不同气候情景下甘肃草地碳收支时空模拟与预测

在碳达峰、碳中和的背景下,草地碳汇是实现碳中和的关键路径.基于第六次国际耦合模式比较计划（CMIP6）气候情景数据,运用Daycent模型对甘肃草地2015~2100年碳收支进行模拟,并利用趋势分析法研究未来78 a草地碳收支的时空变化规律.结果表明,SSP245未来气候情景下,净生态系统生产力（NEP）呈不显著波动下降趋势,速率（以C计,下同）达-0.20 g ·（m² ·a）^-1,且该情景下草地碳汇处于下降状态;SSP585未来气候情景下,草地NEP以1.36 g ·（m² ·a）^-1的速率呈显著波动上升趋势,草地碳汇逐渐增加;草地碳收支的空间分布由西北向东南递增;SSP585气候情景下的温度和降水的增幅高于SSP245的气候情景,且草地碳收支与降水量的变动具有一致性,与温度的变化呈反向关系.研究明确了在不同气候情景下甘肃草地的碳汇强度,对有效固碳有参考和促进作用.     

北京松山国家级自然保护区典型植被类型表层土壤碳密度及周转速率特征

为阐明不同植被类型下表层土壤有机碳的分布特征,本文选取北京松山国家级自然保护区内胡桃楸阔叶林、蒙古栎阔叶林、油松针叶林、针阔叶混交林、灌丛和草甸6种典型植物群落作为研究对象,基于野外调查、采样与实验室分析对不同植被类型下表层土壤有机碳含量、密度及周转速率进行了研究。结果表明：草甸表层土壤有机碳含量和密度最高,分别为188.5 g/kg和10.9 kg/m²,周转速率最低,为0.019 6/a;针阔叶混交林表层土壤有机碳含量和密度最低,分别为68.6 g/kg和5.7 kg/m²,周转速率为0.074 9/a;灌丛表层土壤有机碳周转速率为0.077 4/a。土壤有机碳含量整体上随土壤深度增加而逐渐减少。土壤水分的增加和土壤温度的下降使表层土壤有机碳含量及密度呈上升趋势,而使有机碳周转速率呈下降趋势。土壤有机碳密度随海拔升高呈逐渐上升趋势。海拔通过影响不同植被群落土壤水热条件来影响微生物活动及凋落物的分解,进而影响表层土壤有机碳含量、密度和周转速率。本文为松山国家级自然保护区典型植被类型土壤碳储量和周转研究提供了有效参考。     

基于SSP-RCP情景的黄土高原土地变化模拟及草原碳储量

探索未来气候变化情景下土地利用/覆盖变化（LUCC）和生态系统碳储量的空间分布,可以为优化土地资源再分配和制定社会经济可持续发展政策提供科学依据.研究整合了斑块生成土地利用模拟（PLUS）模型和生态系统服务与权衡综合评价（InVEST）模型,基于CMIP6提供的共享社会经济路径和代表性浓度路径（SSP-RCP）情景,评估了黄土高原LUCC和生态系统碳储量的时空动态变化,分析驱动因素对不同区域的影响程度,探讨各区域碳储量空间相关性.结果表明：①未来3种情景LUCC变化模式相似,耕地、草地和未利用地面积都有不同程度的减少,建设用地急剧扩张,3种情景下的增幅分别为29.23%~53.56%（SSP126）、34.59%~63.28%（SSP245）和42.80%~73.27%（SSP585）.②与2020年相比,2040年SSP126情景碳储量增加1.813 8×10⁶ t,其余情景持续下降;到2060年,3种情景草原碳储量分别减少13.391×10⁶、33.548×10⁶和85.871×10⁶ t.③从空间相关性来看,黄土高原碳储量在市域间存在相关性,未来情景差异不显著,热点分布在研究区中部及中部以北地区,没有明显的冷点区域.④土地利用变化会增加或损失碳储量.林地、耕地和草地比其它土地类型有更多的碳储量,增加它们的面积和限制向其它土地类型转换会增加生态系统碳储量.     

