Decrease In Metal Concentrations Research Articles

Long-term assessment of the environmental fate of heavy metals in agricultural soil after cessation of organic waste treatments

The current study examined the anthropogenic accumulation and natural decrease in metal concentrations in agricultural soils following organic waste application. Three common organic wastes, including municipal sewage sludge, alcohol fermentation processing sludge, and pig manure compost (PMC), were applied annually to an agricultural soil under field conditions over 7 years (1994-2000) at a rate of 12.5, 25, and 50 ton ha(-1) year(-1) and the soil accumulation of three metals of concern (Cu, Pb, and Zn) was monitored. Subsequently, organic waste amendments ceased and the experimental plots were managed using conventional fertilization for another 10 years (2001-2010) and the natural decrease in metal concentrations monitored. Although Cu and Zn concentrations in all experimental plots did not exceed the relevant guideline values (150 mg kg(-1) for Cu and 300 mg kg(-1) for Zn), significant increases in metal concentrations were observed from cumulative application of organic wastes over 7 years. For instance, PMC treatment resulted in an increase in Cu and Zn from 9.8 and 72 mg kg(-1) to 108.2 and 214.3 mg kg(-1), respectively. In addition, the natural decrease in Cu and Zn was not significant as soils amended with PMC showed only a 16 and 19 % decline in Cu and Zn concentrations, respectively, even 10 years after amendment ceased. This research suggested that more attention must be paid during production of organic waste-based amendments and at the application stage.

SYNTHESIS OF TETRAKIS-N,N,N-TRIMETHYLAMMONIUMMETHYL-C-3,4-DIMETHOXYPHENYLCALIX[4]RESORCINARENE IODIDE BASED VANILLIN AND ITS ANTIDOTE ACTIVITY FOR CHROMIUM(VI) INTOXICATION

A research has been conducted to synthesize tetrakis-N,N,N-trimethylammoniummethyl-C-3,4-dimethoxyphenylcalix[4]resorcinarene iodide from vanillin and investigate its antidote capability for Cr(VI) intoxication. The synthesis was carried out in four steps i.e. (1) O-alkylation of 4-hydroxy-3-methoxybenzaldehyde, (2) HCl-catalyzed condensation of 3,4-dimethoxybenzaldehyde with resorcinol, (3) Mannich reaction of C-3,4-dimethoxyphenylcalix[4]resorcinarene with formaldehyde and dimethylamine in the presence of HCl to yield tetrakis-N,N-dimethylaminomethyl-C-3,4-dimethoxyphenylcalix[4]resorcinarene, and (4) treatment the Mannich base with methyl iodide to produce the quaternary ammonium salt of tetrakis-N,N,N-trimethylammoniummethyl-C-3,4-dimethoxyphenylcalix[4]resorcinarene iodide. According to the analysis of 1H-NMR spectrometer, the targeted compounds tend to exist in the chair (C2h) conformation. The capability of resorcinarene for Cr(VI) antidote was examined by orally injection method on mice groups. Based on LD50 determination, the resorcinarene was classified as non toxic compound according to Loomis criteria. Therapeutic using quaternary ammonium-modified resorcinarene was able to reduce metal concentrations of Cr(VI) in liver, kidney, and serum in the magnitude of 78.30; 85.72, and 88.79%, respectively. The higher dose of drug administered the greater decrease in the level of heavy metal. Judging from the amount of milligrams of reduced chromium per gram of organ, kidney is the organ having highest decreasing metal concentrations.

Mass-dependent and mass-independent variations in the isotope composition of mercury in cores from lakes polluted by a smelter: Effects of smelter emissions, natural processes, and their interactions

