Anaerobic soil disinfestation:A chemical-independent approach to pre-plant control of plant pathogens

Due to increasing regulations and restrictions, there is an urgent need to develop effective alternatives to chemical-dependent fumigation control of soilborne pests and pathogens. Anaerobic soil disinfestation （ASD） is one such alternative showing great promise for use in the control of soilborne pathogens and pests. This method involves the application of a carbon source, irrigation to field capacity, and covering the soil with a plastic tarp. While the mechanisms of ASD are not completely understood, they appear to be a combination of changes in the soil microbial community composition, production of volatile organic compounds, and the generation of lethal anaerobic conditions. The variety of materials and options for ASD application, including carbon sources, soil temperature, and plastic tarp type, influence the efficacy of pathogen sup- pression and disease control. Currently, both dry （e.g., rice bran） and liquid （e.g., ethanol） carbon sources are commonly used, but with different results depending on environmental conditions. While solarization is not an essential component of ASD, it can enhance efficacy. Understanding the mechanisms that mediate biological changes occurring in the soil during ASD will facilitate our ability to increase ASD efficacy while enhancing its commercial viability.

Quantification and Remediation of Soil Chemical Degradation in Tropical Australia,China and Thailand

Soil and land degradation in the tropics can be identified and described interms of physical, chemical, and biological changes from its pristine state brought about by naturaland anthropogenic influences. A characteristic of these ecosystems is their capacity to recyclenutrients through soil organic matter (SOM). Following disturbance through changed land management,SOM is rapidly mineralized and there is a corresponding decline in fertility and the variable chargecomponent of the cation exchange capacity. As these ecosystems are strongly dependent on SOM fortheir functionality, changed land use can have irreversible impacts on the productivity of thesesystems. The paper focuses on quantifying chemical degradation through 'benchmarking' using datafrom paired sites in tropical China and Thailand using surface charge fingerprinting. Using valuestaken from the fingerprint of an undisturbed soil, an index of chemical degradation from 'ideality'was calculated. Various management strategies that attempt to reverse degradative trends or improvepoor quality soils in their natural condition are discussed, such as the addition of natural claysand silicated materials. Results are present to show the effect of each of the aforementionedstrategies on surface charge characteristics and associated increases in plant productivity.

Petroleum Hydrocarbon Degradation Potential of Soil Bacteria Native to the Yellow River Delta

The bioremediation potential of bacteria indigenous to soils of the Yellow River Delta in China was evaluated as a treatment option for soil remediation. Petroleum hydrocarbon degraders were isolated from contaminated soil samples from the Yellow River Delta. Four microbial communities and eight isolates were obtained. The optimal temperature, salinity, pH, and the ratios of C, N, and P (C:N:P) for the maximum biodegradation of diesel oil, crude oil, n-alkanes, and polyaromatic hydrocarbons by indigenous bacteria were determined, and the kinetics changes in microbial communities were monitored. In general, the mixed microbial consortia demonstrated wider catabolic versatility and faster overall rate of hydrocarbon degradation than individual isolates. Our experimental results demonstrated the feasibility of biodegradation of petroleum hydrocarbon by indigenous bacteria for soil remediation in the Yellow River Delta.

Soil remediation of degraded coastal saline wetlands by irrigation with paper mill effluent and plowing

