Summary of the Workshop on Peat Bog Archives of Atmospheric Metal Deposition

Water, Air, &; Soil Pollution -     

Cd,Cu, Pb and Zn Concentrations in Atmospheric Wet Deposition at a Coastal Station in Western Europe

Water, Air, &; Soil Pollution - Bulk rainfalls were sampled during ten months in the Eastern Channel (Northern France). Chloride and sodium are the heavily loaded major ions in wet deposition,...     

Pb and Cd Concentrations in a Southern Bavarian Bog Profile and the History of Vegetation as Recorded by Pollen Analysis

In the lower part of a raised bog profile from Langegger Filz, southern Bavaria, the Pb and Cd concentrations were comparatively low while considerably higher concentrations of both elements were observed in the upper section of the profile. The peat layers with the highest concentrations of Pb and Cd were found to date from the Iron Age, the Roman Age, and the Middle Ages. The Fagus pollen curve reflects the beginning of a beech decline exactly in those peat layers in which the start of the Pb increase is visible. Therefore it appears that metal smelting caused a local release of heavy metals which were subsequently deposited in the raised bog. Metals could only be smelted when wood was cut and burned, and beech charcoal was preferred as it produces relatively high temperatures. The good agreement between the Pb concentration profile and the pollen analyses suggests that the bog provides an accurate record of atmospheric Pb deposition.     

Lead in Three Peat Bog Profiles,Jura Mountains,Switzerland: Enrichment Factors,Isotopic Composition,and Chronology of Atmospheric Deposition

One metre cores were taken from three peat bogs in the Jura Mountains of Switzerland: Etang de la Gruère (EGr), La Tourbière des Genevez (TGe), and Praz Rodet (PRd). Dried peat samples were analyzed for lead (Pb) using the EMMA XRF and scandium (Sc) using INAA. Enrichment factors (EF) were calculated by normalizing to the background Pb/Sc ratio at EGr. Age dates were obtained using 210Pb (CRS Model) and confirmed using pollen chronostratigraphic markers in replicate cores. The isotopic composition of Pb in selected peat samples from EGr and TGe was determined using TIMS. Two pronounced peaks in Pb EF occur in the uppermost sections of all three bogs: the upper one corresponds to the late 1960's to late 1970's and the lower one to approximately 1900 to 1920. At EGr, sample 2f5 (11 cm, 86 µg/g Pb, EF = 91, and dated at A.D. 1967 ± 2) has an isotopic composition similar to that of leaded gasoline used in Berne in the 1970's. For comparison, the older peak at EGr (sample 2fl 1 at 29 cm, 84 µg/g Pb, EF = 79 and dated at A.D. 1905 ± 6) is significantly different. In contrast to these two samples, the isotopic composition of sample 2fl 5 (41 cm, 30 µg/g Pb, EF = 13 and pre-dating ca. A.D. 1800) approaches the present day "average terrestrial lead" and is likely to be predominately lithogenic. Therefore, the isotopic data show that the Pb introduced to the bog from leaded gasoline has not penetrated to this depth in the profile. A simple mass balance using the measured Pb concentrations and the isotopic compositions shows that vertical migration of gasoline Pb cannot explain the deeper, older peak in Pb EF. A more likely explanation is that the older peak reflects the rates of atmospheric Pb deposition during the first two decades of the 20th century. Taken together, the Pb concentrations, age dates, and isotopic data suggest that these peat profiles have preserved the record of changing rates of atmospheric Pb deposition. In addition, the results indicate that the isotopic composition of Pb deposited on the surface of the bogs gradually shifted away from lithogenic ratios as long ago as the middle of the 19th century, a change which clearly pre-dates the introduction of leaded gasoline.     

