Metal contamination of soils, sediments and dusts in the vicinity of marine leisure boat maintenance facilities

Purpose

Metal contamination arising from boat maintenance is a growing environmental concern. In this study, metals currently or historically employed in boat paints (Ba, Cu, Pb, Sn and Zn) have been determined in geosolids sampled from within and in the vicinity of two leisure boat maintenance facilities in south west England.

Materials and methods

Samples of dusts, sediments and soils from two boatyards and from various urban control sites were fractionated through 63 μm before being digested in boiling aqua regia. Metal concentrations were determined in sample digests by inductively coupled plasma spectrometry.

Results and discussion

Metal concentrations were highly variable in each medium but were greatest in boatyard dusts which, pre-fractionation, often contained visible particles of paint. Metal concentrations in sediments and soils were higher than concentrations in respective control samples and, in many cases, exceeded environmental quality standards or predicted effect concentrations. Observations are attributed to the heterogeneous contamination of geosolids by fine particulates of antifouling paint generated during boat maintenance and repair; specifically, particulates contaminate sediment via boatyard runoff (with rainfall and washdown water), while soil is contaminated through the deposition of fine, airborne paint dusts.

Conclusions

This study demonstrates that boat paint particles enriched in a variety of metals contaminate both coastal and terrestrial environments. Contamination arises from the removal and dispersion of dusts during boat maintenance. Stricter measures for the containment and disposal of wastes generated by boat repair and repainting are, therefore, recommended.     

Tin concentrations in river / bay sediments of Tokyo in 1984 and 2000

Abstract

To analyze in greater detail the fate and behavior of toxic organotin compounds in the environment, total tin (Sn) concentrations were determined for sediments of the Arakawa River, the Sumida River, and Tokyo Bay by using a graphite furnace atomic absorption spectrophotometer (GFAAS). Sn concentrations in 2000 were compared with those of 1984 (8 years before the regulation on tributyltin-based antifouling paint) as well as with other heavy metals (Cu, Ni, Pb, and Zn). The Sn concentrations ranged from 1.04 to 4.43 mg kg^?1 for sediments sampled in 2000. Although the average concentration of Sn in the sediments was low compared with that of 1984, the concentration tended to increase at several sites in 2000. Moreover, the Sn concentration showed significant correlations with the Cu, Ni, Pb, and Zn concentrations. These results suggest that a significant proportion of the overall Sn content in these sediments was probably introduced from the sources other than antifouling paint. The metals extracted from air-dried sediments with 0.1 m HCl showed that the mobility and bioavailability of Sn was low compared with those of other heavy metals.     

Levels and Bioaccessibilities of Metals in Dusts from an Arid Environment

The elemental composition and bioaccessibility of trace metals have been determined in a variety of geosolids (soils, road dusts and house dusts) from an arid, coastal region (Dhahran, Saudi Arabia). Concentrations of many elements reflected those of the local geology, ascertained by analysis of desert sand. Several trace metals (e.g. Cu, Sb, Zn, Pb, Tl and Sn) were moderately enriched in both road and house dusts, reflecting external and internal (household) anthropogenic sources. For a given trace metal, bioaccessibilities, assessed using a physiologically based extraction test, were broadly similar across the range of geosolids. Median values for a simulated gastric phase ranged from less than 10% (Ba, Cu, Cr, Ni and V) to more than 50% (As, Cd, Sb, Sn and Tl), and for a subsequently simulated intestinal phase from less than 15% (Ba, Cr, Cu, Ni, V and Zn) to more than 50% (As, Cd, Sb, Tl and U). Results suggest that the levels and bioaccessibilities of trace metals in dusts from arid environments are controlled by the dilution of anthropogenic particulates by variable (but significant) proportions of fine, baseline sand.     

