黑土环境中乙草胺的微生物降解特征研究

通过室内恒温(25℃)避光培养试验,研究了黑土环境中乙草胺的微生物降解特征。在适宜水分条件下,将土壤样品分别进行常规、灭菌、选择性抑菌剂加入等处理后培养并测定土壤乙草胺含量和土壤微生物量。结果显示:在灭菌土壤中乙草胺的残留量较未灭菌土壤显著增加,未灭菌土壤中乙草胺残留数量与微生物量变化密切相关,表明微生物活性是影响乙草胺降解的主要因素。适当的水分有益于土壤中微生物生长,从而促进了土壤中乙草胺的降解。加入青链霉素后乙草胺残留量远大于放线菌酮和常规培养,表明细菌比真菌具有更强的降解乙草胺的能力。随着乙草胺的施药量增加,初期微生物量显著降低,是导致乙草胺总降解率下降的主要原因。     

黑土中乙草胺残留和微生物变化的时间特征研究

通过黑土室外盆栽试验,研究了种植玉米和未种植条件下乙草胺在玉米生长苗期的残留变化规律及土壤微生物量碳的动态特征。研究表明:乙草胺在土壤中半衰期较短,土壤微生物活性是影响其降解的主要因素。但是,由于施用化肥极大地刺激了微生物活性,因而,乙草胺施用对土壤微生物量碳影响并不显著。然而,玉米的种植对土壤微生物量和土壤乙草胺残留数量有着显著的影响。种植玉米条件下土壤微生物量碳显著增加,同时,土壤中乙草胺残留量降低,说明种植玉米有助于微生物活性的提高和乙草胺生物毒害性的降低。     

土壤含水量和胡敏酸对有机氯农药降解的影响

尽管我国从1983年就开始禁用有机氯农药，但环境中仍有大量残留存在。土壤中污染物的残留是吸附、降解和迁移等各种理化作用和生物作用的综合结果，其中降解是制约其残留量的关键过程。大量研究表明，影响土壤中农药降解的主要环境因素包括土壤有机质、土壤温度、土壤pH和土壤含水量等，因为这些因素显著影响着土壤微生物的数量和活性。微生物代谢所需的营养物质有一部分来自农药和土壤有机质，土壤中微生物对其降解起着重要作用。胡敏酸（HA）是土壤有机质的主要组分，因此以HA代表土壤有机质对农药降解的影响是合理的，也有很多关于HA对农药在土壤中吸附等环境行为影响的研究报道。     

乙草胺在四种不同土壤中吸附行为研究

通过平衡振荡法测定了乙草胺在四种土壤中的吸附等温线,从影响因素、能量变化等方面研究了乙草胺在4种土壤中的吸附。结果表明:乙草胺易于被各种土壤吸附,土壤的吸附规律能够较好的符合Freundlich方程,拟合方程均有良好的线性关系。微生物的作用并没有显著改变乙草胺的吸附规律,乙草胺的吸附受到土壤有机质和矿物组成的显著影响。     

一株乙草胺降解菌株M-3的分离鉴定及其代谢途径的初步研究

乙草胺是一种广谱、高效的酰胺类除草剂,由于乙草胺具有较长的降解周期,还有不易挥发、不易光解、易残留的特点,如果过量、频繁使用,对人、动植物均有一定的毒害作用。为了探讨乙草胺的微生物降解机理,本研究从长期受乙草胺污染的土壤中分离到一株能降解乙草胺的菌株M-3,该菌株能以乙草胺为唯一碳源生长。通过菌落表型、生理生化特征和菌株16SrRNA基因序列的相似性分析,将其鉴定为寡养单胞菌属(Stenotrophomonas sp.)。在室内条件下,运用HPLC和HPLC-MS分析方法,研究了菌株M-3对乙草胺的降解特性,并对其代谢途径做了初步的研究。结果表明,菌株M-3在5d内对浓度为50mg/L的乙草胺的降解率可达76.6%。M-3降解乙草胺的最适温度和最适pH值分别为30℃和7.0。在对代谢产物结果进行分析的基础上推测了M-3降解乙草胺的途径,将产物鉴定为2-乙基-6-甲基-2-氯乙酰苯胺。该研究为乙草胺污染的生物修复提供了理论依据。     

