Contribution of zooplankton to the total cadmium pool in Canadian shield lakes varying in acidity

Crustacean zooplankton >250 m in size contributed 0.002 to 11% (median of 1.3%) of the total Cd in the epilimnia of 39 Canadian Shield lakes that ranged in pH from 4.7 to 8.3. The contribution of zooplankton to the total Cd pool was consistently low (1%) only in clear water lakes with pH < 5.0.=" in=" three=" intensively=" studied=" lakes,=" the=" contribution=" of=" zooplankton=" to=" total=" aqueous=" cd=" varied=" with=" time=" and=" depth,=" the=" maximum=" contribution=" (4=" to=" 6%)=" occurring=" in=" the=" metalimnion=" in=" mid-summer.=" changes=" with=" depth=" and=" time=" were=" principally=" a=" product=" of=" seasonal=" changes=" in=" zooplankton=" biomass=" and=" seasonal=" succession=" of=" species=" with=" inherently=" different=" tendencies=" to=" accumulate=" cd.=" implications=" for=" the=" study=" of=" cd=" cycling=" in=" lakes=" are=">     

Metal chemistry of irrigation and drainage waters of Al-Ahsa Oasis of Saudi Arabia and its effects on soil properties

Water samples from 18 springs and 13 drainage canals and subcanals were collected from Al-Ahsa Oasis. Concentrations of total dissolved salts, Cl, SO₄ HCO₃, B, Al, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, V, Ti, and Zn were determined. The soil salinity development (SSD), the adjusted Na ratio (adj. SAR), the adjusted Na adsorption ratio (adj. RNa), and exchangeable Na percentage (ESP) were calculated. Sodium was the most abundant cation in all water samples followed by Ca, Mg, Sr, and K in descending order. Concentrations of all other metals were below 0.1 mg L^–1. Chloride was the most abundant anion, followed by SO₄ and HCO₃ in these waters. A significant correlation (P < 0.05)=" between=" na=" and=" cl=" in=" water=" samples=" was=" found.=" thermodynamic=" calculations=" revealed=" that=" an=" appreciable=" fraction=" of=" ca=" and=" mg=" in=" spring=" and=" drainage=" waters=" were=" associated=" with=">₄ and HCO₃ ions. Calcium increased from less than 10 meq L^–1 in spring waters to > 16 meq L^–1, Mg was doubled, and Na and Cl increased several times in the drainage waters. The salinity and sodicity hazards of the spring and drainage waters were classified as C₄S₂ i.e. high salinity with medium sodicity problems.     

Snowpack quality as an indicator of air pollution in Finnish Lapland and the Kola Peninsula,NW Russia

Bulk snow samples were collected from the snowpack in open areas along two sampling lines running to the west from the Cu-Ni smelters at Nikel and Monchegorsk, NW Russia, during 1991–1993. The aim of the study was to estimate the area affected by sulphur and heavy metal deposition from the smelters. Snowpack quality was used as an indicator of deposition during winter time. The total sulphur, copper and nickel concentrations in the snowpack decreased significantly (p<0.001) with=" increasing=" distance=" from=" the=" smelters=" along=" the=" sampling=" line=" running=" directly=" to=" the=" west=" from=" monchegorsk.=" the=" deposition=" pattern=" was=" similar=" each=" winter=" during=" 1991–1993.=" the=" ph=" values=" did=" not=" correlate=" with=" the=" corresponding=" sulphur=" concentrations,=" and=" there=" was=" no=" decreasing=" ph=" gradient=" in=" the=" snowpack=" on=" moving=" towards=" monchegorsk.=" the=" effects=" of=" sulphur=" emissions=" from=" monchegorsk=" on=" snowpack=" chemistry=" were=" not=" detectable=" on=" the=" finnish=" side=" of=" the=" border.=" the=" 3-year=" mean=" of=" the=" total=" sulphur=" concentration=" was=" 0.27=" mg/kg,=" and=" of=" the=" ph=" values=" 4.92,=" along=" the=" sampling=" line=" running=" to=" the=" west=" of=" monchegorsk.=" the=" total=" sulphur=" concentrations=" near=" the=" smelters=">< 20=" km)=" varied=" between=" 0.37=" and=" 0.95=" mg/kg.=" the=" effect=" of=" the=" cu-ni=" smelters=" at=" nikel=" on=" snowpack=" quality=" was=" not=" detectable=" in=" northern=" finnish=" lapland.=" the=" 3-year=" mean=" for=" total=" sulphur=" was=" 0.20=" mg/kg=" and=" for=" ph=" 4.96=" along=" the=" sampling=" line=" running=" to=" the=" west=" of=">     

