Environmental cadmium exposure, adverse effects and preventive measures in Japan

In Japan the most heavily cadmium (Cd)-polluted region is the Jinzu river basin, where Itai-itai disease is endemic and the Kakehashi river basin is the second most polluted region.. The village average Cd concentrations in rice were distributed in the range between 0.02 microg/g and 1.06 microg/g in the Jinzu river basin and 0.11 microg g and 0.67 microg g in the Kakehashi river basin. Severe renal damage has occurred widely in the Jinzu river basin. Even after Cd exposure had ceased, renal dysfunction became worse. Dose-response relationships between Cd exposure and health effects were clearly demonstrated in both regions. The allowable limits (according to the present authors' assessment) of Cd concentrations in rice were estimated to be 0.08 microg g to 0.13 microg g and approximately 2 g for total Cd intake. Renal dysfunction caused by exposure to Cd was associated with an increased mortality in both regions. The increased total Cd intake and high concentration of Cd in rice also exerts an adverse influence on life prognosis.     

Influence of Consumption of Cadmium-Polluted Rice or Jinzu River Water on Occurrence of Renal Tubular Dysfunction and/or Itai-itai Disease

The aim of this study was to clarify whether consumption of cadmium (Cd)-polluted rice or Jinzu River water exerted any influence on the occurrence of renal tubular dysfunction and/or Itai-itai disease. From the participants of health examinations conducted in 1967 and 1968, 3,078 subjects who had resided for >30 years in the present hamlet and were aged >50 years were selected as the target population and were divided according to their residence in 55 hamlets. In a multiple regression analysis, the regression coefficients between rice-Cd concentration and prevalence of abnormal urinary findings (proteinuria, glucosuria, or proteinuria with glucosuria) or patients with Itai-itai disease were statistically significant between both sexes. The correlation between the prevalence of users of Jinzu River water and the occurrence of glucosuria in men as well as abnormal urinary findings in women was not statistically significant. We surmise that eating Cd-polluted rice and drinking and/or cooking with Jinzu River water influenced the occurrence of Itai-itai disease. The occurrence of renal tubular dysfunction is likely to have also been influenced by both factors, with eating Cd-polluted rice having a greater impact on the occurrence of renal tubular dysfunction as compared to drinking and/or cooking with Jinzu River water.     

Allowable level of lifetime cadmium intake calculated from the individuals in the Jinzu River basin of Japan

We investigated a dose-response relationship between renal dysfunction and liftime cadmium intake in individual subjects using logistic regression analysis and calculated the allowable level of lifetime cadmium intake among the inhabitants of the Jinzu River basin. From the participants of 1967 and 1968 health examinations, target subjects in whose hamlet the cadmium concentration in rice was known and whose history of residence was also known were selected. Cadmium concentrations in rice from data analyzed by the Toyama Prefecture from 1971 to 1976 were used. The urinary examination was done by semiquantitative determination of protein and glucose. All odds ratios for lifetime cadmium intake obtained from logistic regression analysis were more than 1 in both males and females who had resided in their current hamlet since birth with and without subjects who moved from nonpolluted areas and with or without the control group. The allowable levels of lifetime cadmium intake were calculated by substituting the abnormality rates of urinary findings of the controls 40, 50, 60, and 70 yr old into the logistic regression formula. The allowable levels of lifetime cadmium intake were less than 1.58 g for both sexes and each age group using proteinuria with glucosuria measurements.     

