2+)
determined using a CS12 analytical column, CG 12 guard column, using 20 µm CH4SO−3. The concentration of bicarbonate was determined by titration with 0.01 hydrochloric acid using methyl orange as indicator. Major anions (F−, Cl−, NO−3 and SO2− 4 ) were analyzed by 100 Dionex Ion Chromatography instruments equipped with AG4A-SC guard column, AS4ASC separating column, SSR1 anion self regeneration suppresser and conductivity detector. The samples were injected through 25 MI sample loop and eluted at 2.0 ml min-I using 1.7 µm NaHCO3 and 1.8 µm Na2CO3. The system was calibrated with a certified standard from Dionex. Trace metals (Fe2+, Al3+, Mn2+, Cu2+, Ni2+, Zn2+, and Pb2+) were analyzed with Graphite Furnace Atomic Absorption Spectrophotometer (GF-AAS) using a Varian model GTA 100 instrument. The GF-AAS was calibrated using the method of the standard addition. The standard solution of the anions, cations and trace metals as well as blank samples was prepared with different concentrations. All standard solutions were made daily by diluting the stock solutions with 0.01 M HNO3 (Virkutyte and Sillanpåå, 2006), which was prepared from analytical grade HNO3 solution obtained from Merck. Analysis of field blanks showed that contamination during the sampling procedure transport and analysis was negligible. The sampling water bottles were removed immediately and processed in the same manner as the precipitation samples. Detection limits of the ions, concentrations corresponding to three times the standard deviation of ten replicate blank level measurements were 0.04 µg ml− 1 for Cl−, 0.09 µg ml− 1 for Na+, 0.03 µg ml− 1 for K+, and 0.06 µg ml− 1 for Mg2+, 0.11 µg ml− 1 for Ca2+, 0.04 µg ml− 1 for Cd2+, 0.06 µg ml− 1 for Cu2+, 0.05 µg ml− 1 for Fe2+ and below 0.21 µg ml− 1 for the rest of the trace metals. A quality control procedure, including, recalibration of the instruments, analysis of triplicate samples and recovery test of standard reference material was used to control data quality. All chemicals and reagents used in this study were of analytical grade unless otherwise stated. Deionized water (Milli-Q 8.2 µs/ cm) was used for all dilutions. Standard solutions were prepared by diluting the stock solutions. To prevent the sample contamination with trace metals, all the glassware, Pyrex and plastic containers were washed several times with soap, deionized water and treated with 0.01 M HNO3 and finally rinsed with ultra-pure water. 3. Results and discussion The chemical composition of 35 rainwater samples collected from Ghore El-Safi area from October 2006 to May
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Table 2 The mean concentrations of major ions in rainwater at selected sites worldwide Parameters
This study
Italy a
Galilee b, Israel
Tirupati c, India
Mexico d, USA
Melle e, Belgium
Spain f
Tibetan China g
pH EC Ca2+ Mg2+ Na+ K+ NH+4 HCO−3 Cl− NO−3 SO2− 4
6.91 ± 0.65 95.00 ± 97.11 165.32 ± 0.79 93.12 ± 0.51 130.56 ± 0.31 85.21 ± 0.28 75.36 ± 0.82 133.65 ± 0.18 142.36 ± 0.24 67.31 ± 0.63 112.36 ± 0.58
5.18 – 70.00 77.00 252.00 17.00 25.00 – 322.00 29.00 90.00
– – 44.70 28.00 166.00 3.70 24.30 – 176.30 28.00 150.30
– – 150.66 55.51 33.08 33.89 20.37 – 33.91 40.84 127.96
– – 34.60 3.69 4.52 2.04 95.00 – 9.29 42.86 76.67
5.19 – 26.87 9.25 36.98 1.96 65.65 – 33.37 31.26 47.32
6.40 – 57.50 9.80 22.30 4.00 22.90 – 28.40 20.70 46.1
6.59 19.70 65.58 7.43 15.44 14.49 18.13 72.34 19.17 10.37 15.50
Concentrations were in µeq/l, except EC (µs/cm− 1) n = 35. a Le Bolloch and Guerzoni (1995). b Herut et al. (2000). c Mouli et al. (2005). d Baez et al. (2007). e Staelens et al. (2005). f Avila and Alarcon (1999). g Li et al. (2007).
