Speciative determination of Cr (III) and Cr (VI) in dyeing waste water of Dil Creek discharge to Izmit Gulf (Izmit-Kocaeli, Turkey) by ICP-AES

Wastewater pollution in industrial areas is one of the most important environmental problems. Heavy metal pollution, especially chromium pollution in wastewater sources from dyeing and tannery has affected the life on earth. This pollution can affect all ecosystems and human health directly or by food chain. Therefore, the determination of chromium in this study is of great importance. Dil Creek is located in the eastern Marmara region and discharges into the Izmit Gulf. This water source is used for irrigation in agriculture and as drinking water for animals. In this study, a rapid, sensitive and selective method for the speciative direct determination of Cr (III) and Cr (VI) in dyeing waste water samples collected from the nearest station to Izmit Gulf of Dil Creek in May 2006 by inductively coupled plasma-atomic emission spectrometry (ICP-AES) has been developed. An analysis of a given sample is completed in about 15 min for ICP-AES the method. As the result of the chromium analysis, the limit of quantification (LOQ) for the Cr (III), Cr (VI) and total Cr were founded as 0.0111 ± 0.0002 mg/l (RSD, 1.80%), 0.0592 ± 0.0010 mg/l (RSD, 1.70%) and 0.0703 ± 0.0020 mg/l (RSD, 2.84%) respectively. In addition, the general mathematical formula has been developed to calculate the concentration of Cr(III), which can be applied to any other metal species. The result of Cr (VI) analysis indicated that water quality of Creek was IV. class quality according to the inland water classification. In order to validate the applied method, recovery studies were performed.     

Determination of total Cr in wastewaters of Cr electroplating factories in the I.organize industry region (Kayseri, Turkey) by ICP-AES

The wastewater pollution in industrial areas is one of the most important environmental problems. Heavy metal pollution, especially chromium pollution in the wastewater sources from electroplating, dyeing, and tannery, has affected the life on earth. This pollution can affect on all ecosystems and human health directly or by food chain. Therefore, the determination of total chromium in this study is of great importance. In this study, accurate, rapid, sensitive, selective, simple, and low-cost technique for the direct determination of total Cr in wastewater samples collected from the some Cr electroplating factories in March 2008 by inductively coupled plasma-atomic emission spectrometry has been developed. The analysis of a given sample is completed in about 15 min by this technique applied. As the result of the chromium analysis, the limit of quantification for the total Cr were founded to be over the limit value (0.05 mg L^???1; WHO, EPA, TSE 266, and inland water quality classification) as 1,898.78 ± 0.34 mg/L at station 1 and 3,189.02 ± 0.56 mg/L at station 2. The found concentration of total Cr has been determined to be IV class quality water according to the inland water classification. In order to validate the applied method, recovery studies were performed.     

Determination of heavy metal pollution with environmental physicochemical parameters in waste water of Kocabas Stream (Biga, Canakkale, Turkey) by ICP-AES

Waste water pollution of industrial areas can answer for the serious consequences of one of the most important environmental threats to the future. In this study, inductively coupled plasma-atomic emission spectrometry method (ICP-AES) is proposed to determine heavy metals (Pb, Cu, Cd, Cr, Zn, Al, Fe, Ni, Co, Mn) and major elements (Ca, Mg) in waste water of Kocabas Stream. The concentration of metals in the waste water samples taken from 9 different stations (St.) in Biga-Kocabas Stream in November 2004 (autumn period) were determined after simple pretreatment of samples by the proposed ICP-AES method. An analysis of a given sample is completed in about 15 min for ICP-AES the method. The results of heavy metals concentrations in waste water were found between 0.00001–77.69610 mg l⁻¹ by the ICP-AES technique. The concentrations of Pb, Cd, Cu, Zn, Cr, Al, Fe, Mn, Ni, Co, Mg and Ca 0.00001 (St.3,6,7) – 0.0087 mg l⁻¹ (St.9), 0.00001 (St.4-7) – 0.0020 mg l⁻¹ (St.8), 0.00001 (St.1,3-7,9) – 0.0041 mg l⁻¹ (St.2), 0.0620 (St.2) – 0.2080 mg l⁻¹ (St.3), 0.0082 (St.6) – 0.2290 mg l⁻¹ (St.8), 0.3580 (St.2) – 1.7400 mg l⁻¹ (St.3), 0.2240 (St.1) – 0.6790 mg l⁻¹ (St.3), 0.0080 (St.1) – 1.5840 mg l⁻¹ (St.3), 0.0170 (St.3) – 0.0640 mg l⁻¹ (St.2), 0.0010 (St.1,4,5,8) – 0.0080 mg l⁻¹ (St.3), 5.0640 (St.9) – 5.2140 mg l⁻¹ (St.1) and 43.3600 (St.2) – 77.6961 mg l⁻¹ (St.9), respectively. Also we measured environmental physicochemical parameters such as temperature, salinity, specific conductivity, total dissolved solid (TDS), pH, oxidation and reduction potential (ORP), and dissolved oxygen (DO) in the waste water at sampling stations.     

