Estimation of heavy metals (Cu,Zn, Pb) input into Punat Bay

The fate of heavy metals (Cu, Pb, Zn) from their sources to the final sink was analysed. Investigations included the identification of sources, the input from each source as well as transport towards their temporary (soil, vegetation, and marine water) and final sink (marine sediments). Research was conducted in the catchment area of Punat Bay on the island of Krk (Northern Adriatic, Croatia). Four sources were identified: long-range transport, traffic, antifouling paints and eroded material which annually introduced about 158 kg of Cu, 175 kg of Pb and 666 kg of Zn into the Bay. Antifouling paints were significant but not the main source of pollution in this area as was considered in previous investigations. Due to long-range transport, the input of Zn was almost four times greater, whereas the input of Pb was almost six times greater than the input from antifouling paints. Aerosols emitted from motor vehicles still represent the mayor source of Pb in this area. Cu originates mostly from antifouling paints and long-range transport. It was estimated that only around 30% of analysed elements introduced into the water column would be deposited in their final sink, i.e. marine sediments.     

Trace metals (Cd,Cu, Ni,and Zn) and nutrients in coastal waters adjacent to San Francisco Bay,California

Samples collected in December 1990 and July 1991 show that dissolved Cd, Cu, Ni, and Zn distributions in the Gulf of the Farallones are dominated by mixing of two end-members: (1) metal-enriched San Francisco Bay water and (2) offshore California Current water. The range of dissolved metal concentrations observed is 0.2–0.9 nmol kg^?1 for Cd, 1–20 nmol kg^?1 for Cu, 4–16 nmol kg^?1 for Ni, and 0.2–20 nmol kg^?1 for Zn. Effective concentrations in fresh water discharged into San Francisco Bay during 1990–1991 (estimated by extrapolation to zero salinity) are 740–860 μmol kg^?1 for silicate, 21–44 μmol kg^?1 for phosphate, 10–15 nmol kg^?1 for Cd, 210–450 nmol kg^?1 for Cu, 210–270 nmol kg^?1 for Ni, and 190–390 nmol kg^?1 for Zn. Comparison with effective trace metal and nutrient concentrations for freshwater discharge reported by Flegal et al. (1991) shows that input of these constituents to the northern reaches of San Francisco Bay accounts for only a fraction of the input to Gulf of the Farallones from the estuary system as a whole. The nutrient and trace metal composition of shelf water outside a 30-km radius from the mouth of the estuary closely resembles that of California Current water further offshore. In contrast to coastal waters elsewhere, there is little evidence of Cd, Cu, Ni, and Zn input by sediment diagenesis in continental shelf waters of California.     

Trace metals and organic compounds in sediment samples from the River Danube in Russe and Lake Srebarna (Bulgaria)

 In 1995 the contamination status of accumulated fine surface sediments and effluent material from the River Danube in Russe (Bulgaria) was analysed for trace metals (Hg, Cd, Pb, Cu, Zn, Cr, Ni, As), polycyclic aromatic hydrocarbons (PAH), polychlorinated biphenyls (PCB), hexachlorobenzene (HCB), 1,1,1-trichloro-2,2-bis [chlorophenyl] ethane (DDT), 1,1-dichloro-2,2-bis [chlorophenyl] ethylene (DDE), 1,1-dichloro-2,2-bis [chlorophenyl] ethane (DDD), and hexachlorocyclohexanes (α-, β-, γ- and δ-HCH) to achieve basic information about the River Danube in Bulgaria. The range of trace-metal levels came close to or below the intended quality criteria for the River Elbe in Germany. The only exceptions were Pb in a shipyard, exceeding the final criteria by a factor of 17, and Cr downflow from a metal factory. In one sample from a shipyard (D8) the highest trace metal concentrations were analysed in the fraction 125–2000 μm. The maximum measured PAH contents exhibited a contamination on the lower μg g^–1 d.w.-level (dry weight base), traces of PCBs, HCB and DDD/DDE were analysed in the ng g^–1 d.w.-range. DDT and HCHs were not detected in any sample. The trace-metal and organic-compounds level in sediments from Lake Srebarna (UNESCO-Biosphere Reserve) displayed completely background character. Received: 18 March 1997 · Accepted: 21 July 1998     

