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Distribution, partitioning and sources of polycyclic aromatic hydrocarbons in Daliao River water system in dry season, China
Journal of Hazardous Materials 164 (2009) 1379–1385
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Distribution, partitioning and sources of polycyclic aromatic hydrocarbons in Daliao River water system in dry season, China Wei Guo, Mengchang He ∗ , Zhifeng Yang, Chunye Lin, Xiangchun Quan, Bing Men State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, China
a r t i c l e
i n f o
Article history: Received 18 August 2008 Received in revised form 11 September 2008 Accepted 12 September 2008 Available online 30 September 2008 Keywords: Polycyclic aromatic hydrocarbons Daliao River water system Distribution Partitioning Sources
a b s t r a c t Eighteen polycyclic aromatic hydrocarbons (PAHs) were analyzed in 29 surface water, 29 suspended particulate matter (SPM), 28 sediment, and 10 pore water samples from Daliao River water system in dry season. The total PAH concentration ranged from 570.2 to 2318.6 ng L−1 in surface water, from 151.0 to 28483.8 ng L−1 in SPM, from 102.9 to 3419.2 ng g−1 in sediment and from 6.3 to 46.4 g l−1 in pore water. The concentration of dissolved PAHs was higher than that of particulate PAHs at many sites, but the opposite results were generally observed at the sites of wastewater discharge. The soluble level of PAHs was much higher in the pore water than in the water column. Generally, the water column of the polluted branch streams contained higher content of PAHs than their mainstream. The environmental behaviors and fates of PAHs were examined according to some physicochemical parameters such as pH, organic carbon, SPM content, water content and grain size in sediments. Results showed that organic carbon was the primary factor controlling the distribution of the PAHs in the Daliao River water system. Partitioning of PAHs between sediment solid phase and pore water phase was studied, and the relationship between log Koc and log Kow of PAHs on some sediments and the predicted values was compared. PAHs other than naphthalene and acenaphthylene would be accumulated largely in the sediment of the Dalaio River water system. The sources of PAHs were evaluated employing ratios of specific PAHs compounds and different wastewater discharge sources, indicating that combustion was the main source of PAHs input. © 2008 Elsevier B.V. All rights reserved.
1. Introduction Polycyclic aromatic hydrocarbons (PAHs) are widespread environmental contaminants and have been extensively studied due to their toxicity, carcinogenicity and mutagenicity [1–5]. These compounds in the environment are generally attributed to various emission routes from natural processes and anthropogenic activities [1]. PAHs enter the atmosphere, hydrosphere and pedosphere by combustion of organic matter, dry and wet deposition, wastewater discharge, oil pollution and road runoff [6–8]. Owing to the different physicochemical properties of organic contaminants, PAHs tend to interact to different extent with air, water, SPM, soil/sediment and biota [9–11]. Sediment–pore water interaction is one of the dominant processes controlling the distribution and behavior of PAHs in the rivers [12]. Therefore, the degree of sediment–pore water partitioning of a substance plays a key role in the development of sediment quality criteria [13]. Therefore, a comprehensive study of PAH characters and behavior in aquatic
∗ Corresponding author. Tel.: +86 10 58807172; fax: +86 10 58807172. E-mail address: [email protected] (M. He). 0304-3894/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.jhazmat.2008.09.083
environments including water, SPM, sediments and pore water would be important. Moreover, the compositional properties of PAHs can be used for source diagnosis and pollution control and management in the region. The Liao River watershed is located between N40◦ 31 to N45◦ 17 and E116◦ 54 to E125◦ 32 , on the southwestern part of northeast area of China. The catchment area is about 219,600 km2 . The Liao River watershed includes Liao River water system (Liao River) and Daliao River water system (Hun River, Taizi River and Daliao River). Approximately 2074 million tons of industrial and domestic wastewater is discharged annually into the Liao River catchment. One of the most important heavy industrial complexes including chemical/petrochemical, steel–iron and machine of Northeast Asian is located near Daliao River water system. The Daliao River watershed accepts about 60% pollutant discharge load in the whole Liao River watershed. Petrochemical and steel–iron industries have been identified as the important emission sources of organic pollutants in the area. PAHs are the most ubiquitous hydrophobic organic pollutants, and our previous paper quantitatively provided the levels and spatial variations of these compounds in flood season in Liao River watershed of China [14]. This study provided further discussion about the distribution and sources information of PAHs in dry
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Fig. 1. The study areas and sampling locations in the Daliao River watershed, China.
season from the Daliao River water system based on the much more samples analysis, and the partitioning of PAHs between sediment and pore water was also discussed. 2. Materials and methods
the downstream of Beishahe River and Shahe River, which were contaminated by the wastewater of Dengta city and Anshan city, respectively. Moreover, for Daliao River, the sites range is from D1 to D3, and one site (B9) near the downstream of polluted branch stream named as Wailiao River was sampled. The Wailiao River was mainly contaminated by the wastewater from Taian city.