Heavy metals pollution in a sewage treatment oxidation pond and the receiving stream of the Obafemi Awolowo University, Ile Ife, Nigeria

This work centered on a 1-year evaluation campaign of point source pollution from a sewage treatment oxidation pond and its receiving stream. Water samples were collected from the sewage treatment oxidation pond and the receiving stream during July 2002 and June 2003. Concentrations of heavy metals were determined using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) after a triple acid digestion of samples using open beaker method. Generally, the results showed high levels of toxic metals such as Cd, Pb, As, Al, Cr, Mn, Co, and Fe in the influent and effluent samples as well as in the receiving stream. The annual mean concentration of metals in the sewage samples ranged from 11.90 to 16.05, 64.96 to 88.27, 38.91 to 76.35, 17.46 to 24.45 mug/L for Cd, As, Pb, Co, and 4.31 to 8.77, 1.71 to 2.45, 0.46 to 0.74 and 13.82 to 20.47 mg/l for Al, Cr, Mn and Fe, respectively; while in the receiving stream, the concentrations were between 6.89 to 10.45, 35.50 to 59.26, 22.85 to 35.94, 11.33 to 18.83 mug/l for Cd, As, Pb, Co, and 1.99 to 3.49, 1.35 to 2.08, 0.21 to 0.48, and 8.93 to 14.15 mg/l for Al, Cr, Mn and Fe, respectively. The discharge of the effluent from the sewage pond into the receiving stream has therefore led to increase in the concentrations of some heavy metals downstream, thus impacting the receiving stream negatively and could pose a serious health hazard to aquatic ecosystems and humans particularly for rural dwellers and peasant farmers downstream that utilize the water from the receiving stream for various domestic and agricultural purposes untreated.     

Evaluation of chromium contamination in water, sediment and vegetation caused by the tannery of Jijel (Algeria): a case study

In order to evaluate the chromium (Cr) contamination due to the discharge of waste waters from the tannery of Jijel in the Mouttas river (Algeria), samples of water, sediment and vegetation (Agropyrum repens) were collected during a 6 month period in four stations located upstream (control) and downstream of the tannery. The total chromium was measured by atomic absorption spectrophotometry. Metal inputs were clearly related to effluent discharges from the tannery into the river. Although only traces of chromium were found in water samples upstream of the tannery, very high concentrations (up to 860 times higher) were detected downstream. The contamination was not limited to water of Mouttas River because a same difference in chromium concentrations was also found in sediments and plants Agropyrum repens that were sampled upstream and downstream of the tannery. This work showed that the treatment process used in the wastewater treatment plant of the tannery of Jijel is not able to remove the chromium detected in their influents. The occurrence and chromium levels detected in the aquatic environment represent a major problem concerning drinking water resources and environmental protection of water bodies.     

