The pesticide module of the Root Zone Water Quality Model (RZWQM): testing and sensitivity analysis of selected algorithms for pesticide fate and surface runoff

The Root Zone Water Quality Model (RZWQM) is a one-dimensional, numerical model for simulating water movement and chemical transport under a variety of management and weather scenarios at the field scale. The pesticide module of RZWQM includes detailed algorithms that describe the complex interactions between pesticides and the environment. We have simulated a range of situations with RZWQM, including foliar interception and washoff of a multiply applied insecticide (chlorpyrifos) to growing corn, and herbicides (alachlor, atrazine, flumetsulam) with pH-dependent soil sorption, to examine whether the model appears to generate reasonable results. The model was also tested using chlorpyrifos and flumetsulam for the sensitivity of its predictions of chemical fate and water and pesticide runoff to various input parameters. The model appears to generate reasonable representations of the fate and partitioning of surface- and foliar-applied chemicals, and the sorption of weakly acidic or basic pesticides, processes that are becoming increasingly important for describing adequately the environmental behavior of newer pesticides. However, the kinetic sorption algorithms for charged pesticides appear to be faulty. Of the 29 parameters and variables analyzed, chlorpyrifos half-life, the Freundlich adsorption exponent, the fraction of kinetic sorption sites, air temperature, soil bulk density, soil-water content at 33 kPa suction head and rainfall were most sensitive for predictions of chlorpyrifos residues in soil. The latter three inputs and the saturated hydraulic conductivity of the soil and surface crusts were most sensitive for predictions of surface water runoff and water-phase loss of chlorpyrifos. In addition, predictions of flumetsulam (a weak acid) runoff and dynamics in soil were sensitive to the Freundlich equilibrium adsorption constant, soil pH and its dissociation coefficient.     

Characterisation of new strains of atrazine-degrading Nocardioides sp. isolated from Japanese riverbed sediment using naturally derived river ecosystem

A Gram-positive bacterial strain able to degrade the herbicide atrazine was isolated using a simple model ecosystem constituted with Japanese riverbed sediment and its associated water (microcosm). Treatment of the water phase of the microcosm with 1 mg litre-1 [ring-14C]atrazine resulted in the rapid degradation of atrazine after a 10 day lag phase period. The [ring-14C]cyanuric acid formed was transiently accumulated as an intermediary metabolite in the water phase and was subsequently mineralised through triazine ring cleavage. Possible atrazine-degrading microbes suspended in the water phase of the microcosm were isolated by the plating method while rapid degradation of atrazine was in progress. Among the 48 strains that were isolated, 47 exhibited atrazine-degrading activity. From these 47 isolates, 12 strains that were randomly selected were found to identically convert atrazine to cyanuric acid via hydroxyatrazine. Polymerase chain reaction (PCR) amplification of the genes corresponding to atrazine degradation revealed that these strains at least carried the genes trzN (atrazine chlorohydrolase from Nocardioides C190) and atzC (N-isopropylammelide isopropyl amidohydrolase from Pseudomonas ADP). Physiological characteristics and 16S rDNA partial sequences of six strains that were further selected strongly suggested that all these isolates originated from the same Nocardioides sp. strain. Additionally, only one isolate could mineralise the triazine ring of cyanuric acid. Based on microscopic observations, this strain appears to be a two-membered microbial consortium consisting of Nocardioides sp. and a Gram-negative bacterium. In conclusion, atrazine biodegradation in the microcosm appeared to occur predominantly by Nocardioides sp. to yield cyanuric acid, which could be mineralised by the other relatively ubiquitous microbes.     

根际效应对狼尾草降解土壤中阿特拉津的强化作用

采用盆栽根袋培养法,研究了根际效应在狼尾草降解土壤阿特拉津中的作用。结果表明,盆栽培养28 d后,狼尾草对土壤中阿特拉津有较好的根际强化降解效果,狼尾草根际土壤阿特拉津去除率为52.70%,非根际土壤的阿特拉津去除率为37.60%。土壤自身具有修复阿特拉津的潜能,无狼尾草处理的湛江砖红壤中阿特拉津降解以非生物降解为主,降解率为16.90%,土著微生物对阿特拉津的生物降解效果弱于非生物降解,仅为11.70%。狼尾草通过根际效应显著提高了土壤总微生物数量和活性,增加了土壤可培养细菌、真菌和放线菌的数量,尤其是土壤可培养细菌数量,提升了土壤细菌群落结构的丰富度和均匀度,进而间接强化土壤阿特拉津的生物降解。     

几种除草剂及其混剂药效及对玉米安全性评价

盆栽试验条件下，比较了乙草胺、草净津和莠去津及其三者组成的混剂用作土壤处理与茎叶处理剂对玉米安全性，杀草谱及除草效果。结果表明，药剂各处理对玉米安全。土壤处理，3种单剂对单子叶杂草株防效差别不大，对双子叶杂草株防效依次为：乙草胺＝秀去津＞草净津，杂草鲜重抑制效果相当，ED50、ED90相近，分别为154．4－160．4g.ai/hm^2和715．1－871．1g.ai/hm^2；茎叶处理，对单子叶杂草株防效依次为：乙草胺＝莠去津＞草净津，对双子叶杂草株防效依次为：草净津＞莠去津＞乙草胺，杂草鲜重毒力依次为莠去津＞乙草胺＞草净津，ED50、ED90分别为78－107．9g.ai/hm^2和412．3－1271．4g.ai/hm^2。3种混剂杀草谱较单剂广、效果高。     

