Effects of acidification on the availability of toxic metals and calcium to wild birds and mammals

The effects of acidification on wildlife inhabiting aquatic or semi-aquatic environments are reviewed, with particular reference to the possibility for increased dietary exposure to Hg, Cd, Pb and/or Al, and decreased availability of essential dietary minerals such as Ca. It is concluded that: (1) piscivores risk increased exposure to dietary methyl-Hg in acidified habitats, and Hg concentrations in prey may reach levels known to cause reproductive impairment in birds and mammals; (2) piscivores do not risk increased exposure to dietary Cd, Pb or Al because these metals are either not increased in fish due to acidification, or increase are trivial from a toxicological perspective; (3) insectivores and omnivores may, under certain conditions, experience increased exposure to toxic metals in some acidified environments. Exposure levels are likely to be sufficiently low, however, that significant risks to health or reproduction are unlikely. More importantly, these wildlife species may experience a drastic decrease in the availability of dietary Ca due to the pH-related extinction of high-Ca aquatic invertebrate taxa (molluscs, crustaceans). Decreased availability of dietary Ca is known to adversely affect egg laying and eggshell integrity in birds, and the growth of hatchling birds and neonatal mammals. Acidification-related changes in the dietary availability of other essential elements, such as Mg, Se and P, have not been established and require further investigation; (4) herbivores may risk increased exposure to Al and Pb, and perhaps Cd, in acidified environments because certain macrophytes can accumulate high concentrations of these metals under acidic conditions. The relative importance of pH in determining the metal concentrations of major browse species, and the toxicological consequences for herbivores wildlife, is not well established and requires further study. A decreased availability of dietary Ca is also likely for herbivores inhabiting acidified environments.     

Factors affecting trace-metal bioaccumulation in Finnish headwater lakes

Fourteen unpolluted Finnish headwater lakes with pH values varying from 4.8 to 7.0 were studied for trace-metal concentrations in water, sediment, aquatic plants (Nuphar luteum L., Sparganium sp.), aquatic insect larvae (Limnophilus sp., Phryganea sp.) and fish (Esox lucius L., Perca fluviatilis L., Coregonus sp., Salvelinus fontinalis L., Salmo trutta L.). Trace-metal deposition was estimated by analysing the snowpack. Non-parametric correlation analysis was carried out between trace metal concentrations in biota and pH, ANC, TOC, CA + Mg concentration in water and a given metal concentration in water and sediment. Bioaccumulation of several trace metals increased with increasing acidity and decreasing ANC in water. This was especially true for Pb and Cd. Aquatic plants were, in general, the best indicator group concerning differences in trace-metal bioaccumulation in lakes with different acidity. There was some evidence that a higher concentration of TOC in water may reduce bioaccumulation of Pb, Cd and Zn in aquatic plants and fish. The copper concentration in sediment was the only background variable explaining Cu concentration in aquatic insects. Multivariate analysis of the whole background data gave comparable preliminary results. Over 80% of the trace metal concentrations in biota of different lakes was explained by the background variables. In general, elevated concentrations of most of these trace metals can be expected to occur in the biota of acidified low calcareous lakes.     

Profile of trace elements in Parasol Mushroom (Macrolepiota procera) from Tucholskie Forest

The aim of this study was to determine 19 elements contents and bioconcentration potential in fruiting bodies of Parasol Mushroom (Macrolepiota procera) collected from the Tucholskie Forest complex in Poland. Also discussed were Cd, Pb and Hg contents of edible caps in relation to the current regulatory standards. K, P and Mg were particularly abundant in caps and stipes, median values were 38-49, 13, and 1.6-1.6 mg/g dry weight, and followed by Ca, Na and Rb at 110-540, 44-240 and 20-50 μg/g dw, respectively. Concentrations of Al, Fe, Zn, Cu and Mn were from less than 50 to 180 μg/g dw, while concentrations of other elements were ～l.0?μg/g dw or less. Cu, K, Ag, Cd, Na, Rb, Zn and Hg were bioconcentrated (BCF >1), while Al, Ba, Fe, Mn, Co, Sr, Pb and Cr were not bioaccumulated (BCF <1). Cd and Pb content of Parasol Mushroom's edible caps collected from some sites in the Tucholskie Forest exceed the maximum levels set in the EU for cultivated mushrooms.     