Environmental contamination of Zn,Cd, Ni,Cu, and Pb from industrial areas in Hamadan Province,western Iran

Eleven surface soil samples from calcareous soils of industrial areas in Hamadan Province, western Iran were analyzed for total concentrations of Zn, Cd, Ni, Cu and Pb and were sequentially extracted into six fractions to determine the bioavailability of various heavy metal forms. Total Zn, Cd, Ni, Cu and Pb concentrations of the contaminated soils were 658 (57–5,803), 125.8 (1.18–1,361), 45.6 (30.7–64.4), 29.7 (11.7–83.5) and 2,419 (66–24,850) mg kg⁻¹, respectively. The soils were polluted with Zn, Pb, and Cu to some extent and heavily polluted with Cd. Nickel values were not above regulatory limits. Copper existed in soil mainly in residual (RES) and organic (OM) fractions (about 42 and 33%, respectively), whereas Zn occurred essentially as RES fraction (about 69%). The considerable presence of Cd (30.8%) and Pb (39%) in the CARB fraction suggests these elements have high potential biavailability and leachability in soils from contaminated soils. The mobile and bioavailable (EXCH and CARB) fractions of Zn, Cd, Ni, Cu, and Pb in contaminated soils averaged (7.3, 40.4, 16, 12.9 and 40.8%), respectively, which suggests that the mobility and bioavailability of the five metals probably decline in the following order: Cd = Pb > Ni > Cu > Zn.     

Trace metals in surface seawaters and sediments from various habitats of the Red Sea coast of Yemen

The purpose of this study was to determine and assess the concentrations of trace metals in surface seawaters and sediments from different coastal habitats of the Red Sea coast of Yemen. Surface seawater and sediment samples were collected, treated and analyzed for cadmium, cobalt, manganese, chromium, lead, iron, nickel, copper, zinc and vanadium by the atomic absorption spectrometric analysis. The concentrations were high for cadmium, cobalt and lead and low or consistent with the natural background concentrations for the rest of the metals. However, the coastal habitats of the Red Sea coast of Yemen are still considered unpolluted, it is concluded that the cadmium cobalt and lead levels in surface seawaters are high and could have negative effects on marine life of the sites. Further studies are needed to characterize the sources fate, biogeochemical processes and impacts of these trace metals on coastal habitats and marine life of the region.     

Trace metals in sediments near offshore oil exploration and production sites in the Alaskan Arctic

Increased offshore development in the Alaskan Arctic has stimulated interest in assessing potential impacts to the environment before the onset of any adverse effects. Concentrations of trace metals in sediments are used in this paper to provide one sensitive indicator of anthropogenic inputs from offshore activity over the past several decades. Sediments in coastal waters of the western Beaufort Sea are patchy with respect to sediment granulometry, organic carbon content, and concentrations of trace metals. However, results for surface sediments and age-dated cores show that nearly all samples contain natural concentrations of Ag, Ba, Be, Co, Cr, Cu, Hg, Ni, Pb, Sb, Tl, V and Zn, with metal/Al ratios that have been constant for many decades. Metal concentrations for incoming river-suspended matter compare well with sediment metal values and, along with vertical distributions in sediments, show no discernible diagenetic impacts that distort the sedimentary record for metals, except for Mn, As and possibly Cd. Slightly elevated concentrations of Ba, Hg, Ag, Sb and Zn were observed in a total of eight instances or in only 0.7% of the 1,222 data points for metals in surface sediments.     

Geochemistry of Cu, Co, Ni, Zn, Cd and Cr in the surficial sediments of a tropical estuary, southwest coast of India: a granulometric approach