Site-Specific Gastrointestinal Metal Variability in Relation to the Gut Content and Fish Age of Indigenous European Chub from the Sava River

This comprehensive field survey on indigenous European chub (Squalius cephalus L.) presents, for the first time, site-specific variability of trace metal concentrations in the gut content, gastrointestinal tissue and two gastrointestinal sub-cellular fractions, operationally defined as metal-sensitive fraction (S50, which was isolated at 50,000?×?g and contains total water soluble proteins), and metal detoxified fraction (heat-treated S50 (HT S50), which contains heat-stable proteins like metallothioneins). At five sampling sites along the Sava River in Croatia 1 to 5-year-old chub were collected in the post-spawning period (September) in order to estimate if metal concentrations in fish intestine are related to their levels in the gut content or fish age. Concentrations of essential metals (Zn, Fe, Cu, Mn) and non-essential Cd decrease in the gut content as follows: Fe > Mn > Zn > Cu > Cd, while in the gastrointestinal tissue: Zn > Fe > Cu ?? Mn > Cd. Observed difference in metal abundance between the gut content and gastrointestinal tissue points to the selective metal absorption in fish intestine. Relationship among metal concentrations in the gastrointestinal tissue and two sub-cellular fractions (S50/HT S50) is significant for all analysed metals, with Spearman correlation coefficients (r) at p?<?0.01 for Zn 0.84/0.73, Cu 0.73/0.73, Fe 0.62/0.58, Mn 0.81/0.78, Cd 0.81/0.82. Site-specific differences point to the age-related increase of gastrointestinal Cu, Mn and Cd towards the downstream sites, while significant correlation between metal concentrations in the gut content and fish age exists only for Mn. In the sub-cellular gastrointestinal fractions, site-specific differences were not recorded on total water-soluble protein and metallothionein concentrations, which might be ascribed to the constitutional level.     

Heavy metals in the lichen Caloplaca aurantia from urban,suburban and rural regions in Israel (a comparative study)

The content of eight heavy metals: Mn, Zn, Fe, Pb, Ni, Cu, Cr and Cd in the lichen Caloplaca aurantia growing on roof-tiles in urban, suburban and rural settlements in Israel has been evaluated. The data obtained and their statistical analysis indicated the following: (1) The content of all the above listed metals was generally higher in the lichen growing in ‘town’ than in ‘village’ areas; among these metals Ni and Zn were found most suitable for the distinction between ‘town’ and ‘village’ settlements. (2) Comparisons of the coefficient of variation of metal content values in ‘town’ versus ‘village’ furnished indications on the dispersion capacity of the metal particles. (3) Correlation analysis among the metals in ‘town’ and ‘village’ resulted in suggestive information on the emission sources. (4) Leaching tests indicated the tenacity of metal retainment and incorporation efficiency into the lichen tissue. Lichen species like C. aurantia, which grow both in ‘clean’ and metal contaminated areas are suggested as comparative monitors and for assessing periodical changes in metal output and concentrations.     

Toxicity and binding of copper,zinc, and cadmium by the blue-green alga,Chroococcus paris

The toxic effects and accumulation of the heavy metals, Cd, Cu, and Zn by the sheath forming blue-green alga Chroococcus paris were investigated. All three of the metals were bound rapidly. Approximately 90% of the total amount of the added metal was bound within 1 min. Further significant binding occurred at a slower rate. The maximum metal binding capacity, as determined by filtration studies, was determined to be 53, 120, and 65 mg g^?1 dry algal weight for Cd, Cu, and Zn, respectively. Binding curves for the metals followed the Langmuir adsorption isotherm model. The amount of metal bound increased with increasing pH. Metal binding increased significantly when pH was increased from 4 to 7. Nearly all of the metal was found to be rapidly EDTA extractable. Metals were found to be increasingly toxic to growing cultures in the order, Zn, Cd, and Cu. All of the metals studied exhibited toxic effects at concentrations greater than 1.0 mg L^?1. The lowest concentrations used which showed detectable toxicity were 0.1 mg L^?1 for Cu and >0.4 mg L^?1 for Cd and Zn.     

