Evaluation of a sequential extraction for the speciation of thorium in soils from Baotou area, Inner Mongolia

Sequential extraction procedures were widely applied for speciation of radioactive elements. In this study, the sequential extraction procedure developed by Martinez-Aguirre was employed for quantification of different chemical forms of thorium in the soil. The total amount of thorium in contaminated soil was much higher by four-fold than the local background value. The soil properties affect the amount of thoriurn and distribution of fractions in contaminated soil. Results showed that the proportion of thorium in soils from Baotou was found as the residual fraction (F5 + F6) > absorbed fraction (F3), coprecipitated fraction (F4) > carbonates fraction (172) and exchangeable fraction (F1) that could be available to plants. The recovery, calculated by ratio of the sum of the six fractions to the pseudo-total content of thorium, was in the range from 96% to 110%. A comparison was carried out between the sequential extraction and the single extraction to evaluate the selectivity of the extractants. It was found that the amount of thorium of absorbed fraction (H) was higher in the single extraction than that estimated in the sequential extraction, possibly duo to transform of the labile form. While for non-residual fraction analysis, the single extraction scheme was a desirable alternative to the sequential extraction procedure.

Thermodynamic behavior and applications of KMnO4 in cerium separation process using cyanex 923

In this work, studies were carried out on the extraction properties of Mn(II) and MnO4- in sulfuric acid medium using Cyanex 923. Effects of different variables on the extraction of Mn(II) and MnO4-, such as the concentrations of acid, the extractant, and the temperature, were investigated. Results indicated that Mn(II) was extracted weakly by Cyanex 923; however, MnO4- could be strongly extracted into the organic phase. The extraction mechanism of MnO4- was proposed, and the influence of MnO4- on the extraction of cerium was identified when KMnO4 as oxidizer added into the bastnasite sulfuric acid leaching liquor. As MnO4- was easier to be extracted into the organic phase than Ce(IV) and then lost its ability for oxidization, a new device was designed to realize sufficient oxidization of cerium from III to IV, and which has been applied to industrialization.

Alteration of metallothionein mRNA in bay scallop Argopecten irradians under cadmium exposure and bacteria challenge

Metallothionein (MT) is a superfamily of cysteine-rich proteins contributing to metal metabolism, detoxification of heavy metals, and immune response such as protecting against ionizing radiation and antioxidant defense. A metallothionein (designated AiMT2) gene was identified and cloned from bay scallop, Argopecten irradians. The full length cDNA of AiMT2 consisted of an open reading frame (ORF) of 333 bp encoding a protein of 110 amino acids. with nine characteristic Cys-X-Cys, five Cys-X-X-Cys, five Cys-X-X-X-Cys and two Cys-Cys motif arrangements and a conserved structural pattern Cys-x-Cys-x(3)-Cys-Tyr-x(3)Cys-x-Cys-x(3)-Cys-x-Cys-Arg at the C-terminus. The cloned ANT showed about 50% identity in the deduced amino acid sequence with previously published MT sequences of mussels and oysters. The conserved structural pattern and the close phylogenetic relationship of AiMT2 shared with MTs from other mollusc especially bivalves indicated that AiMT2 was a new member of molluscan MT family. The mRNA transcripts in hemolymph of AiMT2 under cadmium (Cd) exposure and bacteria challenge were examined by real-time RT-PCR. The mRNA expression of AiMT2 was up-regulated to 3.99-fold at 2 h after Listonella anguillarum challenge, and increased drastically to 66.12-fold and 126.96-fold at 16 and 32 h post-challenge respectively. Cadmium ion exposure could induce the expression of AiMT2, and the expression level increased 2.56-fold and 6.91-fold in hemolymph respectively after a 10-day exposure of 100 mu g L-1 and 200 mu g L-1 CdCl2. The sensitivity of AiMT2 to bacteria challenge and cadmium stress indicated it was a new Cd-dependent MT in bay scallop and also regulated by an immune challenge. The changes in the expression of AiMT2 could be used as an indicator of exposure to metals in pollution monitoring programs and oxidative stress, and bay scallop as a potential sentinel organism for the cadmium contamination in aquatic environment. (C) 2008 Elsevier Inc. All rights reserved.