Biosorption of heavy metals using rice milling by-products. Characterisation and application for removal of metals from aqueous effluents

The morphological characteristics as well as chemical composition of rice husks were evaluated by different techniques such as spectroscopy and thermogravimetry. The material, which is considered a by-product obtained from rice milling, was then investigated as a potential decontaminant of toxic heavy metals present in laboratory effluents. Studies using glass columns were carried out at room temperature employing 100 ml of synthetic solutions containing Cd(II) and Pb(II) at 100 mg l(-1) in order to study the effects of pH, flow rate and particle size on Cd(II) and Pb(II) adsorption. After establishing the optimised conditions, the potentiality of rice husks for removing Cd(II) and Pb(II) ions from 100 ml of laboratory effluent, presenting concentrations before treatment of 22 and 12 mg l(-1), respectively, was evaluated. The ability to take up other metals species, such as Al(III), Cu(II) and Zn(II), present in this effluent was also studied. According to the data obtained, under the optimised conditions (pH=4.0, flow rate of 8.0 ml min(-1) and < or =355 microm rice husk particle size), 30 g of husks were necessary to attain the permissible limits for effluent release, as recommend by the EPA, for those species evolved in this work (Al, Cd, Cu, Pb and Zn).     

Transfer and effects of cadmium in an experimental food chain involving the snail Helix aspersa and the predatory carabid beetle Chrysocarabus splendens

The transfer and the toxic effects of Cd were studied in an experimental food chain involving the snail Helix aspersa as prey organism and one of its natural predators, the carabid beetle Chrysocarabus splendens. Juvenile snails were fed plant-based food enriched with 0, 10, 50 and 100 microg g(-1) of Cd, then were offered as prey to beetle larvae from egg hatching to pupation stage. Cd concentrations in snail tissues increased with increasing Cd concentration in food and with duration of exposure. Bioaccumulation factors ranged from 1.87 to 3.39, showing that H. aspersa snails, even in their early life stages, belong to macroconcentrator species for Cd. No significant reduction of snail consumption by beetles was found in exposed groups. Cd concentrations in beetle larvae remained very low (lower than 1 microg g(-1) for all groups), demonstrating a very effective regulation capacity in beetle larvae. However, Cd concentrations in highest exposed groups were higher than those found in control groups. Cd contents in adult beetles were lower than in larvae, showing a loss of Cd during metamorphosis. Despite the low Cd concentrations found in beetles, their exposure to Cd contaminated snails led to 31% of mortality, which occurred only during pupation and for the highest exposure level. No clear sublethal effects were found. These results showed that snails inhabiting heavily polluted areas may represent a risk of secondary poisoning for predatory invertebrates and provided quantitative data on the transfer of Cd between two compartments of a terrestrial food chain.     

Habitat type-based bioaccumulation and risk assessment of metal and As contamination in earthworms, beetles and woodlice

The present study investigated the contribution of environmental factors to the accumulation of As, Cd, Cu, Pb and Zn in earthworms, beetles and woodlice, and framed within an exposure assessment of the European hedgehog. Soil and invertebrate samples were collected in three distinct habitat types. Results showed habitat-specific differences in soil and invertebrate metal concentrations and bioaccumulation factors when normalized to soil metal concentration. Further multiple regression analysis showed residual variability (habitat differences) in bioaccumulation that could not be fully explained by differences in soil metal contamination, pH or organic carbon (OC). Therefore, the study demonstrated that in bioaccumulation studies involving terrestrial invertebrates or in risk assessment of metals, it is not sufficient to differentiate habitat types on general soil characteristics such as pH and/or OC alone. Furthermore, simple generic soil risk assessments for Cd and Cu showed that risk characterization was more accurate when performed in a habitat-specific way.     