Temporal Patterns of the Wet Deposition of Zn,Cu, Ni,Cd and Pb: The Arcachon Lagoon (France)

We report here the first data set on wet deposition of heavy metals in the southwestern French coastal zone. In this region, there are two major sensitive coastal ecosystems: the Gironde Estuary and the Arcachon Lagoon. Chemical analyses of heavy metals were carried out by ICP-MS. Annual mean concentrations of the dissolved fraction in precipitation were 0.2, 3.4, 4.3, 8.1 and 30 μg L^-1for Cd, Ni, Cu, Pb and Zn, respectively. In terms of annual fluxes, these numbers are of the same order of magnitude as the fluxes measured in southeastern France, but are higher than those measured in western Brittany. When extrapolated to the entire Bay of Biscay, the annual wet dissolved fluxes of Cd, Ni, Cu, Pb and Zn are respectively 7, 110, 140 340 and 1440 t yr^-1. According to available data in the literature, the regional Cd, Cu, Pb and Zn atmospheric fluxes for the Bay of Biscay are of the same order of magnitude as riverine inputs (Loire and Gironde). On a daily or weekly time scale, we observed a strong variability of elemental fluxes: up to 20% of the annual dissolved flux may occur in a rain event shorter than 3.5 days. Although elements display generally parallel variations with time, they sometimes follow independent behaviours (e.g. Pb and Cd), suggesting that they may derive from different geographical and/or pollution sources.     

The Geochemistry of Ombrotrophic Sphagnum Species Growing in Different Microhabitats Of Eight German and Belgian Peat Bogs and the Regional Atmospheric Deposition

Comparing today’s atmospheric deposition records with the elemental concentration and the net-uptake rates of ombrotrophic Sphagnum mosses from eight German and Belgian peat bogs revealed that most of all the quality and number of regularly obtained deposition monitoring data is not satisfactory. Moreover, it seems likely that the deposition rate, determined by Sphagnum mosses, does not reliably reflect the record of the total open field deposition indicated by the deposition monitoring data. The moss data, too, show a distinct spatial variability possibly because the geochemistry of peat mosses differs according to the annual growth in height, the total surface area and the surface roughness of the receptor ‘peat moss’ (special interception deposition). Increased Ti concentration values, for example, combined with a high annual growth rate in height at the hollow moss S. cuspidatum resulted in generally high Ti net-uptake rates and a high Ti inventory (total Ti in sample). We, therefore, suggest that productive Sphagnum species might be able to fix more Ti particles on their larger surface area than less productive species do. Moreover, the results demonstrate that for reliably calculating Sphagnum elemental net-uptake rates, as well as for all quantification of Sphagnum or peat geochemistry on a time and area basis, an accurate knowledge of the period the collected samples were exposed to atmospheric deposition is required. In particular, to do reliable reconstructions of past atmospheric deposition rates using peat deposits, further studies are needed to precisely specify the spatial variability in the geochemistry of living Sphagnum mosses.     

典型冶炼厂大气沉降区农田耕层土壤重金属（Cd、Cu、Pb）输入输出平衡研究

为探究不同大气沉降区农田耕层土壤镉（Cd）、铜（Cu）、铅（Pb）的质量平衡特征,以距离贵溪冶炼厂34 km（背景区）、6 km（中沉降区）、1 km（高沉降区）的0~20 cm农田耕层土壤为研究对象,通过化学质量平衡方法对土壤重金属的主要输入途径（大气沉降、灌溉水、农药肥料）和输出途径（地表径流、土壤淋溶、籽粒带走）开展为期三年的监测与定量分析。结果表明：背景区、中沉降区、高沉降区由大气沉降导致的Cd年均输入通量分别为0.84、2.26、9.01 mg?m-2?a-1,分别占比43.18%、38.33%、100%;Cu年均输入通量分别为17.62、99.68、747.6 mg?m-2?a-1,分别占比80.76%、86.24%、100%;Pb年均输入通量分别为13.93、27.43、73.17 mg?m-2?a-1,分别占比97.75%、92.36%、100%。背景区和中沉降区由灌溉水导致的Cd年均输入通量分别为1.05、3.60 mg?m-2?a-1,分别占比54.62%和60.82%;农药肥料带入的重金属年均输入量占比小于5%,可忽略不计。不同沉降区土壤的主要输出途径均为地表径流和土壤淋溶,输出占比介于86.66%~100%;籽粒带走的重金属输出占比介于2.88%~13.34%。2019—2021年,背景区、中沉降区、高沉降区土壤Cd、Cu、Pb的年均净输入通量均大于0,Cd年均净输入通量分别为1.54、1.96、4.38 mg?m-2?a-1;Cu年均净输入通量分别为12.72、28.02、184.0 mg?m-2?a-1;Pb年均净输入通量分别为13.03、21.31、55.04 mg?m-2?a-1。综上,建议加强研究区域大气污染源和灌溉水质的长期监测并采取一定的控制措施,同时避免秸秆直接还田。本研究可为区域农田环境质量保护及重金属污染修复治理提供理论支持。     