The analysis consists of chemical composition including ions and trace metals in addition to pH and conductivity. The highest number of events in a month were was seen during February (18.6) followed by January (8.20), and less amount of
rainfall was seen in September, while the monthly average rainfall during the study period is depicted in Fig. 2. The ratio of total cations to that of anions (∑cations/∑anions) is an indicator for the completeness of measured parameters. The average equivalent sum of cations to that of anions ((∑cations/ ∑anions) was 0.86 ± 0.19. The less than unity ratio suggests that a major anion was not measured. The soil in the region is calcareous, indicating that the observed anion deficiency is more likely due to exclusion of bicarbonate from the measurement (Al-Momani et al., 1995; Al-Momani, 2003; AlKhashman, 2005). After computing the concentration of bicarbonate (Granat, 1972), assuming that the concentration of CO2 in the atmosphere is 350 ppm, the average ((∑cations/ ∑anions)) ratio was raised to 0.92 ± 0.22. The average volume weighted concentrations of ions in the investigated area are shown in Table 2 together with those found by others in areas around the world. The concentration of HCO−3 concentration is estimated by ionic balance of the total cations and anions, assuming that the CO2− 3 concentration is negligible. The sulfate concentration (112.36 µeq/l) was found to be very high when compared with those in the literature for similar sampling sites on the world except for the Galilee in Israel (150.30 µeq/l) and in Tirupati in India (127.96 µeq/l). The nitrate value (67.31 µeq/l) was also found to be one of the highest concentrations. The high sulfate
Fig. 2. The monthly rainfall in the study area during the period (1974–2004), (WAJ, 2006).
Fig. 3. Frequency distribution of pH in rainwater samples.
2007 was utilized in this study. The mean ion concentrations for all samples are presented in Table 2. The pH of rainwater samples ranged from 4.81 to 8.24, with an averaged 6.9 ± 0.65 which is in the alkaline range. The pH of rainwater in a clean atmosphere is generally around 5.6 due to the dissolution of CO2 in rain droplets (Boubel et al., 1994; Bayraktar and Turalioglu, 2005). As to pH data, the distribution of pH revealed that the largest fraction 77.2% of all samples had a pH N 5.6, while about 22.8% of rainwater samples had a pH b 5.6. Most pH values ranged between 7.5 and 8.5 (42.8%), while only 22.8% of the rainwater samples had pH values between 5.5 and 4.5. The highest pH (8.2) was observed in the samples collected in the months of April and May and coincided with sulfate, chloride and nitrate concentrations of 3.35 meq/l, 3.71 meq/l and 3.91 meq/l respectively. On the other hand, the lowest pH was associated with the highest value of sulfate (8.69 meq/l) and an average nitrate value of 3.71 meq/l, while the pH increases slightly from winter to summer. 3.1. Major ion concentrations
O.A. Al-Khashman / Atmospheric Research 91 (2009) 53–61
Fig. 4. Contribution of ions to total ion mass.
and nitrate concentrations produce medium pH value in some events. The concentration of Ca2+ is higher than those reported from Italy, Galilee, Triupati, Mexico, Melle and Spain. The higher concentration is due to the large contribution of the Saharan soil dust, which contains large fraction of calcite (Basak and Alagha, 2004; Al-Momani, 2003). The high contribution of Ca2+ and HCO−3 is mainly due to the influence of the continental dust rich in carbonate materials (Li et al., 2007). The concentration of marine elements (Cl−, Na+ and SO2− 4 ) were was much higher in Tirupati in India, Mexico in USA, Melle in Belgium and Spain. NH+4 was much higher in precipitation in USA compared to Jordan. The high values of NH+4 in Ghore area were due to the high level of fertilizer use in agricultural activities, in addition to the contribution of other human activities (Al-Momani et al., 1995; Mouli et al., 2005; Al-Khashman., 2005). 3.2. Chemical composition of rainwater The mean pH value of rainwater has been observed to be 6.9 which is in the alkaline range. The highest acidity was observed on the 8th of December 2006 with a pH of 4.81, while, the lowest was on the 7th of March 2007 with a pH of 8.24. Fig. 3 shows the percent frequency distribution of pH for the rain water samples collected during the rainy season. The observed alkalinity of precipitation is due to high loading of carbonate, bicarbonate of calcium particulate in the atmosphere commonly abundant in the region conditions. The suspended
57