云南滇池沉积物中重金属的形态分布特征

Fractionation of heavy metals in sediments can help in understanding potential hazards of heavy metals. The present study analyzed total concentrations and fractions of selected heavy metals （Cd, Cr, Cu, Pb, and Zn） in surface sediments from Dianchi Lake, Yunnan Province, China, as well as factors that may affect distributions of the various heavy metal fractions. Total concentrations of the heavy metals decreased in the order Zn 〉 Cu 〉 Pb 〉 Cr 〉 Cd. These heavy metals, except Cr, were much higher than their background levels, indicating that Dianchi Lake was polluted by Cd, Zn, Pb, and Cu. Cadmium occurred mainly as the non-residual fraction （sum of the HOAc-soluble, reducible, and oxidizable fractions） （97.6%）, and Zn （55.7%） was also predominantly found in the non-residual fraction. In contrast, most of the Cr （88.5%）, Pb （81.8%）, and Cu （59.2%） occurred in the residual fraction. Correlation analysis showed that total heavy metal concentrations, organic matter and reducible Fe were the main factors affecting the distributions of the various heavy metal fractions. In the Walhai section of Dianchi Lake （comprising 97% of the lake area）, the concentrations of Cd, Zn, Pb, and Cu in the non-residual fraction were significantly lower （P ≤ 0.01 or 0.05） than those of the Caohal section （3% of the lake area）. This indicated that potential heavy metal hazards in the Caohai section were greater than the Waihai section.     

Heavy metal contamination and risk assessment of human exposure near an e-waste processing site

Environmental pollution due to uncontrolled e-waste recycling activities has been reported in a number of locations in China. In this study, heavy metal pollution from primitive e-waste processing facilities was investigated. The pollution is due to high concentrations of metals present in the surrounding soils and vegetables. The highest enrichment factor values due to e-waste wastewater and waste discharges were found at Anqiaotou Village and Beian Village. Vegetables from the vicinity of the e-waste processing sites were found to have higher heavy metal pollution index values in comparison with those from the background site. The bioaccessibilities of heavy metals were decreased in the order of Cd?>?Pb?>?Sn?>?Zn?>?Ni?>?Cr. The e-waste processing site was badly polluted by Cd, Pb, Zn, Ni and Cr, with its pollution level decreased in the following order: Cd?>?Pb?>?Cr?>?Ni?>?Zn?>?Sn. Additionally, the greatest risk among six metals in the e-waste processing areas is caused by Cd and Pb. The risks associated with the consumption of contaminated vegetables grown in e-waste processing regions may be a potential health concern.     

Forms of Cu,Ni, and Zn in soils of sudbury,ontario and the metal concentrations in plants

Forms of Cu, Ni, and Zn in the contaminated soils of the Sudbury mining/smelting district were studied to assess metal mobility and plant availability. Soil, tufted grass (Deschampsia caespitosa (L.) Beauv.), tickle grass (Agrostis scabra Willd.), dwarf birch (Betula pumila L. var. glandulifera Regel) and white birch (Betula paprifera Marsh.) leaf and twig samples were taken from 20 locations around three Cu-Ni smelters. The sampling sites were collected to cover a wide range of soil pH and soil Cu and Ni concentrations. The water-soluble, exchangeable, sodium acetate-soluble, and total concentrations of the metals in the soils were analyzed. The soils were contaminated with Cu and Ni up to 2000 µg g^?1. Zinc concentrations were also elevated in some samples above the normal soil level of 100 µg g^?1. The mobility of Cu and Zn, expressed as the proportion of metals in Fl and F2 forms, increased with soil pH decrease. A strong positive correlation was found between the soil exchangeable (F2) Ni and the soil pH. Concentrations of Cu and Ni in birch twigs showed a good linear relationship with exchangeable forms of the metals in soils. A highly significant correlation was also found between total Ni in soils and the metal content of the twigs. No significant correlation was found between Zn concentrations in the soils and plants. Birch twigs are a good indicator (better than leaves) of Cu and Ni contamination of the Sudbury soils. The mobile forms of Cu and Ni and low pH seem to be the main factors that will control the success of revegetation. Strong variability of the soil metal mobility requires any reclamation effort be site-specific.     