2.1. Description of sampling area 2.2. Sampling and pretreatment The sampling sites are shown in Fig. 1. Sampling campaign was conducted at 29 sites in dry season. The sites of Hun River range from H01 to H6 along the river, and three contaminated branch stream samples were collected at sites B1, B2 and B3. B1 and B2 are located the downstream of wastwater discharge canal of Fushun oil secondary factory wastewater and Shenyang sewage, respectively. B3 is located downstream of Pu River which was contaminated by the sewage of Liaozhong city. For Taizi River, the site range of mainstream is from T1 to T7 along the river, and four contaminated branch stream samples were collected at sites B4, B5, B6 B7 and B8. An untreated wastewater sample was collected (B4) from the discharge canal of a Benxi steel and iron factory located in front site T3. B5 located downstream of Tang River was contaminated by the wastewater of Gongchangling iron ore and cement industry. B6 is near the downstream of organic wastewater discharge canal of Qingyang Chemical & Engineering. B7 and B8 are near
Twenty-nine water and SPM samples, 28 sediment samples (0–20 cm) and 10 pore water samples were collected from the Hun River, Taizi River and Daliao River in dry season of June 2006. At each site, sediment samples were collected from three to four adjacent points and mixed together. Moreover, some pore water samples about 30 ml per sample were obtained by centrifuging (4000 rpm) the sediments at 4 ◦ C with Frozen centrifuges. According to the Chinese standard to SPM determination (GB11901-89), SPM samples were obtained by filtrating the water using 0.45 m filters (partial four fluorin ethylene, d = 50 mm, Millipore, USA). 2.3. Extraction and analyses of PAHs in samples Filtered water samples (5 l) and pore water samples (30 ml) were extracted using a solid-phase extraction (SPE) system from Supelco,
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Table 1 Physicochemical properties in water and surface sediment of Daliao River water system, China. Sites
H01 H02 B1 H1 H2 H3 H4 B2 H5 H5-1 B3 H6 T1 T2 T3 B4 B5 B6 T4 T5 B7 T6 B8 T7 B9 D1 D2 D2-1 D3
Water
Sediment −1
pH
TOC (mg L
7.28 7.77 7.65 7.2 7.18 7.04 6.9 7.14 7.34 7.22 7.32 7.12 7.61 7.45 6.76 nd 6.02 2.84 7.41 7.36 7.47 7.34 7.69 7.45 6.76 7.1 7.41 7.38 7.36
40.16 56.75 61.61 54.71 35.93 55.73 55.45 76.21 57.12 77.27 81.11 57.63 60.88 30.49 33.54 nd 70.57 74.7 30.42 32.09 43.14 31.83 52.51 29.07 40.33 39.31 33.97 52.5 51.45
)
−1
SPM content (mg L 15.92 8.28 46.23 9.53 81.88 51.97 113.58 39.63 103.35 150.35 48.68 114 19.22 22.43 45.45 nd 83.83 120.05 34.15 7.7 279.96 37.05 182.33 77.36 272.18 59.4 407.88 1001.4 263.51
)
Pore water
pH
TOC (%)
Clay (%)
Silt (%)
Sand (%)
TOC (mg L−1 )
7.55 7.45 7.26 8.88 7.28 7.26 7.18 8.16 6.86 6.98 8.33 5.94 7.94 8.09 7.96 nd 8.55 6.24 8.18 8.25 7.92 8.02 8.33 7.56 7.92 7.45 8.03 8.12 8.39
4.39 1.37 1.49 0.22 1 3.36 0.19 1.37 1 0.75 0.38 0.31 1.04 0.49 5.01 nd 0.63 3.79 0.61 0.49 1.49 0.19 2.56 0.13 1.18 0.93 0.71 0.81 0.26
15.52 9.5 13.57 4.86 3.79 15.52 5.23 15.04 4.45 10.27 0.01 0.03 5.16 3.32 9.77 nd 0 12.85 1.47 8.18 9.29 0.25 19.71 4.79 11.88 13.1 11.72 15.13 10.52
51.69 27.11 31.91 4.17 6.31 42.43 4.64 37.16 11.1 20.94 0.05 0.08 14.67 5.27 35.76 nd 0.24 33.07 2.23 22.52 20.79 1.33 36.91 2.89 25.46 33.07 24 32.74 17.5
32.79 63.39 54.52 90.97 89.9 42.05 90.13 47.8 84.45 68.79 99.94 99.89 80.17 91.41 54.47 nd 99.76 54.08 96.3 69.3 69.92 98.42 43.38 92.32 62.66 53.82 64.28 52.13 71.98
96.25 102.1 nd nd nd 77.6 nd nd nd 82.7 92.65 nd 94.02 nd nd nd nd nd nd 76.21 nd nd nd 94.45 66.7 98.4 nd nd nd
nd: not determined; H: Hun River; T: Taizi River; D: Daliao River; B: branch stream.
and sediments samples (15 g) were Soxhlet extracted with 250 ml of dichloromethane/hexane (1:1, v/v) for 24 h in a water bath maintained at 60 ◦ C. The extract of water, SPM and sediment samples passed to a 1:2 alumina:silica gel glass column with 1 g anhydrous sodium sulfate overlaying the silica gel for clean-up and fractionation. The eluents containing PAHs were collected by eluting 70 ml of hexane/DCM (7:3, v/v), and were concentrated to 0.5 ml under a gentle purified N2 stream. PAHs after adding the known quantities of internal standard (10 l) were analyzed using a GC/MS (ThermoQuest, San Jose, CA, USA) with a 30 m × 0.25 mm i.d. × 0.25 m film thickness DB-5 MS column (J&W Co., USA) in selected ion mode. The extract and analyses methods of water, SPM and sediment samples in details were given in the previous study [14]. 2.4. Analytical quality controls All data were subject to strict quality control procedures. The mean recovery of acenaphthene-d10 for water sample was 79.67%, and that of naphthene-d8 , acenaphthene-d10 , phenanthrene-d10 and chrysene-d12 for sediment samples were 51.79%, 85.66%, 83.83%, 80.33%, respectively. The detection limit of method (MLD) ranged from 18.55 to 79.55 ng L−1 for water samples, and ranged from 0.56 to 3.07 ng g−1 for sediment and SPM samples. Spiked samples in each set of 15–20 samples were analyzed with mean recoveries ranging from 60.79% to 120.71%. Each extract was analyzed in duplicate form and relative standard deviations were less than 20%. 2.5. Other analyses Sub-samples were used to determine physicochemical properties including pH values, total organic carbon (TOC), SPM contents for water, and grain size for sediment [14]. The results are shown in Table 1.
3. Results and discussion 3.1. Distribution of PAHs in water column and sediment The concentrations of PAHs in the water column at different sites are shown in Fig. 2a and b. The water column of the mainstream of the Hun River except at H02 site generally contained about 1000 to 3000 ng L−1 of PAHs, while the water column of the mainstream of the Taizi River and Daliao River generally contained about 1000 ng L−1 of PAHs except at T1 and T3 sites. Whereas SPM content at H02 site was 8.2 mg L−1 , lower than that at other sites (Table 1), the concentration of PAHs in the SPM at H02 site was extremely high, indicating the existence of potential pollution sources. Relatively higher concentration of PAHs in the water column at T1 site might also indicate potential pollution sources. The effluent discharge from Benxi Steel and Iron Factory located in front of T3 site led to higher concentration of PAHs in the SPM at this site. Whereas overall level of PAHs in the water column of the mainstream of the Hun River was higher than that of Taizi River, the level of PAHs in the water column of the branch streams of the Hun River was much lower than that of the Taizi River. In addition, the water column of the branch streams of the Hun River contained low concentration of PAHs than their downstream of the mainstream. This indicated that the branch streams of the Taizi River might be major sources of PAHs to the mainstream, while the branch streams of the Hun River might not be. It is not surprising that extremely high concentration of PAHs was observed in the water column at B4 site because the sample was the wastewater from Benxi Steel & Iron Factory. For Daliao River, the influence of branch stream (B9) to the mainstream was small. The high level of PAHs in the water column at H02, H1, T1, B4, T3, B5, B6, B7 and B8 sites was mainly ascribed to their higher level of PAHs in the SPM with low bioavailability. Owing to the study being carried out in dry season, the chance of dry and wet precipitate for PAHs would be reduced relatively. Thus,
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Fig. 2. Distribution of PAHs in the surface water, SPM, sediments and pore water of Daliao River water system, China.