particulate material which is rich in carbonate/bicarbonate of calcium buffers the acidity of wet precipitation (Kulshrestha et al., 2003). The concentration of ions in different rainwater samples is shown in Fig. 4. The chemical composition of major ions in rainwater was listed in Table 2. It clearly shows that the mean concentration of ionic species in rainwater follows the + + + order of: Ca2+ N HCO−3 N Cl− N Mg2+ N NO−3 N SO2− 4 N NH4 N Na N K . Among all the ions, Ca2+ ion makes the highest contribution to the total mass of the ions. It accounts for (17%) followed by HCO−3 (15%), while the Na+ ion makes a relatively moderate contribution compared to Cl− and NH+4 ions. The contributions of Mg2+ and Cl− were 12% and 13% respectively. The sulfate and nitrate ions make a relatively moderate contribution compared to other ions. Bicarbonate ion represents 31% of the total anion mass which was the highest anion contribution, while the highest value of carbonate was measured during warmer dusty storms. The lowest value of bicarbonate was measured during the coldest month of the rainy season, high intensity of precipitation and low dust in the atmosphere (Fig. 5). The contribution of chloride accounts 27% of the total mass of anions in rainwater samples. The highest values of Cl− in rainwater samples were due to the Khamasini wind, in which the region was affected during the spring season and sea salts spray (marine source). However, the Mg2+ ion makes 24% of the total cation mass, which was the highest contribution after Ca2+. The observed Mg2+ values in rainwater samples are generally affected by both sea salt and dust particles in the atmosphere. The contribution of marine sources on observed Mg2+ concentrations is approximately 30%, and the rest being crustal source. The mean concentrations of Na+ and K+ ions account for 16% and 8%, respectively of the cation mass. However, the origin of Na+ and K+ were was mainly derived from the dust sea salts, and the aerosols of the Dead Sea, Mediterranean Sea and polar depressions affected Jordan during the rainy seasons (AlKhashman., 2005). However, NO−3 ion makes a relatively medium contribution compared to Cl− and SO2− 4 . The main sources of NO−3 in the rainwater samples are industries located beside the investigated area such as; potash factory, cement factory and phosphate mines in south Jordan and airborne fertilizer particles. However, motor vehicle emissions make a significant contribution during the dry season when transport
Fig. 5. The monthly mean concentrations of some ions.
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O.A. Al-Khashman / Atmospheric Research 91 (2009) 53–61
and tourist vehicles traffic increases (Al-Momani et al., 1995). The agricultural activities in Ghore area beside the intense thunderstorms caused higher concentrations of nitrate in rainwater samples. The SO2− 4 ion makes 23% of the total mass of anions, which was the highest contribution after bicarbonate and chloride. The high concentration of sulfate in rainwater samples in the study area in air masses originating from sea salt and from soil dust comes from North Africa and deserts around the country which contain a large fraction of calcite, dolomite, gypsum and halite and clay minerals (Foner and Ganor, 1992). On the other hand, the possible source of SO2− 4 in the atmosphere can be derived from SO2 in the air as well as dry deposition of particles over the study area, as a large amount is produced through fuel combustion during the cold winter months (Al-Khashman., 2005). The monthly mean values of 2+ − + SO2− ions in rainy season found in collected 4 , NO3, NH4 and Ca samples were given in Fig. 5. 3.3.
Table 4 Correlation matrix between ions in rainwater samples; cells show the Pearson correlation coefficient and the corresponding P-value Variables Ca Mg2+ +
Na K+
NH+4 HCO−3 Cl− NO−3 SO2− 4
− SO2− 4 /NO3
− The calculated SO2− 4 /NO3 ratio may indicate that the anthropogenic sources in the atmospheric rainfall of industrial areas and the result obtained in the study area were compared to those from other studies (Table 3). They show that this ratio was lower than the ratios found in other studies such as Guaiba, Figueira, Singapore, Galilee, Erzurum, Mexico and Spain. It was, however, higher than the ratio found in Mexico. This might be due to the fact that the locations are − located near or in industrialized urban areas. SO2− 4 and NO3 are ions usually found in rainwater samples and their contribution to the acidity of precipitation is found. The relative contribution by these ions in the acidity of rainwater is variable for event to event. It is estimated that the contribution of H2SO4 in rainwater samples is 60–70 and that of HNO3 is 30–40% (Al-Momani et al., 1995; Tuncer et al., 2001; Migliavacca et al., 2005; Al-Khashman., 2005). Therefore, the contribution of H2SO4 to the acidity of rainwater has decreased compared to HNO3. This is directly related to the control of emitting sources, as well as to the reduction of sulfur contents in oil by-products, in contrast to less stringent controls on NOx emissions, especially in the US and Europe (Byron et al., 1991; Khawaja and Husain, 1990; Al-Momani et al., 1995).
