Survey of Heavy Metal Pollution in Four Chinese Crude Drugs and Their Cultivated Soils

A two-year survey on the residues of heavy metals in four Chinese crude drugs and their cultivated soils was conducted. Targeted heavy metals were copper (Cu), arsenic (As), lead (Pb), nickel (Ni), and cadmium (Cd). Herbs surveyed include White Peony Root (Radix Paeoniae Alba), Turmeric Root Tuber (Radix Curcumae), Thunberg Fritillary Bulb (Bulbus Fritillariae Thumbergii), and Tuber of Dwarf Lilyturf (Radix Ophiopogonis). Concentrations of all heavy metals were under the permitted levels except cadmium, which exceeded the permitted level in some samples of Thunberg Fritillary Bulb, White Peony Root, and Turmeric Root Tuber. Concentration coefficients were less than 1.0 for all heavy metals except cadmium. The concentration coefficient of cadmium in Turmeric Root Tuber was 14.0. Lower pH and high Zn concentration in the soil may facilitate the transfer of cadmium from cultivated soil into the herbs.     

Cadmium uptake by earthworms as related to the availability in the soil and the intestine

The free metal concentration in the soil solution is often considered a key parameter for metal uptake by and toxicity to soft-bodied soil organisms. The equilibrium partitioning theory, which assumes a relationship between the contaminant concentration in pore water and the contaminant concentration in the body tissue, can be used to describe uptake by earthworms. This theory has proved useful for organic chemicals, but its applicability is less clear for metals. In this study, the Cd concentration in soil pore water (pw) was varied by increasing the soil pH by the addition of lime (Ca(OH)2) and by adding manganese oxide (MnO2), which has a high metal binding capacity. Both lime (0.135% w/w) and MnO2 (1% w/w) decreased [Cd2+]pw by a factor of 25, while Cdworm was reduced only by a factor of 1.3 in lime-treated soils and 2.5 in MnO2-treated soils. Cadmium uptake was weakly related to the free metal concentration (R2adj = 0.66). Adding pH as an explanatory variable increased R2adj to 0.89, indicating that Cd uptake from pore water is pH dependent, which might be attributed to competition of protons and Cd at the surface of the earthwororm body. However, previous earthworm experiments in reconstituted groundwater showed a conspicuously smaller pH dependency of Cd uptake. The differences in metal uptake between earthworms in lime- and MnO2-treated soils are therefore more likely to reflect the predominance of pH-independent intestinal uptake of Cd. Equilibrating the soil with a solution of 0.01 M CaCl2 and 0.1 M triethanolamine (buffered at pH 7.2), simulating the conditions prevailing in the worm intestine, yielded free Cd concentrations that were closely (R2adj = 0.83) and linearly related to the Cd concentration in the earthworm tissue.     

Effects of Flooding on Changes in Eh,pH and Speciation of Cadmium and Lead in Contaminated Soil

Artificially contaminated soils (A, B) and naturally contaminated soil (S2) in China were used as the tested soils, and the effect of continuous flooding on the changes of Eh, pH and the speciation of cadmium, lead in contaminated soils was studied in the paper. The results indicated that soil Eh decreased with flooding time, and that soil pH increased with flooding time. The changes of soil pH ceased after 60 days of submergence. The exchangeable Cd and Pb decreased obviously during the flooding process from the results of five-step sequential extraction. The calculations of mobility factor (MF) showed that Cd mobility significantly decreased in artificially contaminated soils (A, B) after the flood. But the change of Pb mobility was not significant after the flood, although a decrease of Pb concentration in the exchangeable fraction (SE) was observed.     