Gastropod Assemblages as Indicators of Sediment Metal Contamination in Mangroves of Dumai, Sumatra, Indonesia

Impacts of heavy metal concentrations in sediments on the gastropod community structure were assessed in the coastal waters of Dumai, Sumatra, Indonesia. The objective of this study was to relate the levels of heavy metal pollution with the changes of gastropod community structure in the study area. Concentrations of Cd, Cu, Pb, Zn, Ni, and Fe in surface sediments collected from five sampling stations were analyzed and correlated with the abundance, species richness, and diversity of gastropod populations. Sediments at stations with more anthropogenic activities accumulated higher concentrations of heavy metals and consequently displayed lower abundances, lower species richness and diversity; while stations with lower heavy metal concentrations in sediments showed the opposite pattern in gastropod community metrics. The above findings are complemented by significant negative correlations p?<?0.05–0.01) between concentrations of Cd, Cu, Pb, Zn, and Ni in the sediments and gastropod abundance and species richness. Among the metals analyzed, Cu and Zn had strongest negative correlations with the gastropod diversity which suggests that these metals may be the most detrimental to gastropod populations in the mangrove area of Dumai coastal waters.     

Evaluation of Heavy Metal Pollution in the Arabian Gulf Using the Clam Meretrix meretrix Linnaeus, 1758

The present study is an attempt to assess the heavy metal contamination in the marine environment of the Arabian Gulf of Saudi Arabia. The concentrations of heavy metals in water and the soft tissues of the bivalve species Meretrix meretrix Linnaeus, 1758, from different stations along the Arabian Gulf coastline, were determined during the summer season of 2008. Bioaccumulation of some heavy metals (Cd, Pb, Cu, and Zn) in fresh parts of the clam (M. meretrix) was measured by an atomic absorption spectrophotometer. The average concentrations of heavy metals in the clam tissues were 0.224?C0.908, 0.294?C2.496, 3.528?C8.196, and 12.864?C24.56 mg/kg wet weight for Cd, Pb, Cu, and Zn, respectively. In water, the mean concentration values of these metals were arranged in the following descending order: Pb > Cu > Zn > Cd. The heavy metal concentrations in tissues of M. meretrix were within the acceptable standards set by the US Environmental Protection Agency, the Commission Européenne, and the Food and Drug Administration of the USA. From the human public health point of view, these results seem to show no possibility of acute toxicities of Cd, Cu, Pb, and Zn if the edible clam is consumed. It is recommended that relevant authorities should carry out a continual assessment on the levels of these pollutants in the studied area.     

Mikrosondenuntersuchungen an unterschiedlich stark mit Schwermetallen belasteten Böden. 2. Gehalte an Schwermetallen und anderen Elementen in Huminstoffaggregationen,Streustoffen und Holzkohlepartikeln

Electron microprobe studies on soil samples with varying heavy metal contamination. 2. Contents of heavy metals and other elements in aggregations of humic substances, litter residues and charcoal particles EMA point analysis show that the organic matter constituents of heavy metal contaminated soils are highly enriched with heavy metals. The maximal trace element accumulation were for Cu up to 13,000 mg/kg, for Zn up to 48,000 mg/kg, for Cd up to 2,100 mg/kg and for Pb up to 193,000 mg/kg. The affinity for the accumulation of the different heavy metals in aggregations of humic substances can be described by the sequence Cu > Pb ? Cd > Zn ? Ni > Co. In very strongly acidified humic top soil horizons the Pb and Cd accumulation in the organic matter constituents is in competition with the accumulation in Fe and Mn oxides. The heavy metal contents (especially of Cu) of the organic matter are often correlated with the content of organically bound calcium. The EMA results also show that high heavy metal amounts occur in combination with Ca-accumulations in the epidermis and the outer bark parenchym of decayed roots. EMA point analysis of the interior of fungus sclerotias show that sclerotias can contain high amounts of heavy metals, in particular lead (up to 49,700 mg Pb/kg). From statistical results of EMA point analysis follows that lead and other heavy metals attached to humic substances are not only bound as metal organic complexes but also as organic metal phosphate complexes. Also charcoal particles of polluted soils contain high amounts of heay metals. The accumulation affinity is quite similar to that of humic substances.     