Analysis of sediment cores from three lakes polluted by a smelter and located 3.8, 9.4, and 21.0km from it revealed that mercury (Hg) in smelter fallout has an isotope signature which denotes enrichment in lighter isotopes by mass-dependent fractionation (MDF), suggesting volatilisation as isotopically light Hg(0) followed by oxidation to reactive gaseous Hg(II) by flue gas constituents. However, the signature was detected only in the lake closest to the smelter; elsewhere it was obliterated by MDF and mass-independent fractionation (MIF) due to natural processes, whose effects varied with environmental factors, including smelter emissions. MIF caused depletion in 199Hg and 201Hg in all three lakes and was enhanced by dissolved organic matter but inhibited by heavy metals from the smelter; yet inter-lake comparison showed that the inhibition increased with decreasing metal concentration (i.e. with increasing distance from the smelter). Inhibition of MIF by metals was strongest in acidic and oxidising environments, and the inhibitory effects of individual metals depended on the metal's atomic polarisability. MDF was controlled by different processes, was more sensitive to local conditions, correlated with sulphate concentrations in lake water, and showed weaker net inhibition by metals; and inhibition by individual metals depended on the standard enthalpy of formation of the aqueous metal cation. Moreover, the combined effects of MDF and MIF varied with the sediment's Zn/Cu ratio but not with its Zn or Cu concentration alone. MIF is attributable to activities of anaerobic heterotrophic bacteria which were inhibited by the metals, whose toxicity depended on the properties, speciation, bioavailability, and interactive effects of the metals. The exacerbation of metal toxicity under acidic and oxidising conditions, and with increasing distance from the smelter, can be explained by enhanced bioavailability. MDF, too, is attributable to effects of bacteria, metals, and environmental variables but involved different mechanisms and pathways.

Evaluation of Heavy Metal in Soils From Enyimba Dumpsite in Aba, Southeastern Nigeria Using Contamination Factor and Geo-Accumulation Index

The manner in which municipal wastes generated are disposed in most urban areas in Nigeria is worrisome. The upsurge in population density and its resultant increase in urbanization and industrialization and the amount of waste generated in Aba, are of great concern. The objective of this research is to evaluate the concentration of some heavy metals in soils in the vicinity of Enyimba dumpsite in Aba, Nigeria. Thirty soil samples were collected and analyzed in the laboratory for some heavy metals by atomic absorption spectrophotometric method and multivariate statistical techniques. Twenty-five of the samples were obtained from the vicinity of the dumpsite while five samples are collected far away from the dumpsite to serve as control samples. The overall decreasing metal concentration in the dumpsite soil is: Cd > Co > Cu > Zn > As > Pb > Mn > Ni > Cr. A positive correlation exists between Cd and organic matter (r = 0.598). Geo-accumulation index and contamination factor showed a moderate contaminated with Cd only while the other metals are in their uncontaminated level. Factor analysis revealed four major components accounting for 78.82% of cumulative variance of the contamination: Cd, Cu, Co and organic matter; Pb, Zn and pH; Mn, As, clay + silt and finally Cr and Ni. From the above observations, it is evident that only Cd showed more pronounced level of pollution than any other metal. The need to replace open dumpsites with well designed sanitary landfills is advocated.

Dispatches

Dispatches

Long-term dispersal of heavy metals in a catchment affected by historic lead and zinc mining

The Matylda catchment, in southern Poland, was polluted by the discharge of mine waters from a lead and zinc mine that inundated parts of a valley floor and caused the accumulation of metal-polluted sediments. After a partial reclamation of the mine site in the early 1980s, polluted sediments continue to accumulate on downstream floodplains and in fishponds. The aim of this study was to reconstruct the changes in metal dispersal during 100 years of mining and during the 40-year post-mining period and to propose a strategy for pollution mitigation in the area. Analyses of Cu, Cd, Pb, Zn, Mn, Ca, Mg and Fe concentrations, speciation of heavy metals and mineralogical analyses were undertaken on overbank sediment cores and in stream sediments. Concentrations of the same elements and macro-ions soluble in stream waters were also determined. Concentrations of Zn, Cd and Pb in the sediment profiles vary between 40,000 and 55,000, 300 and 600 and 30,000 and 50,000 mg kg-1, respectively. Changes of metal concentrations and the stratigraphy of sediments from the floodplains, stream channels and fishponds suggest rapid changes of metal loads migrating downstream during both the mining and post-mining periods. Since the time of mine closure, fine-grained, mine-derived sediments (ca. 12 cm thick) have been the main source of pollution of post-mining sediments and surface waters. Closure of the mine was followed by a relatively short period of rapid redistribution of sediment-associated heavy metals in the stream channel. Since the 1980s, the floodplain and fishponds have received a constant supply of metals. It contrasts with the slow sediment accretion rate and a rapid decrease of metal concentrations in floodplain pools due to dilution by decomposed leaf litter. A fivefold increase of Cd content in waters over the 4.6 km reach of the Matylda stream indicates continuous leaching of this element from the contaminated valley floor. Unsuccessful mine site rehabilitation is due to leaching of mine-originated sediments dispersed over the valley bottom. However, the rate of metal remobilization over the last 40 years is low because of the small thickness and widespread anoxic conditions that prevail within both recent and mine-originated sediments and the alkaline pH of stream water, which reduces metal mobility. Distribution of the contaminated layer over a large area of the valley bottom precludes cost-efficient catchment rehabilitation.

