- Email: [email protected]
Seasonal transport pattern of chromium(III and VI) in a stream receiving wastewater from tanneries
Applied Geochemistry 25 (2010) 116–122
Contents lists available at ScienceDirect
Applied Geochemistry journal homepage: www.elsevier.com/locate/apgeochem
Seasonal transport pattern of chromium(III and VI) in a stream receiving wastewater from tanneries Ewa Szalinska a,*, Janusz Dominik b, Davide A.L. Vignati b,c, Andrzej Bobrowski d, Boguslaw Bas d a
Institute of Water Supply and Environmental Protection, Cracow University of Technology, ul. Warszawska 24, 31-155 Krakow, Poland Institut F.-A. Forel, University of Geneva, route de Suisse 10, CH-1290 Versoix, Switzerland c CNR-IRSA, Via della Mornera 25, 20047 Brugherio, Italy d Faculty of Materials Science and Ceramics, University of Science and Technology, al. Mickiewicza 30, 30-059 Krakow, Poland b
a r t i c l e
i n f o
Article history: Received 8 July 2009 Accepted 2 November 2009 Available online 6 November 2009 Editorial handling by Dr. R. Fuge
a b s t r a c t Water, suspended matter and sediment samples from a system heavily impacted by wastewater from numerous small tanneries (the upper Dunajec River, southern Poland) were collected to establish the annual cycle of Cr. To study possible oxidation processes the speciation of Cr and Mn concentrations were also investigated. This study showed that Cr(III and VI) temporal and spatial distributions are regulated by coupled anthropogenic (source location and emissions) and hydrologic factors (water flow and particle transport). Chromium(III) concentrations in all compartments varied seasonally as a function of the hydrological regime, production cycle in tanneries and distance from the discharge location. Cr(III) was largely associated with the particulate phase and rapidly deposited in river bed sediments. Contaminated river sediments were however flushed during flood periods to the reservoir located downstream from tanneries. During the tanning season (November to March), Chromium(III) concentrations in the water column and total Cr concentration in sediments exceeded relevant ecotoxicological guidelines only upstream from the reservoir, which trapped about 70% of the annual Cr(III) load transported by the Dunajec river. A correlation between Cr(VI)/Cr(III) ratios and Mn concentration in sediments downstream from the reservoir suggests the possibility of Cr(III) oxidation in natural conditions. Ó 2009 Elsevier Ltd. All rights reserved.
1. Introduction Tanneries are important sources of Cr contamination in surface waters throughout the world, especially in regions where sheep breeding and tannery crafts still remain important for economical reasons (Joradao et al., 1997; Khamar et al., 2000; Armienta et al., 2001; Koukal et al., 2004; Rodrigues and Formoso, 2006). The geographical extension of Cr pollution released from tanneries is related to the extent of discharges and hydrological processes. Equally important are Cr speciation in the discharge, and the possibility of its transformation. The environmental fate and ecotoxicologic risk related to Cr emissions from these sources are poorly known because of the complex chemistry of this element in surface water. Concentrations and proportions of trivalent and hexavalent Cr in the aquatic environment, can vary with local conditions. Generally, Cr(VI) is considered more toxic than Cr(III) (e.g. Pawlisz et al., 1997), but a few studies have reported contrasting findings (Thompson et al., 2002; Pereira et al., 2005) suggesting that both forms can adversely affect biota. The identification and quantification of Cr species therefore becomes important from the ecotoxicological point of view. Furthermore, Cr(III) compounds can be * Corresponding author. Tel.: +48 12 628 2870; fax: +48 12 628 2042. E-mail address: [email protected] (E. Szalinska). 0883-2927/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.apgeochem.2009.11.002
rapidly removed from the water column via adsorption–coagulation–sedimentation processes and can accumulate in sediments (Cranston and Murray, 1980; Dominik et al., 2007). High concentrations of Cr in sediments in the vicinity of discharges may affect benthic biota as well. On the other hand, oxidation of Cr(III) to Cr(VI) in the presence of Mn oxides (e.g. Kim et al., 2002; Stepniewska et al., 2004) may result in Cr remobilization from contaminated sediments. A major challenge in assessing Cr fate, transport, and potential risk for aquatic biota in a watershed is usually the scale of the system, and a lack of datasets integrating water, suspended matter and sediments. Furthermore, a number of confounding factors, such as multiple polluting sources and a presence of various contaminants, increases the level of difficulty in evaluating the potential ecotoxicological risk. The upper Dunajec River (West Carpathians Mountains, southern Poland) is a small system particularly suitable for studying the environmental fate and transport of Cr contamination and to assess the relative importance of processes regulating spatial and temporal distribution. The existence of an impoundment reservoir, constructed to protect the area against flood events, plays a role in Cr transport within this system. This is a region with modest industrialization and urbanization, where agriculture and animal breeding provide most of the
E. Szalinska et al. / Applied Geochemistry 25 (2010) 116–122
employment, and where traditional tannery crafts are still practiced. The latter activity is the actual source of Cr contamination since Cr is used as a tanning agent. The tanned leather is produced mostly in small tanneries (300), located in a well constrained section of the watershed. Due to improper tannery wastewater management, pre-treated or raw wastewaters from these tanneries are discharged into local sewers or directly into the Dunajec River and its tributaries (Szalinska, 2001). Other metals are not appreciably enriched above background levels in this watershed, while contamination with organic micropollutants occurs only following accidental spills (Szalinska et al., 2003). The mean monthly flows (1951–1980) of the Dunajec River vary from 6 m3 s 1 in winter months to 20 m3 s 1 during snow thawing (April) and heavy rainfall (June–July) periods. Since, this mean maximum flow can be exceeded by several hundred times between June and July (up to 800 m3 s 1; Fal et al., 2000), an impoundment reservoir was constructed (1997) on the Dunajec River to protect the area against recurrent flood events. Taking advantage of this ideal setting a full year survey of Cr in water, suspended particulate matter and sediments was performed in this study to determine the environmental fate of Cr in a tannery-impacted ecosystem. Design of the sampling strategy also permitted the assessment of the role of the reservoir as a sink for Cr and in limiting Cr transport downstream. Potential threats to the ecosystem such as the impact on biota and the possibility of Cr oxidation in the presence of Mn were also assessed. To verify the findings of this study the results from other investigations in the upper Dunajec River region (2005 and 2006) performed by the authors are included in Section 4.
2. Materials and methods 2.1. Sampling area and sample collection Water and sediment samples were collected from the Dunajec River, November 2000 through December 2001, approximately once a month. However, due to the unfavorable weather conditions
117
only nine water, and seven sediment samples could be obtained. Additional samples were taken from Bialka River in the same period. The sampling localities are shown in Fig. 1. The Dunajec River samples were taken from sites upstream (1 and 2) and downstream (3) from the Czorsztyn Reservoir. Sampling site 1 was located in the vicinity of the main Cr inputs. The Bialka River sampling site (4) was considered to be a non-contaminated reference point. Surface water samples were collected using hand held, HNO3washed, polyethylene bottles. Water samples were filtered (0.45 lm, cellulose acetate) within 2 h of collection and filters were dried and weighed. Filtrates for total dissolved Cr determination were acidified with HNO3 (ACS grade) to a pH below 2. Nonacidified filtrates for Cr(VI) determination were kept below 4 °C until delivered to the laboratory and measured (within 8 h). Sediment samples from the Dunajec River were gently collected from the uppermost oxic layer using a plastic shovel and stored in plastic containers. All sediment samples were sieved using a 2 mm plastic sieve in order to remove major detritus, and air-dried.
2.2. Laboratory analyses Filtrates were analyzed for total dissolved Cr and for Cr(VI) by catalytic adsorptive stripping voltammetry (CAdSV) according to the method described by Bobrowski et al. (2004), while Cr(III) was calculated from the difference. The detection limit for total Cr and Cr(VI) was 0.005 lg L 1. Mean values for blanks were below reported detection limits. All measurements were performed three times and reported as mean values. Replicate measurements agreed within <5%. For selected samples, measurements of total Cr by the CAdSV technique were in very good agreement with ICP-MS and GFAAS determinations (r > 0.99, n = 6; Szalinska, 2002). The suspended matter extraction was performed according to the Osol protocol (Osol, 1986) in an ultrasonic mineralizator (ULTRAsonic 104X) for 10 min with 10 mL 2N HNO3. Samples were then heated at 100 °C for 12 h and allowed to cool. After centrifu-
Fig. 1. Overview of the sampling area and positions of the sampling sites.