Combined with anti-waterlogging ditches, irrigation with treated paper mill effluent （TPME） and plowing were applied in this study to investigate the effects of remediation of degraded coastal sa- line-alkaline wetlands. Three treatments were employed, viz., control （CK）, irrigated with 10 cm depth of TPME （I）, and plowing to 20 cm deep before irrigating 10 cm depth ofTPME （IP）. Results show that both I-treatment and IP-treatment could improve soil structure by decreasing bulk density by 5% and 8%. Irrigation with TPME containing low salinity stimulated salts leaching instead of accumulating. With anti-waterlogging ditches, salts were drained out of soil. Irrigation with 10 cm depth of TPME lowered total soluble salts in soil and sodium adsorption ration by 33% and 8%, respective!y, but there was no significant difference compared with CK, indicating that this irrigation rate was not heavy enough to remarkably reduce so!l salinity and sodicity, Thus, in-i： gation rate should be enhanced in order to reach better effects of desalinization and desodication. Irrigation with TPME significantly increased soil organic matter, alkali-hydrolyzable nitrogen and available phosphorus due to the abundant organic matter in TPME. Plowing increased soil air circulation, so as to enhance mineralization of organic matter and lead to the loss of organic matter; however, plowing significantly improvedsoil alkali-hydrolyzable nitrogen and available phosphorus. Improvements of physicochemical properties in I-treatment and IP-treatment both boosted soil microbial population and activity. Microbial biomass carbon increased significantly by 327% （I-treatment） and 451% （IP-treatment）, while soil respiration increased significantly by 316% （I-treatment） and 386% （IP-treatment）. Urease and dehydrogenase activities in both I-treatment and IP-treatment were significantly higher than that in CK. Phosphatase in IP-treatment was significantly higher than that in CK. Compared to I-treatment, IP-treatment improved all of the soil properties except for soil organic matter. The key to remediation of degraded sa- line-alkaline wetlands is to decrease soil salinity and sodicity; thus, irri- gation plus plowing could be an ideal method of soil remediation.

Impact of Anaerobic Soil Disinfestation Treatment on the Properties of Tomato Continuous Cropping Soil

To investigate the impact of anaerobic soil disinfestation(ASD)treatment with different processing duration on tomato continuous cropping soil,a total of eight treatments were designed,which included two treatment temperatures of 10℃ and 30℃,and four treatment times of 3,4,5 and 7 weeks(w).The results showed that whether the temperature was 10℃ or 30℃,the pH values,TOC and available K contents in the soil treated by the ASD method were significantly increased(P<0.05),while the EC values and NO_(3)^(-)contents in soils treated by ASD were significantly reduced compared with the untreated group(P<0.05).The Fusarium oxysporum population in soils treated by ASD decreased with the extension of the treatment time.When the treatment temperature was 30℃,the effect on the removal of the NO_(3)^(-)that had accumulated in soils treated by ASD was significantly better than the treatment temperature of 10℃(P<0.05).When soil was treated by ASD for more than 5 w at 30℃,the NH4+content in soil was significantly increased(P<0.05)compared with the untreated soil.In conclusion,NO_(3)^(-)accumulation in soils could not be completely eliminated with treatment by ASD,even when the treatment time at 10℃ was prolonged.Whether the treatment temperature was 10℃ or 30℃,the F.oxysporum population in soils treated by ASD decreased significantly with the extension of the treatment time to more than 5 w compared with treatment only for only 3 w.

农田土壤中邻苯二甲酸酯降解功能细菌及其应用

本文综述了我国农田土壤PAEs污染特征,重点概述了PAEs降解功能菌株筛选、菌群构建及其应用策略.详细分析了细菌介导的PAEs降解的水解和开环裂解两个途径及参与其中的关键功能基因和酶,讨论了PAEs降解功能细菌在污染土壤中的应用、影响因素及可能存在的问题,并对该技术在消减农田土壤PAEs污染中的应用进行展望,以期为我国PAEs污染农田土壤功能细菌修复及农业生产安全提供理论和技术参考.

温度对厌氧土壤消毒处理效果的影响

为探讨温度对厌氧土壤消毒处理消除连作障碍因子的影响,以番茄连作土壤为研究对象,设置5个处理:对照、10℃、20℃、30℃和40℃处理,置于生化恒温培养箱内,密封处理3周。结果表明,不同温度ASD处理均可使土壤pH显著升高、EC显著降低,土壤有机碳(TOC)、速效钾含量显著增加,低温(小于10℃)ASD处理不能完全消除土壤累积的NO_(3)^(-),高温(40℃)ASD处理中NH_(4)^(+)含量显著升高;不同温度ASD处理中细菌数量显著增加,高温(40℃)ASD处理中真菌、尖孢镰刀菌数量均显著降低。可见,高温(40℃)ASD处理效果最好,不同温度ASD处理均显著提高土壤TOC、速效钾含量。