 Geochemical characteristics of six trace metals – Cu, Co, Ni, Zn, Cd and Cr – in the bulk sediment and sand, silt and clay fractions of a tropical estuary on the southwest coast of India have been studied and discussed. In bulk sediment, the trace metal concentration is controlled mainly by the textural composition of the sample. Mud, sandy mud and sandy silt register higher concentrations of trace metals than that in sand-dominant sediments. The granulometric partitioning studies also re-affirmed the role of particle size in enriching the trace metals. The silt and clay fractions exhibit 7–8 times the enrichment of Cu and Cd compared to that in sand. The enrichment factors of Zn, Cr, Ni and Co in the silt and clay fractions, compared to that in sand, are 5–6, 4–5, 2–5 and 2–3 times, respectively. The trace metals in the sand fraction, particularly Ni and Cr, exhibit strong positive correlation with the heavy mineral content of the samples. It clearly indicates a heavy mineral pathway to the trace metals in the sand fraction. Cu and Co in silt and clay fractions exhibit a marked decrease towards the high saline zones of the estuary. This is attributed to the desorption of Cu and Co from particulate phases during estuarine mixing. Contrary to Cu and Co, the content of Zn in the clay fraction shows a marginal increase towards the estuarine mouth. This could be explained by the influx of Zn-rich contaminant discharges from Zn-smelting industries located slightly north of the estuarine mouth. The released Zn will effectively be held in the lattices of the clay mineral montmorillonite, which also exhibits a marked increase towards the estuarine mouth. The anomalously high values of Cd in some places of the Central Vembanad estuary is attributed to the local pollution. Received: 10 July 1995 · Accepted: 3 June 1996     

Sources, input pathways, and distributions of Fe, Cu, and Zn in a Chesapeake Bay tidal freshwater marsh

Tidal freshwater marshes exist at the interface between watersheds and estuaries, and thus may serve as critical buffers protecting estuaries from anthropogenic metal pollution. Bi-weekly samples of newly deposited marsh sediments were collected and analyzed for Cu, Zn, and Fe concentrations over 21 months from July 1995 to March 1997 in five distinct habitats at the head of Bush River, Maryland. Bi-weekly anthropogenic metal enrichments ranged from 0.9–4.7. Anthropogenic excess metal loadings averaged over 1996 ranged from 6–306 and 25–1302 μg cm⁻² year⁻¹ between sites for Cu and Zn, respectively. Based on Fe-normalized trace metal signatures, Susquehanna River sediment does not significantly contribute to upper Bush River. Organic matter was found to dilute total metal concentrations, whereas past studies suggested organics enhance labile metal content. Analysis of metal input pathways shows that marsh metals are primarily imported from nearby subtidal accumulations of historic watershed material by tidal flushing. Received: 29 April 1999 / Accepted: 7 December 1999     

炼锌固体废渣中重金属(Pb、Zn)的存在状态及环境影响

利用XRD、TEM/EDS和连续提取实验研究了土法炼锌固体废渣中重金属的矿物学特征及不同粒度中重金属的相态分布特征。与通常发现的重金属一般富集在小粒径废渣中的情况不同,本工作所研究的废渣样品中大粒径废渣与细粒径废渣相似,甚至有更高的金属含量。化学形态研究表明,冶炼过程形成的矿物(或玻璃质)集合体和堆积后的风化过程形成的次生矿物是废渣中重金属存在的主要化学相。同时发现Pb的残渣态很少(0.39%～15.75%),而Zn的残渣态较高(14.3%～46.2%),这可能与冶炼工艺所形成较多Zn的硅酸盐矿物有关。尽管可交换态Pb、Zn在不同相态中的相对比例非常小(Pb0.03%～1.30%;Zn0.03%～3.30%),但其绝对含量却比一般土壤或沉积物要高(Pb1.5～385μg/g;Zn3～590μg/g)。由于重金属可交换态有比其他化学相态更高的活动性和生物可利用性,因此,对环境有较大的潜在影响。废渣样品的微束分析表明,Pb在废渣中见有金属Pb存在形式或呈纳米金属Pb颗粒包裹于其他矿物或铁合金及熔球集合体中。同时不排除有Pb的碳酸盐矿物存在的可能。而以硅锌矿Zn2(SiO4)、锰硅锌矿(Zn,Mn)2犤SiO4犦和纤维状的丝锌铝石Zn8Al4犤(OH)8(SiO4)5犦·7H2O等矿物形式存在以及Fe、Mn等的铝硅酸盐形式存在的Zn,可能是导致Zn的残渣态较高的原因。与连续提     

