微生物降解DDT研究进展

DDT是<关于持久性有机污染物(POPs)的斯德哥尔摩公约>规定的12种禁限POPs之一.它的环境毒性越来越引起人们的关注.微生物降解是一种有效的环境友好型去除DDT污染的手段.本文简要综述了国内外在DDT微生物降解方面的研究进展,主要包括降解DDT的微生物、微生物降解DDT的途径以及以影响土壤中微生物降解DDT的因素.并对通过生物强化手段消除土壤中的DDT污染进行了展望.     

湿地开发过程的哲学思考

本文在对湿地的发展现状进行剖析时,引发了对人与自然问关系的思考。历史上人类与自然的关系曾一度进入了“人类中心主义”的泥潭,并最终导致自然界对人类的疯狂报复。人类只有正确地认识自然、尊重自然,科学地开发和利用自然,按照自然规律办事,对大自然始终怀有谦逊的态度,才能真正实现人与自然的和谐发展。     

花生对DDT的吸收积累

采用盆栽试验,通过向土壤中添加DDT设置3个浓度处理(T1,295 ng g-1;T2,3723 ng g-1;T3,6109 ng g-1)和1个对照(CK,31 ng g-1),研究花生(Arachis hypogaea)对DDT的吸收积累。花生果实成熟后将植株分成根、茎、果壳和果仁四部分,GC-ECD测定各部位中的DDT浓度。结果表明,在T2和T3处理中,花生果仁中的DDT含量高达200 ng g-1左右,超过100 ng g-1的WHO/FAO最大残留限量标准。虽然在CK和T1中,花生的果仁没有超标,但是,果壳和茎中,特别是根中DDT的高浓度值得关注。根部的总量最大,果仁中的总量最小,根部是DDT吸收积累的最主要部位。花生根部和茎部较高的生物蓄积系数暗示着花生对DDT具有较强的吸收积累能力。此外,研究显示花生果仁中高的含油量可能有助于亲脂性DDT的吸收积累。     

有机氯农药残留对农产品质量的影响分析

对不同农产品中有机氯农药（“六六六”、“DDT”）残留进行了监测与分析评价，简述了有机氯农药有害物在农业环境和农产品中残留现状，并提出相应的防治对策，为合理施用农药，提高农产品质量和安全性提供参考依据。     

杂交苏丹草(Sorghum bicolor×S.sudanense)修复DDT污染土壤效果研究

采用盆栽试验,研究了杂交苏丹草吸收和富集DDT的规律及其对DDT污染土壤的修复效果。结果表明:①土壤中添加高浓度的DDT,对杂交苏丹草的生物量没有显著影响,说明杂交苏丹草对DDT有耐受能力;②杂交苏丹草对DDT及其主要降解产物都有吸收,在旺盛生长期,植株中DDT的累积速率也较快;③杂交苏丹草根系中DDT及其主要降解产物的浓度是茎叶中相应组分浓度的4.81~10.32倍,质量比在0.57~1.55倍之间;④杂交苏丹草从土壤中吸收DDT占添加量的11.3%,而在其生长期间,土壤中DDT消失量为56.0%。     

AQDS加速红壤性水稻土中DDT厌氧脱氯效应研究

电子供体基质和电子穿梭体对电子转移过程有重要影响,进而可能影响厌氧反应体系中2,2-双(4-氯苯基)-1,1,1-三氯乙烷(DDT)还原脱氯降解。为了阐明电子供体基质正丁酸与电子穿梭体蒽醌-2,6-二磺酸盐(AQDS)对红壤性水稻土中DDT还原脱氯效果的影响,本研究采用厌氧土壤培养试验并设定以下5个处理:1灭菌对照,2对照,3正丁酸,4AQDS,5正丁酸+AQDS。结果表明,厌氧培养20 d后,土壤中DDT可提取态残留量减少了85.2%~96.3%。DDT厌氧脱氯降解的主要产物为2,2-双(4-氯苯基)-1,1-二氯乙烷DDD。添加正丁酸在培养前8d显著提高产CH4速率,而对DDT脱氯降解无显著促进作用,第8天之后,随着产CH4速率降低,添加正丁酸处理的DDT脱氯速率逐渐升高。添加AQDS显著增强土壤还原性并加速三价铁氧化物还原生成电子供体二价铁,进而显著促进DDT还原脱氯降解。同时添加正丁酸和AQDS对促进DDT还原脱氯的效果最佳,但是正丁酸和AQDS对加速DDT还原脱氯无显著交互作用。本研究结果对于制定DDT污染土壤的高效原位修复技术方案具有指导意义。     