E. Szalinska et al. / Applied Geochemistry 25 (2010) 116–122
gation (4000 rpm for 20 min), supernatants were diluted by a ratio of 200 with 1% HNO3 before measurement. Chromium measurements were performed by ICP-MS (HP-4500 Agilent) and the detection limit was 0.01 lg L 1. Previous tests have shown that the Osol procedure extracted 80–100% of the total recoverable Cr from the contaminated sediment samples (r > 0.99, n = 9; Szalinska, 2002). Due to the small amount of suspended matter retained on filters, only some of them were subjected to extraction. Total digestion of sediment samples, following dry mineralization at 450 °C for 6 h, was performed in Kjeldahl flasks with 10 mL HNO3 and 5 mL HClO4 (ACS grade) for 12 h according to the protocol described by Ostrowska et al. (1991). Samples were then heated to 250 °C and cooled. After adding 10 mL HCl (1 + 1) samples were heated at 100 °C for 2 h and cooled again. After filtration, the supernatant was transferred to LDPE bottles and brought up to 50 mL with MQ water. Chromium and Mn concentrations in sediments were measured by flame AAS (UNICAM 939 AA Spectrometer) and the reported detection limit was 0.02 mg L 1 for both metals.
3. Results 3.1. Chromium in water In all investigated Dunajec River sites, concentrations of dissolved Cr(VI) did not exceed 4 lg L 1 (Fig. 2a). Concentrations were relatively high in November and December and decreased in other months. Minimum values (below 0.3 lg L 1) were detected in 25
4
20
3
15
2
10
]
5
1
1
5
0
0 Dec 00
Jan 01
Mar 01
Apr 01
Sampling site 1
May 01
Jul 01
Sampling site 2
Oct 01
Nov 01
Dec 01
Sampling site 3
80
20
60
15
40
10
1
]
25
chromium(III) [µg L-1]
(b) 100
flow [m3 s-1]
chromium(VI) [µg L-1]
(a)
During Cr and Mn analyses, calibration solutions, blanks, and standards were re-run every 10 samples. Precision was monitored by running duplicates of any two real samples placed in random order within every 10 samples. To assess contamination, three method blanks were randomly processed through the procedure. Mean values for blanks were below reported detection limits. Accuracy was assured through the use of a certified reference sediment material STSD-1 and STSD-2. Percentage recovery of Cr and Mn with respect to certified values was in the 90–110% range.
flow [m3 s-1]
118
20
5
0
0 Dec 00
Jan 01
Mar 01
Apr 01
Sampling site 1
May 01
Jul 01
Sampling site 2
Oct 01
Nov 01
Dec 01
Sampling site 3
Fig. 2. Concentrations of dissolved Cr(VI) (a) and Cr(III) (b) in Dunajec River water during the sampling period. Bars represent the Dunajec River mean monthly flows for the gauge cross-section (see Fig. 1). Note the different vertical scales for parts (a) and (b).
119
E. Szalinska et al. / Applied Geochemistry 25 (2010) 116–122 Table 1 Mean (±std) chromium and manganese concentrations in water (lg L Bialka River (4). Site
1
), suspended matter (lg L
Water
1 2 3 4
) and sediments (mg g
1
sm) from the Dunajec River sites (1–3), and from the
Suspended matter
Sediments
Cr(VI)
Cr(III)
Cr
Mn
Cr
Mn
1.1 ± 1.2 1.4 ± 1.1 0.3 ± 0.2 0.1 ± 0.1
23.4 ± 27.5 11.7 ± 12.5 0.6 ± 0.5 0.2 ± 0.2
12.8 ± 13.1 4.0 ± 2.5 2.0 ± 1.8 0.3 ± 0.5
14.6 ± 23.4 23.2 ± 31.5 29.5 ± 24.2 2.4 ± 3.6
0.72 ± 0.36 0.43 ± 0.30 0.06 ± 0.04 0.03 ± 0.02
1.05 ± 0.72 0.53 ± 0.12 2.61 ± 1.06 0.16 ± 0.09
months with high flows, above 20 m3 s 1 (April and July). For both sites upstream from the reservoir, mean concentrations were comparable (Table 1), but for the same date higher values were observed at site 2 (except for November 2001). Downstream from the reservoir (site 4), the Cr(VI) mean concentration was lower, but still three times higher than the concentration for the reference site 4. Maximum concentrations of dissolved Cr(III), exceeding 50 lg L 1, were detected at site 1 in December 2000 and November
(a)
1
2001 (Fig. 2b). For site 2, Cr(III) peak concentrations were detected during the same months, but were about 40 lg L 1 lower than at site 1. As a rule, concentrations of Cr(III) were higher at site 1 than at 2 during the whole sampling period, however the mean concentrations (Table 1) for these sites were not significantly different. The temporal distribution of Cr(III) in sites 1 and 2 showed a distinct increase in late fall/winter months (November and December), and decreased in April and July. Downstream from the
40
25
chromium [µg L-1]
15 20 10
suspended solids [mg L-1]
20 30
10 5
0
0 Apr 01
Jul 01
Sampling site 1
Oct 01
Nov 01
Sampling site 2
Dec 01
Sampling site 3 25
1.0
20
0.8
15
0.5
10
0.3
5
chromium [mg g-1 dry weight]
(b) 1.3
0.0
Flow [m3 s-1]
Mar 01
0 Nov 00
Dec 00
Sampling site 1
Jan 01
Mar 01
Sampling site 2
May 01
Oct 01
Nov 01
Sampling site 3
Fig. 3. Concentrations of Cr in Dunajec River suspended matter (a) and sediments (b) during the sampling period. Bars represent distribution of the Dunajec River mean monthly suspended solids concentrations for the gauge cross-section.
120
E. Szalinska et al. / Applied Geochemistry 25 (2010) 116–122
reservoir (site 3), the mean Cr(III) concentration was one order of magnitude lower than at sites 1 and 2, while values for the reference site (4) were in the range of 0.03–0.4 lg L 1. The two redox forms of Cr were significantly correlated (p < 0.05, Spearman test) for upstream sites (n = 10, r = 0.96 and r = 0.80 for sites 1 and 2, respectively) but not correlated for site 3. 3.2. Chromium in suspended matter The suspended matter concentrations followed the distribution of flows in the Dunajec River. The concentration increased in the snow thawing period (March and April) up to 15 mg L 1 (Fig. 3a) and reached maximum values (up to 23 mg L 1) in July, when heavy rainfall occurred. Chromium concentrations measured in the suspended matter are reported below in lg L 1, instead of the usual lg g 1, to elucidate the fate of the total Cr (dissolved and particulate), also given in lg L 1, in the further discussion. In all investigated samples, Cr concentrations in the particulate phase were higher at site 1 than in the rest of the investigated sites, with the highest detected value being 37.9 lg L 1. The temporal distribution of Cr concentrations in suspended matter for both upstream sites (1 and 2) showed a similar pattern, with a noticeable decrease in July 2001, when the observed concentration of suspended solids was highest (Fig. 3a). The mean concentration in the site downstream from the reservoir (3) was lowest (Table 1) but not significantly different from the upstream site concentrations. Also a t-test showed that there was no significant difference between concentrations on particular sampling days. In samples from the reference site (4) concentrations of particulate Cr were close to the detection limit (0.15–0.30 lg L 1) due to low suspended solid concentrations, below 4 mg L 1, and low Cr content. 3.3. Chromium in bottom sediments Distribution of Cr concentrations in the Dunajec River sediment samples showed spatial and temporal diversity. At sites upstream from the reservoir (1 and 2), detected mean values were significantly higher (ANOVA, p < 0.006) than downstream (site 3) (Table 1). At these sites Cr concentrations increased from November 2000 to January 2001, and minimum values were detected in the periods following high flow events (May and October 2001) (Fig. 3b). The maximum value, 1.22 mg g 1 dw (November 2001), was found at site 1. Concentrations in sediment downstream from the reservoir (site 3) were in the range of 0.02–0.13 mg g 1 dw. Values for the reference site (4) did not exceed 0.06 mg g 1 dw. Chromium distribution in sediments showed a similar temporal and spatial pattern during a subsequent 2005 sampling campaign (Micula, 2006). The maximum concentrations observed in site 1, with mean values of 0.45 ± 0.38 mg g 1 dw, decreased by about 68–98% at site 2 (0.17 ± 0.30 mg g 1 dw). Downstream from the reservoir and in the reference site concentrations were in a similar range as during previous sampling (0.03 ± 0.01 and 0.01 ± 0.01 mg g 1 dw for sites 3 and 4, respectively). Investigation of the Czorsztyn Reservoir sediments (CzaplickaKotas et al., 2008) revealed Cr concentrations within the range of 0.01–0.23 mg g 1 dw. The highest values were detected in the samples collected from the vicinity of the dam and the outlet of one of the reservoir tributaries discharging water contaminated with the Cr from the local sources. 3.4. Manganese in suspended matter and bottom sediments In all investigated samples, Mn concentrations in the suspended matter were higher downstream from the reservoir (site 3), than in the rest of the investigated sites, with the exception of a sample taken in December 2001 from site 2. In this sample, the highest value
of 78.2 lg L 1 was detected. The temporal distribution of Mn in the suspended matter for all the sites showed an increase in April 2001, followed by a noticeable decrease in July 2001, also observed for Cr concentrations. Manganese concentrations in the bottom sediments were generally higher at site 3 than in the other sites, with the mean value (Table 1) significantly higher (ANOVA, p < 0.003) than in the other sites. The highest value detected at this site was 4.19 mg g 1 dw. At the reference site (4) Mn concentrations in bottom sediments did not exceed 0.06 mg g 1 dw.
