Entry of pesticides into the plant symplast as measured by their loss from an ambient solution

A method was developed to determine the extent of penetration of substances into the plant symplast. The known apoplastic dye trisodium 3-hydroxy-5,8,10-pyrenetri-sulphonate (PTS) and various systemic pesticides were studied using potato tuber tissue. The dye penetrated only 5% of the volume of living tissue while those pesticides which display an apoplastic pattern of transport in plants penetrated the entire tissue volume. The pesticides diffused freely out of the tissue when it was transferred to fresh medium. It is proposed that the term euapoplastic be used to describe chemicals that behave like the dye, and that the term pseudoapoplastic be used to describe chemicals that behave like atrazine, carbendazim, carboxin and diuron. 2,4-D, which displays a symplastic transport pattern in the plant, was concentrated by the tissue and did not diffuse out freely. It appears that the property which allows a pesticide to be transported in the symplast is not its ability to penetrate the plasmalemma but rather its ability to be retained by the symplast after entry.     

Adsorption of systemic fungicides and a herbicide by some components of plant tissues,in relation to some physicochemical properties of the pesticides

Lignin, an important component of plant tissues, adsorbed five systemic fungicides and one herbicide (carbendazim, triadimefon, nuarimol, triarimol, fenarimol and fluometuron) more strongly than bovine serum albumin, cellulose, ethylcellulose or sodium polygalacturonate. Significant correlations were found between the extent of the adsorption of the pesticides on the lignins extracted from three different plant species, and the log Poet (Poet is the octan-1-ol/water partition coefficient) of the compounds. The more lipophilic fungicides triarimol and fenarimol (log Poet about 2.6) were adsorbed to the greatest extent. Fluometuron, triadimefon and nuarimol (log Poet about 2.0) were moderately adsorbed, whereas carbendazim with the lowest log Poet (1.34 at pH 5.0), was adsorbed more than expected from its Poet value. The anomaly of carbendazim is discussed; it is ascribed to it's partial protonation at pH 5.0, whereas the other pesticides were non-ionised.     

杨梅中4种农药残留的膳食风险评估及家庭清洗去除效果

为明确杨梅中农药残留风险及去除效果,利用QuEChERS样品前处理方法结合高效液相色谱-串联质谱(HPLC-MS/MS)法测定了来自市场流通和生产环节的239个批次杨梅样品中检出率和残留量相对较高的4种农药(2,4-D、咪鲜胺、嘧菌酯和多菌灵)残留量.采用点评估方法评价了杨梅中4种农药的膳食暴露风险,并分别选择清水冲洗...     

九种常用农药在桃树生长后期使用的安全性

为了评价桃生长后期使用农药的安全性,以桃早熟品种‘金陵黄露’为材料,分别在桃果收获前7和14 d,按最高推荐剂量及2倍最高推荐剂量混合施用9种农药,包括4种杀虫剂 (阿维菌素、氯虫苯甲酰胺、氯氟氰菊酯和吡虫啉) 和5种杀菌剂 (苯醚甲环唑、腈苯唑、嘧菌酯、甲基硫菌灵和多菌灵),研究了桃果中的农药残留量变化及不同农药在桃枝、桃叶、果皮和果肉中的分布规律,以及套袋在桃生长后期阻控农药吸收中发挥的作用。结果表明:在桃收获前7 d,按2倍最高推荐剂量施用其中3种杀菌剂 (苯醚甲环唑、腈苯唑、嘧菌酯) 和4种杀虫剂 (阿维菌素、氯虫苯甲酰胺、氯氟氰菊酯、吡虫啉),7种农药在桃全果中的残留量均低于中国国家农药残留限量标准(MRL);而过量施用多菌灵和甲基硫菌灵,桃全果中多菌灵残留量显著高于MRL标准,且随着施药后时间的延长,增加了多菌灵由果皮或枝叶向果肉迁移的风险。套袋处理后,桃全果中多菌灵的残留量远低于中国MRL标准,同时显著减少了桃全果中其他8种农药的残留量。9种供试农药在桃树不同组织中的分布规律一致,由高到低依次为果皮>全果>桃叶≥果肉≥桃枝。本研究表明,不同农药品种在桃生长后期消解规律存在差异,其中多菌灵和甲基硫菌灵超量使用会增加多菌灵在桃果中残留超标的风险,而套袋处理可减少桃果中的农药残留。该结果对去除桃果中农药残留、降低膳食摄入风险有一定指导意义。     

