Effects of repeated applications of fungicide carbendazim on its persistence and microbial community in soil

Carbendazim, a systemic benzimidazole fungicide, is applied repeatedly to control of plant diseases including soilborne diseases, over a growing season. Studies were carried out under laboratory conditions to assess the effects of repeated carbendazim applications on its persistence and microbial community in soil. The results indicate that dissipation of carbendazim in soil was accelerated with its application frequency. The degradation rate constant of carbendazim was increased significantly from 0.074 d-1 to 0.79 d-1. The corresponding half-life was shorten markedly from 9.3 d to 0.9 d after four repeated applications. No significant inhibitory effect of carbendazim on soil microbial utilization of the carbon sources was observed after first treatment, but a slight increase in average well color development (AWCD) was shown after second, third, and fourth applications. It suggested that soil microorganisms become adapted to carbendazim after repeated application. Simpson and Shannon indexes of soil microbial community from carbendazim treated soil were also similar to those from the control soil, indicating that the richness and dominant character of soil microorganisms remain unchangeable after repeated application. However, after first, second, and third addition of carbendazim, McIntosh indexes on day 21 were significantly increased as compared with the control, suggesting that balance of soil microorganisms was altered due to the enrichment of the specific carbendazim-adapting strains in soil.     

Effects of pesticides on soil biochemical characteristics of a paddy soil

IntroductionThemaintenanceofsoilfertilitydependsonthesizeandtheactivityofthesoilmicrobialbiomasswhichisoffundamentalimportanceinbiologicalcyclesofalmostallmajorplantnutrients(Robert,1992 ) .Thereisconsiderableinterestinstudyofsoilbiochemicalcharacteristic…     

理化性质对土壤吸附-解吸苄嘧磺隆的影响

为探讨土壤理化性质对其吸附-解吸BSM(苄嘧磺隆)的影响,采用批量平衡法研究了采自我国东南沿海和中部14个省区的21个土壤样品对BSM的吸附-解吸行为,以及BSM吸附-解吸行为与土壤pH、w(有机质)、w(TN)、w(黏粒)、CEC(阳离子交换量)等理化性质的关系. 结果表明:BSM在土壤中的等温吸附线可用Freundlich方程进行拟合,不同土壤对BSM的吸附强度差异较大,K_f (Freundlich常数)介于0.52~24.05之间. 土壤pH、w(有机质)是影响BSM吸附的主要因素,二者对K_f的解释率为58.1%;土壤对BSM的吸附还受w(TN)、w(黏粒)等的影响. 土壤对BSM的吸附-解吸存在滞后现象,HI(迟滞系数)与土壤pH呈极显著负相关,与w(黏粒)呈显著正相关,其中土壤pH对HI的解释率为33.0%. 吸附平衡溶液pH与K_d (分配系数)呈极显著负相关,对其进行调节可显著改变土壤对BSM的分配能力.      

Movement and degradation of aldicarb residues in South Carolina loamy sand soil

The movement and degradation of aldicarb (2-methyl-2-(methylthio)propionaldehyde O-(methylcarbamoyl)oxime) residues was measured in a Dotham loamy sand soil in Barnwell County in southern South Carolina. The experiment was designed to compare movement in a fallow plot versus a soya bean plot and to compare residue results from soil suction lysimeters and soil samples. The soil sample data indicate that aldicarb degraded at a rate corresponding to a half life of approximately 9 days with essentially no residues present 4 months after application. This degradation rate is faster than the 14–39-day half-life measured in nearby states. Because this relatively rapid degradation rate generally constrained residue movement to the upper 0.3 m in both plots (resulting in no significant residues in the lysimeters and monitoring wells), comparison between data from soil cores and suction lysimeters was not possible and the reduced evapotranspiration in the fallow plot had little effect on residue movement. Simulations using the unsaturated zone model PRZM with rainfall records from 15 years were used to illustrate that aldicarb residues should be limited to the upper 1.5 m, regardless of year-to-year variations in rainfall.     

