Lead levels in teeth of an urban Indian population

The lead content of teeth of Bombay residents has been determined using differential pulse anodic stripping voltammetry. The median tooth lead concentrations for adults and children in Bombay are estimated to be 8.31 and 3.01 micrograms/g of tooth, respectively. The data indicate that the lead concentration of a tooth increases with the age of the donor. For children the tooth lead content varies with the type of tooth. Further, children living in industrial areas have a higher tooth lead content than children living in the cleaner suburbs of Greater Bombay.     

Application of land use regression to regulatory air quality data in Japan

A land use regression (LUR) model has been used successfully for predicting traffic-related pollutants, although its application has been limited to Europe and North America. Therefore, we modeled traffic-related pollutants by LUR then examined whether LUR models could be constructed using a regulatory monitoring network in Shizuoka, Japan. We used the annual-mean nitrogen dioxide (NO₂) and suspended particulate matter (SPM) concentrations between April 2000 and March 2006 in the study area. SPM accounts for particulate matter with an aerodynamic diameter less than 8 μm (PM₈). Geographic variables that are considered to predict traffic-related pollutants were classified into four groups: road type, traffic intensity, land use, and physical component. Using geographical variables, we then constructed a model to predict the monitored levels of NO₂ and SPM. The mean concentrations of NO₂ and SPM were 35.75 μg/m³ (standard deviation of 11.28) and 28.67 μg/m³ (standard deviation of 4.73), respectively. The final regression model for the NO₂ concentration included five independent variables. R² for the NO₂ model was 0.54. On the other hand, the regression model for the SPM concentration included only one independent variable. R² for the SPM model was quite low (R² = 0.11). The present study showed that even if we used regulatory monitoring air quality data, we could estimate NO₂ moderately well. This result could encourage the wide use of LUR models in Asian countries.     

Developing environment-specific water quality guidelines for suspended particulate matter

It is generally well recognised that suspended particulate matter (SPM), from nano-scale particles to sand-sized sediments, can cause serious degradation of aquatic ecosystems. However, at present there is a poor understanding of the SPM conditions that water quality managers should aim to achieve in contrasting environments in order to support good ecological status. In this article, we analyse long-term SPM data collected from a wide range of reference-condition temperate environments in the UK (638 stream/river sites comprising 42 different ecosystem-types). One-way analysis of variance reveals that there is a statistically significant difference (p < 0.001) between the background SPM concentrations observed in contrasting ecosystems that are in reference condition (minimal anthropogenic disturbance). One of the 42 ecosystems studied had mean background concentrations of SPM in excess of the current European Union (EU) water quality guideline, despite being in reference condition. The implications of this finding are that the EU’s current blanket water quality guideline (25 mg L⁻¹ for all environments) is inappropriate for this specific ecosystem-type which will be non-compliant with the guideline regardless of the intensity of land-use. The other 41 ecosystems studied had mean concentrations below the current EU water quality guideline. However, this does not necessarily mean that the guideline is appropriate for these ecosystems, as previous research has demonstrated that detrimental impacts can be experienced by some freshwater organisms, of all trophic levels, when exposed to concentrations below 25 mg L⁻¹. Therefore, it is suggested here that it is likely that some ecosystems, particularly those with mean concentrations in the 0.00-5.99 mg L⁻¹ range, require much lower guideline values in order to be effectively protected. We propose a model for predicting environment-specific water quality guidelines for SPM. In order to develop this model, the 638 reference condition sites were first classified into one of five mean background SPM ranges (0.00-5.99, 6.00-11.99, 12.00-17.99, 18.00-23.99 and >24.00 mg L⁻¹). Stepwise Multiple Discriminant Analysis (MDA) of these ranges showed that a site’s SPM range can be predicted as a function of: mean annual air temperature, mean annual precipitation, mean altitude of upstream catchment, distance from source, slope to source, channel width and depth, the percentage of catchment area comprised of clay, chalk, and hard rock solid geology, and the percentage of the catchment area comprised of blown sand as the surface (drift) material. The MDA technique, with cross-validation (Wilks-Lambda 0.358, p 0.000), can predict the correct or the next closest SPM range of a site in 90% of cases. This technique can also predict SPM range membership in a probabilistic manner, allowing for an estimate of uncertainty to be made in the allocation of a site to an environment-specific SPM range.     