Metal bioaccumulation and metallothionein concentrations in larvae of Crassostrea gigas

Larval stages of bivalve molluscs are highly sensitive to pollutants. Oysters from a hatchery from Normandy (English Channel) were induced to spawn, and fertilized eggs were exposed to copper or cadmium for 24 h. Metal accumulation (from 0.125 to 5 microg Cu L(-1) and from 25 to 200 microg Cd L(-1)) and MT concentrations were measured in larvae. Compared to controls, larvae accumulated copper and cadmium with an increase in MT concentrations particularly with cadmium (i.e. 130.96 ng Cu (mg protein)(-1) and 12.69 microg MT (mg protein)(-1) at 1 microg Cu L(-1) versus 23.19 ng Cu (mg protein)(-1) and 8.92 microg MT (mg protein)(-1) in control larvae; 334.3 ng Cd (mg protein)(-1) and 11.70 microg MT (mg protein)(-1) at 200 microg Cd L(-1) versus 0.87 ng Cd (mg protein)(-1) and 4.60 microg MT (mg protein)(-1) in control larvae). Larvae were also obtained from oysters of a clean area (Arcachon Bay) and a polluted zone (Bidassoa estuary) and exposed to copper in the laboratory, their MT concentration was measured as well as biomarkers of oxidative stress. Biomarker responses and sensitivity to copper for the larvae from Arcachon oysters were higher than for those from Bidassoa.     

Characterization and spatial distribution of heavy metals in sediment from Cedar and Ortega rivers subbasin

The Cedar and Ortega rivers subbasin is a complex environment where both natural and anthropogenic processes influence the characteristics and distributions of sediments and contaminants, which in turn is of importance for maintenance, dredging and pollution control. This study investigated the characteristics and spatial distribution of heavy metals, including lead (Pb), copper (Cu), zinc (Zn) and cadmium (Cd), from sediments in the subbasin using field measurements and three-dimensional kriging estimates. Sediment samples collected from three sampling depth intervals (i.e., 0-0.10, 0.11-0.56 and 0.57-1.88 m) in 58 locations showed that concentrations of Pb ranged from 4.47 to 420.00 mg/kg dry weight, Cu from 2.30 to 107.00 mg/kg dry weight, Zn from 9.75 to 2,050.00 mg/kg dry weight and Cd from 0.07 to 3.83 mg/kg dry weight. Kriging estimates showed that Pb, Cu and Cd concentrations decreased significantly from the sediment depth of 0.10 to 1.5 m, whereas Zn concentrations were still enriched at 1.5 m. It further revealed that the Cedar River area was a potential source area since it was more contaminated than the rest of the subbasin. Comparison of aluminum (Al)-normalized metal concentrations indicated that most of the metals within the top two intervals (0-0.56 m) had concentrations exceeding the background levels by factors of 2-10. A three-dimensional view of the metal contamination plumes showed that all of the heavy metals, with concentrations exceeding the threshold effect level (TEL) that could pose a threat to the health of aquatic organisms, were primarily located above the sediment depth of 1.5 m.     

Self-organizing feature map (neural networks) as a tool in classification of the relations between chemical composition of aquatic bryophytes and types of streambeds in the Tatra national park in Poland

Concentrations of the elements Al, Be, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Ni, Pb and Zn were measured in the aquatic bryophytes Fontinalis antipyretica, Platyhypnidium riparioides and Scapania undulata. These bryophytes were sampled from streams flowing through granites/gneisses, limestones/dolomites and sandstones in the Tatra national park in Poland. The Self-organizing feature map (SOFM) or Kohonen network was used to classify the bryophytes according to the concentrations of the elements. This method was verified using principal component analysis (PCA) to check whether this well-known technique would give similar results. Both the self-organizing map and ordination by PCA yielded distinct groups of aquatic bryophytes growing in streams flowing through different types of rock, groups which differed significantly in the concentrations of certain elements. Bryophytes from granites/gneisses were distinguished by higher concentrations of Cd and Pb, while those from sandstones had a higher concentration of Cr and those from limestones/dolomites had higher concentrations of Ca and Mg. The SOFM and PCA ordinations thus yield identical classifications of bryophytes from the Tatra mountains streams.     