4. Discussion 4.1. Fate of chromium The results clearly indicate that the temporal pattern of the Cr concentration in river water is related to the local tanneries activities. In the upper Dunajec River increased tannery wastewater discharges occur mainly from November to March, in the high season of tanned leather production. During this time of year, a decrease in the flow of water is also observed. Both processes contribute to the distinct increase of Cr concentrations. The inverse correlations of total dissolved Cr (sum of the dissolved Cr(III) and Cr(VI)) concentration with the Dunajec River flow (r = 0.53 and r = 0.45 for sites 1 and 2, respectively), however insignificant, indicate that total dissolved Cr concentrations may temporarily exceed the highest observed values, (89.2 lg L 1 for site 1 and 42.2 lg L 1 for site 2, respectively) even at the same level of tannery wastewater discharges. To establish the relative importance of the variation of the river flow and the tannery’s activities for measured Cr concentrations, stepwise regression has been performed. The obtained coefficients of determination for Cr concentrations and Cr loads (r2 = 0.56 and 0.77 for the sites 1 and 2, respectively) were much higher than those calculated for Cr concentrations and river flows (r2 = 0.28 and 0.20). This suggests that concentrations of Cr are much more dependent on the activity of tanneries than on variations of stream flow. Total dissolved Cr concentrations observed downstream from the reservoir (site 3) did not exceed 2 lg L 1, but remained higher than at the reference site (4). Since, the use of Cr in the tanning process results in the discharge of Cr mainly it trivalent form (Pereira de Abreu, 2006), this form is also the most abundant in water samples from the tanneryimpacted aquatic systems. In this study, Cr(III) constituted 90–97% of the total dissolved fraction in samples from site 1, and 68–98% from site 2. As shown by Dominik et al. (2003, 2007) about 50% of this dissolved Cr(III) in the Dunajec River was associated with colloids. In general, Cr associated with suspended matter constituted 10–87% of total Cr (dissolved and particulate) in the water samples. Therefore, the 1.3–4 times decrease in total Cr concentration over the distance of 7.5 km between sites 1 and 2 can be attributed to the sedimentation of particulate Cr(III) from the water column to bottom sediments, and possible removal of colloidal Cr(III) via ‘‘colloidal pumping’’. Although, the Dunajec River is joined by a couple of small tributaries in the span between these sites, the increase of flow is in the range of 9–15%. Thus, the impact of the dilution factor between sites 1 and 2 on Cr concentration decrease is fairly negligible even if the tributaries were completely Cr-free. The removal of Cr(III) via rapid association with particles favors the accumulation in river sediments in the area of tannery discharges. Average Cr concentrations in the sediment samples from sites upstream from the reservoir (0.72 mg g 1 dw with CV = 49% and 0.38 mg g 1 dw with CV = 71% for sites 1 and 2, respectively) considerably exceeded the background concentration for freshwater sediments, 0.1 mg g 1 dw (Salomons and Förstner, 1984), and
E. Szalinska et al. / Applied Geochemistry 25 (2010) 116–122
121
concentrations observed in the reference sampling site 4 (0.03 mg g 1 dw). Concentrations of Cr in sediment samples collected upstream from the reservoir were well correlated with total concentrations in water (r = 0.77, n = 7, p < 0.05), and decreased with distance, between sites 1 and 2. No correlation between the sediment grain-size distribution and Cr concentrations has been found in the riverine samples (Pawlikowski et al., 2006). This suggests that Cr distribution in the Dunajec River mostly reflects the proximity of contamination sources, and very little hydrological sorting is involved in this process. 4.2. Transport of chromium As described above, Cr(III) is rapidly removed from the water column, and water transport processes remain restricted to Cr(VI), associated almost completely with the dissolved fraction (Dominik et al., 2003, 2007). Since, the Cr(VI) concentrations remained negligible in comparison to the total dissolved Cr concentrations it can be concluded that water transport processes are not primary in the system. The subsequent transport of Cr is mostly related to the hydrological conditions in the system, especially, to the conditions favoring the translocation of sediment mass, like high flow events. The temporal distribution of Cr concentrations in sediment samples has shown that Cr accumulated in the area of discharges through the whole period of intensive tannery activity, with maximum values up to 1.22 and 0.81 mg g 1 dw for sites 1 and 2, respectively. After the high flow events, Cr concentrations in sediments showed a distinct decrease (Fig. 3b). In samples collected after the snow thawing period (May), concentrations were reduced to 12–45% of the maximum values. After the early summer rainstorms events (occurring regularly in June July), concentrations were reduced to background levels. In the case of the upper Dunajec River catchment further transport of sediments flushed out during the high water events is limited by the presence of the impoundment reservoir, due to reduction of the current velocity. As in general, Cr concentrations in the sediment samples collected downstream from the reservoir (site 3) were very low, with a maximum value of 0.13 mg g 1 dw, it can be concluded that the reservoir acts as a sediment trap for a substantial part of the Cr load. Indeed, the assessment of Cr distribution in the Czorsztyn reservoir sediments performed in 2006 (Czaplicka-Kotas et al., 2008) showed that Cr originating from the Dunajec River is transported to and settled in the reservoir. The broad estimation of the annual flux of total Cr showed that about 73% (5.5 tons) of the Cr supplied by the Dunajec River is retained in the reservoir (Szalinska et al., in preparation). Considering the recurrent pattern of Cr contamination and inevitable hydrological processes in the catchment it would be expected that the increase of the Cr load in the reservoir will be the same every year. 4.3. Potential threat of chromium contamination for the ecosystem Since Cr speciation showed that Cr(III) was predominant and this form is largely bound to the particulate and colloidal phases, a special concern for ecosystem health may be posed by sediment contamination. Concentrations of Cr in sediments in the vicinity of wastewater discharges were high and exceeded guideline values. Based on the sediment quality objectives established for the severe effect level (SEL, 0.11 mg g 1 dw) (Persaud et al., 1992), the sediments upstream from the reservoir showed the Cr concentrations well above the SEL during most of the year. The highest concentration observed in sediments at site 1 exceeded the SEL by a factor of 11. There is little doubt that such a level of contamination affects the biota, even if the acute toxicity effects of Cr(III) in sediments are not evident at similar concentrations (Rifkin et al., 2004). Since,
Fig. 4. Manganese concentrations in sediments and the Cr(VI)/Cr(III) ratios in water for the Dunajec River sampling sites.
elevated Cr concentrations in sediments were encountered during following investigations in the catchment (Micula, 2006) the longterm effects of Cr-contaminated sediments could be of particular concern for benthic invertebrates. Indeed, a reduced biodiversity of benthic invertebrates has been observed in the Dunajec River (Szczesny, 1995) although the relationship to Cr contamination in sediments has never been clearly demonstrated. Preliminary studies on Cr bioavailability have shown that Cr is available for chironomidae larvae and enters the food-web of the upper Dunajec River (Szalinska et al., 2008) however, there is no exact relationship between Cr levels in sediments and indigenous chironomids (Ferrari et al., 2006). Chromium(III) accumulated in sediments may also be subjected to oxidation processes and subsequent transformation into the more toxic, hexavalent form. Chromium oxidation is theoretically possible in the presence of Mn(IV) oxides (Rai et al., 1989; Richard and Bourg, 1991), and indeed increased Mn concentration in suspended and bottom sediments has been observed in this study (Table 1). Although Mn speciation was not performed in this study, the total Mn concentrations were considered a reasonable proxy of the oxidative potential for Cr(III), at least for local comparison purposes. A pronounced relationship between Cr(VI)/Cr(III) ratio in water and the Mn concentrations in bottom sediments has been observed for site 3 (r = 0.94, p < 0.005; Fig. 4). The noticeable increase of Mn concentrations in sediments for this site seems to be related to the intense water aeration and oxidation process during release of water from the Czorsztyn Reservoir. 5. Conclusions This study has demonstrated that Cr fate and transport in the tannery-impacted aquatic system are temporally and spatially restricted. The distribution pattern is mostly defined by the source localities and their characteristics. However, after discharge from tanneries, Cr distribution and mobility are determined by hydrological conditions. Since, most of the Cr is deposited in sediments the risk related to elevated Cr concentrations in sediments (up to 1.22 mg g 1 dw) is primarily restricted to the area of discharge. However, in the long-term, the process of flushing out of sediments during high water events may shift the main context of the problem towards previously uncontaminated sites. In the case of the upper Dunajec River catchment the impoundment reservoir exerts a positive role in limiting the geographic extension of Cr(III) pollution. The study, demonstrating the recurrent pattern of Cr contamination, also raises questions about the possible chronic, ecologic impact related to high Cr concentrations in sediments and the possible interconversion between Cr(III) and Cr(VI) depending on processes regulating Cr mobility at the sediment–water interface.