Progress in the isolation and characterization of non-volatile mutagens in a drinking-water

Using the Ames Salmonella mutagenicity test (TA98, without S9), non-volatile mutagenic fractions were obtained by applying a separation scheme on XAD extracts of Pretoria drinking-water. The fractionations obtained were based on solubility, volatility, permeation and adsorption and the mutagenicity yield of each step was estimated. One mutagenic fractionconsisted of humic like material, possibly together with polar polynuclear aromatic hydrocarbons.     

Geochemical signals and source contributions to heavy metal (Cd, Zn, Pb, Cu) fluxes into the Gironde Estuary via its major tributaries

Daily measurements of water discharges and suspended particulate matter (SPM) concentrations and monthly sampling for trace element analyses (Cd, Zn, Pb and Cu) were conducted from 1999 to 2002 on the Garonne, Dordogne and Isle Rivers, the three main tributaries of the Gironde Estuary, France. Dissolved and particulate Cd, Zn, Pb and Cu concentrations in the Isle River were generally higher than those in the Garonne River, despite the known historical polymetallic pollution affecting the Lot-Garonne River system. Even if the relatively high dissolved metal concentrations in the Isle River may be of importance for the local ecosystem, metal inputs into the estuarine and coastal zones are mainly controlled by fluvial transport via the Garonne River. Characteristic element concentration ratios (e.g., Zn/Pb) in SPM and stream sediments from the Dordogne and Isle Rivers suggest two different metal source areas with distinct geochemical signals. Low Zn/Pb ratios (<8) and low Cu/Pb ratios (<0.8) have been attributed to upstream source zones in the Massif Central, featuring various ore deposits and mining areas. High Zn/Pb ratios were assigned to downstream sources (e.g., vineyards), partly explaining high Zn and Cu concentrations and high Cu/Pb ratios (>0.8) in SPM. Although SPM derived from the upstream parts of the studied watersheds may greatly contribute to the observed fluvial metal transport (up to approximately 80% for Pb), the results suggest that intensive agriculture also considerably influences gross metal (e.g., Zn, Cu) fluxes into the Gironde Estuary. Relative contributions of upstream and downstream source zones may vary from one year to another reflecting hydrological variations and/or reservoir management. Monitoring fluxes and identifying distinct geochemical signals from source areas in heterogeneous watersheds may greatly improve understanding of contaminant transport to the coast.     

Comparative assessment of genotoxicity of mineral water packed in polyethylene terephthalate (PET) and glass bottles

The potential migration of genotoxic compounds into mineral water stored in polyethylene terephthalate (PET) bottles was evaluated by an integrated chemical/biological approach using short-term toxicity/genotoxicity tests and chemical analysis. Six commercial brands of still and carbonated mineral water bottled in PET and in glass were stored at 40 °C for 10 days in a stove according to the standard EEC total migration test (82/711/EEC), or at room temperature in the dark. After treatment, the samples were analysed using gas-chromatography/mass spectrometry (GC/MS) to detect volatile and non-volatile compounds, the Microtox^® test to evaluate potential toxicity of the samples, and three mutagenicity tests - Tradescantia and Allium cepa micronucleus tests and the Comet assay on human leukocytes - to detect their genotoxic activity.GC/MS analysis did not detect phthalates or acetaldehyde in the water samples. The Microtox^® test found no toxic effects. Mutagenicity tests detected genotoxic properties of some samples in both PET and glass bottles. Statistical analyses showed a positive association between mineral content and mutagenicity (micronuclei in A. cepa and DNA damage in human leukocytes). No clear effect of treatment and PET bottle was found. These results suggest the absence of toxic compounds migrating from PET regardless of time and conditions of storage. In conclusion, bottle material and stove treatment were not associated with the genotoxic properties of the water; the genotoxic effects detected in bottled water may be related to the characteristics of the water (minerals and CO₂ content).     