几种农药多元组合对HepG2人肝癌细胞的联合毒性效应

多种农药残留经膳食暴露途径进入人体后,其联合毒性的潜在风险通常超过单一农药。为探明农药多残留的联合暴露毒性,采用经典MTT (噻唑蓝) 比色法,测定了阿维菌素、啶虫脒、多菌灵、百菌清、毒死蜱、高效氯氟氰菊酯、咪酰胺和三唑磷8种农药多种组合方式联合暴露下对HepG2人肝癌细胞增殖的抑制活性。结果表明:联合暴露24 h后,不同种类农药组合对HepG2细胞存活率的影响存在较大差异,随着组合农药质量浓度升高,部分组合对HepG2细胞增殖的抑制效应分别呈现S型变化和线性变化。例如,二元组合 (多菌灵+高效氯氟氰菊酯) 在0~10.00 mg/L、三元组合 (多菌灵+阿维菌素+高效氯氟氰菊酯) 在0~24.12 mg/L、四元组合 (三唑磷+高效氯氟氰菊酯+多菌灵+阿维菌素) 在0~47.46 mg/L以及五元组合 (毒死蜱+阿维菌素+啶虫咪+高效氯氟氰菊酯+三唑磷) 在0~62.80 mg/L暴露条件下其抑制效应表现为S型变化,即随着组合农药质量浓度增大,细胞存活率先迅速降低,之后则缓慢降低;二元组合 (多菌灵+百菌清) 在0~8.46 mg/L、三元组合 (毒死蜱+啶虫脒+多菌灵) 在0~39.97 mg/L、四元组合 (多菌灵+高效氯氟氰菊酯+百菌清+阿维菌素) 在0~25.92 mg/L以及六元组合 (啶虫脒+毒死蜱+三唑磷+多菌灵+高效氯氟氰菊酯+阿维菌素) 在0~57.48 mg/L暴露条件下其抑制效应表现为线性变化,即随着组合农药质量浓度升高,细胞存活率呈线性降低。本研究对农产品中农药多残留的体外细胞毒性进行了评估,明确了不同农药多残留组合对HepG2人肝癌细胞增殖的抑制作用剂量-效应关系,可为进一步探索农药多残留的细胞毒性机制和开展食品安全风险评估提供依据。     

农田尾菜发酵过程中农药残留变化特征

基于尾菜中存在农药残留的现状,以设施农业尾菜黄瓜秧为研究对象,采用气相色谱法和超高效液相色谱-串联质谱法检测了尾菜黄瓜秧在静态好氧发酵过程中多菌灵、吡虫啉、哒螨灵等50种农药残留的动态变化,并分析发酵重要影响因子堆高对农药残留消解的影响。结果表明:在尾菜黄瓜秧中共检测出腐霉利、多菌灵、嘧菌酯、苯醚甲环唑、烯酰吗啉、虫螨腈、吡虫啉、啶虫脒和哒螨灵9种农药残留,其中多菌灵平均残留量最高,达11.2 mg/kg,其他8种农药平均残留量在0.042~0.89 mg/kg之间。在发酵的24 d中,不同堆高条件下9种农药的消解规律均符合一级反应动力学方程,但不同农药半衰期差异较大,其中吡虫啉的平均半衰期最长,为28.9 d,多菌灵的平均半衰期最短,为10.2 d;不同堆高处理中农药的消解速率也有差异,总体上在2.5 m堆高下各农药的消解率最高、半衰期最短。本研究结果可为尾菜发酵参数优化、农业废弃物的高效资源化利用以及研发基于尾菜发酵产物的有机蔬菜专用有机肥提供理论支撑。     