3.4. Statistical analysis 3.4.1. Ionic correlation In order to identify the possible relationship between the various ionic species in rainwater samples, linear regression Table 3 − SO2− 4 /NO3 comparison ratio at various locations in the world Locations
− SO2− 4 /NO3
References
Present study Guaiba Figueira Singapore Galilee Erzurum Mexico Spain
1.20 8.70 5.30 3.50 5.37 11.60 0.75 2.22
Migliavacca et al. (2005) Flues et al. (2002) Balasubramanian et al. (2001) Herut et al. (2000) Bayraktar and Turalioglu (2005) Baez et al. (2007) Avila and Alarcon (1999)
Ca2+
Mg2+
Na+
K+
NH+4
HCO−3
Cl−
NO−3
0.80 0.00 0.50 0.00 0.33 0.00 0.51 0.00 0.76 0.00 0.77 0.00 0.53 0.00 0.75 0.00
0.71 0.00 0.25 0.00 0.76 0.00 0.71 0.00 0.74 0.00 0.33 0.00 0.44 0.00
0.59 0.00 0.70 0.00 0.59 0.00 0.79 0.00 0.30 0.00 0.28 0.00
0.72 0.00 0.61 0.00 0.72 0.00 0.16 0.00 0.02 0.01
0.22 0.00 0.61 0.00 0.63 0.00 0.58 0.00
0.76 0.00 0.29 0.00 0.44 0.00
−0.20 0.01 0.68 0.00
0.85 0.00
2+
analysis was carried out. Table 4 gives the Pearson correlation coefficients computed from 35 samples. Strong correlation 2 − was seen between SO2− 4 and NO3 (R = 0.85) indicating their origin from similar sources. This was due to similarity in their behavior in precipitation and the co-emission of their precursors NOx and SO2. The reason for nitrate and sulfate might be due to accumulation of these ions in the upper atmosphere being washed down with rains during the cold season. Besides, anthropogenic sources and agricultural activities in the study area may contribute more concentrations of these ions during summer and autumn (Al-Khashman, 2005). Ca2+ showed strong correlation with Mg2+ (R2 = 0.80), suggesting the common source of these ions from natural source (crustal origin). This was due to calcareous nature of the soil and the frequent input of Saharan soil dust during the spring season. Other relative good correlations were observed between Ca2+ 2+ and SO2− and Cl− and Mg2+ and Cl−, Mg2+ and NH+4, Mg2+ 4 , Ca − and HCO3 (Table 4). Significantly good correlation was seen between Na+ and Cl− (R2 = 0.79) and also, both showed good correlations with Mg2+ (R2 N 0.70), indicating towards a common sea sea-salt origin (marine source). However, moderate correlation was found between sodium, chloride and sulfate and calcium indicate indicating towards the existence of sea sea-salt particles that are deposited on the local soil (Safai et al., 2004). The ammonium ion was correlated with SO2− 4 (R2 = 0.64), on the other hand, other relatively good correlations noticed between NH+4 and Cl−, and between NH+4 and NO−3 were R2 = 0.61 and 0.58, respectively. The ammonium compounds applied to soil can escape into the atmosphere by means of gaseous NH3 or as NH4NO3 and (NH4)2SO4 particles. When NH4NO3 and (NH4)2SO4 particles were incorporated in precipitation, they change NO−3 and SO2− 4 values, but do not
Table 5 Ratio values of the major ion components of rainwater samples and the corresponding values for sea water
Rainwater Seawater
Cl−/Na+
K+/Na+
Mg2+/Na+
Ca2+/Na+
+ SO2− 4 /Na
1.09 1.80
0.65 0.037
0.71 0.038
1.30 0.12
0.68 0.25
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affect the pH. However, when ammonium was incorporated in the rain, it can neutralize the acidity of rainwater (Al-Momani et al., 1995). However, in order to determine the marine contribution in the composition of rainwater the ratio of sea salts were was calculated considering the sodium as sea sea-salt tracer, assuming that all sodium to be of marine origin. The calculated ratios for rainwater deviated considerably from the seawater ratios (Table 5), indicating a modification of the sea sea-salt constituents along the trajectory of the air masses. The observed Cl−/Na+ ratio (1.09) is much lower to that of seawater ratio (1.8) suggesting either a fractionation of Cl− or enrichment of Na+ (Eriksson, 1959; Mouli et al., 2005). The + elevated K+/Na+, Mg2+/Na+, Ca2+/Na+ and SO2− ratios 4 /Na (Table 4) indicate the possible contribution of other components probably from the soil dust affecting the study area. 3.4.2. Principle component analysis (PCA) Statistical analyses were performed with SPSS for window; 10.0.5 data were log-transformed prior Principle Component Analysis (PCA) to reduce the influence of high data (Moller et al., 2005). PCA was applied to assist in the identification of the source of ions in the rainwater samples by using factor extraction with an Eigenvalue larger