Effects of methamidophos on the community structure,antagonism towards Rhizoctonia solani,and phlD diversity of soil Pseudomonas

A microcosm incubation study using an aquic brown soil from northeast China (a Cambisol in the UN Food and Agriculture Organization FAO Soil Taxonomy) was conducted to examine the effects of different concentrations (0, 50, 150, and 250 mg kg^?1) of methamidophos (O,S-dimethyl phosphoramidothioato) on Pseudomonas, one of the most important gram-negative bacteria in soil. Amplified ribosomal DNA restriction analysis (ARDRA) was performed to study the Pseudomonas community structure, an in vitro assay was made to test the antagonistic activity of isolated Pseudomonas strains against soil-borne Rhizoctonia solani, a major member of the pathogens highly related to soil-borne plant diseases, and special primer amplification and sequencing were performed to investigate the diversity of phlD, an essential gene in the biosynthesis of 2, 4-diacetylphloroglucinol (2, 4-DAPG), which has biocontrol activity in phlD ⁺isolates. With exposure to increasing methamidophos concentrations, the total number of soil Pseudomonas ARDRA patterns decreased significantly, but with less change in the same treatments over 1, 3, and 5 weeks of incubation. The number of isolated Pseudomonas strains with antagonistic activity against R. solani as well as the diversity and appearance frequency of the strains' phlD gene also decreased with increasing concentrations of methamidophos, especially at high methamidophos concentrations. Applying methamidophos could increase the risk of soil-borne plant diseases by decreasing the diversity of the soil Pseudomonas community and the amount of R. solani antagonists, particularly those with the phlD gene.     

Some toxicological aspects op methamidophos exposure in mice 1

Abstract

Cholinesterase activity in the brain, RBC and plasma of Swiss mice was determined following different routes of administration of methamidophos. Continuous feeding with the insecticide caused a progressive inhibition of both plasma‐ and erythrocyte enzymes. The effect of methamidophos was more pronounced when applied in diet than when administered dermally or intraperitoneally. Following a single injection (i.p.) of methamidophos, the brain enzyme showed maximum inhibition 24 hr following treatment. At the appearance of tremors, the plasma and RBC‐enzymes showed considerable inhibition, the former being more inhibited. The plasma enzyme appears to be the most sensitive enzyme and may be taken as a suitable index for exposure to methamidophos.     

光催化降解有机磷农药中甲胺磷的降解效率的测定

采用纳米TiO2光催化降解甲胺磷农药，分别测定分析了PO^3-4,有机磷农药，COD等，以说明光催化降解甲胺磷的情况，结果说明纳米TiO2光催化降解甲胺磷是可行的，根据我们及他人光催化降解有机磷农药的实验结果，比较了分别通过测定TOC，CO2，PO^3-4，有面农药，COD等各种不同的分析方法来衡量光催化降解效率，以评定催化剂的活性及光催化法的可行性的优缺点，以便根据样品的实际情况以及实验室所具备的仪器设备，选择合适的分析方法。     

Book review

Chemical Hazards to Human Reproduction by Ian C. Nisbet and Nathan J. Karch, Noyes Data Corp., Park Ridge, N.J. (1983), 245 pp., $28.00.     

B—82细菌的筛选及降解甲胺磷的实验研究

从受甲胺磷长期污染的土壤中采取土样，经驯化富集后筛选到一株能高效降解甲胺磷的细菌Ｂ－８２菌株，经初步鉴定，为施氏假单胞菌（Ｐｓｅｕｄｏｍｏｎａｓ ｓｔｕｔｚｅｒｉ）。菌株Ｂ－８２能以甲胺磷为为施氏假单胞菌氮和磷源进行生长并将其降解为无机磷，此菌能耐受０．５％的甲胺磷。     

快速测定米饭中甲胺磷农药

用无水硫酸钠吸干米饭中水份，再以乙酸乙脂提取样品中甲胺磷，提取液直接进气相色谱仪测定。达到了分析快速，结果良好。     

工业废水中甲胺磷农药的气相色谱的分离与测定

对测定工业废水中甲胺磷的色谱条件及其干扰进行了试验，并对ＨＰ－５弹性石英毛细管柱和电子捕获检测器，氮磷检测器，火焰光度检测器作了分析比较，结果表明，３０ｍ柱和这３种检测器能满足要求。     

Toxicity and metabolism of acephate in adult and larval insects

Abstract

Adult and larval insects from the terrestrial and aquatic environments were exposed to acephate. The chemical was more toxic to adult insects than to larvae, and was a poor insect cholinesterase inhibitor in vitro compared to methamidophos which was a much stronger inhibitor. Both acephate and methamidophos inhibited the adult cholinesterase in vitro much more strongly than they did the larval enzymes. Acephate was metabolized by the insects to methamidophos which did not appear to be the only metabolite, although no other metabolites were looked for. The cholinesterase of insects exposed to sublethal levels of acephate was inhibited, but this inhibition appeared to be due to the combined effect of acephate and methamidophos and not to any hypothetical substance with greater anticholinesterase activity. This was bourne out when acephate was incubated with mixed function oxidases (MFO). No activated product with potent anticholinesterase activity was identified. Methamidophos was not produced by the MFO system but by some other unidentified mechanism.     

光催化降解甲胺磷的研究

用离子色谱法检测光催化降解甲胺磷的最终产物PO4^3-、SO4^2-、NH4^ 、NO3^-，它们随光照时间的生成量不同，80min时甲胺磷分子中的N原子已完全矿化为NH4^ 和NO3^-，而P、S原子矿化为PO4^3-、SO4^2-则较慢且不同步，刚开始，SO4^2-生成量大于PO4^3-，100min后则PO4^3-生成量大于SO4^2-，经气相色谱及CODCr分析，均表明在甲胺磷光催化降解过程中存在中间产物，用气质联用仪（GC-MS）检测出中间产物CH3-SO2-SCH3及CH3S-SCH3，提出光催化降解甲胺磷的可能途径。     

GC/MS在监测甲胺磷工业废水中的应用

就甲胺磷工业废水监测中甲胺磷及其干扰组分进行了色谱分离及质谱定性分析,并以火焰光度检定量,用甲胺磷工业原油作为标准,圆满完成了甲胺磷工业废水的监测任务。