南极普里兹湾表层沉积物微量元素分布特征及其物源指示意义

利用电感耦合等离子体质谱仪测定了中国南极科考21~27航次期间获取的普里兹湾表层沉积物中Cu、Pb、Zn、Cd、Cr、Co、Al、Fe、Mn的含量,分析了普里兹湾微量元素的分布特征,结合沉积物粒度分布、生物硅含量,并利用富集系数和主成分分析的方法,探讨了微量元素的物源指示意义。研究结果表明:普里兹湾沉积物中的微量元素含量与南大洋其他海域具有很好的可比性。Cu、Zn、Cr、Co、Fe、Mn含量在陆坡深海区明显高于冰架边缘区和陆架区;Al、Pb含量在冰架边缘区较高;而Cd含量在陆架区相对较高。人类活动对普里兹湾沉积物中的微量元素没有明显的影响,南极大陆岩石风化产物和海洋生物源性沉降是其主要来源。冰架边缘区及陆架破折处P2-9站位的微量元素主要为岩源性输入。陆架区、陆坡深海区的微量元素Cu、Zn、Cr、Co、Fe、Mn明显受到生源性物质输入的影响。而普里兹湾沉积物中Cd则主要来源于硅藻的吸收利用及硅质软泥的富集。     

Test of experimental set-ups for electrodialytic removal of Cu, Zn, Pb and Cd from different contaminated harbour sediments

Electrodialytic removal of heavy metals from different harbour sediments was investigated. Electrodialytic remediation experiments in laboratory scale were made with calcareous and non-calcareous harbour sediments. Two different experimental set-ups were used for the study, one with stirring of the sediment slurry, the other without stirring. The removal of heavy metals was highest in the non-calcareous sediment, where 94% Cd, 91% Zn and 73% Cu were removed after 24 days. The highest removal obtained for the calcareous sediment was 81% Cd, 76% Zn, 75% Pb and 53% Cu after 21 days, with stirred sediment slurry. Electrodialytic experiments without stirring of calcareous sediment gave high removals (84% Zn, 58% Pb and 48% Cu), but there were problems with precipitations in the sediment, which limited the removal. The stirred experiments gave the highest removals of heavy metals and the voltage was the most stable in these experiments, and thus, the stirred set-up is the best choice for experimental set-up. The order in which the heavy metals were removed from the harbour sediments was Cd>Zn>Pb>Cu.     

Distribution of Cd,Pb, Zn and Cu and their chemical speciations in soils from a peri-smelter area in northeast China

An exploratory study on soil contamination of heavy metals was carried out surrounding Huludao zinc smelter in Liaoning province, China. The distribution of total heavy metals and their chemical speciations were investigated. The correlations between heavy metal speciations and soil pH values in corresponding sites were also analyzed. In general, Cd, Zn, Pb, Cu and As presented a significant contamination in the area near the smelter, comparied with Environmental Quality Standards for Soils in China. The geoaccumulation index showed the degree of contamination: Cd > Zn > Pb > Cu > As. There was no obvious pollution of Cr and Ni in the studied area. The speciation analysis showed that the dominant fraction of Cd and Zn was the acid soluble fraction, and the second was the residual fraction. Pb was mostly associated with the residual fraction, which constituted more than 50% of total concentration in all samples. Cu in residual fraction accounted for a high percentage (40–80%) of total concentration, and the proportion of Cu in the oxidizable fraction is higher than that of other metals. The distribution pattern of Pb and Zn was obviously affected by soil pH. It seemed that Pb and Zn content in acid solution fraction increased with increasing soil pH values, while Cd content in acid soluble fraction accounted for more proportion in neutral and alkaline groups than acidic one. The fraction distribution patterns of Cu in three pH groups were very similar and independent of soil pH values. And the residual fraction of Cu took a predominant part (50%) of the total content.     