Environmental Monitoring and Impact Assessment of a Solid Waste Disposal Site

The objective of this study is an attempt to conduct an environmentalmonitoring and impact assessment of the On-Nooch solid waste disposal sitein Bangkok, Thailand. Four water and five air sampling stations (2 upwindand 3 downwind directions) were established at the site. Grab water samplesfrom leachate treatment plant and Khlong Song Hong, a nearby stream, werecollected during the rainy and dry seasons. Analytical results of the wastewater discharged by the leachate treatment plant, during dry season showedchemical oxygen demand: 618 mg/l; biochemical oxygen demand: 80 mg/l;suspended solid: 101 mg/l; Total Kjeldahl Nitrogen: 283 mg/l, which werestill higher than standard limit for effluents in Thailand. During the dryseason, results also showed widespread heavy metal pollution from leachate(chromium: 1.03 mg/l; manganese: 1.07 mg/l; mercury: 0.025 mg/l) and werehigher than the allowable level of heavy metals for the Industrial EffluentStandard in Thailand. The direct discharge of untreated leachate into inlandwater will cause considerable water pollution in the study area. Compositeair samples in this study area were collected during the rainy and dryseasons and were analyzed for methane (CH₄), carbon dioxide(CO₂), carbon monoxide (CO), sulphur dioxide(SO₂), nitrogen dioxide (NO₂) andsuspended particulate matter (SPM). The average concentration of SPM rangedbetween 0.1–0.36 mg/m³ for 24-hour average, dependingupon the season. The level of CH₄ and CO₂ inthe ambient air of the study area were found to be 3.48–65.71mg/m³ and 886-1758 mg/m³ respectively which weremuch higher than the normal concentration of CH₄ andCO₂ in the air (CH₄: 2.41 mg/m³;CO₂: 585 mg/m³). Hence, adverse health andenvironmental effects could be expected from water and air pollution.     

Distribution of heavy metals in surface water of Ranipet industrial area in Tamil Nadu, India

Ranipet industrial area is about 120 km from Chennai on Chennai-Bangalore highway and is a chronic polluted area identified by Central Pollution Control Board of India. It is one of the biggest exporting centers of tanned leather in India. The total number of industries located in and around Ranipet town are 240 tanneries along with ceramic, refractory, boiler auxiliaries plant, and chromium chemicals. Studies were carried out to find out the contamination of surface water bodies due to industrial effluents. The results reveal that the surface water in the area is highly contaminated showing very high concentrations of some of the heavy/toxic metals like Cadmium ranging from 0.2 to 401.4 μg/l (average of 51.1 μg/l), Chromium 2.4–1,308.6 (average of 247.2 μg/l), Copper 2.1–535.5 μg/l (average of 95.5 μg/l), Nickel 1.6–147.0 μg/l (average of 36.7 μg/l), Lead 6.4–2,034.4 μg/l (average of 467.8 μg/l) and Zinc 20.8–12,718.0 μg/l (average of 3,760.4 μg/l). The concentration levels of these metals are much above the permissible limits in surface water and are health hazards especially for the people working in the tannery industries. It was observed that the people in the area are seriously affected and suffering from occupational diseases such as asthma, chromium ulcers and skin diseases. Distribution of metals, their contents at different locations, and their effects on human health are discussed in this paper.     

Analysis of the environmental impact on a stream: is only tannery to blame?

The contribution of wastewater from a tannery industry to the pollution of a stream was investigated. The main parameters studied were biochemical oxygen demand, chemical oxygen demand, chromium, dissolved oxygen, fecal and total coliforms, nitrogen, oils and greases, pH, phosphorous, sulfides, suspended solids, turbidity, and volatile solids. Three sampling points were located: (1) at the discharge point of tannery wastewater, (2) 50 m upstream, and (3) 80 m downstream of discharge point. Also was investigated the pollution at the stream source.     