水热条件和施肥对黑土中微生物群落代谢特征的影响

选择位于我国东部3个不同气候带(温带、暖温带、中亚热带)的农业生态试验站(海伦站、封丘站、鹰潭站),设置水热变化梯度下的土壤置换试验,利用Biolog方法,研究了水热因子和施肥对单作玉米的黑土中微生物群落的影响。结果表明,在3种气候条件下,施用NPK肥均提高了黑土中细菌群落的碳源代谢活性(Average well color development,AWCD值表示)。在玉米抽雄期,施肥处理(NPK)黑土中AWCD值大小顺序为:鹰潭站(中亚热带)>海伦站(温带)>封丘站(暖温带),不施肥(CK)处理为:鹰潭站(中亚热带)>封丘站(暖温带)>海伦站(温带)。说明不施肥时黑土中微生物代谢活性随月均温度的提高而增加,而施肥和降水影响了温度对黑土中微生物代谢活性的作用。主成分分析表明,黑土中微生物群落代谢特征在海伦站(温带)和封丘站(暖温带)之间变化较小,而在鹰潭站(中亚热带)黑土中微生物群落的代谢指纹发生明显改变。气候条件变化导致的黑土中微生物代谢碳源的分异主要表现在:α-丁酮酸、腐胺、D,L-α-甘油、L-苏氨酸(r>0.9);而施肥导致的黑土中微生物代谢碳源的分异主要表现为:β-甲基-D-葡萄糖苷、葡萄糖-1-磷酸盐和丙酮酸甲脂。总体上,不同气候带水热条件的变化和施肥均影响了黑土中微生物群落的代谢活性和代谢特征的变化。     

气候条件和作物对黑土和潮土固氮微生物群落多样性的影响

固氮微生物是土壤氮素的主要贡献者之一。利用在黑龙江海伦(寒温带)、河南封丘(暖温带)和江西鹰潭(中亚热带)设置的2种农田土壤(黑土、潮土)的置换试验,研究了不同气候、土壤和种植条件对固氮微生物多样性的影响。通过直接从土壤中提取DNA,对固氮酶基因nifH PCR扩增并进行DGGE电泳的分析方法研究了2种类型土壤在3种不同水热条件下固氮微生物群落多样性的变化特征。研究结果表明,在置换到不同气候条件下3年后,土壤类型是决定固氮微生物结构及多样性的主要影响因子,其次是短期气候条件变化的影响,最后是种植玉米的影响。土壤固氮微生物多样性、优势度与土壤C/N及碱解氮含量呈显著正相关(p<0.01),与pH呈显著负相关;多元回归分析及典范对应分析均表明土壤碱解氮含量是影响固氮微生物多样性的决定因素。水热条件与土壤固氮微生物多样性没有线性相关关系,暖温带条件下黑土固氮微生物多样性最高,而潮土最低。种植玉米提高了土壤固氮微生物多样性。     

秸秆源性碳在黑土和褐土中的转运及其对氮肥的响应

采用室内培养结合同位素13C标记技术,探讨了添加小麦秸秆和氮肥后黑土和褐土的碳素矿化特征,分析了土壤原有碳（Cs）和秸秆源性碳（Cstr）在土壤不同有机碳组分（轻组、闭蓄态组分、重组）中的转运特征。结果表明：土壤培养过程是碳矿化损失的过程,施氮肥对黑土和褐土中碳矿化均有一定的抑制效应,褐土中该抑制效应在施秸秆时较不施秸秆时更显著。土壤有机碳组分中Cs损失率表现为由高到低依次为重组、闭蓄态组分、轻组,施秸秆使黑土重组Cs损失率由2.83%增加至5.53%（P<0.05）,使褐土闭蓄态组分中Cs损失率由1.86%减少至0.82%（P<0.01）。随培养时间的进行,土壤轻组中Cstr经降解逐渐向闭蓄态组分和重组中转移,180 d后转移缓慢;至培养结束（300 d）时,Cstr总残留率在黑土与褐土之间无显著差异,轻组中Cstr残留率为褐土（4.98%～8.52%）显著高于黑土（1.71%～2.47%）。与不施氮相比,施氮处理使褐土轻组的Cstr残留率增加了近一倍。综上,施氮肥对黑土和褐土中碳矿化均有一定的抑制效应,重组是土壤碳损失的主要来源,添加秸秆对黑土重组的碳矿化有激发效应,而对褐土闭蓄态组分的碳矿化有抑制作用。褐土轻组中外源秸秆的降解程度低于黑土,并且施氮肥抑制其降解。     