Status of marine pollution research in South Africa (1960–present)

The published literature on marine pollution monitoring research in South Africa from 1960 to present was evaluated. There has been a general decline in the number of papers from the 1980s and this can be linked to the absence of a marine pollution monitoring programme in South Africa. General trends observed were that contaminant exposure monitoring of metals predominates the research conducted to date. Monitoring results indicate that there has been a general decrease in metal concentrations in South African coastal waters and concentrations of metals and most organics in mussels are lower than in other industrialised nations. This is reflected in the general pristine nature and high biodiversity of the South African coastline. The establishment of a national marine pollution monitoring framework would stimulate marine pollution research.

Bioavailability and extraction of heavy metals from contaminated soil by Atriplex halimus

Pot experiments were performed to evaluate the phytoremediation capacity of plants of Atriplex halimus grown in contaminated mine soils and to investigate the effects of organic amendments on the metal bioavailability and uptake of these metals by plants. Soil samples collected from abandoned mine sites north of Madrid (Spain) were mixed with 0, 30 and 60Mgha−1 of two organic amendments, with different pH and nutrients content: pine-bark compost and horse- and sheep-manure compost. The increasing soil organic matter content and pH by the application of manure amendment reduced metal bioavailability in soil stabilising them. The proportion of Cu in the most bioavailable fractions (sum of the water-soluble, exchangeable, acid-soluble and Fe–Mn oxides fractions) decreased with the addition of 60Mgha−1 of manure from 62% to 52% in one of the soils studied and from 50% to 30% in the other. This amendment also reduced Zn proportion in water-soluble and exchangeable fractions from 17% to 13% in one of the soils. Manure decreased metal concentrations in shoots of A. halimus, from 97 to 35mgkg−1 of Cu, from 211 to 98mgkg−1 of Zn and from 1.4 to 0.6mgkg−1 of Cd. In these treatments there was a higher plant growth due to the lower metal toxicity and the improvement of nutrients content in soil. This higher growth resulted in a higher total metal accumulation in plant biomass and therefore in a greater amount of metals removed from soil, so manure could be useful for phytoextraction purposes. This amendment increased metal accumulation in shoots from 37 to 138mgpot−1 of Cu, from 299 to 445mgpot−1 of Zn and from 1.8 to 3.7mgpot−1 of Cd. Pine bark amendment did not significantly alter metal availability and its uptake by plants. Plants of A. halimus managed to reduce total Zn concentration in one of the soils from 146 to 130mgkg−1, but its phytoextraction capacity was insufficient to remediate contaminated soils in the short-to-medium term. However, A. halimus could be, in combination with manure amendment, appropriate for the phytostabilization of metals in mine soils.

Municipal sewage sludge characteristics and waste water treatment plant effectiveness under warm climate conditions

The present paper deals with the characterization of the municipal sewage sludge (MSS) and the effectiveness of the waste water treatment plant (WWTP) under warm climate condition. The WWTP effectiveness is more than 98.5% for the BOD5, 90% for COD, 95% for SS, 70% for TN, 99% for NH4, while the TP efficiency rang from 15.17% to 99.12%. The total kWh/kgBOD5/month is from 1.97 to 3.13, while the total kWh/m3 of wastewater influent range from 0.62 to 1.36. The yearly chemical consumption (chlorine, polymer, lime) depends at the end from the season. The sludge does not present significant concentration of metals and the evaluation with sequential extraction showed that the metals are associated with inert forms while the application of the, Generalized acid neutralization capacity (GANC) test indicated that by increasing the leach ate pH, the heavy metal concentration decreases.

