2,4-D丁酯的水解与光解特性研究

通过室内模拟试验,研究2,4-D丁酯在不同pH值和温度下的水解动态和在有机溶剂中的光解特性。结果表明,2,4-D丁酯的水解与光解均符合一级动力学方程。在pH7以下的缓冲溶液中,2,4-D丁酯的水解反应十分缓慢,但在碱性溶液中其水解速率加快。25℃下2,4-D丁酯在pH5、7和9的缓冲溶液中的水解半衰期分别为23.5、5.8d和10.7min。2,4-D丁酯的水解速率随温度升高而增加,在温度为15、25℃和35℃的pH7缓冲溶液中的水解半衰期分别为21.5、5.8、3.9d,平均温度效应系数为2.57。2,4-D丁酯水解反应的活化能与温度之间无明显相关性,而活化熵与温度呈显著相关性。2,4-D丁酯的水解主要由活化熵所驱动。采用GC-MS技术对2,4-D丁酯水解产物进行鉴定,确定水解产物主要是2,4-二氯苯氧乙酸和2,4-二氯苯酚。2,4-D丁酯在正己烷中光解速率比在甲醇中快,在丙酮中几乎不发生光解,其光解速率随浓度的升高而减慢。     

2,4-D 对铜在乌栅土胶体和红壤胶体上吸附的影响

应用批平衡法研究了农药2,4-D对Cu在乌栅土胶体和红壤胶体上吸附的影响。结果表明,Cu在两种土壤胶体上的吸附等温线均符合Langmuir方程,Cu在乌栅土胶体上的吸附量较其在红壤胶体上的吸附量要高;在pH3.0～6.7范围内,两种土壤胶体对Cu的吸附量均随溶液pH的升高而升高。2,4-D增加了Cu在土壤胶体上的吸附,2,4-D的浓度越高,Cu的吸附量越大,这主要是由于2,4-D的存在显著增加了平衡液的pH,从而增加了土壤胶体表面所带负电荷量。     

苯磺隆和2,4-D胁迫对土壤微生物影响的研究

以盆栽试验研究了除草剂苯磺隆、2,4-D对石灰性褐土中土壤微生物群落的影响。结果表明,在供试浓度下,土壤微生物对两种除草剂的感应存在一定的差异性。苯磺隆高浓度处理在最初3d极显著地抑制细菌生长,之后对土壤细菌具有刺激作用,特别是培养结束时激活率还高达917.6%,低浓度处理呈极显著的刺激作用;苯磺隆对土壤放线菌具有显著的刺激作用,对土壤真菌有强烈的抑制作用,最高抑制率达100%,到培养结束时(60d)真菌数量还未恢复到对照水平。2,4-D处理对土壤放线菌具有明显的抑制、激活的波动性,对土壤细菌、真菌有强烈的抑制作用。     

纳米Fe3O4/微生物联合体系对2,4-D和阿特拉津降解的研究

采用纳米Fe3O4/微生物联合体系降解溶液中2,4-D和阿特拉津,考察了不同2,4-D和阿特拉津初始浓度、微生物接种量、纳米Fe3O4投加量、溶液ｐＨ值等对降解效果的影响。结果表明,纳米Fe3O4/微生物联合体系对2,4-D和阿特拉津的降解率显著高于纳米Fe3O4和微生物单一体系;2,4-D和阿特拉津初始浓度在0～10 mg·L^-1、微生物接种量在0～12 mg·L^-1、纳米Fe3O4的投加量在0～200 mg·L^-1范围内,2,4-D和阿特拉津的降解率随其初始浓度、微生物接种量和纳米Fe3O4 投加量的增大而增加。溶液pH3．0左右、2,4-D和阿特拉津初始浓度10 mg·L^-1、微生物接种量12 mg·L^-1、纳米Fe3O4投加量200 mg·L^-1,是反应的最佳条件,此实验条件下反应7 d,2,4-D和阿特拉津的残留率分别降低至35．7％和54．0％。     

Fate of 14C-ring-labeled 2,4-D, 2,4-dichlorophenol and 4-chlorophenol during straw composting

Experiments were carried out to study the transformation of ¹⁴C-ring-labeled 2,4-D and the two related chlorophenols 4-chlorophenol (4-CP) and 2,4-dichlorophenol (4-DCP) during straw composting under controlled laboratory conditions. Incubation under sterile and nonsterile conditions was done to evaluate the relative importance of the biotic and abiotic processes. Pre-composted straw was treated with the three chemicals. The availability of the different chemicals was monitored during incubations as well as their degradation. Under nonsterile conditions, the mineralization of both chlorophenols reached 20% of the applied compounds, whereas it was 52% for 2,4-D. Transitory water-soluble metabolites of 2,4-D and chlorophenols were formed but they disappeared rapidly. After 21 days, 21% of the 2,4-D and 38% of the 2,4-DCP was stabilized as nonextractable (bound) residues under nonsterile conditions. Bound residues of both chemicals were negligible under sterile conditions. Availability of chemicals as estimated by water extraction decreased during incubation proportionally to mineralization and to the formation of bound residues. The increase in immobilization of the chemical residues was stronger under nonsterile conditions than under sterile conditions. Under nonsterile conditions 71% of the 4-CP was recovered as bound residues, whereas under sterile conditions 30% of the applied 4-CP formed bound residues after formaldehyde addition and only 8% with autoclaved straw. Global microbial activity decreased in the presence of the chlorophenols probably due to their toxic effect. These data indicate that the biological activity associated with straw transformation during composting stimulates the depletion of 2,4-D and chlorophenols by mineralization and by formation of bound residues. Received: 6 September 1996     