Biogeochemistry of trace metals (Mn, Sr, Rb, Ba, Cu, Zn, Pb and Cd) in a river-wetland-lake system (Balaton Region, Hungary)

Mn, Sr, Ba, Rb, Cu, Zn, Pb and Cd concentrations have been measured seasonally in the water and deposited sediments of the system comprising: Zala river (main input) — Lakes Kis-Balaton 1 and 2 (small artificial lakes created in a former bay of Lake Balaton) — Keszthely bay (hypertrophic part of Lake Balaton). The concentrations of the trace elements together with pH, alkalinity, dissolved cations (Ca²⁺, Mg²⁺, Na⁺, and K⁺), dissolved inorganic ligands (Cl^–, SO₄ ^2–), particulate Al, Ca, inorganic and organic carbon are used to assess the contamination of the study area and biogeochemical processes controlling trace element concentrations. Thermodynamic speciation calculations have also been utilized to enhance our understanding of the system. In the sediments Rb, Ba, Cu and Zn concentrations were mainly controlled by the abundance of the aluminosilicate fraction. Strontium was mainly associated with the calcium carbonate fraction. The aluminosilicate fraction constitutes a major sink for Mn and Cd but the concentration of these elements are also strongly related to calcite precipitation. The main processes that control the dissolved distribution of trace elements in the Balaton system were: solid phase formation (carbonate) for Mn; coprecipitation with calcite for Sr, Ba, Rb and possibly Mn and Cd; adsorption/desorption processes (pH dependent) for Zn and Pb; solubilization of Mn and precipitation of Cd and Cu in reed covered wetland areas where anoxic conditions were probably existing during the warm season. A preliminary budget of atmospheric and river input to Lake Balaton has also been outlined. Although Lake Balaton, is subjected to anthropogenic inputs mainly from agricultural and domestic activities, their impact on trace element concentrations in the Balaton system is very limited due to the efficiency of removal processes (i.e. adsorption and co-precipitation) and to high sedimentation rates and strong sediment re-suspension. Anthropogenic inputs are only detected for Pb.     

Modeling the adsorption of Cd (II), Cu (II), Ni (II), Pb (II) and Zn (II) onto montmorillonite

The adsorption of five toxic metallic cations, Cd(II), Cu(II), Ni(II), Pb(II) and Zn(II), onto montmorillonite was investigated as a function of pH and ionic strength and a two-site surface complexation model was used to predict the adsorption data. The results showed that in the lower pH range, 3∼6 for Cd, Cu, Ni and Zn, and 3∼4.5 for Pb, the adsorption was greatly affected by ionic strength, while in the higher pH range, the adsorption was not. In the lower pH range, the metallic cations were mainly bound through the formation of outer-sphere surface on the permanently charged basal surface sites (≡X⁻), while in the higher pH range the adsorption occurred mainly on the variably charged edge sites (≡SOH) through the formation of inner-sphere surface complexes. Acid-base surface constants and metal binding constants for the two sites were optimized using FITEQL. The adsorption affinity of the five metallic cations to the permanently charged sites of montmorillonite was Pb > Cu > Ni ≈ Zn ≈ Cd, while that to the variable charged sites was Pb ? Cu > Zn > Cd > Ni.     

Comparative study of As,Cd, Cu,Cr, Mg,Mn, Ni,Pb and Zn concentrations between sediment and water from estuary and port

The contents of As, Cd, Cu, Cr, Mg, Mn, Ni, Pb and Zn have been determined in sediment and water samples from Valle de las Garzas estuary and Port Manzanillo (Colima, Mexico) using ICP-AES. The concentrations of these elements were used for a comparative study to determine the distribution of heavy metals and to evaluate which elements reflect natural or anthropogenic backgrounds. For this purpose, seven sampling points were selected: Four of them correspond to the lagoon, and three were situated in the port. Statistical analysis of the mineral content was assessed. Initially, data comparison was assessed by statistical tests for each variable. Principal component analysis was then applied considering the influence of all variables at the same time by obtaining the distribution of samples according to their scores in the principal component space. In this way, four studies were carried out: (1) study of sediments collected during the dry season; (2) study of sediments collected during the rainy season; (3) comparative study between sediments from rainy and dry season; and (4) study of water composition collected during rainy season. From the results of the performed analyses, it can be concluded that metals distribution pattern reflected natural and anthropogenic backgrounds (e.g., sediments from the lagoon, situated at the beginning of the rain channel, presented high contents of Zn and Cu, perhaps related to anthropogenic activities or the influence of igneous sediments).     