122
E. Szalinska et al. / Applied Geochemistry 25 (2010) 116–122
This study integrates spatial and temporal trends of the total Cr and Cr(VI) contamination in water, suspended particulate matter and sediments of the catchment impacted with tannery effluents. This provides a reference framework, which can be used in more focused studies in the future, involving the potential bioavailability of Cr and its impact on the aquatic environment. Acknowledgements The authors would like express their thanks to Andrzej Jasztal (WIOS Nowy Sacz), Michał Krzyszkowski (Niedzica Hydro-Electric Power Plant) and Zofia Znachowska (Cracow University of Technology) for their help in the field and laboratory work. This study was a part of the Ph.D. thesis of the senior author. A part of analytical work performed at the Institute F.-A. Forel and the Academy of Science and Technology in Cracow was supported by the Swiss National Science Foundation (Grant No. 20-65098.01). References Armienta, M.A., Morton, O., Rodriguez, R., Cruz, O., Aguayo, A., Ceniceros, N., 2001. Chromium in a tannery wastewater irrigated area, Leon Valley, Mexico. Bull. Environ. Contam. Toxicol. 66, 189–195. Bobrowski, A., Bas, B., Dominik, J., Niewiara, E., Szalinska, E., Vignati, D., Zare˛bski, J., 2004. Chromium speciation study in polluted waters using catalytic adsorptive stripping voltammetry and tangential flow filtration. Talanta 63, 1003–1012. Cranston, R.E., Murray, J.W., 1980. Chromium species in the Columbia River and estuary. Limnol. Oceanog. 25, 1104–1112. Czaplicka-Kotas, A., Szalin´ska, E., Wachałowicz, M., 2008. Chromium distribution in the Czorsztyn Reservoir bottom sediments. Gosp. Wod. 11, 457–462 (in Polish). Dominik, J., Bas, B., Bobrowski, A., Dworak, T., Koukal, B., Niewiara, E., Pereira de Abreu, M.-H., Rosee, P., Szalinska, E., Vignati, D., 2003. Partitioning of chromium(VI) and chromium(III) between dissolved and colloidal forms in a stream and reservoir contaminated with tannery waste water. J. Phys. IV 107, 385–388. Dominik, J., Vignati, D.A.L., Koukal, B., Pereira de Abreu, M.-H., Kottelat, R., Szalinska, E., Bas, B., Bobrowski, A., 2007. Speciation and environmental fate of chromium in rivers contaminated with tannery effluents. Eng. Life Sci. 7, 155–169. Fal, B., Bogdanowicz, E., Czernuszenko, W., Dobrzyn´ska, I., Koczyn´ska, A., 2000. Characteristic Flows for Main Polish Rivers in 1951–1995, vol. 26. Materials of Institute of Meteorology and Water Management (issue: Hydrology and Oceanography (in Polish)). Ferrari, B., Vignati, D.A.L., Kottelas, R., Dominik, J., Szalinska, E., Czaplicka-Kotas, A., 2006. Chromium bioaccumulation in chironomids exposed to sediments contaminated by tannery effluents. In: SETAC North America 27th Annual Meeting, Montreal, November 5 9. Joradao, C.P., Pereira, J.L., Jham, G.N., 1997. Chromium contamination in sediment, vegetation and fish caused by tanneries in the State of Minas Gerais, Brazil. Sci. Total Environ. 207, 1–11. Khamar, M., Bouya, D., Ronneau, C., 2000. Organic and metallic pollution of waters and sediments of a Moroccoan River impacted by wastwaters. Water Qual. Res. J. Can. 35, 147–161 (in French).
Kim, J.G., Dixon, J.B., Chusuei, C.C., Deng, Y., 2002. Oxidation of chromium(III) to (VI) by manganese oxides. Soil Sci. Am. J. 66, 306–315. Koukal, B., Dominik, J., Vignati, D., Arpagaus, P., Santiago, S., Ouddane, B., Benaabidate, L., 2004. Assessment of water quality and toxicity of polluted rivers Fez and Sebou in the Region of Fez (Marocco). Environ. Pollut. 13, 163– 172. Micula, M., 2006. Chromium Distribution in the Upper Dunajec River Sediments. Masters Thesis, Cracow Univ. Technology (in Polish). Osol, 1986. Directive on Threats to Soils. RS 814.015. Le Conseil Féderal Suisse (in French). Ostrowska, A., Gawlinski, S., Szczubiałka, Z., 1991. Bulletins of Institute of Environmental Protection, Warsaw, Poland (in Polish). Pawlikowski, M., Szalinska, E., Wardas, M., Dominik, J., 2006. Chromium originating from tanneries in river sediments: a preliminary investigation from the upper Dunajec River (Poland). Polish J. Environ. Studie 15, 885–894. Pawlisz, A.V., Kent, R.A., Schneider, U.A., Jefferson, C., 1997. Canadian water quality guidelines for chromium. Environ. Toxicol. Water Qual. 12, 123–183. Pereira, M.J., Resende, P., Azeiteiro, U.M., Oliveira, J., de Figueiredo, D.R., 2005. Differences in the effects of metals on growth of two freshwater green algae (Pseudokirchneriella subcapitata (Korshikov) Hindak and Gonium pectorale Müller). Bull. Environ. Contam. Toxicol. 75, 515–522. Pereira de Abreu, M.-H., 2006. Spéciation et mobilité du chrome dans les environnements aquatiques pollués par de tannerie. Terre Environ. 62 (in French). Persaud, D., Jaagumagi, R., Hayton, A., 1992. Guidelines for the Protection and Management of Aquatic Sediment Quality in Ontario. Water Resources Branch, Ontario Ministry of the Environment, Toronto, Ontario. Rai, D., Eary, L.E., Zachara, J.M., 1989. Environmental chemistry of chromium. Sci. Total Environ. 86, 15–23. Richard, F.C., Bourg, A.C.M., 1991. Aqueous geochemistry of chromium: a review. Water Res. 25, 807–816. Rifkin, E., Gwinn, P., Bouver, E., 2004. Chromium and sediment toxicity. Environ. Sci. Technol. 38, 267A–271A. Rodrigues, M.L.K., Formoso, M.L.L., 2006. Geochemical distribution of selected heavy metals in stream sediments affected by tannery activities. Water, Air, Soil Pollut. 169, 167–184. Salomons, W., Förstner, U., 1984. Metals in Hydrocycle. Springer, Berlin. Stepniewska, Z., Bucior, K., Bennicelli, R.P., 2004. The effects of MnO2 on sorption and oxidation of Cr(III) by soils. Geoderma 122, 291–296. Szalinska, E., 2001. Surface water quality in the upper Dunajec watershed, 1995 1998. Gospodarka Wodna 3, 114–118 (in Polish). Szalinska, E., 2002. Chromium Transformations in the Water Environment Contaminated with Tannery Waste Water, vol. 283. Monographs of Cracow University of Technology (issue: Environmental Engineering (in Polish)). Szalinska, E., Dominik, J., Bobrowski, A., Bas, B., 2003. Fate of tannery chromium contamination in a stream: temporal and spatial evolution of chromium(III) and chromium(VI). J. Phys. IV 107, 1275–1278. Szalinska, E., Vignati, D.A.L., Czaplicka-Kotas, A., Ferrari, B.J.D., Dominik, J., 2008. Bioavailability of sedimentary chromium for chironomids in the upper Dunajec River (southern Poland). Verhandlungen IVL 30, 534–536. Szalinska, E., Vignati, D.A.L., Dominik J., in preparation. Calculating loading in a river with seasonaly variable flow and pollutant discharge. Szczesny, B. (Ed.), 1995. Degradation of benthic invertebrates fauna in the Dunajec River in the area of the Pieniny National Park. Ochrona Przyrody 52, 207–211 (in Polish). Thompson, S.L., Manning, F.C.R., McColl, S.M., 2002. Comparison of the toxicity of chromium(III) and chromium(VI) to cyanobacteria. Bull. Environ. Contam. Toxicol. 69, 286–293.
