【作者】 文波龙；

【导师】 刘兴土；

【作者基本信息】 中国科学院研究生院(东北地理与农业生态研究所) ， 环境科学， 2012， 博士

【摘要】 农业非点源污染与湿地缺水退化是生态环境面临的两大难题，湿地对农田退水的水资源利用和水质净化是解决该问题的有效途径。研究农田退水中的除草剂残留对湿地系统的影响和污染消减机理，搞清除草剂与湿地各组分的相互关系，解决湿地保护、恢复与净化功能利用中的一些根本性的科学问题及关键技术问题，将为缺水退化的芦苇湿地利用农田退水、湿地生态工程控制农业非点源污染的实用技术提供科学依据。论文在评述土壤-植物系统中的关键微界面过程、阐述磺酰脲类除草剂的环境行为和钠盐的生态效应的基础上，以芦苇湿地为研究对象，围绕盐碱地区的钠盐胁迫下芦苇湿地系统对BSM的耐性和净化效能、BSM在湿地生态系统微界面的消减过程、以及根表铁膜和根分泌物对其的影响等内容，开展了钠盐梯度下BSM在芦苇湿地中的生物地球化学过程的控制模拟研究。主要得到以下成果：实地调查和采样分析结果证明盐碱地灌区水稻田磺酰脲类除草剂的施用会引起农田排水中除草剂的残留，吉林省月亮泡灌区水稻田农田退水中的BSM残留量达到1.68～3.77μg/L。原位控制试验揭示盐碱（Na⁺25mmol/l）芦苇湿地90天对土壤BSM（0.05mg/kg～0.50mg/kg）去除率能达到65%以上，低浓度的BSM去除率更高，净化功能明显。从揭示芦苇湿地对农田退水除草剂的耐性出发，深入探讨了钠盐胁迫下湿地芦苇两种繁殖方式对BSM的响应，开展了BSM对盐碱芦苇湿地土壤生化环境的影响研究。发现芦苇种子的响应与受胁迫时种子膜透性的改变关系较大，种子萌发率、发芽整齐度、发芽速率、活力均受到钠盐（Na⁺50mmol/l）的抑制，BSM（0.05mg/l～0.50mg/l）能够缓解芦苇种子受钠盐的抑制，但缓解作用随着BSM浓度的增加逐渐减弱；芦苇种子幼芽生长受影响较小，低浓度BSM也能缓解钠盐对芦苇的株高、生物量的抑制。同时发现盐碱芦苇湿地土壤微生物量碳、氮均受到BSM的抑制，抑制率在20%以上，BSM能够提高盐碱湿地土壤蔗糖酶活性能力但未达到差异显著水平。整个芦苇湿地生态系统表现出一定耐受性。以芦苇湿地土壤、不同土壤胶体为材料，通过批量平衡试验研究了湿地土壤对BSM的吸附、解吸过程，探讨了湿地土壤对BSM的不可逆吸附能力。发现芦苇沼泽湿地土壤对BSM（0.10～20.0mg/l）吸附率在70%以上，单次解吸后残留率仍能维持在60%以上,残存率随BSM浓度增加而减小并趋于稳定是由吸附率降低和解吸率增加共同作用的结果。DMM模型能够很好的拟合BSM在芦苇湿地土壤上的吸附、解吸过程的热力学等温线，在BSM＞1.0mg/l表现出较好的线性，而在低浓度（≤1.0mg/l）下非线性特征较强；动力学过程上，湿地土壤上对BSM的吸附量、解吸量在短时间内增长剧烈，但120min都能基本平衡。湿地土壤中有机质含量高则吸附量大且不易解吸，提取的土壤胶体比原土壤吸持BSM的能力提高25%以上，是土壤吸附的主要因素，不同土壤胶体类型和表面电荷性状对胶体吸持能力影响较大，吸附量腐植酸、蒙脱石-ca2+胶体＞针铁矿+腐植酸复合胶体＞针铁矿胶体＞蒙脱石-K+＞高岭石胶体，而解吸量相反。同时发现钠盐胁迫抑制湿地土壤对BSM的吸附而促进解吸，在湿地土壤及组分、土壤胶体对BSM的吸附、解吸过程中都有明显体现，且蒙脱石-ca2+胶体受钠盐影响最大。迟滞系数较好的反映了湿地土壤对BSM吸附的不可逆部分，也受钠盐抑制，同时迟滞系数随平衡浓度的增大而减小，是与平衡浓度相关的参数。采用多隔层毫米级根箱法模拟芦苇根际环境，研究了BSM消减行为在芦苇毫米级根际土壤中伴随根系分泌物梯度递减效应的微域响应规律。发现BSM的根际消减存在距离根系不同远近的差异，消减效率总的有近根际>根室>远根际的趋势，在近根际BSM的最佳消减发生在距根室2mm左右，并非根系密集、分泌物较多的根室，近根际微域中适宜的根系分泌物水平能最大诱导和激发加速BSM消减的相关微生物和酶活性；钠盐、BSM双因素下土壤可识别的碳链长度在C12到C20的PLFAs有52种，指示了BSM对微生物群落结构的显著影响，揭示了BSM0.130mg/l、钠盐50mmol/l高复合污染下特有的微生物标记物ISO17:1G、19:0cyclo c11-12、18:2w6c、20:4w6c、18:1w9t Alcohol、16:1w7c、ANTEISO17:1AT9、19:1（w8?） Alcohol等。通过水培模拟，围绕根系分泌物的响应机制，探讨了湿地芦苇对钠盐、BSM诱导下根系低分子分泌物的特异性。发现BSM（2.5mg/l、5.0mg/l、10.0mg/l、50mmol/l）、钠盐胁迫诱导的分泌物未引起环境pH的显著变化，诱导根系增强含碳有机物、总糖、氨基酸等低分子有机物的分泌，且诱导作用随BSM浓度增大而增强。同时钠盐与BSM对湿地芦苇根系分泌总糖和氨基酸存在一定的负交互作用，特别是在诱导根系分泌总糖时这种拮抗作用达到差异显著水平。模拟生成湿生植物特有的根表铁膜，探讨了钠盐对根表铁膜形成的影响以及根表铁膜的存在对芦苇BSM污染响应的可能影响。发现低浓度Fe²⁺（0～20mg/l）促进芦苇生长，在Fe²⁺20mg/l以上会对芦苇生长有抑制作用，同钠盐胁迫对芦苇地下部生长的抑制在Fe²⁺高浓度时还会有协同的显著交互作用。芦苇根表铁膜量主要受环境中Fe²⁺浓度影响，Fe²⁺增加显著增加根表铁膜量，与生物量关系较小，钠盐胁迫诱导的芦苇根系分泌物有促进根表铁膜的形成的可能。根表对BSM的吸附量受根表铁膜量的影响很大，根表铁膜量与BSM的吸附量呈极显著的线性正相关，钠盐胁迫对芦苇根表铁膜吸附BSM的影响主要是通过抑制生物量显示，提高了单位根系干物质的吸附量。更多还原

【Abstract】 Agricultural non-point pollution and wetlands degradation for lack of water are twodifficult problems in ecological environment. An effective way to solve these problems is torestore wetlands with the water resources of farmland drainage and to purify drainage byengineering wetland. However, the effect of herbicide residues from drainage on wetlandsystem and its dissipation process are still not clear. Understanding the behavior of herbicideand its environment risk, which is important to the ecological conservation, restoration andutilization of wetland, requires an assessment of the processes influencing its fate, transport,bioactivity and persistence in wetland. Investigation of the ecological impact andenvironment behavior of herbicide in wetland and the controlling key factors involved arethus necessary and effective.This dissertation is aimed to revealthe ecological impacts of bensulfuron methyl （BSM）, inreed wetland under salt stress, understand the interface behavior of BSM in the soil-watersystem, determining the possibility to supply the dry wetlands by farmland drainage withBSM residues, identifying the potential contributions