Anthropogenic components of heavy metal (Cd,Zn, Cu,Pb) budgets in the Lot-Garonne fluvial system (France)

Heavy metal (Zn, Cd, Cu and Pb) mass balances in the Lot-Garonne fluvial system have been established for 1999 and 2000. The mean annual discharges of these years are close to the mean discharge of the previous decade. The estimated annual dissolved and particulate fluxes in this model watershed integrate daily input from diffuse and point sources, diffusive fluxes at the water/sediment interface, changes in the dissolved-particulate partition and changes in sediment stock. Cadmium, Zn, Cu and Pb entering the Gironde estuary via the Garonne River (11–14 t a⁻¹ of Cd; 1330–1450 t a⁻¹ of Zn; 126–214 t a⁻¹ of Cu and 127–155 t a⁻¹ of Pb) are mainly transported in the particulate phase and the major part (i.e. ∼74 to 96% for Cd, ∼60% for Zn, ∼50 to 60% for Cu and ∼80% for Pb) is transported by the Lot River. The main anthropogenic heavy metal point source is located in a small upstream watershed (Riou-Mort River) accounting for at least 47% (Cd), ∼20% (Zn), ∼4% (Cu) and ∼7 to 9% (Pb) of the total heavy metal inputs into the Garonne River, although it contributes only 1% of the discharge. Mass balances for 1999 suggest that under mean annual hydrologic conditions on the basin scale, the heavy metal budget of the Lot-Garonne fluvial system is balanced and that the stocks of Cd [200 t; Environ. Tech. 16 (1995) 1145] and Zn in the Lot River sediment are constant under mean discharge conditions. Heavy metal input by molecular diffusion at the sediment surface represents an important component of dissolved metal inputs into the system (e.g. 30% for Cu). Except for Cu, these dissolved inputs are totally removed from solution by SPM. Based on the generally constant Zn/Cd (∼50) concentration ratio in sediment cores from the polluted Lot River reaches and the sediment stock of Cd [200 t; Environ. Tech. 16 (1995) 1145], the present day Zn stock in the Lot River sediments has been estimated at about 10,000 t. In addition to the mobilization of river-bed sediment and associated heavy metals by intense floods, local human activities, including river-bed dredging, may strongly modify the heavy metal budget of the river system. In 2000, the dredging-related remobilization of polluted Lot River sediment released 2–6 t Cd. This additional Cd point source was estimated to account for 15–43% of the gross inputs into the Gironde Estuary.     

Relationships Between Geochemical Parameters (pH, DOC, SPM, EDTA Concentrations) and Trace Metal (Cd, Co, Cu, Fe, Mn, Ni, Pb, Zn) Concentrations in River Waters of Texas (USA)

Water samples from eight major Texas rivers were collected at different times during 1997–1998 to determine the dissolved and particulate trace metal concentrations, expected to show differences in climate patterns, river discharge and other hydrochemical conditions, and human activities along the different rivers. Specifically, two eastern Texas rivers (Sabine, Neches) lie in a region with high vegetation, flat topography, and high rainfall rates, while four Central Texas rivers (Trinity, Brazos, Colorado, and San Antonio) flow through large population centers. Relatively high dissolved organic carbon (DOC) concentrations in the eastern Texas rivers and lower pH led to higher Fe and Mn concentrations in river waters. The rivers that flow through large population centers showed elevated trace metal (e.g., Cd, Pb, Zn) concentrations partly due to anthropogenically produced organic ligands such as ethylenediaminetetraacetic acid (EDTA) present in these rivers. Trace metal levels were reduced below dams/reservoirs along several Texas rivers. Statistical analysis revealed four major factors (suspended particulate matter [SPM], EDTA, pH, and DOC) that can explain most of the observed variability of trace metal concentrations in these rivers. SPM concentrations directly controlled particulate metal contents. Variation in pH correlated with changes of dissolved Co, Fe, Mn, and Ni, and particulate Mn concentrations, while DOC concentrations were significantly related to dissolved Fe concentrations. Most importantly, it was found that, more than pH, EDTA concentrations exerted a major control on dissolved concentrations of Cd and Zn, and, to a lesser extent, Cu, Ni, and Pb.     