Contents lists available at ScienceDirect
Applied Geochemistry journal homepage: www.elsevier.com/locate/apgeochem
Seasonal transport pattern of chromium(III and VI) in a stream receiving wastewater from tanneries Ewa Szalinska a,*, Janusz Dominik b, Davide A.L. Vignati b,c, Andrzej Bobrowski d, Boguslaw Bas d a
Institute of Water Supply and Environmental Protection, Cracow University of Technology, ul. Warszawska 24, 31-155 Krakow, Poland Institut F.-A. Forel, University of Geneva, route de Suisse 10, CH-1290 Versoix, Switzerland c CNR-IRSA, Via della Mornera 25, 20047 Brugherio, Italy d Faculty of Materials Science and Ceramics, University of Science and Technology, al. Mickiewicza 30, 30-059 Krakow, Poland b
a r t i c l e
i n f o
Article history: Received 8 July 2009 Accepted 2 November 2009 Available online 6 November 2009 Editorial handling by Dr. R. Fuge
a b s t r a c t Water, suspended matter and sediment samples from a system heavily impacted by wastewater from numerous small tanneries (the upper Dunajec River, southern Poland) were collected to establish the annual cycle of Cr. To study possible oxidation processes the speciation of Cr and Mn concentrations were also investigated. This study showed that Cr(III and VI) temporal and spatial distributions are regulated by coupled anthropogenic (source location and emissions) and hydrologic factors (water flow and particle transport). Chromium(III) concentrations in all compartments varied seasonally as a function of the hydrological regime, production cycle in tanneries and distance from the discharge location. Cr(III) was largely associated with the particulate phase and rapidly deposited in river bed sediments. Contaminated river sediments were however flushed during flood periods to the reservoir located downstream from tanneries. During the tanning season (November to March), Chromium(III) concentrations in the water column and total Cr concentration in sediments exceeded relevant ecotoxicological guidelines only upstream from the reservoir, which trapped about 70% of the annual Cr(III) load transported by the Dunajec river. A correlation between Cr(VI)/Cr(III) ratios and Mn concentration in sediments downstream from the reservoir suggests the possibility of Cr(III) oxidation in natural conditions. Ó 2009 Elsevier Ltd. All rights reserved.
1. Introduction Tanneries are important sources of Cr contamination in surface waters throughout the world, especially in regions where sheep breeding and tannery crafts still remain important for economical reasons (Joradao et al., 1997; Khamar et al., 2000; Armienta et al., 2001; Koukal et al., 2004; Rodrigues and Formoso, 2006). The geographical extension of Cr pollution released from tanneries is related to the extent of discharges and hydrological processes. Equally important are Cr speciation in the discharge, and the possibility of its transformation. The environmental fate and ecotoxicologic risk related to Cr emissions from these sources are poorly known because of the complex chemistry of this element in surface water. Concentrations and proportions of trivalent and hexavalent Cr in the aquatic environment, can vary with local conditions. Generally, Cr(VI) is considered more toxic than Cr(III) (e.g. Pawlisz et al., 1997), but a few studies have reported contrasting findings (Thompson et al., 2002; Pereira et al., 2005) suggesting that both forms can adversely affect biota. The identification and quantification of Cr species therefore becomes important from the ecotoxicological point of view. Furthermore, Cr(III) compounds can be * Corresponding author. Tel.: +48 12 628 2870; fax: +48 12 628 2042. E-mail address: [email protected] (E. Szalinska). 0883-2927/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.apgeochem.2009.11.002
rapidly removed from the water column via adsorption–coagulation–sedimentation processes and can accumulate in sediments (Cranston and Murray, 1980; Dominik et al., 2007). High concentrations of Cr in sediments in the vicinity of discharges may affect benthic biota as well. On the other hand, oxidation of Cr(III) to Cr(VI) in the presence of Mn oxides (e.g. Kim et al., 2002; Stepniewska et al., 2004) may result in Cr remobilization from contaminated sediments. A major challenge in assessing Cr fate, transport, and potential risk for aquatic biota in a watershed is usually the scale of the system, and a lack of datasets integrating water, suspended matter and sediments. Furthermore, a number of confounding factors, such as multiple polluting sources and a presence of various contaminants, increases the level of difficulty in evaluating the potential ecotoxicological risk. The upper Dunajec River (West Carpathians Mountains, southern Poland) is a small system particularly suitable for studying the environmental fate and transport of Cr contamination and to assess the relative importance of processes regulating spatial and temporal distribution. The existence of an impoundment reservoir, constructed to protect the area against flood events, plays a role in Cr transport within this system. This is a region with modest industrialization and urbanization, where agriculture and animal breeding provide most of the
E. Szalinska et al. / Applied Geochemistry 25 (2010) 116–122
employment, and where traditional tannery crafts are still practiced. The latter activity is the actual source of Cr contamination since Cr is used as a tanning agent. The tanned leather is produced mostly in small tanneries (300), located in a well constrained section of the watershed. Due to improper tannery wastewater management, pre-treated or raw wastewaters from these tanneries are discharged into local sewers or directly into the Dunajec River and its tributaries (Szalinska, 2001). Other metals are not appreciably enriched above background levels in this watershed, while contamination with organic micropollutants occurs only following accidental spills (Szalinska et al., 2003). The mean monthly flows (1951–1980) of the Dunajec River vary from 6 m3 s 1 in winter months to 20 m3 s 1 during snow thawing (April) and heavy rainfall (June–July) periods. Since, this mean maximum flow can be exceeded by several hundred times between June and July (up to 800 m3 s 1; Fal et al., 2000), an impoundment reservoir was constructed (1997) on the Dunajec River to protect the area against recurrent flood events. Taking advantage of this ideal setting a full year survey of Cr in water, suspended particulate matter and sediments was performed in this study to determine the environmental fate of Cr in a tannery-impacted ecosystem. Design of the sampling strategy also permitted the assessment of the role of the reservoir as a sink for Cr and in limiting Cr transport downstream. Potential threats to the ecosystem such as the impact on biota and the possibility of Cr oxidation in the presence of Mn were also assessed. To verify the findings of this study the results from other investigations in the upper Dunajec River region (2005 and 2006) performed by the authors are included in Section 4.
2. Materials and methods 2.1. Sampling area and sample collection Water and sediment samples were collected from the Dunajec River, November 2000 through December 2001, approximately once a month. However, due to the unfavorable weather conditions
117
only nine water, and seven sediment samples could be obtained. Additional samples were taken from Bialka River in the same period. The sampling localities are shown in Fig. 1. The Dunajec River samples were taken from sites upstream (1 and 2) and downstream (3) from the Czorsztyn Reservoir. Sampling site 1 was located in the vicinity of the main Cr inputs. The Bialka River sampling site (4) was considered to be a non-contaminated reference point. Surface water samples were collected using hand held, HNO3washed, polyethylene bottles. Water samples were filtered (0.45 lm, cellulose acetate) within 2 h of collection and filters were dried and weighed. Filtrates for total dissolved Cr determination were acidified with HNO3 (ACS grade) to a pH below 2. Nonacidified filtrates for Cr(VI) determination were kept below 4 °C until delivered to the laboratory and measured (within 8 h). Sediment samples from the Dunajec River were gently collected from the uppermost oxic layer using a plastic shovel and stored in plastic containers. All sediment samples were sieved using a 2 mm plastic sieve in order to remove major detritus, and air-dried.
2.2. Laboratory analyses Filtrates were analyzed for total dissolved Cr and for Cr(VI) by catalytic adsorptive stripping voltammetry (CAdSV) according to the method described by Bobrowski et al. (2004), while Cr(III) was calculated from the difference. The detection limit for total Cr and Cr(VI) was 0.005 lg L 1. Mean values for blanks were below reported detection limits. All measurements were performed three times and reported as mean values. Replicate measurements agreed within <5%. For selected samples, measurements of total Cr by the CAdSV technique were in very good agreement with ICP-MS and GFAAS determinations (r > 0.99, n = 6; Szalinska, 2002). The suspended matter extraction was performed according to the Osol protocol (Osol, 1986) in an ultrasonic mineralizator (ULTRAsonic 104X) for 10 min with 10 mL 2N HNO3. Samples were then heated at 100 °C for 12 h and allowed to cool. After centrifu-
Fig. 1. Overview of the sampling area and positions of the sampling sites.