基于荧光探针技术检测30种农兽药及其二元、三元组合对CYP3A4酶的联合毒性

在农业生产中混合使用多种农药或兽药越来越普遍,但因药剂联合毒性效应的不确定性而对人体健康产生严重威胁。本文基于酶抑制法原理,利用荧光探针 NEN (N-乙基-1,8-萘二甲酰亚胺) 直接检测CYP3A4酶的活性,建立了广谱筛查混合农兽药联合毒性效应的方法,并以常用的30种农兽药及其典型的23种二元和26种三元组合为研究对象,检测了农兽药混合物对CYP3A4酶的联合毒性效应,其中标准质量浓度根据食品安全国家标准规定的农兽药最大残留限量确定。结果表明:3种质量浓度梯度下对CYP3A4酶均具有协同作用的混合农兽药组合有克百威 + 多菌灵、克百威 + 吡虫啉、啶虫脒 + 烯酰吗啉、吡虫啉 + 多菌灵、氯氰菊酯 + 啶虫脒 + 烯酰吗啉、克百威 + 啶虫脒 + 多菌灵、吡虫啉 + 啶虫脒 + 多菌灵、吡虫啉 + 啶虫脒 + 烯酰吗啉、毒死蜱 + 啶虫脒 + 多菌灵和联苯菊酯 + 啶虫脒 + 多菌灵。当单一农兽药对CYP3A4酶活性的抑制率较高时,与其他农兽药混合后联合毒性效应呈拮抗作用,而当单一农兽药对酶活性的抑制率低于2%时,则与其他农兽药混合后联合毒性效应呈现不确定性。农兽药组合在低浓度下对CYP3A4酶的联合毒性往往存在较强的协同作用,但随着浓度的升高,联合毒性效应从协同变为拮抗作用。分析农兽药与CYP3A4酶之间的构效关系可知,含有芳氯基团的数量与对酶活性的抑制程度成正相关,含有3个芳氯及以上基团的农兽药对CYP3A4酶活性的抑制作用最为显著,抑制率在30%以上,如百菌清、毒死蜱、甲基毒死蜱、咪鲜胺等;含有2个芳氯或“强吸电子基团 + 1个芳氯”基团的农兽药,对CYP3A4酶活性的抑制作用较强,抑制率在18%以上,如苯醚甲环唑、哒螨灵和异菌脲等。具有氨基甲酸酯基团的农兽药单独作用于CYP3A4酶毒性较小或几乎没有毒性时,与其他农兽药混合后显示较强的协同作用。本研究建立的检测方法为广谱筛查混合农兽药联合毒性提供了新思路,检测结果可为进一步在细胞和动物水平制订农兽药混剂的风险评估方案提供依据。     

四种农药在莼菜加工过程中的残留量变化

为了考察敌百虫、毒死蜱、氯氰菊酯和多菌灵4种农药在莼菜加工过程中的加工因子,从而优化莼菜的加工过程,分别模拟莼菜加工的清洗、杀青、护绿和储藏4个步骤,考察4种农药的加工因子,并分析每个步骤的相关因素对加工因子的影响。采用气相色谱-火焰光度检测器（GC-FPD）检测敌百虫和毒死蜱的含量,气相色谱-电子捕获检测器（GC-ECD）检测氯氰菊酯的含量,液相色谱-二极管阵列检测器（LC-DAD）检测多菌灵的含量。结果表明:随着清洗时间的增加,4种农药的加工因子逐渐变小,并在一定时间后趋于稳定;在供试的10 min内,杀青时间越长,4种农药的加工因子越小;护绿和储藏条件的改变对加工因子均无显著影响。综合考虑莼菜品质和农药残留两方面因素,建议莼菜清洗时间为30 min,在不影响莼菜品质的前提下尽量延长杀青时间。     