漫话农业工程(连载) 二、农业机具的演化

农业生产与农民生活需要各种机械,对其进行研究设计以及搞好运用、管理、销售服务等是一门重要的学问.我国己将这一学科惯称为“农业机械化”,它是农业工的一个主要分支.世界上.不论东方西方,对农业机的研究、制造均有数于年的历史。从人类开始使用简易工具进行考还,我国早在四、五十万年     

~(14)C-丁草胺、~(14)C-毒死蜱和~(14)C-DDT在日本林蛙中的生物学行为(英文)

用同位素示踪技术研究了14 C 丁草胺、14 C 毒死蜱和14 C DDT在日本林蛙 (RanajaponicajaponicaGuenther)中的生物学行为。结果发现 ,14 C 丁草胺、14 C 毒死蜱和14 C DDT在 2 4h后分布到青蛙的各个器官组织 ,并分别以胆囊、小肠、小肠为它们的特异性浓集器官。与胆囊或小肠的14 C放射性活度比较 ,其它器官组织中的要小得多。14C DDT在日本林蛙中较难降解 ,2 4h后DDT母体在肝和脂肪组织中占DDT代谢物的54 6%和 88 4%。青蛙中的14 C 丁草胺、14 C 毒死蜱和14 C DDT可被丙酮提取 ,但三者之间以及在青蛙的器官之间有差异     

正丙醇与羟丙基-β-环糊精复配对高浓度DDT污染土壤的增效洗脱修复研究

以武汉某高浓度滴滴涕(DDT)污染场地土壤为研究对象,采用正丙醇和羟丙基-β-环糊精(HPCD)为洗脱剂进行相关的洗脱试验,并嵌合升温措施,研究了其对DDT污染场地土壤的洗脱修复效果。试验结果表明,20%正丙醇和50 g L-1HPCD复配、50℃水浴连续洗脱5次,可以使土壤中DDT总量的平均去除率达到96.41%。研究为DDT污染场地土壤的异位增效洗脱技术研发提供了一种有效手段。     

珠江三角洲地区典型类型土壤中DDT残留及其潜在风险

珠江三角洲地区有机氯农药的残留一直以来受到关注。本研究通过对该地区30个采自典型类型土壤剖面的表层样品进行DDT的含量和组成分析,初步揭示了珠江三角洲地区的DDT残留情况及其潜在生态风险。研究结果表明:珠江三角洲地区6种典型类型土壤中,除滨海砂土外,其他5种土壤都能够检测到DDT的存在。DDT含量在0.16~32.8μg/kg之间,以o,p′-DDT的检出率最高,其次为p,p′-DDE。该地区可能存在通过使用三氯杀螨醇带入微量DDT的情况。此外,个别采样点存在低剂量DDT的潜在生态风险,需要做进一步探讨。     