Modelling long-term acidification trends of forested sandstone catchments in the Black Forest (SW Germany)

An extensive database from eight Triassic (Bunter) sandstone catchments in the Black Forest, SW Germany, was used to apply the MAGIC model and simulate long-term acidification trends. Using the ion ratio (Ca+Mg)/(SO₄+NO₃) as criterium (values< 1.5=" indicate=" an=" acidified=" state),=" hindcast=" simulations=" showed=" that=" the=" brooks=" of=" three=" catchments=" have=" reached=" values="><1.5, three=" catchments=" are=" approaching=" 1.5,=" and=" two=" catchments=" (carbonate=" bearing=" upper=" bunter)=" are=" still=" well=" above=" this=" limit.=" the=" different=" acidification=" state=" of=" the=" catchments=" is=" mainly=" caused=" by=" the=" amount=" of=" acidic=" deposition=" and=" bedrock=" geology.=" other=" differences=" (shallow=" or=" deep=" groundwater=" circulation,=" sulphate=" sorption=" and=" soil=" parameters)=" are=" less=" significant.=" to=" simulate=" the=" future=" evolution,=" three=" scenarios=" were=" tested:=" a=" pessimistic,=" an=" optimistic=" and=" a=" most=" probable=" case.=" the=" latter=" leads=" to=" a=" still=" progressing=" but=" decelerated=" acidifcation=" in=" the=" next=" 100=" years.=" in=" the=" pessimistic=" case,=" acidification=" rates=" will=" be=" accelerated=" in=" two=" of=" the=" catchments.=" even=" in=" the=" optimistic=" case,=" the=" initial=" state,=" prior=" to=" acidification,=" cannot=" be=" restored=" up=" to=" the=" year=" 2130.=" however,=" the=" forecasting=" of=" the=" future=" evolution=" is=" still=" markedly=" hampered=" by=" the=" significant=" uncertainty=" in=" the=" evaluation=" of=" nitrogen-driven=" acidification,=" a=" process=" which=" today=" already=" predominates=" in=" parts=" of=" the=" black=">     

Cadmium contamination of sediments in the water reservoirs in Silesian Upland (southern Poland)

Purpose

Cadmium (Cd) is considered a toxic element and its concentrations are relevant to human health and the environment. Therefore, the purpose of the study was to determine the extent to which the bottom sediments of water bodies (artificial lakes and ponds) in the Silesian Upland in southern Poland are contaminated with Cd; an attempt was also made to determine the factors that condition spatial differences in the concentration of this element between individual water bodies in the region.

Materials and methods

Measurements of the Cd content in bottom sediments were carried out in 35 water bodies in southern Poland in 2011 and 2012. Depending on the surface area and morphometric characteristics, from two to nine samples representative in terms of sediment thickness were collected in each water body. Cadmium concentrations were determined for 92 0.25 g aliquots using the TD-ICP method.

Results and discussion

Cadmium content in all samples (0.7–580.0 mg kg^?1) was higher than the natural range of concentrations for this element in the Earth’s crust (0.1–0.3 mg kg^?1) and the geochemical background for Poland (0.5 mg kg^?1) and, with a few exceptions, was also higher than the preindustrial concentration (1.0 mg kg^?1) and the regional geochemical background (2.5 mg kg^?1). Adopting natural Cd concentrations in the Earth’s crust (0.1–0.3 mg kg^?1) as the baseline for the geoaccumulation index (I_geo), the sediments examined can be classified as extremely and heavily contaminated (and moderately contaminated in a small number of cases). The assessment of sediment quality based on I_geo, with the regional geochemical background (2.5 mg kg^?1) adopted as the baseline, results in non-contaminated and moderately contaminated sediments being dominant with a far smaller number of heavily and extremely contaminated ones.