Association between urinary calcium excretion level and mortality in inhabitants of the Jinzu River basin area of Japan

A follow-up study on 5442 inhabitants (2699 men, 2743 women) was conducted to determine the association between urinary Ca excretion level and mortality of the general population of three different areas of the Jinzu River basin area, namely, non-Jinzu River, mixed, and the Jinzu River water systems, over a period of 6127 d. More than 98% of the subjects were followed completely in each area. In comparison with the low- and high-Ca-excretion groups (cutoff values; 25.1 mg/dL in men, 20.4 mg/dL in women), the mortality rates per 1000 person-years and standardized mortality ratios (SMRs) tended to be greater in the low-Ca-excretion groups than in the high-Ca-excretion groups in both sexes for each of the three areas. Moreover, Cox’s hazard ratios in men and women of the three areas exhibited negative values, 0.99 except for men of the mixed water system. These values were statistically significant in both sexes for the Jinzu River water system and in women for the non-Jinzu River water system. We conclude that the life-span becomes shorter as urinary Ca excretion levels become lower.     

Smoking does not influence cadmium concentrations in blood and urine in relatively high levels of environmental cadmium areas in Japan

We examined how the influence of smoking on blood and urinary cadmium (Cd) concentrations was modified by the level of environmental Cd. We measured blood and urinary Cd concentrations of 1134 men over 50 yr of age in three areas in Japan that were exposed to different levels of environmental Cd. Analysis of variance was used to compare Cd concentrations in blood and urine of smokers with those of nonsmokers living in the three areas. Correlation coefficients between the number of cigarets smoked per day or smoking indices (the number of cigarets smoked per day multiplied by the number of years smoked) and blood and urinary Cd concentrations were calculated. No significant difference in Cd concentrations between smokers and nonsmokers was observed in areas where the average Cd concentration in blood was over approx 2.4 ng/g, 2.0 μg/L in urine, and 2.3 μg/g creatinine in urine, respectively. Therefore, it was suggested that an influence of smoking on blood and urinary Cd concentrations was not observed in areas exposed to relatively high levels of environmental Cd.     

Influence of Drinking and/or Cooking with Jinzu River Water on the Development of Itai-Itai Disease

This study was undertaken to estimate the amount of cadmium (Cd) exposure needed for the development of Itai-itai disease and the influence of using Jinzu River water for drinking and/or cooking on its development. The subjects comprised 38 Itai-itai disease patients admitted both for questionnaire survey and medical testing. The period when the patients started to perceive leg/back pain was defined as ‘mild disease onset’ and that when they experienced the most severe manifestations such as ambulatory disturbance as ‘severe disease onset’. In a comparison of non-users/users of river water, mean age and lifetime Cd intake (LCd) estimated from the daily consumption of rice and other foods at the onset of mild or severe disease showed smaller values in the users than non-users. LCd in non-users/users of river water for drinking and/or cooking were estimated as 3.46–3.60 g/2.58–2.63 g at mild disease onset and 4.24–4.44 g/3.50–3.54 g at severe disease onset. A portion of the differences in LCd in non-users/users is attributable to the influence of Cd consumption from the use of river water, although it was suggested that LCd estimated from eating Cd-polluted rice exerted a greater influence on the development of Itai-itai disease than drinking and/or cooking with Cd-polluted river water.     

Sex Differences in Shotgun Proteome Analyses for Chronic Oral Intake of Cadmium in Mice

Environmental diseases related to cadmium exposure primarily develop owing to industrial wastewater pollution and/or contaminated food. In regions with high cadmium exposure in Japan, cadmium accumulation occurs primarily in the kidneys of individuals who are exposed to the metal. In contrast, in the itai-itai disease outbreak that occurred in the Jinzu River basin in Toyama Prefecture in Japan, cadmium primarily accumulated in the liver. On the other hand, high concentration of cadmium caused renal tubular disorder and osteomalacia (multiple bone fracture), probably resulting from the renal tubular dysfunction and additional pathology. In this study, we aimed to establish a mouse model of chronic cadmium intake. We administered cadmium-containing drinking water (32 mg/l) to female and male mice ad libitum for 11 weeks. Metal analysis using inductively coupled plasma mass spectrometry revealed that cadmium accumulated in the kidneys (927 x 10 + 185 ng/g in females and 661 x 10 + 101 ng/g in males), liver (397 x 10 + 199 ng/g in females and 238 x 10 + 652 ng/g in males), and thyroid gland (293 + 93.7 ng/g in females and 129 + 72.7 ng/g in males) of mice. Female mice showed higher cadmium accumulation in the kidney, liver, and thyroid gland than males did (p = 0.00345, p = 0.00213, and p = 0.0331, respectively). Shotgun proteome analyses after chronic oral administration of cadmium revealed that protein levels of glutathione S-transferase Mu2, Mu4, and Mu7 decreased in the liver, and those of A1 and A2 decreased in the kidneys in both female and male mice.     