Effect of soil properties on lead bioavailability and toxicity to earthworms

Soil properties are important factors modifying metal bioavailability to ecological receptors. Twenty-one soils with a wide range of soil properties (USA; http://soils.usda.gov/technical/classification/taxonomy/) were amended with a single concentration of Pb (2,000 mg/kg) to determine the effects of soil properties on Pb bioavailability and toxicity to earthworms. Earthworm mortality ranged from 0 to 100% acute mortality following exposure to the same total concentration of Pb (2,000 mg/kg) in amended field soils. Internal Pb concentrations in earthworms ranged from 28.7 to 782 mg/kg, with a mean of 271 mg/kg. Path analysis was used to partition correlations in an attempt to discern the relative contribution of each soil property. Results of path analysis indicated that pH was the most important soil property affecting earthworm mortality (p < 0.01) and internal Pb (p < 0.05). Soil pH was related inversely to mortality and internal Pb, soil solution Pb, and Pb bioavailability. The most important soil property modifying reproduction was amorphous iron and aluminum oxides (FEAL). Because FEAL is rich in pH-dependent cation-exchange sites, several soil properties, including pH, FEAL, and cation-exchange capacity, have a causal effect on Pb adsorption and soluble Pb. Path analysis is useful for assessing contaminated soils with a wide range of soil properties and can assist in ecological risk assessment and remediation decisions for contaminated sites. Soil properties are important factors modifying metal bioavailability and toxicity and should be considered during the ecological risk assessment of metals in contaminated soils.     

Uptake and Elimination of Cadmium and Zinc by Eisenia andrei During Exposure to Low Concentrations in Artificial Soil

Bioaccumulation factors (BAFs) are often used in the risk assessment process to estimate trophic transfer of contaminants such as metals from soil. BAFs can be derived from laboratory studies through the determination of steady-state concentrations or kinetic estimation methods. In this study, bioaccumulation tests were performed with artificial soil spiked at low levels with cadmium or zinc to determine uptake and elimination kinetics of both metals by the compost worm Eisenia andrei. The metal-amended soils were acclimated for 21 days prior to the test, after which worms were individually incubated in the soils. The uptake phase comprised 0–21 days, after which the test organisms were transferred into clean soil and the elimination phase continued for an additional 21 days. Subsamples of soil and earthworms (whole body) were collected from independent replicates throughout the uptake phase and elimination phase and analyzed for total metal concentrations. Uptake of Cd in E. andrei increased linearly with time and did not reach steady state within the testing period. Cd uptake and excretion were described by a one-compartment first-order kinetics model. Zn concentrations rapidly increased in E. andrei after 1 day of exposure but subsequently decreased to background levels throughout the remainder of the uptake phase; internal Zn concentrations did not change from background levels during the elimination phase. Kinetic BAFs were calculated for Cd and Zn. Cd is a nonessential metal that is bioaccumulated at a relatively rapid rate, while Zn is an essential metal, and as such, it is regulated by E. andrei. Metal essentiality and concentration significantly impact bioaccumulation of metals by terrestrial invertebrates.     

Stable strontium accumulation by earthworms: a paradigm for radiostrontium interactions with its cationic analogue, calcium

The accumulation of stable strontium and its chemical analogue calcium by four species of earthworm, representing three distinct ecophysiological groups inhabiting celestite (SrSO4)-rich natural soils, was investigated. An increase in soil strontium concentration over a four-orders-of-magnitude range was accompanied by an increase in earthworm tissue strontium concentration. In contrast, no relationship between soil and tissue calcium concentrations was apparent, indicating that this essential cation is strongly regulated within earthworm tissues but that nonessential strontium burdens are not physiologically regulated. Concentration factors for strontium ranged from 0.1 to 1.42, with an inverse relationship between this parameter and soil strontium concentration. The use of concentration factors and discrimination coefficients lead to the conclusion that earthworms discriminate against strontium accumulation at increased soil calcium concentrations, such that strontium would be predicted to be more efficiently accumulated by worms inhabiting acidic, calcium-poor soils. Although few consistent trends in strontium and calcium concentration were apparent between earthworm species, the species with the highest calcium turnover (i.e., the litter-inhabiting Lumbricus rubellus) typically accumulated higher concentrations of strontium than representatives of contrasting ecophysiological classes. These findings are considered in the context of the distribution, retention, and cycling of radiostrontium in soils.     