than 1 after varimax rotation. The result of statistical analysis was given in Table 6. The loadings having a greater value than 0.70 are marked bold in the table. Factor 1 accounts for 28.5% of total variance and has high 2+ 2+ loading for Cl−, NO−3 and SO2− and Na+ in decreasing 4 , Ca , Mg order; good positive correlations among the ions are found in the correlation matrix analysis. The results of correlation analysis are given in Table 3. For example, the correlation coefficient between Cl− and Ca2+ is 0.77, between Cl− and Mg2+ is 0.74 and between Cl− and SO2− 4 is 0.68. This factor is associated with soil and sea-salt sources. The association sodium and chloride in factor 1 indicates the presence of sea salts arriving in masses of polar sea air (Lee et al., 2000; Mello, 2001). Mg2+ and Ca2+ probably originate from natural sources (soil) and they contribute to neutralization reactions that occur in atmospheric precipitation (Saxena et al., 1996; Migliavacca et al., 2005; Ganor et al., 1991). However, factor 1 shows high loadings for sulfate, chloride and nitrate and this may be related to long-range transport of anthropogenic origin, deriving from human activities from industrial countries (AlKhashman., 2005). The second factor, with 24.3% of the total
59
Table 7 Mean mass contribution from identified sources for rainwater Source
Mean contribution
Percentage of total predicted mass
Soil dust (natural) Anthropogenic Sea spray (marine) Total predicted mass Total estimated mass R (predicted/observed)
442.1 ± 35.2 138.6 ± 13.4 125.7 ± 17.6 706.4 ± 49.1 708.1 ± 34.5 0.99
62.6 19.7 17.7 – – –
(meq/l for the rainwater parameters).
variance, showed Mg2+, Na+, HCO−3 and Ca2+ in decreasing order. This factor is associated with soil source (natural origin). There is a good correlation among the ions, which belong to the second factor, the correlation coefficient between HCO−3 and Ca2+ is 0.76 and between HCO−3 and Mg2+ is 0.71. The high concentration of carbonate materials in rainwater samples is due to large contribution of Saharan soil dust, which contains large fractions of CaCO3, MgCO3 and MgSO4. The third factor, explaining only 15.9% of the total variance, showed the ions K+ and NH+4 with higher values, suggesting biomass burning. The ammonium found atmospheric wet deposition might come from several sources, including the volatilization of animal manure, human excrements, natural loss by plants, fertilizers and agricultural activities (Migliavacca et al., 2005). Based on the statistical analysis, factor 1 represents the contribution of ions from local anthropogenic activities, but the factor 2 represents the contribution of ions from a natural source. On the other hand, factor 3 suggests biomass burning and anthropogenic source. The mean mass contribution from identified sources for rainwater samples is presented in Table 7. In Table 7, the data from the PC analysis with respect to mean mass contribution from identified by PCA sources is presented. It could be seen that for rainwater samples the marine origin delivers the dominant quantity of potassium, sodium and chloride; the anthropogenic source emitters deliver mainly ammonium and nitrate with additional contribution of chlorides and sulfates. Soil dust (Saharan soil dust) contribution is mainly calcium, magnesium and bicarbonate with additional contribution of sulfate and chloride in rainwater samples. 3.5. Trace metals The statistical analysis of metal values in rainwater samples at Ghore El-Safi area during the rainy season were was presented in Table 8. The mean values for Fe, Al, Zn, Pb,
Table 6 Factor analysis of chemical constituents in precipitation Parameters
Factor 1
Factor 2
Factor 3
Communities
pH EC Ca Mg Na K NH4 HCO3 Cl NO3 SO4 Total variance %
−0.84 −0.21 0.51 0.61 0.31 0.17 0.12 0.19 0.85 0.95 0.94 28.5
0.27 0.45 0.45 0.71 0.81 0.31 −0.21 0.82 0.40 0.11 −0.18 24.3
−0.17 −0.31 −0.14 0.33 0.41 0.76 0.66 −0.28 0.12 −0.12 0.18 15.9
0.822 0.876 0.783 0.913 0.931 0.809 0.952 0.740 0.948 0.931 0.947
Table 8 Concentrations of trace metals in rainwater samples (ppb) Element
Mean
Standard deviation
Fe Al Zn Pb Cu Cd Ni Cr
430 324 210 66 73 52 3.5 3.1
75.51 61.74 44.21 33.25 23.10 19.13 2.24 2.01
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atmospheric pollution and the soil dust which affect the composition of wet atmospheric deposition. 4. Conclusion
Fig. 6. The contribution of metals in different rainwater samples.