The influence of contrasting suspended particulate matter transport regimes on the bias and precision of flux estimates

A large database (507 station-years) of daily suspended particulate matter (SPM) concentration and discharge data from 36 stations on river basins ranging from 600 km(2) to 600,000 km(2) in size (USA and Europe) was collected to assess the effects of SPM transport regime on bias and imprecision of flux estimates when using infrequent surveys and the discharge-weighted mean concentration method. By extracting individual SPM concentrations and corresponding discharge values from the database, sampling frequencies from 12 to 200 per year were simulated using Monte Carlo techniques. The resulting estimates of yearly SPM fluxes were compared to reference fluxes derived from the complete database. For each station and given frequency, bias was measured by the median of relative errors between estimated and reference fluxes, and imprecision by the difference between the upper and lower deciles of relative errors. Results show that the SPM transport regime of rivers affects the bias and imprecision of fluxes estimated by the discharge-weighted mean concentration method for given sampling frequencies (e.g. weekly, bimonthly, monthly). The percentage of annual SPM flux discharged in 2% of time (Ms(2)) is a robust indicator of SPM transport regime directly related to bias and imprecision. These errors are linked to the Ms(2) indicator for various sampling frequencies within a specific nomograph. For instance, based on a deviation of simulated flux estimates from reference fluxes lower than +/-20% and a bias lower than 1% or 2%, the required sampling intervals are less than 3 days for rivers with Ms(2) greater than 40% (basin size<10,000 km(2)), between 3 and 5 days for rivers with Ms(2) between 30 and 40% (basin size between 10,000 and 50,000 km(2)), between 5 and 12 days for Ms(2) from 20% to 30% (basin size between 50,000 and 200,000 km(2)), 12-20 days for Ms(2) in the 15-20% range (basin size between 200,000 and 500,000 km(2)).     

Microscale fluctuation assay coupled with Sep-PakR concentration as a rapid and sensitive method for screening mutagens in drinking water

A sensitive short-term mutagenicity test, the microscale fluctuation test has been coupled with a concentration method based on adsorption on Sep-Pak^R C₁₈ cartridges as a method for screening drinking water mutagens. Comparison with XAD-2 concentration method showed that Sep-Pak adsorbed 5 times higher quantity of organics but was slightly less efficient for adsorbing TOX.Microscale fluctuation test was found to be more sensitive than Ames test by testing known direct-acting mutagens and concentrates of drinking water. Samples derived from conventional treatment including chlorination from eight surface water supplies in Norway were concentrated at pH 2 by adsorption on the disposable columns. The adsorbates were tested at different doses by the microscale fluctuation assay. The mutagenic properties of drinking water samples were also related to total organic carbon (TOC), total organic halogen (TOX) and trihalomethanes (THM) concentrations. Dose-related mutagenic responses were found for all the samples with S. typhimurium TA 100 and TA98 strains without metabolic activation. Good relationship was found between mutagenicity data and TOX and THM results. The method showed to be simple, rapid and suitable for routine screening of mutagens in drinking water.     

Levels of lead,cadmium, zinc and copper in the blood of an urban population

Levels of lead, cadmium, zinc and copper were measured in the blood of normal children and adults of Greater Bombay, India using differential pulse anodic stripping voltammetry. The median concentrations of Pb, Cd, Zn and Cu in the whole blood of children and adults were 11.54, 0.21, 484.2 and 86.2 μg dl⁻¹, respectively. The blood lead concentration showed an increase with age. Children living in industrial zones with high vehicular traffic have significantly higher blood lead concentrations than their counterparts living in the cleaner suburban parts of the city. The mean levels of Pb, Cd, Zn and Cu in blood of Bombay children and adults are compared with those from other countries.     