cDNA cloning and mRNA expression of heat shock protein 90 gene in the haemocytes of Zhikong scallop Chlamys farreri

Heat shock protein 90 (HSP90) is a highly conserved molecular chaperone contributing to the folding, maintenance of structural integrity and proper regulation of a subset of cytosolic proteins. The full-length cDNA of Zhikong scallop Chlamysfarreri HSP90 (designated CfHSP90) was cloned by EST and rapid RACE techniques. It was of 2710 bp, including an open reading frame (ORF) of 2181 bp encoding a polypeptide of 726 amino acids with all the five HSP90 family signatures. BLAST analysis revealed that the CfHSP90 gene shared high similarity with other known HSP90 genes. Fluorescent real-time quantitative RT-PCR was used to examine the expression pattern of CfHSP90 mRNA in haemocytes of scallops exposed to Cd2+, Pb2+ and Cu2+ for 10 and 20 days, respectively. All the three heavy metals could induce CfHSP90 expression. There was a clear dose-dependent expression pattern of CfHSP90 after heavy metals exposure for 10 days or 20 days. Different concentrations of the same metal resulted in different effects on CfHSP90 expression. The results indicated that CfHSP90 responded to various heavy metal stresses with a dose-dependent expression pattern as well as exposure time effect, and could be used as a molecular biomarker in a heavy metal polluted environment. (c) 2007 Elsevier Inc. All rights reserved.

南黄海重金属的演变特征及控制因素

本文以南黄海1997～2006年10年表层海水和沉积物中重金属为主要研究对象，同时结合对生态环境信息的综合分析，系统探讨了海水和沉积物中重金属的生物地球化学特征、影响控制因素、演变趋势，并对海域生态风险进行了评估，获得了以下一系列新的结果和认识： 1．系统获得了南黄海海水和沉积物中重金属的地球化学分布模式，揭示了影响和控制其生物地球化学特征的因素 南黄海表层海水中重金属As、Cd、Cu、Hg、Pb、Zn的平均浓度分别为2.33、0.078、1.41、0.0036、0.37、6.21 μg/L，低于其它中国近海海水，而高于水交换较好的深海；表层海水重金属的分布模式（除Pb外）表现为在离岸较远的南黄海中部地区其含量较低，而近岸海区则普遍含量较高，区域分布呈现“高Cd-Cu-Hg-Zn区”，“高Pb-Cu-Zn区”以及“高Pb区”三个地球化学分区。 南黄海表层沉积物中重金属比邻近海域沉积物中的浓度低，南黄海重金属主要受沉积物粒度控制，即在细粒度高的南黄海中部区域重金属（除As外）的含量较高，粗粒度的近岸区则较低，区域分布呈现“高Cd-Cu-Pb-Zn区”，“高Hg低As-Cu-Zn区”以及“高As低Cd-Hg-Zn区”三个地球化学分区。 人类活动已经显著影响了南黄海海水中重金属的含量水平，重金属分布是径流、大气沉降、pH、盐度和重金属自身性质等各种影响因子耦合的结果。沉积物重金属的富集因子Pb>As>Hg>Cd>Zn>Cr>Cu，其中Pb和As主要来自人为污染排放，污染状况相对较重，Cr和Cu几乎没有受到人为污染的影响。沉积物的粒度是控制表层沉积物重金属分布的最主要因素，次要的因素包括沉积物有机质的含量、沉积速率以及重金属存在形态等。 2．首次获得了南黄海海水和沉积物中重金属的演变趋势 近10年来南黄海表层海水中，Zn呈上升趋势，As、Cd、Cu、Pb基本稳定变化不大，而Hg则呈略下降趋势。Zn的线性上升趋势明显，在近岸水域和中央水域中其浓度和公元年的统计关系分别为y=0.9524x+0.0034（R=0.97）和y=0.8622x+0.0299（R=0.95）（其中y为Zn的浓度，x为年度，取1997～2004）。近10年沉积物中重金属年际变化较小，浓度变化在多年均值的±（10%～30%）之间变动。As、Cd、Cu、Hg、Pb、Zn的均值变化范围分别为7.17±1.70、0.108±0.024、17.61±1.65、0.024±0.008、18.44±4.26、70.53±5.73 mg/kg，除了Hg随公元年呈较好的线性增加（y=0.0033x-6.50，R=0.75）外，其它重金属未显现出有明显的演变趋势。 近百年来，南黄海重金属的变化可分为3个阶段，20世纪60年代以前，20世纪60年代至90年代，及20世纪90年代至今。第一个阶段的60年可以看作是南黄海未明显受人类活动影响的一个时期，该段时期内明显的特征是重金属含量的变化受径流输入不均等多种因素影响，变化规律性不强；第二阶段是南黄海近岸工农业迅猛发展的阶段，由近岸传输到这一海域的重金属量增加，南黄海沉积物重金属浓度增加，沉积物质量有下降的趋势，这一阶段是人类活动影响南黄海最为明显的一个阶段；第三个阶段是20世纪90年代至今，南黄海沉积物重金属浓度呈降低趋势，与中韩两国减排及治污措施有关。近几年，南黄海沉积物的环境质量较20世纪末期有了较明显的改善。 3. 初步阐明了南黄海重金属的环境污染危害和潜在生态风险 采用潜在生态危害指数法和地积累指数等方法对南黄海沉积环境进行分析，结果表明，中等重金属污染程度海区占研究海区面积的38.7%，中等生态风险的区域则占了研究海区面积77.8%，但均未发现沉积物中的重金属与生物量的分布有明显的关系，总体表明，南黄海沉积物中的重金的污染状况及生态风险较低，南黄海沉积物质量良好。