The discharge of wastewater might be major sources of PAHs in the SPM. The concentration of PAHs in the sediment of the Hun River gradually decreased from ca. 1400 ng g−1 at upstream H01 site to ca. 100 ng g−1 at downstream H6 site (Fig. 2c). However, the concentration of PAHs in the sediment of the mainstream of the Taizi River and Daliao River did not show a regular variation, ranging from ca. 350 ng g−1 to 1000 ng g−1 . The extremely high concentration of PAHs in the sediment at T3 was duo to contamination by the wastewater from Benxi Steel & Iron Factory. In Hun River, the level of PAHs in its branch stream sediment was lower than that in the near mainstream. In Taizi River, the sediments at the sites near industrial cities such as T2, T3, T5, B5, B6, B8 sites had a high level of PAHs. In Daliao River, the contamination of branch stream sediment (B9) was heavy, and the port activities might lead to relatively higher concentration of PAHs in the sediment at D3 site. The concentrations of PAHs in the pore water had no relation to those in the sediment (Fig. 2d), whereas the level of PAHs in the pore water may be influenced by the balance of sorption and partitioning between sediments and pore water [13]. The concentration of PAHs in the pore water was much higher than that in the surface water. 3.2. Factors affecting the content of PAHs PAHs are hydrophobic and prefer to associate with colloids, dissolved organic matter, or SPM in water, and finally deposit in sediment. The characteristic of the water and sediments including pH, TOC, SPM content and clay minerals would influence the behavior and fate of PAHs in the water column and sediments
[11,13,15]. The relation between PAHs and properties of medium was discussed according to Pearson’s coefficient rank correlation. In dry season, resuspension is depressed owing to low velocity and flow quantity of river. The average SPM content was 0.013 g L−1 and lower than that in flood season (0.065 g L−1 ) [14]. The PAHs in water column originated mainly from discharge of wastewater and atmospheric dry fallout. Dissolved organic carbon is one of the most important factors influencing the behavior, fate, and toxicity of dissolved phase PAHs in water column [11,16]. Positive correlation was found between low molecular weight (LMW) (2–3 ring) in water and SPM, high molecular weight (HMW) (4–6 ring) in water and water TOC at 0.05 levels of significance (r < 0.5, P < 0.05, n = 28). No correlation between pH, SPM content and PAHs in water column was observed. Other factors such as various inorganic matrices, hydrodynamic conditions in water body, and so on may influence the PAHs in water, it needs to be studied further. Due to low aqueous solubility and hydrophobic nature, PAHs would finally deposit to underlying sediments. Therefore, the characteristics of sediment influence the transport and fate of PAHs in sediments [11,17]. Under steady state, distribution of PAHs tends to follow equilibrium partitioning of PAHs to organic carbon [18]. In this study, the positive correlation between LMW or HMW PAHs and TOC was observed in sediments (r > 0.5, P < 0.01, n = 28) and pore water (r > 0.7, P < 0.01, n = 10), which indicates that sediment contaminations were primarily controlled by TOC. The relation to LMW (r = 0.869) is better than HMW (r = 0.798) in pore water, and the higher correlation coefficients indicated better linear relationship formed under steady and no disturb state corresponding to surface water. In this study, the mean of TOC in sediments was 1.3 ± 1.3%. When the value of
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Table 2 Comparison of log Koc and log Kow for PAHs at the sediment/pore water interface in the study area. PAHs
log Kow a
log Kow b
Naph Aceph Ace Fl Phen Ant Flu Pyr BaA Chr BbF BkF BaP InP DBA BgP
3.30 4 3.92 4.18 4.56 4.45 4.18 4.88 5.79 5.86 5.8 6 6.04 7.04 6.50 6.5
3.11 3.51 3.43 3.7 4.28 4.27 3.70 4.66 5.30 5.43 5.36 5.57 5.61 6.64 6.22 6.9
log Koc
H01
H02
H3
Hb
P1
T1
T5
T7
W1
D1
3.68 2.22 1.39 2.66 2.31 2.06 2.3 2.76 1.71 1.94 1.65 1.76 1.65 2.69 2.67 3.57
4.24 2.87 3.96 2.92 2.61 2.56 2.37 2.42 2.06 1.48 1.88 2.12 1.6 2.97 1.84 4.53
3.94 2.53 2.02 2.62 2.26 2.81 2.46 2.72 2 2.08 2.09 2.24 2.27 3.11 2.76 3.81
3.65 3.85 2.57 3.46 3.23 3.34 3.44 3.33 3.09 2.9 2.5 2.81 2.66 3.76 3.16 4.41
3.2 3.4 2.78 2.81 2.7 2.99 3.16 3.13 3.2 3.07 3.28 2.94 2.98 4.13 3.89 4.83
3.11 3.52 2.33 3.28 3.24 3.15 2.93 2.89 2.76 2.45 1.98 1.97 1.98 3.72 2.6 4.75
5.23 4.4 2.63 3.29 3.1 3.19 3.21 3.16 2.88 2.63 3.05 2.95 3.12 4.19 3.38 5.17
4.53 4.93 3.18 3.13 2.95 3.01 3.90 3.69 3.45 3.35 3.00 3.04 2.90 4.85 3.34 5.56
5.32 4.45 2.64 3.47 3.3 3.52 4.11 4.14 2.44 2.94 3.09 3.76 3.19 4.18 3.07 5.59
3.37 3.9 2.68 3.12 2.9 2.96 3.29 3.14 2.67 2.77 2.23 2.42 2.17 3.92 2.99 4.6
log Koc (mean)
log Koc (obs − pred)
4.03 3.61 2.62 3.08 2.86 2.96 3.12 3.14 2.63 2.56 2.47 2.6 2.45 3.75 2.97 4.68
0.92 0.1 −0.81 −0.62 −1.42 −1.31 −0.58 −1.52 −2.67 −2.87 −2.89 −2.97 −3.16 −2.89 −3.25 −2.22
obs: observed; pred: predicted. a log Kow values refer to [36,37]. b log Koc values refer to [36], and some PAHs log Koc values calculated referring to [25].