糙皮侧耳菌丝培养液对4种农药的降解活性

为明确食用菌培养液对农药污染物的降解活性,运用液相色谱-串联质谱仪 (LC-MS/MS) 和超高效液相色谱仪-附带二级阵列管检测器 (UPLC-PDA) 技术,测定了乐果、啶虫脒、高效氯氟氰菊酯和多菌灵4种农药在糙皮侧耳液体培养基中的降解动态及随漆酶活性变化情况。结果表明:4种农药在培养液中残留降解动态符合一级动力学模型,高效氯氟氰菊酯、多菌灵、乐果和啶虫脒的降解半衰期分别为2.93、4.38、11.83和14.01 d,降解速率由高到低为高效氯氟氰菊酯 > 多菌灵 > 乐果 > 啶虫脒。灭菌后培养液中漆酶活性消失,农药降解速率降低。在1 h和4 h时,粗酶液浓度越高,农药降解率越大,4种农药的降解率与漆酶活性符合ExpDec1型函数关系。本研究证实了糙皮侧耳培养液对4种农药的降解具有促进作用,初步揭示了漆酶具有降解农药的活性,为糙皮侧耳降解农药资源开发提供了技术支持。     

QuEChERS-UPLC-MS/MS法快速筛查稻米和稻茎中42种农药残留

建立了QuEChERS前处理技术结合超高效液相色谱-串联质谱 (UPLC-MS/MS) 同时检测稻米和稻茎中42种农药残留的分析方法。样品经乙腈涡旋提取、QuEChERS净化管净化,C₁₈超高效液相色谱柱分离后,在电喷雾正离子 (ESI+) 模式下,通过多反应监测正离子模式进行检测,采用基质匹配标准曲线峰面积外标法进行定量分析。结果表明:在0.01~0.2 mg/L范围内,42种农药的质量浓度与对应的峰面积间线性关系良好,R2 > 0.99,检出限为0.001~0.002 mg/kg。在0.01、0.02、0.05、0.1和0.2 mg/kg 5个添加水平下,42种农药在稻米和稻茎中的平均回收率均为70%~117%,相对标准偏差 (RSD) 稻米为1.5%~15%和稻茎为0.9%~15%。该方法具有操作简单、快速、灵敏度高、准确度高等优点,适用于稻米和稻茎中多种类农药残留的快速筛查分析。     

Influence of stem diameter, water content, and freezing-thawing on bacterial canker development in excised stems of dormant stone fruit

ABSTRACT In excised dormant stems of peach (Prunus persica), prune (Prunus domestica), and almond (Prunus dulcis), stem diameter, stem hydration, and freezing-thawing influenced the extent of infection caused by Pseudomonas syringae pv. syringae. Bacterial lesion length increased with increasing stem diameter, demonstrating the need to account for the effects of stem diameter when lesion length data are analyzed. Lesion length increased or decreased with stem hydration or dehydration, respectively. However, tissue water content was not a good indicator of tissue susceptibility to infection by P. syringae pv. syringae, as larger diameter stems had larger lesions and lower water content than did smaller diameter stems. After freezing at -5 degrees C for 12 to 24 h, inoculations made during the thawing process produced significantly larger lesions than did inoculations performed before freezing or after thawing. These results support the hypothesis that the increased susceptibility to bacterial canker that is associated with noninjurious freezing is a result of the increased passive spread of bacteria through water redistribution when inoculation is performed during the thawing process. Plant tissue water relationship characteristics that can influence water movement during freezing and thawing may be an important component of bacterial canker development in stone fruit trees.     

CTMAB-膨润土对水溶液中4种农药的吸附特性

用溴化十六烷基三甲铵(CTMAB) 制得改性膨润土, 研究了CTMAB-膨润土吸附水中甲萘威、甲基对硫磷、克百威、多菌灵的性能和适宜条件。结果表明: CTMAB-膨润土对水溶液中4 种农药有较强的吸附能力, 且与CTMAB 在膨润土上的实际交换量有关, 随着表面活性剂浓度的增大而增大; 但CTMAB 浓度≥4% 时, 实际发生吸附的农药就不再随着加入量的增加而增大。4 种农药的吸附等温线呈线性, 表明分配模式是主要的吸附形式。有机膨润土对4 种农药的吸附很快, 大部分农药在10 m in 内被吸附。pH 值变化对吸附有不同的影响, 并与农药性质有关: 低pH 值会降低有机农药的吸附量, 4 种农药在pH4～ 10 时吸附量较稳定,高pH 值导致多菌灵的吸附量增加, 而甲萘威、甲基对硫磷和克百威有分解现象。     