Characterisation of urban catchment suspended particulate matter (Auckland region, New Zealand); a comparison with non-urban SPM

Suspended particulate matter (SPM) is an important transport agent for metal contaminants in streams, particularly during high flow periods such as storm events. For highly contaminated urban catchments in the greater Auckland (New Zealand) area, trace metal partitioning between the dissolved phase and SPM was determined, and SPM characterised in terms of its Si, Al, Fe, Mn, Zn, Cu, Pb, TOC, TON and PO(4) concentrations, as well as particle size, abundance, type and surface area. This data was compared to similar data from representative non-urban catchments in the Auckland region, the Kaipara River and Waikato River catchments, to identify any significant differences in the SPM and its potential trace metal adsorption capacity. Trace metal partitioning was assessed by way of a distribution coefficient: K(D)=[Me(SPM)]/[Me(DISS)]. Auckland urban SPM comprises quartz, feldspars and clay minerals, with Fe-oxides and minor Mn-oxides. No particles of anthropogenic origin, other than glass shards, were observed. No change in urban SPM particle size or SSA was observed with seasonal change in temperature, but the nature of the SPM was observed to change with flow regime. The abundance of finer particles, SSA and Al content of the SPM increased under moderate flow conditions; however, Si/Al ratios remained constant, confirming the importance of aluminosilicate detrital minerals in surface run-off. The SPM Fe content was observed to decrease with increased flow and was attributed to dilution of SPM Fe-oxide of groundwater origin. The Kaipara River SPM was found to be mineralogically, chemically and biologically similar to the urban SPM. However, major differences between urban catchment SPM and SPM from the much larger (non-urban) Waikato River were observed, and attributed to a higher abundance of diatoms. The Fe content of the Waikato River SPM was consistently lower (<5%), and the Si/Al ratio and Mn content was higher. Such differences observed between urban and non-urban SPM did not appear to affect the partitioning of Zn and Cu; however, Pb in the Kaipara and Waikato Rivers was found to be more associated with the dissolved phase. This is likely to reflect higher particulate Pb inputs to urban systems.     

The particulate Be/Pbxs and Th/Pbxs activity ratios as tracers for tidal-to-seasonal particle dynamics in the Gironde estuary (France): Implications for the budget of particle-associated contaminants

The short-lived natural radionuclides ⁷Be (T_1/2 = 53 days), ²³⁴Th_xs (T_1/2 = 24.1 days) and ²¹⁰Pb_xs (T_1/2 = 22.3 years), i.e. ²³⁴Th and ²¹⁰Pb in excesses of that supported within particles by the decay of their parent isotopes, were analysed in suspended particulate matter (SPM) to study the particle dynamics in the Gironde fluvial estuarine system (France), strongly impacted by heavy metal pollution. From surveys of this land-ocean interface in 2006 and 2007, we established a times series of these radioisotopes and of their activity ratios (⁷Be/²¹⁰Pb_xs and ²³⁴Th/²¹⁰Pb_xs ARs) in particles sampled under different hydrological conditions.The particulate ⁷Be/²¹⁰Pb_xs AR varies along the fluvial estuarine system mainly due to variations in ⁷Be activities, controlled by riverine, oceanic and atmospheric inputs and by resuspension of old ⁷Be-deficient sediments. These processes vary with river discharge, tidal cycle and season. Therefore, seasonal particle transport processes can be described using variations of the SPM ⁷Be/²¹⁰Pb_xs ARs.During high river discharge, the SPM ⁷Be/²¹⁰Pb_x ARs decrease from river to the ocean. The turbidity maximum zone (TMZ) is dispersed and the particles, and the associated contaminants, are rapidly transported from river to coastal waters, without significant retention within the TMZ. During low river discharge, the TMZ intrudes into the fluvial estuary, and the lowest ⁷Be/²¹⁰Pb_x ARs are observed there due to resuspension of ⁷Be-deficient sediments. Away from the TMZ, from the middle to lower estuary, SPM ⁷Be/²¹⁰Pb_x ARs increase, indicating that the particles have been recently tagged with ⁷Be. We explain this trend as being caused by marine input of dissolved radionuclides, as traced by SPM ²³⁴Th/²¹⁰Pb_xs ARs, followed by scavenging in the estuary. This result indicates that particle transport models based on ⁷Be and trace-metal budgets must consider oceanic dissolved inputs as an additional source of ⁷Be and, possibly, of contaminants to estuaries.     