organic carbon is low, the partitioning of PAHs to sediment can be determined by organic carbon and inorganic matrix [18,19]. Unlike other observations [11,20,21], sediments pH has no relation to PAHs. Much more organic matter distributed in small particle sediments including clay and silt (r > 0.05, P < 0.01, n = 28), and a good negative correlation between TOC and sand was observed (r = −0.709, P < 0.01, n = 28). However, only the silt had a positive correlation with LMW PAHs (r = 0.377, P = 0.048, n = 28). These relationships indicate heterogeneous distribution of PAHs and composition in these sediments [13]. According to the above analysis, TOC was the major factor to control the contamination of PAHs, and grain size only had a minor contribution. Similar result was gained in Tianjin’s rivers (China) [11]. 3.3. In situ sediment–pore water partition coefficients Several studies have been conducted by various researchers to understand the equilibrium partitioning and kinetic geochemistry of PAHs between sediment and water [13,22,23], and as a result, distribution coefficient tends to be closely related to the properties of contaminants, in particular their octanol/water partition coefficients (Kow ). This coefficient can be used in predicting the environmental fate of organic chemicals such as PAHs. The higher the log Kow is, the greater the propensity for the chemical to partition to organic phases. The equilibrium partitioning coefficient (Koc ) can be used to describes the relative affinity or attraction of PAHs to sediment and predict the degree of sediment–water partitioning. To evaluate a partitioning behavior and fate of PAHs in the Daliao River water system, in situ sediment–pore water partition coefficient (Koc ) was derived as, K oc = Kp =
Kp foc
,
Cs , Caq
(1) (2)
Cs is the solid-phase concentration, Caq is the aqueous phase concentration, and foc is the sediment fraction of organic carbon [13]. The relationships between log Koc and log Kow were derived by Seth et al. [24] for PAHs on sediments as, logKoc = 1.03 log Kow − 0.61
(3)
This relationship has been recommended for use in critical review papers on Koc estimation [25]. Table 2 showed the values of octanol–water partition coefficient (log Kow ), sediment–pore water equilibrium partitioning coefficient (log Koc ), in situ sediment–pore water distribution coefficient values and the difference of observed and predicted for equilog Koc − log K ) of PAHs in some librium partitioning coefficient (log Koc oc for PAHs was higher sites of studied area. The mean value of log Koc than log Kow and log Koc other than easily volatile Naph and Aceph, and the different tendency was significant for middle and high molecular weight PAHs (Table 2). Some researches have confirmed that particulate associated PAHs were not easily exchangeable with the dissolved phase but were present as either being occluded or tightly bound to fine-grained particles [26]. The result also indicates that only a fraction of total measured site sediment (P1) PAHs concentrations was available to come in equilibrium with the surrounding pore waters [13]. There was no linear relation between and log K log Koc oc or log Kow . The difference of values between in and the corresponding log K indicates more imbalance situ log Koc oc degree between measured sediment and pore water concentrations. Imbalance state between measured sediment and pore water concentrations of PAHs maybe existed in river, a relative unsteady condition compared to sea and bay environment. Certain current erode and a high level of sand content maybe led to difficult accumulation in sediment for PAHs. The result is not in agreement with studies on PAHs from Boston Harbor [27], from San Francisco Bay [13] and from Daya Bay [28] but has similar results to some rivers from Hangzhou of China [29]. 3.4. Source analysis for PAHs In order to assess the possible sources of PAHs, principal component analysis and the ratios of selected PAH compounds in this study were used, for example, Flu/Flu + Pyr and InP/InP + BgP can be applied to help distinguishing the petrogenic and pyrolytic sources [8,30]. The results of principal component analysis and the ratios for Flu/Flu + Pyr and InP/InP + BgP are shown in Figs. 3 and 4, respectively. Principal component analysis of the PAH compound composition produced the first two components (31.6% and 20.3%) that describe above 50% of the variance in samples including water, SPM and sediments data (Fig. 3). The low molecular weight and high
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Fig. 3. Principle component analysis of PAHs composition of water, SPM and sediment from Daliao River water system. (1: Naph, 2: 1-M-Naph, 3: 2-M-Naph, 4: Aceph, 5: Ace, 6: Fl, 7: Phen, 8: Ant, 9: Flu, 10: Pyr, 11: BaA, 12: Chr, 13: BbF, 14: BkF, 15: BaP, 16 DBA, 17: InP, 18: BgP).
molecular weight PAHs were divided in the plot. PC1 represents the contribution of the low molecular weight PAHs and PC2 represents the contribution of the high molecular weight PAHs. Two rings PAHs including Naph, 1-M-Naph and 2-M-Naph and 3 rings PAH including Aceph and Phen attributed to the first principle component with loading above 0.6, and 5 rings and 6 rings PAHs attributed to the second principle component with loading above 0.6. 3 ring PAHs including Fl and Ant and 4 rings PAHs including BaA and Flu were loading of two components above 0.5. It can be concluded that the PAHs pollution is from petrogenic and pyrolytic PAH inputs in this studied region. The same results were also confirmed in earlier investigation for the Daliao River water system [14]. Fl/(Fl + Py) ratio with 0.4 has been considered as the petroleum/combustion transition point, i.e., the ratio less than 0.4 corresponds to petroleum pollutant and higher than 0.5 is characteristic of grass, wood or coal combustion. Furthermore a ratio between 0.4 and 0.5 is more attributed to liquid fossil fuel combustion such as vehicle and crude oil; InP/(InP + BgP) ratio of <0.2 has been used to indicate discharge of petroleum input, and the ratio of >0.5 indicates wood and coal combustion, while a ratio between 0.2
and 0.5 is characteristic of petro-chemical fuel combustion [30,31]. As is shown in Fig. 4, mixed PAH sources were found for water, SPM and sediments. Petro-chemical product and petroleum combustion were probably the dominant source. PAHs enter river environment system mainly via atmospheric fallout, urban runoff, municipal/industrial effluents, and oil leakage [1,32–34]. The source of PAHs is mainly anthropogenically related [35], where PAHs are formed mainly via two mechanisms: fuelcombustion (pyrolytic) and discharge crude oil related material (petrogenic). Pyrogenic PAHs are formed in high temperature combustion processes such as industry emission, and have condensed ring structures (four to six rings); they are usually identified as the majority of PAH input from urban wastewater and industrial emission [8]. For example, the petroleum and chemistry wastewater from Funshun oil secondary factory discharge canal (B1) and sewage from Shenyang industrial and domestic discharge (B2) in Hun River, and steel and iron wastewater from a Benxi steel and cement factory’s discharge canal (B4) and organic wastewater from Qingyang chemical and engineering company (B6) in Taizi River introduced into the river periodically. Moreover, heavy industry development in the area such as Benxi and Anshan metallurgy industry (T1, T2, T3, T7), Shenyang coal, energy and machinery industrial (H2, H3) and the influx from big branch stream contaminated by city sewage such as Pu River (B3) for Hun River, Beisha River (B7) and Shahe River (B8) for Taizi River, and Wailiao River (B9) for Daliao River have a role of the river contamination in a long-term. Petrogenic PAHs originate from unburned products with a smaller number of rings (two to three rings) and are more highly alkylated. For example, the activities of Liaoyang and Fushun oil foundation and Yingkou port shipping led the petrogenic PAHs inputs near the sites such as B4, H1, T4, T5, D2-1 and D3. Although the heavy industry in the area contributed to the development of economy in China in the past, the development of heavy industry around the river until now caused the contamination of river environment by PAHs. 4. Conclusions The occurrence of PAHs in water, SPM and sediments was examined to derive information about the behavior and fate of PAHs in Daliao River water system. The spatial distribution of PAHs was sitespecific, and the concentrations of PAHs were higher in samples collected near industrial areas than those from urban and agriculture sites. Organic carbon was the primary factor controlling the behavior of the PAHs in water and sediments. Disequilibrium partitioning of PAHs between measured sediment and pore water was observed. PAHs were preferably accumulated in sediments. The calculated ratios of selected PAH and PCA analysis suggested that the sources of PAH were mixed from petrogenic and pyrolytic inputs. Petroleum combustion from heavy industrial product process was identified to be a long-term and prevailing contamination source. The short-term contribution to PAHs was obviously derived from different wastewater discharge sources. Acknowledgements The study was supported by the National Basic Research Program of China (Grant no. 2004CB418502) and National Natural Science Foundation of China (no. 20477003). References
Fig. 4. Cross plots of the values of Flu/Flu + Pyr versus InP/InP + BgP for all of the Daliao River water system samples data.
