Uptake of trace elements and PAHs by fruit and vegetables from contaminated soils

The aims of this study were to investigate the uptake of seven trace elements and five PAHs in crop plants in order to establish advice regarding consumption of fruit and vegetables grown in soils contaminated by trace elements and PAHs. In a field experiment, vegetables were grown in two contaminated soils and in a reference soil, whereas fruits were collected from uncontaminated and contaminated private gardens. The results showed elevated levels of several trace elements and PAHs in the vegetables from contaminated soil. Bioconcentration factors (BCF values), based on dry weight, were below 1, except for those of Cd in lettuce and carrot with peel from uncontaminated soil. In most cases, BCF values were decreasing with increasing concentrations in soil. From the heavily contaminated soil, BCF values for Pb in lettuce, potato, and carrot with peel were 0.001, 0.002, and 0.05, respectively, and those for benzo[a]pyrene were 0.004, 0.002, and 0.002, respectively. For most metals in most vegetables, linear regression showed good correlation between soil and crop concentrations. For PAHs, such good correlation was generally not found. The contents of contaminants in fruits were generally low and no correlation with the level of contamination in the soils was found.     

Speciation and release kinetics of zinc in contaminated paddy soils

Zinc is an important nutrient for plants, but it can be toxic at high concentrations. The solubility and speciation of Zn is controlled by many factors, especially soil pH and Eh, which can vary in lowland rice culture. This study determined Zn speciation and release kinetics in Cd-Zn cocontaminated alkaline and acidified paddy soils, under various flooding periods and draining conditions, by employing synchrotron-based techniques and a stirred-flow kinetic method. Results showed almost no change in Zn speciation and release kinetics in the two soils, although the soils were subjected to different flooding periods and draining conditions. The mineral phases in which Zn is immobilized in the soil samples were constrained by linear least squares fitting (LLSF) analyses of bulk X-ray absorption fine structure (XAFS) spectra. Only two main phases were identified by LLSF, i.e., Zn-layered double hydroxides (Zn/Mg-hydrotalcite-like, and ZnAl-LDH) and Zn-phyllosilicates (Zn-kerolite). Under all soil pHs, flooding, and draining conditions, less than 22% of Zn was desorbed from the soil after a two-hour desorption experiment. The information on Zn chemistry obtained in this study will be useful in finding the best strategy to control Cd and Zn bioavailability in the Cd-Zn cocontaminated paddy soils.     

Extractable copper,lead, zinc and cadmium in Northern Ireland soils

A survey of extractable copper, lead, zinc and cadmium in Northern Ireland's top soils was carried out to see if the trace element concentrations could be related to the parent material of the soils and to the influence of human activity. Using ordnance-survey identification, 1305 samples were selected as representative of the soils of Northern Ireland. Duplicate subsamples of each soil were shaken with 0.05M EDTA (pH 7.0) for 60 min and the supernatant analysed for copper, lead, zinc and cadmium by atomic absorption techniques. Ranges and medians for each trace element are recorded and comparisons with results of copper reported for other countries have been identified. Relative distribution diagrams are presented for each of the elements under investigation and computer-drawn symbol maps have been produced showing the distribution of the concentration of each element in comparison to the parent geology. Finally correlation coefficients between the concentration of each trace element and the ammonium acetate/acetic acid (pH 4.2) extracted phosphorus and potassium have been calculated and used to show that a specific relationship between the extractable trace elements and man's additions to the soil, as indicated by the soil fertility, is poorly developed.     