Trend in metals variation in Tasik Chini, Pahang, Peninsular Malaysia

Water from 15 sampling stations in Tasik Chini (Chini Lake), Peninsular Malaysia were sampled for 12 months from September 2004 until August 2005 and analyzed for 11 metals including iron (Fe), aluminum (Al), manganese (Mn), barium (Ba), zinc (Zn), lead (Pb), copper (Cu), cadmium (Cd), nickel (Ni), chromium (Cr) and cobalt (Co). Results showed that the mean (min-max) metal concentrations (in micrograms per liter) in Tasik Chini waters for the 12 months sampling based on 15 sampling stations (in descending order) for Fe, Al, Mn, Ba, Zn, Pb, Cu and Cd were 794.84 (309.33-1609.07), 194.53 (62.37-665.93), 29.16 (16.68-79.85), 22.07 (15.64-29.71), 5.12 (2.224-6.553), 2.36 (1.165-4.240), 0.832 (0.362-1.443) and 0.421 (0.254-0.696) respectively. Concentration for three metals i.e. Ni, Cr and Co were too low and not detected by the graphite furnace Atomic Absorption Spectrophotometry (AAS). Comparison with various water quality standards showed that the mean metals concentration in surface water of Tasik Chini were low and within the range of natural background except for Fe and Al. In general, metal concentrations in Tasik Chini water varied temporally and spatially. The main factors influencing these metal concentrations in the water were the raining season and mining activities. Stations located at Tanjung Jerangking and Melai areas were the most effected due to those factors.     

Influence of Mining Activities in the North of Potosi, Bolivia on the Water Quality of the Chayanta River, and its Consequences

Mining activity in the North of Potosi (Siglo XX mine, Ingenio Catavi-Siglo XX, Pucro mine and Colquechaca mine) produces minewater containing high concentrations of heavy metals such as As (0.02-34 mg/l), Cd (45-11,600 microg/l), Cu (0.35-32 mg/l), Fe (42-1,010 mg/l), Pb(33-3,130 microg/l), Ni(20-4,320 microg/l), and Zn (1.1-485 mg/l), that exceed considerably the limit values. The rivers in the North of Potosi (Katiri and Pongoma) that do not receive minewater contain clear water with rather low heavy metal concentrations. These rivers and also other rivers contaminated with minewater, are tributaries of the Chayanta River that transports water with a high concentration of heavy metals such as As (6-24 microg/l), Cd (260-2,620 microg/l), Cu (205-812 microg/l), Pb(10-21 microg/l) and Ni(110-332 microg/l). These elements result from mining activity, as indicated by a comparison with rivers not contaminated by minewater discharges. Water of the Chayanta River, used all year long by the population of Quila Quila, (a village situated at about 75 km from the mining centers), for the irrigation of crops such as potato, maize and broad bean, contains heavy metal concentrations exceeding for several elements the guidelines for irrigation. As drinking water the population of Quila Quila consumes spring water with a generally acceptable heavy metal concentration, as well as infiltrated water of Chayanta River (which is also used in animal drinking troughs) with a high concentration of Cd (23-63 microg/l), exceeding the limit value for drinking water. The metal concentration is significantly lower in the infiltrated water than in the water of Chayanta River. Some technological solutions are suggested to improve the quality of the water used. Surveys carried out on inhabitants of the region, showed that many people present health problems, probably to be attributed to the bad quality of the water they consume and use for irrigation.     

Bioremediation of tannery effluent by Cr- and salt-tolerant bacterial strains

Microorganisms have great potential to control environmental pollution, particularly industrial sources of water pollution. Currently, leather industry is regarded as the most polluting and suffering from negative impacts due to the pollution it adds to the environment. Chromium, one of the hazardous pollutants discharged from tanneries, is highly toxic and carcinogenic in nature. Effective treatment of tannery effluent is a dire need of the era as a part of environmental management. Among all the wastewater treatment technologies, bioremediation is the most effective and environment-friendly tool to manage the water pollution. The present study evaluated the potential of 11 previously isolated bacterial strains, tolerant to high concentrations of salts and Cr for the bioremediation of tannery effluent. Among all the tested strains, Enterobacter sp. HU38, Microbacterium arborescens HU33, and Pantoea stewartii ASI11 were found most effective in reducing biological oxygen demand (BOD), chemical oxygen demand (COD), total dissolved solids (TDS), total suspended solids (TSS), and chromium (Cr) 70, 63, 57, 87, and 54%, respectively, of tannery effluent and proliferated well under highly toxic conditions, at 9 days of incubation. The pollutant removal efficacy of these bacterial strains can be improved by extending the incubation period or by increasing the amount of inoculum.     