The mutagenicity of ambient air particles from local traffic and distant sources during episodes with moderate photochemical air pollution

The mutagenicity of ambient air particles in the Ames test was investigated during episodes with moderate photochemical air pollution. The particles were sampled on 11 occasions, each consisting of at least four sampling periods of 3 h during the day and one period of not more than 12 h during the following night. During the last 4 days, sampling was carried out at three locations, which allowed observation of the contribution from local sources (traffic in a town and on a motorway) to the mutagenicity. The local sources caused an increase in the indirect (S9-dependent) mutagenicity; the direct mutagenicity was not significantly affected. The particles sampled upwind dominated the mutagenicity in the area; in contrast to the locally emitted particles, their effects decreased in the presence of S9 fraction. This difference may indicate a qualitative change in the mutagenicity during the residence of the particles in the air. The direct mutagenicity depended very much on bacterial nitro reduction, as was demonstrated by using strain TA98NR; the effect in this strain was substantially increased in the presence of S9 fraction. This increase shows that, in the presence of S9 fraction, the effect in the TA98 strain is to a great extent the result of indirect mutagens and not only the result of partially deactivated direct mutagens. No typical quantitative or qualitative diurnal variation could be demonstrated. This is most probably due to the overwhelming influence of long-range transported mutagens which had already undergone maximum conversion during their residence in the air. Multivariate analysis of the effects and concentrations of gaseous pollutants indicated a rather strong link between mutagenicity and SO2, which confirms the important contribution of long-range transported mutagenicity.     

River sediments provide a link between catchment pressures and ecological status in a mixed land use Scottish River system

This study evaluates water quality, suspended and bed sediment, ecological and catchment land use data for 13 catchments of the mixed land use River Dee, NE Scotland, where pollution point sources are limited. Samples were collected at key times of biological activity (early and late summers). Mean river water concentrations were smaller in main stem and upland sites and greater in tributaries where agricultural pressures were greater and were 2-41 microgPO(4)-Pl(-1), 8-58 microg total dissolved Pl(-1) and 1-6 mg l(-1) of suspended particulate matter (SPM). SPM was 7-372 times enriched in biologically available P (BAP; determined using an FeO paper strip method) and 2-122 times in organic C relative to bed sediments. Ratios in river water concentrations of BAP attributed to the SPM (0.1-1.0 microgPl(-1)) to PO(4)-P had the greatest range at baseflow (0.01-0.80) with larger values for low land use intensity catchments. During May chlorophyll a concentrations were related to SPM BAP (p<0.001), but later in summer to PO(4)-P, and there was a corresponding change in the organic composition of SPM observed by IR spectroscopy. SPM concentrations and SPM BAP were better related to intensive grassland land use (p<0.001) than was PO(4)-P concentration (p<0.01) and also predicted abundances of filter feeding macroinvertebrates (p<0.001). Within this river system SPM quantity and composition proved to be an indicator of river biogeochemical functioning and requires further investigation as a potentially sensitive monitoring tool and to increase our understanding of chemical ecological links.     

Extraction parameters in the mutagenicity assay of soil samples

This study aimed at investigating parameters of chemical extraction associated with the detection of mutagenicity in soil samples extracts. In order to evaluate the extraction efficiency of inorganic mutagens, besides the chemical analysis of metals, the Salmonella/microsome assay was performed in the preincubation and microsuspension procedures, using two solvents, and using two extraction methodologies. The efficiency of two organic compound extraction methods was compared by qualitative analysis using CG/MS in Scan mode. The results of the analysis of inorganic extracts correlated with the mutagenicity results. Mutagenic effects were detected only in the acidic extracts of soil that were shaken, in the microsuspension assay, both in the presence and absence of metabolic activation. The other conditions tested demonstrated higher cytotoxicity and negative mutagenic effects. As to the organic compounds, Accelerated Solvent Extraction (ASE) proved more effective than extraction using ultrasound (sonication). This study will help the implementation of extraction parameters to evaluate the presence of mutagenic substances in soil samples, both of inorganic and organic origins, suggesting the implementation of acidic extraction for the assessment of inorganic mutagenicity from soil samples and confirming the efficiency of ASE extraction for the assessment of organic compounds.     