Environmental cadmium exposure and forearm bone density

Environmental exposure to cadmium may give rise to osteomalacia combined with renal dysfunction, so called 'Itai-Itai disease', which was endemic in the heavily polluted area in Japan. The main focus of this study was to investigate whether environmental exposure to cadmium is associated with low bone mass in a population living near a smelter. A total of 790 persons (302 males and 488 females), who were all over 35 years old and resided in areas near a lead, zinc and cadmium smelter and in a control area in southeast China, completed a questionnaire, and bone mineral density was measured by SPA-4 single photon absorptiometry at the radius and ulna. Cadmium content of urine was determined by graphite-furnace atomic absorption spectrophotometry as a measure of dose. The present study shows that forearm bone densities were negatively correlated with urinary cadmium excretion (p < 0.001) and forearm bone density decreased linearly with age (p < 0.001) and urinary cadmium (p < 0.01), suggesting a dose-effect relationship between cadmium dose and bone mineral density. Based on the World Health Organization criteria, (bone mineral density < -2.5 SDs below the normal young adult), the prevalence of osteoporosis in women increased from 34.0% in the control area to 51.9% in the heavily polluted area (p < 0.01) among subjects over 50 years old, and the odds ratio value was 2.09 (95% CI: 1.08-4.03) for the highly polluted area compared with the control area. A striking observation in the study was a marked increase of the prevalence of fracture in the cadmium-polluted area in both sexes. It was concluded that environmental exposure to cadmium is associated with an increased loss of bone mineral density in both gender, leading to osteoporosis and increased risk of fractures, especially in the elderly and in females.     

Mortality in a cadmium polluted area in Japan

A 15-year follow-up study of 3178 inhabitants (1424 men and 1754 women) living in the cadmium (Cd) polluted Kakehashi River basin was conducted. The results clarified effects on mortality of renal dysfunction induced by Cd indicated by urinary beta-2-microglobulin (beta2-MG), total protein, glucose, and total amino acids. This study used Cox's proportional hazard model. The mortality risk ratio of urinary beta2-MG positive (>= 1000 microg/gCr) subjects was significantly increased in both sexes: 1.35 for men and 1.73 for women. The increased mortality ratio of the urinary protein positive (>= 10 mg/dl) subjects was also significant for both sexes, with risk ratios of 1.82 for men and 2.01 for women. Only the women showed significantly increased mortality of the urinary glucose positive (>= 20 mg/dl) subjects and amino acids positive (> = 300 microg/gCr) subjects. When the subjects were divided into four categories according to urinary beta2-MG, <300, 300-1000, 1000-10000, >= 10000 microg/gCr, the mortality risk ratios were increased in proportion to the increase of urinary beta2-MG in both sexes. These results suggest that mortality of Cd-exposed subjects increased with increasing excretion of four urinary markers of renal tubular dysfunction, and in proportion to increases in the amount of urinary beta2-MG excretion including under 1000 microg/gCr.     