获得甘薯×五倍体种间杂种的杂交后代的有效方法

为获得甘薯×五倍体种间杂种的大量杂交后代而进行的实验表明,反交(即以甘薯为父本)或蒙导授粉(五倍体活花粉与甘薯死花粉混授给异不孕群甘薯)显著促进五倍体花粉管生长和增加结实；生长调节剂(NAA+BA)授粉当天及授粉后5 d两次处理能有限地延长子房寿命；反交(或蒙导授粉)结合生长调节剂处理有利于获得大量适龄子房和有效胚珠，将它们置于筛选到的培养基(MS+CH，或MS+BA+GA3)，成苗率较高，是获得五倍体种间杂种同甘薯杂交的后代的有效方法；自交和互交均不结实的五倍体各系同甘薯品种相间种植以进行放任授粉，能在五倍体植株上收获大量杂交种子，是在一定条件下获得五倍体种间杂种同甘薯杂交的后代的有效方法。     

Relationships between microbial biomass and dissipation of 2,4-D and dicamba in soil

A study was conducted to evaluate relationships between microbial biomass and the dissipation of 2,4-D (2,4-dichlorophenoxy acetic acid) and dicamba (2-methoxy-3,6-dichlorobenzoic acid) in soil. We hypothesized that the size of the microbial biomass should be a strong predictor of the pesticide degradation capacity of a particular soil. Soils with a high microbial biomass should have relatively high levels of general microbial activity and should support a diversity of degradation pathways. In this study, we quantified the degradation of 2,4-D and dicamba in a range of soils with different concentrations of microbial biomass. The herbicides 2,4-D and dicamba were added to similar soils collected from five different land use types (home lawn, cornfield, upland hardwood forest, wetland forest, and aquifer material) and incubated for 80 days under laboratory conditions. Herbicide residue and microbial biomass (C and N) analyses were performed 5, 10, 20, 40, and 80 days following herbicide application. Microbial biomass-C and -N and soil organic matter content were positively correlated with dissipation of 2,4-D and dicamba. The results suggest that there are relationships between the size of the soil microbial biomass and the herbicide degradation capacity of an ecosystem. These relationships may be useful for developing approaches for evaluating and predicting the fate of pesticides in different ecosystems.     

Spatial variability of 2,4-dichlorophenoxyacetic acid (2,4-D) mineralisation potential at a millimetre scale in soil

We analysed the ability of soil units of millimetre size to mineralise a herbicide, 2,4-D, using incubations of individual aggregates (2-7 mm diameter) and 6×6×6 mm³ cubes dissected from soil cores, under standard conditions. Mineralisation of ¹⁴C-ring labelled 2,4-D was measured using a barite paper trap and a Phosphorimager to record the evolved ¹⁴C-CO₂ from these very small soil samples. We found a large variability of 2,4-D mineralisation potential between aggregate size classes, between individual aggregates of the same size and between the different dissected cubes from a given core. We explained this variability by an uneven distribution of the degrading microorganisms at this scale, and to a lesser extent, an uneven distribution of C, necessary for co-metabolism. Furthermore, we found that in a soil core, the dissected cubes with a large mineralisation potential were not randomly distributed, but rather organised into centimetre sized hot spots.     

固相萃取-高效液相色谱法测定4种蔬果中2,4-D的残留量

为建立蔬果中2,4-D残留量高效液相色谱(HPLC)检测方法,以固相萃取为净化手段,采用HPLC法检测番茄、葡萄、枇杷和黄瓜4种蔬果中2,4-二氯苯氧乙酸(2,4-D)的残留量。结果表明,样品经碱性水溶液提取、酸化,C18固相萃取小柱净化后,能够有效排除杂峰干扰,2,4-D残留量检测准确。该方法的线性相关系数为0.9980,检测限为0.0012 mg·kg~(-1),2,4-D的添加回收率为81.8%~116.0%,变异系数(CV)小于6%,表明方法准确度高,能满足番茄、葡萄、枇杷和黄瓜产品中2,4-D残留量的检测。采用此方法测定番茄等4种蔬果21份样品,样品中仅有2份番茄样品检测出2,4-D,残留量均小于0.02mg·kg~(-1)。本研究为利用HPLC检测果蔬中2,4-D残留量奠定了理论基础。     

平阳霉素对花生体细胞胚胎发生的影响

本文对花生离体培养高频率体细胞胚(体胚)诱导方法,及平阳霉素(PYM)对体胚发生的抑制作用进行了研究,旨在为以PYM作为化学诱变剂进行花生离体诱变提供有效方法.以花生品种花育20号和花育22号成熟种子的胚小叶为外植体,在添加不同浓度2,4-D(0,5,10,15,20mg/L)的MSB5(MS无机盐+B5有机成分)培养...