药剂诱导稻飞虱再猖獗及科学用药

稻飞虱是典型的再猖獗型重大害虫。害虫再猖獗包括生态再猖獗和生理再猖獗,前者主要由药剂杀伤天敌使天敌功能崩溃引起,后者指药剂刺激害虫生殖导致害虫增殖倍数显著增加。刺激稻飞虱生殖的药剂包括大部分有机磷、菊酯类、氨基甲酸酯类杀虫剂,及一些除草剂和杀菌剂(如井冈霉素、多菌灵)等。通过蛋白质组学、转录组学、基因表达谱分析及基因沉默试验证实化学药剂刺激稻飞虱生殖主要涉及与生殖和代谢相关基因的上调表达,但同一药剂对稻飞虱组团物种产生物种间基因功能生态位分离。这就需要在深入理解化学农药对生态系统中组团物种的正负效应和生殖影响的基础上进行精准用药技术设计。本文综述了一些农药对稻田害虫天敌行为、生殖、捕食功能及稻飞虱生殖影响的机理,并基于同种药剂对稻飞虱组团内不同物种生殖的相反效应,提出稻飞虱多物种共存时的科学用药技术。     

不同采收期及贮藏条件下冬枣中54种农药的筛查、残留消解动态与膳食风险评估

利用气相色谱-串联质谱法及液相色谱-串联质谱法,研究了不同贮藏时间、贮藏温度及采收期对冬枣在不同流通环节中农药残留的影响,并对冬枣中检出的12种农药的安全使用风险进行了评估.结果表明,对供试冬枣样品筛查了54种待测农药,共检出12种,检出率为22.6％,均未检出禁用和高毒农药.在室温条件下,多菌灵在冬枣中的半衰期为4....     

铁皮石斛中3种常用农药的残留动态及最佳清除方法研究

以被苯醚甲环唑、多菌灵及烯酰吗啉污染的铁皮石斛为研究对象,采用乙腈提取,固相分散法净化,高效液相色谱-串联质谱仪分析了3种农药在铁皮石斛鲜条及栽培基质中的残留消解动态,并检测了不同水洗时间、不同溶液浓度（氯化钠和碳酸氢钠）条件下农药残留的去除情况,通过响应面方法确定了农药最佳去除方法。结果表明:3种常用农药在不同添加水平下的回收率为78.5%~106%,相对标准偏差（RSD）为0.7%~4.5%,满足农药残留检测要求;田间试验采用推荐剂量和两倍推荐剂量处理,苯醚甲环唑在铁皮石斛鲜条和基质中的半衰期分别为3.8~3.9 d和4.1~5.6 d;多菌灵的半衰期分别为2.6 d和2.8~3.1 d;烯酰吗啉的半衰期分别为2.8~2.9 d和3.6~5.1 d。响应面法结果显示:经质量分数为5.49%的氯化钠和1.27%的碳酸氢钠混合溶液浸泡5 min后再用清水冲洗45 min,残留的苯醚甲环唑去除率最高;用5.34%的氯化钠和1.22%的碳酸氢钠混合溶液浸泡5 min后再用清水冲洗45 min,多菌灵的去除率最高;而用2.07%的氯化钠和0.80%的碳酸氢钠混合溶液浸泡5 min后再用清水冲洗59 min,烯酰吗啉的去除率最高。本研究可为铁皮石斛质量安全评价体系的建立提供基础数据。     

Ground deposit of pesticides in relation to the cereal canopy density

Pesticides not reaching the intended target may have negative effects on the environment and the field ecosystem. To estimate the potential ground water pollution and risk for soil-dwelling organisms it is necessary to estimate the amount of pesticide reaching the soil in different spraying situations. Literature shows that ground deposition may vary even within equal growth stages due to variations in canopy density. This paper discusses the feasibility of estimating the ground deposition of pesticides from canopy density in cereal fields. Spray experiments were carried out in wheat and barley with flat-fan nozzles of two sizes. Differences of ground deposition between the two nozzle sizes were insignificant. Adding surfactant to the spray solution significantly reduced the soil deposition in barley and in wheat cv Sleipner but not in cv Haven. A significant effect of Leaf Area Index (LAI) on ground deposition was obtained. A simple exponential model based on the LAI with an extinction coefficient of 0.48–0.50 may for many occasions satisfactorily describe the soil deposition of pesticides in cereals. Using non-destructive LAI-measurements combined with the deposition model may be useful in pesticide risk assessment on field, farm and larger regional scale and is optimising the application rate in site-specific farming. © 1999 Society of Chemical Industry     

