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.     

One-Year Cycle of DDT Concentrations in High-Altitude Soils

Soils are an important sink for persistent organic pollutants (POPs), and high mountain soils are considered a stable reservoir for many compounds due to their high organic matter content. This study focuses on the small-scale variability on the environmental distribution of dichlorodiphenyltrichloroethane (DDT) in mountain soils. Several soil samples taken from May 2007 to June 2008 in a small area at around 1,900 m?a.s.l. (Italian Central Alps) were analyzed for DDT compounds. Pedological analyses were done as well. Organic matter content, soil layer, differences in solar radiation, and sampling period were considered as possible variability factors. Organic matter content can account for a DDT concentration difference of a factor 3 among different sites, soil layer can account for a concentration difference of a factor near 2, differences in solar radiation values do not seem to affect DDT concentrations, whereas the sampling period has the greatest influence with a difference factor of three to four among different sampling dates. Summing all these variability factors together, even though operating on such a small scale, we obtain a predicted spatial variability depending on the considered variables near to one order of magnitude. In particular, it was surprising that seasonal variations could be so great. If this conclusion is to be confirmed in the future, this element must be considered very carefully by scientists and environmental agencies during monitoring campaigns.     

旱地轮作对西藏中部土壤恢复过程的影响

于西藏中部生态条件下,就麦类作物轮作、麦油轮作对土壤化学和生物性质的影响以及农田养分平衡等进行了初步研究。结果表明,不同轮作方式对土壤化学和生物学过程具有显著不同的影响。轮作周期内春青稞→春油菜、春小麦→春油菜轮作对以细菌为主导的土壤微生物的生长与繁殖具有显著的促进作用,耕层土壤有机质、全氮、全磷的绝对增长量分别达3.05~3.06g/kg,0.06~0.07g/kg,0.01~0.26g/kg。麦类作物间,春小麦→春青稞轮作对土壤肥力亦具明显的恢复作用;春小麦→春小麦连作、春青稞→冬小麦轮作土壤微生物区系构成不甚协调,土壤细菌数量明显较低,0~30,31~60cm土层有机质、全氮、全磷总体呈不同程度的退化趋势。在较高外源钾投入条件下,不同轮作方式的土壤钾素均呈不同程度的亏缺状态。     

Ultrasonic Enhanced Desorption of DDT from Contaminated Soils

In this study, using high-power low-frequency ultrasound, heated slurries with anionic surfactant sodium dodecyl sulfate (SDS) were treated to enhance desorption of DDT from soils with high clay, silt, and organic matter content and different pH (5.6?C8.4). The results were compared with DDT extracted using a strong solvent combination as reference. Slurry ranges from 5 to 20 wt.% were studied. For a soil slurry (10 wt.%) at pH 6.9 with 0.1% v/v SDS surfactant heated to 40°C for 30 min, desorption was above 80% in 30 s using 20 kHz, 932 W/L ultrasonic intensity without solvent extraction. Other soils gave lower desorption efficiency in the range 40?C60% after 30 s ultrasonic treatment. The percentage of organic matter, dissolved organic carbon, soil surface area, clay and silt percentage, and soil pH level were the key parameters influencing variations in desorption of DDT in the three soils in similar experimental conditions. DDT dissolution in SDS and soil organic matter removal employing the ultrasonic-enhanced organic matter roll-up mechanism emerged as the two best possible methods of DDT desorption. The method offers a practical, potentially low-cost alternative to high volume, costly, hazardous solvent extraction of DDT.     

唑螨酯在土壤中的降解及淋溶特性

为研究唑螨酯在环境中的行为特性,采用室内模拟试验方法,研究了唑螨酯在土壤中的降解及淋溶特性,通过降解半衰期和比移值Rf来评价其在土壤环境中的安全性。结果表明:唑螨酯在3种土壤中的降解符合一级动力学方程,好气条件下,在黄壤、水稻土和石灰土的降解半衰期分别为81.5、96.3和84.5 d,唑螨酯在水稻土中较难降解,在黄壤和石灰土中中等降解;厌气条件下的半衰期分别为154.0、56.3和43.3 d,水稻土和石灰土中中等降解,黄壤中较难降解。唑螨酯在黄土、水稻土和石灰土中比移值Rf均为0.083,唑螨酯在3种土壤中均不移动,正常条件下不会对地下水造成污染。综上所述,唑螨酯在土壤环境中具有较强的稳定性,因此应严格掌握其使用量和使用时期,同时建议加强对唑螨酯残留的跟踪监测。     