Conclusions

In the case of several water bodies, Cd concentrations were at record levels that have not been found anywhere else in the world. On the basis of the I_geo, sediments of varying quality were found—from virtually uncontaminated to extremely contaminated. The I_geo index as an indicator of the quality of bottom sediments is a measure that requires careful interpretation, especially when different concentration levels regarded as natural are used for determining its value.

     

Evaluating macroinvertebrate responses to recovery from acidification in small lakes in Ontario,Canada

The biomonitoring program of Environment Canada examines food chains in small Ontario lakes to interpret ecological responses of waterfowl and their foods to changing acid deposition. Macroinvertebrates and fish were sampled in three acid-sensitive regions: Muskoka (1991; N=20), Algoma (1992; N=20), and Sudbury (1994; N=22). Small lakes (<11 ha;=" important=" breeding=" habitat=" for=" waterfowl)=" were=" chosen=" to=" cover=" the=" range=" of=" ph=" in=" each=" region,=" and=" include=" those=" with=" and=" without=" fish.=" in=" all=" regions,=" macroinvertebrate=" taxonomic=" richness=" (particularly=" nekton=" and=" benthos)=" was=" greater=" in=" fishless=" lakes=" compared=" to=" lakes=" with=" fish.=" among=" fishless=" lakes,=" taxonomic=" richness=" (especially=" benthos)=" was=" positively=" correlated=" with=" ph,=" although=" regional=" differences=" were=" evident.=" previous=" studies=" near=" sudbury=" have=" shown=" that=" several=" benthic=" groups=" have=" distribution=" and=" abundance=" patterns=" with=" respect=" to=" ph=" (trichoptera,=" ephemeroptera,=" hirudinea,=" amphipoda,=" and=" gastropoda).=" those=" patterns=" continue=" near=" sudbury,=" and=" were=" also=" strongly=" apparent=" in=" algoma.=" in=" all=" regions,=" the=" number=" of=" acid-sensitive=" taxa=" per=" lake=" is=" related=" to=" ph,=" and=" should=" increase=" as=" lakes=" recover=" from=" acidification.=" however,=" predicting=" macroinvertebrate=" responses=" to=" recovery=" must=" consider=" concurrent=" effects=" of=" fish,=" as=" they=" are=" a=" dominant=" factor=" structuring=" these=">     

Evidence of Metal Interaction in the Bioaccumulation of Cadmium and Zinc in Porcellio Laevis (Isopoda) after Exposure to Individual and Mixed Metals

The aim of this study was to determine the accumulation of cadmium and zinc in Porcellio laevis after separate and mixed exposure to these metals. This would give an indication whether cadmium and zinc influence each others bioaccumulation. Decaying oak leaves collected from an uncontaminated site (Botanical Gardens of the University of Stellenbosch) were used as substrate in the experiments. The concentrations used were 20, 80 and 160 mg kg^–1 (dry mass) cadmium sulphate and 1000, 4000 and 8000 mg kg^–1 (dry mass) zinc sulphate. These metals were administered separately and mixed in the experiments. The cadmium and zinc mixtures used were 20 mg kg^–1 CdSO₄ with 1000 mg kg^–1 ZnSO₄, 80 mg kg^–1 CdSO₄ with 4000 mg kg^–1 ZnSO₄ and 160 mg kg^–1 CdSO₄ with 8000 mg kg^–1 ZnSO₄. It was shown that cadmium and zinc accumulated in P. laevis, especially in the hepatopancreas, in both the single-metal and mixed-metal exposures. Cadmium and zinc also exhibited the ability to influence the bioaccumulation of each other in the mixed-metal exposures. It is also concluded that the interaction of these two metals is at least partly dependent on the ratio of exposure concentrations, the actual exposure concentrations, and also the period of exposure.     

Trace metals in sediments and aquatic plants from the Xiangjiang River, China

Purpose

The metal concentrations and Pb isotopic composition in sediments and plants from the Xiangjiang River, China, were investigated to understand the contamination and potential toxicity of metals in sediments; to determine the accumulation and distribution of metals in plant tissues; and to trace the possible pollution source of Pb in sediments and plants.