Reference concentrations for heavy metals in mineral soils, oat, and orchard grass (Dáctylis glomeráta) from three agricultural regions in Norway

Background values for heavy metals are necessary for the assessment of metal pollution of soils and plants. Samples of cultivated and uncultivated soils, oat grain, and seed heads of orchard grass (Dáctylis glomeráta) were collected from central, southeastern, and southwestern Norway. Total and easily extractable concentrations of As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn were determined in soil samples and total concentrations in plant samples. Element distributions have been correlated with petrology of soil parent material, type of mineral deposit, soil depth, geographic area, and land use. Concentrations of heavy metals are generally within the lower part of the normal global range. The petrology of the soil parent material has the greatest influence on aqua regia extracted metal concentrations among the factors studied. DTPA extracted metals show less dependence on rock types. Presence of alum shale results in particularly high values for Cd in both soil extracts and in oat grain. Soil cultivation seems to influence the relative concentration of metals in the topsoil. The ratios of easily extractable to total concentrations of metals are primarily related to the organic matter content. Metal concentrations in oat grain can best be predicted by concentrations in DTPA extracts and soil pH among the factors studied. Seed heads of orchard grass are less affected by concentrations in the soil and appear therefore to be a poor indicator of heavy metals in soils.     

Population size of indigenous Rhizobium leguminosarum biovar trifolii in long-term field experiments with sewage sludge cake,metal-amended liquid sludge or metal salts: Effects of zinc,copper and cadmium

There is conflicting evidence, and therefore continuing concern, as to whether metals in sewage sludge are deleterious to soil microbial processes and long-term agricultural productivity. Nine field experiments with sewage sludge cakes, three with metal-amended liquid sludges and three with inorganic metal salts were set up across Britain in 1994 to give individual metal dose–response treatments to try to answer this question. This study reports on the effects of Zn, Cu and Cd on the population size of Rhizobium leguminosarum biovar trifolii, a nitrogen fixing symbiont of white clover (Trifolium repens), in soils from these experiments over 11 years. Significant (P < 0.05) reductions in indigenous rhizobial numbers occurred on the Zn metal dose–response treatments at eight of the sludge cake sites in 2005, but few consistent effects were evident on the Cu or Cd metal dose–response treatments during the 11-year monitoring period. The soil total Zn concentrations where effects occurred were near to the UK statutory limit of 300 mg kg^?1 for soils receiving sewage sludge. No significant reductions occurred in any treatments on the metal-amended liquid sludge or inorganic metal salt experiments in which the metals would be expected to be in a more bioavailable form, even after 11 years. The effects in the sludge cake experiments were related consistently with soil total Zn, with no recovery to date. The reductions in clover rhizobial numbers in the sludge cake experiments were due to Zn effects on free-living rhizobia in the soil, with gradual die-off over a long time with increasing soil total Zn concentrations. Currently, no consistent adverse effects on rhizobia have been seen at the UK limits for Cu and Cd of 135 and 3 mg kg^?1, respectively.     

Trace metal composition and speciation in street sediment: Sault Ste. Marie,Canada

Street sediment collected in Sault Ste. Marie, Ontario was examined for trace element composition (As, Cd, Cr, Cu, Fe, Pb, Hg, Ni and Zn) and the metal partitioning to various sediment properties was determined by sequential extraction. Total Ni, Cu, Zn and Pb concentrations exceeded the lowest effect levels specified in the Ontario Provincial Sediment Quality Guidelines for Metals (Environment Ontario, 1992) and derived from bioassay studies. According to these Guidelines, the disposal of such sediment has to be guided by environmental considerations. A significant fraction of these metals was extractable in 0.5 N HCl over a 12-hour period and considered as potentially bioavailable. The major accumulative phases of toxic metals in this sediment are exchangeable, carbonate, Fe/Mn oxides and organic matter but the relative importance of each phase varied for individual metals. Approximately 20% of the total extractable Cd is found in each of these four fractions. Pb, Zn and Mn are predominantly bound to carbonates, Fe/Mn oxides and organic matter. Cu shows a high affinity for organic matter and to a lesser extent for carbonates. Elevated levels of Cd, Pb, Cu, Zn, Mn and Cr in the exchangeable and/or soluble phase suggest that sediment associated metals, mobilised from streets in Sault Ste. Marie during runoff and snowmelt, would adversely impact water quality in the receiving waters. However, large fractions of the total metal load are associated with coarser particles which are unlikely to be transported through the drainage system into receiving waters.     