生物堆修复城市多环芳烃污染土壤的调控研究

土壤多环芳烃(PAHs)污染已成为一种严重的全球性城市环境问题。以通风时间、绿肥、无机营养剂和疏松剂含量为调控因素,利用现场规模的正交试验进行了生物堆修复城市多环芳烃污染土壤的调控研究。结果表明,所有生物堆处理对土壤PAHs的去除均有一定促进作用,75 d时平均降解率为30.63%~80.41%,且深层土壤降解率比表层土壤高8.55%;运行期间各调控因素对不同深度土壤PAHs降解的影响程度和作用规律各不相同,其中通风时间始终是主导因素,且通风时间越长,降解效果越好;生物堆的最佳运行条件总体上为通风时间3 h、绿肥3.5%、营养剂0.2%、疏松剂18%(表层土壤)或14%(深层土壤)。因此,利用生物堆修复城市PAHs污染土壤是有效的,且增加通风时间是提高其修复效率的优先调控方式。     

除草剂苄嘧磺隆在土壤中的吸附

应用平衡法研究了除草剂苄嘧磺隆在8种土壤中的吸附特性．结果表明,土壤对苄嘧磺隆有很强的吸附性,且随供试土壤理化性质的差异其吸附性呈明显变化．苄嘧磺隆在土壤中的吸附符合Fruendlich方程,其在土壤中的吸附常数Kf与土壤有机质、粘粒含量呈显著正相关(r＝0．7393*和0．7751*,p＜0．05),与土壤pH呈显著负相关(r＝0．7068*,p＜0．05)．苄嘧磺隆在土壤上的吸附自由能为11．45—13．38KJ／mol,表明苄嘧磺隆在土壤中的吸附以物理作用为主。     

土壤和叶际微生物对啶虫脒的降解作用

深入研究了土壤、叶际原位和叶际可培养微生物对啶虫脒的降解作用及各条件下降解效果的差异.结果表明,不同环境下的微生物对啶虫脒有不同程度的降解效果.原位叶际微生物对啶虫脒降解影响的程度较小,在灭菌处理与对照叶面中啶虫脒的半衰期分别为8 1 d和6 6d.相对而言,土壤和叶际分离培养微生物对啶虫脒降解作用更加显著,在自然土壤和灭菌土壤中啶虫脒的降解半衰期分别为5.0 d和39.6d,相差为8倍;和原位叶际微生物相比,在油菜叶培养基中微生物的生物量大幅度提高,同时,对啶虫脒的降解效果也更加显著;在灭菌处理的豆叶培养基中(CK),啶虫脒42d的降解率为16.5%,相同时间内非灭菌处理的叶际分离微生物降解率高达95%,其降解速率与培养基中的微生物量呈正相关性,叶际和土壤中都存在能降解啶虫脒的微生物.     

聚-γ-谷氨酸在环境中降解特性的初步研究

通过液相色谱分析聚-γ-谷氨酸(γ-PGA)在环境水样和土样中的降解率,以及降解产物谷氨酸的生成量,研究γ-PGA在环境中的降解特性。研究表明:γ-PGA在环境水样中的降解较慢,10d后,0.5%γ-PGA在鱼塘水样中仅降解了1.6%,谷氨酸的含量也仅为120mg/kg。γ-PGA在环境土样中降解明显,γ-PGA在土壤中放置20d,仅保存了7.6%,而谷氨酸含量达到了3.2mg/g土样。γ-PGA在灭菌土壤中降解的半衰期是未灭菌土壤的3.7倍,这说明γ-PGA在环境土样中的降解主要是微生物的作用。从土壤中分离的γ-PGA生产菌株B. subtilis CCTCC202048能降解γ-PGA,通过PCR扩增从该菌株中得到了γ-PGA降解酶基因。该研究将为γ-PGA在环境中的使用奠定理论基础。     