Cu, and Cd were 56, 40, 18, 22, 20, 12, µg− 1, respectively. The variation of concentration of these metals in rainwater samples can be explained by the scavenging of pollutants (Al-Khashman., 2005). The variation in the values of trace metals between different rainfall events could be related to the source of pollutant emissions. The high concentrations of metals were measured in wet deposition after periods of dryness, while low values of metals were measured when rain continued for several days. The values of each metal in rainwater are shown in Fig. 6. The relative abundance in rainwater (µg− 1) observed were was Fe N Al N Pb N Cu N Zn N Cd depending upon their evaporation rate, relative concentration of metals in rainwater samples and solubility of their metals. The maximum concentration value appeared in the beginning of the rainy season, because of the fact that there is a large amount of pollutants soluble in less solvent (Fig. 7). Metal concentrations in rainwater had a great variability according to the direction of atmospheric depression, metrological conditions and the amount of rainfall. In this study, the highest concentration of metals was shown during the period from January to March (Fig. 7). Moderate correlation between anthropogenic elements Cr and Zn (R2 = 0.61), Cr and Cu (R2 = 0.66) and Zn and Cu (R2 = 0.69). Strong correlation was observed between lead and copper (R2 = 0.81) and lead and zinc (R2 = 0.78) in samples indicating their origin from similar sources. The high values of metals in rainwater samples may be due to long-range atmospheric transport of anthropogenic activities from other parts of Europe and local point sources of
Investigation of chemical composition of rainwater was carried out in the western side of Jordan (Ghore El-Safi area) nearby the Dead Sea during the period (October 2006 to May 2007). This study is essential for establishing a data base about the rainwater quality around one of the most important watersheds in the south region of Jordan. The mean pH of rainwater was 6.91 ± 0.65 well above 4.8, which is the reference pH of rainwater while pH ranged between 4.8 and 8.2. The study revealed that rainwater in the area is alkaline, while the acidity in the rainwater is largely neutralized by Ca2+ and Mg2+ whereas NH+4 played a minor role. The major ions and their concentrations in rainwater followed the order + + + of: Ca2+ N HCO−3 N Cl− N Mg2+ N NO−3 N SO2− 4 N NH4 N Na N K . Sulfate and nitrate were the major acidifying ions in rainwater of the study area. The chemical composition of rainwater in the study area is influenced by either local condition such as; the Dead Sea, agricultural activities in the Ghore area or remote sites associated with depressions rich in calcite, dolomite and gypsum and polar and Mediterranean depressions rich in sulfate and nitrate ions. There was a strong correlation between Ca2+ and Mg2+, Ca2+ and HCO−3, Ca2+ and 4+ Cl−, Ca2+ and SO2− and SO2− 4 and NH 4 . Other moderate correlations were observed between NH+4 and Cl− and between 2+ NH+4 and NO−3 and SO2− makes the 4 . Among the ions, Ca − − highest contribution followed by HCO3, Cl and SO2− 4 indicating the incorporation of soil dust into the rain samples, which reflects a major crustal influence. The relatively moderate concentration of NH+4 observed at the study area is suspected to be due to the surrounding agricultural activity. This agricultural activity has been found to be effective not only in winter and spring, but also in summer, and autumn to cause the neutralization of the rainwater. The use of factor analysis facilitates the interpretation of the rainwater chemistry characterization, highlighting the influence of the anthropogenic sources in the study area. The results of this study are related to various sources, such as soil dust, sea salts, agricultural and biomass burning. The concentration of trace metals (Fe, Al, Zn, Pb, Cu, and Cd) that were determined in the rainwater samples was relatively low. The main source of trace metals in rainwater were was anthropogenic sources.