假单胞菌YZ32产生物乳化剂及原油降解作用

为了分离出一株产生物乳化剂且能降解原油的菌株,以原油为唯一碳源,筛选出能乳化原油的细菌,再通过调整培养基成分来优化假单胞菌YZ32产生物乳化剂,以乳化指数和乳化剂产量为指标选出最佳的碳源和氮源;用乙醇提取生物乳化剂,再用透析袋纯化,测定乳化剂的糖含量和蛋白质含量,检测乳化剂的乳化活性物质。将乳化剂与7种不同的底物混合后测定乳化指数,考察乳化剂对不同底物的乳化效果。在不同条件下考察生物乳化剂的理化稳定性;通过原油降解实验,用GC-MS对原油组分进行分析,考察菌株对原油的去除率和降解效果。结果表明,分离出的能乳化原油的假单胞菌YZ32,以蔗糖(20 g/L)和谷氨酸钠(7 g/L)为碳源和氮源时,可获得最大的生物乳化剂产量。代谢产物中蛋白含量为64.29%,糖含量为13.89%,乳化活性物质为蛋白类物质。该乳化剂对液体石蜡和甲苯具有较好的乳化效果,在温度为15~80℃、pH值为4~11和矿化度为50~350g/L的条件下,YZ32产生的生物乳化剂都能保持良好的稳定性。原油降解实验表明,YZ32在24 d内对原油的去除率达到60.3%,对原油饱和烃中的C11—C20组分和芳香烃中的菲类具有较好的降解效果。假单胞菌YZ32能产生蛋白类的且稳定性良好的生物乳化剂,对原油具有良好的降解效果,在含油污泥土壤修复中具有巨大的应用潜力。

草甘膦概况及微生物降解研究进展

草甘膦作为一种广泛使用的除草剂,因其高效和低成本的特点在农业生产中得到了广泛应用。然而,这种化学物质的使用也给环境带来了一系列的问题。本研究简述了草甘膦作用机理和毒性等概况,阐明草甘膦对水环境的危害主要在影响水质、水生生物和生态系统等方面,对土壤的危害主要体现在破坏土壤微生物生态、破坏土壤微生物群落的结构和功能、影响土壤酶活性。介绍了生物降解的草甘膦污染土壤修复方式的研究进展,草甘膦污染土壤的修复主要运用微生物降解手段。相比于吸附、光解等非生物降解,微生物降解更环保更高效且更具有前景。最后对草甘膦污染土壤修复的微生物降解方式进行了展望,以期为草甘膦微生物降解技术在草甘膦污染土壤中的应用和改进提供参考。

强还原处理对土壤中常见抗生素及其抗性基因的影响研究

土壤中抗生素长期累积所引发的抗性致病菌富集以及抗性基因(Antibiotic resistance genes,ARGs)的传播扩散,已成为当前备受关注的环境问题。为研究强还原处理(Reductive soil disinfestation,RSD)对土壤中抗生素及其ARGs的影响,以常用且难降解的抗生素四环素、土霉素、磺胺嘧啶和磺胺甲恶唑所构建的质量分数为20 mg·kg^(-1)的抗生素混合污染土壤为研究对象,分别设置以玉米秸秆(2%,RCS)、甘蔗渣(2%,RSR)为有机物料的RSD处理,同时设置不处理对照,于处理第7、14、28天进行破坏性采样,利用高效液相色谱和荧光定量PCR技术分析RSD处理过程中抗生素质量分数及ARGs和可移动遗传元件(Mobile genetic elements,MGEs)丰度的变化。结果表明,RSD处理可有效降解土壤中的四环素类和磺胺类抗生素,处理28 d后磺胺类抗生素的降解率为45.2%-100%,优于四环素类的33.5%-57.2%;RSR处理对四环素和磺胺嘧啶的降解效果优于RCS处理,其降解率可达57.2%-64.8%,而RCS处理对土霉素的降解率可达44.7%;两种RSD处理对磺胺甲恶唑的降解率在14 d时即可达100%。RSD处理后土壤中ARGs绝对丰度显著增加,RCS处理的增加作用强于RSR处理;随处理时间延长,tetM、qacH等基因相对丰度在RSD处理中呈下降趋势,一定程度上表明ARGs增加带来的生态负面效应得到缓解。RSD处理可显著降低IS26基因的相对丰度,表明其能通过消减特定MGEs削弱ARGs水平转移能力。综上,RSD处理可有效降解土壤中四环素类和磺胺类抗生素,具有消减土壤中ARGs并降低其传播风险的潜力。研究结果可为解决土壤抗生素污染问题、降低ARGs扩散风险提供一定的理论与技术支持。