基于SSPs情景的中国极端降水影响评估

气候变化对区域经济系统造成的影响不容忽视。中国为应对全球气候变化做出努力争取2060年前实现碳中和的承诺。然而,我国碳中和路径设计需要考虑不同气候情景下气候风险的差异。如何评估不同气候情景下气候变化对经济系统的影响,尤其是极端天气气候事件的经济损失评估对减缓或适应气候变化提供重要指导信息。本研究基于参与CMIP6计划的BCC-CSM2-MR气候系统模式气候模拟资料,构建气候灾害经济损失函数,并预估不同SSPs情景下中国区域极端降水天气灾害的直接经济损失。结果显示,在高碳排放SSP585情景下,如没有适应能力的改善,中国极端降水事件的经济损失值将比排放量较低的SSP126和SSP370情景高,且这种趋势将逐渐扩大,在2090—2100年,年均直接GDP损失值可达2.4万亿元。     

嘉善冬季碳质气溶胶变化特征及其来源解析

利用2018年冬季（2018年12月至2019年2月）和2019年冬季（2019年12月至2020年2月）嘉兴市嘉善县善西超级站有机碳（OC）、元素碳（EC）及细颗粒物（PM_2.5）浓度数据分析嘉兴嘉善地区碳质气溶胶变化特征及潜在来源区域.结果表明,2018年和2019年冬季OC浓度分别为6.90μg·m^-3和5.63μg·m^-3,EC浓度分别为2.47μg·m^-3和1.57μg·m^-3,2019年冬季OC和EC浓度较2018年冬季降幅分别为18.4%和36.4%.利用Minimum R-squared （MRS）方法计算得到2018年和2019年冬季二次有机碳（SOC）分别为1.49μg·m^-3和1.97μg·m^-3,一次有机碳（POC）浓度分别为5.41μg·m^-3和3.66μg·m^-3,SOC在OC中占比呈上升趋势,上升31.1个百分点,POC占比变化则相反.值得注意的是,随着PM_2.5浓度升高,OC和EC浓度呈上升趋势,最高上升幅度分别为474.7%和408.2%,但在PM_2.5中占比却呈下降趋势,OC和EC占比下降幅度分别为6.5个百分点和2.4个百分点;POC对PM_2.5的贡献波动不大,仅在150μg·m^-3以上有明显降低趋势,SOC对PM_2.5的贡献先下降后上升.嘉兴OC和EC潜在源区主要为苏南地区、安徽东南部和浙江北部,且2019年冬季和2018年冬季相比,OC和EC的主要潜在源区贡献浓度分别下降2μg·m^-3和6μg·m^-3以上,且潜在源区高值区域变小.疫情前受机动车尾气排放和燃煤共同影响,春节和居家隔离期间,因交通管制等原因,机动车排放量减少,燃煤贡献占比上升.     

黄土丘陵区不同恢复植被类型的固碳特征

为分析黄土高原水土流失严重区不同恢复植被类型的固碳特征,比较恢复年限和坡向因素对植被碳汇效应的影响,在陕北黄土丘陵区选取了6种典型植被类型（农地、草地、沙棘、柠条、刺槐和山杨）,研究了不同类型的生态系统碳密度及其构成特征.结果表明：①半干旱黄土区植被恢复具有明显的碳汇功能,不同植被组分（地上生物、地下根系和枯落物）碳密度均表现出乔木>灌丛>草地>农地的变化特征.农地0~40 cm土层土壤有机碳密度最低（1355.5 g ·m^-2）,草地、沙棘、柠条、刺槐和山杨较农地分别增加了91.4%、125.2%、144.0%、124.5%和232.6%.②草地、沙棘、柠条和山杨的不同植被组分碳密度和不同土层（0~5、5~20和20~40 cm）土壤有机碳密度随恢复时间的推移总体上表现出增加趋势.③坡向对农地和草地植被碳密度无明显影响,沙棘、柠条、刺槐和山杨不同坡向间的植被碳密度差异明显.土壤有机碳密度存在明显的阴阳坡差异,农地、草地、沙棘、柠条、刺槐和山杨阳坡土壤有机碳密度分别比阴坡减少了22.9%、34.3%、75.8%、49.1%、22.4%和69.4%.④不同类型的生态系统碳密度差异明显,其中农地最低（2022.1 g ·m^-2）,草地、沙棘、柠条、刺槐和山杨较农地分别增加了48.7%、152.8%、125.1%、166.3%和530.7%.生态系统各组分碳密度总体表现为：土壤层>地上生物层>根系层>枯落物层.土壤有机碳构成了农地、草地、沙棘、柠条和刺槐碳密度的主体,分别占生态系统碳密度的67.0%、86.3%、59.7%、72.7%和56.5%.研究结果可为黄土高原地区科学管理生态系统碳库和推进生态环境治理提供重要依据.     