Decrease of Zn, Cd and Pb concentrations in marine fish species over a decade as response to reduction of anthropogenic inputs: The example of Tagus estuary

Concentrations of Zn, Cd and Pb were measured in muscle of pelagic, demersal and benthic fishes, captured in the coastal area adjoining the Tagus estuary (Portugal), in 1998 and 2010. Additionally, Pb and Cd were determined in estuarine waters, showing a pronounced decrease between 1999 and 2010. Accordingly, specimens captured in 2010 presented significantly lower metal concentrations than individuals caught in 1998. Reductions were more evident for Pb (reduction of 59–99%) than for Cd (14–93%) and Zn (17–54%). Values in pelagic and demersal species exhibited higher reductions than in benthic species. Decrease of metal concentrations in fish appears thus to reflect the improvement of estuarine water quality as anthropogenic sources have been reduced or eliminated. Furthermore, it emphasises the usefulness of the descriptor “Contaminants in Fish” to assess the efficiency of measures to achieve a good environmental status, in the scope of the Marine Strategy Framework Directive.

English

Like many large abandoned mining areas, the Tri-State Mining District of the central US is plagued by numerous environmental problems, including contaminated soils, tailings, waste rock, and water, with subsequent detrimental impacts to human and ecological health. In one of the major basins of the district, the Tar Creek watershed, impacts to surface waters were once deemed to be due to irreversible man-made damages, resulting in minimal effort to address environmental risk from these legacy mine waters over the past 30 years. However, recent watershed-scale environmental monitoring studies, along with completion and evaluation of a full-scale passive treatment demonstration project, indicate that this may no longer be the case. Evaluation of artesian discharges indicates significant evolution of mine pool water quality (e.g., decreased metal concentrations, increased pH and alkalinity) since first flush. In-stream water quality, although still not meeting designated beneficial uses, has also changed. Substantial surface water degradation due to waste rock and tailings runoff and leachate is still problematic, but large-scale land reclamation (including wholesale removal and underground injection) is ongoing. Conceptual designs for watershed-scale passive treatment implementation have been developed and indicate that both artesian mine discharges and remaining runoff/leachate waters may be treatable in a cost-effective and sustainable manner. Recent voluntary relocation efforts, resulting in the dissolution of historic mining communities, provide opportunities for watershed-scale remediation and restoration. However, long-term operation and maintenance obligations for the proposed passive systems, incorporating the cultural and social needs of Native American tribes, requires sustained commitment of technical and financial resources. Promising initial results, coupled with results from other ongoing remediation efforts, warrant further exploration and reevaluation of previous administrative decisions.

A modeling assessment of contaminant fate in the Bay of Quinte, Lake Ontario: Part 1. Metals

A mass balance model of contaminant fate-transport was used to assess the fate of four metals: As, Cd, Cu and Zn, in the Bay of Quinte for hydrologic conditions and loadings in 2000. Results were compared with previous model results of 1988. The model was based on the QWASI (Quantitative Water Air Sediment Interaction) approach and the fugacity/aquivalence concept. The Bay was divided into five geographic segments based on hydrodynamics and chemical loadings. The model identified tributaries and Lake Ontario as the major sources of metal loadings to the Upper and Lower Bays, respectively. Metal concentrations in water decreased by 40–75% in the tributaries between May 1988 and 2000, which resulted in decreased metal concentrations that were, in 2000, all below the Provincial Water Quality Objectives. Measured sediment concentrations exceeded the Lowest Effect Levels (LEL) for all metals at many sites in the Upper and Lower Bays. Using 2000 metal loadings from tributaries and Lake Ontario, the model predicted that sediment concentrations will meet or come within 20% of LELs for all metals in segment 1, As in segments 2 and 3, and Zn in segment 3 within 40 years. Although the model predicted that sediment concentrations would decline to the LEL for all segments within 26 (Zn) to 54 (Cu) years, evidence suggests that benthos are now not impaired by ambient sediment concentrations (excluding “hot spots”). Reducing sediment concentrations faster is expected to be very difficult because their loadings originate from diffuse sources in the watersheds of tributaries and Lake Ontario.