壬基酚在土壤中的降解和吸附特性

采用室内模拟试验,研究了壬基酚（NP）在3种土壤中的降解和吸附特性。结果表明,NP在土壤中的降解分为快速和慢速降解阶段,半衰期分别为6.74～9.72d和70.02～78.77d。降解前期3种土壤中的降解速率相差较大,依次为黑龙江黑土〉北京潮土〉广西红壤,与土壤有机质含量相一致,随培养时间推移,降解速率差异减小。NP在土壤中具有不同结合状态及异构体降解性不同可能是出现慢速降解阶段的主要原因。土壤对NP的吸附较为符合Linear等温吸附方程（r≥0.9686）,黑龙江黑土、北京潮土和广西红壤中吸附常数Kd值分别为65.52、31.66和32.71,黑龙江黑土对NP的吸附最强,广西红壤和北京潮土的吸附能力较为接近。各土壤理化性质参数中,以土壤有机质含量对NP吸附的影响最大（r=0.9950）,阳离子交换量对吸附也有一定影响,粘粒含量和pH对吸附的影响较小。NP在3种土壤中的有机碳吸附常数KOC在3696.22～4334.51之间,移动性很弱,吸附自由能变化均小于40kJ·mol-1,NP在土壤中的吸附以物理吸附为主。     

3种烟碱类杀虫剂在土壤中的降解吸附特性及对地下水的影响

采用室内模拟实验方法,以太湖水稻土、江西红壤和东北黑土为代表性土壤,研究了噻虫啉等3种烟碱类杀虫剂在土壤中的降解、吸附特性,并利用GUS（Ground Ubiquity Score）指数分析了其对地下水污染的影响。结果表明,3种烟碱类杀虫剂在3种土壤中均较易降解,降解半衰期在5～31d之间,属于易降解农药,降解特性与土壤理化性质及农药本身性质有关。3种烟碱类杀虫剂在江西红壤、太湖水稻土与东北黑土中的吸附较好地符合Freundlich方程,Kd值在0.30～14.70之间,KOC在42.8～1750.9之间,属难吸附农药。吸附性强弱与农药本身溶解性和土壤有机质含量有关,水溶性越强吸附越弱,有机质含量越高,吸附性越强。3种烟碱类杀虫剂在太湖水稻土中的GUS值均小于1.8,而在江西红壤中,其GUS值均大于1.8,这3种杀虫剂在江西红壤中均有一定的淋溶性,对地下水均有一定的污染风险。     

Degradation Kinetics of Perchlorate in Sediments and Soils

This study investigated the intrinsic perchlorate (ClO₄ ^-)degradation kinetics of sediments and soils from multiple sites in microcosm studies, including the influence of varying nitrate concentration (NO₃ ^--N from 1 to 22.8 ppm) and up to 300 ppm sulfate. The first-order degradation rates and lag times of both ClO₄ ^- and NO₃ ^- degradation were site-specific and dependent on environmental conditions such as organic substrate availability, nitrate, initial ClO₄ ^- concentration, and prior ClO₄ ^- exposure. At an initial ClO₄ ^- concentration of 5 ppm, ClO₄ ^- degradation rates ranged from 0.13 to 0.46 day^-1, and lag times of ClO₄ ^- degradation ranged from 0 to 60.0 days; while NO₃ ^- degradation occurred at rates ranging from 0.03 to 1.42 day^-1, with lag times ranging from 0 to 29.7 days. Under the same treatment conditions, NO₃ ^- degradation rates were relatively higher than that of ClO₄ ^-. Perchlorate degradation rates remained constant at both lower (0.5 ppm) and higher (5 ppm) ClO₄ ^- concentrations. Generally, ClO₄ ^- rates were affected by the availability of organic substrate, which was represented here by Total Volatile Solids (TVS) of sediments and soils, and not by NO₃ ^-. Nitrate did increase the lag time of ClO₄ ^- degradation, which may account for the persistence of ClO₄ ^- in the environment, especially when ClO₄ ^- is typically ppb levels in the environment compared to ppm levels of NO₃ ^-. This study showed rapid intrinsic ClO₄ ^- degradation in sediments and soils of contaminated sites, and highlighted the potential for natural attenuation of ClO₄ ^- in the environment.     

