Biodegradation of methyl parathion by Acinetobacter radioresistens USTB-04

Biodegradation of methyl parathion （MP）, a widely used organophosphorus pesticide, was investigated using a newly isolated bacterium strain Acinetobacter radioresistens USTB-04. MP at an initial concentration of 1200 mg/L could be totally biodegraded by A. radioresistens USTB-04 as the sole carbon source less than 4 d in the presence of phosphate and urea as phosphorus and nitrogen sources, respectively. Biodegradation of MP was also achieved using cell-free extract of A. radioresistens USTB-04. MP at an initial concentration of 130 mg/L was completely biodegraded in 2 h in the presence of cell-free extract with a protein concentration of 148.0 mg/L, which was increased with the increase of pH from 5.0 to 8.0. Contrary to published reports, no intermediate or final degradation metabolites of MP could be observed. Thus we suggest that the cleavage of C-C bond on the benzene ring other than P-O bond may be the biodegradation pathway of MP by A. radioresistens USTB-04.

A new fluorescence probing strategy for the detection of parathion-methyl based on N-doped carbon dots and methyl parathion hydrolase

A new facile fluorescence probing strategy, which was based on N-doped carbon dots（NCDs） and methyl parathion hydrolase（MPH）, was developed for the determination of parathion-methyl（PM）. The fluorescence intensity of NCDs-MPH system was proportional to PM concentration in the range of 2.38–73.78 mmol/L, with a detection limit of 0.338 mmol/L. Moreover, the present simple and facile method could be used to determine methyl parathion in environmental and agricultural samples successfully.Furthermore, the detection mechanism of this system is inner filter effect and molecular interactions between NCDs and p-nitrophenol, which is the hydrolysis product of PM catalyzed by methyl parathion hydrolase.

A nanosilica/exfoliated graphene composite film-modified electrode for sensitive detection of methyl parathion

Graphene nanosheets （GS） were easily prepared through liquid-phase exfoliation of graphite powder in N,N-dimethylformamide （DMF） with the assistance of sodium citrate. Then, GS was coated onto a glassy carbon electrode （GCE） surface by drop to fabricate a GS]GCE nanointerface. Subsequently, by using tetraethylorthosilicate sol as precursor, nanosilica was electrochemically deposited onto the GS]GCE surface to produce a nanocomposite film electrode （nanosilicaJGSJGCE）. Electrochemical behaviors of methyl parathion （MP） on the nanosilica/GS/GCE surface were investigated thoroughly. It was found that the nanosilicaJGS nanocomposites can improve the redox peak currents of MP significantly due to the synergetic effect. The oxidation peak current was linearly related to MP concentration in the range from 0.0005 μmol/L to 5.6 μmol/L. The detection limit was calculated to be 0.07 nmol/L （SJN = 3）. The developed method was used to determine MP in real samples. The recoveries were in the range from 95.4% to 104.2%, demonstrating satisfactory results.

Enhanced Degradation of Methyl Parathion in the Ligand Stabilized Soluble Mn(Ⅲ)-Sulfite System

The ligand-stabilized soluble Mn(Ⅲ) recognized as active intermediate can potentially mediate the attenuation of contaminants. In this study,the abiotic degradation behaviors of methyl parathion in the ligand stabilized Mn(Ⅲ)-sulfite system were investigated. The results showed that the yield of soluble Mn(Ⅲ) produced from the redox reaction of MnO2 and oxalic acid was dependent linearly on the dosage of Mn O2 and caused the decomposition of methyl parathion up to 50.1% in Mn(Ⅲ)-sulfite system after 30 minutes. The fitted pseudo-first-order reaction constants of methyl parathion degradation increased with the increasing of the amount of produced Mn(Ⅲ) but was not effected linearly by the addition of sulfite. Other ligands,including pyrophosphate and oxalic acid,acted as effective complexing agents to stabilize soluble Mn(Ⅲ),and exhibited competitive effect on methyl parathion degradation with sulfite. The formation of Mn(Ⅲ)-sulfite complexes is the critical step in the system to produce abundant reactive oxygen species identified as SO3·-to facilitate methyl parathion degradation. The hydrolysis and oxidation of methyl parathion were acknowledged as two primary transformation mechanisms in Mn(Ⅲ)-sulfite system. These findings indicate that naturally ligands-stabilized soluble Mn(Ⅲ) can be generated and could oxidatively decompose organophosphate pesticides such as methyl parathion.