磁性炭基菌球降解土壤阿特拉津性能的研究

本研究通过海藻酸钠包埋磁性生物炭与降解菌DNS32形成磁性炭基菌球(DMBC-P),并将其用于阿特拉津(ATZ)污染土壤的修复,探讨其去除ATZ的效能及促进大豆幼苗生长的能力。研究表明,当海藻酸钠与氯化钙的浓度为2%时,DMBC-P对ATZ的去除能力最强。在DMBC-P投加量为2%、温度为30℃、pH=7.3时,其对水体中ATZ的去除率可达到99.99%;并且在pH为3.3~7.3、温度为10~50℃以及ATZ浓度为30~140 mg·L^(-1)的环境中,DMBC-P对ATZ的去除性能仍然十分优异且其可以被有效回收。盆栽试验结果表明,施用DMBC-P进行修复后,该处理下大豆幼苗的生理指标显著高于空白对照处理,叶绿素a、叶绿素b、类胡萝卜素和总叶绿素含量分别提高79.14%、45.48%、67.87%和110.78%。研究表明,DMBC-P施用于污染土壤中能够实现ATZ的高效去除和材料有效回收,是一种极具潜力的污染土壤修复材料。

脉冲放电等离子体修复绝缘油污染土壤

目的为了探讨绝缘油降解的等离子体工艺参数影响规律和机理,方法利用针板式脉冲放电等离子试验平台,选取峰值电压、含水率、频率等6个参数分析绝缘油处理效果。结果结果表明:影响绝缘油降解率的主要因素依次为峰值电压、含水率、绝缘油初始质量分数、空气流速、频率、处理时间;为实现绝缘油降解,峰值电压应高于10 kV,高电压可促进降解和缩短处理时间,降解率和能量效率最高分别为88.18%,43.71 mg/kJ;适当提升含水率可增加·OH数量,促进降解,但含水率更高时因土壤透气能力降低和团聚增强,限制活性离子传输而抑制降解;绝缘油初始质量分数增加可降低降解率,但质量分数较高时,因土壤内层绝缘油组分无法与高活性物质接触,导致降解量下降;处理前后土壤中绝缘油均以饱和烃为主,低碳烷烃易被降解,随着碳数增加降解率逐渐下降;4环芳香烃降解效果优于2~3环的,但因小分子烃类与苯环高温缩合形成高分子芳香烃,处理后4环以上芳烃含量增加。结论研究结果可为等离子体修复绝缘油污染土壤技术研究提供参考。

加油站场地气相抽提(SVE)拖尾污染物的微生物降解效果研究

针对加油站场地气相抽提(SVE)拖尾污染物组成及其含量,首先利用不同浓度石油烃对活性污泥中石油烃降解微生物进行驯化、富集以及筛选,共分离出7株优质石油烃降解菌;其次利用混合降解菌群进行降解试验,对人工配制模拟石油烃污染土壤(石油烃初始质量分数约1400μg/g)生物降解180 d后,石油烃降解率大于86%;最后,开展混合降解菌对目标加油站真实污染土壤(石油烃初始质量分数1532.3μg/g)降解试验研究,结果表明,微生物混合菌群将真实污染土壤中石油烃质量分数降至342.6μg/g(230 d),满足美国堪萨斯州风险评估标准(非居民用地石油烃质量分数小于450μg/g),降解率可达77.6%。

Treatability studies of naphthalene in soil,water and air with persulfate activated by iron(Ⅱ)