E. Szalinska et al. / Applied Geochemistry 25 (2010) 116–122
gation (4000 rpm for 20 min), supernatants were diluted by a ratio of 200 with 1% HNO3 before measurement. Chromium measurements were performed by ICP-MS (HP-4500 Agilent) and the detection limit was 0.01 lg L 1. Previous tests have shown that the Osol procedure extracted 80–100% of the total recoverable Cr from the contaminated sediment samples (r > 0.99, n = 9; Szalinska, 2002). Due to the small amount of suspended matter retained on filters, only some of them were subjected to extraction. Total digestion of sediment samples, following dry mineralization at 450 °C for 6 h, was performed in Kjeldahl flasks with 10 mL HNO3 and 5 mL HClO4 (ACS grade) for 12 h according to the protocol described by Ostrowska et al. (1991). Samples were then heated to 250 °C and cooled. After adding 10 mL HCl (1 + 1) samples were heated at 100 °C for 2 h and cooled again. After filtration, the supernatant was transferred to LDPE bottles and brought up to 50 mL with MQ water. Chromium and Mn concentrations in sediments were measured by flame AAS (UNICAM 939 AA Spectrometer) and the reported detection limit was 0.02 mg L 1 for both metals.
3. Results 3.1. Chromium in water In all investigated Dunajec River sites, concentrations of dissolved Cr(VI) did not exceed 4 lg L 1 (Fig. 2a). Concentrations were relatively high in November and December and decreased in other months. Minimum values (below 0.3 lg L 1) were detected in 25
4
20
3
15
2
10
]
5
1
1
5
0
0 Dec 00
Jan 01
Mar 01
Apr 01
Sampling site 1
May 01
Jul 01
Sampling site 2
Oct 01
Nov 01
Dec 01
Sampling site 3
80
20
60
15
40
10
1
]
25
chromium(III) [µg L-1]
(b) 100
flow [m3 s-1]
chromium(VI) [µg L-1]
(a)
During Cr and Mn analyses, calibration solutions, blanks, and standards were re-run every 10 samples. Precision was monitored by running duplicates of any two real samples placed in random order within every 10 samples. To assess contamination, three method blanks were randomly processed through the procedure. Mean values for blanks were below reported detection limits. Accuracy was assured through the use of a certified reference sediment material STSD-1 and STSD-2. Percentage recovery of Cr and Mn with respect to certified values was in the 90–110% range.
flow [m3 s-1]
118
20
5
0
0 Dec 00
Jan 01
Mar 01
Apr 01
Sampling site 1
May 01
Jul 01
Sampling site 2
Oct 01
Nov 01
Dec 01
Sampling site 3
Fig. 2. Concentrations of dissolved Cr(VI) (a) and Cr(III) (b) in Dunajec River water during the sampling period. Bars represent the Dunajec River mean monthly flows for the gauge cross-section (see Fig. 1). Note the different vertical scales for parts (a) and (b).
119
E. Szalinska et al. / Applied Geochemistry 25 (2010) 116–122 Table 1 Mean (±std) chromium and manganese concentrations in water (lg L Bialka River (4). Site
1
), suspended matter (lg L
Water
1 2 3 4
) and sediments (mg g
1
sm) from the Dunajec River sites (1–3), and from the
Suspended matter
Sediments
Cr(VI)
Cr(III)
Cr
Mn
Cr
Mn
1.1 ± 1.2 1.4 ± 1.1 0.3 ± 0.2 0.1 ± 0.1
23.4 ± 27.5 11.7 ± 12.5 0.6 ± 0.5 0.2 ± 0.2
12.8 ± 13.1 4.0 ± 2.5 2.0 ± 1.8 0.3 ± 0.5
14.6 ± 23.4 23.2 ± 31.5 29.5 ± 24.2 2.4 ± 3.6
0.72 ± 0.36 0.43 ± 0.30 0.06 ± 0.04 0.03 ± 0.02
1.05 ± 0.72 0.53 ± 0.12 2.61 ± 1.06 0.16 ± 0.09
months with high flows, above 20 m3 s 1 (April and July). For both sites upstream from the reservoir, mean concentrations were comparable (Table 1), but for the same date higher values were observed at site 2 (except for November 2001). Downstream from the reservoir (site 4), the Cr(VI) mean concentration was lower, but still three times higher than the concentration for the reference site 4. Maximum concentrations of dissolved Cr(III), exceeding 50 lg L 1, were detected at site 1 in December 2000 and November
(a)
1
2001 (Fig. 2b). For site 2, Cr(III) peak concentrations were detected during the same months, but were about 40 lg L 1 lower than at site 1. As a rule, concentrations of Cr(III) were higher at site 1 than at 2 during the whole sampling period, however the mean concentrations (Table 1) for these sites were not significantly different. The temporal distribution of Cr(III) in sites 1 and 2 showed a distinct increase in late fall/winter months (November and December), and decreased in April and July. Downstream from the
40
25
chromium [µg L-1]
15 20 10
suspended solids [mg L-1]
20 30
10 5
0
0 Apr 01
Jul 01
Sampling site 1
Oct 01
Nov 01
Sampling site 2
Dec 01
Sampling site 3 25
1.0
20
0.8
15
0.5
10
0.3
5
chromium [mg g-1 dry weight]
(b) 1.3
0.0
Flow [m3 s-1]
Mar 01
0 Nov 00
Dec 00
Sampling site 1
Jan 01
Mar 01
Sampling site 2
May 01
Oct 01
Nov 01
Sampling site 3
Fig. 3. Concentrations of Cr in Dunajec River suspended matter (a) and sediments (b) during the sampling period. Bars represent distribution of the Dunajec River mean monthly suspended solids concentrations for the gauge cross-section.
120
E. Szalinska et al. / Applied Geochemistry 25 (2010) 116–122
reservoir (site 3), the mean Cr(III) concentration was one order of magnitude lower than at sites 1 and 2, while values for the reference site (4) were in the range of 0.03–0.4 lg L 1. The two redox forms of Cr were significantly correlated (p < 0.05, Spearman test) for upstream sites (n = 10, r = 0.96 and r = 0.80 for sites 1 and 2, respectively) but not correlated for site 3. 3.2. Chromium in suspended matter The suspended matter concentrations followed the distribution of flows in the Dunajec River. The concentration increased in the snow thawing period (March and April) up to 15 mg L 1 (Fig. 3a) and reached maximum values (up to 23 mg L 1) in July, when heavy rainfall occurred. Chromium concentrations measured in the suspended matter are reported below in lg L 1, instead of the usual lg g 1, to elucidate the fate of the total Cr (dissolved and particulate), also given in lg L 1, in the further discussion. In all investigated samples, Cr concentrations in the particulate phase were higher at site 1 than in the rest of the investigated sites, with the highest detected value being 37.9 lg L 1. The temporal distribution of Cr concentrations in suspended matter for both upstream sites (1 and 2) showed a similar pattern, with a noticeable decrease in July 2001, when the observed concentration of suspended solids was highest (Fig. 3a). The mean concentration in the site downstream from the reservoir (3) was lowest (Table 1) but not significantly different from the upstream site concentrations. Also a t-test showed that there was no significant difference between concentrations on particular sampling days. In samples from the reference site (4) concentrations of particulate Cr were close to the detection limit (0.15–0.30 lg L 1) due to low suspended solid concentrations, below 4 mg L 1, and low Cr content. 3.3. Chromium in bottom sediments Distribution of Cr concentrations in the Dunajec River sediment samples showed spatial and temporal diversity. At sites upstream from the reservoir (1 and 2), detected mean values were significantly higher (ANOVA, p < 0.006) than downstream (site 3) (Table 1). At these sites Cr concentrations increased from November 2000 to January 2001, and minimum values were detected in the periods following high flow events (May and October 2001) (Fig. 3b). The maximum value, 1.22 mg g 1 dw (November 2001), was found at site 1. Concentrations in sediment downstream from the reservoir (site 3) were in the range of 0.02–0.13 mg g 1 dw. Values for the reference site (4) did not exceed 0.06 mg g 1 dw. Chromium distribution in sediments showed a similar temporal and spatial pattern during a subsequent 2005 sampling campaign (Micula, 2006). The maximum concentrations observed in site 1, with mean values of 0.45 ± 0.38 mg g 1 dw, decreased by about 68–98% at site 2 (0.17 ± 0.30 mg g 1 dw). Downstream from the reservoir and in the reference site concentrations were in a similar range as during previous sampling (0.03 ± 0.01 and 0.01 ± 0.01 mg g 1 dw for sites 3 and 4, respectively). Investigation of the Czorsztyn Reservoir sediments (CzaplickaKotas et al., 2008) revealed Cr concentrations within the range of 0.01–0.23 mg g 1 dw. The highest values were detected in the samples collected from the vicinity of the dam and the outlet of one of the reservoir tributaries discharging water contaminated with the Cr from the local sources. 3.4. Manganese in suspended matter and bottom sediments In all investigated samples, Mn concentrations in the suspended matter were higher downstream from the reservoir (site 3), than in the rest of the investigated sites, with the exception of a sample taken in December 2001 from site 2. In this sample, the highest value
of 78.2 lg L 1 was detected. The temporal distribution of Mn in the suspended matter for all the sites showed an increase in April 2001, followed by a noticeable decrease in July 2001, also observed for Cr concentrations. Manganese concentrations in the bottom sediments were generally higher at site 3 than in the other sites, with the mean value (Table 1) significantly higher (ANOVA, p < 0.003) than in the other sites. The highest value detected at this site was 4.19 mg g 1 dw. At the reference site (4) Mn concentrations in bottom sediments did not exceed 0.06 mg g 1 dw.