Metals in bulk deposition and surface waters at two upland locations in northern England

Concentrations of aluminium and minor metals (Mn, Ni, Cu, Zn, Sr, Cd, Ba, Pb) were measured in precipitation and surface water at two upland locations (Upper Duddon Valley, UDV; Great Dun Fell, GDF) in northern England for 1 year commencing April 1998. At both locations, the loads in bulk precipitation were at the lower ends of ranges reported for other rural and remote sites, for the period 1985-1995. The deposited metals were mostly in the dissolved form, and their concentrations tended to be greatest when rainfall volumes were low. The concentrations of Cu, Zn and Pb in deposition were correlated (r2 > or = 0.40) with concentrations of non-marine sulphate. Three streams, ranging in mean pH from 5.07 to 7.07, and with mean concentrations of dissolved organic carbon (DOC) < 1 mg l(-1). were monitored at UDV, and two pools (mean pH 4.89 and 6.83, mean DOC 22 and 15 mg l(-1)) at GDF. Aluminium and the minor metals were mainly in the dissolved form, and in the following ranges (means of 49-51 samples. microg l(-1)): Al 36-530. Mn 4.4-36, Ni 0.26-2.8, Cu 0.25-1.7, Zn 2.1-30, Cd 0.03-0.16, Ba 1.9-140, Pb 0.10-4.5. Concentrations were generally higher at GDF. Differences in metal concentrations between the two locations and between waters at each location, and temporal variations in individual waters, can be explained qualitatively in terms of sorption to solid-phase soil organic matter and mineral surfaces, complexation and transport by DOC, and chemical weathering. The UDV catchments are sinks for Pb and sources of Al, Mn, Sr, Cd and Ba. The GDF catchments are sources of Al, Mn, Ni, Zn, Sr, Cd and Ba. Other metals measured at the two locations are approximately in balance. Comparison of metal:silicon ratios in the surface waters with values for silicate rocks indicates enrichment of Ni and Cu, and substantial enrichment of Zn, Cd and Pb. These enrichments, together with high metal deposition in the past, make it likely that concentrations of the metals in the surface waters are governed by release from catchment pools of atmospherically-deposited metal. The catchments appear to be responding on a time scale of decades, possibly centuries, to changes in metal deposition. For the more acid waters at UDV, the calculated free-ion concentrations of Al are similar to published LC50 values for acute toxicity towards fish. The free-ion concentrations of Ni, Cu, Zn and Cd in all the surface waters are one-to-four orders of magnitude lower than reported LC50 values for fish.     

Changes in trace metal concentrations in lake water and biota during experimental acidification of Little Rock Lake, Wisconsin, USA

Little Rock Lake, a small (18 ha), low-alkalinity (25 microeq litre(-1), pH 6.1) seepage lake in northern Wisconsin, was divided into two basins by a flexible, inert barrier and, beginning in spring 1985, the north basin was acidified in three 2-year steps to pH 5.6, 5.1 and 4.7. The annual average pH of the reference basin remained near 6.1. As part of a comprehensive programme to determine the chemical and biological responses to acidification, minor metals (Al, Fe, Mn) and trace metals (Cd, Cu, Pb, Zn) in lake water (0.4 microm pore filtered samples), periphyton, zooplankton, and yellow perch (Perca flavescens) were measured. At pH 5.6, dissolved Mn and Fe increased in the acidified basin. At pH 5.1 and 4.7, dissolved Al, Fe, Mn, Cd and Zn were elevated in the acidified basin. At pH 4.7, dissolved Pb in the acidified basin became elevated over reference basin levels. Dissolved Cu remained similar in both basins down to pH 4.7. Cd burdens in periphyton collected on artificial substrates were lower in the treatment basin at pH 5.1 (1.8 microg g(-1) dry wt.) than in the reference basin at pH 6.1 (7.5 microg g(-1) dry wt.), but Al and Fe burdens in periphyton were similar in both basins. Likewise, Cd levels in muscle tissue of perch from the treatment basin at pH 4.7 were lower (26 ng g(-1) dry wt.) than in the reference basin at pH 6.1 (36 ng g(-1) dry wt.); Al and Fe burdens were similar in perch muscle tissue from both basins. Levels of Cd and Fe in zooplankton from the acidified basin at pH 4.7 were approximately equal to 2x higher than in animals from the reference basin. In both basins of the lake, Al and Cd levels in lake biota decreased with increasing trophic level, demonstrating that food chain biomagnification does not occur for these metals.     