Chemical oxidation was applied to an artificially contaminated soil with naphthalene(NAP).Evaluation of NAP distribution and mass reduction in soil,water and air phases was carried out through mass balance.Evaluation of NAP distribution and mass reduction in soil,water and air phases was carried out through mass balance.The importance of the air phase analysis was emphasized by demonstrating how NAP behaves in a sealed system over a 4 hr reaction period.Design of Experiments method was applied to the following variables:sodium persulfate concentration[SP],ferrous sulfate concentration[FeS04],and pH.The system operated with a prefixed solid to liquid ratio of 1:2.The following conditions resulted in optimum NAP removal[SP]=18.37 g/L,[FeSO4]=4.25 g/L and pH=3.00.At the end of the 4 hr reaction,62%of NAP was degraded.In the soil phase,the chemical oxidation reduced the NAP concentration thus achieving levels which comply with Brazilian and USA environmental legislations.Besides the NAP partitioning view,the monitoring of each phase allowed the variabilities assessment over the process,refining the knowledge of mass reduction.Based on NAP distribution in the system,this study demonstrates the importance of evaluating the presence of semi-volatile and volatile organic compounds in the air phase during remediation,so that there is greater control of the system as to the distribution and presence of the contaminant in the environment.The results highlight the importance of treating the contaminant in all its phases at the contaminated site.

“新农科”背景下本科生创新能力训练——以“土壤中邻苯二甲酸酯降解微生物鉴定实验”为例

“新农科”建设和科技快速发展对本科生的创新能力和实践能力提出了更高要求。为提升农业资源与环境专业本科生的实践创新能力,增强专业自信,本文详细阐述了农田土壤中广泛存在的污染物邻苯二甲酸酯降解微生物原位鉴定方法的优化过程,并将其成功应用于蔬菜基地土壤中邻苯二甲酸二(2-乙基己基)酯降解微生物研究。学生在开展创新训练过程中巩固了多学科理论知识,掌握了相关实验仪器操作和数据分析技能,熟悉了开展科学研究的基本流程,认识到科学前沿与农业生产实践的紧密联系,增强了专业自信和投身“三农”工作的责任感。在该创新实验的基础上已有本科生获得多项大学生创新创业项目资助。

生物炭对退化蔬菜地土壤及其修复过程中N2O产排的影响

高氮投入的设施蔬菜地土壤易发生次生盐渍化、酸化、板结化等土壤退化现象,也会引起地下水污染、N_2O大量排放等环境后果,严重影响了蔬菜农业的可持续发展。强还原土壤灭菌(reductive soil disinfestation,RSD)作为新兴的退化设施蔬菜地土壤修复方法,能够有效缓解土壤退化,但也导致N_2O大量排放。本研究选用生物炭作为调节剂,评估不同生物炭施加量对退化设施蔬菜地土壤及其强还原修复过程中N_2O排放的影响,并测定反硝化功能基因(一氧化氮还原酶基因nor B和氧化亚氮还原酶基因nos Z)丰度来反映反硝化微生物活性。结果显示:RSD法显著降低了土壤硝酸盐含量、提高了土壤p H,缓解了土壤退化,但其N_2O累计排放量是非修复土壤的950倍以上;施加生物炭具有减排效果,其中施加5%的生物炭显著降低了退化设施蔬菜地土壤及其强还原修复过程中的N_2O排放,其减排量分别为68.7%和16.0%;Pearson相关分析显示,非强还原修复过程和强还原修复过程中土壤N_2O排放速率均与p H显著负相关,而在强还原修复过程中土壤N_2O排放速率还与NO_3^--N含量显著正相关;施加生物炭显著改变了土壤nor B和nos Z基因,线性回归分析表明,非强还原修复过程和强还原修复过程中土壤N_2O排放的微生物机理不同,前者显著受nos Z基因丰度影响,而后者显著受nor B基因丰度影响。在退化设施蔬菜地土壤中施加5%生物炭可有效减低退化设施蔬菜地土壤及其强还原修复过程中的N_2O排放。