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Distribution, partitioning and sources of polycyclic aromatic hydrocarbons in Daliao River water system in dry season, China Wei Guo, Mengchang He ∗ , Zhifeng Yang, Chunye Lin, Xiangchun Quan, Bing Men State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, China
a r t i c l e
i n f o
Article history: Received 18 August 2008 Received in revised form 11 September 2008 Accepted 12 September 2008 Available online 30 September 2008 Keywords: Polycyclic aromatic hydrocarbons Daliao River water system Distribution Partitioning Sources
a b s t r a c t Eighteen polycyclic aromatic hydrocarbons (PAHs) were analyzed in 29 surface water, 29 suspended particulate matter (SPM), 28 sediment, and 10 pore water samples from Daliao River water system in dry season. The total PAH concentration ranged from 570.2 to 2318.6 ng L−1 in surface water, from 151.0 to 28483.8 ng L−1 in SPM, from 102.9 to 3419.2 ng g−1 in sediment and from 6.3 to 46.4 g l−1 in pore water. The concentration of dissolved PAHs was higher than that of particulate PAHs at many sites, but the opposite results were generally observed at the sites of wastewater discharge. The soluble level of PAHs was much higher in the pore water than in the water column. Generally, the water column of the polluted branch streams contained higher content of PAHs than their mainstream. The environmental behaviors and fates of PAHs were examined according to some physicochemical parameters such as pH, organic carbon, SPM content, water content and grain size in sediments. Results showed that organic carbon was the primary factor controlling the distribution of the PAHs in the Daliao River water system. Partitioning of PAHs between sediment solid phase and pore water phase was studied, and the relationship between log Koc and log Kow of PAHs on some sediments and the predicted values was compared. PAHs other than naphthalene and acenaphthylene would be accumulated largely in the sediment of the Dalaio River water system. The sources of PAHs were evaluated employing ratios of specific PAHs compounds and different wastewater discharge sources, indicating that combustion was the main source of PAHs input. © 2008 Elsevier B.V. All rights reserved.
1. Introduction Polycyclic aromatic hydrocarbons (PAHs) are widespread environmental contaminants and have been extensively studied due to their toxicity, carcinogenicity and mutagenicity [1–5]. These compounds in the environment are generally attributed to various emission routes from natural processes and anthropogenic activities [1]. PAHs enter the atmosphere, hydrosphere and pedosphere by combustion of organic matter, dry and wet deposition, wastewater discharge, oil pollution and road runoff [6–8]. Owing to the different physicochemical properties of organic contaminants, PAHs tend to interact to different extent with air, water, SPM, soil/sediment and biota [9–11]. Sediment–pore water interaction is one of the dominant processes controlling the distribution and behavior of PAHs in the rivers [12]. Therefore, the degree of sediment–pore water partitioning of a substance plays a key role in the development of sediment quality criteria [13]. Therefore, a comprehensive study of PAH characters and behavior in aquatic
∗ Corresponding author. Tel.: +86 10 58807172; fax: +86 10 58807172. E-mail address: [email protected] (M. He). 0304-3894/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.jhazmat.2008.09.083
environments including water, SPM, sediments and pore water would be important. Moreover, the compositional properties of PAHs can be used for source diagnosis and pollution control and management in the region. The Liao River watershed is located between N40◦ 31 to N45◦ 17 and E116◦ 54 to E125◦ 32 , on the southwestern part of northeast area of China. The catchment area is about 219,600 km2 . The Liao River watershed includes Liao River water system (Liao River) and Daliao River water system (Hun River, Taizi River and Daliao River). Approximately 2074 million tons of industrial and domestic wastewater is discharged annually into the Liao River catchment. One of the most important heavy industrial complexes including chemical/petrochemical, steel–iron and machine of Northeast Asian is located near Daliao River water system. The Daliao River watershed accepts about 60% pollutant discharge load in the whole Liao River watershed. Petrochemical and steel–iron industries have been identified as the important emission sources of organic pollutants in the area. PAHs are the most ubiquitous hydrophobic organic pollutants, and our previous paper quantitatively provided the levels and spatial variations of these compounds in flood season in Liao River watershed of China [14]. This study provided further discussion about the distribution and sources information of PAHs in dry
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Fig. 1. The study areas and sampling locations in the Daliao River watershed, China.
season from the Daliao River water system based on the much more samples analysis, and the partitioning of PAHs between sediment and pore water was also discussed. 2. Materials and methods
the downstream of Beishahe River and Shahe River, which were contaminated by the wastewater of Dengta city and Anshan city, respectively. Moreover, for Daliao River, the sites range is from D1 to D3, and one site (B9) near the downstream of polluted branch stream named as Wailiao River was sampled. The Wailiao River was mainly contaminated by the wastewater from Taian city.
2.1. Description of sampling area 2.2. Sampling and pretreatment The sampling sites are shown in Fig. 1. Sampling campaign was conducted at 29 sites in dry season. The sites of Hun River range from H01 to H6 along the river, and three contaminated branch stream samples were collected at sites B1, B2 and B3. B1 and B2 are located the downstream of wastwater discharge canal of Fushun oil secondary factory wastewater and Shenyang sewage, respectively. B3 is located downstream of Pu River which was contaminated by the sewage of Liaozhong city. For Taizi River, the site range of mainstream is from T1 to T7 along the river, and four contaminated branch stream samples were collected at sites B4, B5, B6 B7 and B8. An untreated wastewater sample was collected (B4) from the discharge canal of a Benxi steel and iron factory located in front site T3. B5 located downstream of Tang River was contaminated by the wastewater of Gongchangling iron ore and cement industry. B6 is near the downstream of organic wastewater discharge canal of Qingyang Chemical & Engineering. B7 and B8 are near