of soil componts and its colloids toBSM retention, evaluating the dissipation of BSM in the rhizosphere and the correspondingmicrobiological and biochemical resopnses, and analysing the influence of iron plaque androot exudates, to develop strengthening wetland treatment techniques to decrease BSMcontamination. The information derived from this work will contribute to a betterunderstanding the interactions and their impacts on the environmental behavior of organicand inorganic combined contaminants in the flooded soil-plant system. The main experimentand conclusions are as follows:It was proved by field survey and sampling investigation that, the application ofsulfonylurea herbicides in saline and alkali paddy field can cause the problem of herbicidesresidues in gricultural drainage, and the BSM in gricultural drainage was up to1.68³.77μg/L in Yueliangpao irrigation district of Jilin Province. The in-situ test revealed that thepurification function of saline reed wetland to BSM was obvious, and the removal rate of BSM （0.05mg/kg⁰.50mg/kg） by saline reed wetland （Na+25mmol/l） after90days canachieve﹥65%and can be more efficient when the concentration of BSM was lower.Information of the resistance of reed wetland to BSM from drainage under salt stress wasgained by in-situ and laboratory simulated experiments with sexual and asexual reproductionof reeds. The results indicated that the response of reed seeds were closely related to themembrane permeability of seed under stress, the seed germination rate, germination vigor,germination index and vigor index all were inhibited by salt stress （Na+50mmol/l）,meanwhile the BSM （0.05mg/l⁰.50mg/l） can alleviate this inhibition, but the inhibitionfunction weakened gradually along with the increasing BSM concentration; the influence onreed plumule was little, and BSM at low concentration can also alleviate the inhibition reedheight and biomass under salt stress. At the same time, it was discovered that the soilmicrobial biomass carbon and nitrogen were inhibited by BSM, and the inhibition rate wasabove20%, but BSM can improve the invertase activity though it was not significant at0.05level. In general, the entire reed wetland ecosystem showed tolerance to BSM under saltstress, to some extent.The adsorption and desorption of BSM on reed wetland soil and different colloids of puresoil minerals and humic acids were measured to obtained the potential contributions of thesematters to BSM retention in wetland under salt stress.Above70%BSM（0.10～20.0mg/l）canbe adsorbed by reed wetland soil, the residual rate still could maintain﹥60%after singledesorption, and the residual rate increased along with the BSM concentration and tended tobe stable, which was the combined result of the increasing adsorption rate and decreasingdesorption rate. The adsorption and desorption isotherms of BSM by reed wetland soil,predicted accurately by the dual-mode model （DMM）, showed good linearity at BSM>1.0mg/l, but the misalignment characteristic was more obvious at the low concentration（BSM≤1.0mg/l）. In dynamics process, the adsorption and desorption quantity of BSM allincreased sharply in a short time, but both process can be basically balanced after120min. Byremoving organic carbon from the wetland soils with H₂O₂, the adsorption decreased anddesorption increased. The colloid improved adsorption rate by>25%, which extracted fromthe original soil, played an important role in the process of BSM adsorption. The adsorptionaffinity for BSM by different colloids was in the order: humic acid colloid,montmorillonite-ca²⁺colloid>goethite+humic