乙草胺降解菌株Rhodococcus sp.AC-1的分离及降解特性研究

为解决乙草胺残留问题,采用连续传代富集培养的方法,从长期生产乙草胺的农药厂污染土壤中分离筛选到1株乙草胺降解菌株AC-1。经过形态学特征、生理生化特征和16S rRNA基因序列系统发育分析,菌株AC-1被鉴定为红球菌属(Rhodococcus)。菌株AC-1在48h内能将0.2 m M的乙草胺完全降解,但不能矿化乙草胺。借助LC-MS,确定乙草胺降解终产物为2-氯-N-(2-乙基-6-甲基苯基)乙酰胺(CMEPA)。菌株AC-1降解乙草胺的最适温度为30℃,最适p H值为7.5。0.1 m M的Cu2+和Hg2+对菌株AC-1降解乙草胺具有很强的抑制作用,而0.1 m M的Fe2+则对菌株AC-1降解乙草胺具有微弱的促进作用。菌株AC-1对乙草胺的降解效果与起始接种量呈正相关。菌株AC-1对甲草胺和丁草胺表现出良好的降解效果,但对异丙甲草胺的降解能力非常微弱。土壤降解试验表明,投加菌株AC-1可以明显促进土壤中乙草胺的降解。本研究为乙草胺的有效降解提供了数据和技术支持。     

再生水灌溉对4类土壤Cd生物有效性的影响

根据国家土壤环境质量标准,选取重金属Cd含量为二级水平的4类土壤（红壤、 潮土、 土、 黑土）进行土培试验,研究再生水灌溉与小白菜生物量及Cd含量、 土壤有效态Cd含量、 pH、 微生物群落的关系,以及不同类型土壤间的差异性。结果表明, 再生水灌溉在不同类型土壤上对小白菜生物量及Cd含量、 土壤有效态Cd含量、 土壤pH和微生物数量的影响不同: 1）红壤、 潮土、 土上小白菜生物量增加显著,分别增加9.09%、 16.08%、 9.92%,黑土上增加不显著; 2）小白菜Cd含量在红壤上显著降低,由对照的0.29 mg/kg降低到0.22 mg/kg,在黑土上比对照增加了18.75%,在潮土和土上影响不大; 3）有效态Cd含量在红壤没有变化,但在潮土、 土、 黑土上增加显著; 4） 4类土壤微生物数量增加显著; 5）潮土、 土、 黑土的pH值有所降低。     

Environmental distribution of acetochlor, atrazine, chlorpyrifos, and propisochlor under field conditions

The environmental behavior, movement, distribution, persistence, and runoff by rainfall of the pesticides acetochlor, atrazine, chlorpyrifos, and propisochlor were studied under field conditions during a five-month period at normal weather conditions. The pesticide concentrations in soil depths of 0-5 and 5-20 cm, and in sediment and runoff water samples (collected from an artificial reservoir built in the lower part of the experimental plot) were measured every second week and following every runoff event. The contamination of a stream running across the lowest part of the plot was also monitored. The weather conditions were also recorded at the experimental site. The pesticide residues were quantified by a capillary gas chromatograph equipped with a nitrogen phosphorus selective detector (GC-NPD). There was a consistent decrease in pesticide residues in the 0-5 cm soil layer with time after spaying. At 140 days after treatment only atrazine and chlorpyrifos were present; acetochlor and propisochlor were not detected in this soil layer. Atrazine and chlorpyrifos in the soil at a depth of 5-20 cm were detectable during the whole experimental interval, whereas acetochlor and propisochlor concentrations were below the limit of detection. Pesticide losses by the surface runoff process and the contamination of the stream were closely related to the time of rainfall elapsed after treatment and amount of rain at the experimental plots. Losses were primarily dependent on surface rainfall volume and intensity. The maximum detected residues of atrazine and acetochlor in stream water were 1 order of magnitude higher than the maximum residue limit specified by the European Union (EU) for environmental and drinking water (0.1 microg/L for individual compounds and 0.5 microg/L for total pesticides). Chlorpyrifos and propisochlor were not detected in this matrix.     