Assessment of metal contamination in surface sediments of Jiaozhou Bay, Qingdao, China

An assessment of metal contamination in surface sediments of the Jiaozhou Bay, Qingdao, one of the rapidly developing coastal economic zones in China, is provided. Sediments were collected from 10 stations and a total of 15 heavy metals were analyzed. Concentrations of metals show significant variability and range from 210 to 620 ppm for Ti, 2.7 to 23 ppm for Ni, 4.2 to 28 ppm for Cu, 5.2 to 18 ppm for Pb, 12 to 58 ppm for Zn, 0.03 to 0.11 ppm for Cd, 5 to 51 ppm for Cr, 1.5 to 9.9 ppm for Co, 5.3 to 19 ppm for As, 12 to 32 ppm for Se, and 19 to 97 ppm for Sr. Based on concentration relationships and enrichment factor (EF) analyses, the results indicate that sediment grain size and organic matter played important roles in controlling the distribution of the heavy metals in surface sediments of the Jiaozhou Bay. The study shows that the sediment of the Jiaozhou Bay has been contaminated by heavy metals to various degrees, with prominent arsenic contributing the most to the contamination. The analysis suggests that the major sources of metal contamination in the Jiaozhou Bay are land-based anthropogenic ones, such as discharge of industrial waste water and municipal sewage and run-off. Notably, the elevated heavy metal concentrations of the Jiaozhou Bay sediments could have a significant impact on the bay's ecosystem. With the rapid economic development and urbanization around the Jiaozhou Bay, coastal management and pollution control should focus on these contaminant sources, as well as provide ongoing monitoring studies of heavy metal contamination within the bay.

Biosorption of copper(II) from aqueous solutions by green alga Cladophora fascicularis

Biosorption is an effective means of removal of heavy metals from wastewater. In this work the biosorption behavior of Cladophora fascicularis was investigated as a function of pH, amount of biosorbent, initial Cu2+ concentration, temperature, and co-existing ions. Adsorption equilibria were well described by Langmuir isotherm models. The enthalpy change for the biosorption process was found to be 6.86 kJ mol(-1) by use of the Langmuir constant b. The biosorption process was found to be rapid in the first 30 min. The presence of co-existing cations such as Na+, K+, Mg2+, and Ca2+ and anions such as chloride, nitrate, sulfate, and acetate did not significantly affect uptake of Cu2+ whereas EDTA substantially affected adsorption of the metal. When experiments were performed with different desorbents the results indicated that EDTA was an efficient desorbent for the recovery of Cu2+ from biomass. IR spectral analysis suggested amido or hydroxy, C=O, and C-O could combine strongly with Cu2+.