Lead and stable lead isotope ratios in soil, earthworms, and bones of American woodcock (Scolopax minor) from eastern Canada

A study to discriminate among different possible sources of elevated Pb exposure for American woodcock (Scolopax minor) in eastern Canada is described. Undamaged wing bones excised from young-of-the-year woodcock collected from several locations in southern Ontario, southern Quebec, New Brunswick, and Nova Scotia, Canada, along with soil and earthworm (Aporrectodea tuberculata and Lumbricus rubellus) samples from the same sites, were analyzed for total Pb, and stable Pb isotopes. Ignoring six soil samples with high (> 60 microg/g) Pb concentration from the vicinity of Montreal (QC, Canada), the mean soil-Pb concentration for all sites combined was 19 microg/g (dry wt; n = 64), with a mean 206Pb:207Pb ratio of 1.19, values typical for uncontaminated rural soils in eastern North America. In earthworms, Pb concentrations ranged from 2.4 to 865 (microg/g [dry wt], mean = 24 microg/g). Concentrations of Pb in worms and soils were positively correlated (r = 0.71; p < 0.01), and 206Pb:207Pb ratios for worms and soils were also positively correlated (r = 0.54; p < 0.05). However, most young-of-the-year woodcock with high bone-Pb accumulation (> 20 microg/g) had 206Pb:207Pb ratios substantially different from worms and soils sampled from the same areas, even though woodcock feed extensively on soil invertebrates, especially earthworms. The range of 206Pb:207Pb ratios in wing bones of woodcock with elevated Pb exposure was not consistent with exposure to environmental Pb from past gasoline combustion nor Precambrian mining wastes but was consistent with ingestion of spent Pb shotgun pellets.     

Study of the health effects of long-term exposure to cadmium and lead in a region of Poland

A region in Poland with a high concentration of lead (Pb) and cadmium (Cd) was used as a case study to look for the potential health consequences of chronic cadmium and lead exposure. The analysis of the incidence of cardiovascular diseases and neoplasms mortality were carried out and the mortality using SDR (standardized death rate) were compared with Cd and Pb pollution in each of 13 cities. To estimate the association between health effect and the pollutant concentration, the linear regression method was used. On the basis of calculated regression, the magnitude of changes in the health state has been estimated assuming that the ambient air pollution decrease is 10%. The reduction of the concentrations of both heavy metals in the air will lower SDR, by 24.4 and 31.6 people for cadmium and lead, respectively.     

Horizontal and Vertical Distribution of Lead,Cadmium, and Zinc in Farmlands Around a Lead-Contaminated Goldmine in Zamfara,Northern Nigeria

This study was undertaken to evaluate the vertical and horizontal distribution of lead (Pb), cadmium (Cd), and zinc (Zn) in farmlands around a Pb-contaminated goldmine. Total concentrations of Pb and Cd recorded were at maximum values of 2,246.55 and 68.7 mg kg^?1, respectively; these are greater than the threshold values for Pb (300 mg kg^?1) and Cd (3 mg kg^?1). However, the concentration of Zn was within acceptable limits (300 mg kg^?1). Down the soil profile, concentrations of Pb, Cd, and Zn showed two peaks; these were attributed to facilitated transport and ground-water enrichment. Incubation of the soil samples with glucose indicated low microbial process(es), which could be due to the increased levels of Pb and Cd. Factor analysis showed a close association of Pb and Cd with the soil-exchange complex with a possibility of these heavy metals replacing Ca and other divalent cations in the soil-exchange site. This will, however, increase the risk of Pb and Cd leaching and uptake by plants. Although the metals were more associated with resistant soil fraction (sand), which also indicates their geogenic origin, chemical weathering under the influence of pH could release these metals into the soil-exchange site.     

Availability of Heavy Metals (Cd, Pb, and Cr) in Agriculture from Commercial Fertilizers

The purpose of this study was to investigate the availability of the heavy metals cadmium (Cd), lead (Pb), and chromium (Cr) to soil and maize plants fertilized with different sources and doses of zinc (Zn) in a Rhodic Eutrudox soil. For that purpose, concentrations of Cd, Pb, and Cr were evaluated in leaf tissue and grains of maize plants and in 0–20 and 20–40 cm soil layers after fertilization with four doses of Zn from eight different sources of fertilizer. There was no accumulation of Cd, Pb, and Cr in maize grain and Cd and Cr in leaf tissue of the plants; nevertheless, there was accumulation of Pb in leaf tissue, showing its availability throughout different sources of Zn and consequent uptake by plants. Regarding the soil, it was observed that fertilizer from the different sources made Cd, Pb, and Cr available at increasing amounts proportional to increased Zn doses. Under experimental conditions, fertilization with Zn increased concentrations of heavy metals Cd, Pb and Cr in soil, further highlighting the importance of conducting more studies related to the application of mineral fertilizers for micronutrient supply and the availability of heavy metals.     