Efficient Purification of Heavy-Metal-Contaminated Water by Microalgae-Activated Pine Bark

Batch experiments were performed to study metal sorption by pine bark and algae-treated bark. The biosorption of copper (Cu), lead (Pb), zinc (Zn), cadmium (Cd), cobalt (Co), and nickel (Ni) in synthetic multimetal aqueous solutions was studied as a function of metal content in solution, and amount and size of bark particles used for sorption. Influence of water hardness (Ca²⁺ only was tested) on the metal sorption process was also evaluated. Metal uptake from solutions with high heavy metal content (i.e. 10× the limit for leachate from landfills) was found to be independent of Ca²⁺ concentration. At low metal content in solution (i.e. 1× the limit for leachate from landfills), uptake of Cu, Zn, Ni, and Cd decreased with increasing Ca²⁺ content in water. Microalgae-treated bark was found to increase the metal sorption efficiency. Air-drying of bark-entrapped algae was shown to be the best method for sorbent drying. In general, the green algae, Chlorella sp. and Pseudokirchneriella subcapitata showed the best results in metal uptake. Sorption of Co, Zn, Ni, and Cd from solution with high levels of both heavy metals and calcium increased by almost 50% with algae treatment of bark was applied. At low levels of metals and calcium content, 100% uptake of Cu and Pb in water was observed. Uptake of other metals from solution with low metal and Ca content was relatively high (50–60%). Low pH (pH 3.0) had no influence on metal sorption from solutions with high metal content. For solutions with low metal content a decrease of metal uptake by 10–15% was observed for all the metals but Pb. Thus, the treatment of bark with microalgae was successful and influenced positively the uptake capacity of the bark.     

重金属复合处理对小麦锌铜镍镉积累和分布的影响

为增加粮食可食用部分有益元素的浓度,同时减少有毒重金属元素的含量,需要更好地了解元素在植株和籽粒内的运输和分布。在温室盆栽条件下,以春小麦为供试材料,设置对照（不添加重金属）和重金属复合处理（同时添加铜、锌、镍、镉,以不影响小麦生长为前提）,研究锌（Zn）、铜（Cu）、镍（Ni）、镉（Cd）在成熟植株和籽粒不同部位的分布特点。结果表明,重金属复合处理对小麦成熟期籽粒和秸秆产量、收获指数以及粒重均无显著影响,但使小麦各器官重金属浓度均显著增加,增幅因不同器官和不同元素而异,籽粒中Zn、Cu、Ni和Cd浓度分别增加1.8、0.5、48.1倍和45.3倍。重金属复合处理还显著改变了Zn和Ni在地上部各器官中的分配模式：对照小麦吸收的Zn更易向生殖器官中转运,处理植株则更多地滞留在营养器官中,而Ni呈相反的趋势。激光剥蚀电感耦合等离子体质谱仪（LA-ICP-MS）对籽粒糊粉层和胚乳的定量分析表明,重金属复合处理使糊粉层Zn和Cu浓度仅增加了78%和86%,而糊粉层Ni和Cd浓度分别增加了30倍和121倍。重金属复合处理使胚乳Zn和Cu浓度分别增加了49%和48%,使Ni和Cd浓度均超出小麦标准中Ni和Cd的最大允许浓度（对照籽粒胚乳中没有检验到Ni和Cd）。以上结果表明,在小麦生物强化实践中,在增加有益营养元素（如Cu和Zn）的同时亦存在有毒重金属（如Ni和Cd）超标的巨大风险。     

Effect of biosolid application to Mollisol Chilean soils on the bioavailability of heavy metals (Cu,Cr, Ni,and Zn) as assessed by bioassays with sunflower (Helianthus annuus) and DGT measurements

Purpose

This study assessed the effect of biosolid application on the bioavailable fraction of some trace elements (Cu, Cr, Ni, and Zn) using a bioassay with sunflower (Helianthus annuus) and a chemical assay, diffusion gradient in thin films (DGT).

