改性明矾浆对土壤中镉、铅可提取性的影响研究

为探讨不同改性明矾浆能否作为修复中、低度Cd和Pb污染土壤的重金属钝化剂,采用土培实验研究了不同改性明矾浆和系列添加浓度对污染土壤中可提取态Cd和Pb含量的影响。结果表明:土壤中可提取态Cd和Pb的含量随明矾浆添加量的增大和钝化时间的延长而降低,其中同等钝化剂添加量条件下,热碱改性明矾浆钝化土壤中Cd和Pb的能力优于其他三种明矾浆,如添加浓度为5.0%,放置时间为16周的热碱改性明矾浆处理,其可提取态Cd和Pb含量分别为1.04、19.87 mg·kg-1,与对照相比(可提取态Cd和Pb含量分别为2.12、50.8 mg·kg-1),降幅分别为51%和60.9%,均达到显著水平(P0.05)。扫描电镜和比表面积测试结果证实,原明矾浆经过热碱改性后其粒径变小,比表面积增大,增加了明矾浆与污染物的接触面积,使其与重金属的吸附固定能力有所提高,可以有效降低土壤中重金属Cd和Pb的可提取态含量,从而降低其生物有效性。     

土壤的老化对PCB138的可提取性和生物可利用性的影响

为探讨老化行为对多氯联苯(Polychlorinated biphenyls,PCBs)在土壤中的可提取性和生物可利用性的影响,选取2,2′,3,4,4′,5-六氯联苯(PCB138)作为目标污染物,进行90 d的老化试验,比较了超纯水提取、正丁醇溶液提取、超声提取(正己烷/丙酮)和索氏抽提(正己烷/二氯甲烷)等4种方法对土壤中不同老化时间PCB138的提取率;以赤子爱胜蚓(Eisenia fetida)为土壤模式参照生物,在不同的老化时间里测定蚯蚓体内PCB138的含量与脂肪含量。结果表明,4种方法提取PCB138的能力依次为索氏抽提(正己烷/二氯甲烷)≈超声提取(正己烷/丙酮)正丁醇提取超纯水溶液提取;索氏抽提、超声提取和正丁醇溶液提取的提取率从最初的87%~93%、85%~90%、50%~60%分别下降到70%~76%、65%~73%、25%~45%,在30~45 d时总提取量保持稳定,而超纯水提取PCB138的量有限,显示出最低的提取能力且为非重复性结果。PCB138在蚯蚓体内富集量随接触时间增加而增加,在老化30 d左右其体内PCB138富集量最大;在老化30~60 d时,蚯蚓体内的PCB138的含量逐渐下降,健康状况良好的蚯蚓脂肪含量有所下降但不明显。正丁醇溶液提取、超声提取和索氏抽提对PCB138的提取率,以及老化土壤中蚯蚓对PCB138的富集量,均说明PCB138在土壤中的生物有效性随着老化时间的延长而降低。     

土壤中镉铅锌单一和复合老化效应的研究

重金属的形态随时间变化,即老化效应,对评价重金属污染有着重要意义.本实验采用实验室模拟方式人为加入不同浓度的镉铅锌盐溶液,于污染后的第3、7、15、30、90、180、360 d采样,用0.01 mol·L-1CaCl2提取可利用态.单一老化效应的结果表明:Cd、Pb、Zn的有效态浓度在开始的7 d内迅速减小,7～30 d内缓慢减小,而30 d以后浓度趋于稳定,达到动态平衡.Pb的有效态减少相对最为显著.在Zn或Pb存在的条件下,重金属的交互作用产生的复合老化效应表现为Cd的稳态浓度显著高于单一老化效应,并且达到稳态的时间延长.Pb比Zn对有效态Cd含量的增加有着更为显著的影响.     

热处理对土壤中多环芳烃的影响

[目的]为了对多环芳烃在土壤中的行为进行研究。[方法]利用一种温度辅助解吸-气流式液相微萃取装置结合溶剂超声萃取,研究了热处理(温度为50~300℃)对土壤中多环芳烃(苊、菲、芘、苯并[a]芘)存留的影响。[结果]在该温度范围内进行热处理时只有极少部分的多环芳烃从土壤中释放出来,大部分被保留于土壤中;200℃以上的处理温度明显降低了土壤中多环芳烃的溶剂可提取性,对多环芳烃起锁定作用。[结论]该研究可以为受多环芳烃污染的土壤修复和生物有效性提供指导。     

土壤环境质量研究回顾与讨论

土壤环境质量的研究和应用是环境科学和环境土壤学的重要命题。本文简要回顾了与土壤环境质量密切相关的土壤质量的概念与质疑,给出了土壤环境质量的参考定义,强调了这些概念和定义仍处于发展之中。土壤环境质量是指在一定的时间和空间范围内,土壤自身性状对其持续利用以及对其他环境要素,特别是对人类或其他生物的生存、繁衍以及社会经济发展的适宜性。土壤环境质量是土壤环境“优劣”的一种概念,是特定需要之“环境条件”的量度,它与土壤的健康或清洁的状态,以及遭受污染的程度密切相关。本文重点讨论了土壤环境质量研究中需要考虑的问题、主要研究内容、土壤环境质量应用中的突出问题,包括标准的制订和土壤“可提取态”和植物有效性关系的研究。     

A scheme for soil classification of paddy fields in Japan with special reference to mineral paddy soils