土壤中萘降解菌的耐铅性能及机制初步研究

目的探讨土壤中萘降解菌对萘和重金属双重污染的耐受性。方法对油田石油污染土壤中分离到的一株高效萘降解菌——伯克霍尔德菌(Burkholderia sp.)TN的重金属耐受性、铅富集机制及在土壤生物修复中的应用进行研究,以分光光度法测定不同Pb~(2+)浓度(100~500 mg/L)对菌悬液吸光度的影响,以电感耦合等离子体发射光谱仪(ICP-OES)测定培养基中重金属(50 mg/L,Pb~(2+),Zn~(2+),Cu~(2+)和Cd~(3+))在菌体培养液、细胞壁、细胞内富集物中的分布,以扫描电镜(SEM)、能谱仪(EDS)和傅里叶变换红外光谱(FTIR)观察100 mg/L Pb~(2+)对菌体形态、元素及官能团分布的影响。结果菌株TN对Pb~(2+)的最高耐受浓度为500 mg/L并可耐受一定浓度的Zn~(2+)、Cu~(2+)和Cd~(3+),TN对Pb~(2+)富集程度最高,细胞壁及胞内富集率达到98.33%;菌体蓄积Pb~(2+)后细胞壁表面有沉淀物附着并有铅元素检出,对Pb~(2+)的蓄积主要依靠细胞壁上的羧基、羟基、酰胺基及磷酸基团;将TN菌株接种到含有2.5 mg/g萘及200 mg/L Pb~(2+)的灭菌土壤中,经过13 d室温培养之后,萘的去除率为94.29%。结论 TN菌株对Pb~(2+)、Zn~(2+)、Cu~(2+)和Cd~(3+)均具有一定的耐受性,对Pb~(2+)的富集能力强。该菌株能够依靠细胞壁上的活性基团富集Pb~(2+),适用于萘和Pb~(2+)双重胁迫的土壤修复。     

我国环境中镉、铅、砷污染及其对暴露人群健康影响的研究进展

该文对我国环境有色金属镉、铅、砷污染及其对暴露人群健康影响的流行病学研究进展进行了综述.研究认为有色金属镉、铅、砷对人体有毒害作用;有色金属矿山的开采和冶炼是环境镉、铅、砷污染的主要来源;污染物进入环境后,产生水污染、大气污染、土壤污染和生物污染,继而危害暴露人群的身体健康,产生一系列急性和慢性病症.但环境有色金属镉、铅、砷污染与暴露人群肿瘤等相关疾病的相关性以及对人体健康产生影响的累积暴露量需进一步进行调查和研究;通过危害认定、剂量-反应关系评定、暴露评价和危险度特性描述对该类环境污染健康影响作出危险度评价应是今后研究的重点.     

Cadmium and Lead Accumulation in Three Endogeic Earthworm Species

The objective of this study was to assess the capability of earthworms from the same ecological group as heavy metal bioindicators. Three earthworm species from the endogeic group were studied: Aporrectodea caliginosa (Savigny, 1826), Perelia kaznakovi (Michaelsen, 1910) and Octolasion lacteum (Örley, 1885). Their accumulation of the heavy metals lead (Pb) and cadmium (Cd) were studied from three stations in Tehran province, Iran. O. lacteum was used to compare metal accumulations in two sites located next to a highway. A. caliginosa and P. kaznakovi were used at a third site located near the edge of a sewage system to compare metal accumulations between the two endogeic species in this area. At both locations, the concentrations of Cd and Pb in earthworms were higher than in the surrounding soil. The results of the study revealed that P. kaznakovi and A. caliginosa were better bioindicators for Pb, but O. lacteum was a better bioindicator for Cd. These earthworms can therefore be used as Cd and Pb bioindicators in environmental assessment.     

Effect of beringite on cadmium and zinc uptake by plants and earthworms: more than a liming effect?