Fig. 7. The monthly mean concentrations of metals in rainwater samples.
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Acknowledgements The author would like to acknowledge Dr. Abdelaziz L. AlKhlaifat (Director of Prince Faisal Center for Dead Sea, Environmental and Energy Research at Mutah University) for his help and critical reviewing of the text.
References Al-Khashman, O., 2005. Ionic composition of wet precipitation in the Petra region, Jordan. Atmos. Res. 78, 1–12. Al-Momani, I.F., 2003. Trace elements in atmospheric precipitation at northern Jordan measured by ICP-MS: acidity and possible sources. Atmos. Environ. 37, 4507–4515. Al-Momani, I., Tuncel, S., Eler, U., Ortel, E., Sirin, G., Tuncel, G., 1995. Major ion composition of wet and dry deposition in the eastern Mediterranean basin. Sci. Total Environ. 164, 75–85. Al-Momani, I.F., Jaradat, Q.M., Al-Momani, K., 2000. Chemical composition of wet precipitation in Irbid, Jordan. J. Atmos. Chem. 35, 47–57. Avila, A., Alarcon, M., 1999. Relationship between precipitation chemistry and metrological situations at a rural site in NE Spain. Atmos. Environ. 33, 1663–1667. Baez, A.P., Belmont, R.D., Garcia, R.M., Torres, M.C., Padilla, H.G., 2007. Rainwater chemical composition at two sites in Central Mexico. Atmos. Res. 80, 67–85. Balasubramanian, R., Victor, T., Chun, N., 2001. Chemical and statistical analysis of precipitation in Singapore. Water Air Soil Pollut. 130, 451–456. Basak, B., Alagha, O., 2004. The chemical composition of rainwater over Buyukcekmece Lake, Istanbul. Atmos. Res. 71, 275–288. Bayraktar, H., Turalioglu, F.S., 2005. Composition of wet and bulk deposition in Erzurum, Turkey. Chemosphere 59, 1537–1546. Bender, F., 1974. Geology of Jordan, Gerbruder Borntraeger, Berlin. Germany. Bergametti, G., Dutot, A.L., Buart-Menard, P., Losno, R., Remoudaki, E., 1989. Seasonal variability of elemental composition of atmospheric aerosol particles over the north western Mediterranean. Tellus 41B, 353–361. Boubel, R.W., Fox, D.L., Tuner, D.B., Stern, A.C., 1994. Fundamentals of Air Pollution. Academic Press, San Diego, CA. Byron, E.R., Axler, R.P., Goldman, C.R., 1991. Increased precipitation acidity in the central Sierra Nevada. Atmos. Environ. 21, 271–275. Das, R., Das, S., Misra, V., 2005. Chemical composition of rainwater and dust fall at Bhubaneswar in the east coast of India. Atmos. Environ. 39, 5908–5916. Demirak, A., Balci, A., Karaoglu, H., Tosmur, B., 2006. Chemical characteristics of rainwater at urban site of south western Turkey. Environ. Monit. Assess. 123 (1–3), 271–283. Eriksson, E., 1959. The yearly circulation of chloride and sulfur in nature: meteorological, geochemical and pedological implications, part 1. Tellus 11, 375–403. Flues, M., Hamma, P., Lames, M.J.L., Dantas, E.S.K., Fornaro, A., 2002. Evaluation of the rainwater acidity of a rural region due to a coal-fired power plant in Brazil. Atmos. Environ. 36, 2397–2404. Foner, H.A., Ganor, E., 1992. The chemical and mineralogical composition of some urban atmospheric aerosols in Israel. Atmos. Environ. 26, 125–133. Ganor, E., Foner, H.A., Brenner, J., Neeman, E., Lavi, N., 1991. The chemical composition of aerosols setting in Israel following dust storms. Atmos. Environ. 25A, 2665–2670.