Solid-solution speciation and phytoavailability of copper and zinc in soils

The soil solution speciation and solid-phase fractionation of copper (Cu) and zinc (Zn) in 11 typical uncontaminated soils of South Australia were assessed in relation to heavy metal phytoavailability. The soils were analyzed for pH (4.9-8.4), soil organic matter content (3.5 to 23.8 g of C kg(-1)), total soil solution metal concentrations, Cu8 (49-358 microg kg(-1)) and Zn8 (121-582 microg kg(-1)), and dissolved organic matter (DOM) (69-827 mg of C L(-1)). The solid-liquid partition coefficient (Kd) ranged from between 13.9 and 152.4 L kg(-1) for Cu and 22.6 to 266.3 L kg(-1) for Zn. The phytoavailability of Cu and Zn could be predicted significantly using an empirical model with the solid-phase fractions of Cu and Zn, as obtained from selective sequential extraction scheme, as components. Phytoavailable Cu and Zn were found to significantly correlate with fulvic complex Cu (r= 0.944, P < 0.0001) and exchangeable Zn (r = 0.832, P = 0.002), respectively. The fulvic complex Cu was found to explain 89.2% of the variation in phytoavailable Cu, where as, the exchangeable Zn together with fulvic complex Zn could explain 78.9% of the variation in phytoavailable Zn. The data presented demonstrate the role of solid-phase metal fractions in understanding the heavy metal phytoavailability. The assessment of the role of solid-phase fractions in heavy metal phytoavailability is a neglected area of study and deserves close attention.     

Relationship between cobalt,copper and zinc content of soils and vegetables

The relationship between cobalt, copper and zinc content of soils and the vegetables grown in them is discussed. Samples of soil and edible vegetables were taken from 15 different sites, corresponding to four agricultural areas exposed to different degrees of environmental pollution: high industrial and traffic, high industrial and urban, and low industrial and urban pollution. Elements were determined by atomic absorption spectroscopy. Variance analysis (ANOVA) was applied to cobalt, copper and zinc content of vegetables and soils in order to detect significant differences among soils of different areas and the vegetables grown there. The possible relationship between the heavy metal content of soils (total and extractable) and of the vegetables grown in them was estimated by the correlation coefficient value. Statistically significant correlations were observed between the total and extractable cobalt content of soils and of roots and bulbs (p < 0.1) and between the total copper content of soils and of inflorescences (p < 0.05). In the case of zinc no correlation was found.     

Iron,nickel, copper,zinc and cadmium content of two cultivars of white yam (Dioscorea rotundata) and their source soils

The determination by atomic absorption spectroscopy of the iron, nickel, copper, zinc and cadmium content of two cultivars of white yam (Dioscorea rotundata Pair) and their source soil from three farms, and also of random samples of the cultivars from five geographical areas in Kaduna and Plateau states of Nigeria, is reported. The analyses show all the metals except Fe to be in trace amounts in the tissues of both cultivars; the barks contain two to four times more. The iron content was found to be about 20 times higher in the bark than in the tissue. Less than 0.7% of the metals present in the soil could be extracted with NH₄NO₃ solution. Yam bark, which contains reasonable amounts of the above metals, could be useful as cattle feed. Yam tissue, having a high content of Zn compared with Cd, could be recommended for the diet of hypertensive patients.     

湿法快速消解-电感耦合等离子质谱法测定大米中的锌、铜、镍

目的探讨电感耦合等离子体质谱法测定大米中铜、锌、镍时,消解温度、混合酸体系和消解时间等因素对测定数据的影响,寻找最佳的样品处理方法。方法通过以45Sc、115In、209Bi作为内标元素进行仪器干扰的校正,对质控样分别采用快速消解和微波消解进行处理,将测定值进行对比。结果锌、铜、镍的检出限分别是0.0012、0.0037、0.0007 ng/mL;回收率在91.20%～106.82%;精密度为5.78%～6.42%。结论采用这2种消解方法对于质控样的测定值基本一致,且都在质控样的标值范围内,表明快速消解和微波消解均可用于大米中铜、锌、镍的测定。     

Estimation of available copper,iron, manganese and zinc in soils using cation-exchange resin

Studies on the extractability of available Cu, Fe, Mn and Zn in soils using cation-exchange resin were carried out. A procedure involving the shaking of 5 g soil with 5 g of resin in 200 ml deionised water for 2 h at 25 ± 1°C followed by colorimetric determination of the micronutrient elements in solution was adopted. This was compared with known chemical extraction methods in the prediction of availability to Phaseolus mungo as test plant. Correlation analysis showed that the method successfully indicated the availability of Cu, Mn and Zn but was not sensitive enough for the prediction of the availability of Fe. The proposed method is simple, convenient and compares favourably with the chemical extractants in the prediction of availability of Cu, Mn and Zn.     