Earthworms as biological monitors of cadmium, copper, lead and zinc in metalliferous soils

Earthworms (Lumbricus rebellus and Dendrodrilus rubidus) were sampled from one uncontaminated and fifteen metal-contaminated sites. Significant positive correlations were found between the earthworm and 'total' (conc. nitric acid-extractable) soil Cd, Cu, Pb and Zn concentrations (data log1) transformed). The relationships were linear, and the accumulation patterns for both species were similar when a single metal was considered, even though there were species difference in mean metal concentrations. Generally, the earthworm Cd concentration exceeded that of the soil; by contrast, the worm Pb concentration was lower than the soil Pb concentration in all but one (acidic, low soil Ca) site. Our observations suggest that Cu and Zn accumulation may be physiologically regulated by both species. Total-soil Cd explained 82-86% of the variability (V2) in earthworm Cd concentration; 52-58% of worm Pb and worm Zn concentrations were explained by the total-soil concentrations of the respective metals. Total-soil Cu explained only 11-32% of the worm Cu concentration. The effect of soil pH, total Ca concentration, cation-exchange capacity (CEC) and organic carbon on metal accumulation by L. rubellus and D. rubidus was investigated by multiple regression analysis. Soil pH (coupled with CEC) and soil Ca had a major influence on Pb accumulation (V2 of worm Pb increased to 77-83%), and there was some evidence that Cd accumulation may be suppressed in extremely organic soils. The edaphic factors investigated had no effect on Cu or Zn accumulation by earthworms. In the context of biomonitoring, it is proposed that earthworms have a potential in a dual role: (1) as 'quantitative' monitors of total-soil metal concentrations (as shown for Cd); and (2) as estimators of 'ecologically significant' soil metal, integrating the effects of edaphic factors (as shown for Pb).     

Metal contents of fish from cultureponds near scrap metal reclamation facilities

Milkfish (Chanos chanos) from four fish-culture ponds adjacent to different metal recovery facilities along the Er-Jen River area, Tainan, Taiwan, were sampled to determine their metal contents. Chemical analysis showed that fish tissue contained different concentrations of Cu: 0.71-6.37 micrograms/g, Pb: ND (not detectable) approximately 41.04 micrograms/g, Cd: ND approximately 0.41 microgram/g, Al: 6.75-64.11 micrograms/g, Ni: 0.062-0.504 microgram/g and Zn: 16.11-41.86 micrograms/g. The average concentrations of Cu, Al, Zn, Cd and Pb in fish samples from some of the ponds were significantly higher than those from the reference pond. In addition, there were variations in metal concentrations of fish collected from different ponds. Pond D had the highest mean values of Cu, Cd and Zn, and Pond B of Al and Pb. Further investigations are needed to determine the source of metal contamination in the fish.     

The EDTA effect on phytoextraction of single and combined metals-contaminated soils using rainbow pink (Dianthus chinensis)

Rainbow pink (Dianthus chinensis), a potential phytoextraction plant, can accumulate high concentrations of Cd from metal-contaminated soils. The soils used in this study were artificially added with different metals including (1) CK: original soil, (2) Cd-treated soil: 10 mg Cd kg(-1), (3) Zn-treated soil: 100 mg Zn kg(-1), (4) Pb-treated soil: 1000 mg Pb kg(-1), (5) Cd-Zn-treated soil: 10 mg Cd kg(-1) and 100 mg Zn kg(-1), (6) Cd-Pb-treated soil: 10 mg Cd kg(-1) and 1000 mg Pb kg(-1), (7) Zn-Pb-treated soil: 100 mg Zn kg(-1) and 1000 mg Pb kg(-1), and (8) Cd-Zn-Pb-treated soil: 10 mg Cd kg(-1), 100 mg Zn kg(-1), and 1000 mg Pb kg(-1). Three concentrations of 2Na-EDTA solutions (0 (control), 2, and 5 mmol kg(-1) soil) were added to the different metals-treated soils to study the influence of applied EDTA on single and combined metals-contaminated soils phytoextraction using rainbow pink. The results showed that the Cd, Zn, Pb, Fe, or Mn concentrations in different metals-treated soil solutions significantly increased after applying 5 mmol EDTA kg(-1) (p<0.05). The metal concentrations in different metals-treated soils extracted by deionized water also significantly increased after applying 5 mmol EDTA kg(-1) (p<0.05). Because of the high extraction capacity of both 0.005 M DTPA (pH 5.3) and 0.05 M EDTA (pH 7.0), applying EDTA did not significantly increase the Cd, Zn, or Pb concentration in both extracts for most of the treatments. Applying EDTA solutions can significantly increase the Cd and Pb concentrations in the shoots of rainbow pink (p<0.05). However, this was not statistically significant for Zn because of the low Zn concentration added into the contaminated soils. The results from this study indicate that applying 5 mmol EDTA kg(-1) can significantly increase the Cd, Zn, or Pb concentrations both in the soil solution or extracted using deionized water in single or combined metals-contaminated soils, thus increasing the accumulated metals concentrations in rainbow pink shoots. The proposed method worked especially well for Pb (p<0.05). The application of 2 mmol EDTA kg(-1) might too low to enhance the phytoextraction effect when used in silty clay soils.     