Using Low-Cost Iron Byproducts from Automotive Manufacturing to Remediate DDT

Water, soil and sediment contaminated with DDT poses a threat to the environment and human health. Previous studies have shown that zerovalent iron (ZVI) can effectively remediate water contaminated with pesticides like DDT, metolachlor, alachlor. Because the type of iron can significantly influence the efficiency and expense of ZVI technology, finding a cheaper and easily available iron source is one way of making this technology more affordable for field application. This study determined the effects of iron source, solution pH, and presence of Fe or Al salts on the destruction of DDT. Batch experiments demonstrated successful removal of DDT (>95% in 30 d) in aqueous solutions by three different iron sources with the following order of removal rates: untreated iron byproduct (1.524 d^?1) > commercial ZVI (0.277 d^?1) > surface-cleaned iron byproduct (0.157 d^?1). DDT removal rate was greatest with the untreated iron byproduct because of its high carbon content resulted in high DDT adsorption. DDT destruction rate by surface-cleaned iron byproduct increased as the pH decreased from 9 to 3. Lowering solution pH removes Fe (III) passivating layers from the ZVI and makes it free for reductive transformations. By treating DDT aqueous solutions with surface-cleaned iron byproduct, the destruction kinetics of DDT were enhanced when Fe(II), Fe(III) or Al(III) salts were added, with the following order of destruction kinetics: Al(III) sulfate > Fe(III) sulfate > Fe(II) sulfate. Cost analysis showed that the cost for one kg of surface-cleaned iron byproduct was $12.33, which is less expensive than the commercial ZVI. Therefore, using surface-cleaned iron byproduct may be a viable alternative for remediating DDT-contaminated environments.     

The interaction of ddt with suspended particles in sea water

The equilibrium distribution of DDT between the liquid and solid phases in the sea water medium was investigated by means of the radiotracer technique. The investigation of the influence of DDT concentration on its adsorption on several solid phases is presented and results are given as adsorption isotherms. Desorption experiments indicate that these processes are reversible. Extension of desorption is higher from quartz than from limestone, while it is significantly lower than from marine sediments. Examination of the equilibrium distribution of DDT between sea water and the examined surfaces suggested that DDT in the investigated systems exists as a colloid dispersion. The results are also discussed from the point of view of marine pollution. Suggestions for the future work in this field are also given.     

蔬菜不同部位对DDTs的富集与分配作用

在可控条件下研究了人为污染土壤中DDT类污染物在蔬菜（菠菜和胡萝卜）不同部位的富集与分配规律。结果表明,DDT类污染物在菠菜和胡萝卜叶部和根部均有一定富集,其中菠菜叶面富集量占富集总量的68.6%～92.2%之间;而胡萝卜叶部富集占富集总量的34.9%～41.6%之间。不同DDTs在菠菜和胡萝卜体内的生物富集量呈：p,p＇-DDE〉p,p＇-DDT〉p,p＇-DDD〉o,p＇-DDE〉o,p＇-DDT的规律。DDTs通过不同途径在菠菜和胡萝卜内的生物富集系数表现如下规律：BCF大气－菠菜〉BCF大气－胡萝卜〉BCF土壤－胡萝卜〉BCF土壤－菠菜。不同DDTs在蔬菜体内的生物富集系数表现为：BCFp,p＇-DDE〉BCFo,p＇-DDE〉BCFp,p＇-DDD〉BCFp,p＇-DDT〉BCFo,p＇-DDT。由于DDTs在蔬菜体内富集后,可沿食物链传递和放大,对农产品质量和人体健康构成直接威胁。     

Ecological Risk Assessment for the Recent Case of DDT Pollution in Lake Maggiore (Northern Italy)

Contamination by DDT of industrial origin was detected in 1996 in Lake Maggiore (Northern Italy) causing concern for wildlife and human health. Starting from 1998 a monitoring programme involving different research laboratories was undertaken to establish the pollution level of the lake. In assessing the ecological risk to Lake Maggiore wildlife during this period, the present study integrates information provided by the Commission for the Protection of Italian and Swiss Waters with further analysis and ecotoxicological tests carried out on some autochthonous target species for this insecticide. Sediments collected at the end of 1997 in the most contaminated bay (total DDT 860.2 ng g^?1 dry weight) caused a decrease in fertility and growth of benthic oligochaetes and chironomids, while the 48 h IC₅₀ for Daphnia galeata (0.76 μg L^?1, c.i. 0.43–1.34) was much higher than the DDT concentration in the lake water. The risk of acute effects on zooplankton should therefore be excluded, while transfer through the trophic web and bioconcentration in fish and fish-eating birds are the most adverse consequences of DDT contamination in Lake Maggiore.     