1981—2010年内蒙古草地土壤有机碳时空变化及其气候敏感性

草地土壤有机碳储量巨大,其较小幅度的波动即可能显著反馈于气候变化. 基于1981—2010年内蒙古自治区境内及其周边共计92个气象台站气候要素插值数据,采用空间化的生物地球化学模型——CENTURY 4.5,模拟分析近30年来内蒙古草地表层(0~20 cm)土壤有机碳的空间格局与动态变化特征,并通过构建气候变化情景探讨其对主要气候要素的敏感性. 结果表明:近30年内蒙古草地表层土壤有机碳密度平均值约为1.99 kg/m2(以C计),在空间上呈由东北向西南逐渐减少的分布特征. 近30年来内蒙古草地表层土壤有机碳密度略有增加,年均增幅约0.22%,其中草甸草原的增速〔14.25 g/(m2·a)〕最大,荒漠草原的增速〔1.36 g/(m2·a)〕最小. 草地表层土壤有机碳密度年际变化差异明显,1980s至1990s的增加较为缓慢,1990s至2000s的增幅约为前者的2倍,其中草甸草原和典型草原土壤有机碳增幅较大. 气候敏感性分析结果显示,区域降水量变化可能是近30年内蒙古草地表层土壤有机碳密度变化的主要影响因素,但不同草地类型表层土壤有机碳密度对气候变化的敏感性存在较大差异;典型草原与草甸草原表层土壤有机碳变化主要受控于降水量变化,荒漠草原则主要受控于温度变化.      

沙漠化过程中科尔沁沙地植物-土壤系统碳氮储量动态

研究了科尔沁沙地不同沙漠化阶段(潜在、轻度、中度、重度和严重沙漠化)植物-土壤系统的有机碳与氮储量,以揭示沙漠化对碳氮动态的影响.结果表明,从潜在沙漠化到轻度、中度、重度和严重沙漠化,生物量(地上与地下)有机碳储量分别下降26.4%、51.0%、79.0%和91.0%,生物量氮储量分别下降33.6%、66.9%、87.4%和93.2%;土壤有机碳储量分别下降52.2%、75.9%、87.0%和90.1%,土壤全氮储量分别下降43.5%、71.0%、81.3%和82.7%.植物-土壤系统的有机碳与氮储量大小为:潜在沙漠化(C:5 266 g·m^-2和N:534 g·m^-2)>轻度沙漠化(C:2 619 g·m^-2和N:303 g·m^-2>中度沙漠化(C:1368 g·m^-2和N:156 g·m^-2)>重度沙漠化(C:715 g·m-^-2和N:99 g·m^-2)>严重沙漠化(C:517 g·m^-2和N:91 g·m^-2).研究结果表明,生物量碳氮储量的衰减在沙漠化后期(从重度到严重)快于沙漠化初期(从潜在到轻度),而土壤碳氮储量的衰减在沙漠化初期快于沙漠化后期;沙漠化过程中土壤有机碳储量的衰减要快于全氮,而生物量氮储量的衰减在沙漠化初期快于碳,在后期则相反.     

