Effects of eggshell addition on calcium-deficient acid soils contaminated with heavy metals

The eggshell was used to remediate the contaminated soil by heavy metals. The eggshell addition decreased the available state of the heavy metals. The available calcium in the soil increased due to eggshell addition. The efficiency was investigated in different moisture conditions. In this study, effects of water conditions (flooded, wet, or dry) and eggshell dosages (0, 0.1, 1.0, and 10.0 g/kg soil, respectively) on pH variation, content of unavailable state of heavy metals, form of heavy metals, and available nutritious element calcium (Ca) in acid soils contaminated with heavy metals were investigated, respectively. The soil samples were continuously cultivated indoors and analyzed by toxicity characteristic leaching procedure and community bureau of reference (BCR) sequential extraction procedure. The results showed that the addition of eggshell could effectively improve the pH of acid soil and increase it to neutral level. Moreover, the contents of unavailable state of heavy metals Cu, Zn, and Cd increased significantly. Furthermore, when the soil was cultivated under the flooded condition with 1.0 g/kg eggshell, the unavailable state of Cu, Zn, and Cd increased the most, and these heavy metals were transformed into residual state. On the other hand, the amount of available state of Ca increased to 432.19 from 73.34 mg/kg with the addition of 1.0 g/kg eggshell, which indicated that the addition of eggshell dramatically improved the available state of Ca. Therefore, eggshell could ameliorate the soil environment as it led to the decrease of available heavy metals and improvement of fertilization effectively. In a word, this study indicates that the addition of eggshell would be a new potential method for remediation of acid field soils contaminated with heavy metals.     

连环湖阿木塔泡沉积物中重金属形态及其对环境影响分析

采用了BCR三步提取法,对连环湖阿木塔泡AMT岩芯沉积物中的Mn、Cr、Cu、Fe、Ni、Pb和Zn等7种重金属元素的化学形态进行了分析。结果表明：Cr、Cu、Fe、Ni、Pb、zn元素以残渣态为主,Mn元素以可交换态及碳酸盐结合态为主。Cr、Cu、Ni、Pb的有机物及硫化物结合态、Fe—Mn氧化物结合态含量较高,Zn的有机物及硫化物含量较高。其中,Mn、Cr、Ni和Pb对环境产生危害的可能性最大,对这几元素应该予以足够的关注。     

东北地区城市污水处理厂污泥中重金属的形态分布及其潜在生态风险评价

分析了东北地区7个城市污水处理厂脱水污泥中Cu、Zn、Cr、Ni、Mn的含量,利用修正的BCR法研究了污泥中重金属的形态分布特征,并使用地累积指数(Igeo)法和内梅罗指数法(PI)评估了污泥在土地利用过程中重金属的潜在生态风险.结果表明,污水厂污泥中Zn含量超过了国家标准(GB4284—1984)限值,且污泥中Cu、Zn和Mn的含量远远超过东北耕地黑土中的背景含量.污泥中Cu和Cr的有机物结合态(即可氧化态)所占比例较大,可迁移形态含量最高的重金属是Zn,Ni广泛分布于可交换态、酸溶态、可还原态、可氧化态和残渣态中,Mn的残渣态在5种形态中所占比例最高.5种金属中迁移性最强的是Zn,其次为Mn,Cr的迁移性最差.内梅罗单项污染指数法和地累积指数法的评价结果表明,Cu、Zn和Mn是污泥土地利用过程中潜在的污染元素.内梅罗综合指数法的评价结果显示,种脱水污泥均对耕地黑土环境存在严重的潜7在生态风险.     

The relationship between epilithic periphyton (biofilm) bound metals and metals bound to sediments in freshwater systems

Surficial sediments and epilithic periphyton (biofilm) were sampled from six sites on the River Churnet and five sites on the River Manifold in Staffordshire and analysed for cadmium (Cd), copper (Cu), lead (Pb) and zinc (Zn). The sites demonstrated a wide range of sediment trace metal concentrations determined by inductively coupled plasma optical emission spectrometry (ICP-OES) and atomic absorbtion spectroscopy (AAS). Biofilm was removed from the substrate using physical abrasion and 0.005 M ethylenediaminoethanetetra-acetic acid (EDTA) extractant. The European Standards, Measurements and Testing Programmes (BCR) operationally defined geochemical speciation scheme was used to determine the exchangeable, acid soluble fraction of the sediments. Significant positive correlations were determined between the EDTA extractable biofilm and the exchangeable sediment fraction for Cd, Cu and Zn but not for Pb. Natural epilithic periphyton may be a potential metal biomonitor particularly of Cu, Cd and Zn in aquatic systems and provide supporting information in relation to potential sediment toxicity.     