4. Discussion 4.1. Fate of chromium The results clearly indicate that the temporal pattern of the Cr concentration in river water is related to the local tanneries activities. In the upper Dunajec River increased tannery wastewater discharges occur mainly from November to March, in the high season of tanned leather production. During this time of year, a decrease in the flow of water is also observed. Both processes contribute to the distinct increase of Cr concentrations. The inverse correlations of total dissolved Cr (sum of the dissolved Cr(III) and Cr(VI)) concentration with the Dunajec River flow (r = 0.53 and r = 0.45 for sites 1 and 2, respectively), however insignificant, indicate that total dissolved Cr concentrations may temporarily exceed the highest observed values, (89.2 lg L 1 for site 1 and 42.2 lg L 1 for site 2, respectively) even at the same level of tannery wastewater discharges. To establish the relative importance of the variation of the river flow and the tannery’s activities for measured Cr concentrations, stepwise regression has been performed. The obtained coefficients of determination for Cr concentrations and Cr loads (r2 = 0.56 and 0.77 for the sites 1 and 2, respectively) were much higher than those calculated for Cr concentrations and river flows (r2 = 0.28 and 0.20). This suggests that concentrations of Cr are much more dependent on the activity of tanneries than on variations of stream flow. Total dissolved Cr concentrations observed downstream from the reservoir (site 3) did not exceed 2 lg L 1, but remained higher than at the reference site (4). Since, the use of Cr in the tanning process results in the discharge of Cr mainly it trivalent form (Pereira de Abreu, 2006), this form is also the most abundant in water samples from the tanneryimpacted aquatic systems. In this study, Cr(III) constituted 90–97% of the total dissolved fraction in samples from site 1, and 68–98% from site 2. As shown by Dominik et al. (2003, 2007) about 50% of this dissolved Cr(III) in the Dunajec River was associated with colloids. In general, Cr associated with suspended matter constituted 10–87% of total Cr (dissolved and particulate) in the water samples. Therefore, the 1.3–4 times decrease in total Cr concentration over the distance of 7.5 km between sites 1 and 2 can be attributed to the sedimentation of particulate Cr(III) from the water column to bottom sediments, and possible removal of colloidal Cr(III) via ‘‘colloidal pumping’’. Although, the Dunajec River is joined by a couple of small tributaries in the span between these sites, the increase of flow is in the range of 9–15%. Thus, the impact of the dilution factor between sites 1 and 2 on Cr concentration decrease is fairly negligible even if the tributaries were completely Cr-free. The removal of Cr(III) via rapid association with particles favors the accumulation in river sediments in the area of tannery discharges. Average Cr concentrations in the sediment samples from sites upstream from the reservoir (0.72 mg g 1 dw with CV = 49% and 0.38 mg g 1 dw with CV = 71% for sites 1 and 2, respectively) considerably exceeded the background concentration for freshwater sediments, 0.1 mg g 1 dw (Salomons and Förstner, 1984), and
E. Szalinska et al. / Applied Geochemistry 25 (2010) 116–122
121
concentrations observed in the reference sampling site 4 (0.03 mg g 1 dw). Concentrations of Cr in sediment samples collected upstream from the reservoir were well correlated with total concentrations in water (r = 0.77, n = 7, p < 0.05), and decreased with distance, between sites 1 and 2. No correlation between the sediment grain-size distribution and Cr concentrations has been found in the riverine samples (Pawlikowski et al., 2006). This suggests that Cr distribution in the Dunajec River mostly reflects the proximity of contamination sources, and very little hydrological sorting is involved in this process. 4.2. Transport of chromium As described above, Cr(III) is rapidly removed from the water column, and water transport processes remain restricted to Cr(VI), associated almost completely with the dissolved fraction (Dominik et al., 2003, 2007). Since, the Cr(VI) concentrations remained negligible in comparison to the total dissolved Cr concentrations it can be concluded that water transport processes are not primary in the system. The subsequent transport of Cr is mostly related to the hydrological conditions in the system, especially, to the conditions favoring the translocation of sediment mass, like high flow events. The temporal distribution of Cr concentrations in sediment samples has shown that Cr accumulated in the area of discharges through the whole period of intensive tannery activity, with maximum values up to 1.22 and 0.81 mg g 1 dw for sites 1 and 2, respectively. After the high flow events, Cr concentrations in sediments showed a distinct decrease (Fig. 3b). In samples collected after the snow thawing period (May), concentrations were reduced to 12–45% of the maximum values. After the early summer rainstorms events (occurring regularly in June July), concentrations were reduced to background levels. In the case of the upper Dunajec River catchment further transport of sediments flushed out during the high water events is limited by the presence of the impoundment reservoir, due to reduction of the current velocity. As in general, Cr concentrations in the sediment samples collected downstream from the reservoir (site 3) were very low, with a maximum value of 0.13 mg g 1 dw, it can be concluded that the reservoir acts as a sediment trap for a substantial part of the Cr load. Indeed, the assessment of Cr distribution in the Czorsztyn reservoir sediments performed in 2006 (Czaplicka-Kotas et al., 2008) showed that Cr originating from the Dunajec River is transported to and settled in the reservoir. The broad estimation of the annual flux of total Cr showed that about 73% (5.5 tons) of the Cr supplied by the Dunajec River is retained in the reservoir (Szalinska et al., in preparation). Considering the recurrent pattern of Cr contamination and inevitable hydrological processes in the catchment it would be expected that the increase of the Cr load in the reservoir will be the same every year. 4.3. Potential threat of chromium contamination for the ecosystem Since Cr speciation showed that Cr(III) was predominant and this form is largely bound to the particulate and colloidal phases, a special concern for ecosystem health may be posed by sediment contamination. Concentrations of Cr in sediments in the vicinity of wastewater discharges were high and exceeded guideline values. Based on the sediment quality objectives established for the severe effect level (SEL, 0.11 mg g 1 dw) (Persaud et al., 1992), the sediments upstream from the reservoir showed the Cr concentrations well above the SEL during most of the year. The highest concentration observed in sediments at site 1 exceeded the SEL by a factor of 11. There is little doubt that such a level of contamination affects the biota, even if the acute toxicity effects of Cr(III) in sediments are not evident at similar concentrations (Rifkin et al., 2004). Since,
Fig. 4. Manganese concentrations in sediments and the Cr(VI)/Cr(III) ratios in water for the Dunajec River sampling sites.
elevated Cr concentrations in sediments were encountered during following investigations in the catchment (Micula, 2006) the longterm effects of Cr-contaminated sediments could be of particular concern for benthic invertebrates. Indeed, a reduced biodiversity of benthic invertebrates has been observed in the Dunajec River (Szczesny, 1995) although the relationship to Cr contamination in sediments has never been clearly demonstrated. Preliminary studies on Cr bioavailability have shown that Cr is available for chironomidae larvae and enters the food-web of the upper Dunajec River (Szalinska et al., 2008) however, there is no exact relationship between Cr levels in sediments and indigenous chironomids (Ferrari et al., 2006). Chromium(III) accumulated in sediments may also be subjected to oxidation processes and subsequent transformation into the more toxic, hexavalent form. Chromium oxidation is theoretically possible in the presence of Mn(IV) oxides (Rai et al., 1989; Richard and Bourg, 1991), and indeed increased Mn concentration in suspended and bottom sediments has been observed in this study (Table 1). Although Mn speciation was not performed in this study, the total Mn concentrations were considered a reasonable proxy of the oxidative potential for Cr(III), at least for local comparison purposes. A pronounced relationship between Cr(VI)/Cr(III) ratio in water and the Mn concentrations in bottom sediments has been observed for site 3 (r = 0.94, p < 0.005; Fig. 4). The noticeable increase of Mn concentrations in sediments for this site seems to be related to the intense water aeration and oxidation process during release of water from the Czorsztyn Reservoir. 5. Conclusions This study has demonstrated that Cr fate and transport in the tannery-impacted aquatic system are temporally and spatially restricted. The distribution pattern is mostly defined by the source localities and their characteristics. However, after discharge from tanneries, Cr distribution and mobility are determined by hydrological conditions. Since, most of the Cr is deposited in sediments the risk related to elevated Cr concentrations in sediments (up to 1.22 mg g 1 dw) is primarily restricted to the area of discharge. However, in the long-term, the process of flushing out of sediments during high water events may shift the main context of the problem towards previously uncontaminated sites. In the case of the upper Dunajec River catchment the impoundment reservoir exerts a positive role in limiting the geographic extension of Cr(III) pollution. The study, demonstrating the recurrent pattern of Cr contamination, also raises questions about the possible chronic, ecologic impact related to high Cr concentrations in sediments and the possible interconversion between Cr(III) and Cr(VI) depending on processes regulating Cr mobility at the sediment–water interface.