Introduction

Paddy (irrigated) rice is the most important single crop in Japan. Nearly half of the total arable lands covering approximately 6.5 million hectares, are devoted to the growing of the rice plant. It is grown mainly on the alluvial plains which are intensively cultivated, and are the most productive soils of the country. Since the idea of modern pedology was introduced into Japan, some work has been done by some Japanese investigators to classify paddy soils on the basis of their morphological characteristics. A brief historical review on the soil survey work in Japan has been given by Kamoshita⁸⁾. In 1936 Kawamura described methods of soil survey in Korea through a careful study of the work developed by Stremme and his colleagues in Danzig. In those days Kamoshita⁹⁾,¹⁰⁾ devised a scheme of paddy soil classification by applying the concept of the wet soil types (mineralische Nassböden) proposed by Stremme, and he established five predominant soil types as follows: Bog soils (Moorböden), Half-bog soils (anmoorige Böden), Meadow soils (Wiesenböden), Gray lowland soils (graue Auenböden), and Brown lowland soils (braune Auenböden). The names in parentheses represent the wet soil types proposed by Stremme. These soil types are subdivided into soil kinds (Bodenarten) on the basis of differences in texture, rusty mottling, and humus content. The soil kinds were used as both categorical and cartographical units for detailed soil surveys.     

Testing mechanisms underlying the Hedley sequential phosphorus extraction of soils

The Hedley fractionation has become the preeminent measure for estimating the bioavailability of phosphorus (P) in soils. However, mechanisms underlying P extractability have never been tested. We hypothesize that P sequentially extracted by individual steps can either be referred to a specific mineral source (Hypothesis 1) or to its binding strength to minerals (Hypothesis 2). We prepared mineral‐P associations in the laboratory using various secondary mineral phases and P forms (orthophosphate, phytic acid, ribonucleic acid), which were then subject to the Hedley sequential extraction scheme (anion exchange resin in form, 0.5 M NaHCO₃, 0.1 M NaOH, 1 M HCl, and concentrated HCl at 80°C). Extracts were analyzed for P as well as for the main mineral‐borne elements by inductively coupled plasma–optical emission spectroscopy (ICP–OES). In order to test if the observed mineral dissolution patterns match those of natural soils, we applied the Hedley fractionation to forest soils comprising various P stocks and measured in addition to extracted P also iron, aluminum, and calcium by ICP – OES. Phosphorus extractability from mineral‐P associations differed between P forms and mineral phases. Adsorbed P always contributed to several or all extracts, Hypothesis 1 was thus not tenable. Aluminum hydroxide, allophane, ferrihydrite, and goethite completely dissolved during Hedley fractionation from the third extraction step onwards. Successive mineral dissolution also occurred for the soil samples. Thus, extracted P represents partly desorbed P from various soil constituents and partly P co‐released upon dissolution of various minerals. Consequently, also Hypothesis 2 could not be confirmed, i.e., the sequential extraction is not suitable to assess different binding strengths between P forms and minerals. We conclude that the method hardly provides information for studies aiming at the mechanistic understanding of P bioavailability in soil.     

Behaviour and assessment of bioavailability of organic contaminants in soil: relevance for risk assessment and remediation

Abstract. Soils contaminated with organic chemicals are now widespread in industrialized and developing countries, and the risk assessment and remediation of such contaminated sites is a priority. However, containment and remediation strategies are complicated in many cases by the range of contaminants present and the historical nature of the contamination. Research has increased our understanding of the behaviour of organic contaminants in soil and the factors that control their behaviour. There is a fundamental need to understand and, where possible, quantify the bioavailable fraction as well as the total concentration of contaminant present in soil: the bioavailable fraction is key to toxicity or biodegradation. To quantify these fractions, a large number of techniques have been employed, ranging from organic and aqueous based solvent extractions to the use of biota. Many studies have been carried out investigating the use of chemical techniques to describe bioavailability, which could be used in the assessment and remediation of contaminated land. The aim of this review is to consider the behaviour of organic contaminants in soil, highlighting issues of bioavailability, and then to discuss the relevance of the various methods for assessing risk and potential remediation of organic contaminants in soil.     

有机化合物和硝酸溶液对复合污染土壤中Cu、Zn、Pb释放的影响

研究了等浓度的不同有机酸、有机盐、人工螯合剂和不同浓度HNO3 溶液对复合污染土壤中Cu、Zn、Pb的浸提性及其潜在释放性。结果表明 :四种有机酸对铜的释放顺序为 :柠檬酸 >草酸 >酒石酸 >苹果酸 ,对锌的释放顺序为 :柠檬酸 >苹果酸 >草酸 >酒石酸 ,对铅的释放顺序为 :柠檬酸 >酒石酸 >苹果酸 >草酸 ;有机盐对这些金属的释放顺序较为一致 :EDTA >柠檬酸钠 >草酸钠 >酒石酸钾钠 (铅为酒石酸钾钠 >草酸钠 )。对这三种金属来说 ,铜是最易释放的元素 ,锌次之 ,铅最差。从释放特征来看 ,各种有机化合物对不同的金属表现不尽相同 ,人工螯合剂EDTA、柠檬酸钠、有机酸对铜 ,EDTA、酒石酸钾钠对铅 ,1molL-1HNO3 和0 .1molL-1HNO3 对铜、锌、铅等的释放速率较快 ;草酸钠对铜、锌 ,草酸对铅 ,0 .0 1molL-1HNO3 对铜、锌、铅等的释放速率较慢 ,其它释放剂的释放速率介于两者之间