Assessment of chromium efficacy on germination,root elongation,and coleoptile growth of wheat (Triticum aestivum L.) at different growth periods

The tannery effluents contain a high concentration of chromium (Cr). It drastically reduces the crop yield when used for irrigation purpose. A huge volume of tannery effluents is available as irrigation for crop production. It is negatively affecting germination as well as yield of the crop. The wheat seeds were exposed to five different concentrations of Cr (0, 20, 40, 80, and 100 ppm). In Petri plates, 100 seeds were placed and the germination percent was recorded after 72 hour (h). Root elongation and coleoptile growth were measured at 72, 120, 168, and 240 h. Results showed that the germination percent of the test crop decreased with increasing Cr levels. It decreased by 6, 14, 30, and 37 % under the Cr concentration of 20, 40, 80, and 100 ppm, respectively. The root elongation was more sensitive than the coleoptile growth. The negative correlation was found between Cr levels and root elongation as well as coleoptile growth. These growth parameters were significantly affected up to 80 ppm of Cr level. The wheat growers using tannery effluent as irrigation should be well treated prior to application.     

Characterization of heavy metals in water and sediments in Taihu Lake, China

To explore a comprehensive status of heavy metals in the Taihu Lake, which is one of the most important waters in China, water and sediment samples were taken throughout the lake during April to May of 2010, and metal elements (Cu, Cd, Cr, Ni, Pb, Sn, Sb, Zn, Mn) were analyzed in the water column, interstitial water and sediment. Relevant standards were used to assess the sediment and water quality. Results show that, in the lake water column, the average concentration of all metals ranged from 0.047 μg/l (Cd) to 8.778 μg/l (Zn). The concentration in the river water was usually higher than in the lake water for many metals. In the interstitial water Mn was significantly higher than that in water column, and other metals had no significant difference between the two media. In the surface sediment, average metal content ranged from 1.325 mg/kg (Cd) to 798.2 mg/kg (Mn). Spatially, contents of many metals were higher in Zhushan Bay than in other lake areas, and there existed a clear content gradient from the river to the lake for both water and sediment. On the sediment profiles, many metals presented an increasing trend from the depth of 15-20 cm to the top, which is indicative of the impact of increasingly intensive human activities from that period. Quality assessment indicates that metals in water phase are generally safe compared with USEPA "National Recommended Water Quality Criteria," with the exception of Mn in the interstitial water and Sb in the river water. Whereas the sediment is widely contaminated with metals to some extent compared with the "Consensus-Based Sediment Quality Guidelines," and Cu, Cr, and Ni are more likely to raise ecological risks. This work could be a basis for the ongoing China's criteria strategy.     

The duckweed Wolffia globosa as an indicator of heavy metal pollution: Sensitivity to Cr and Cd

The potential of Wolffia globosa, a profusely occurring rootless duckweed, was evaluated as an indicator of metal pollution in the water bodies. Plants of W. globosa were cultured in 3% Hoagland's nutrient medium which was supplemented with 0.05, 0.1, 1.0 and 2.0 mg/L of Cr and Cd. Plants showed substantial accumulation of both the metals at lowest concentrations. For example, at 0.05 ppm, the concentration factor (Cf) value for Cr was significantly higher (5616) than for Cd (1018). A high level of tolerance was shown by the plants to both Cr and Cd. The results show that the plants are sensitive to the variations in metal concentration and are capable of high metal enrichment at very low ambient concentration of the metals. This information may be useful for detecting metals in the water.NBRI Research Publication No. 401 (N.S.)     