Excretion levels of urinary calcium and phosphorus among the inhabitants of Cd-polluted Kakehashi River basin of Japan

Bone damage caused by exposure to cadmium (Cd) is often seen in Cd-polluted areas, and increased excretion of calcium (Ca) in urine is thought to be an important factor affecting bone damage. In order to clarify the significance of urinary Ca excretion in bone damage, we investigated the urinary excretion levels of Ca and phosphorus (P) of inhabitants of a Cd-polluted area and compared them to those of nonexposed subjects, and explored the possible association between urinary Ca or P and β ₂-microglobulin (β ₂-MG). The target subjects were 3164 inhabitants of the Cd-polluted Kakehashi River basin. Ca and Ca/P measurements were significantly higher in the Cd-polluted area than in the controls. In multiple-regression analysis, where either Ca or P was used as the criterion variable, and age, Cd, and β ₂-MG were used as explanatory variables, there were positive associations between Ca and Cd and β ₂-MG in both sexes. Therefore, the increased excretion level of Ca was the result of renal dysfunction. Bone damage is not thought to be caused by increased excretion of Ca alone because urinary excretion levels of Ca do not differ greatly between people with and without bone damage.     

河北主要土壤中Cd、Pb形态与油菜有效性的关系

当今土壤重金属污染日趋严重而表征土壤污染程度 的指标不够完善、相关性亦较差。为此,采用网室盆栽试验,研究了河北平原主要土壤类型潮土和潮褐土上Cd、Pb的化学形态特征及其与油菜植株干物重、油菜吸收重金属含量的关系。结果表明Cd对油菜的毒害作用大于Pb。总量及各形态Cd、Pb含量与油菜可食部分干物重呈负相关,对油菜干物重影响最大的是交换态Cd、Pb。而对油菜吸收Cd、Pb贡献最大的形态是碳酸盐结合态和铁锰氧化物结合态。深入研究重金属形成与植物有效性间的关系,可为进一步揭示重金属的生物有效性,为更准确评价土壤重金属污染程度提供理论依据,具有重要的理论意义和实际应用价值。     

不同性别桑树幼苗对镉与酸雨复合处理的生长响应及镉积累差异

为研究不同性别桑树在镉(Cd)与酸雨(AR)复合处理条件下的生长与镉积累差异,本试验以‘强桑1号’(雌株)和‘农桑14号’(雄株)两种不同性别桑树为材料,研究重金属镉(100 mg·kg^-1干土)和模拟酸雨(pH 3.0)处理下,两者生物量积累和分配、最大净光合速率(A_max)和叶绿素荧光参数,以及Cd积累与分配的差异.试验共设置无Cd和AR(对照)、单独Cd、单独AR、Cd+AR复合4个处理.结果表明:单独Cd处理虽然显著增加了雌株和雄株根茎叶中Cd含量,而且雌株各部分Cd含量显著高于雄株,但是只有雄株根、茎和总生物量、最大净光合速率显著下降,而雌株除了A_max显著下降外,各部分生物量积累下降均不显著,且两者的最大光化学效率(F_v/F_m)、光化学淬灭系数(q_P)和非光化学淬灭系数(q_N)均未发生显著变化.复合处理下,雄株和雌株的总生物量、A_max均显著降低,与单独镉处理相比,雌株根和叶中的Cd含量显著升高,但雄株没有明显变化,两者的F_v/F_m、q_P没有显著变化,但q_N均显著降低.短时间处理下桑树雌株对单独镉胁迫的耐受性高于雄株,但是酸雨的加入会降低雌株对镉的耐受性,可能是因为酸雨促进雌株根系对镉的吸收,并导致叶片积累了更多的镉.     

A multi-level approach using Gambusia affinis as a bioindicator of environmental pollution in the middle-lower basin of Suquía River