Studies of blood lead levels in children by proton-induced X-ray emission (PIXE)

Blood lead levels of children admitted to Sion Hospital, Bombay (India), from the adjoining Dharavi slum areas have been determined by proton-induced X-ray emission (PIXE). Blood samples were collected from 36 children with suspected lead poisoning and from 20 control children. The analysis showed that the lead concentration of the patients varied from 0.1 to 6.0 micrograms ml-1. In addition to lead, K, Ca, Fe, Cu, Zn, Se, Br and Rb were also detected simultaneously, of which the concentrations of Fe, Cu, Zn, Se, Rb and Pb were determined. The high blood lead levels of the children from this area may be ascribed to environmental pollution due to heavy vehicular traffic and industrial sources.     

Trace elements in size separated atmospheric particulates at trombay,Bombay, India

The results of measurements for the trace element composition of size-separated aerosols collected with an eight-stage impactor at Trombay, Bombay, India and analysed by instrumental neutron activation analysis are presented. The mass size functions and the sources of the elements analysed are discussed. The elements Sb and Hg are mainly derived from industrial emissions; over 40% of the concentration of these elements have a mean particle diameter (M.P.D.) of 1 μm for which alveolar deposition is higher than that in other parts of the lung. For Zn the abundance of particles <1 μm MMAD is high, while it is only ca. 15% or less for elements such as Fe, Sc, Co and Cr which are principally derived from soil debris.     

Blood lead levels in children after phase-out of leaded gasoline in Bombay, India

The objective of this study was to test for reduction in pediatric blood lead levels (BLLs) in Bombay, India, by comparing BLLs collected in 2002 (after use of leaded gasoline was phased out in Bombay) to those collected in a study conducted by the George Foundation in 1997 (when leaded gasoline was still used in Bombay). We analyzed BLL in a total of 754 children under 12 years of age in two separate sampling campaigns (276 from December 2002 to January 2003 [non-monsoon season]; 478 in June to August 2003 [monsoon season]). BLL was measured using an ESA Lead Care Portable Analyzer. We also measured lead in PM10 samples collected in the study region. These data were compared with a study done by the George Foundation in 1997 before the phase out of leaded gasoline. The George Foundation study reported that 61.8% of the 291 children tested in Bombay had elevated blood lead levels (BLL>or=10 microg/dL). In the present study, 33.2% of the 754 tested children had elevated blood lead levels. The average BLL for the current study population (Geometric Mean=8.36 microg/dL, SD=5.23 microg/dL) was lower than the CDC level of concern (10 microg/dL), with one child diagnosed with lead poisoning (BLL>65 microg/dL). A seasonal trend of BLLs was suggested, with BLL in monsoon season (Geometric Mean=9.1 microg/dL, SD=5.7 microg/dL) higher than that in the non-monsoon season (Geometric Mean=7.3 microg/dL, SD=4.0 microg/dL). A seasonal periodicity of lead in PM10 was found, with lead in monsoon season (Geometric Mean=0.04 microg/m3, SEM=0.000667 microg/m3) lower than that in the non-monsoon season (Geometric Mean=0.38 microg/m3, SEM=0.10 microg/m3). The overall level of airborne dust (PM10) in monsoon season (56.2 microg/m3) was lower than in the non-monsoon season (273.0 microg/m3), presumably due to precipitation. The comparatively higher BLLs in the monsoon season, in the presence of lower air lead levels, suggest ingestion of water or food, with greater lead contamination in the monsoon season, as a possible pathway contributing to elevated BLLs in these children in the monsoon season. These results demonstrate a significant success of the public health system in Bombay, India-achieved by the removal of lead from gasoline. The emphasis should shift in the study region towards sources of lead exposure other than leaded gasoline (lead in paints, lead in Herbal medicines and lead in Kohl).     