acid compound colloid> goethite colloid>montmorillonite-K+colloid> kaolinite colloid, but the desorption affinity was completelyopposite. It was also discovered that the salt stress inhibited adsorption and promoted desorption of BSM on all soil components and all kinds of soil colloids, especially themontmorillonite-ca²⁺colloid. The irreversible process of adsorption-desorption of BSM inreed wetland soil was strongly indicated by hysteresis index （HI）, which also inhibited by saltstress, and hysteresis index decreased with the increasing balanced concentration.The rhizophere effects on the dissipation of BSM was investigated with a speciallydesigned rhizobox where reeds were planted for90days in the soil with BSM at differentconcentration, the soil in the box was divided into six separate compartments at variousdistances from the root surface. Obtained results indicated that the dissipation of BSM wasvaried along with the distance from the reed root, the dissipation gradient of BSM followedthe order: near-rhizosphere> root compartment> far-rhizosphere soil zones, and the largestand most rapid loss of BSM in soil was observed at about2mm from the root zone other thanat the root zone. The increase in soil microbial biomass and the activity of soil invertase wererelated to the enhanced dissipation of BSM. Further investigation was conduced usingphospholipid fatty acids （PLFAs） profiles to follow the millimeter spatial response of the soilmicrobial community, the results showed52PLFAs with carbon chain length from C12toC20were identified under the combined exposure of salt and BSM, the microbial communitywas affected by BSM significantly, and some unique microbial markers were induced by thecombined exposure of salt （0.130mg/l） and BSM （50mmol/l）, such as ISO17:1G,19:0cycloc11-12,18:2w6c,20:4w6c,18:1w9t Alcohol,16:1w7c, ANTEISO17:1AT9,19:1（w8?）Alcohol and so on.The results drawn from a hydroponics experiment to investigate the response of rootexudates of reed to BSM under salt stress showed that, the pH in environment was notaffected significantly by the root exudates with the induction by BSM （2.5mg/l,5.0mg/l,10.0mg/l,50mmol/l） under salt stress （50mmol/l）, but the induction strengthened thesecretion of total organic carbon （TOC）, total sugar and the amino acid from reed root, andthe induction function enhanced gradually along with the increasing BSM concentration.Simultaneously, the induction of BSM and salt were antagonistic in the total sugar and aminoacid of root exudates, especially in total sugar significantly.A special hydroponics experiment was conducted to elucidate the effects of iron plaquefrom root surface on the response of reed to BSM under salt stress. The Fe²⁺at lowerconcentration （0-20mg/l） can promote the growth of reed, however Fe²⁺at higherconcentration （>20mg/l） inhibited the growth, and the inhibition of BSM and salt to the rootgrowth of reed presented synergistic effects significantly. The mass of iron plaque on reedroot surface was greatly affected by the Fe²⁺concentration in environment, and the iron plaque mass increased significantly with Fe²⁺concentration increasing rather than the reedbiomass. The root exudates of reed induced by salt stress might stimulate the formation ofiron plaque on root surface. The iron plaque mass substantially influenced the adsorption ofBSM on root surface, and both presented a significantly positive correlation. The effect ofsalt stress on the adsorption of BSM by iron plaque on root surface was reflected in theimprovement of adsorption efficiency, because of the inhibition of root biomass.更多还原