Potential neoplastic effects of parathion-methyl on rat liver

The mutagenic and carcinogenic effects of parathion-methyl were examined by bacterial reverse mutation assay and a long-term experiment with wistar rats. The potential mutagenic effect of parathion-methyl in Salmonella typhimurium TA100 bacterial cells was observed without rat liver S9 metabolic activation. Parathion-methyl was further investigated for pathological changes in rat pancreas and liver. The long-term rat experiments showed that parathion-methyl exposure for 3 months can cause pathological changes in rat pancreases acinar cells and pancreatic hepatocytes. Atypical acinar cell focuses （AACF） were determined in the liver and pancreas of the rats. The results from short-term Ames test and long-term rat experiments suggested that parathion-methyl would be potential carcinogenic.

Study on Sorption of Monocrotophos and Parathion-methyl on Yellow River's Sediments

A study on the sorption of monocrotophos and parathion methyl on Yellow River's sediments was performed. The influence of some factors, such as pH value and ionic strength, on the sorption was investigated and first order kinetics mode for the sorption of monocrophos was shown. Freundlich isotherm was suggested as the most appropriate type for monocrophos and parathion methyl. But the sorption isotherms of monocrotophos and parathion methyl are also in conformity with Langmuir equation. Both partition and adsorption occur to the sorption of monocrophos to Yellow River's sediments, but partition is the predominant for that of parathion methyl.

SPE-GC-FPD法测定三七中甲基对硫磷残留量

目的:为更好地控制三七质量,拟建立三七中甲基对硫磷的GC-FPD检测方法。方法:采用超声提取固相萃取法、GC-FPD检测。结果:方法回收率在62.52%~118.49%,精密度RSD为3.597%,标准偏差符合检测要求,满足农药残留检测的要求。

基于rGO-AuNPS修饰丝网印刷电极的电化学生物传感器快速检测甲基对硫磷

目的:实现对甲基对硫磷的快速检测。方法:基于金纳米颗粒和还原氧化石墨烯制备了用于对甲基对硫磷进行定量检测的乙酰胆碱酯酶传感器。采用层层组装方法,将还原氧化石墨烯、金纳米颗粒、乙酰胆碱酯酶依次修饰在丝网印刷电极表面。对传感器的催化活性、阻抗特性、传感器的抑制率与甲基对硫磷浓度的关系、实际样品检测进行了评估。结果:制备的乙酰胆碱酯酶生物传感器对乙酰硫代胆碱氯化物表现出优异的亲和力,米氏常数为2.76 mmol/L。在最佳条件下,可以有效检测甲基对硫磷,线性范围为5~500 ng/mL,检出限为0.692 ng/mL。结论:该方法操作简单、成本低、稳定性好,适用于有机磷类农药的快速检测。

相对湿度条件下二氧化锰对甲基对硫磷的转化行为

以不同晶型的二氧化锰(MnO_(2))为试验材料,探讨了相对湿度(relativehumidity,RH<5%~100%)条件下MnO_(2)对典型有机磷农药甲基对硫磷的转化行为。结果显示:甲基对硫磷的一级降解速率与RH呈明显负相关性,与MnO_(2)含量呈明显正相关性;不同晶型MnO_(2)对反应体系中甲基对硫磷的降解行为差异较大,其一级动力学降解反应速率常数(kobs)顺序为α-MnO_(2)>γ-Mn O_(2)>β-Mn O_(2);负载离子(PO_(4)^(3-)、Ca^(2+)和Mn^(2+))都能明显抑制甲基对硫磷的降解反应速率,其中Mn^(2+)的抑制效果最为显著;RH条件下Mn O_(2)对甲基对硫磷的转化路径主要包括水解和氧化,水解产物为对硝基苯酚,氧化产物为甲基对氧磷。本研究结果证实了实际土壤层RH显著影响锰氧化物对有机磷农药的转化行为,对理解天然环境中该类污染物的归趋行为具有参考价值。