土壤厌氧还原消毒对尖孢镰刀菌的抑制研究

试验采用土壤淹水同时添加有机物料的方法创造土壤厌氧还原环境,抑制香蕉连作土壤中致病菌尖孢镰刀菌(Fusarium oxysporum,FOC)的数量。结果表明:土壤淹水同时添加玉米秸秆的处理显著增加了土壤p H,降低了土壤氧化还原电位和土壤中NO3–-N的浓度;土壤淹水同时添加玉米秸秆的处理过程中,土壤可培养细菌数量显著增加,土壤中可培养放线菌和真菌数量显著降低;土壤淹水同时添加石灰或玉米秸秆均显著降低了土壤中FOC的数量,其中每千克土添加20 g玉米秸秆的处理中FOC数量下降最多,仅为对照处理FOC数量的2.8%。田间试验结果表明:土壤淹水同时每千克土添加5 g玉米秸秆可以有效降低香蕉枯萎病的发生,防效为69.5%。因此,土壤淹水同时添加有机物料是一种可以防控香蕉枯萎病的高效和环保的方法。

石油降解菌剂的研制及其在石油污染土壤修复中的应用

用液态和固态相结合的方式对包含2种细菌的石油降解菌剂进行培养,牛肉膏、蛋白胨作为液态培养基培养初级种子,然后接种到草炭和麸皮的固态培养基中培养。分析温度、接种量、料水比、草炭与麸皮的比例、培养时间对固态培养的影响。制备的BC-E和BC-I 2种菌剂的活菌量分别达到2.47×1011个/g和3.6×1010个/g。采用研制的菌剂对石油污染土壤进行修复实验,1个月污染土壤中的石油降解率可达到45%。

微生物降解三唑类杀菌剂研究进展

三唑类杀菌剂因具有高效、低毒的特性已在中国得到广泛使用,但同时也因其残留期较长、易污染土壤而备受关注。微生物降解被认为是修复被污染土壤的有效措施。文章从降解三唑类杀菌剂的微生物种类、降解机理及影响微生物降解的因素等方面进行了综述,同时指出,目前有关微生物降解三唑类杀菌剂的研究多数仅限于降解菌的筛选及影响降解的因素分析等方面,对于三唑类杀菌剂的微生物代谢途径、降解过程中起关键作用的酶和基因,以及对手性三唑类杀菌剂的对映体选择性降解机制等机理方面的研究仍较少,相关研究有待进一步加强。

土壤厌氧消毒对青枯病的控制及土壤细菌群落结构的影响

近年来,土壤厌氧消毒(Anaerobic soil disinfestation,ASD)作为一种非化学、环境友好型土壤消毒方法,在缓解连作障碍和防治土传病害方面具有显著效果,但其作用机理尚不完全清楚。本研究设置6个处理,即对照、添加米糠(DRB)、麦麸(DWB)、茶麸(DTB)、秸秆(DRS)和不添加物料(D)5种土壤厌氧消毒处理,分析不同处理对青枯病防控效果、土壤理化性质及土壤细菌群落结构组成及多样性的影响。结果表明,与CK相比,添加4种物料厌氧消毒处理对青枯病的防效均达100%,单纯厌氧处理防效为83.3%,且除了DRB外各厌氧处理均能大幅度促进番茄生长。各ASD能显著提高土壤温度、p H和电导率,降低Eh和土壤青枯菌数量。田间试验表明,与CK相比,ASD的番茄青枯病发病率降低29.4%~42.7%,产量增加2.5倍~4.7倍。利用16S r DNA对土壤测序表明,ASD降低了土壤细菌α多样性指数,不同处理间土壤细菌物种种类、丰富度及多样性均存在显著差异。添加不同有机物料的ASD厚壁菌门(Firmicutes)相对丰度大幅度提高,成为优势群落;该门中的厌氧型细菌梭菌科(Clostridiaceae)、瘤胃菌科(Ruminococcaceae)和耐受性细菌芽孢杆菌科(Bacillaceae)等相对丰度也大幅度提高。本研究表明,土壤厌氧消毒处理显著改变了土壤细菌群落结构组成及多样性,厌氧和耐受型细菌丰度大幅度增加,这可能是ASD防控土传病害青枯病的作用机理之一。