Materials and methods

Five surface soil samples (0–20 cm) were collected from an agricultural zone in Central Chile where biosolids are likely to be applied. Municipal biosolids were mixed with the soil at concentrations of 0, 30, 90, and 200 Mg ha^?1. The experiment to determine the bioavailability of metals in the soil using the bioassay was performed using sunflower. The DGT technique and Community Bureau of Reference (BCR) sequential extraction were used to determine the bioavailable fractions of the metals.

Results and discussion

The application of biosolids increased the phytoavailability of Zn, Ni, and Cr in most of the soils, as indicated by the increasing concentrations in sunflower plants as the biosolid application rate increased. In two of the soils, Codigua and Pelvín, this increase peaked at an application rate of 90 Mg ha^?1. Decreases in the bioavailable fractions of Zn, Ni, and Cr were observed with higher biosolid application rates. The bioavailability of metals was estimated through multiple linear regression models between the metals in the sunflower plants and the different chemical fractions of metals in the soils treated with different biosolid rates, which displayed a positive contribution of the labile (water soluble, carbonate, and exchangeable), oxide, and organic metal forms in the soil, particularly with respect to Ni and Zn at application rates of 30 and 90 Mg ha^?1. The bioavailable fraction of metals was determined in soils using the DGT technique. The effective concentration (C _E) results were compared with those in sunflower plants. The DGT technique could effectively predict the bioavailable fractions of Cr, Ni, and Zn in the Taqueral soil but only that of Zn in the Polpaico soil.

Conclusions

The application of biosolids significantly increased the labile fraction of most of the metals in the studied soils, particularly at the highest biosolid application rate. C _E increased as the concentration of biosolids increased for most of the metals. The effectiveness of the DGT technique for predicting the bioavailability of metals was dependent on the soil type and the metal. However, the C _E for soil Cu was not related to plant Cu for all soils studied.     

Co-tolerance to zinc and copper of the soil nitrifying community and its relationship with the community structure

Soil microbial communities can develop trace metal tolerance upon soil contamination with corresponding metals. A few studies have reported co-tolerance in such cases, i.e. tolerance to other metals than those to which the microbial community had been exposed to. This study was set-up to test for co-tolerance of nitrifying communities to zinc (Zn) and copper (Cu) and to relate tolerances to shifts in community structure using amoA AOB (ammonia oxidizing bacteria) DGGE. Seven sets of soils, each representing a Cu or Zn contamination gradient were sampled from four locations. At two locations, both Cu and Zn had been added as single contaminants. Increased Zn and Cu tolerance of the nitrifying communities was consistently observed in response to corresponding soil contamination. Co-tolerance to Zn was obtained in two of the three Cu gradients and that to Cu in one of the four Zn gradients. DGGE analysis and sequencing showed that contamination with either Zn or Cu selected for identical AOB phylotypes in soils at one location but not at the other location. The nitrifying community structures in soils from different locations did not become more similar upon Zn exposure than those in corresponding uncontaminated soils. Hence, trace metal tolerance development was not due to the emergence of specific AOB phylotypes, but due to the emergence of different AOB phylotypes bearing tolerance mechanisms for Zn, Cu or both metals.     

Interactive Effects of Copper, Cadmium and Lead on Zinc Accumulation in the Gastropod Mollusc Littorina Saxatilis

The effects of copper, cadmium and lead on the bioaccumulation of zinc were studied in populations of the gastropod mollusc Littorina saxatilis from sites in the Isle of Man subjected to varying degrees of mine-related metal contamination. Exposures to 2 mg/L Zn alone and in combinations with 0.01 mg/L, 0.1 mg/L and 1 mg/L of the respective metals were conducted at ～10 ^°C in semi-static assays. Copper had a significant antagonistic effect on Zn accumulation at 1 mg/L Cu, but was not antagonistic at 0.01 and 0.1 mg/L Cu. Prior exposure to metals in the field did not appear to affect the interactive effect of copper as all populations showed similar patterns. Combinations of Zn with Cd or Pb at the above concentrations did not show any significant effects on Zn accumulation. On the other hand, Zn had an antagonistic effect on Cd and Pb accumulation but showed inconsistent effects on Cu accumulation. Interactions of Cu and Zn in particular may have repercussions for interpretation of biomonitoring data in L. saxatilis.