The Suquía River middle-lower basin (Córdoba, Argentina) is subjected to a strong anthropogenic impact because it receives pollutants from different sources. The main goal of this study was to evaluate the introduced fish species Gambusia affinis as a bioindicator of environmental pollution in the middle-lower basin of the Suquía River. The assessment was performed by measuring biomarkers at different levels of biological organization, at two sampling sites (before and after Córdoba city), and at dry and wet seasons. Water quality evaluation was made through a water-quality index (based on physico-chemical parameters), heavy-metals and pesticides concentrations in water. The water quality varied between sampling sites, showing the most degraded conditions downstream Córdoba city. The same pattern of variation was detected in the biomarkers studied, mainly in: gill and liver histopathological indexes, copulatory organ (gonopodium) morphology and vitellogenin expression in males and females. The present study characterized the environmental conditions in the middle-lower basin of the Suquía River and revealed the low freshwater quality at the most polluted site. Although G. affinis is an introduced species, it could be considered a good sentinel of water resource quality of invaded Neotropical basins. Our results demonstrated the importance of addressing the environmental quality monitoring through an integrated analysis of water quality parameters together with histological, morphological and molecular parameters. Thus, our study provides a good model for application in other basins of South America.     

四种抗寒花卉对镉的生理响应和富集特征

以矮型四季菊、羽扇豆、欧报春和虞美人等冬春季常见花卉为试验材料,通过盆栽试验,研究了不同浓度Cd处理下4种花卉对Cd的生理响应和富集特征,探讨利用这4种花卉在冬春季寒冷时期修复Cd污染土壤的可行性,为提高植物修复技术的效率提供参考。结果表明:(1)在所有Cd处理下,羽扇豆各部位生物量与对照均无差异;欧报春仅根系生物量在80 mg·kg^-1Cd处理时显著低于对照,为对照的74.51%;矮型四季菊和虞美人全株生物量分别在Cd处理浓度高于10、40 mg·kg^-1时开始显著低于对照,并在80 mg·kg^-1Cd处理时全株生物量均达到最小值,分别为对照的41.21%和64.15%。(2)在所有Cd处理下,羽扇豆体内抗氧化酶活性均显著高于对照,MDA含量与对照无显著性差异,清除活性氧能力最强,未受到伤害;欧报春体内抗氧化酶活性升高幅度较小,MDA含量和REC有小幅度增加,清除活性氧的能力较强,受到的伤害程度较低;矮型四季菊和虞美人对活性氧清除能力最差,受到了严重的氧化伤害。(3)在所有Cd处理下,Cd在矮型四季菊体内的分布均为地上部>根系,BCF和TF均大于1,地上部含量和富集量最大值分别为136.20mg·kg^-1和1118.20μg·plant^-1;Cd在羽扇豆、欧报春、虞美人体内表现为地上部<根系,TF均小于1,地上部Cd含量、富集量、BCF和TF均为羽扇豆>欧报春、虞美人。综上所述,与欧报春和虞美人相比,矮型四季菊对Cd耐性相对较差,但对Cd有较强的吸收转移能力,适合用于冬春季Cd污染土壤的修复;羽扇豆对Cd的耐性强,对Cd吸收转移能力也较强,也适合用于冬春季Cd污染土壤的修复。     

Effects of inoculation with arbuscular mycorrhizal fungi on photosynthetic physiology in females and males of Populus deltoides exposed to cadmium pollution