典型湿地生态系统碳循环模拟与预测

以植物生理生态特性和有机碳周转动力学原理为基础,利用室内模拟培养试验结果率定了温度、积水强度、冻融交替对湿地有机碳分解矿化的影响参数,建立了典型湿地生态系统碳循环模拟模型.利用实地观测的数据对模型进行了检验,对模型的灵敏性进行了分析,同时利用该模型进行了情景预测.结果表明,所建模型能较好地模拟中温带（三江平原）和亚热带（洞庭湖）湿地生态系统的碳通量和碳累积特征,沉积物呼吸的模拟值与实测值呈极显著相关关系（p<0.01）;三江平原常年积水沼泽有机碳密度约为80×10⁹ g·km^-2,洞庭湖湿地碳密度约为20×10⁹ g·km^-2;三江平原常年积水沼泽和季节性积水沼泽每年碳的净固定速率分别为104　g·m^-2和76 g·m^-2;该模型对温度和大气CO₂浓度变化反应敏感.在既定的水文条件下,大气CO₂浓度升高和增温可能会使湿地生态系统的碳交换变得更为活跃;在CO₂浓度倍增和增温小于2.5℃的气候变化情景时,系统净初级生产力（NPP）和积累的有机碳密度增加,系统仍为大气的CO₂ 汇,但气候变暖的进一步加剧并不利于湿地有机碳的积累,由于CO₂施肥效应和温度升高增加的系统NPP补偿不了因温度升高导致的沉积物呼吸速率加快而损失的碳,季节性积水沼泽生态系统积累的有机碳甚至出现明显的下降趋势.     

基于MGWR的黄河流域土壤有机碳密度和影响因素分析

土壤有机碳作为最大陆地碳库,其空间分布特征和影响因素对于全球碳循环过程具有重要影响.基于土壤有机碳密度数据,结合环境因子,使用多尺度地理加权回归（MGWR）模型预测了黄河流域土壤有机碳密度（SOCD）和影响因素.结果表明：①黄河流域0~20 cm和0~100 cm的SOCD范围分别为0~14.82 kg ·m^-2和0~32.39kg ·m^-2,均值分别为3.48 kg ·m^-2和8.07kg ·m^-2,储量则分别为2.76 Pg和6.48 Pg;②各生态系统类型中,0~20 cm的SOCD从大到小依次为：森林>水体与湿地>其他>草地>农田>聚落>荒漠,0~100 cm的SOCD从大到小依次为：水体与湿地>森林>其他>草地>农田>聚落>荒漠,SOCR从大到小皆为：草地>农田>森林>荒漠>水体与湿地>聚落>其他;③黄河流域SOCD的分布主要受常数项、剖面曲率、NDVI和降水的影响,曲率和粉砂对深层的SOCD的分布也具有重要影响;此外,降水、NDVI和常数项（除森林外）是影响各生态系统的主要因素,曲率和粉砂则仅对荒漠和其他生态系统具有重要影响.研究结果得出了黄河流域SOCD的空间分布和影响因素,可为黄河流域碳平衡、土壤质量评价和生态治理恢复与巩固提升提供科学依据.     

Toxic effects of acetochlor, methamidophos and their combination on nifH gene in soil