Residue analysis and dissipation of monosulfuron in soil and wheat

HPLC-UV residue analytical method for monosulfuron [ N-[( 4‘-methyl ) pyrimidin-2‘-yl ]-2-nitrophenylsulfonyl urea] in soil and wheat was developed. Monosulfuron residues were recovered by solvent extraction, followed by liquid-liquid partition, and C18 cartrige clean-up. Excellent method recoveries ranging from 95%-104% for both fortified soil and wheat grain were obtained with coefficients of variation 1.5%-11.8%. The minimum detectable quantities in soil and wheat were both 4 ng, the limit of detection was 0.02 mg/kg. When monosulfuron was applied according to double dosage of maximum recommended use direction(120 g ai/hm^2 of 10% monosulfuron wettable powder sprayed for once during development of wheat ) in field studies conducted in Shandong Province and near Beijing, monosulfuron residues was not detected in soil and wheat samples collected 75 d after application. Laboratory soil degradation studies showed that monosulfuron degraded faster in acidic soil and strong alkaline soil than in neutral or weak alkaline soil. Half lives in Jiangxi soil, Shijiazhuang soil, Jiangsu soil and Heilongjiang soil were 41, 48, 87 and 84 d respectively. Monosulfuron residues dissipated rapidly in Shandong and Beijing field test sites with half-lives of less than 14 d.     

Effects of combination of plant and microorganism on degradation of simazine in soil

The degradative characteristics of simazine （SIM）, microbial biomass carbon, plate counts of heterotrophic bacteria and most probably number （MPN） of SIM degraders in uninoculated non-rhizosphere soil, uninoculated rhizosphere soil, inoculated non- rhizosphere soil, and inoculated rhizosphere soil were measured. At the initial concentration of 20 mg SIM/kg soil, the half-lives of SIM in the four treated soils were measured to be 73.0, 52.9, 16.9, and 7.8 d, respectively, and corresponding kinetic data fitted first-order kinetics. The experimental results indicated that higher degradation rates of SIM were observed in rhizosphere soils, especially in inoculated rhizosphere soil. The degradative characteristics of SIM were closely related to microbial process. Vegetation could enhance the magnitude of rhizosphere microbial communities, microbial biomass content, and heterotrophic bacterial community, but did little to influence those community components responsible for SIM degradation. This suggested that rhizosphere soil inoculated with microorganisms-degrading target herbicides was a useful pathway to achieve rapid degradation of the herbicides in soil.     

乙氧氟草醚在模拟稻田-鱼塘生态系统中残留动态的研究

在野外稻田-鱼塘模拟系统研究了乙氧氟草醚以规定剂量72g/hm2施用于田间后的残留分布及消解动态?结果表明,施药后4h该药在稻田表水和鱼沟中的浓度分别为29.4和19.6μg/L,在稻田土?鱼塘水和塘泥中的最大浓度分别为0.752,0.006和0.156mg/L?且在各介质中消解迅速,在田表水?塘水?田土中的半衰期分别为4.5,48.8h和7.2d?说明该药对水生生物虽有较高毒性,但在规定使用剂量下,其在稻田及邻近鱼塘中的残留浓度与毒性已降到对其中的水生生物不再有危害的水平?因此可认为该农药在稻田使用对水生生物无实际危害作用?      

Degradation of 14C-glyphosate and aminomethylphosphonic acid (AMPA) in three agricultural soils

Glyphosate (N-phosphonomethyl glycine) is the most used herbicide worldwide. The degradation of 14C-labeled glyphosate was studied under controlled laboratory conditions in three di erent agricultural soils: a silt clay loam, a clay loam and a sandy loam soil. The kinetic and intensity of glyphosate degradation varied considerably over time within the same soil and among di erent types of soil. Our results demonstrated that the mineralization rate of glyphosate was high at the beginning of incubation and then decreased with time until the end of the experiment. The same kinetic was observed for the water extractable residues. The degradation of glyphosate was rapid in the soil with low adsorption capacity (clay loam soil) with a short half-life of 4 days. However, the persistence of glyphosate in high adsorption capacity soils increased, with half-live of 19 days for silt clay loam soil and 14.5 days for sandy loam soil. HPLC analyses showed that the main metabolite of glyphosate, aminomethylphosphonic acid (AMPA) was detected after three days of incubation in the extracts of all three soils. Our results suggested that the possibility of contamination of groundwater by glyphosate was high on a long-term period in soils with high adsorption capacity and low degrading activities and/or acid similar to sandy loam soil. This risk might be faster but less sustainable in soil with low adsorption capacity and high degrading activity like the clay loam soil. However, the release of non-extractable residues may increase the risk of contamination of groundwater regardless of the type of soil.     