气相色谱法测定蔬菜中甲基对硫磷残留量的不确定度评定

依据《测量不确定度评定与表示》(JJF 1059.1—2012)和《蔬菜和水果中有机磷、有机氯、拟除虫菊酯和氨基甲酸酯类农药多残留的测定》(NY/T 761—2008),建立评定蔬菜中甲基对硫磷残留量测定不确定度的数学模型,分析其测定不确定度的主要来源有样品质量称量、体积、工作液配制、添加回收、精密度,计算其合成标准不确定度与扩展不确定度。结果表明,标准储备液及标准工作液配制引入的不确定度是不确定度的关键来源,甲基对硫磷合成标准不确定度Uc(W)为0.00182 mg/kg,取置信水平为95%,甲基对硫磷扩展不确定度U(W)为0.00364 mg/kg,蔬菜中甲基对硫磷残留量测定的不确定度可表示为(X±U)=(0.10±0.00364)mg/kg。

CuNWs/PBS复合材料修饰电极的构建及对OPs的检测

采用两步水热法制备了直径均一、高长径比的铜纳米线(Cu NWs)和多孔碳球(PCBs),利用透射电镜(TEM)对其结构和形貌进行了表征.同时通过滴涂法将其修饰于玻碳电极表面,构建了电化学传感器,采用循环伏安法和交流阻抗法对电极的电化学行为进行了考察.结果表明,铜纳米线直径为5~10 nm,具有高长径比,所制传感器对K_(3)[Fe(CN)_(6)]探针具有良好的电化学响应,并将其应用于对甲基对硫磷(MP)的检测中,采用差分脉冲伏安法,在最佳条件下,氧化峰电流和甲基对硫磷的质量浓度在0.1~50 mg·L^(-1)范围内呈良好的线性关系,检出限为0.04 mg·L^(-1).此传感器具有制作简单、灵敏度高、良好的线性范围等优点,期望应用于实际样品检测.

全自动在线固相萃取-液相色谱串联质谱法快速测定地表水中痕量甲基对硫磷

建立了全自动化在线固相萃取-液相色谱串联质谱法快速、准确测定地表水中痕量甲基对硫磷的方法.水样经在线富集、色谱柱分离后,梯度洗脱,采用电喷雾离子源正离子多反应监测模式,内标法定量.通过对离子源参数、水相洗脱溶剂、有机相洗脱溶剂、洗脱溶剂初始比例进行优化试验,甲基对硫磷的灵敏度显著提升,峰型更好.该方法在质量浓度5—1000 ng·L^(-1)范围内线性关系良好(相关系数R^(2)≥0.998).添加回收试验结果表明,方法检出限为4 ng·L^(-1),方法定量限为16 ng·L^(-1),在40、100、500 ng·L^(-1)的3个添加水平下,平均回收率为90.1%—97.8%,相对标准偏差为1.7%—3.5%。应用于实际地表水样品测定,结果均未检出.该方法便捷、高效,可实现高通量测定地表水中痕量甲基对硫磷.

假单胞菌WBC-3甲基对硫磷水解酶性质的初步研究

从最近分离到的有机磷农药降解菌Pseudomonassp .WBC 3中获得了甲基对硫磷水解酶 (Methylparathionhydrolase,MPH ,EC 3 1 8 3)。该酶在 48h的培养物中分布比例分别为 :上清液 2 1 % ,胞内 86 2 %和胞间质 1 1 7% ,说明MPH为胞内酶。经过CM sepharoseFastFlow阳离子交换层析 ,获得电泳纯的酶。SDS PAGE和凝胶过滤层析表明 ,该酶为单体蛋白 ,分子量约为 34kD。动力学分析显示该酶为非特异性有机磷降解酶 ,但最适底物为甲基对硫磷。在pH9～ 1 2范围 ,酶表现较高活力水平 ,最高活力的反应温度为 40℃。根据各类金属离子和鳌合剂对酶活的影响 ,推测MPH为金属酶。

流动注射化学发光测定甲基对硫磷

首次研究了农药甲基对硫磷在碱性介质中（ｐＨ：１１．５～１２．０）与鲁米诺和过氧化氢产生化学发光的行为及反应机理，并发现水溶性高分子聚乙二醇对该反应具有显著的增效作用，据此建立了流动注射化学发光测定甲基对硫磷的新方法。甲基对硫磷的浓度在 ５×１０－８～１．０ ×１０－５ｇ／ｍＬ范围内与化学发光强度呈良好的线性关系；检出限为 ２×１０－８ｇ／ｍＬ；对 １．０×１０－６ｇ／ｍＬ甲基对硫磷进行了１１次平行测定，相对标准偏差小于４％；标准加入回收率为８３％～９４％。该法应用于谷物中农药残余量的测定，结果满意。