Materials and methods

Sediments and plants were collected from 43 sampling sites in the study region. After sediments were air-dried and passed through a 63-??m sieve, they were acid-digested and DTPA-extracted for determination of total and bioavailable metals. The plants were separated into roots, leaves, and stems; dried; cut into pieces; and digested with HNO₃?CH₂O₂. Metals (As, Cd, Cr, Cu, Ni, Pb, and Zn) and Pb isotopic composition were analyzed by inductively coupled plasma-mass spectrometry.

Results and discussion

Maximum As, Cd, Cr, Cu, Ni, Pb, and Zn concentrations in sediments were 47.18, 55.81, 129.5, 161.6, 160.4, 430.7, and 1,098.8?mg?kg^?1, respectively. The bioavailable fractions of As, Cd, Cu, Pb, and Zn had significant linear relationship with their corresponding total contents in sediments while no significant relationship was observed between bioavailable and total contents of Cr and Ni. In general, plant tissues showed higher As, Cd, Cu, Pb, and Zn concentrations and lower Cr and Ni concentrations compared with sediments. The ²⁰⁶Pb/²⁰⁷Pb ratios decreased in the order of total > bioavailable > stems ?? leaves > roots. A strong linear correlation was observed between the ²⁰⁸Pb/²⁰⁶Pb and ²⁰⁶Pb/²⁰⁷Pb ratios of the plant tissues, sediments, and the possible pollution sources of Pb in the Xiangjiang River.

Conclusions

As, Cd, Cu, Pb, and Zn demonstrated higher contamination levels in sediments and plants compared with Cr and Ni. Cd had highest potential ecological risk. The Pb from anthropogenic sources with low ²⁰⁶Pb/²⁰⁷Pb ratios was preferentially associated with the bioavailable fractions in sediments and accumulated in roots. The Pb in plant tissues is mainly derived from the Pb in sediment and is taken up through the sediment-to-root pathway.     

Influence of pH on the release and chemical fractionation of heavy metals in sediment from a suburban drainage stream in an arid mine-based oasis

Purpose

The objectives of this study were to explore the influences of pH on the release of Cu, Zn, Cd, Pb, Ni, and Cr in sediments derived from the upstream, middle, and downstream reaches of Dongdagou stream in Gansu Province, Northwest China, and to examine the fractionation changes of heavy metals in the sediments after reaching their release equilibrium under different pH conditions.

Materials and methods

Sediment samples were obtained using a stainless steel grab sampler to collect the uppermost 10 cm of sediment from the channel bed. The pH-dependent release experiment was conducted in the solid-to-liquid ratio of 1:20 at different pH values (2, 4, 6, 8, 10, and 12) at room temperature. The total Cu, Zn, Cd, Pb, Ni, and Cr concentrations in the sediments were digested using an acid digestion mixture (HNO₃ + HF + HClO₄) in an open system. Metal fractionation of selected sediments was obtained using the Tessier sequential extraction procedure. Heavy metal concentrations in the samples were determined using atomic absorption spectrophotometry.

Results and discussion

The mean concentrations of heavy metals in sediments decreased in the following order: Zn (1676.67 mg kg^?1) > Pb (528.65 mg kg^?1) > Cu (391.34 mg kg^?1) > Cr (53.48 mg kg^?1) > Ni (34.27 mg kg^?1) > Cd (11.53 mg kg^?1). Overall, the solubility of Cu, Zn, Cd, Pb, and Ni decreased with increasing pH, and they were strongly released at pH 2. Moreover, the solubility of Cr increased with increasing pH, and its release was highest at pH 12. After reaching the release equilibrium of heavy metals under different pH conditions, the percentages of organic Cu, Zn, Cd, and Fe-Mn oxyhydroxide Pb decreased, compared to their initial fractions. The residual fractions of Ni and Cr were dominant, regardless of pH.

Conclusions

The average concentrations of Cu, Zn, Cd, and Pb in sediments were highly elevated compared with the soil background values in Gansu Province, China. The results of this pH-dependent release experiment showed that the release behaviors of Cu, Zn, Pb, and Cr followed an asymmetric V-shaped pattern, whereas Cd and Ni followed an irregular L-shaped pattern. The changes in the release of heavy metals in sediments were related to their redistribution between chemical fractionations.

     

Sources of error in the determination of Cd and Pb in plant material by atomic absorption

Abstract

Some difficulties were met when low levels of Cd and Pb were estimated in plant samples in this laboratory by atomic absorption spectrophotometry (AAS).