61
Gullu, G., Olmez, I., Aygun, S., Tuncel, G., 1998. Atmospheric trace elements concentrations over the eastern Mediterranean Sea: factors affecting temporal variability. J. Geophys. Res. 103, 21943–21954. Herut, B., Starinsky, A., Katz, A., Rosenfeld, D., 2000. Relationship between the acidity and the chemical composition of rainwater and climatological conditions a long a transition zone between large deserts and Mediterranean climate. Israel. Atmos. Environ. 34, 1281–1292. Khawaja, H.A., Husain, L., 1990. Chemical characterization of acid precipitation in Albany, New York. Atmos. Environ. 24A, 1869–1882. Kubilay, N., Saydam, A.C., 1995. Trace elements in the atmospheric particulates over eastern Mediterranean; concentrations, sources and temporal variability. Atmos. Environ. 29, 2289–2300. Kulshrestha, U., Monika Jain, T., Prabhat, K., Sarkar, A., 1999. Measurements of atmospheric aerosols at New Delhi during INDOEX Pre-Campaigns. Curr. Sci. 76 (7), 968–972. Kulshrestha, U., Monika, T., Kulshrestha, M., Sekar, R., Vairamani, M., 2003. Chemical Characteristics of rainwater at an urban site of south central India. Atmos. Environ. 37, 3019–3026. Le Bolloch, O., Guerzoni, S., 1995. Acid and alkaline deposition in precipitation on the western coast of Sardinia, central Mediterranean (40 °N, 8 °E). Water air soil pollut. 85, 2155–2160. Lee, B.K., Hong, S.H., Lee, D.S., 2000. Chemical composition and wet deposition of major ions on the Korean peninsula. Atmos. Environ. 34, 563–575. Li, M., Kang, S., Zhang, Q., Kaspari, S., 2007. Major ionic composition of precipitation in the Nam Co region, Central Tibetan Plateau. Atmos. Res. 85, 351–360. Mello, W.Z., 2001. Precipitation chemistry in the coast of the Metropolitan region of Rio de Janeiro. Brazil. Environ. Pollut. 114, 235–242. Migliavacca, D., Teixeira, E.C., Wiegand, F., Machado, A., Sanchez, J., 2005. Atmospheric precipitation and chemical composition of an urban site, Guaiba hydrographic basin, Brazil. Atmos. Environ. 39, 1829–1844. Mouli, P., Mohan, S., Reddy, S., 2005. Rainwater chemistry at a regional representative urban site: influence of terrestrial sources on ionic composition. Atmos. Environ. 39, 999–1008. Moller, A., Muller, H.W., Abdullah, A., Abdelgawad, G., Utermann, J., 2005. Urban soil pollution in Damascus, Syria: concentrations and patterns of heavy metals in the soils of the Damascus Ghouta. Geoderma 124, 63–71. Munger, J., 1982. Chemistry of atmospheric precipitation in north-central United States: influence of sulfate, nitrate, ammonia and calcareous soil particulate. Atmos. Environ. 16, 1633–1645. Nguyen, V.D., Valenta, P., 1987. Electrometric determination of the pH of atmospheric precipitation. Frez. Z. Anal. Chem. 327, 253–260. Safai, P.D., Rao, P.S.P., Momin, G.A., Ali, K., Chate, D.M., Praveen, P.S., 2004. Chemical composition of precipitation during 1984–2002 at Pune, India. Atmos. Environ. 38, 1705–1714. Saxena, A., Kulshrestha, U.C., Kumar, N., Kumari, K.M., Srivastava, S.S., 1996. Characterization of precipitation at Agra. Atmos. Environ. 30 (20), 3405–3412. Schuurkes, J., Maenen, M., Roelofs, J., 1988. Chemical characteristics of precipitation in NH-3 affected areas. Atmos. Environ. 22, 1689–1698. Shehdeh., N., 1991. The Climate of Jordan. Al-basher press, Amman, Jordan. Staelens, J., Schrijver, A.D., Avermaet, P.V., Genouw, G., Verhoest, N., 2005. A comparison of bulk and wet-only deposition at two adjacent sites in Melle. Atmos. Environ. 39, 7–15. Tuncer, B., Bayer, B., Yesilyurt, C., Tuncel, G., 2001. Ionic composition of precipitation at the central Anatolia, Turkey. Atmos. Environ. 35, 5989–6002. Virkutyte, J., Sillanpåå, M., 2006. Chemical evaluation of potable water in Eastern Qinghai Province, China: human health aspects. Environ. Int. 32, 80–86. WAJ Files, 2006. Water Authority of Jordan Files, Amman, Jordan.