Aims Populus deltoides is an important plantation tree species in the middle and lower reaches of the Yangtze River and in Huai River Plain. The extensively cultivated varieties are consisted of both females and males of P. deltoides. The objective of this paper was to characterize the difference in cadmium (Cd) tolerance between the sexes and the effects of symbiosis with Rhizophagus intraradices on their Cd tolerance.
Methods The experiment was carried out under semi-controlled conditions in a natural light greenhouse, protected from rain. Rhizophagus intraradices was inoculated on roots of both females and males when transplanting to a sand culture substrate. After one month, half of cuttings were exposed to Cd pollution (10 mg·kg^-1). All cuttings were irrigated with sterile water to avoid infection by other microorganism. About three months later, the gas exchange rate, net photosynthesis rate (P_n)-intercellular CO₂ concentration (C_i) curve, chlorophyll fluorescence, osmotic adjustment and phytohormone content of both females and males of P. deltoides were measured.
Important findings Our main results are as follows: (1) when compared to the controls, decreases in P_n, stomatal conductance, C_i, transpiration rate, maximum photochemical efficiency of photosystem II (PSII), effective quantum yield of PSII, photo-chemical quenching coefficient, maximum rate of carboxylation of Rubisco, photosynthetically active radiation-saturated rate of electron transport and rate of triose phosphate utilization to a different degree in both sexes of P. deltoides under Cd pollution were found, and females exhibited a greater decrease in such parameters than males. Rhizophagus intraradices inoculation mitigated the toxic effect of Cd on such parameters to a different degree in females, not in males. (2) Under Cd pollution, there was an increase in proline content in both sexes when compared to the controls. A further increase in proline content occurred in females, not in males, when inoculated with R. intraradices. (3) When compared to the controls, there was a decrease in indoleacetic acid, but an increase in abscisic acid in leaves of both sexes when exposed to Cd pollution. The amplitude changed in both phytohormones in females was greater than that in males. Rhizophagus intraradices inoculation was helpful for recovery of phytohormone balance in females, which was not observed in males. Therefore, our results indicated that (1) there were a greater negative effect exerted by Cd pollution on gas exchange rate, carbon fixation capacity and phytohormone balance and a more impairment of photosynthetic apparatus in females when compared to males, showing a less tolerance to stress conditions in females; (2) Rhizophagus intraradices inoculation could enhance the osmotic adjustment capacity in females, thus mitigate the negative effect of Cd stress on ability of carbon fixation and phytohormone balance in females. However, such positive effects derived from R. intraradices symbiosis were not observed in males.     

Disturbance of the indigenous gene pool of the threatened brook lamprey Lethenteron sp. S by intraspecific introgression and habitat fragmentation

Artificial introduction and habitat fragmentation affect the indigenous gene pools of fluvial animals. To investigate the effect of human activities on the genetic population structure of vulnerable brook lamprey Lethenteron sp. S in a single river system, samples from 12 tributaries of the Jinzu River, Japan, were analyzed using mitochondrial and microsatellite DNA markers. Exogenous Lake Biwa (Japan) haplotypes and alleles were detected in lampreys from several Jinzu River tributaries. Since Lake Biwa is the source of the commercial ayu fish Plecoglossus altivelis that is introduced in the Jinzu River, the exogenous Lake Biwa lamprey genotypes in the Jinzu River probably originated from the Lake Biwa lampreys that were unintentionally introduced along with the ayu fish. Bayesian admixture and mitochondrial DNA analyses revealed various genetic disturbance phases of the exogenous genotypes in the Jinzu River, such as the six indigenous populations, four admixed populations with low frequencies (average admixture proportion = 0.02–0.04; exogenous haplotype proportion <0.01), one introgressed population (0.71 and 0.57) and one population almost displaced by exogenous genotypes (0.93 and 0.96). Samples from three tributaries with weirs were genetically differentiated from the others by using pairwise F _ST and Bayesian analyses; the results suggested isolation by the weirs. Reduced mitochondrial DNA diversity was observed in 1 of the 3 samples probably due to reduced population size. These findings indicate that the indigenous lamprey populations in the Jinzu River are seriously affected by introgression with exogenous genotypes via unintentional introduction and habitat fragmentation by weirs.     

Effects of Cd on Uptake of P in Potato Grown in Sierozems

The effects of Cd on the bioaccumulation of P in soil-plant system have aroused wide interest and been widely explored. Sierozem has been contaminated by Cd in many areas in Northwest China. To investigate the effects of Cd on the uptake and translocation of P in plants in sierozem, pot experiments were carried out by cultivating potato (Solanum tuberosum L.) under Cd treatment. The fractions of Cd in the soil were examined by soil extraction; available P in the soil was determined; Cd and P accumulation in the plants was also determined. The result of the soil extraction shows that the acid-soluble Cd fraction gradually became the main fraction with the increasing Cd concentrations in the soil. This suggests that the change in the main fraction of Cd may promote the uptake of Cd in plants because acid-soluble Cd fraction may be utilized easily by plants. Given increasing Cd concentrations in the soil, Cd concentrations increased in each part of potato plants, whereas the soil available P and plant P contents were decreased. These results indicate that increasing Cd concentrations in sierozems exerts negative effects on the uptake and translocation of P in plants.     