Soil tests for available copper and zinc in soils of Western Nigeria

Four soil tests for copper and zinc were evaluated for their ability to predict Cu and Zn uptake by oats (Avena sativa, L., Lodi var.) grown on 28 soils from Western Nigeria. Statistical analyses showed that EDTA was a better extractant for predicting Cu uptake than was DTPA, 0.1 N -HCl or 1 N -HCl. Copper uptake was more strongly correlated with inorganic soil fractions than with organic matter and was not significantly affected by soil pH. The best prediction of Zn uptake was provided by a combination of 0.1 N -HCl extractable Zn, pH, organic matter and the silt plus clay fraction in a multiple regression analysis. All four extractants predicted plant Zn uptake better on soils of pH less than 6.0 than on soils of pH greater than 6.0. A significant amount of Cu and Zn in the soils appeared to be associated with sesquioxides, part of which was available for plant use.     

Zinc,copper and nickel concentrations in ryegrass grown on sewage sludge-contaminated soils of different pH

Sewage sludges containing high concentrations of zinc, copper and nickel were added separately to samples of two soils, a silty clay loam and a sandy loam, on which pH levels between 4.5 and 7.5 had been established; there were also treatments with sludge of low metal content or no-sludge. Soil-sludge mixtures were either continuously cropped with ryegrass or kept uncropped in pots in the glasshouse for 6 months. Zinc and nickel concentrations in 0.1 μM calcium chloride extracts of soils from the cropped pots and in solutions displaced from the fallow pots decreased with increasing pH over the range tested, but copper concentrations remained steady above pH 5.5; individual metal concentrations in ryegrass tops followed the same pattern with pH as those in extracted solutions. Squared correlation coefficients (R⁷) between shoot metal concentrations and concentrations of metals in EDTA, DPTA or calcium chloride extracts or displaced solutions, when taken over all soil, pH and sludge treatments, were >0.60 (P<0.001). Ryegrass yield reductions occurred on soils contaminated with each of the three metal sludges when soil pH was 5.5 or below.     

Time-dependent changes of zinc speciation in four soils contaminated with zincite or sphalerite

The long-term speciation of Zn in contaminated soils is strongly influenced by soil pH, clay, and organic matter content as well as Zn loading. In addition, the type of Zn-bearing contaminant entering the soil may influence the subsequent formation of pedogenic Zn species, but systematic studies on such effects are currently lacking. We therefore conducted a soil incubation study in which four soils, ranging from strongly acidic to calcareous, were spiked with 2000 mg/kg Zn using either ZnO (zincite) or ZnS (sphalerite) as the contamination source. The soils were incubated under aerated conditions in moist state for up to four years. The extractability and speciation of Zn were assessed after one, two, and four years using extractions with 0.01 M CaCl(2) and Zn K-edge X-ray absorption fine structure (XAFS) spectroscopy, respectively. After four years, more than 90% of the added ZnO were dissolved in all soils, with the fastest dissolution occurring in the acidic soils. Contamination with ZnO favored the formation of Zn-bearing layered double hydroxides (LDH), even in acidic soils, and to a lesser degree Zn-phyllosilicates and adsorbed Zn species. This was explained by locally elevated pH and high Zn concentrations around dissolving ZnO particles. Except for the calcareous soil, ZnS dissolved more slowly than ZnO, reaching only 26 to 75% of the added ZnS after four years. ZnS dissolved more slowly in the two acidic soils than in the near-neutral and the calcareous soil. Also, the resulting Zn speciation was markedly different between these two pairs of soils: Whereas Zn bound to hydroxy-interlayered clay minerals (HIM) and octahedrally coordinated Zn sorption complexes prevailed in the two acidic soils, Zn speciation in the neutral and the calcareous soil was dominated by Zn-LDH and tetrahedrally coordinated inner-sphere Zn complexes. Our results show that the type of Zn-bearing contaminant phase can have a significant influence on the formation of pedogenic Zn species in soils. Important factors include the rate of Zn release from the contaminant phases and effects of the contaminant phase on bulk soil properties and on local chemical conditions around weathering contaminant particles.     