凤眼莲植物修复水溶液中甲基对硫磷的效果与机理研究

报道了凤眼莲 (EichhorniacrassipesSolms)净化水溶液中甲基对硫磷的作用及修复甲基对硫磷污染水体的主要机理。研究结果表明 ,与空白抑菌水溶液相比 ,10— 11g凤眼莲抑菌可将 2 5 0mL的 10mg L的甲基对硫磷降解速度提高 76 3 5 2 %。处理 10d后甲基对硫磷的消除率 ,凤眼莲培养液为 99 9% ,对照水溶液为 4 0 1%。其修复机理主要是凤眼莲的直接吸收和微生物降解。在不抑菌条件下 ,凤眼莲对水溶液中甲基对硫磷净化的贡献率达 6 7 2 8% ,微生物降解约占 2 3 97%

茶叶中水胺硫磷、亚胺硫磷、甲基对硫磷和伏杀硫磷农药残留的高效液相色谱法测定

建立了茶叶中4种有机磷农药——水胺硫磷、亚胺硫磷、甲基对硫磷和伏杀硫磷残留的高效液相色谱测定方法．在45℃加温条件下用乙酸乙酯-正己烷（1：1，by vol．）混合溶剂提取待测目标物、活性炭层析柱净化，用10．0mL乙酸乙酯-正己烷（6：1，by vol．）淋洗待测组分，以Eclipse XDB-Cs色谱柱、乙腈-水混合液梯度洗脱分离、二极管阵列检测器测定．结果表明，上述4种农药在6．5min内能很好地分离；样品中添加的待测组分能定量回收，回收率89．0％～108．0％，相对标准偏差为1．89％～5．96％（1．0μg／mL，n=5），检出限分别为：水胺硫磷9．82μg／kg、亚胺硫磷7．88pg／kg、甲基对硫磷2．19pg／kg、伏杀硫磷0．72pg／kg（dm）．

降解甲基对硫磷真菌的分离及降解特性

利用富集培养基从农药厂的活性污泥中分离到 3株能以甲基对硫磷为碳源和能源而生长的真菌 ,分别编号为 Hw- 3、Hw- 6和 Hw- 7,并进行了降解条件的研究。结果表明 ,p H7.0、温度 2 8℃是 3株真菌降解甲基对硫磷的最佳条件。同时对底物浓度对降解率的影响及菌株的共代谢作用进行了探讨。

有机磷农药对锯齿新米虾的毒性及敏感性分析

以锯齿新米虾为受试生物,研究了敌敌畏、马拉硫磷、对硫磷、甲基对硫磷和乐果5种有机磷农药对锯齿新米虾(Neocaridina denticulate)暴露时间为4d的急性毒性和28d的慢性毒性.结果表明,敌敌畏、马拉硫磷、对硫磷、甲基对硫磷和乐果对锯齿新米虾的96h半数致死浓度(96h-LC_(50))分别为34.100,846.408,7.736,4.132,1606.875ng/L.28d无可观测效应浓度(NOEC)分别为0.991,7.755,0.269,0.222,100ng/L.28d最低可见效应浓度(LOEC)分别为1.388,15.200,0.404,0.333,200ng/L.锯齿新米虾对乐果和对硫磷相对不敏感,对马拉硫磷和甲基对硫磷不敏感,对敌敌畏较敏感.研究结果可为5种有机磷农药的水生生物基准的制定及环境风险评估提供科学依据.

表面活性剂对甲基对硫磷光解的影响

以高压汞灯和太阳光为光源 ,研究 S1 、 S2 等 1 0种表面活性剂在玻片表面和水溶液中对甲基对硫磷光解的影响。结果表明 :在玻片表面 ,甲基对硫磷在高压汞灯和太阳光下的光解半衰期分别为 4 .83 h和 5.0 6h。表面活性剂对甲基对硫磷光解有显著的敏化或猝灭作用。S1 、β-C、OP、 0 2 0 1、JFC和 2 2 0 1分别促进甲基对硫磷的表面光解 1 .3 2～ 3 .3 5倍 ,而 T和 S2 则延缓其光解 1 .59和 2 .0 4倍。甲基对硫磷在高压汞灯和太阳光下水溶液中的光解半衰期分别为 3 .96h和 3 1 .0 8h,表现光敏作用的表面活性剂有 S1 、T和 885,而 S2 、TX-8对甲基对硫磷在水溶液中的光解在两种光源下则表现相反的作用。