Meat characteristics of Qinghai yak and semi-wild yak

Six domestic yaks aged 6 years, comprising three culling male and three culling female yaks, from the Qinghai Lake area and three male semi-wild yaks aged 6 months from Datong Yak Farm were used to detect the levels of amino acids, mineral elements, residual heavy metals and pesticides in yak meat. The results showed that there was little difference in amino acid levels for different types of yak by age and sex. The meat of the adult male yak was 7.35 mg/kg higher in calcium (P < 0.05) and 124 mg/kg higher in phosphorus (P < 0.01) than that of the adult female yak. There was an obvious difference in zinc content, and there was also a significant difference for copper and sulfur between adult male and female yaks (P < 0.01). Iron was 8.85 mg/kg higher in semi-wild yaks than in domestic yaks, but there were no differences for other minerals. The levels of residual heavy metals and residual pesticides were well within those allowed by the National Standard of China. Furthermore, the data showed that introducing wild yak's blood did not result in a quality change in the domestic yak meat. Yak meat from Qinghai Plateau has the characteristics of being non-polluted and rich in amino acids in comparison with local yellow cattle meat.

高温实验中重金属钼在硅酸盐熔体中的含量研究

This dissertation discusses current status of high temperature and high pressure and focuses on analyzing systematically the solubility of heavy metals in the silicate magma in HTHP experiments. The high temperature study on the content of heavy metal molybdenum in the silicate melts in this dissertation, which is granted, based on the geology mineralization model and the theory of HTHP experiments and combined with mineralization grade and geochemical nature of Mo, discusses the difference of mineralization between mantle plume and aqueous fluids and comes to the conclusions, which are as follows: (1) The content of Mo in the silicate melts is much greater than Mo mineralization grade. The molybdenum ore has the exploitation value when the industrial grade is higher than 0.06%. Mo content in different silicate melts varies because of the concentration of SiO2, that is, Mo content in the granodiorite is greater. (2) The content of Mo, which varies with reaction time, arises first and drops down in the alkali basalt melts, while variation is not too obvious in the granodiorite melts on the whole. (3) According to the picture of sample, the conclusion is not reached very well on some issues, such as the volatility and characteristic of molybdenum oxide and dependence on the geology environment.