Oral intake of cadmium,cobalt, copper,iron, lead,nickel, manganese and zinc in the University student's diet

A duplicate diet meal study was carried out with a group of university students living in a hostel, in order to estimate the intake of Zn, Cd, Co, Cu, Fe, Mn, Ni and Pb. Zn, Cu, Fe, Mn and Ni were determined by flame atomic absorption spectrophotometry and Cd, Co and Pb by graphite furnace atomic absorption spectrophotometry after a nitric acid wet digestion procedure. The estimated intake values from the contents of breakfast, lunch, dinner and drinks were compared with the values of the Provisional Tolerable Daily Intake (PTDI) in the case of Cd and Pb, Recommended Dietary Allowances (RDA) of Co, Fe and Zn and Estimated Safe and Adequate Dietetic Daily Intake (ESADDI) of Cu and Mn. Neither excessive intake of Pb and Cd nor deficiencies in Zn, Co, Fe, Mn or Ni were observed, but Cu intake was lower than the ESADDI.     

Toxicity of silver, zinc, copper, and nickel to the copepod Acartia tonsa exposed via a phytoplankton diet

Toxicity tests were conducted with the marine copepod Acartia tonsa to assess the effects of dietary metal exposure. The diatom Thalassiosira pseudonana was cultured with Ag, Zn, Cu, or Ni and used as diets for adult A. tonsa over a 7-d exposure, and copepod survival and reproduction were measured throughout the exposure period. For all metals, reproduction was the most sensitive endpoint, with 20% effect concentrations (EC(20)s) corresponding to exposures of T. pseudonana to 0.64, 0.3, 1.2, and 2.4 microg/L for Ag, Zn, Cu, and Ni, respectively. The corresponding metal concentrations in the algae added to copepod test solutions (EC(20)s) were 5.44, 0.55, 22.3, and 15.3 microg/g for Ag, Zn, Cu, and Ni, respectively. None of the applied metal concentrations influenced algal growth. The results of this study have potential implications for water quality criteria considering that the estimated EC(20)s fall below the current criteria of 3, 86, 3, and 8.3 microg/L for Ag, Zn, Cu, and Ni, respectively.     

Comparison of atmospheric deposition of copper, nickel, cobalt, zinc, and cadmium recorded by Finnish peat cores with monitoring data and emission records

This study aims to determine the extent to which the accumulation rates of Cu, Ni, Co, Zn, and Cd in peat cores agree with established histories of atmospheric emission from local pointsources. Metals accumulating in three Finnish peat cores with known metal deposition histories have been measured using inductively coupled plasma-sector field mass spectrometry. Samples were age-dated using both 210Pb and 14C (bomb pulse curve). At the Outokumpu (OUT) site as well as the low-background site Hietaj?rvi (HIJ), 210Pb age dates are in excellent agreement with the 14C bomb pulse curve method results, and the precision is between 1 and 10 years for most of the samples; at the Harjavalta (HAR) site, precision is > 6 years. Mean regional "background" concentrations have been calculated from deeper peat layers of the HIJ site (microg g(-1)): Cu, 1.3 +/- 0.2 (n = 62); Co, 0.25 +/- 0.04 (n = 71); Cd, 0.08 +/- 0.01 (n = 23); and Zn, 4 +/- 2 (n = 40). For layers accumulated within the past 100 years, accumulation rates (ARs) have been calculated. At sites with < 0.06 g m(-2) cumulative Ni inventory (HIJ and OUT), ARs of Cu and Co trace the known metal deposition histories very well. At HAR, where metal inventories are much greater, Cu and Co are mobile. ARs of Zn were between 3 and 30 mg m(-2) year(-1) and those of Cd between 24 and 140 microg m(-2) year(-1) at all sites and are independent of the chronology of their inputs from the atmosphere.     