Toxic effects of two agrochemicals on nifH gene in agricultural black soil were investigated using denaturing gradient gel electrophoresis （DGGE） and sequencing approaches in a microcosm experiment. Changes of soil nifH gene diversity and composition were examined following the application of acetochlor, methamidophos and their combination. Acetochlor reduced the nifH gene diversity （both in gene richness and diversity index values） and caused changes in the nifH gene composition. The effects of acetochlor on nifH gene were strengthened as the concentration of acetochlor increased. Cluster analysis of DGGE banding patterns showed that nifH gene composition which had been affected by low concentration of acetochlor （50 mg/kg） recovered firstly. Methamidophos reduced nifH gene richness that except at 4 weeks. The medium concentration of methamidophos （150 mg/kg） caused the most apparent changes in nifH gene diversity at the first week while the high concentration of methamidophos （250 mg/kg） produced prominent effects on nifH gene diversity in the following weeks. Cluster analysis showed that minimal changes of nifH gene composition were found at 1 week and maximal changes at 4 weeks. Toxic effects of acetochlor and methamidophos combination on nifH gene were also apparent. Different nifH genes （bands） responded differently to the impact of agrochemicals： four individual bands were eliminated by the application of the agrochemicals, five bands became predominant by the stimulation of the agrochemicals, and four bands showed strong resistance to the influence of the agrochemicals. Fifteen prominent bands were partially sequenced, yielding 15 different nifH sequences, which were used for phylogenetic reconstructions. All sequences were affiliated with the alpha- and beta-proteobacteria, showing higher similarity to eight different diazotrophic genera.     

Arsenic uptake by arbuscular mycorrhizal maize （Zea mays L.） grown in an arsenic-contaminated soil with added phosphorus

The effects of arbuscular mycorrhizal (AM) fungus (Glomus mosseae) and phosphorus (P) addition (100 mg/kg soil) on arsenic (As) uptake by maize plants (Zea mays L.) from an As-contaminated soil were examined in a glasshouse experiment.Non-mycorrhizal and zero-P addition controls were included.Plant biomass and concentrations and uptake of As,P,and other nutrients,AM colonization,root lengths,and hyphal length densities were determined.The results indicated that addition of P significantly inhibited root colonization and development of extraradical mycelium.Root length and dry weight both increased markedly with mycorrhizal colonization under the zero-P treatments,but shoot and root biomass of AM plants was depressed by P application.AM fungal inoculation decreased shoot As concentrations when no P was added,and shoot and root As concentrations of AM plants increased 2.6 and 1.4 times with P addition,respectively.Shoot and root uptake of P,Mn,Cu,and Zn increased,but shoot Fe uptake decreased by 44.6%,with inoculation, when P was added.P addition reduced shoot P,Fe,Mn,Cu,and Zn uptake of AM plants,but increased root Fe and Mn uptake of the nonmycorrhizal ones.AM colonization therefore appeared to enhance plant tolerance to As in low P soil,and have some potential for the phytostabilization of As-contaminated soil,however,P application may introduce additional environmental risk by increasing soil As mobility.     

Degradation of metabolites accumulated of benzo[a]pyrene by coupling Penicillium Chrysogenum with KMnO4

Several main metabolites of benzo[a]pyrene （BaP） formed by Penicillium chrysogenum, Benzo[a]pyrene-1,6-quinone （BP 1,6- quinone）, trans-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene （BP 7,8-diol）, 3-hydroxybenzo[a]pyrene （3-OHBP）, were identified by high-performance liquid chromatography （HPLC）. The three metabolites were liable to be accumulated and were hardly further metabolized because of their toxicity to microorganisms. However, their further degradation was essential for the complete degradation of BaP. To enhance their degradation, two methods, degradation by coupling Penicillium chrysogenum with KMnO4 and degradation only by Penicillium chrysogenum, were compared; Meanwhile, the parameters of degradation in the superior method were optimized. The results showed that （1） the method of coupling Penicillium chrysogenum with KMnO4 was better and was the first method to be used in the degradation of BaP and its metabolites; （2） the metabolite, BP 1,6-quinone was the most liable to be accumulated in pure cultures; （3） the effect of degradation was the best when the concentration of KMnO4 in the cultures was 0.01% （w/v）, concentration of the three compounds was 5 mg/L and pH was 6.2. Based on the experimental results, a novel concept with regard to the bioremediation of BaP-contaminated environment was discussed, considering the influence on environmental toxicity of the accumulated metabolites.     