Physico-chemical changes in metal-spiked sediments deployed in the field: Implications for the interpretation of in situ studies

Manipulative field studies are useful for investigating cause–effect relationships between contamination and benthic community health. However, there are many challenges for creating environmentally relevant exposures and determining what measurements are necessary to correctly interpret the results. This study describes the physical and chemical changes in the properties of metal-spiked marine sediments deployed in four different locations for up to 11 months. The test sediments lost between 20% and 75% of their volume during the deployment period, with the greatest losses occurring at sites affected by strong hydrodynamic activity. More sediment was lost from clean treatments than those spiked with high metal concentrations and corresponded with differential recruitment of infauna to these treatments. In general, a greater proportion of spiked-metals remained at lower energy sites (48–85%) than at higher energy sites (15–48%). The decreased metal concentrations were attributed mostly to the loss of the metal-spiked sediments (through resuspension) and their dilution with sediments depositing from the surrounding environment. A range of recommendations are made for optimising the information gained from field-based studies using metal-spiked sediments. These include the careful documentation of physico-chemical sediment properties pre- and post-deployment, the use of co-located sediment traps and knowledge of site-specific hydrodynamic processes.

Heavy Metals Contamination of Road-Deposited Sediments

Problem statement: Impact of anthropogenic activities on man and his environment as a result of the growing rate of urbanization in Bida, Nigeria is of a great concern. Street sediments that accumulate along pavements in urban environments have the potential to provide considerable loadings of heavy metals to receiving waters and water bodies, particularly with changing environmental conditions. The objective of this research was to evaluate the streets sediment contamination in Bida, Nigeria. Approach: Fifty five sediment samples were collected from four roads that experience intense traffic conditions and analyzed in the laboratory for some heavy metals by atomic absorption Spectrophotometric method and multivariate statistical techniques. Results: The overall decreasing metal concentration order was: Pb > Mn > Fe > Zn > Cu > Cr > Ni > Cd. Significantly positive correlation was only found between Cd and organic matter (r = 0.580). Factor analysis shows that road deposited sediment quality data consists of four major components accounting for 77.11% of cumulative variance of the contamination: Ni, pH and silt + clay; Cr, Fe and organic matter; Mn and Zn and finally Cu and Pb. Discriminant analysis revealed that the first two Discriminate Functions (DF1 and DF2) contain 90.61% information for Cu, Pb and Ni accumulation. Conclusion: This study concluded that the concentrations of all metals measured in Bida can be considered to present a low level of contamination and that multivariate statistical analysis is a useful tool in understanding contaminants relationships.

Arbuscular Mycorrhizal Fungi, Bacillus cereus, and Candida parapsilosis from a Multicontaminated Soil Alleviate Metal Toxicity in Plants

We investigated if the limited development of Trifolium repens growing in a heavy metal (HM) multicontaminated soil was increased by selected native microorganisms, bacteria (Bacillus cereus (Bc)), yeast (Candida parapsilosis (Cp)), or arbuscular mycorrhizal fungi (AMF), used either as single or dual inoculants. These microbial inoculants were assayed to ascertain whether the selection of HM-tolerant microorganisms can benefit plant growth and nutrient uptake and depress HM acquisition. The inoculated microorganisms, particularly in dual associations, increased plant biomass by 148% (Bc), 162%, (Cp), and 204% (AMF), concomitantly producing the highest symbiotic (AMF colonisation and nodulation) rates. The lack of AMF colonisation and nodulation in plants growing in this natural, polluted soil was compensated by adapted microbial inoculants. The metal bioaccumulation abilities of the inoculated microorganisms and particularly the microbial effect on decreasing metal concentrations in shoot biomass seem to be involved in such effects. Regarding microbial HM tolerance, the activities of antioxidant enzymes known to play an important role in cell protection by alleviating cellular oxidative damage, such as superoxide dismutase, catalase, glutathione reductase, and ascorbate peroxidase, were here considered as an index of microbial metal tolerance. Enzymatic mechanisms slightly changed in the HM-adapted B. cereus or C. parapsilosis in the presence of metals. Antioxidants seem to be directly involved in the adaptative microbial response and survival in HM-polluted sites. Microbial inoculations showed a bioremediation potential and helped plants to develop in the multicontaminated soil. Thus, they could be used as a biotechnological tool to improve plant development in HM-contaminated environments.