Co-remediation of DDT-contaminated soil using white rot fungi and laccase extract from white rot fungi

Purpose

2,2-Bis(p-chlorophenyl)-1,1,1-trichloroethane (DDT), one of the most widely used organochlorine pesticides in soil, was banned in the 1970s for agricultural use because of its detrimental impacts on wildlife and harmful effects on human health via the food chain. However, high levels of DDT are frequently detected in agricultural soils in China. Considering this situation, this study investigated the use of white rot fungi and laccase derived from white rot fungi to co-remediate DDT-contaminated soil.

Materials and methods

A culture of white rot fungi was used to inoculate soil samples and also to extract laccase from. Soil was contaminated with four components of DDT (p,p′-DDE, o,p′-DDT, p,p′-DDD, and p,p′-DDT). Individual DDT components and the sum of the DDT components (p,p′-DDE, o,p′-DDT, p,p′-DDD, and p,p′-DDT—collectively referred to as DDTs) were both analyzed by GC at various stages during the incubation period. The efficacy of co-remediating DDT-contaminated soil using white rot fungi and laccase was tested by investigating how degradation varied with varying amounts of white rot fungi, sterilizing soil, temperature, soil pH, concentrations of DDT, and concentration of the heavy metal ion Cd²⁺.

Results and discussion

“”It was concluded that the reduction of DDTs in soil using white rot fungi and laccase was higher than reduction using only white rot fungi or laccase by nearly 14 and 16 %, respectively. Five milliliters fungi per 15 g soil and 6 U laccase per gram soil were the optimal application rates for remediation, as shown by a reduction in DDTs of 66.82 %. The difference in the reduction of individual DDT components and DDTs between natural and sterilized soils was insignificant. The optimal temperature and pH in the study were 28 °C and 4.5, respectively. In addition, reduction of individual DDT components and DDTs increased with increasing concentrations of DDT and decreased with increasing concentrations of Cd²⁺.

Conclusions

Compared with the remediation of DDT using only white rot fungi or laccase, the co-remediation of DDT using white rot fungi and laccase degraded DDT in soil more rapidly and efficiently; the highest reduction of DDTs was 66.82 %.     

Historical distribution of DDT residues in pond sediments in an intensive agricultural watershed in the Yangtze-Huaihe region,China

Purpose

The extensive use of chemical pesticides on farmlands during the last several decades in China has led to a rapid deterioration of environmental water quality in recent years. The aims of this study were to: reconstruct the history of pesticide residues, determine the input load and residual load of dichlorodiphenyltrichloroethane (DDT) pesticides, and assess the risk of pesticide residues to aquatic ecosystem and human health.

Materials and methods

Caesium-137 was used to date sediment cores collected from ponds representing four land use types of an agricultural watershed with high-yield grain production and characterized by multipond systems in the Yangtze-Huaihe region of China. These ponds were selected to establish the historic pattern of DDT pesticide residues.

Results and discussion

(1) The mean total concentration of DDT residues including p,?p?′-dichlorodiphenyldichloroethylene (p,p′-DDE), p,?p?′-dichlorodiphenyldichloroethane ( p,p′-DDD), o,p′-DDT, and p,p′-DDT in sediment in the watershed was 82 μg kg^?1, ranging from under the detection limit to 457 μg kg^?1, which was mostly contributed by p,?p′-DDE (57 μg kg^?1 on average). Spatially, total concentrations of DDT residues in farmland pond sediment were the highest, reaching as high as 457 μg kg^?1. Temporally, an inflection point appeared in the 1970s, prior to which DDT contents increased with time, after which concentrations showed a decreasing trend. (2) In total, 323 kg DDT pesticide was applied to the Liuchahe Watershed since 1955. The total retention of four DDT residues in the multipond system was 14 kg (～4 % of the input), and most DDT pesticide was degraded to p,?p?′-DDE. (3) More than 80 % of sediment DDT residues exceeded their interim freshwater sediment quality guidelines, and the percentages of DDT,DDD, and DDE residues exceeding probable effect limit (PEL) values were 57, 29, and 70 %, respectively, which indicated a moderate to high ecological risk of DDT in this watershed.