Twenty-nine water and SPM samples, 28 sediment samples (0–20 cm) and 10 pore water samples were collected from the Hun River, Taizi River and Daliao River in dry season of June 2006. At each site, sediment samples were collected from three to four adjacent points and mixed together. Moreover, some pore water samples about 30 ml per sample were obtained by centrifuging (4000 rpm) the sediments at 4 ◦ C with Frozen centrifuges. According to the Chinese standard to SPM determination (GB11901-89), SPM samples were obtained by filtrating the water using 0.45 m filters (partial four fluorin ethylene, d = 50 mm, Millipore, USA). 2.3. Extraction and analyses of PAHs in samples Filtered water samples (5 l) and pore water samples (30 ml) were extracted using a solid-phase extraction (SPE) system from Supelco,
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Table 1 Physicochemical properties in water and surface sediment of Daliao River water system, China. Sites
H01 H02 B1 H1 H2 H3 H4 B2 H5 H5-1 B3 H6 T1 T2 T3 B4 B5 B6 T4 T5 B7 T6 B8 T7 B9 D1 D2 D2-1 D3
Water
Sediment −1
pH
TOC (mg L
7.28 7.77 7.65 7.2 7.18 7.04 6.9 7.14 7.34 7.22 7.32 7.12 7.61 7.45 6.76 nd 6.02 2.84 7.41 7.36 7.47 7.34 7.69 7.45 6.76 7.1 7.41 7.38 7.36
40.16 56.75 61.61 54.71 35.93 55.73 55.45 76.21 57.12 77.27 81.11 57.63 60.88 30.49 33.54 nd 70.57 74.7 30.42 32.09 43.14 31.83 52.51 29.07 40.33 39.31 33.97 52.5 51.45
)
−1
SPM content (mg L 15.92 8.28 46.23 9.53 81.88 51.97 113.58 39.63 103.35 150.35 48.68 114 19.22 22.43 45.45 nd 83.83 120.05 34.15 7.7 279.96 37.05 182.33 77.36 272.18 59.4 407.88 1001.4 263.51
)
Pore water
pH
TOC (%)
Clay (%)
Silt (%)
Sand (%)
TOC (mg L−1 )
7.55 7.45 7.26 8.88 7.28 7.26 7.18 8.16 6.86 6.98 8.33 5.94 7.94 8.09 7.96 nd 8.55 6.24 8.18 8.25 7.92 8.02 8.33 7.56 7.92 7.45 8.03 8.12 8.39
4.39 1.37 1.49 0.22 1 3.36 0.19 1.37 1 0.75 0.38 0.31 1.04 0.49 5.01 nd 0.63 3.79 0.61 0.49 1.49 0.19 2.56 0.13 1.18 0.93 0.71 0.81 0.26
15.52 9.5 13.57 4.86 3.79 15.52 5.23 15.04 4.45 10.27 0.01 0.03 5.16 3.32 9.77 nd 0 12.85 1.47 8.18 9.29 0.25 19.71 4.79 11.88 13.1 11.72 15.13 10.52
51.69 27.11 31.91 4.17 6.31 42.43 4.64 37.16 11.1 20.94 0.05 0.08 14.67 5.27 35.76 nd 0.24 33.07 2.23 22.52 20.79 1.33 36.91 2.89 25.46 33.07 24 32.74 17.5
32.79 63.39 54.52 90.97 89.9 42.05 90.13 47.8 84.45 68.79 99.94 99.89 80.17 91.41 54.47 nd 99.76 54.08 96.3 69.3 69.92 98.42 43.38 92.32 62.66 53.82 64.28 52.13 71.98
96.25 102.1 nd nd nd 77.6 nd nd nd 82.7 92.65 nd 94.02 nd nd nd nd nd nd 76.21 nd nd nd 94.45 66.7 98.4 nd nd nd
nd: not determined; H: Hun River; T: Taizi River; D: Daliao River; B: branch stream.
and sediments samples (15 g) were Soxhlet extracted with 250 ml of dichloromethane/hexane (1:1, v/v) for 24 h in a water bath maintained at 60 ◦ C. The extract of water, SPM and sediment samples passed to a 1:2 alumina:silica gel glass column with 1 g anhydrous sodium sulfate overlaying the silica gel for clean-up and fractionation. The eluents containing PAHs were collected by eluting 70 ml of hexane/DCM (7:3, v/v), and were concentrated to 0.5 ml under a gentle purified N2 stream. PAHs after adding the known quantities of internal standard (10 l) were analyzed using a GC/MS (ThermoQuest, San Jose, CA, USA) with a 30 m × 0.25 mm i.d. × 0.25 m film thickness DB-5 MS column (J&W Co., USA) in selected ion mode. The extract and analyses methods of water, SPM and sediment samples in details were given in the previous study [14]. 2.4. Analytical quality controls All data were subject to strict quality control procedures. The mean recovery of acenaphthene-d10 for water sample was 79.67%, and that of naphthene-d8 , acenaphthene-d10 , phenanthrene-d10 and chrysene-d12 for sediment samples were 51.79%, 85.66%, 83.83%, 80.33%, respectively. The detection limit of method (MLD) ranged from 18.55 to 79.55 ng L−1 for water samples, and ranged from 0.56 to 3.07 ng g−1 for sediment and SPM samples. Spiked samples in each set of 15–20 samples were analyzed with mean recoveries ranging from 60.79% to 120.71%. Each extract was analyzed in duplicate form and relative standard deviations were less than 20%. 2.5. Other analyses Sub-samples were used to determine physicochemical properties including pH values, total organic carbon (TOC), SPM contents for water, and grain size for sediment [14]. The results are shown in Table 1.
3. Results and discussion 3.1. Distribution of PAHs in water column and sediment The concentrations of PAHs in the water column at different sites are shown in Fig. 2a and b. The water column of the mainstream of the Hun River except at H02 site generally contained about 1000 to 3000 ng L−1 of PAHs, while the water column of the mainstream of the Taizi River and Daliao River generally contained about 1000 ng L−1 of PAHs except at T1 and T3 sites. Whereas SPM content at H02 site was 8.2 mg L−1 , lower than that at other sites (Table 1), the concentration of PAHs in the SPM at H02 site was extremely high, indicating the existence of potential pollution sources. Relatively higher concentration of PAHs in the water column at T1 site might also indicate potential pollution sources. The effluent discharge from Benxi Steel and Iron Factory located in front of T3 site led to higher concentration of PAHs in the SPM at this site. Whereas overall level of PAHs in the water column of the mainstream of the Hun River was higher than that of Taizi River, the level of PAHs in the water column of the branch streams of the Hun River was much lower than that of the Taizi River. In addition, the water column of the branch streams of the Hun River contained low concentration of PAHs than their downstream of the mainstream. This indicated that the branch streams of the Taizi River might be major sources of PAHs to the mainstream, while the branch streams of the Hun River might not be. It is not surprising that extremely high concentration of PAHs was observed in the water column at B4 site because the sample was the wastewater from Benxi Steel & Iron Factory. For Daliao River, the influence of branch stream (B9) to the mainstream was small. The high level of PAHs in the water column at H02, H1, T1, B4, T3, B5, B6, B7 and B8 sites was mainly ascribed to their higher level of PAHs in the SPM with low bioavailability. Owing to the study being carried out in dry season, the chance of dry and wet precipitate for PAHs would be reduced relatively. Thus,
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Fig. 2. Distribution of PAHs in the surface water, SPM, sediments and pore water of Daliao River water system, China.