Rate of volatilisation of pesticides from soil surfaces; comparison of calculated results with those determined in a laboratory model system

A laboratory model system for the determination of the volatility of non-ionic pesticides from soil surfaces is presented. The pesticides examined were the insecticides methidathion, diazinon, and isazophos, the herbicide metolachlor, and the fungicide metalaxyl. The rates of volatilisation of these compounds from soil increased with increasing pesticide concentration, temperature and air flow rate and with decreasing soil organic matter content. The volatilities of the same pesticides were also calculated by using their vapour pressure, water solubility and soil adsorption data. The excellent correlation between calculated and experimental results showed that information on the volatility of a chemical can be obtained simply by calculation. Such calculations allow the classification of each pesticide according to its volatility, and therefore represent a useful alternative for volatility studies in laboratory model systems.     

Anti-oxidant response of Cucumis sativus L. to fungicide carbendazim

Our purpose in this research was to determine the response of anti-oxidative enzymes of cucumber (Cucumis sativus L.) when carbendazim applied as soil drench at 0, 5, 50, and 100 mg kg⁻¹. The changes in the activity of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX) enzymes were measured in roots, stems, and leaves of cucumber. The plants were sampling at cotyledon phase (14 days) and florescence phase (56 days). A strong correlation between anti-oxidant content and carbendazim concentration was observed. As concentration increased, the activities of SOD and CAT increased in roots and leaves. While in stems, SOD and CAT activities were increased in florescence phase and declined in cotyledon phase. The content of GPX increased in stems, and declined in leaves. Higher levels of SOD, CAT, and GPX were observed in cucumber cotyledons than the older leaves. The present study suggested that carbendazim treatments had different effects on cucumber anti-oxidant system in different tissues. It was concluded that cotyledons might play an important role for adaptation as the carbendazim concentration increased, and the ability of mature cucumber to maintain a balance between the formation and detoxification of activated oxygen species appeared likely to enhance. On the basis of our observations, we conclude that increased SOD, CAT and GPX activity provides plant with increased carbendazim stress tolerance.     

QuEChERS-超高效液相色谱-串联质谱法测定香菇中56种农药残留

建立了香菇中多菌灵、啶虫脒、氟虫腈等56种农药残留的超高效液相色谱-串联质谱 (UPLC-MS/MS) 检测方法。样品以酸化乙腈为提取剂,涡旋提取,N-丙基乙二胺 (PSA) 和十八烷基键合硅胶 (C₁₈) 粉末分散固相萃取净化,经BEH-C₁₈超高效液相色谱柱分离后,在电喷雾正离子 (ESI+) 模式下,通过多反应监测 (MRM) 模式测定。结果表明:56种农药在一定的浓度范围内线性关系良好,决定系数 (R2) 均大于0.99;56种农药的平均回收率在71%~121%之间,相对标准偏差为0.6%~9.2%,符合农药多残留分析的要求。考察了溶剂和滤膜对检测结果的影响。结果发现,当定容溶剂含有高比例的水相时,哒螨灵等化合物在过聚四氟乙烯 (PTFE) 或尼龙材质的滤膜时有明显损失。基质效应测定结果显示,灭多威等40种化合物表现为弱基质效应,甲胺磷等16种化合物表现为中等强度基质效应。研究表明,建立的QuEChERS-超高效液相色谱-串联质谱法能够对香菇中56种农药残留进行快速、准确的测定。     

正确认识化学农药的问题

针对当前我国农药使用中存在的一些主要问题作了详细地分析,其中有些属于基本概念,应须统一认识,但很多属于农药使用中实际操作如何规范化的问题。文中提出了解决问题的一些建议和措施。