Statistical source identification of metals in groundwater exposed to industrial contamination

Levels of selected metals Na, Ca, Mg, K, Fe, Mn, Cr, Co, Ni, Cd, Pb and Mn were estimated by flame atomic absorption spectrophotometry in groundwater samples from Kasur, a significant industrial city of Pakistan. Salient mean concentration levels were recorded for: Na (211 mg/l), Ca (187 mg/l), Mg (122 mg/l), K (87.7 mg/l), Fe (2.57 mg/l) and Cr (2.12 mg/l). Overall, the decreasing metal concentration order was: Na > Ca > Mg > K > Fe > Cr > Zn > Co > Pb > Mn > Ni > Cd. Significantly positive correlations were found between Na–Cr (r = 0.553), Na–Mn (r = 0.543), Mg–Fe (r = 0.519), Mg–Cr (r = 0.535), Pb–K (r = 0.506) and Pb–Ni (r = 0.611). Principal Component Analysis and Cluster Analysis identified tannery effluents as the main source of metal contamination of the groundwater. The present metal data showed that Cr, Pb and Fe levels were several times higher than those recommended for water quality by WHO, US-EPA, EU and Japan. The elevated levels of Cr, recorded as 21–42 fold higher compared with the recommended quality values, were believed to originate from the tanning industry of Kasur.     

Estimation of uranium and radon concentration in some drinking water samples of Upper Siwaliks, India

Uranium and radon concentration was assessed in water samples taken from hand pumps, natural sources and wells collected from some areas of Upper Siwaliks, Northern India. Fission track registration technique was used to estimate the uranium content of water samples. The uranium concentration in water samples was found to vary from 1.08 +/- 0.03 to 19.68 +/- 0.12 microg l(-1). These values were compared with safe limit values recommended for drinking water. Most of the water samples were found to have uranium concentration below the safe limit of 15 microg l(-1) (WHO, World Health Organization, Guidelines for drinking-water quality (3rd ed.). Geneva, Switzerland: WHO, 2004). The radon estimation in these water samples was made using alpha-scintillometry to study its correlation with uranium. The radon concentration in these samples was found to vary from 0.87 +/- 0.29 to 32.10 +/- 1.79 Bq l(-1). The recorded values of radon concentration were within the recommended safe limit of 4 to 40 Bq l(-1) (UNSCEAR, United Nations Scientific Committee on the Effects of Atomic Radiations, Sources and effects of ionizing radiation. New York: United Nations, 1993). No direct correlation was found between uranium concentration and radon concentration in water samples belonging to Upper Siwaliks. The values of uranium and radon concentration in water were compared with that from the adjoining areas of Punjab state, India.     

Pollution and variation of stream nitrate in a protected high-mountain watershed of Central Taiwan: evidence from nitrate concentration and nitrogen and oxygen isotope compositions

This study analyzed the concentration and stable nitrogen (δ(15)N) and oxygen (δ(18)O) isotopic compositions of water NO (3) (-) , as well as NO (3) (-) concentration and δ(15)N values of soils and manure-sourced fertilizers to assess pollution and variation in stream nitrate at the watershed of the Chi-Chia-Wan Stream (CCWS), a protected high-mountain stream in Central Taiwan. Results indicate a gully (G1) that contributes significantly high NO (3) (-) concentration water (up to 122 mg/L) to trunk water as the major pollution source of CCWS. The high NO (3) (-) concentration gully water has a close relationship with manure-sourced fertilizer with both having compatible enriched δ(15)N values. Results also indicate that water mixing over isotopic fractionation processes such as denitrification or assimilation is the major process accounting for variations in concentrations and isotopic values for stream NO (3) (-) . Incorporation of gully/tributary water of high NO (3) (-) concentration increases both the concentration and isotopic values of trunk water and vice versa for the incorporation of low NO (3) (-) concentration tributary water. Despite G1 contributing high NO (3) (-) concentration water to the trunk water of CCWS, the concentration of the trunk water is only slightly elevated and is still lower than the required water quality standard due to much lower drainage of the gully water compared to trunk water's runoff. In addition to gully or tributary water and rainwater, NO (3) (-) derived from soil is another important contributor to trunk water. The NO (3) (-) contribution of soil to trunk water is greater in summer than in winter. Additionally, NO (3) (-) concentrations in soil from ex-cultivated land are significantly lower than that in cultivated land. This means that NO (3) (-) contribution from ex-cultivated land soil to trunk water is small and demonstrates that the land-recovery plan that has been underway in the studied watershed for sometime is effective.     