122
E. Szalinska et al. / Applied Geochemistry 25 (2010) 116–122
This study integrates spatial and temporal trends of the total Cr and Cr(VI) contamination in water, suspended particulate matter and sediments of the catchment impacted with tannery effluents. This provides a reference framework, which can be used in more focused studies in the future, involving the potential bioavailability of Cr and its impact on the aquatic environment. Acknowledgements The authors would like express their thanks to Andrzej Jasztal (WIOS Nowy Sacz), Michał Krzyszkowski (Niedzica Hydro-Electric Power Plant) and Zofia Znachowska (Cracow University of Technology) for their help in the field and laboratory work. This study was a part of the Ph.D. thesis of the senior author. A part of analytical work performed at the Institute F.-A. Forel and the Academy of Science and Technology in Cracow was supported by the Swiss National Science Foundation (Grant No. 20-65098.01). References Armienta, M.A., Morton, O., Rodriguez, R., Cruz, O., Aguayo, A., Ceniceros, N., 2001. Chromium in a tannery wastewater irrigated area, Leon Valley, Mexico. Bull. Environ. Contam. Toxicol. 66, 189–195. Bobrowski, A., Bas, B., Dominik, J., Niewiara, E., Szalinska, E., Vignati, D., Zare˛bski, J., 2004. Chromium speciation study in polluted waters using catalytic adsorptive stripping voltammetry and tangential flow filtration. Talanta 63, 1003–1012. Cranston, R.E., Murray, J.W., 1980. Chromium species in the Columbia River and estuary. Limnol. Oceanog. 25, 1104–1112. Czaplicka-Kotas, A., Szalin´ska, E., Wachałowicz, M., 2008. Chromium distribution in the Czorsztyn Reservoir bottom sediments. Gosp. Wod. 11, 457–462 (in Polish). Dominik, J., Bas, B., Bobrowski, A., Dworak, T., Koukal, B., Niewiara, E., Pereira de Abreu, M.-H., Rosee, P., Szalinska, E., Vignati, D., 2003. Partitioning of chromium(VI) and chromium(III) between dissolved and colloidal forms in a stream and reservoir contaminated with tannery waste water. J. Phys. IV 107, 385–388. Dominik, J., Vignati, D.A.L., Koukal, B., Pereira de Abreu, M.-H., Kottelat, R., Szalinska, E., Bas, B., Bobrowski, A., 2007. Speciation and environmental fate of chromium in rivers contaminated with tannery effluents. Eng. Life Sci. 7, 155–169. Fal, B., Bogdanowicz, E., Czernuszenko, W., Dobrzyn´ska, I., Koczyn´ska, A., 2000. Characteristic Flows for Main Polish Rivers in 1951–1995, vol. 26. Materials of Institute of Meteorology and Water Management (issue: Hydrology and Oceanography (in Polish)). Ferrari, B., Vignati, D.A.L., Kottelas, R., Dominik, J., Szalinska, E., Czaplicka-Kotas, A., 2006. Chromium bioaccumulation in chironomids exposed to sediments contaminated by tannery effluents. In: SETAC North America 27th Annual Meeting, Montreal, November 5 9. Joradao, C.P., Pereira, J.L., Jham, G.N., 1997. Chromium contamination in sediment, vegetation and fish caused by tanneries in the State of Minas Gerais, Brazil. Sci. Total Environ. 207, 1–11. Khamar, M., Bouya, D., Ronneau, C., 2000. Organic and metallic pollution of waters and sediments of a Moroccoan River impacted by wastwaters. Water Qual. Res. J. Can. 35, 147–161 (in French).
Kim, J.G., Dixon, J.B., Chusuei, C.C., Deng, Y., 2002. Oxidation of chromium(III) to (VI) by manganese oxides. Soil Sci. Am. J. 66, 306–315. Koukal, B., Dominik, J., Vignati, D., Arpagaus, P., Santiago, S., Ouddane, B., Benaabidate, L., 2004. Assessment of water quality and toxicity of polluted rivers Fez and Sebou in the Region of Fez (Marocco). Environ. Pollut. 13, 163– 172. Micula, M., 2006. Chromium Distribution in the Upper Dunajec River Sediments. Masters Thesis, Cracow Univ. Technology (in Polish). Osol, 1986. Directive on Threats to Soils. RS 814.015. Le Conseil Féderal Suisse (in French). Ostrowska, A., Gawlinski, S., Szczubiałka, Z., 1991. Bulletins of Institute of Environmental Protection, Warsaw, Poland (in Polish). Pawlikowski, M., Szalinska, E., Wardas, M., Dominik, J., 2006. Chromium originating from tanneries in river sediments: a preliminary investigation from the upper Dunajec River (Poland). Polish J. Environ. Studie 15, 885–894. Pawlisz, A.V., Kent, R.A., Schneider, U.A., Jefferson, C., 1997. Canadian water quality guidelines for chromium. Environ. Toxicol. Water Qual. 12, 123–183. Pereira, M.J., Resende, P., Azeiteiro, U.M., Oliveira, J., de Figueiredo, D.R., 2005. Differences in the effects of metals on growth of two freshwater green algae (Pseudokirchneriella subcapitata (Korshikov) Hindak and Gonium pectorale Müller). Bull. Environ. Contam. Toxicol. 75, 515–522. Pereira de Abreu, M.-H., 2006. Spéciation et mobilité du chrome dans les environnements aquatiques pollués par de tannerie. Terre Environ. 62 (in French). Persaud, D., Jaagumagi, R., Hayton, A., 1992. Guidelines for the Protection and Management of Aquatic Sediment Quality in Ontario. Water Resources Branch, Ontario Ministry of the Environment, Toronto, Ontario. Rai, D., Eary, L.E., Zachara, J.M., 1989. Environmental chemistry of chromium. Sci. Total Environ. 86, 15–23. Richard, F.C., Bourg, A.C.M., 1991. Aqueous geochemistry of chromium: a review. Water Res. 25, 807–816. Rifkin, E., Gwinn, P., Bouver, E., 2004. Chromium and sediment toxicity. Environ. Sci. Technol. 38, 267A–271A. Rodrigues, M.L.K., Formoso, M.L.L., 2006. Geochemical distribution of selected heavy metals in stream sediments affected by tannery activities. Water, Air, Soil Pollut. 169, 167–184. Salomons, W., Förstner, U., 1984. Metals in Hydrocycle. Springer, Berlin. Stepniewska, Z., Bucior, K., Bennicelli, R.P., 2004. The effects of MnO2 on sorption and oxidation of Cr(III) by soils. Geoderma 122, 291–296. Szalinska, E., 2001. Surface water quality in the upper Dunajec watershed, 1995 1998. Gospodarka Wodna 3, 114–118 (in Polish). Szalinska, E., 2002. Chromium Transformations in the Water Environment Contaminated with Tannery Waste Water, vol. 283. Monographs of Cracow University of Technology (issue: Environmental Engineering (in Polish)). Szalinska, E., Dominik, J., Bobrowski, A., Bas, B., 2003. Fate of tannery chromium contamination in a stream: temporal and spatial evolution of chromium(III) and chromium(VI). J. Phys. IV 107, 1275–1278. Szalinska, E., Vignati, D.A.L., Czaplicka-Kotas, A., Ferrari, B.J.D., Dominik, J., 2008. Bioavailability of sedimentary chromium for chironomids in the upper Dunajec River (southern Poland). Verhandlungen IVL 30, 534–536. Szalinska, E., Vignati, D.A.L., Dominik J., in preparation. Calculating loading in a river with seasonaly variable flow and pollutant discharge. Szczesny, B. (Ed.), 1995. Degradation of benthic invertebrates fauna in the Dunajec River in the area of the Pieniny National Park. Ochrona Przyrody 52, 207–211 (in Polish). Thompson, S.L., Manning, F.C.R., McColl, S.M., 2002. Comparison of the toxicity of chromium(III) and chromium(VI) to cyanobacteria. Bull. Environ. Contam. Toxicol. 69, 286–293.