Metals in edible fish from Vistula River and Dead Vistula River channel, Baltic Sea

Metals including Al, Ba, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Mg, Mn, Na, Ni, Pb, Sr and Zn were determined in muscle tissue of 12 fish species by inductively coupled plasma-atomic emission spectroscopy (ICP-AES) and cold vapour-atomic absorption spectroscopy (CV-AAS). Fish were collected from Vistula River at lower course and Dead Vistula River channel in south of Baltic Sea in Poland. The fish species examined include Round Goby (Neogobius melanostomus), Crucian Carp (Carassius carassius), Bull-rout (Myoxocephalus scorpius), Tench (Tinca tinca), Bream (Abramis brama), Burbot (Lota lot), Perch (Perca perca), Roach (Rutilus rutilus), Silver Carp (Hypophthalmichthys molitrix), Pikeperch (Stizostediun lucioperca), Brown salmon (Salmo trutta m. Trutta) and Eel (Anguilla anguilla). The median values of metal concentrations in fresh muscle tissue of 11 fish species varied as follows: Al < 0.5-60; Ba < 0.05-0.31; Ca 120-1800; Cd < 0.05-0.096; Co < 0.10; Cr < 0.10-0.50; Cu < 0.15-0.77; Fe 1.5-21; Hg 0.0058-0.65; K 1800-4200; Mg 130-560; Mn 0.12-0.59; Na 350-840; Ni < 0.2-0.31; Pb < 0.75; Sr 0.079-2.9; Zn 3.3-23 μg/g fresh weight. The Target Hazard Quotient (THQ) values calculated in this study for Cd and Hg from muscles of fish species collected from Vistula River were low in the range of 0.4 for Hg and 0.8 for Cd.     

Concentrations of cadmium and other metals in Fucus vesiculosus L. and Fontinalis dalecarlica Br. Eur. from the northern Baltic Sea and the southern Bothnian Sea

Concentrations of Cd and ten other metals (Al, Co, Cr, Cu, Fe, Mn, Ni, Pb, V and Zn) were determined in the brown seaweed Fucus vesiculosus L. and the aquatic moss, Fontinalis dalecarlica Br. Eur. from the northern Baltic Sea and the southern Bothnian Sea. Elevated concentrations of metals were found in samples taken close to densely populated areas, such as Stockholm and Nyn?shamn. Very high concentrations of especially Zn were found in both Fucus and Fontinalis samples taken from the area south of the Gulf of G?vle. The results indicate that mining and industrial activities along the river Dal?lven are the main sources of Zn and several other metals. Cd concentrations in Fucus plants reached maximum values (24.5 mg kg(-1)) at the northern site. The gradual increase of Cd concentrations in Fucus plants northward could not be totally explained by the salinity gradient in the Baltic Sea; reasons for this are discussed in this paper.     

Distribution of elements in needles of Pinus massoniana (Lamb.) was uneven and affected by needle age

Macronutrients (P, S, K, Na, Mg, Ca), heavy metals (Fe, Zn, Mn, Cu, Pb, Cr, Ni, Cd) and Al concentrations as well as values of Ca/Al in the tip, middle, base sections and sheaths of current year and previous year needles of Pinus massoniana from Xiqiao Mountain were analyzed and the distribution patterns of those elements were compared. The results indicated that many elements were unevenly distributed among the different components of needles. Possible deficiency of P, K, Ca, Mn and Al toxicity occurred in needles under air pollution. Heavy metals may threaten the health of Masson pine. Needle sheaths were good places to look for particulate pollutants, in this case including Fe, Cu, Zn, Pb, Cr, Cd and Al.     