土法炼锌区大气沉降Pb、Zn、Cd及其对土壤质量的影响

Dust emissions from smelters, as a major contributor to heavy metal contamination in soils, could severely influence soil quality. Downwind surface soils within 1.5 km of a zinc smelter, which was active for 10 years but ceased in 2000, in Magu Town, Guizhou Province, China were selected to examine Pb, Zn, and Cd concentrations and their fractionation along a distance gradient from a zinc smelter, and to study the possible effects of Pb, Zn, and Cd accumulation on soil microorganisms by comparing with a reference soil located at a downwind distance of 10 km from the zinc smelter. Soils within 1.5 km of the zinc smelter accumulated high levels of heavy metals Zn (508 mg kg-1), Pb (95.6 mg kg-1), and Cd (5.98 mg kg-1) with low ratios of Zn/Cd (59.1--115) and Pb/Cd (12.4--23.4). Composite pollution indices (CPIs) of surface soils (2.52--15.2) were 3 to 13 times higher than the reference soils. In metal accumulated soils, exchangeable plus carbonate-bound fractions accounted for more than 10% of the total Zn, Pb, and Cd. The saturation degree of metals (SDM) in soils within 1.5 km of the smelter (averaging 1.25) was six times higher than that of the reference soils (0.209). A smaller soil microbial biomass was found more frequently in metal accumulated soils (85.1--438 μg C g-1) than in reference soils (497 μg C g-1), and a negative correlation (P < 0.01) of soil microbial biomass carbon to organic carbon ratio (Cmic/Corg) with SDM was observed. Microbial consumption of carbon sources was more rapid in contaminated soils than in reference soils, and a shift in the substrate utilization pattern was apparent and was negatively correlated with SDM (R = -0.773, P < 0.01). Consequently, dust deposited Pb, Zn, and Cd in soils from zinc smelting were readily mobilized, and weredetrimental to soil quality mainly in respect of microbial biomass.     

Toxicity of heavy metals (Zn,Cu, Cd,Pb) to vascular plants

The literature on heavy metal toxicity to vascular plants is reviewed. Special attention is given to forest plant species, especially trees, and effects at low metal concentrations, including growth, physiological, biochemical and cytological responses. Interactions between the metals in toxicity are considered and the role of mycorrhizal infection as well. Of the metals reviewed, Zn is the least toxic. Generally plant growth is affected at 1000 μg Zn L^?1 or more in a nutrient solution, though 100 to 200 µg L^?1 may give cytological disorders. At concentrations of 100 to 200 μg L^?1, Cu and Cd disturb metabolic processes and growth, whereas the phytotoxicity of Pb generally is lower. Although a great variation between plant species, critical leaf tissue concentrations affecting growth in most species being 200 to 300 μg Zn g^?1 dry weight, 15 to 20 μg Cu g^?1 and 8–12 μg Cd g^?1. With our present knowledge it is difficult to propose a limit for toxic concentrations of Zn, Cu, Cd and Pb in soils. Besides time of exposure, the degree of toxicity is influenced by biological availability of the metals and interactions with other metals in the soil, nutritional status, age and mycorrhizal infection of the plant.     