The discharge of wastewater might be major sources of PAHs in the SPM. The concentration of PAHs in the sediment of the Hun River gradually decreased from ca. 1400 ng g−1 at upstream H01 site to ca. 100 ng g−1 at downstream H6 site (Fig. 2c). However, the concentration of PAHs in the sediment of the mainstream of the Taizi River and Daliao River did not show a regular variation, ranging from ca. 350 ng g−1 to 1000 ng g−1 . The extremely high concentration of PAHs in the sediment at T3 was duo to contamination by the wastewater from Benxi Steel & Iron Factory. In Hun River, the level of PAHs in its branch stream sediment was lower than that in the near mainstream. In Taizi River, the sediments at the sites near industrial cities such as T2, T3, T5, B5, B6, B8 sites had a high level of PAHs. In Daliao River, the contamination of branch stream sediment (B9) was heavy, and the port activities might lead to relatively higher concentration of PAHs in the sediment at D3 site. The concentrations of PAHs in the pore water had no relation to those in the sediment (Fig. 2d), whereas the level of PAHs in the pore water may be influenced by the balance of sorption and partitioning between sediments and pore water [13]. The concentration of PAHs in the pore water was much higher than that in the surface water. 3.2. Factors affecting the content of PAHs PAHs are hydrophobic and prefer to associate with colloids, dissolved organic matter, or SPM in water, and finally deposit in sediment. The characteristic of the water and sediments including pH, TOC, SPM content and clay minerals would influence the behavior and fate of PAHs in the water column and sediments
[11,13,15]. The relation between PAHs and properties of medium was discussed according to Pearson’s coefficient rank correlation. In dry season, resuspension is depressed owing to low velocity and flow quantity of river. The average SPM content was 0.013 g L−1 and lower than that in flood season (0.065 g L−1 ) [14]. The PAHs in water column originated mainly from discharge of wastewater and atmospheric dry fallout. Dissolved organic carbon is one of the most important factors influencing the behavior, fate, and toxicity of dissolved phase PAHs in water column [11,16]. Positive correlation was found between low molecular weight (LMW) (2–3 ring) in water and SPM, high molecular weight (HMW) (4–6 ring) in water and water TOC at 0.05 levels of significance (r < 0.5, P < 0.05, n = 28). No correlation between pH, SPM content and PAHs in water column was observed. Other factors such as various inorganic matrices, hydrodynamic conditions in water body, and so on may influence the PAHs in water, it needs to be studied further. Due to low aqueous solubility and hydrophobic nature, PAHs would finally deposit to underlying sediments. Therefore, the characteristics of sediment influence the transport and fate of PAHs in sediments [11,17]. Under steady state, distribution of PAHs tends to follow equilibrium partitioning of PAHs to organic carbon [18]. In this study, the positive correlation between LMW or HMW PAHs and TOC was observed in sediments (r > 0.5, P < 0.01, n = 28) and pore water (r > 0.7, P < 0.01, n = 10), which indicates that sediment contaminations were primarily controlled by TOC. The relation to LMW (r = 0.869) is better than HMW (r = 0.798) in pore water, and the higher correlation coefficients indicated better linear relationship formed under steady and no disturb state corresponding to surface water. In this study, the mean of TOC in sediments was 1.3 ± 1.3%. When the value of
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Table 2 Comparison of log Koc and log Kow for PAHs at the sediment/pore water interface in the study area. PAHs
log Kow a
log Kow b
Naph Aceph Ace Fl Phen Ant Flu Pyr BaA Chr BbF BkF BaP InP DBA BgP
3.30 4 3.92 4.18 4.56 4.45 4.18 4.88 5.79 5.86 5.8 6 6.04 7.04 6.50 6.5
3.11 3.51 3.43 3.7 4.28 4.27 3.70 4.66 5.30 5.43 5.36 5.57 5.61 6.64 6.22 6.9
log Koc
H01
H02
H3
Hb
P1
T1
T5
T7
W1
D1
3.68 2.22 1.39 2.66 2.31 2.06 2.3 2.76 1.71 1.94 1.65 1.76 1.65 2.69 2.67 3.57
4.24 2.87 3.96 2.92 2.61 2.56 2.37 2.42 2.06 1.48 1.88 2.12 1.6 2.97 1.84 4.53
3.94 2.53 2.02 2.62 2.26 2.81 2.46 2.72 2 2.08 2.09 2.24 2.27 3.11 2.76 3.81
3.65 3.85 2.57 3.46 3.23 3.34 3.44 3.33 3.09 2.9 2.5 2.81 2.66 3.76 3.16 4.41
3.2 3.4 2.78 2.81 2.7 2.99 3.16 3.13 3.2 3.07 3.28 2.94 2.98 4.13 3.89 4.83
3.11 3.52 2.33 3.28 3.24 3.15 2.93 2.89 2.76 2.45 1.98 1.97 1.98 3.72 2.6 4.75
5.23 4.4 2.63 3.29 3.1 3.19 3.21 3.16 2.88 2.63 3.05 2.95 3.12 4.19 3.38 5.17
4.53 4.93 3.18 3.13 2.95 3.01 3.90 3.69 3.45 3.35 3.00 3.04 2.90 4.85 3.34 5.56
5.32 4.45 2.64 3.47 3.3 3.52 4.11 4.14 2.44 2.94 3.09 3.76 3.19 4.18 3.07 5.59
3.37 3.9 2.68 3.12 2.9 2.96 3.29 3.14 2.67 2.77 2.23 2.42 2.17 3.92 2.99 4.6
log Koc (mean)
log Koc (obs − pred)
4.03 3.61 2.62 3.08 2.86 2.96 3.12 3.14 2.63 2.56 2.47 2.6 2.45 3.75 2.97 4.68
0.92 0.1 −0.81 −0.62 −1.42 −1.31 −0.58 −1.52 −2.67 −2.87 −2.89 −2.97 −3.16 −2.89 −3.25 −2.22
obs: observed; pred: predicted. a log Kow values refer to [36,37]. b log Koc values refer to [36], and some PAHs log Koc values calculated referring to [25].