Metal-contaminated soils are potentially harmful to plants, animals, and humans. Harmful effects are often related to the free-metal concentration in the soil solution. Immobilization is a potentially useful method to improve the quality of metal-contaminated soils by transforming free-metal ions into species that are less mobile and less toxic. The effect of many immobilizing products can be attributed to sorption on the surface of the material. Alkaline materials also enhance adsorption to soil particles by decreasing proton competition. Immobilization should preferably be evaluated independently of soil pH to discriminate between these processes. In this study, the immobilizing effect of beringite, an alkaline alumino silicate, was compared with that of lime. Plants (Swiss chard [Beta vulgaris L. var. cicla]) were grown on a soil contaminated with cadmium and zinc and treated with graded amounts of beringite or lime. Metal availability, as determined by a 0.01 M CaCl2 extraction, and metal uptake by plants strongly decreased in all treated soils. Beringite did not reduce metal availability more than liming when the obtained pH levels were similar. The effect of beringite can, therefore, be explained as a liming effect, at least for the duration of our experiment (10 weeks). The effect of beringite and lime on metal accumulation by earthworms (Eisenia veneta and Lumbricus rubellus) was small or not significant, although the CaCl2-extractable metal concentration in treated soils decreased by more than 90%. We conclude that immobilizing agents based on a liming effect can decrease metal uptake by plants, but they will hardly affect metal uptake by earthworms. Hence, these materials can reduce negative ecological effects of metal contamination on plants and herbivores, but not on earthworm predators.     

Toxicity of metal mixtures to a tropical freshwater alga (Chlorella sp): the effect of interactions between copper,cadmium, and zinc on metal cell binding and uptake

The individual and combined effects of copper, cadmium, and zinc on the cell division rate of the tropical freshwater alga Chlorella sp. were determined over 48 to 72 h. Metal mixtures were prepared based on multiples of their single-metal median effective concentration (EC50) values, i.e., toxic units (TU) using a triangular mixture design with five toxicant levels (0, 0.75, 1.0, 1.25, and 1.5 TU). Single-metal EC50 values after a 72-h exposure were 0.11, 0.85, and 1.4 microM for copper, cadmium, and zinc, respectively. Significant interactions were observed for all metal combinations after 48 and 72 h. An equitoxic mixture of Cu + Cd was more than concentration additive (synergistic) to the growth of Chlorella sp., while combinations of Cu + Zn, Cd + Zn, and Cu + Cd + Zn were all less than concentration additive or were antagonistic. To determine the effect of each metal on the uptake of the other, extracellular (membrane-bound) and intracellular metal concentrations, both alone and in mixtures, were compared. The increased growth inhibition observed for mixtures of Cu + Cd was due to higher concentrations of cell-bound and intracellular copper in the presence of cadmium compared with copper alone (i.e., cadmium-enhanced copper uptake). In contrast, both extra- and intracellular cadmium concentrations were reduced in the presence of copper. In mixtures of Cu + Zn, copper also inhibited the binding and cellular uptake of zinc, which resulted in decreased toxicity. Zinc had no appreciable effect on the uptake of copper by Chlorella sp. Our results suggest that all three metals share some common uptake and transport sites on Chlorella cells and that copper out competes both cadmium and zinc for cell binding. Determination of metal cell distribution coefficients (K(d)) confirmed that K(d) values for cadmium and zinc in single-metal exposures decreased in the presence of copper.     

Placental transfer of lead,mercury, cadmium,and carbon monoxide in women: I. Comparison of the frequency distributions of the biological indices in maternal and umbilical cord blood

In 1975 and 1976 we have undertaken a survey among 500 pregnant women living in different areas of Belgium in order to evaluate the extent of exposure to heavy metals (lead, mercury, cadmium) during fetal life, their possible biological effects, and the epidemiological factors which may influence the intensity of exposure.Carboxyhemoglobin level was also determined. Comparison of the frequency distributions of the various hematological indices in maternal and umbilical cord blood indicates that the three heavy metals are transferred from the mother to the fetus but the barrier role of the placenta is different for the three metals. There is no barrier for the transfer of mercury, a slight one for lead, and a more important one for cadmium. This explains that the correlation found between the cadmium concentration in maternal (CdB) and fetal blood is much lower (although statistically significant: r = +0.38) than that found for lead and mercury (r>0.6). For the range of blood lead concentrations (PbB) observed in the mothers and their newborns, there is no significant correlation between PbB and erythrocyte porphyrin level. On the contrary, because of its high sensitivity to lead, the erthrocyte enzyme δ-aminolevulinate dehydratase (ALAD) is negatively correlated with PbB in mother and newborn. The correlation is higher when ALAD activity is expressed in per cent of its activity found in presence of the reactivator dithiothreitol rather than in absolute values. Carboxyhemoglobin levels (HbCO) of mother and newborn are highly correlated (r = +0.81 P < 0.001). In mother, HbCO is also slightly correlated with CdB (r = +0.29 P < 0.001) which suggests that both pollutants come at least partly from a similar source (smoking).Because of the different barrier effect of the placenta for CO and Cd no significant correlation between both parameters is found in newborns.     