培养基质对印度芥菜Cd、Pb、Zn富集效果的研究

通过温室土培和砂培盆栽对比试验,研究了外源Cd、Pb、Zn复合污染对印度芥菜富集重金属的效果。结果表明,印度芥菜Cd、Pb和Zn的富集量分别与土培和砂培Cd、Pb、Zn的添加量呈极显著正相关。砂培印度芥菜Cd、Pb和Zn的富集量分别远大于土培,前者印度芥菜地上部Cd、Pb、Zn的最高富集量分别达311.3,248.0,2760mg/kg,分别为土培的10.4,12.9,4.67倍;砂培条件下印度芥菜地上部Cd、Pb、Zn的提取量均大于土培,分别为土培的1.29～8.96倍、1.02～8.58倍和1.68～5.62倍;印度芥菜Cd、Pb、Zn的富集系数砂培较土培明显增大,其中富集系数的变化为CdZnPb,对Pb的富集系数除个别处理外均小于1,说明印度芥菜对Cd、Zn具有很强的富集能力,对Pb的富集能力较弱。研究表明,土培条件下Cd、Pb、Zn的生物有效性较低,直接制约着印度芥菜对土壤重金属污染的修复效果。     

Distribution of Cd, Ni, Cr, and Pb in Amended Soils from Alicante Province (SE, Spain)

Heavy metals can be transferred from soils to other ecosystem parts and affect ecosystems and human health through the food chain. Today the use of biosolids to improve the nutrient contents of a soil is a common practice. Contamination of soils by potentially toxic elements (e.g., Cd, Ni, Cr, Pb) from amendments of biosolids is subject to strict controls within the European Community in relation to total permissible metal concentrations, soil properties and intended use. In this context, heavy metal concentrations were studied in agricultural soils devoted to vegetable crops in the province of Alicante (SE Spain), where an intensive agriculture takes place. This study is aimed at ascertaining the chemical partitioning of Cd, Ni, Cr, and Pb in agricultural soils repeatedly amended with sludge. Selected soil properties relevant to control the mobility and bioavaibility of heavy metals were analyzed for the general characterisation of these agricultural soils. The distribution of chemical forms of Cd, Ni, Cr, and Pb in five biosolids-amended soils was studied using a sequential extraction procedure that fractionates the metal into soluble-exchangeable, specifically sorbed-carbonate bound, oxidizable, reducible, and residual forms. The biosolids incorporation has modified the soil composition, leading to the increment of heavy metals. The residual, reducible, and carbonate-sorbed forms were dominant. Detailed knowledge of the soil at the application site, especially pH, CEC, buffering capacity, organic matter, clay minerals, and clay content, is essential.     

Retention of Cd, Cu, Pb and Zn by Wood Ash, Lime and Fume Dust

Heavy metals are of interest due to their deleterious impacts on both human and ecosystem health. This study investigated the effectiveness of wood ash in immobilizing the heavy metals Pb, Cd, Cu and Zn from aqueous solutions. The effects of initial metal concentrations, solution pH, ash dose and reaction time on metal sorption, as well as the metal sorption mechanisms were studied. To investigate the effect of initial metal concentrations, solutions containing Cd, Zn (25, 50, 75, 100 or 125 mg L^?1), Cu (25, 50, 75, 100, 125, 150 or 175 mg L^?1) or Pb (250, 500, 750, 1000, 1250, or 1500 mg L^?1) were reacted with 10 g L^?1 ash for two hours. For the effect of pH, solutions containing 100 mg L^?1 of Cd, Cu or Zn or 1500 mg L^?1 of Pb were reacted with 15 g L^?1 ash over a pH range of 4 to 7. The wood ash was effective in immobilizing the four metals with a sorption range of 41–100 %. The amounts of metals retained by the ash followed the order of Pb > Cu > Cd > Zn. As expected, absolute metal retention increased with increasing initial metal concentrations, solution pH and ash dose. Metal retention by the ash exhibited a two-phase step: an initial rapid uptake of the metal followed by a period of relatively slow removal of metal from solution. Metal retention by the ash could be described by the Langmuir and Freundlich isotherms, with the latter providing a better fit for the data. Dissolution of calcite /gypsum minerals and precipitation of metal carbonate/sulfate like minerals were probably responsible for metal immobilization by the ash in addition to adsorption.     