The cadmium and lead content of suspended particulate matter emitted from a U.K. refuse incinerator

Suspended particulate matter (SPM), sampled from the stack of a large refuse incinerator in the U.K., contained markedly elevated levels of Cd (approximately 1600 micrograms g-1) and Pb (approximately 3%). These values were similar to those previously reported for several other incinerators in Europe, but the Pb concentrations were lower than in the SPM from three American incinerators. Calculation of the metal concentration ratio SPM/fly ash for the U.K. incinerator revealed a three-fold enrichment of the two metals on the SPM. Similar ratios were obtained for several other European incinerators; this correspondence in metal partitioning was linked to the use of electrostatic precipitators in these facilities. The SPM metal data obtained in this study were used to estimate atmospheric emissions of 0.5 t Cd year-1 and 11 t Pb year-1 from the incinerator. Extrapolation of the Cd and Pb emission factors derived from this study to the quantity of refuse incinerated in the U.K. results in atmospheric discharges of 6 t Cd year-1 and 115 t Pb year-1. These estimates are in good agreement with those previously reported by an emissions inventory which identified incineration as the single largest source of airborne Cd in the U.K.     

Correlations, partitioning and bioaccumulation of heavy metals between different compartments of Lake Balaton

Correlations between trace metals in dissolved and particulate phases, zooplankton, mussels and sediments in Lake Balaton were investigated. The degree of correlation between the various metals was different in each of the investigated compartments. Particulate metal concentrations (microg g(-1)) were anti-correlated with suspended particulate matter (SPM) (mg l(-1)), indicating a dilution effect, while total metal concentrations in the water column (microg l(-1)) were highly correlated with SPM, implying a major influence of the turbidity on the total metal concentrations. Between compartments, not many significant correlations were recognized. Only Ba, Ca, Sr and Mg are correlated in the sediments and in the particulate phase, suggesting common sources for both compartments. Partitioning coefficients (Kd) of trace metals between dissolved and particulate phases are generally low, typical for natural water and fairly stable over the lake. Most of the trace metals (Zn, Co, Cd and Pb) exist in the particulate phase (for about 70% of the total metal load). Cu and Ni are exceptions, showing a more equal distribution. Bioconcentration factors (BCF) of zooplankton and mussels were comparable to those of other natural waters. A negative biomagnification from suspended particulate matter to zooplankton and from sediment to mussel was recognized for all trace metals, except a small enrichment of Zn in zooplankton and Cd in mussel. Four factors were recognized in SPM and in sediments but they did not contain the same group of metals. Cluster analysis showed that metal accumulations in the sediments were different between northern and southern shores and in SPM between western and eastern areas.     

Algal-derived organic matter as precursors of disinfection by-products and mutagens upon chlorination

Algal-derived organic materials (including algal cells, hydrophilic and hydrophobic proteins) from Chlamydomonas sp. (a common green alga in local reservoirs), were chlorinated in the laboratory (20 °C, pH 7, Cl₂/DOC ratio of 20 mg Cl₂ mg⁻¹). Levels of disinfection by-products and mutagenicity (via Salmonella T100 mutation assay, -S9) over 2 h of chlorination time were determined. The hydrophilic proteins were more effective precursors of chloroform (35.9 μmol L⁻¹ at 120 min), 35 times greater than that from the hydrophobic proteins; whereas the hydrophobic proteins were more potent precursors of direct-acting mutagens (maximum level of 50.1 rev μL⁻¹ at 30 s) than the hydrophilic proteins (maximum level of 3.38 rev μL⁻¹ at 60 min). The mutagenicity of the chlorinated solutions generally reached a peak level shortly after chlorination and then declined afterwards, a pattern different from that of chloroform generation. The results indicate that algal hydrophilic proteins, containing low aromaticity and difficult to be removed via coagulation/flocculation, are important chloroform precursors. It is also suggested that hydrophobic organic intermediates with low molecular weight formed during chlorination may serve as the direct-acting mutagens.