Impact of atrazine and nitrogen fertilizers on the sorption of chlorotoluron in soil and model sorbents

Sorption of chlorotoluron in ammonium sulfate, urea and atrazine multi-solutes system was investigated by batch experiments. The results showed application of nitrogen fertilizers to the soil could affect the behavior of chlorotoluron. At the same concentration of N, sorption of chlorotoluron decreased as the concentration of atrazine increased on the day 0 and 6 in soil, respectively. The sorption of chlorotoluron increased from 0 to 6 d when soils were preincubated with deionized water, ammonium sulfate and urea solution for 6 d. That indicated incubation time was one of the most important factors for the sorption of chlorotoluron in nitrogen fertilizers treatments. The individual sorption isotherms of chlorotoluron in rubbery polymer and silica were strictly linear in single solute system, but there were competition sorption between pesticides or between pesticides and nitrogen fertilizers. That indicated the sorption taken place by concurrent solid-phase dissolution mechanism and sorption on the interface of water-organic matter or water-mineral matter.     

Potential of plant polyphenol oxidases in the decolorization and removal of textile and non-textile dyes

In this study an effort has been made to use plant polyphenol oxidases; potato （Solanum tuberosum） and brinjal （Solanum melongena）, for the treatment of various important dyes used in textile and other industries. The ammonium sulphate fractionated enzyme preparations were used to treat a number of dyes under various experimental conditions. Majority of the treated dyes were maximally decolorized at pH 3.0. Some of the dyes were quickly decolorized whereas others were marginally decolorized. The initial first hour was sufficient for the maximum decolorization of dyes. The rate of decolorization was quite slow on long treatment of dyes. Enhancement in the dye decolorization was noticed on increasing the concentration of enzymes. The complex mixtures of dyes were treated with both preparations of polyphenol oxidases in the buffers of varying pH values. Potato polyphenol oxidase was significantly more effective in decolorizing the dyes to higher extent as compared to the enzyme obtained from brinjal polyphenol oxidase. Decolorization of dyes and their mixtures, followed by the formation of an insoluble precipitate, which could be easily removed simply by centrifugation.     

Removal of heavy metals from sewage sludge by low costing chemical method and recycling in agriculture

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Single and joint effects of pesticides and mercury on soil urease

The influence of two pesticides including chlorimuron-ethyl and furadan and mercury （Hg） on urease activity in 4 soils （meadow burozem and phaeozem） was investigated. The soils were exposed to various concentrations of the two pesticides and Hg individually and simultaneously. Results showed that there was a close relationship between urease activity and organic matter content in soil. Chlorimuron-ethyl and furadan could both activate urease in the 4 soils. The maximum increment of urease activity by chlorimuronethyl was up to 14%-18%. There was almost an equal increase （up to 13%-21%） in the urease activity by furadan. On the contrary, Hg markedly inhibited soil urease activity. A logarithmic equation was used to describe the relationship （P〈0.05） between the concentration of Hg and the activity of soil urease in the 4 tested soils. Semi-effect dose （ED50） values by the stress of Hg based on the inhibition of soil urease in the 4 soils were 88, 5.5, 24 and 20 mg/kg, respectively, according to the calculation of the corresponding equations. The interactive effect of chlorimuron-ethyl or furadan with metal Hg on soil urease was mainly synergic at the highest tested concentrations.     

Isolation and preliminary characterization of a 3-chlorobenzoate degrading bacteria

A study was conducted to compare the diversity of 2-, 3-, and 4-chlorobenzoate degraders in two pristine soils and one contaminated sewage sludge. These samples contained strikingly different populations of mono-chlorobenzoate degraders. Although fewer cultures were isolated in the uncontaminated soils than contaminated one, the ability of microbial populations to mineralize chlorobenzoate was widespread. The 3- and 4-chlorobenzoate degraders were more diverse than the 2-chlorobenzoate degraders. One of the strains isolated from the sewage sludge was obtained. Based on its phenotype, chemotaxonomic properties and 16S rRNA gene, the organism S-7 was classified as Rhodococcus erythropolis. The strain can grow at temperature from 4 to 37℃. It can utilize several （halo）aromatic compounds. Moreover, strain S-7 can grow and use 3-chlorobenzoate as sole carbon source in a temperatures range of 10-30℃ with stoichiometric release of chloride ions. The psychrotolerant ability was significant for bioremediation in low temperature regions. Catechol and chlorocatechol 1,2-dioxygenase activities were present in cell free extracts of the strain, but no （chloro）catechol 2,3- dioxygenase activities was detected. Spectral conversion assays with extracts from R. erythropolis S-7 showed accumulation of a compound with a similar UV spectrum as chloro-cis,cis-muconate from 3-chlorobenzoate. On the basis of these results, we proposed that S-7 degraded 3-chlorobenzoate through the modified ortho-cleave pathway.     