Imazaquin degradation and metabolism in a sandy loam soil amended with farm litters

Irnazaquin applied in legume crops has a long residual time in soil, which often impacts safety of the susceptible crops. To increase safety of imazaquin application, two composted litters, bovine manure （BM） and chicken manure （CM）, were used to determine their effects on imazaquin environmental behavior by incorporating each kind of manure into the tested sandy loam soil at 10% （w/w）. The degradation of imazaquin in BM- and CM-amended soil was about 2.4 and 1.5 times, respectively, faster than that in unamended soil. The half-lives of imazaquin in BM-amended soil varied between 6.7 and 15.4 d over the temperature range of 20 to 40℃, and the degradation rate constant （k） increased by a factor of about 1.5 for every 10℃ change. Higher mix ratio did not significantly increase the degradation, and the optimal active degradation of imazaquin was observed approximately at the mix ratio of 10：1 of soil to BM. The different moisture levels had negligible effect on imazaquin degradation. In both unamended and BM-amended treatments, two metabolites were observed at 5, 10 and 30 d after treatment. One metabolite at retention time （RT） of 8.4 rain was identified as 2-（4- hydroxyl-5-oxo-2-imidazolin-2-yl） quinoline acid, originating from the loss of isopropyl group and hydroxylation at the 4-position of imidazolinone ring. The other at RT of 12.9 rain was identified as quinoline-2,3-dicarboxylic anhydride, resulting from detachment of imidazolinone ring and the forming of dicarboxylic anhydride. This finding suggested that the addition of farm litters into soil might be a good management option since it can not only increase soil fertility but also contribute to increase safety of imazaquin application to the following susceptible crops.     

生物炭影响抗生素在土壤中环境行为的Meta分析

生物炭作为一种减污降碳相协同的土壤改良剂,在抗生素污染控制方面均有较大应用前景.为了系统研究生物炭施用对抗生素在土壤中环境行为的影响,对2011～2021年发表的20篇文献进行Meta分析.结果表明,抗生素在生物炭改良土壤中的吸附、降解行为受生物炭施用量与性质的显著影响.施用质量分数为2%时,对抗生素吸附行为的影响最强,效应值为0.19;施用质量分数为5%时,对其降解作用影响显著,效应值为0.23;生物炭比表面积、极性、稳定性和芳香化程度对分配系数的增加影响非常显著,分别为0.11、0.13、0.09和0.18;而生物炭施用量和性质对抗生素迁移行为影响并不显著.生物炭还可通过调控土壤环境间接影响抗生素环境行为.但抗生素在土壤中多环境行为耦合对生物炭的响应机制仍不明确,生物炭田间施用的长效性与负面效应仍缺乏基础数据支撑.     

Combined effects of two sulfonylurea herbicides on soil microbial biomass and N-mineralization

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毫米级根际微域磺胺嘧啶的降解动态研究

采用特制根际箱,研究了玉米根际效应作用下磺胺嘧啶在土壤中的降解动态.在空间上将根-土界面(0~5 mm)细化到1 mm,箱内磺胺嘧啶剂量分别设为1 mg·kg-1和5 mg·kg-1,分别在出苗后第20、40和60 d取样,并将磺胺嘧啶降解率与根-土界面4种有机酸含量进行回归分析,从而得出影响磺胺嘧啶在根际土壤降解的关键因素.结果表明,种植作物可有效促进磺胺嘧啶的降解,且磺胺嘧啶的最大消减水平发生在距离根室3 mm的近根区,降解顺序依次为:近根际根室远根际.通过对不同剂量磺胺嘧啶胁迫下有机酸响应的相关分析发现,苹果酸和乙酸是影响磺胺嘧啶在根际土壤中降解的关键因素之一.     