中国南方侵蚀土壤退化指标体系研究

介绍了国内外土壤退化的评估方法和建立侵蚀土壤退化指标的原则;根据侵蚀土壤的发展过程和属性变化特点,提出了侵蚀土壤退化指标体系;系统全面地论述了侵蚀土壤物理退化、化学退化和生物退化的具体内容和定量指标。为土壤退化从定性研究走向定量化研究提供了有益的方法,同时为科学评估土壤质量变化和防治土壤退化提供重要依据。     

土壤中有机农药的自然降解行为

有机农药是一类典型的环境污染物,自然降解是其在土壤中消除的主要过程。本文阐述了土壤中有机农药生物降解、光解、水解和化学氧化等自然降解机制,综述了土壤中有机农药自然降解的研究方法及研究现状,指出了目前自然降解研究中存在的一些问题并展望了今后的研究方向。     

有机磷农药污染土壤的微生物降解研究进展

有机磷农药是目前我国使用量最大的农药之一,严重污染环境和生态系统,并通过食物链在生物体内富集,进而危害人类健康。微生物降解技术具有降解效率高、代谢途径多、无二次污染的优势,是目前清除环境中有机磷农药的主要手段,能有效降低有机磷农药的危害。目前有机磷农药的降解微生物主要是通过实验室纯培养方法获得,与自然生态环境中存在的降解功能性微生物信息差异较大,而利用不可培养方法识别功能性微生物的技术具有广阔的应用前景。本文从有机磷农药的使用情况及引发的环境问题出发,概述了有机磷农药在土壤中的迁移转化途径,稳定同位素探测技术和磁性纳米材料等不可培养方法对有机磷农药降解功能性微生物的识别,微生物降解有机磷农药污染土壤的功能基因、降解途径及降解机理;探讨了植物–微生物联合修复在有机磷农药污染土壤修复中的作用,并分析了环境因子及农药自身性质对有机磷农药降解的影响;最后,讨论了微生物降解技术存在的问题及今后研究方向。     

哒螨灵农药在土壤中的降解吸附和移动特性

采用室内模拟试验方法,研究了哒螨灵在3种土壤中的降解、吸附和移动特性。结果表明,25℃下,哒螨灵在江西红壤、河南二合土和东北黑土中的降解半衰期分别为41．0、55．9和72．2d,属于易降解农药,其降解速率依次为江西红壤〉河南二合土〉东北黑土。酸性条件有利于哒螨灵的降解,土壤pH值对哒螨灵降解的影响比土壤有机质含量大。3种土壤对哒螨灵农药的吸附均较好地符合Freundich方程,吸附系数鼠值分别为3．35×10^3,6．17×10^3和8．48×10^3,具有极强的吸附性,且土壤有机质含量越高,对哒螨灵的吸附性越强。土壤对哒螨灵的吸附自由能变化均小于40kJ·mol^-1,属于物理吸附。哒螨灵在土壤中不易移动,3种土壤薄层移动试验的Rf值均仅为0．05,正常条件下不会造成对地下水的污染。     

Degradation and Leaching of Simazine in Arctic Sandy Soils

Abstract

Degradation and leaching of ¹⁴C-labelled simazine in coarse sandy soils at 15 + 1°C were investigated using radiometric and mass-spectrometric methods. During 6 months incubation approx. 4–7% of the applied ¹⁴C-simazine was evolved as ¹⁴CO₂. 4–9% of the simazine still remained in the soil. Addition of hen manure or acidification by addition of peat did not clearly influence the rate of degradation of simazine, whereas mechanical treatment significantly increased its degradation. In a nitrogen atmosphere the rate of degradation of simazine was reduced.

9–15% of the simazine or its radioactive metabolites leached through a 33 cm sandy moraine soil column (diameter 6 cm) in ca. 1770 mm of precipitation over a 4 month period, and 2% was leached from a fine sand soil under the same conditions.     