Organochlorine pesticides in soils under different land usage in the Taihu Lake region, China

A field study was conducted in the Taihu Lake region, China in 2004 to reveal the organochlorine pesticide concentrations in soils after the ban of these substances in the year 1983. Thirteen organochlorine pesticides (OCPs) were analyzed in soils from paddy field, tree land and fallow land. Total organochlorine pesticide residues were higher in agricultural soils than in uncultivated fallow land soils. Among all the pesticides, ΣDDX (DDD, DDE and DDT) had the highest concentration for all the soil samples, ranging from 3.10 ng/g to 166.55 ng/g with a mean value of 57.04 ng/g and followed by ΣHCH, ranging from 0.73 ng/g to 60.97 ng/g with a mean value of 24.06 ng/g. Dieldrin, endrin, HCB and α-endosulfan were also found in soils with less than 15 ng/g. Ratios of p,p'-(DDD DDE)/DDT in soils under three land usages were: paddy field ＞ tree land ＞ fallow land, indicating that land usage inlfuenced the degradation of DDT in soils. Ratios of p,p'-(DDD DDE)/DDT ＞1, showing aged residues of DDTs in soils of the Taihu Lake region. The results were discussed with data from a former study that showed very low actual concentrations of HCH and DDT in soils in the Taihu Lake region, but according to the chemical half-lives and their concentrations in soils in 1980s, the concentration of DDT in soils seemed to be underestimated. In any case our data show that the ban on the use of HCH and DDT resulted in a tremendous reduction of these pesticide residues in soils, but there are still high amounts of pesticide residues in soils, which need more remediation processes.     

Sorption of 1-naphthol by plant cuticular fractions

The contribution of aliphatic-rich plant biopolymer to sorption of hydrophobic organic compounds is significantly important because of their preservation and accumulation in the soil environment,but sorption mechanism is still not fully understood.In this study, sorption of 1-naphthol by plant cuticular fractions was examined to better understand the contributions of respective fraction.Toward this end,cuticular materials were isolated from the fruits of tomato by chemical method.The tomato cuticle sheet consisted of waxes (6.5 wt%),cuticular monomer (69.5 wt%),and polysaccharide (24.0 wt%).Isotherms of l-naphthol to the cuticular fractions were nonlinear (N value (0.82-0.90)) at the whole tested concentration ranges.The KodKow ratios for bulk cuticle (TC1),dewaxed cuticle (TC2),cutin (TC4),and desugared cuticle (TC5) were larger than unity,suggested that tomato bulk cuticle and cutin are much powerful solption medium.Sorption capability of cutin (TC4) was 2.4 times higher than the nonsaponifiable fraction (TC3).The 1-naphthol interactions with tomato cuticular materials were governed by both hydrophobic-type interactions and polar (H-bonding) interactions. Removal of the wax and polysaccharide materials from the bulk tomato cuticle caused a significant increase in the sorption ability of the cuticular material.There was a linear negative trend between K_(oc) values and the amount of polysaccharides or fraction's polarities ((N O)/C);while a linear positive relationship between K_(oc) values and the content of cutin monomer (linear R~2=0.993) was observed for present in the cuticular fractions.Predominant sorbent of the hydrophobic organic compounds (HOCs) in the plant cuticular fraction was the cutin monomer,contributing to 91.7% of the total sorption of tomato bulk cuticle.