白洋淀表层沉积物重金属形态分布特征及生态风险评价

为了研究白洋淀全域表层沉积物重金属污染程度,采用BCR 3步提取法分析了沉积物中6种重金属（Cd、Cr、Cu、Ni、Pb和Zn）的含量及其赋存形态,讨论了6种重金属的生物可利用性大小,并运用次生相与原生相比值法（RSP）、潜在生态风险指数法（RI）和聚类分析进行了生态风险评价及重金属污染来源探讨.研究表明,白洋淀表层沉积物中重金属Cd和Cu含量均值分别达到背景值的2.9倍和1.3倍.Cd的可交换态及碳酸盐结合态和铁锰氧化物结合态的质量分数达到51.20%,生物可利用性较大;Pb主要赋存于铁锰氧化物结合态;Cr、Cu、Ni和Zn以残渣态为主要的存在形式.白洋淀的首要污染因子是Cd,整体面临较高Cd风险.圈头片风险最高,端村片风险最低;南刘庄片区域内风险相差较大,其中N4为白洋淀全域最高风险点.源解析结果显示,Cd、Cu、Pb和Ni受人类活动因素较多,Cr和Zn则更多的受到自然因素影响.     

北京某污水处理厂污泥重金属污染特征、潜在生态风险及健康风险评价

连续采集了北京市某污水处理厂污泥,样品经过微波消解后利用ICP-OES测定重金属含量,同时,利用BCR连续提取分析方法分析了污泥中重金属赋存形态.在分析测定污泥中Pb、Zn、Cd、Cr、As、Ni、Cu 7种重金属含量及形态的基础上,开展了污泥重金属污染水平评价、潜在生态风险评价及健康风险评价.结果表明,污泥中重金属含量最高的是Zn,含量为930.08 mg·kg-1,残渣态及可提取态所占比例最高的元素分别是Pb和Ni,所占比例分别为80.86%及18.84%;污泥重金属综合污染指数为4.84,属重度污染;污泥重金属潜在环境综合风险指数为237.60,属极高生态风险.基于健康风险评价模型建立两条暴露途径,分别对儿童及成人进行健康风险评价,得出儿童非致癌指数及致癌指数分别为2.02×10-1和1.44×10-4,而成人非致癌指数及致癌指数分别为7.21×10-2和5.13×10-5.     

Leaching Characteristics of Heavy Metals and As from Two Urban Roadside Soils

The leaching tests, including the Toxicity Characteristic Leaching Procedure (TCLP), EDTA extraction and BCR sequential extractions before and after EDTA treatments, were performed on two specific soils to elucidate heavy metal-associated mineral fractions and general leachability. The TCLP illustrated the low leachability of heavy metals in soils from two sites. EDTA is a strong chelator and therefore had higher extraction efficiency compared to that of TCLP. The lower extraction percentages by EDTA for As and Sb were found compared to the other heavy metals derived from anthropogenic sources. Sequential extractions showed that the importance of acid-extractable, organically-bound and Fe–Mn oxide fractions was identified for anthropogenic heavy metals with the exception of As and Ni while the importance of residual fraction was identified for endogenous metals. Changes in sequential fractions of heavy metals after leaching with EDTA are very complex and it is difficult to generalize on which fraction was more mobile than the others. These combined results are helpful in elucidating the association of heavy metals to soil fractions and the mobility characteristics of heavy metals under certain environmental conditions.     