Comparison of Hg and Pb Fluxes to Hummocks and Hollows of Ombrotrophic Big Heath Bog and to Nearby Sargent Mt. Pond,Maine, USA

Two hummock cores (separated by 1 m), two hollow cores (separated by 1 m and both within 5 m of the hummock) from ombrotrophic Big Heath, and a single core from Sargent Mountain Pond (12 km north-northeast of the bog), Mt. Desert Island, Acadia National Park, Maine, USA were collected in 1983 and dated using 210Pb and analyzed for a suite of major and trace metals. The hummock cores correspond closely in terms of dating profiles, concentrations of Hg and Pb, and thus trends and values for accumulation rates. The hollow cores agree generally with each other but give more subdued peaks in concentration and lower integrated anthropogenic burdens of Hg and Pb and 50% lower unsupported 210Pb than the hummock cores. Σ210Pbuns. (Bq/cm2), ΣHganth. (ng/cm2), and ΣPbanth. (µg/cm2) for the two hummock cores were 0.744 and 0.773, ≈ 130 and 130 (ng/cm2), and ≈ 159 and 138 (µg/cm2), respectively. The values for Sargent Mountain Pond were 0.411, 269, and 72, respectively. Hummock cores agree closely with the lake sediment core with respect to timing of maximum accumulation rates which occurred in the 1970s; Background atmospheric deposition rates of Hg and Pb to coastal Maine appear to have been about 2.5 to 3 ng/cm2/yr and <0.2 µg/cm2/yr, respectively. Atmospheric deposition of Hg and Pb increased to as much as 20 ng/cm2/yr and 2 µg/cm2/yr, respectively, by the 1970s and has decreased since then. Probably more than 50% of the Hg and Pb are deposited in dry and occult deposition.     

Solubility control of Cu, Zn, Cd and Pb in contaminated soils

We developed a semiempirical equation from metal complextion theory which relates the metal activity of soil solutions to the soil's pH, organic matter content (OM) and total metal content (MT). The equation has the general form: where pM is the negative logarithm (to base 10) of the metal activity, and a, b and c are constants. The equation successfully predicted free Cu²⁺ activity in soils with a wide range of properties, including soils previously treated with sewage sludge. The significant correlation of pCu to these measured soil properties in long-contaminated soils suggests that copper activity is controlled by adsorption on organic matter under steady state conditions. An attempt was made from separate published data to correlate total soluble Cu, Zn, Cd and Pb in soils to soil pH, organic matter content and total metal content. For Cu, the total Cu content of the soil was most highly correlated with total soluble Cu. Similarly, total soluble Zn and Cd were correlated with total metal content, but were more strongly related to soil pH than was soluble Cu. Smaller metal solubility in response to higher soil pH was most marked for Zn and Cd, metals that tend not to complex strongly with soluble organics. The organic matter content was often, but not always, a statistically significant variable in predicting metal solubility from soil properties. The solubility of Pb was less satisfactorily predicted from measured soil properties than solubility of the other metals. It seems that for Cu at least, solid organic matter limits free metal activity, whilst dissolved organic matter promotes metal solubility, in soils well-aged with respect to the metal pollutant. Although total metal content alone is not generally a good predictor of metal solubility or activity, it assumes great importance when comparing metal solubility in soils having similar pH and organic matter content.     