ICP-MS测定土壤中的As、Cr、Pb、Se、Cu和Zn

本文用电感耦合等离子质谱法(ICP-MS)测定了土壤的As、Cr、Pb、Se、Cu和Zn6种微量元素的质量分数,以In作为内标进行基体效应的补偿,方法快速灵敏,回收率为92.4%～106.8%,相对标准偏差小于5.0%,结果达到国家标准要求。     

Zn, Pb, Cu and As distribution patterns in overbank and medium-order stream sediment samples: their use in exploration and environmental geochemistry

Overbank and medium-order stream sediment samples were collected in Belgium and Luxembourg from 66 sampling locations (area of about 33,000 km²) and analysed for major and trace elements among which Zn, Pb, Cu and As. At each sampling location large bulk samples were taken, namely in the lower (normally at ≥1.5 m depth, over an interval of about 20–40 cm) and upper (normally upper 5–25 cm) parts of the overbank profiles and from the stream sediments. Furthermore, at a number of these sites, a detailed geochemical analysis of vertical overbank sediment profiles (sampling intervals of 10–20 cm) was subsequently carried out to unravel element variations through time and to help in the overall evaluation. For most sampled sections evidences such as ¹⁴C-dating and the absence of anthropogenic particles point towards a pre-industrial and often pristine origin of the lower overbank sediment samples. From the latter bulk samples, mean background concentrations were deduced. They reveal the existence of significant differences between the northern and southern part of Belgium (incl. Luxembourg) which relate to the difference in geological substrate. In the north dominantly non-lithified Quaternary and Tertiary sands, marls and clays occur while in the south Palaeozoic sandstones, shales and carbonate rocks outcrop. Consequently separate mean background values were calculated for the two areas. In the southern study area, some anomalous metal concentrations have been recorded in pre-industrial sediments. They are derived from mineralised Palaeozoic rocks, a feature which could be of interest for base metal exploration. In the upper overbank and stream sediments, in general, higher heavy metal and As contents were recorded with highest values in areas with metal mining, metal melting and cokes treatment industries. By comparing the trace element concentrations of the upper overbank or stream sediment samples with the concentrations detected in the lower overbank samples at each of the sampling locations, and by evaluating the vertical distribution patterns where available, the degree of pollution of the alluvial plain and the present-day stream sediments can be assessed. From this exercise, it is clear that highest pollution occurs in the northern part of Belgium, which relates to its high population density and industrial development.     

Contamination by heavy metals (Cd, Zn, Cu, and Hg) of eight fish species in the Gironde estuary (France)

The Gironde estuary, one of the largest in Europe, is considerated as a reference ecological system, with all the western European diadromous fish species present. The national biomonitoring program on the coastal marine environment has revealed since 1979 severe metal pollution (mostly cadmium [Cd]) in oysters collected from the estuary. No data are available on metal contamination levels in fish, despite their ecological and economic importance. We present the results from a detailed study based on 4 metals (Cd, zinc [Zn], copper [Cu], and mercury [Hg]) measured in 4 organs (gills, dorsal skeletal muscle, liver, and kidneys) from 8 fish species illustrating several ecological combinations: European eel (Anguilla anguilla), twaite shad (Alosa fallax), bass (Dicentrarchus labrax), meagre (Argyrosomus regius), flounder (Platichthys flesus),, thin-lippid grey mullet (Liza ramada), sole (Solea vulgaris), and Canary drum (Umbrina canariensis). The results show very marked differences between species and organs, as well as very significant variations between the 4 metals. Although metal concentrations measured in fish muscle are low, except in the case of Hg for theA. fallax, high levels of Cu and Cd were observed in the kidneys and livers ofL. ramada andA. anguilla. A multifactorial analysis based on rank ordered metal concentrations for the 8 fish species clearly shows 4 clusters of species assigned to the different degrees of metal contamination, from the lowest contaminated (A. regius, D. labrax, S. vulgaris, andU. canariensis), to the most contaminated group (L. ramada). The most contaminated species (L. ramada, A. angailla, andP. flesus) are characterized by long residence times in the estuary, between 3.5 and 14 yr. ForL. ramada, biofilms with high metal storage capacities would be the principal uptake route; the two other species are benthic with a carnivorous regime. Comparisons between our data and four estuaries (Seine, France; Mersey, U.K.; La Plata, Argentina; Guadalquivir, Spain), on a limited number of common species, metals and fish organs, clearly reveal higher Cd bioaccumulation levels in the Gironde estuary.