Activity,Adsorption, and Lixiviation of Acetochlor in Soil under No Tillage and Conventional Tillage: Influence of Straw Coverage

Abstract

The activity of residual herbicides employed for weed control varies with adsorption, lixiviation, degradation, and biological transformation of these compounds in the soil. The purpose of this study was to evaluate the activity of the herbicide acetochlor (2‐chloro‐N‐ethoxymethyl‐6′‐ethylacet‐o‐toluidine) in Typic Paleodult under no tillage and conventional tillage. Field and laboratory experiments were carried out at the Universidade Federal do Rio Grande do Sul. Weed control with and without straw coverage, and adsorption and lixiviation of acetochlor, in soil with both tillage systems were evaluated. Adsorption and lixiviation processes were determined by high‐performance liquid chromatography (HPLC) with UV detector. The coefficients K _d and K _oc were higher in no‐tillage soil, indicating a more effective acetochlor adsorption. The maximum concentration of acetochlor was found in a depth of 15–20 cm, indicating a higher lixiviation in this soil. The acetochlor was more effective in weed control using conventional tillage when compared to no tillage. The straw coverage reduced the control efficiency of the herbicide.     

乙草胺对土壤微生物数量和酶活性的影响

采用室内瓶培养试验,研究了乙草胺施用对土壤微生物数量及酶活性的影响。结果表明:乙草胺施用初期对土壤细菌和放线菌数量有明显刺激作用,但施用30d时高施用量处理(30mg·kg-1)呈明显抑制作用,之后各处理放线菌恢复到对照水平,而对细菌的抑制作用一直持续到60d;乙草胺对土壤真菌数量呈"抑制-恢复-刺激"的作用趋势。乙草胺施用初期对土壤脱氢酶产生一定刺激作用,45d后高施用量处理呈明显抑制作用,一直持续到60d;土壤过氧化氢酶对乙草胺不敏感,而转化酶和脲酶对乙草胺施入初期较敏感;低施用量处理对转化酶有抑制作用,高施用量处理对转化酶有刺激作用,各处理对脲酶都有抑制作用。     

乙草胺对农田中小型土壤动物群落结构的影响

采用定点试验的方法,在哈尔滨市呼兰区选择典型农田生态系统进行试验,研究施用不同浓度乙草胺对农田中小型土壤动物群落组成、多样性及垂直分布的影响。本调查共获中小型土壤动物4 648只,隶属于2门4纲10目15个类群,其中甲螨亚目和中气门亚目为优势类群。研究结果表明,施用不同浓度的乙草胺对农田中小型土壤动物群落组成、多样性及垂直分布均产生一定影响。Sorenson相似性系数和Morisita-Hron相似性系数均表现为高浓度与中浓度差异高浓度与低浓度差异高浓度与对照差异,表明随乙草胺浓度的增加土壤动物的群落结构差异逐渐显著;除优势度指数外,其余多样性指数均表现为中浓度和低浓度样地与对照样地存在显著差异(P0.05),高浓度样地与对照样地间存在极显著差异(P0.001)。5月、7月和9月土壤动物的密度在0~5 cm土层中均表现为对照样地低浓度样地中浓度样地高浓度样地,而在其下部的各土层中土壤动物密度变化与乙草胺浓度变化无明显相关性。中小型土壤动物可以作为揭示施用乙草胺过程中土壤质量变化的生物学指标。其群落组成、多样性和垂直分布的变化表明,中小型土壤群落对乙草胺的不同施用浓度产生了响应,过高浓度乙草胺会对土壤生态系统产生干扰,对土壤环境造成威胁。     