贵阳市郊（喀斯特地区）菜园土重金属的生物地球化学循环与绿色作物生产

随着城市化进程的快速推进，大量蔬菜等食物由农村向城市输送，因此促进了城郊结合部蔬菜基地的发展。然而，城市化发展却导致越来越严重的城市和城郊土壤和大气污染，加上现代化生产中化肥和农用化学品的大量使用等，使得重金属在菜园土中大量积累，并可能通过食物链进入人体，威胁人类身体健康。因此，对重金属在土壤－蔬菜体系间迁移的生物地球化学行为的研究是我们了解和防治蔬菜重金属污染、促进绿色作物生产和保护人类健康的关键。 本文选择世界典型喀斯特地区的贵阳市市郊的菜园土－蔬菜体系为主要研究对象，通过系统地对土壤、主要蔬菜和大气沉降物质的元素分析以及铅同位素分析，对研究区域菜园土的主要理化性质、土壤（以及剖面）和蔬菜样品中重金属Cu、Pb、Zn和Cd的含量变化、菜园土以及土壤剖面重金属的形态分布等特征进行了研究。利用微量元素地球化学以及同位素地球化学理论，并结合土壤学研究理论和方法探讨了重金属在菜园土（石灰土和黄壤）和蔬菜体系间的赋存形态、重金属元素的来源、迁移与转化规律及其中的主要控制因素。 主要研究结果认为：贵阳市郊菜园土重金属元素含量变化与土壤母质显著相关，黄壤类型菜园土处于中度污染水平，石灰土类型菜园土处于轻度污染水平。菜园土中重金属形态以残余态为主，其次为有机结合态，再次为铁锰氧化物结合态和酸可提取态。土壤剖面中，菜园土表层大多数重金属含量高于背景剖面，其余各层吻合度较高。土壤剖面中重金属的形态分布仍以残余态为主，菜园土剖面上各元素的生物可利用态即酸可提取态、氧化物结合态和有机结合态则均要高于背景剖面，Pb和Zn主要受到有机结合态的影响，而Cd则三种形态的含量均高于背景剖面，种种迹象表明人为活动增加了菜园土重金属的活性和生物有效性，且以有机结合态的改变最为显著。 蔬菜中红薯可食部位的各项重金属富集系数均大于其他蔬菜，最容易受到土壤中重金属的影响；在土壤－蔬菜体系中，重金属元素含量的分布总体特征为菜园土>根>茎叶>果实，体系内元素的迁移在土壤/蔬菜根界面上最为关键，起着控制作用，此界面上各元素的迁移系数顺序为Cd>>Cu，Zn>Pb，大多数重金属元素在黄壤类型的菜园土中的迁移系数要小于石灰土类型的；在土壤－红薯和土壤－辣椒体系中，Cd的迁移系数随土壤pH的增加而降低，而其余元素的迁移系数则随土壤pH的增加而增加；土壤主成分与土壤理化性质对重金属形态分布有显著影响，但BCR连续提取法得到的土壤中重金属元素的各生物可利用态的含量与蔬菜根部的含量相关性不大；覆膜种植方式使土壤pH由4.5降低到3.8，并改变了其它物化参数，从而影响重金属的形态分布及其在蔬菜体内的含量分布特征，极可能增加农业系统中重金属的环境风险；铅稳定同位素分析表明，土壤中的铅主要来自于母岩的风化，蔬菜中放射成因铅明显略低于菜园土，菜园土和蔬菜中铅同位素组成在208Pb/206Pb对207Pb/206Pb的分布图上呈直线分布（在菜园土－蔬菜体系中，土壤样品、蔬菜不同部位的样品、以及雨水样品的铅同位素组成的分布也形成了极好的直线），显示明显的两端元混合体系；根据各端元物质铅同位素组成计算，土壤铅对蔬菜根部、茎叶的贡献值由71.8%~77.7%降低到16.0%~45.4%之间，大气铅的贡献则沿根向茎叶和果实逐渐增加，研究结果显示大气污染对蔬菜重金属Pb的贡献不可忽视。