The determination of Zn,Cd, Pb and Cu in soil extracts by anodic stripping voltammetry

This work describes simultaneous determination of Zn, Cd, Pb and Cu in soil extract by d. c. anodic stripping voltammetry at the hanging mercury drop electrode. Soil samples were taken from six different areas characterized by different degrees of heavy metal pollution. The metals were extracted from the soil samples using 0.5 M HCI. The base electrolyte for ASV was 0.2 M acetic buffer at pH 5.0. These results are compared with those obtained by using atomic absorption spectrophotometric method. The accuracy and precision of the presented method are satisfactory (relative standard deviation is 3.5 to 11%). Iron, Al and Ti contained in the extract in the concentration of 1120, 5400, and 480 µg g^?1, respectively, do not present measurement difficulties.[/p]     

The flux of Cd,Cu, Pb and Zn in mining polluted soils

The monitoring of heavy metal deposition onto soils surrounding old Pb-Zn mines in two locations in the UK has shown that relatively large amounts of Cd, Pb, Zn and, in one case, Cu are entering the soil annually. Small particles of ore minerals in windblown mine tailings were found to be contributing up to 1.46 g m^?2 yr^?1 of Pb, 1.41 g m^?2 yr^?1 of Zn and 0.027 g m^?2 yr^?1 of Cd. However, when these inputs from bulk deposition are compared with the concentrations of the same metals within the soil profiles it is apparent that relatively little long-term accumulation is occurring. Metals are being lost from the soil profiles, probably through leaching. A calculated relative retention parameter gave values that ranged from 0.01 to 0.17 for Cd, 0.11 to 0.19 for Zn, 0.32 to 0.63 for Cu and over 1 for Pb. These relative retention values were found to follow the order of electronegativity of the elements concerned: Pb>Cu>Zn>Cd. Distribution coefficient (Kd) values quantifying the adsorptive capacity of the mine soils for Cd and Pb showed marked differences for the two metals (12 to 69 cm³ g^?1 for Cd and 14 to 126 cm³ g^?1 for Pb) and may, in part, account for the two to one hundred-fold variation in the relative retention parameter for the different metals within these soils.     

The effect of pH on the retention of Cu,Pb, Cd,and Zn by clay-fulvic acid mixtures

The addition of fulvic acid to clay suspensions (kaolinite, illite or montmorrillonite) resulted in increased uptake of Cu, Pb, Cd, and Zn ions over the pH range 3 to 6, due to the limited solubility of one of the metal-fulvate species formed. At higher pH values, residual metal ion was retained in solution, instead of precipitating as hydroxy species. The amount of total metal ion found in solution at equilibrium was determined by the quantity and type of clay added; the amount of organic acid present; and to a lesser extent, pH. The behavior of the clay-fulvic acid systems differed from that observed using other organic materials such as gelatine, tannic acid or a humic acid.     

Heavy metal accumulations of 24 asparagus bean cultivars grown in soil contaminated with Cd alone and with multiple metals (Cd, Pb, and Zn)

Crops grown in heavy metal contaminated soils are an important avenue for these toxic pollutants entering the human food chain. Information on how crops respond to soil contaminations of single versus multiple metals is scarce and much needed. This study investigated the accumulation of Cd by 24 cultivars of asparagus bean (Vigna unguiculata subsp. Sesquipedalis L., family Fabaceae) under a low level (0.8 mg kg-1) and a high level (11.8 mg kg-1) of Cd exposure in a garden experiment, and that in a field experiment with Cd, Pb, and Zn (1.2, 486, and 1114 mg kg-1, respectively) contaminated soil. Both experiments showed that there were highly significant variations among the tested cultivars in Cd accumulation by roots, stems, leaves, and fruits of asparagus bean. In the garden experiment, all cultivars under the low Cd exposure and 41.7% of the tested cultivars under the high Cd exposure bore fruits (pods) whose Cd concentrations were lower than 0.05 mg kg-1 fw and therefore were safe for consumption. In addition, the fruit Cd concentrations of cultivars with black seed coats were significantly lower than those with red or spotted seed coats. These results suggest that asparagus bean is a hypo-accumulator to Cd pollutant and the trait of Cd accumulation is genetic-dependent among cultivars. In the field experiment, correlation between fruit Cd and Pb concentrations was significantly positive (p < 0.05). Additional correlation analyses between two experiments showed that fruit Cd concentrations in the field experiment were significantly correlated with those exposed to the high level of Cd stress, instead of to the low level of Cd stress in the garden experiment. This suggests that the presence of other toxic heavy metals in the soil might have facilitated the accumulation of Cd in fruits, and the selection of pollution-safe-cultivars (PSC) in multi-metal polluted condition could refer to the PSCs selected under a high level exposure of a single heavy metal.     