Surface water quality assessment of the Vatinsky Egan River catchment, West Siberia

Stream water chemistry were analyzed across Vatinsky Egan River Catchment (West Siberia). The objective of the study is to reveal the spatial and seasonal variations of the water quality and to assess the anthropogenic chemical inputs into the river system. Stream chemistry were monitored in 24 sampling sites for a period extended from January 2002 to December 2005. Spatial distribution of constituents in the Vatinsky Egan River basin indicated pollution from non-point sources associated with oil development. Data revealed that ion concentrations of river waters are usually negatively correlated with stream discharge. The major spatial variations of the hydrochemistry are related to the salinity. Chloride exhibited wide and high concentration range. A comparison with another rivers of West Siberia reveals that Vatinsky Egan River is the most saline and regional impacts further out in the watershed. The salinity of the river water increases substantially as it crosses Samotlor oil field. Many Cl(-) concentrations in the middle and lower parts of the catchment exceed the world average river values by one or more orders of magnitude. For 38% of sampling events, total petroleum hydrocarbons (TPH) concentrations were above the recommended water quality standards.     

Chromium redox speciation in natural waters

Dissolved hexavalent chromium concentrations were determined in river, estuarine and coastal waters of the Humber catchment in north-east England. Samples were collected, filtered, extracted on site and after storage for up to eight days. Hexavalent chromium concentrations did not change by more than 0.05 microg l(-1) (not significant, p = 0.05) over this period. Total chromium concentrations in the catchment were less than 1.0 microg l(-1). This is low in relation to the proposed Environmental Quality Standard. Hexavalent chromium accounted for between 27% and 100% of the total dissolved concentration, with an average of approximately 50%. The proportion of Cr(III) and Cr(VI) in the rivers and estuary were of the same range as previously measured in 1993. The addition of Cr(III) and Cr(VI) to fresh and saline water samples illustrates the complexity of the factors controlling chromium speciation in natural waters. The presence of oxidisable organic matter and the stabilising role of complexing organic ligands are proposed as the main controlling influences of redox speciation in filtered samples.     

Inventory compilation and distribution of heavy metals in wastewater from small-scale industrial areas of Delhi, India

Delhi has the highest cluster of small-scale industries (SSI) in India. There are generally less stringent rules for the treatment of waste in SSI due to less waste generation within each individual industry. This results in SSI disposing of their wastewater untreated into drains and subsequently into the river Yamuna, which is a major source of potable water in Delhi, thus posing a potential health and environmental risk to the people living in Delhi and downstream. To study the quantity, quality and distribution of heavy metals in liquid waste from industrial areas, wastewater, suspended materials and bed sediments were collected from industrial areas and from the river Yamuna in Delhi. This study has also focused on the efficiency of production processes in small-scale industries in India. Heavy metals such as Fe, Mn, Cu, Zn, Ni, Cr, Cd, Co and Pb were detected using a GBC 902 atomic absorption spectrometer. The concentration of heavy metals observed was as follows: Fe 2-212, Mn 0.3-39, Cu 0.2-20, Zn 0.2-5, Ni 0.6-6, Cr 0.2-53, Cd 0.08-0.2, Co 0.013-0.55, Pb 0.3-0.7 mg L(-1) in wastewater; Fe 5842-78 000, Mn 585-10 889, Cu 206-7201, Zn 406-9000, Ni 22-3621, Cr 178-10 533, Co 17-114, Cd 13-141, Pb 67-50 171 mg kg(-1) in suspended material; and Fe 3000-84000, Mn 479-1230, Cu 378-8127, Zn 647-4010, Ni 164-1582, Cr 139-3281, Co 20-54, Cd 37-65, Pb 228-293 mg kg(-1) in bed residues. This indicates that SSI could be one of the point sources of metals pollution in the river system.