贵阳市大气颗粒物、雨水及土壤中重金属的研究

重金属是指比重大于或等于5.0的金属。随着城市化在全球范围内的飞速发展，以及城市人口的不断增长，客观上需要增加对城市生态环境的了解，以及研究城市生态环境与人类健康之间的相互关系。 大气沉降包括干沉降与湿沉降，大气的干、湿沉降是大气化学、环境化学和生物地球化学研究的重要内容之一，在重金属循环中扮演着重要的角色。大气沉降对土壤重金属地球化学过程有着重要影响。因此，准确把握环境中重金属的主要来源、行为及归宿，对有效控制重金属的污染、保护人类健康提供科学依据具有非常重要的意义。城市土壤是城市生态环境的重要组成部分，对城市的可持续发展有着重要意义。在城市环境中，各种各样的人类活动将大量的重金属带人城市土壤中，造成这些元素在土壤中的积累，并通过大气、水体或食物链而直接或间接地威胁着人类的健康甚至生命。 本研究以贵阳为例，对环境中的重金属进行研究。系统研究了贵阳市大气颗粒物重金属含量与形态、雨水重金属的含量与季节变化及土壤重金属含量与形态。主要结果如下： 1 贵阳市的干、湿沉降与气象因子关系密切。随温度的升高，贵阳市TSP浓度下降；相对湿度与TSP呈负相关性；风速对贵阳市区的TSP浓度的影响主要表现为扩散和稀释作用，随风速的增加，贵阳TSP浓度降低；雨水对贵阳市大气总悬浮颗粒物的有明显的清除作用。随着风速的增加，贵阳市雨水中重金属含量降低；雨量与雨水中的Cd、Cr、Cu、Pb与Zn的含量均呈一定的负相关关系，总体趋势为当降雨量较大的时候，雨水中重金属的含量较低。 2 贵阳市大气颗粒物中重金属含量有明显季节变化规律。Cd、Cr、Pb和Zn冬季的含量明显高于其它季节，而春季和夏季颗粒物中重金属含量相对较低，冬季的浓度是夏季的1.8-4.6倍。同样，贵阳市雨水中Cr、Cu、Zn的最高浓度都出现在冬季，这与贵阳市在冬季大量使用燃煤来取暖的时段相符合。 3与其它城市相比，贵阳市大气颗粒物重金属污染比较严重。同样，与地表水国家标准值相比较，贵阳市大部分样品Cd、Cu、Pb与Zn明显超过地表水国家标准，雨水中Cd、Cu、Pb与Zn的平均值分别国家标准的为2.7、2.2、6.0和1.3倍。贵阳市表层土壤已受到重金属不同程度的污染。表层土壤Cd的平均含量为0.66mg/kg，Co的平均含量为17.31mg/kg，Cr的平均含量为82.91mg/kg，Cu的平均含量为52.20mg/kg，Ni的平均含量38.76mg/kg，Pb的平均含量为71.03 mg/kg，Zn的平均含量为216.05mg/kg。土壤Cd、Co、Cr、Cu、Ni、Pb和Zn的平均含量分别我国土壤元素的背景值的6.8倍、1.36倍、1.36倍、2.31倍、1.44倍、2.73倍与2.98倍，其中以Cd和Zn 积累较明显。 4对贵阳市大气颗粒物、土壤重金属形态分别进行分析，结果表明：大气颗粒物中Cd主要以环境可迁移态存在，占61.4%；Cr和Cu主要稳定态存在，二者对环境不会造成直接影响；Pb主要以环境可迁移态、碳酸盐和氧化物结合态存在；Zn主要以环境可迁移态存在。土壤中，除Cd以外，Co、Cr、Cu、Ni、Pb和Zn元素的酸可提取态在总的元素含量中所占比例较小，均小于总量的3.0%，而Cd的酸可提取态含量为23.3%。相反，除Cd以外，其它6种金属元素的残渣态含量都比较高，Zn为96.8%，Cr为92.2%，Cu为83.4%，Co为69.2%，Ni为57.4%，Pb为41.9%。 5 贵阳市土壤剖面重金属元素的分布比较混乱，没有规律性，底土层含量仍然很高。城市土壤受到人为因素等影响，已发生严重改变。土壤中有许多不同来源物质的混入，土壤剖面经常受到人为扰动，自然土壤发生层被破坏，导致许多土壤剖面上下土层没有发生学上的联系。