Determination of Free Cd, Cu and Zn Concentrations in Lake Waters by In Situ Diffusion Followed by Column Equilibration Ion-exchange

Combining in situ diffusion and column ion-exchange equilibration, we measured free metal ion concentrations (Cd, Cu and Zn) in water samples collected from the epilimnion of 14 lakes in the Rouyn-Noranda area (600 km north-west of Montreal, QC, Canada). Lakes were selected to represent a wide range of physico-chemical characteristics (hardness, pH, dissolved organic matter—DOM, degree of metal contamination), to determine the influence of these parameters on metal speciation. Total dissolved metal concentrations, as determined within the diffusion cells, varied over one to two orders of magnitude: [Cd] 0.19–2.9 nM; [Cu] 36–190 nM; [Zn] 7–2,800 nM. The proportion of total dissolved metal present as free Cd2+ and Zn2+ was relatively constant for the 14 selected lakes, despite the wide pH (4.5–8) and DOM (3–23 mg C/L) ranges, probably reflecting the inverse relationship observed between pH and DOM; this proportion did, however, vary with DOM and pH for Cu. Our experimental free metal ion concentrations were compared with those calculated with the thermodynamic models WHAM (Windermere Humic Aqueous Model VI) and ECOSAT 4.7 (incorporating the NICA-Donnan model). Measured and calculated values were in reasonable agreement for both Cd and Zn although measured values were generally slightly higher, i.e. less than one order of magnitude. For several lakes, measured free Cu concentrations were, however, much higher than the calculated values, suggesting that these models overestimate Cu complexation. The gap between measured and calculated free metal ion concentration becomes more important as the total metal concentration decreases and as pH increases.

Heavy metals leachability before, during and after composting of sewage sludge with natural clinoptilolite

Environmental problems associated with sewage sludge disposal have prompted strict legislative actions over the past years. At the same time, the upgrading and expansion of wastewater treatment plants have greatly increased the volume of sludge generated. The major limitation of land application of sewage sludge compost is the potential high heavy metal content in relation to the metal content of the original sludge. Composting of sewage sludge with natural zeolite (clinoptilolite) can enhance its quality and suitability for agricultural use. The aim of the article is to examine the leachability of the heavy metals before, during and after the composting process of sewage sludge and clinoptilolite. The natural zeolite, clinoptilolite has the ability to uptake heavy metals in satisfactory levels. In order to estimate the metal leach ability of the final product of compost, the generalized acid neutralization capacity (GANC) procedure was used, and was found that by increasing the leachate pH, the heavy metal concentration decreases.

Passive diffusion assessment of cadmium and lead accumulation by plants in hydroponic systems

In experiments with willow planted in cadmium- or lead-contaminated Knopp nutrient solutions, the ability of willow and chelex gel in the diffusive gradient in a thin film (DGT) unit to absorb these elements was observed and compared. A method to compare the accumulated amount of metals by the willow and the sorbed amount of metal onto the DGT unit was designed. The accumulated/sorbed amount of metals was recalculated to the same units (μg cm−2 day−1). The study of Cd(Pb) dynamic uptake by willow showed an exponential decrease of metal content in the exposure solution. The willow planted in the Knopp nutrient solution accumulated Cd(Pb) less than did the DGT unit in the same matrix. The willow planted in the soil/water system accumulated more lead than did the willow in a lead-contaminated aquatic system nor did the DGT unit in the nitrate matrix. The willow further accumulated lead from the soil/water system due to the active co-uptake of nutrients and lead. The DGT technique was considered as very good comparative method to measure heavy metals plant uptake. This technique is suitable for use in water as well as in soil systems.