Influence of solution acidity and CaCl2 concentration on the removal of heavy metals from metal-contaminated rice soils

Soil washing is considered a useful technique for remediating metal-contaminated soils. This study examined the release edges of Cd, Zn, Ni, Cr, Cu or Pb in two contaminated rice soils from central Taiwan. The concentrations exceeding the trigger levels established by the regulatory agency of Taiwan were Cu, Zn, Ni and Cr for the Ho-Mei soil and Pb for the Nan-Tou soil. Successive extractions with HCl ranging from 0 to 0.2 M showed increased release of the heavy metals with declining pH, and the threshold pH value below which a sharp increase in the releases of the heavy metals was highest for Cd, Zn, and Ni (pH 4.6 to 4.9), intermediate for Pb and Cu (3.1 to 3.8) and lowest for Fe (2.1), Al (2.2) and Cr (1.7) for the soils. The low response slope of Ni and Cr particularly for the rice soils make soil washing with the acid up to the highest concentration used ineffective to reduce their concentrations to below trigger levels. Although soil washing with 0.1 M HCl was moderately effective in reducing Cu, Pb, Zn and Cd, which brought pH of the soils to 1.1+/-0.1 (S.D.), the concurrent release of large quantities of Fe and Al make this remediation technique undesirable for the rice soils containing high clay. Successive washings with 0.01 M HCl could be considered an alternative as the dissolution of Fe and Al was minimal, and between 46 to 64% of Cd, Zn, and Cu for the Ho-Mei soil and 45% of Pb in the Na-Tou soil were extracted after four successive extractions with this dilute acid solution. The efficacy of Cd extraction improved if CaCl2 was added to the acid solution. The correlation analysis revealed that Cr extracted was highly correlated (P < 0.001) with Fe extracted, whereas the Cu, Ni, Zn, Cd or Pb extracted was better correlated (P < 0.001) with Al than with Fe extracted. It is possible that the past seasonal soil flooding and drainage in the soils for rice production was conducive to incorporating Cr within the structure of Fe oxide, thereby making them extremely insoluble even in 0.2 M HCl solution. The formation of solid solution of Ni with Al oxide was also possible, making it far less extractable than Cd, Zn, Cu, or Pb with the acid concentrations used.     

Heavy metal and Pb isotopic compositions of aquatic organisms in the Pearl River Estuary, South China

The accumulation of trace metals in aquatic organisms may lead to serious health problems through the food chain. The present research project aims to study the accumulation and potential sources of trace metals in aquatic organisms of the Pearl River Estuary (PRE). Four groups of aquatic organisms, including fish, crab, shrimp, and shellfish, were collected in the PRE for trace metal and Pb isotopic analyses. The trace metal concentrations in the aquatic organism samples ranged from 0.01 to 2.10 mg/kg Cd, 0.02 to 4.33 mg/kg Co, 0.08 to 4.27 mg/kg Cr, 0.15 to 77.8 mg/kg Cu, 0.17 to 31.0 mg/kg Ni, 0.04 to 30.7 mg/kg Pb, and 8.78 to 86.3 mg/kg Zn (wet weight). High concentrations of Cd were found in crab, shrimp and shellfish samples, while high concentration of Pb was found in fish. In comparison with the baseline reference values in other parts of the world, fish in the PRE had the highest elevated trace metals. The results of Pb isotopic compositions indicated that the bioaccumulation of Pb in fish come from a wide variety of food sources and/or exposure pathways, particularly the anthropogenic inputs.     

Distribution of elements in needles of Pinus massoniana (Lamb.) was uneven and affected by needle age

Macronutrients (P, S, K, Na, Mg, Ca), heavy metals (Fe, Zn, Mn, Cu, Pb, Cr, Ni, Cd,) and Al concentrations as well as values of Ca/Al in the tip, middle and base sections, and sheaths of current year and previous year needles of Pinus massoniana from Xiqiao Mountain were analyzed and the distribution patterns of those elements were compared. The results indicated that many elements were unevenly distributed among the different components of needles. Possible deficiency of P, K, Ca, Mn and Al toxicity occurred in needles under air pollution. Heavy metals may threaten the health of Masson pine. Needle sheaths were good places to look for particulate pollutants, in this case including Fe, Cu, Zn, Pb, Cr, Cd and Al.