乙草胺、甲胺磷及其复合污染对黑土土壤真菌的影响

Using plate counting and ergosterol assay, single and joint effects of acetochlor and methamidophos on the dynamics of soil fungal population and total fungal biomass in the black soil zone of Northeast China were investigated. The results demonstrated that acetochlor at high concentration levels （150 and 250 mg kg^-1） had an acute and mostly chronic toxicity on both the soil fungal population and total fungal biomass, but at a low concentration （50 mg kg^-1） generally had a stimulating effect that was stronger with total fungal biomass than with the soil fungal population. Methamidophos at a high concentration level （250 mg kg^-1） alone and almost all of its combinations with various dosages of acetochlor increased the soil fungal population, whereas at most sampling dates with 250 mg methamidophos kg^-1 soil, total fungal biomass increased, but in combination with acetochlor it was decreased in the early period of incubation and then increased 28 days after incubation. Thus, through measuring the number of colony forming unit of the soil fungal population along with the total fungal biomass, a better understanding on effects of agrochemicals on soil fungi could be made.     

Discriminating multiple impacts of biogas residues amendment in selectively decontaminating chloroacetanilide herbicides

There is increasing concern about modifications to pesticide persistence in soil from the application of organic wastes as fertilizers. This study was conducted to discriminate the multiple effects of biogas residues (BR) amendment, including soil nutrients, soil microbial activity and biodiversity, and adsorption and degradation of chloroacetanilide herbicides (acetochlor, metolachlor, and butachlor). Addition of BR to soil increased the release of organic materials (i.e., dissolved organic carbon, dissolved organic nitrogen, and active phosphorus). It not only stimulated soil microorganisms and caused changes to microorganism diversity but also increased herbicide adsorption. Such multiple effects led to selective decontamination of chloroacetanilide herbicides, depending on herbicide structures and BR amendment levels. Stereoselectivity in degradation of acetochlor and metolachlor with biphasic character was magnified by BR amendment, which was well explained by integrating the impacts of BR amendment. Interestingly, BR amendment induced significant accumulation of herbicidally active aS,CS-metolachlor, facilitating the utilization of herbicidal activity.     

不同添加剂对土壤中乙草胺吸附／解吸的影响

采用批处理恒温振荡法,利用气相色谱一质谱联用仪研究了人工添加不同吸附物质对土壤中乙草胺的吸附／解吸作用。结果表明,人工添加不同吸附物质对土壤中乙草胺的吸附强度和吸附容量不同,不同的添加剂对土壤中乙草胺的吸附／解吸作用均呈现明显的非线性关系,可用Freundlich模型描述。并且随着土壤中添加量的增大,吸附强度增大、吸附容量增大、所得吸附等温线的非线性也逐步增大;另外,添加剂对乙草胺的解吸迟滞作用也随添加剂含量的增高而更加明显。但是不同添加剂对土壤中乙草胺的吸附能力有明显差异,其中煤粉的吸附能力最大,其次是壳聚糖,沸石最小。     

Dissipation of [(14)C]acetochlor herbicide under anaerobic aquatic conditions in flooded soil microcosms

Acetochlor degradation was studied under anaerobic conditions representative of conditions in flooded soils. Soil-water microcosms were prepared with a saturated Drummer clay loam and made anaerobic by either glucose pretreatment or N(2) sparging. Sparged microcosms consisted of sulfate-amended, unamended, and gamma-irradiated microcosms. The microcosms were sampled in triplicate at predetermined time intervals during a 371 day incubation period. Volatile, aqueous, extractable, and bound (unextractable) (14)C residues were quantified with liquid scintillation counting and characterized using high-performance liquid radiochromatography (HPLRC) and soil combustion. SO(4)(2)(-), Fe(II), CH(4), and pH were monitored. Complete anaerobic degradation of [(14)C]acetochlor was observed in all viable treatments. The time observed for 50% acetochlor disappearance (DT(50)) was 10 days for iron-reducing and sulfate-reducing conditions (sulfate-amended), 15 days for iron-reducing conditions (unamended), and 16 days for methanogenic conditions (glucose-pretreated). Acetochlor remained after 371 days in the gamma-irradiated microcosms, and metabolites were observed. [(14)C]Metabolites were detected throughout the study. Formation of one of the metabolites correlated with Fe(II) formation (r(2)(), 0.83). A significant portion of the (14)C activity was eventually incorporated into soil-bound residue (30-50% of applied acetochlor) in all treatments.