Cadmium concentrations in the freshwater mussel (Elliptio complanata) and their relationship to water chemistry

Concentrations of cadmium were determined in freshwater mussels (Elliptio complanata) from 21 small lakes in south-central Ontario. The average Cd concentrations ranged from 0.5 to 7.5 g/g dry weight. A poor correlation between the concentration of Cd in lakewater and the concentration of Cd in the organisms was observed. Concentration of Cd in the sediments was not a useful predictor. Thus, it is hypothesized that the availability of the Cd varies among the 21 lakes. In an effort to test this hypothesis, the relationships between organism concentrations and water chemistry parameters that have the potential to alter Cd availability including pH, calcium (Ca), total organic carbon (TOC) and total inorganic carbon (TIC) were examined. The strongest relationship was found between Cd concentration in the mussels and water column pH, suggesting that hydrogen ions are replacing Cd ions in complexes and increasing the amount of free Cd available to the organisms. Correlations between pH and other water chemistry parameters make it difficult to test this hypothesis. A multiple regression model was developed incorporating pH, Ca, TOC, and TIC which explained 69% of the variance in Cd concentrations.     

Liming Effects on Cadmium Stabilization in Upland Soil Affected by Gold Mining Activity

To reduce cadmium (Cd) uptake of plants cultivated in heavy metal–contaminated soil, the best liming material was selected in the incubation test. The effect of the selected material was evaluated in the field. In the incubation experimentation, CaCO₃, Ca(OH)₂, CaSO₄·2H₂O, and oyster shell meal were mixed with soil at rates corresponding to 0, 400, 800, 1600, 3200 mg Ca kg⁻¹. The limed soil was moistened to 70% of field moisture capacity, and incubated at 25°C for 4 weeks. Ca(OH)₂ was found to be more efficient on reducing soil NH₄OAc extractable Cd concentration, due to pH increase induced net negative charge. The selected Ca(OH)₂ was applied at rates 0, 2, 4, 8 Mg ha⁻¹ and then cultivated radish (Raphanus sativa L.) in the field. NH₄OAc extractable Cd concentration of soil and plant Cd concentration decreased significantly with increasing Ca(OH)₂ rate, since alkaline-liming material markedly increased net negative charge of soil induced by pH increase, and decreased bioavailable Cd fractions (exchangeable + acidic and reducible Cd fraction) during radish cultivation. Cadmium uptake of radish could be reduced by about 50% by amending with about 5 Mg ha⁻¹ Ca(OH)₂ without adverse effect on radish yield and growth. The increase of net negative charge of soil by Ca(OH)₂ application may suppress Cd uptake and the competition between Ca²⁺ and Cd²⁺ may additionally affect the suppression of Cd uptake.     

Effect of Chronic Sublethal Exposure of Major Heavy Metals on Filtration Rate, Sex Ratio, and Gonad Development of a Bivalve Species

The chronic toxic effects of major heavy metals including copper (Cu), zinc (Zn), lead (Pb), and cadmium (Cd) on the filtration rate (FR), sex ratio, and gonad development of immature blood clams, Tegillarca granosa, were investigated. The FRs were significantly inhibited by Cu, Pb and Cd, with rates generally decreasing with both increasing metal concentrations and exposure time. EC₅₀ values for FR after 28 days of exposure were 12.9, 12.7 and 14.4 μg/L for Cu, Pb and Cd, respectively. Zn exposure had no effect on FR. Sex ratios were significantly altered from controls in favor of an increased proportion of males at metal concentrations of ≥14.2, ≥86 and ≥110 μg/L for Cu, Pb and Cd, respectively; and at ≥1.68 mg/L for Zn. The gonado-somatic index was significantly reduced in clams at all metal exposures, except for the lowest concentration of Cu (7.1 μg/L).