Changes in Concentrations of Cd,Zn, Mn,Cu and Pb in Spruce (Picea abies) Needle Litter During Decomposition

Spruce (Picea abies (L.) Karst) needle litter was placedin litterbags and incubated (≥6 yr) at five spruce standsin southern Sweden. The litterbags were collected twice a yearduring year 1–2 and thereafter once a year, for total analyses(conc. HNO₃) of Cd, Zn, Mn, Cu and Pb. The main objectiveswere to document changes in concentrations and amounts of theseelements during litter decomposition and to investigate factorscontrolling the changes.Concentrations of Cd, Zn, Cu and Pb increased to at least 0.5, 1.5, 3 and 13 times the initial concentration. During the latterpart of the incubations, concentrations became more stable ordecreased. Concentrations at which the metals are considered to be toxic to micro-organisms in the mor layer were not reached during the experiment. Generally, concentrations of Mn decreased.Total amounts of Cd, Zn and Mn had decreased by at least15, 24 and 43%, from the initial amount at the end of theexperiment. The total amount of Cu increased (>40%) before itstarted to decrease. The total amount of Pb increased by over230%. Thereafter it became more constant or decreased.According to a PCA, the dynamics of total amounts of Cd,Zn and Mn in the litter were similar, as were those of Pb and Cu.Furthermore, in most cases the heavy metal amounts on anysampling occasion differed more between than within sites. Thedynamics of total amounts of elements were more similar betweenadjacent sites than between more distant sites.     

Distribution of Zn, Cd, Pb and Cu Metals in Groundwater of the Guadiamar River Basin

Traditionally, the Guadiamar River Basin (Seville, SouthwestSpain) has received pollution from two different sources. Inits upper course, from a pyrite exploitation and, in itslower reaches, from untreated urban and industrial wastes aswell as wastes from intensive agricultural activity. In 1998,the accidental release in the river of about 6 million m³ of acid water and sludge from mine tailings contributedto worsen the pollution of an already contaminated area. Themain polluting agents of the spill were heavy metals. Itaffected a large number of wells either directly or as a consequence of infiltration from polluted soils. Assessment of the pollution by total metal determination does not revealthe true environmental impact of the spill and speciation studies showing the distribution of the main pollutants are required. There is a direct association between the physicochemical speciation of an element and its bioavailability, toxicity and mobility. This article describesa distribution study of the metals Zn, Cd, Pb and Cu by speciation analysis of groundwater in six wells of the GuadiamarRiver Basin; the samples were taken several weeks after the spill. The speciation analysis resulted in the definition ofthree species categories: a) labile metal (H⁺ exchangeable),b) metal strongly associated to dissolved organic matter and c) metal associated with suspended material. Analysis was carried out by anodic stripping voltammetry (ASV). Metal speciation ingroundwater of the Guadiamar River Basin allows a differentiationbetween: on the one hand, metals from the mining spill, andon the other hand a less recent pollution from accumulatedinfiltration of either mining or agricultural origin, the last one due to an abuse of phytosanitary products.