节杆菌AD26的分离鉴定及其与假单胞菌ADP对阿特拉津的联合降解

用富集培养法,从农药厂的工业废水中分离到高效降解除草剂阿特拉津的AD26菌株,通过16S rRNA基因序列分析,该菌株被鉴定为节杆菌(A rthrobacter sp.).降解基因的PCR分析表明,AD26含有阿特拉津降解基因trzN和atzBC,它能以阿特拉津为唯一氮源、蔗糖或柠檬酸钠为碳源生长,将阿特拉津降解成氰尿酸,降解速度快但降解不完全.假单胞菌(Pseudomonas sp.)ADP是Waekea实验室分离的阿特拉津降解菌株,含有阿特拉津降解基因atzABCDEF,能以阿特拉津为唯一氮源、柠檬酸钠为碳源(不能以蔗糖为碳源)生长.将阿特拉津降解成NH3,和CO2,降解完全但降解速度慢.在阿特拉津浓度为200 mg·L-1的无机盐培养基中进行的AD26和ADP混合培养表明,它们对阿特拉津的降解发生了互补和增强作用,两个菌株能在以阿特拉津为唯一氮源、蔗糖为碳源的培养基中生长,而且生长和降解速率都好于单个菌株,培养72 h后阿特拉津去除率达到99.9%,其中76.7%的阿特拉津被降解成NH3和CO2.这表明由节杆菌AD26和假单胞菌ADP组成的混合菌株在阿特拉津废水处理和污染土壤的生物修复中有很好的应用潜力.     

污泥土地利用途径分析

污泥中含有丰富的氮、磷和有机质等肥力成分,土地利用是污泥处置的主要途径。污泥和污泥堆肥的土地施用可以促进植物的生长、提高作物的产量以及明显改善土壤的物理和生物学性质,然而污泥中的重金属元素是限制其大规模农田利用的重要因素。污泥和施污土壤中重金属形态的研究可以用来评价土壤中重金属的生物有效性以及它们在土壤中的移动性。文章概述了提取土壤中重金属元素的主要方法及污泥土地利用的方式。     

莠去津对中华绒螯蟹蜕皮抑制激素表达的影响

用RT-PCR方法检测了中华绒螯蟹暴露于不同质量浓度[0(DMSO对照)、0.001、0.01、0.1、1、10 mg/L]莠去津后蜕皮抑制激素在眼柄视神经节中的表达。结果表明,低质量浓度的莠去津可诱导蜕皮抑制激素的合成分泌,其中0.1 mg/L处理组作用明显。莠去津对中华绒螯蟹的蜕皮活动有一定影响。     

粘土矿物固定化微生物对土壤中阿特拉津的降解研究

以粘土矿物为载体,采用吸附挂膜法对已筛选的阿特拉津降解菌株进行固定化,并应用固定化微生物降解土壤中的阿特拉津。结果表明,该菌株在粘土矿物上生长良好,根据菌种生理生化特性、环境扫描电镜图片以及16S rDNA基因的相似性分析初步鉴定该菌株为Ochrobactrum sp.。接种降解菌能明显加快阿特拉津在土壤中的降解速率,粘土矿物固定化微生物的降解效果要明显优于游离菌,粘土矿物粒径越小,固定化微生物的降解效果越好,纳米粘土矿物固定化微生物的降解效果要好于原粘土矿物。用一级动力学方程描述阿特拉津在土壤中的降解过程,不同土壤中阿特拉津的降解速率不同。阿特拉津在红壤、砂姜黑土、黄褐土中的降解半衰期（t1/2）分别为36.9、49.1、55.0 d,投加纳米蒙脱石固定化降解菌后的半衰期则分别为16.3、25.3、21.7 d。     

不同施肥处理下旱地红壤中阿特拉津的环境归趋及其调控研究

本研究采集长期施用化肥或有机肥(猪粪)的旱地红壤,设置单一或复合添加木质素和牡蛎壳粉的不同组合处理,进行微宇宙试验。采用同位素示踪、定量PCR、高通量测序等方法,研究施肥及土壤改良措施对红壤中阿特拉津矿化特征及降解微生物的调控作用。结果表明,在14周培养期间,旱地红壤对阿特拉津的矿化率低于0.33%。牡蛎壳粉有效提高红壤p H、改变土壤细菌群落,将施化肥、有机肥土壤中矿化率大幅提高至43.3%和9.51%,同时导致atz C和trz N等阿特拉津降解功能基因的富集。木质素则显著促进阿特拉津残留态形成,使阿特拉津与土壤有机质的结合达对照组的6.1倍,但对污染物的矿化没有明显作用。本研究结果有助于阐明旱地红壤中阿特拉津的环境归趋,并为发展适用于红壤的污染物控制技术提供科学依据。     

阿特拉津降解菌ADH-2的分离、鉴定及其特性研究

从长期施用阿特拉津的玉米地中采集土样,通过富集培养的方法分离出一株能以阿特拉津为唯一碳、氮源生长的细菌ADH-2,结合生理生化特陛及16SrRNA基因的相似性分析将其初步鉴定为节杆菌属（Arthrobacter sp．）。该菌在10h内对100mg·L-1阿特拉津的降解率为99．9％。外加氮源能促进菌株的生长,但对阿特拉津的降解有轻微的抑制作用。外加蔗糖和葡萄糖能显著促进菌株的生长,但对阿特拉津的降解表现出显著的抑制。而淀粉既能促进菌株的生长又能促进阿特拉津的降解。对其降解基因的初步研究显示,该菌含有trzN、atzB和atzC3个阿特拉津降解相关基因。通过与本实验室另外两株阿特拉津降解菌比较,菌株ADH-2具有更好的应用潜力。