Heavy metal contamination in the vicinity of an industrial area near Bucharest

Heavy metals such as lead are well known to cause harmful health effects. Especially children are particularly susceptible to increased levels of lead in their blood. It is also a fact that lead concentration is increasing in the environment due to increased anthropogenic activity. The risk of heavy metal contamination is pronounced in the environment adjacent to large industrial complexes. In a combined case study, the environmental pollution by heavy metals was related to children's health in the vicinity of an industrial area located 4 km south-east from Bucharest about 2 km east from the nearest town-Pantelimon. This site includes companies processing different, nonferrous solid wastes for recovery of heavy metals and producing different nonferrous alloys and lead batteries. In this paper, mainly the results of environmental sampling and analyses are summarized. Water, soil, and atmospheric deposition samples were collected from different locations within 3 km from the industrial area. For comparison, samples were also taken from Bucharest. Water samples were filtered (<0.45 microm), extracted by salpetric acid, and quantified by ICP-OES and ICP-MS. Soil samples were dried, sieved (<2 mm), extracted by aqua regia and analyzed by AAS. In order to quantify the atmospheric deposition, three kinds of permanently open collecting pots were used on nine different sites between August and November 2006. At most sampling locations, the heavy metal concentrations in soil decrease with increasing distance to the presumably major source of pollution. Highest heavy metal concentrations were found in 10-20 cm soil depths. There were also decreasing heavy metal concentrations for atmospheric deposition with increasing distance to the industrial site. In surface and groundwater samples, traces of zinc, copper and lead were detected. The heavy metal concentrations in soil were increased in the study area, mostly under legal action limits in low-concern areas (e.g., 1,000 mg Pb/kg dry soil), but often above action limits for high-concern areas (100 mg Pb/kg dry soil) such as populated areas. The soluble lead concentrations in water samples indicate a need for monitoring and assessing water quality in more detail. The results for atmospheric deposition showed increased dust precipitation and heavy metal loads in the study area compared to Bucharest. However, based on mass flow balance calculations, the actual atmospheric deposition of heavy metals must be much lower than it was in the past decades. It was shown that highest lead values in water, soil and atmospheric deposition are rather to be found near the investigated industrial site than at the control sites in Bucharest. Our results correspond very well with results that show that children from Pantelimon have significantly increased lead concentrations in their blood compared to children in Bucharest. The increased lead contamination around the investigated industrial area is likely to have caused the increased exposure for children living in Pantelimon. In high-concern areas, such as found in populated areas, further measures have to be taken to avoid health risks for people living in these areas. The measures already taken to reduce emissions from the industrial site will help to avoid further increases in heavy metal concentrations. In areas with exceeded action limits, measures have to be taken as required by law. Detailed risk assessments could help to take necessary actions to protect public health in this area. The public should be informed about the potential hazards of eating plants grown in that area. Educational programs for schools, informing children about the contamination, should lead to a better understanding of environmental problems and a more sustainable behavior in the future.

Geochemical and microfaunal proxies to assess environmental quality conditions during the recovery process of a heavily polluted estuary: The Bilbao estuary case (N. Spain)

This study explores the eventual environmental improvement of the Bilbao estuary (northern Spain), from 1997 to 2006, in order to assess current estuarine restoration being undertaken as part of a Revitalization Strategic Plan. The monitoring programme is based on spatial and temporal variation in the distributions of both benthic foraminiferal assemblages and heavy metals contained in surficial sediments from the polluted intertidal flats. The overall pattern shows a decreasing metal concentration; however, reversals to this trend are noticed in the middle estuary. From 2000 to 2003, a significant decrease in heavy metal concentration was observed which is most likely related to the implementation in 2001–2002 of the biological treatment at a central wastewater treatment plant. Although the metal concentration decreased by 85% for some elements, these values still remain considerably high. No significant change occurred between 2003 and 2006 in metal concentrations. During the monitoring period the estuary channel presented environmental conditions close to azoic in 3/4 of its watercourse. Only in the year 2006, the two lowermost estuarine samples exhibited an increase in microfaunal densities. These samples were dominated by pollution-resistant estuarine species. The fact that estuarine sediments quality is recovering very slowly seems to be caused mainly by the resuspension of accumulated contaminants in the sediments due to dredging and working activities in the estuary. Thus, local authorities should consider also the clean up of the pollutants stored in the sediments, not seeking only the achievement of the water quality standards, as these polluted sediments can act as source of contamination.