土壤水分变化对玉米苗期吸收积累镉的影响

采用土壤盆栽试验研究不同土壤水分含量对玉米苗期吸收积累 Cd的影响。试验结果表明 ,玉米生物量及其吸收 Cd量在玉米不同的生长时期差异较大。2 2 d收获时 ,玉米地上部和地下部生物量均随着田间持水量 (35 %～ 85 % )的增加而提高 ;而 16 d收获时 ,玉米生物量在田间持水量为 35 %和 85 %时比在其它水分时低许多。 16 d和 2 2 d收获时 ,玉米地上部 Cd含量在田间持水量 5 5 %时分别达到最大值 ,5 5 .4 1mg/ kg和 39.33mg/ kg;而在田间持水量 85 %时分别达最小值 ,2 7.97mg/ kg和 2 3.5 2 m g/kg。在玉米根系的影响下 ,土壤溶液 Cd含量基本上随着玉米的不断生长而降低。田间持水量为 6 5 %时的土壤溶液 Cd含量比田间持水量为 75 %和 85 %时大。玉米总吸 Cd量与水分蒸腾量之间呈极显著的线性正相关关系     

水稻根表铁膜吸附镉及植株吸收镉的动态

采用营养液培养法研究了Cd处理时间对有铁膜和无铁膜水稻根表吸附Cd及植株吸收Cd动态变化的影响.水稻根表铁膜由50 mg·L^-1 Fe^2＋（Fe₅₀）诱导形成.供试植株在含10 μmol·L^-1Cd的营养液中生长不同时间后收获.结果表明, 随Cd处理时间的延长,无铁膜和有铁膜处理水稻根表DCB-Cd含量均为先增加后减少,Cd处理2 h达到最高,之后逐渐下降并趋于稳定. 根系和地上部Cd含量均持续上升,Cd处理8 h前增加缓慢,8 h后增加幅度加大.有铁膜水稻根系和地上部Cd含量增加幅度均低于无铁膜水稻.有铁膜处理DCB-Cd含量、根系和地上部Cd含量均低于无铁膜处理.表明铁膜不影响水稻各部分Cd含量随时间的变化趋势;不同Fe处理之间根系和地上部Cd含量的差异可能与根系含Fe量有关.     

Assessment of Heavy Metal Contamination in the Surrounding Soils and Surface Sediments in Xiawangang River,Qingshuitang District

Xiawanggang River region is considered to be one of the most polluted areas in China due to its huge amount discharge of pollutants and accumulation for years. As it is one branch of Xiang River and the area downstream is Changsha city, the capital of Hunan Province, the ecological niche of Xiawangang River is very important. The pollution treatment in this area was emphasized in the Twelfth Five-Year Plan of Chinese government for Xiang River Water Environmental Pollution Control. In order to assess the heavy metal pollution and provide the base information in this region for The Twelfth Five-Year Plan, contents and fractions of four heavy metals (Cd, Cu, Pb and Zn) covering both sediments and soils were analyzed to study their contamination state. Three different indexes were applied to assess the pollution extent. The results showed this area was severely polluted by the four heavy metals, and the total concentrations exceeded the Chinese environmental quality standard for soil, grade III, especially for Cd. Moreover, Cd, rated as being in high risk, had a high mobility as its great contents of exchangeable and carbonates fractions in spite of its relative low content. Regression analysis revealed clay could well explain the regression equation for Cd, Cu and Zn while pH and sand could significantly interpret the regression equation for Pb. Moreover, there was a significant correlation between Non-residual fraction and I_geo for all the four metals. Correlation analysis showed four metals maybe had similar pollution sources.