土壤中重金属活动性的唐南膜测定、模型模拟与污染的原位控制

土壤是自然环境的重要组成部分，是人类赖以生存与发展的宝贵资源。但是近年来我国土壤重金属污染日益严重，重金属污染物与其它类型的污染物相比具有隐蔽性、长期性与不可逆性等一系列特殊性，成为土壤中永久的污染物，最终通过食物链的传递进入人体，对人类的健康造成潜在的危害。因此，研究土壤重金属污染与控制具有很重要的意义。本论文首次将唐南膜平衡法（DonnanMembraneTechnique）和EcosAT（EquilibriumCalculationOfSpeciationAndTransport）模型引入我国土壤重金属活动性研究，并将两种方法获得的结果进行比较，互相验证，取得了较好的结果。还将两种方法结合探讨了贵州铝厂生产的赤泥对土壤中的游离重金属离子浓度的影响。土壤样品采于贵州都匀福锌矿地区，一个位于锅锌矿选厂尾矿坝下农田中的水稻土，以下简称坝下土，为重污染土；另一个位于锅锌矿上游桥边农田中的水稻土，以下简称桥边土，为轻污染土，本研究取得的主要结论与认识包括：1．作者对唐南膜平衡法进行了部分改进，用国内生产的JAM一I型均相离子交换膜替换Brwin等所用的BDH膜，既降低了实验的平衡时间，又经济实惠。另外还用KNO3溶液代替KNO3和Ca（NO3）2混合溶液作为实验的介质溶液，就可以避免由于国内土壤中Ca2+含量差异较大可能造成的误差。其它实验条件为：蠕动泵的流速为2.0ml／min，平衡时间为48小时。2．用柠檬酸体系（液一液体系）和土壤一水体系（固一液体系）检验了唐南膜平衡法，它可以在不扰动体系平衡的基础上同时测定同一体系中的多个游离金属离子浓度，而且各金属离子之间互不干扰。3．桥边土中的游离重金属离子浓度与其中2mol／LHNO3提取的重金属总含量成很好的直线关系，其中Cu和Zn游离离子浓度与其中的总金属含量呈现较好的正比关系，随着重金属总含量的降低，即土液比的降低，游离重金属离子浓度随之降低；而其中的Ni和Cd却相反，随着重金属总含量的降低，游离重金属离子浓度反而增加。添加赤泥后随着土液比的降低各重金属的游离离羲?子浓度的变化趋势与添加赤泥前一样。桥边土中的重金属游离离子浓度在添加联合法赤泥后有所增加，而拜尔法赤泥的加入降低了其中的游离重金属离子浓度，加入的比例越大，变化的量越多，而且其中Ni和cd的变化幅度比Cu和Zn的要大。4．坝下土中Cu、Zn、Ni和Cd元素的游离离子浓度与它们在土壤中Zmol／LHNo3提取的重金属总含量呈很夯的正比关系，随着重金属总含量的降低，游离重金属离子浓度随之降低。添加赤泥后其中Cu和Zn元素的变化趋势与添加赤泥前一样，Ni和Cd元素出现了异常，Ni在赤泥添加比例为0.50％时变化趋势一样，但添加比例为2.00％时其离子浓度先增加，但在土液比为1:100时反而有较大幅度的降低。而其中Cd离子浓度先增加，在土液比为1:100时反而有较大幅度的降低。坝下土中Cu和Zn的游离离子浓度在添加赤泥以后改变很小，赤泥添加比例为2.00％的土壤中的游离离子浓度相对较低一点，而添加比例为0.50％的与未加赤泥的土壤基本上一样；其中Ni和Cd的变化相对来说较大，赤泥添加比例为2.00％的土壤中的游离离子浓度降低得比较明显，拜尔法赤泥添加比例为0.50％的土壤也得到了较大的改善，而联合法赤泥添加比例为0.50％的却比未加赤泥的土壤中的还要高一点。5．利用ECOSAT模型模拟了本论文所涉及的实验中的游离重金属离子浓度，测量值与模拟值取得了较好的一致，除了Zn的误差较大以外，其它三个元素符合的很好，从而表明EC0sAT在土壤一水系统中的模拟取得了较好的结果。6．模拟了不同土液比土壤中各重金属元素在有机质、铁氧化物、粘土和唐南凝胶体这四种吸附相中的分配。发现在所研究的土壤样品中所有元素在粘土相中所占的比例很小，可以忽略不计，Cu主要分布在有机质相中，占80％左右，随着土液比的降低，其在有机质和唐南凝胶体相中的分配比例慢慢变小，而在铁氧化物中的比例越来越大；Zn主要分布在有机质和铁氧化物相中，各占40％左右；随着土液比的降低，Zn在有机质相中的比例增大，铁氧化物比例几乎不变，而唐南凝胶体所占比例逐渐减小；Ni基本上只分布在有机质和铁”氧化物相中，Cd则几乎只存在于有机质相中，它们的分布比例几乎不随土液比的改变而变化。7．无论在桥边土和坝下土中添加何种赤泥，添加的比例是多少，在添加赤泥前后土壤中重金属元素在各吸附相中的分配比变化很小，主要是有机质相所占比例稍微变小，而铁氧化物相相应的有一点增加。而对于不同的土液比，其变化趋势相同，只是变化幅度相对来说较大。

Uso agrícola de composto de lixo: estudo da transferência de metal pesado no sistema solo-cana-de-açúcar.

Este estudo buscou avaliar uma solução agronômica para a destinação do lixo urbano com a utilização de sua compostagem na adubação da cana-de-açúcar. A utilização de composto de lixo (CL) altera a dinâmica de matéria orgânica do solo, tendo um impacto sobre seus processos físicos, químicos, mineralógicos e biológicos, podendo ser benéfica, pois constitui uma importante fonte de nutrientes, mas pode também causar problemas, em médio e longo ´prazos por conter metais pesados, que podem contaminar os solos e até entrar na cadeia alimentar.