四环素类抗生素对土壤-生菜系统的生物效应及其迁移降解特性

四环素类抗生素（TCs）会随畜禽粪便的施用而残留在农田土壤,对蔬菜生长和土壤生态带来风险.本文通过温室土壤盆栽试验,外源添加3种不同水平的土霉素（OTC）、四环素（TC）和金霉素（CTC）,研究了TCs对生菜的生理毒性和在生菜中的吸收转运特性,同时研究了TCs在土壤中的降解和对土壤酶活性以及土壤微生物数量的影响.结果表明,OTC、TC和CTC降低了生菜的生物量,减少了叶绿素a、叶绿素b和类胡萝卜素的含量,抑制了净光合速率,提高了SOD、POD和CAT活性;生菜对TCs的吸收量根系>地上部分,随土壤施加的TCs增加吸收量增加,而生物富集系数和转运系数降低;通过人体预测每日摄入量（EDI）和人体每日允许摄入量（ADI）的比值计算TCs暴露引起的人体健康潜在风险值（HQ）,当土壤中OTC、TC和CTC含量低于150 mg·kg^-1时,生菜可食部位的健康风险较低（HQ<0.1）;TCs在不同土壤中的降解速率：对照土 > 根际土 > 非根际土,OTC在土壤中的降解速率显著低于TC和CTC;高含量的TCs（150~1350 mg·kg^-1）处理显著抑制土壤脲酶和根际土的过氧化氢酶活性,减少土壤细菌和真菌的数量.     

Effect of copper on the degradation of pesticides cypermethrin and cyhalothrin

The influence of coexisting copper (Cu) ion on the degradation of pesticides pyrethroid cypermethrin and cyhalothrin in soil and photodegradation in water system were studied.Serial concentrations of the pesticides with the addition of copper ion were spiked in the soil and incubated for a regular period of time,the analysis of the extracts from the soil was carried out using gas chromatography (GC).The photodegradation of pyrethroids in water system was conducted under UV irradiation.The effect of Cu~(2 ) on the pesticides degradation was measured with half life (t_(0.5)) of degradation.It was found that a negative correlation between the degradation of the pyrethroid pesticides in soil and Cu addition was observed.But Cu~(2 ) could accelerate photodegradation of the pyrethroids in water.The t_(0.5) for cyhalothrin extended from 6.7 to 6.8 d while for cypermethrin extended from 8.1 to 10.9 d with the presence of copper ion in soil.As for photodegradation,t_(0.5) for cyhalothrin reduced from 173.3 to 115.5 rain and for cypermethrin from 115.5 to 99.0 min.The results suggested that copper influenced the degradation of the pesticides in soil by affecting the activity of microorganisms.However, it had catalyst tendency for photodegradation in water system.The difference for the degradation efficiency of pyrethroid isomers in soil was also observed.Copper could obviously accelerate the degradation of some special isomers.     

Residual dynamics of thiacloprid in medical herbs marjoram, thyme, and camomile and in soil

Thiacloprid is a new insecticide of the chloronicotinyl family. To assess its risk after application, residual characteristics of thiacloprid in marjoram, thyme, and camomile and in soil were studied under field conditions. The active ingredient was extracted from the plant material using a mixture of acetone-water. After filtration, the extract was concentrated to the aqueous phase, diluted with water, and portioned against ethyl acetate on a matrix solid phase dispersion column. Thiacloprid was extracted from soil using a mixture of methanol-water, filtered, and re.extracted （clean up） with dichloromethane. The residues were quantified using HPLC-MS-MS. The methods were validated by recovery experiments. Thiacloprid residues in marjoram, thyme, and camomile and in soil persisted beyond 10, 14, 14, and 21 d but no residues were detected after 14, 21, 21, and 28 d, respectively. The data obtained in this study indicated that the biexponential model is more suitable than the first-order function to describe the decline of thiacloprid in fresh marjoram, fresh thyme, and dried camomile flowers with half-life （t1/2） of 1.1, 0.7, and 1.2 d, respectively. However, both the first-order function and biexponential model were found to be applicable for dissipation of thiacloprid in soil with almost the same t1/2 values of 3.5 and 3.6 d. The results indicated that thiacloprid dissipates rapidly and does not accumulate in the tested herbs and in soil.     

土壤及铝氧化物吸附氯磺隆和苄嘧磺隆动力学研究

用间歇法研究了红壤和人工合成的铝氧化物吸附除草剂(氯磺隆、苄嘧磺隆)的动力学特性。结果表明:土壤和氧化物对除草剂的吸附均在较短的时间内达到平衡。用五种模型对土壤和氧化物的吸附动力学过程进行了描述,其中最优模型是一级动力学方程。两种除草剂在两种供试样品中的吸附量均有差别。