organic carbon is low, the partitioning of PAHs to sediment can be determined by organic carbon and inorganic matrix [18,19]. Unlike other observations [11,20,21], sediments pH has no relation to PAHs. Much more organic matter distributed in small particle sediments including clay and silt (r > 0.05, P < 0.01, n = 28), and a good negative correlation between TOC and sand was observed (r = −0.709, P < 0.01, n = 28). However, only the silt had a positive correlation with LMW PAHs (r = 0.377, P = 0.048, n = 28). These relationships indicate heterogeneous distribution of PAHs and composition in these sediments [13]. According to the above analysis, TOC was the major factor to control the contamination of PAHs, and grain size only had a minor contribution. Similar result was gained in Tianjin’s rivers (China) [11]. 3.3. In situ sediment–pore water partition coefficients Several studies have been conducted by various researchers to understand the equilibrium partitioning and kinetic geochemistry of PAHs between sediment and water [13,22,23], and as a result, distribution coefficient tends to be closely related to the properties of contaminants, in particular their octanol/water partition coefficients (Kow ). This coefficient can be used in predicting the environmental fate of organic chemicals such as PAHs. The higher the log Kow is, the greater the propensity for the chemical to partition to organic phases. The equilibrium partitioning coefficient (Koc ) can be used to describes the relative affinity or attraction of PAHs to sediment and predict the degree of sediment–water partitioning. To evaluate a partitioning behavior and fate of PAHs in the Daliao River water system, in situ sediment–pore water partition coefficient (Koc ) was derived as, K oc = Kp =
Kp foc
,
Cs , Caq
(1) (2)
Cs is the solid-phase concentration, Caq is the aqueous phase concentration, and foc is the sediment fraction of organic carbon [13]. The relationships between log Koc and log Kow were derived by Seth et al. [24] for PAHs on sediments as, logKoc = 1.03 log Kow − 0.61
(3)
This relationship has been recommended for use in critical review papers on Koc estimation [25]. Table 2 showed the values of octanol–water partition coefficient (log Kow ), sediment–pore water equilibrium partitioning coefficient (log Koc ), in situ sediment–pore water distribution coefficient values and the difference of observed and predicted for equilog Koc − log K ) of PAHs in some librium partitioning coefficient (log Koc oc for PAHs was higher sites of studied area. The mean value of log Koc than log Kow and log Koc other than easily volatile Naph and Aceph, and the different tendency was significant for middle and high molecular weight PAHs (Table 2). Some researches have confirmed that particulate associated PAHs were not easily exchangeable with the dissolved phase but were present as either being occluded or tightly bound to fine-grained particles [26]. The result also indicates that only a fraction of total measured site sediment (P1) PAHs concentrations was available to come in equilibrium with the surrounding pore waters [13]. There was no linear relation between and log K log Koc oc or log Kow . The difference of values between in and the corresponding log K indicates more imbalance situ log Koc oc degree between measured sediment and pore water concentrations. Imbalance state between measured sediment and pore water concentrations of PAHs maybe existed in river, a relative unsteady condition compared to sea and bay environment. Certain current erode and a high level of sand content maybe led to difficult accumulation in sediment for PAHs. The result is not in agreement with studies on PAHs from Boston Harbor [27], from San Francisco Bay [13] and from Daya Bay [28] but has similar results to some rivers from Hangzhou of China [29]. 3.4. Source analysis for PAHs In order to assess the possible sources of PAHs, principal component analysis and the ratios of selected PAH compounds in this study were used, for example, Flu/Flu + Pyr and InP/InP + BgP can be applied to help distinguishing the petrogenic and pyrolytic sources [8,30]. The results of principal component analysis and the ratios for Flu/Flu + Pyr and InP/InP + BgP are shown in Figs. 3 and 4, respectively. Principal component analysis of the PAH compound composition produced the first two components (31.6% and 20.3%) that describe above 50% of the variance in samples including water, SPM and sediments data (Fig. 3). The low molecular weight and high
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Fig. 3. Principle component analysis of PAHs composition of water, SPM and sediment from Daliao River water system. (1: Naph, 2: 1-M-Naph, 3: 2-M-Naph, 4: Aceph, 5: Ace, 6: Fl, 7: Phen, 8: Ant, 9: Flu, 10: Pyr, 11: BaA, 12: Chr, 13: BbF, 14: BkF, 15: BaP, 16 DBA, 17: InP, 18: BgP).
molecular weight PAHs were divided in the plot. PC1 represents the contribution of the low molecular weight PAHs and PC2 represents the contribution of the high molecular weight PAHs. Two rings PAHs including Naph, 1-M-Naph and 2-M-Naph and 3 rings PAH including Aceph and Phen attributed to the first principle component with loading above 0.6, and 5 rings and 6 rings PAHs attributed to the second principle component with loading above 0.6. 3 ring PAHs including Fl and Ant and 4 rings PAHs including BaA and Flu were loading of two components above 0.5. It can be concluded that the PAHs pollution is from petrogenic and pyrolytic PAH inputs in this studied region. The same results were also confirmed in earlier investigation for the Daliao River water system [14]. Fl/(Fl + Py) ratio with 0.4 has been considered as the petroleum/combustion transition point, i.e., the ratio less than 0.4 corresponds to petroleum pollutant and higher than 0.5 is characteristic of grass, wood or coal combustion. Furthermore a ratio between 0.4 and 0.5 is more attributed to liquid fossil fuel combustion such as vehicle and crude oil; InP/(InP + BgP) ratio of <0.2 has been used to indicate discharge of petroleum input, and the ratio of >0.5 indicates wood and coal combustion, while a ratio between 0.2
and 0.5 is characteristic of petro-chemical fuel combustion [30,31]. As is shown in Fig. 4, mixed PAH sources were found for water, SPM and sediments. Petro-chemical product and petroleum combustion were probably the dominant source. PAHs enter river environment system mainly via atmospheric fallout, urban runoff, municipal/industrial effluents, and oil leakage [1,32–34]. The source of PAHs is mainly anthropogenically related [35], where PAHs are formed mainly via two mechanisms: fuelcombustion (pyrolytic) and discharge crude oil related material (petrogenic). Pyrogenic PAHs are formed in high temperature combustion processes such as industry emission, and have condensed ring structures (four to six rings); they are usually identified as the majority of PAH input from urban wastewater and industrial emission [8]. For example, the petroleum and chemistry wastewater from Funshun oil secondary factory discharge canal (B1) and sewage from Shenyang industrial and domestic discharge (B2) in Hun River, and steel and iron wastewater from a Benxi steel and cement factory’s discharge canal (B4) and organic wastewater from Qingyang chemical and engineering company (B6) in Taizi River introduced into the river periodically. Moreover, heavy industry development in the area such as Benxi and Anshan metallurgy industry (T1, T2, T3, T7), Shenyang coal, energy and machinery industrial (H2, H3) and the influx from big branch stream contaminated by city sewage such as Pu River (B3) for Hun River, Beisha River (B7) and Shahe River (B8) for Taizi River, and Wailiao River (B9) for Daliao River have a role of the river contamination in a long-term. Petrogenic PAHs originate from unburned products with a smaller number of rings (two to three rings) and are more highly alkylated. For example, the activities of Liaoyang and Fushun oil foundation and Yingkou port shipping led the petrogenic PAHs inputs near the sites such as B4, H1, T4, T5, D2-1 and D3. Although the heavy industry in the area contributed to the development of economy in China in the past, the development of heavy industry around the river until now caused the contamination of river environment by PAHs. 4. Conclusions The occurrence of PAHs in water, SPM and sediments was examined to derive information about the behavior and fate of PAHs in Daliao River water system. The spatial distribution of PAHs was sitespecific, and the concentrations of PAHs were higher in samples collected near industrial areas than those from urban and agriculture sites. Organic carbon was the primary factor controlling the behavior of the PAHs in water and sediments. Disequilibrium partitioning of PAHs between measured sediment and pore water was observed. PAHs were preferably accumulated in sediments. The calculated ratios of selected PAH and PCA analysis suggested that the sources of PAH were mixed from petrogenic and pyrolytic inputs. Petroleum combustion from heavy industrial product process was identified to be a long-term and prevailing contamination source. The short-term contribution to PAHs was obviously derived from different wastewater discharge sources. Acknowledgements The study was supported by the National Basic Research Program of China (Grant no. 2004CB418502) and National Natural Science Foundation of China (no. 20477003). References
Fig. 4. Cross plots of the values of Flu/Flu + Pyr versus InP/InP + BgP for all of the Daliao River water system samples data.
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