Sorption of copper,zinc and cobalt by oat and oat products

We determined copper, zinc and cobalt sorption by oat and its products under variable pH conditions as well as the content of neutral dietary fiber (NDF) and its fractional composition. Adsorbents in a model sorption system were: oat, dehulled oat, oats bran and oats flakes. Three various buffers (pH 1.8, 6.6 and 8.7) were used as dispersing solutions. Results collected during this study indicate that copper, zinc and cobalt sorption is significantly affected by the type of cereal raw material. Zinc and copper ions are subjected to higher sorption than cobalt ions. Examined metal ions were subjected to high sorption under conditions corresponding to the duodenum environment (pH 8.7( regardless of the kind of adsorbent. A little lower sorption capacity is observed under conditions close to the neutral environment, while the lowest one is found in environment reflecting conditions of stomach juice (pH 1.8). Zinc ions are bound intensively by dehulled oat, while oats flakes bound mostly copper and cobalt, independently on environmental conditions. Contents of dietary fiber in oat, dehulled oat, oat bran and oat flakes were: 40.1, 19.3, 20.3 and 14.3%, respectively. The dominating fraction in all oat products was the fraction of hemicelluloses. The content of remaining fractions varies in dependence on the product.     

Sorption of copper,zinc and cobalt by oat and oat products

We determined copper, zinc and cobalt sorption by oat and its products under variable pH conditions as well as the content of neutral dietary fiber (NDF) and its fractional composition. Adsorbents in a model sorption system were: oat, dehulled oat, oats bran and oats flakes. Three various buffers (pH 1.8, 6.6 and 8.7) were used as dispersing solutions. Results collected during this study indicate that copper, zinc and cobalt sorption is significantly affected by the type of cereal raw material. Zinc and copper ions are subjected to higher sorption than cobalt ions. Examined metal ions were subjected to high sorption under conditions corresponding to the duodenum environment (pH 8.7), regardless of the kind of adsorbent. A little lower sorption capacity is observed under conditions close to the neutral environment, while the lowest one is found in environment reflecting conditions of stomach juice (pH 1.8). Zinc ions are bound intensively by dehulled oat, while oats flakes bound mostly copper and cobalt, independently on environmental conditions. Contents of dietary fiber in oat, dehulled oat, oat bran and oat flakes were: 40.1, 19.3, 20.3 and 14.3%, respectively. The dominating fraction in all oat products was the fraction of hemicelluloses. The content of remaining fractions varies in dependence on the product.     

杂优水稻对土壤中铅和镉的吸收与分配

研究在长沙市金星村采集的普通红壤、加石灰红壤,以及于两种土壤生长的杂优水稻,检测土壤、根、茎叶、壳及糙米中Pb和Cd的含量,分析水稻出穗前,向土壤中加入石灰对Pb和Cd在水稻各部位分配的影响。结果表明:在普通红壤中,Pb有94.20%在根中分配,Cd只有54.00%在根中分配;在加石灰红壤中,Pb和Cd在根及茎叶中总的分配分别增加2.20%,17.20%,在糙米中的分配分别降低0.78%,11.30%;加石灰红壤中糙米Pb和Cd的富集系数分别降低0.02%,2.60%。因此在水稻出穗前向土壤中加入石灰能有效降低Pb和Cd在糙米中的富集。