低分子有机酸对土壤中Cu化学形态的影响

向石英砂岩坡积物发育的红壤中添加系列浓度CuSO4模拟土壤Cu污染,然后加入不同浓度的低分子量有机酸培养,采用改进的BCR连续提取法评价低分子有机酸对重金属Cu形态的影响.结果表明,对不同程度的Cu污染(Cu 0～400mg·kg-1)土壤,随着有机酸添加浓度的升高,最具活性的弱酸溶解态Cu含量均有不同程度的提高,土壤重金属Cu得到活化;Cu活化效果随柠檬酸浓度升高而升高,随酒石酸和草酸浓度升高呈先上升后基本不变趋势;整体活化效果是柠檬酸>酒石酸≈草酸.可还原态Cu随着有机酸浓度的增加而减少,其中添加柠檬酸的处理减少最明显.当有机酸浓度为10 mmol·kg-1、20 mmol·kg-1时,酒石酸和草酸、柠檬酸活化Cu效果分别达到最优.     

外源添加磷和有机酸模拟铅污染土壤钝化效果及产物的稳定性研究

有机酸可提高土壤磷有效性,且能影响对重金属的固定,其在磷活化和重金属钝化方面具有非常复杂的功能.本研究以模拟铅污染土壤为对象,外源添加磷和柠檬酸,采用BCR三步连续提取法、0.01 mol·L-1CaCl2提取和毒性淋溶提取法(TCLP)评价有机酸存在下磷对模拟铅污染土壤的钝化效果;以苹果酸、NaNO3溶液为解吸剂探讨磷-柠檬酸-铅体系的稳定性.结果表明,无柠檬酸时,酸提取态Pb含量随磷浓度的增加而降低;加磷100 mg·kg-1、400 mg·kg-1时,酸提取态Pb含量随柠檬酸浓度增加而显著增加.残渣态Pb与酸提取态Pb的变化趋势相反,说明磷能降低土壤铅的生物有效性,柠檬酸则作用相反.有机酸浓度一定时,随磷浓度增加,0.01 mol·L-1CaCl2提取和TCLP提取的铅含量均呈降低趋势,表明磷具有钝化铅污染土壤的效果;但磷浓度一定时,它们提取铅含量随柠檬酸浓度增加表现出相反的变化趋势.土壤铅的解吸率随苹果酸浓度增加、pH值减小、离子强度增加而提高,且只添加磷处理的土壤铅解吸量较添加磷和柠檬酸共同处理的土壤少,前者钝化的铅稳定性更高.     

基于地球化学特性的海州湾海洋牧场沉积物重金属研究

海洋牧场是一种新的可持续的生产方式,对中国海洋经济的转型具有重要作用.本文根据海底构筑物的密集程度与投放时间把海州湾海洋牧场划分为3个区(外侧区、内测区、中心区),对表层沉积物的温度(T)、酸碱度(p H)、氧化还原电位(Eh)、表面积平均粒径(D[3,2])、总有机碳(TOC)这5种地球化学指标进行原位调查,采用改进的BCR方法对重金属Cr、Cu、Ni、Zn、Pb、Cd进行连续提取.结果表明,沉积物Eh的横向分布受到了海底构筑物的影响,TOC在11.7~13.5 g·kg-1之间,与p H呈显著负相关;Cu、Zn、Ni、Cr以原生相为主要赋存形态,Pb、Cd以次生相的铁锰氧化物结合态(F2)为主要赋存形态,并受Eh控制;相关性及聚类分析表明,Cr、Cu、Ni、Zn为天然源,Cd、Pb存在明显的人为来源;Cr、Ni、Cu、Zn、Pb、Cd的可交换及碳酸盐结合态(F1)与TOC显著相关,Cr、Ni、Cu、Zn、Pb、Cd铁锰氧化物结合态(F2)、Cr、Ni、Cu、Zn的残渣态(F4)都与沉积物粒度显著相关,不同形态的Cd受多环境因子控制;海洋牧场中心区和外侧区沉积物中重金属总量、次生相含量均较内侧区和对照区要低.由于海底构筑物和水动力学的差异性,海洋牧场内侧区细颗粒与有机质对沉积物重金属Cr、Ni、Cu、Zn次生相的富集、吸附作用要大于颗粒再悬浮的释放作用,而在中心区、外侧区细颗粒和有机质影响较小;沉积物富集系数显示Cd出现了富集现象.