恶唑菌酮土壤降解影响因子研究

探讨了土壤环境中的主要因素:土壤微生物、温度、含水量、pH值以及施用有机肥对恶唑菌酮降解的影响。结果表明:土壤微生物对恶唑菌酮在土壤中的降解起着重要作用,相同条件下灭菌土壤的降解半衰期是非灭菌土壤的27.6倍。环境温度、土壤含水量等对恶唑菌酮降解也有影响,在15℃～40℃的试验条件下,随着温度升高,恶唑菌酮的降解速率加快,特别是15℃～25℃温度范围内降解速率上升较快;过高和过低的土壤含水量都不利于土壤中恶唑菌酮的降解,土壤含水量为50?～100?时适宜恶唑菌酮的降解;此外施用有机肥会加速恶唑菌酮的降解;而土壤pH值对降解的影响不显著。     

虱螨脲在土壤中的降解、吸附和移动特性

采用室内模拟试验方法,研究了虱螨脲在3种土壤中的降解、吸附和移动特性。结果表明：25℃下,虱螨脲在江西红壤中的降解半衰期为101d,属于中等降解农药;在太湖水稻土和东北黑土中的降解半衰期分别为74.5d和55.5d,属于较易降解农药。土壤有机质含量是影响虱螨脲降解速率的主要因素;3种土壤对虱螨脲具有较强的吸附性,且土壤有机质含量越高,对虱螨脲的吸附性越强;3种土壤对虱螨脲的吸附自由能变化均小于40kJ·mol^-1,属于物理吸附;虱螨脲在土壤中不易移动,正常条件下不会造成地下水的污染。     

双草醚在稻田土壤中的降解及其影响因子的研究

采用了实验室模拟方法研究了双草醚在不同土壤中的降解动态。结果表明,在未灭菌的土壤中,双草醚三种浓度(2.0、10.0、50.0mg kg-1)处理的半衰期为7.6~10.3d,远远小于在灭菌土壤中3种添加浓度处理的半衰期(43.3~61.9 d);双草醚在偏酸土壤中降解较快,随着土壤含水量的增加和环境温度的增高,双草醚降解速度加快。4种试验因子中土壤微生物是影响双草醚降解的主要因素,有利于土壤中微生物生长的环境因素,如偏酸的土壤、较高的温度和土壤湿度等,也能促进土壤中双草醚的降解。     

不同施肥条件下氯氰菊酯对土壤酶活性的影响及其降解差异

采用长期定位施肥试验土壤（轻壤质黄潮土），研究不同施肥条件下，氯氰菊酯降解变化和对土壤酶活性的影响。结果表明，不同的施肥处理对土壤中氯氰菊酯的降解行为有显著影响，长期施用氮肥，土壤中速效氮含量升高，对氯氰菊酯降解有抑制作用；施用磷肥则促进降解；施用有机肥在提高土壤有机质含量的同时，虽加速了氯氰菊酯降解，但降解延滞期和残留期有所增加。氯氰菊酯在土壤中的降解遵循一级动力学方程，降解半衰期为10．13d（PK）～14．58d（NK）。土壤中加入氯氰菊酯后，脱氢酶、脲酶活性有所升高，施肥处理不同，升高幅度也不一样．均达显著水平。磷酸酶活性变化在不同施肥处理中，表现不一样。培养26d左右，土壤酶活性大多都能恢复到初始水平。研究土壤中农药残留与施肥、土壤酶活性的关系，对于实现农业可持续发展具有重要意义。     

好氧条件下环氧虫啶在土壤中的快速降解研究

为明确环氧虫啶异构体在土壤环境中的迁移转化及代谢降解规律,本试验以14C标记外消旋环氧虫啶为示踪剂,综合运用核素示踪与高效液相色谱分离技术,研究了好氧条件下环氧虫啶在3种土壤中的快速降解动态规律,并分析了其形成结合残留和母体降解可能的对映体选择特性。结果表明,好氧条件下环氧虫啶在整个培养期(120 h)内,未发现其2种对映异构体的结合残留形成和母体降解具有手性差异。环氧虫啶在3种土壤中均迅速形成结合残留,其结合残留量由高到低依次为中性黄松土、碱性滨海盐土、酸性红砂土。环氧虫啶属于易降解农药,好氧条件下环氧虫啶在3种土壤中的降解动态显著符合一级动力学方程,其降解速率由快到慢依次为酸性红砂土(半衰期为23.10 h)、中性黄松土(半衰期为53.32 h)、碱性滨海盐土(半衰期为77.02 h)。数据分析还表明,土壤p H对环氧虫啶的降解速率影响最大。本研究为环氧虫啶的登记注册奠定了基础,为环氧虫啶的正确、合理使用提供了科学依据。