A modified procedure, based on methyl isobutyl ketone (MIBK) extraction of the metal complexes with ammonium pyrollidine dithio carbamate (APDC), has been developed for use on samples digested with HNO₃/HCIO₄. The procedure was compared with X‐ray fluorescence and with other AAS methods including those based on dry ashing. Dry ashing gave generally lower values for Cd and Pb. Improvement in conditions of digestion and analysis are described. Of these, the presence of small amounts of Fe in standards and unknown samples increases the stability and reproducibility of absorbance values, especially for cadmium.     

Extractability of major and trace elements from agricultural soils using chemical extraction methods: Application for phytoavailability assessment

Abstract

To assess soil-to-plant transfer of various elements more precisely, the concentrations of the elements extracted from soil samples using eight chemical solutions were compared with the results of a pot cultivation experiment of komatsuna (Brassica rapa L. var. perviridis) or buckwheat (Fagopyrum esculentum M.) using the soils. From agricultural fields in Aomori, Japan, 16 soil samples were collected. Elements in the samples were extracted using acids (1 mol L^?1 HNO₃, 0.1 mol L^?1 HNO₃, 0.01 mol L^?1 HNO₃), chelating agents (0.05 mol L^?1 EDTA), neutral salt solutions (1 mol L^?1 NH₄OAc, 1 mol L^?1 NH₄NO₃, 0.01 mol L^?1 CaCl₂) and pure water. The 28 elements in the extracted solutions and plant samples were determined. The extractability of many metals was higher in 1 mol L^?1 HNO₃, 0.1 mol L^?1 HNO₃ and the 0.05 mol L^?1 EDTA solutions than in the other extractants. Higher extractability using the NH₄OAc solution than the NH₄NO₃ solution was observed for some elements, in particular U. Extractability by pure water was not always lowest among these methods, probably because of dispersion of colloidal substances in the extracted solution. The pot cultivation experiment showed that the concentrations in soil and in the extracted fraction using 1 mol L^?1 HNO₃, 0.1 mol L^?1 HNO₃ or the EDTA solution did not correlate with the concentration in plant samples for most elements. Plant uptake of Zn, Y and La by komatsuna correlated well with their concentrations in extracts with neutral salt solutions or 0.01 mol L^?1 HNO₃. Concentrations of Al, Cu and Cd in buckwheat were also correlated with the concentrations in the extracts.     

SOLUBILITY AND SORPTION OF CADMIUM IN SOILS AMENDED WITH SEWAGE SLUDGE

The mechanisms governing the retention and release of Cd in two soils, a loam and a loamy sand, pretreated with anaerobically digested sewage sludges or with chemical fertilizers, were studied using batch equilibration in 0.05 m Ca(NO₃)₂ solution containing up to 6 μg Cd/ml. Adsorption rather than precipitation as Cd₃(PO₄)₂ limited solution Cd²⁺ concentration. With the addition of 50 μg Cd/g, however, precipitation as CdCO₃ was likely at pH 7.6. Cadmium adsorption increased with increasing soil pH. The differences in Cd adsorption between different soil treatments were attributed mainly to the soil pH (6.9 to 7.9) induced by sludge application. About 82 to 92 per cent of adsorbed Cd was retained by cation exchange and complexing sites. Soils treated with sludge increased the amount of exchangeable Cd but reduced the amount of complexed Cd compared with the fertilized soil. Cadmium retention by cation exchange became more dominant as the amount of Cd in the soil was increased.     

Plant Availability of Cadmium in Soils: II. Factors Related to the Extractability and Plant Uptake of Cadmium in Cultivated Soils

Abstract

Eighty four soil samples collected from southeastern Norway were analyzed for Cd by extraction with NH₄OAc, DTPA, NH₄OAc-EDTA, NH₄NO₃, HCl and CaCl₂. The total Cd, pH, exchangeable K and Ca, dithionite-extractable Mn, available P and fine sand (0.2–0.02 mm) contents were the principal factors related to the extractable Cd, with some inter-extractant variations. Cadmium extracted by NH₄NO₃, NH₄OAc, HCl and CaCl₂ decreased with increasing soil pH, but the Cd extracted by all the extractants increased with increasing total Cd, exchangeable K and Ca, available P, and Mn-oxide contents in the soils. The Cd concentrations in plants were significantly related to the extractable Cd, exchangeable Ca and Mg, pH, Mn-oxides and organic matter content.     