Conclusions

Our results clearly reveal that the extensive use of pesticides has resulted in significant pesticide residual pollution in this watershed, which could severely deteriorate water quality and threaten aquatic ecosystem and human health in the watershed and, thus, remain a cause for concern.     

DDT Resistance and Transformation by Different Microbial Strains Isolated from DDT-Contaminated Soils and Compost Materials

Bioremediation is a potential option to treat 1, 1, 1-trichloro-2, 2-bis (4-chlorophenyl) ethane (DDT) contaminated sites. In areas where suitable microbes are not present, the use of DDT resistant microbial inoculants may be necessary. It is vital that such inoculants do not produce recalcitrant breakdown products e.g. 1, 1-dichloro-2, 2-bis (4-chlorophenyl) ethylene (DDE). Therefore, this work aimed to screen DDT-contaminated soil and compost materials for the presence of DDT-resistant microbes for use as potential inoculants. Four compost amended soils, contaminated with different concentrations of DDT, were used to isolate DDT-resistant microbes in media containing 150 mg l^?1 DDT at three temperatures (25, 37 and 55°C). In all soils, bacteria were more sensitive to DDT than actinomycetes and fungi. Bacteria isolated at 55°C from any source were the most DDT sensitive. However DDT-resistant bacterial strains showed more promise in degrading DDT than isolated fungal strains, as 1, 1-dichloro 2, 2-bis (4-chlorophenyl) ethane (DDD) was a major bacterial transformation product, while fungi tended to produce more DDE. Further studies on selected bacterial isolates found that the most promising bacterial strain (Bacillus sp. BHD-4) could remove 51% of DDT from liquid culture after 7 days growth. Of the amount transformed, 6% was found as DDD and 3% as DDE suggesting that further transformation of DDT and its metabolites occurred.     

Levels of pesticide residues in Egyptian human milk samples and infant dietary intake

Contamination of human milk with residues of organochlorine pesticides and polychlorinated biphenyls was studied in a series of investigations concerned with the monitoring of these chemicals in Egyptian food. The DDT complex was the most frequently found pesticide, followed by total hexachlorocyclohexane isomers. Heptachlor and its epoxide, dieldrin, hexachlorobenzene, and oxychlordane were also found but less frequently. Estimated dietary intakes (EDIs) of these contaminants by the breast-fed infants were compared to acceptable daily intakes (ADIs). EDIs of DDT complex, lindane (gamma-HCH), heptachlor + heptachlor epoxide, and oxychlordane were below ADIs. Dieldrin EDI exceeded the acceptable daily intake.     

DDT in Biota of Paranagu�� Bay, Southern Brazil: Recent Input and Rapid Degradation

The presence of recent dichlorodiphenyltrichloroethane (DDT) inputs is established for Paranaguá Bay biota, i.e. bivalves, fish and one sponge. Values ranged from 6.9 to 156.2 ng ??DDT/g dry weight. Three fish species analysed showed ??DDT values from 36.8 to 92.1 ng/g dry weight. The highest contents (up to 156.2 ng ??DDT/g dry weight) were found for mangrove oysters (Crassostrea rhizophorae) at locations affected by sewage discharge from Paranaguá City. Turtles as herbivores were not affected by this input with values of 0.7 and 2.2 ng ??DDT/g dry weight. The areal distribution of samples suggests that usage of DDT is widespread around the bay. Fresh DDT input is degraded to DDE and DDD within approximately 5 months.