The influence of the form of nitrogen nutrition on uptake and distribution of cadmium in lettuce varieties

Four lettuce (Lactuca saliva L.) varieties ('Benita’, ‘Wendy’, ‘Mirena’, and ‘Jacky') were grown for 43 days in a pH‐controlled complete nutrient solution without cadmium (Cd) or with either 0.01 or 0.03 mg Cd/1 and with NH₄ or NO₃ as the form of nitrogen nutrition. Cadmium did not affect dry matter yield. ‘Wendy’ had a significantly higher total dry matter production when grown on NO₃ compared to NH₄, whereas growth of ‘Mirena’ was best on NH₄ (P<0.05). Dry weights of ‘Benita’ and ‘Jacky’ were not affected by the N source. Cadmium concentrations in shoots (and roots) of plants grown on NH₄ were significantly higher than in plants grown on NO₃. The Zn concentrations in the shoots were also enhanced. The distribution of Cd in the lettuce varieties was independent of the form of N nutrition. It is concluded that the N source directly affects the amount of Cd taken up, without influencing the Cd distribution.     

Efficiency of h+‐atpase activity on cadmium uptake by four cultivars of lettuce

Cadmium (Cd) uptake by lettuce (Lactuca sativa L.) was studied in a hydroponic solution study at concentrations approaching the total concentration in contaminated soil solutions. Four cultivars of lettuce were tested (Divina, Reine de Mai, Melina, and J.44). Ten 12‐day old seedlings, pretreated in 0.5 μM CdCl₂ solution, were labelled with carrier free ¹⁰⁹CdCl₂ (from 0.05 μM to 5 μM Cd in nutrient solution) in the presence and absence of metabolic inhibitors, DNP and DCCD. Cadmium taken up by the roots was determined after a 30 min desorption in unlabelled CdCl₂ solution. In the absence of metabolic inhibitors and at 5 μM Cd, root absorbed from 2.5 to 8 mg Cd/g root dry weight. Exchangeable Cd measured after desorption represented less than 1% of the total Cd absorbed by the root. Cadmium absorption in presence of DNP showed that approximately 80% of the Cd enters the cell through an active process. This mechanism seems to be directly associated with H⁺‐ATPase as observed with DCCD inhibition. Varietal differences in shoot Cd uptake were only demonstrated at concentrations below 0.1 μM. Screening lettuce cultivars only by the Cd level in the tissue seems not to be possible for these cultivars except at concentrations close to that in the soil solution. But differences in relative contribution of uptake mechanisms in total Cd absorption were observed. High levels of Cd in roots were correlated with high contri‐ butions from H⁺‐ATPase in the active process of Cd uptake.     

Predicting heavy metal transfer from soil to plant: potential use of Freundlich‐type functions

Soil‐plant transfer of metals is a nonlinear process. We therefore aimed at evaluating the potential of Freundlich‐type functions (c_Plant = b × c_Soil^a) to predict Cd, Cu, Pb, and Zn concentrations in wheat (Triticum aestivum L.) grain and leaf (c_Plant) from soil concentrations (c_Soil). Wheat plants and soil A horizons, mainly developed from Holocene sediments, were sampled at 54 agricultural sites in Slovakia. Metals were extracted from soils with 0.025 M EDTA at pH 4.6 and concentrated HNO₃/HClO₄ (3:1); plant samples were digested with concentrated HNO₃. Total metal concentrations of soil samples were 0.07—25 mg Cd kg^—1, 9.3—220 mg Cu kg^—1, 14—1827 mg Pb kg^—1, and 34—1454 mg Zn kg^—1. On average, between 20 % (Zn) and 80 % (Cd) of the total concentrations were EDTA‐extractable. The total metal concentrations of grain samples were < 0.01—1.3 mg Cd kg^—1, 1.3—6.6 mg Cu kg^—1, < 0.05—0.30 mg Pb kg^—1, and 8—104 mg Zn kg^—1. The leaves contained up to 3.2 mg Cd kg^—1, 111 mg Cu kg^—1, 4.3 mg Pb kg^—1, and 177 mg Zn kg^—1. Linear regression without data transformation was precluded because of the nonnormal data distribution. The Freundlich‐type function was suitable to predict Cd (grain: r = 0.71, leaf: 0.86 for the log‐transformed data) and Zn concentrations (grain: 0.69, leaf: 0.68) in wheat grain and leaf from the EDTA‐extractable metal concentrations. The prediction of Cu and Pb concentrations in grain (Cu: r = 0.44, Pb: 0.41) was poorer and in leaf only possible for Pb (0.50). We suggest to use the Freundlich‐type function for defining threshold values instead of linear regression because it is more appropriate to simulate the nonlinear uptake processes and because it offers interpretation potential. The results suggest that the coefficient b of the Freundlich‐type function depends on the intensity of metal uptake, while the coefficient a reflects the plants' capability to control the heavy metal uptake. The latter is also sensitive to metal translocation in plants and atmospheric deposition.<?show $6#>     

Trace Elements in Fish Overlying Subaqueous Tailings in the Tropical West Pacific

From 1972–1989, Bougainville Copper Limited (BCL) dischargedmine tailings into Empress Augusta Bay on the west coast ofBougainville Island, Papua New Guinea. For a decade(1977–1987), trace elements (Cu, Pb, Zn, Cd, Hg and As) weremeasured in muscle tissue and organs of 8 species of tropicalmarine fish common to both the east and west coasts of theIsland. Metal concentrations were not elevated in muscle tissueof west fish compared with those from the east coast.Concentrations of Cu, Pb, Zn and Cd in fish muscle from bothcoasts ranged from 10–15% of recommended maximum residuelimits (MRLs), whereas concentrations of Hg in muscle wereslightly higher, ranging up to 80% of the MRL (0.5 mgkg^-1 Hg wet wt.). Maximum total As concentrations (3.6 mgkg^-1 wet wt.) were recorded in the shark (Rhizoprionodon acutus), while highest Hg values (0.76 mgkg^-1 wet wt.) were found in hammerhead sharks (Sphyrnalewini) from both coasts. Despite significant temporalvariations in Hg and As concentrations in muscle tissue of somewest coast fish populations (p < 0.05), there was no evidencefor bioaccumulation or biomagnification of any of these metalsduring the 10 yr period, even in the soft organs (liver andkidney) of fish. Several site specific factors contributing toabsence of metals uptake from tailings are discussed.     

Assessing metal bioaccumulation from estuarine sediments: comparative experimental results for the polychaete Arenicola marina

Purpose

The purpose of this paper is to compare three approaches for providing information on the bioaccumulation potential of metals from contaminated sediments to the deposit-feeding polychaete Arenicola marina.

Materials and methods

We present metal (Ag, As, Cd, Cu, Pb and Zn) bioaccumulation results from field-collected sediments quantified through direct measurements of bioaccumulated concentrations in A. marina over a period of 30 days under controlled laboratory exposures and compare these results with bioaccumulated metal concentrations in field-collected organisms from the same sites of collection of the sediments used in the laboratory exposures. For the metals for which model parameters are available (Ag, As, Cd and Zn), we also compare these results with biodynamic model predictions. We considered three UK estuaries characterised by a well-reported history of trace metal contamination and bioavailability in addition to the (control) site of collection of the worms.

Results and discussion

The results from laboratory-exposed organisms showed that the standard 28-day exposure duration may be adequate to identify the potential for metal bioaccumulation in this polychaete at the sites considered here. However, the time course of bioaccumulated concentrations and the comparison with measured concentrations in field-collected worms show that a steady state has not been reached, confirming the need for extended exposure periods. The worms showed symptoms of stress in feeding and growth during the initial 10 days of exposure and subsequent partial recovery during the following 20 days, suggesting that stress was not always caused by sediment contamination but that it was likely associated with handling and acclimation. At this last stage of the exposure, a generalised biodynamic model was used to provide estimates of bioaccumulated metal concentrations and net accumulation rates in worms.

Conclusions

The results of this study highlight the number of factors that should be considered for the interpretation of bioaccumulated metal concentrations in A. marina under laboratory exposures for contaminated sediment assessment, factors that appear to be common to most deposit-feeding polychaetes. A general biodynamic model proved to be a cost-effective method for an initial estimation of the extent and pattern of metal bioaccumulation under specified exposure conditions.     

Phytoextraction of Cadmium and Phytostabilisation with Mugwort (Artemisia vulgaris)

Artemisia vulgaris (mugwort) is a tall (1.0?C2.0 m) high biomass perennial herb which accumulates considerable amounts of metals on contaminated sites. An outdoor pot experiment was conducted on a sandy, slightly alkaline soil of moderate fertility to study the uptake of cadmium and the distribution of Cd in plant tissues of A. vulgaris. Cadmium was applied as CdCl₂ (a total of 1 l solution of 0, 10, 50 and 100 mg Cd l^?1) to 12-l pots with a height of 25 cm. HNO₃- and water-extractable concentrations of Cd were correlated with the applied Cd at 2-cm soil depth, but were not correlated at 20-cm soil depth, suggesting that Cd was either not mobile in the soil or completely taken up by mugwort roots. The Cd concentrations in different organs of A. vulgaris and litter increased with increasing soil contamination. Leaf/soil concentration ratios (BCFs) up to 65.93?±?32.26 were observed. Translocation of Cd to the aboveground organs was very high. The leaf/root Cd concentration ratio (translocation factor) ranged from 2.07?±?0.56 to 2.37 ± 1.31; however, there was no correlation of translocation factors to Cd enrichment, indicating similar translocation upon different soil contamination levels. In summary, A. vulgaris is tolerant to the metal concentrations accumulated, has a high metal accumulating biomass and accumulates Cd up to about 70% in the aboveground parts. Both a high phytoextraction potential and a high value for phytostabilisation would recommend mugwort for phytoremediation.     

Proper supply of S increases GSH synthesis in the establishment and reduces tiller mortality during the regrowth of Tanzania guinea grass used for Cd phytoextraction

Purpose

Cadmium has caused serious environmental problems due to its phytotoxicity, requiring solutions to reduce its concentration in the environment. Because S can alleviate the phytotoxicity caused by heavy metals, the evaluation of the effects of S supply is a promising approach to address this problem. The aim of this study was to determine the influence of S in reducing the phytotoxicity caused by Cd to Panicum maximum Jacq. cv. Tanzania (guinea grass) and to evaluate the potential of this grass for Cd phytoextraction.

Materials and methods

Tanzania guinea grass was cultivated in a nutrient solution to evaluate the combinations of five rates of S (0.1, 1.0, 1.9, 2.8, and 3.7 mmol L^?1) and five rates of Cd (0.0, 0.5, 1.0, 1.5, and 2.0 mmol L^?1), in a 5² fractional factorial design with six replications. Six plants were grown per pot in two growth periods to evaluate the effect of Cd on the establishment (51 days of age) and on the regrowth (18 days of growth) of the plants. During regrowth, Cd was not supplied in the nutrient solution. At the end of each growth period, growth parameters, concentrations of S and Cd, Cd transport factor, and concentrations of hydrogen peroxide (H₂O₂), malondialdehyde, reduced glutathione, and oxidized glutathione were evaluated.

Results and discussion

On the establishment of Tanzania guinea grass, application of Cd reduced mass production by 39 % due to the increases in the concentration of Cd (30 times compared with the treatment without Cd) and in lipid peroxidation (124 %). During regrowth, the residual effect of Cd resulted in a lower number of tillers (62 %) and leaves (89 %) caused by the increase in concentrations of Cd, H₂O₂ (49 %), and lipid peroxidation, which resulted in a 65 % lower dry mass production. The proper supply of S reduced concentration of Cd and tiller mortality rate due to the residual effect of Cd on the regrowth of the grass. Mass production by the roots was 43 % lower because of Cd, but the transport of Cd from roots to shoots increased. The increase in the concentration of glutathione (GSH) associated with a possible higher activity of antioxidant enzymes alleviated the phytotoxic effects of Cd on the guinea grass.

Conclusions

The supply of S reduces the phytotoxicity caused by Cd to guinea grass, especially during the regrowth of the plant, when the concentration of Cd is higher because of the transport from roots to shoots. Tanzania guinea grass showed to be very promising for phytoextraction of Cd due to its high mass production, even when Cd was largely available in the nutrient solution.