冷冻干燥法制备阿特拉津降解菌剂的条件优化

旨在研究通过冷冻干燥法制备出高活性的阿特拉津降解菌剂,并得到最佳工艺条件。采用冷冻干燥法制备阿特拉津降解菌HBT4（Microbacterium sp.）菌剂,通过单因素及正交试验对工艺条件进行优化,其中以菌体存活率为指标。结果表明添加的保护剂的最佳配方为蔗糖10% (w/v),甘油8 mL/L,脱脂乳15% (w/v)。然后在正交试验中选取4个影响因素,单因素试验结果确定3个水平,得出最佳工艺为：菌液的离心速度为7000 r/min、菌体与冻干保护剂的配比为2:1、冻干过程中装液量为12 mL、冻干的时间为16 h,此时冻干菌体的存活率最高为75.1%。该试验条件下所制备的菌剂存活率高且稳定性较好,为微生物菌剂的工艺化生产及应用奠定基础。     

喷雾干燥法制备阿特拉津降解菌剂条件优化

[目的]针对土壤中农药残留严重造成的污染问题,本研究旨在研究制备阿特拉津降解菌剂的最佳工艺条件,为采用微生物菌剂修复土壤的研究奠定基础。[方法]试验采用高效降解菌株HBT4,对其进行纯化与扩培,选择合适的保护剂用喷雾干燥法制成固体粉末菌剂,以含水量、菌体存活率及有效活菌数为指标,采用正交试验方法进行工艺条件的优化。[结果]探索结果的最佳工艺条件为：蠕动泵转速15%、热空气流速35L.h-1、保护剂与菌泥的比例(V:V)为3:1、入口温度170℃。最佳工艺条件下得到的产品含水量为4.42%,有效活菌数为1.45×109 cfu/mL,菌体存活率为82.6%。[结论]用喷雾干燥法在最佳工艺条件下所制得的HBT4的降解菌剂对阿特拉津有良好的降解效果,这将为未来除草剂的微生物降解菌剂的研制提供良好的菌种资源。     

气相色谱串联质谱法测定土壤中除草剂残留含量

以气相色谱串联质谱法(GC-MS/MS)多反应监测(MRM)方式进行定量和定性分析建立了土壤中除草剂莠去津、塞克津、2,4-D丁酯残留含量的联合测定方法。结果表明,本方法有效地降低了样品复杂基质带来的干扰,简化了分析步骤。采用外标法定量测得回收率为73%～104%,标准偏差为5.9%～11.5%,方法的回收率和线性关系结果令人满意,实验证明,该方法快速、准确、灵敏度高,适用于土壤中除草剂莠去津、塞克津、2,4-D丁酯残留含量的联合检测。     

Effects of some integrated management options on parthenium interference in sorghum

Parthenium is widely distributed across the uncropped areas of the tropics. It has slowly encroached into many crops and causes considerable yield loss. It heavily infests sorghum, which is widely cultivated by the resource‐poor farmers in Africa and Asia. Its interference and management in sorghum in these cropping systems is not well understood. Therefore, this experiment was undertaken to determine the appropriate parthenium management techniques to use in sorghum crops. All the studied weeds, in combination with parthenium, offered greater competition to sorghum than parthenium alone. Similarly, under a composite stand of weeds, parthenium was inferior in competitiveness to the other weeds until 60 days after sowing (DAS); by 90 DAS, it could accumulate a higher dry weight due to its consistent growth. A pre‐emergence treatment of atrazine (0.75 kg ha^‐1) with wheat straw mulch (5.0 t ha^?1) brought about a consistent and significant reduction in the parthenium growth and, consequently, increased the sorghum yield by 90.8%. Cowpea intercropping with and without pendimethalin (1.0 kg ha^?1) as a pre‐emergence treatment could not control parthenium between 0 and 60 DAS, but could reduce the parthenium growth during the later period of 60–90 DAS, which resulted in a significant increase in sorghum growth. These intercropping treatments increased the sorghum grain yield by 156.2% and 142.4%, respectively, over the unweeded control and by 18.5% and 12.1%, respectively, over the weed‐free control. These treatments also promoted a higher uptake of N, P, and K by the sorghum crop. Thus, cowpea intercropping was the most effective method for parthenium management vis‐à‐vis sorghum yield improvement, followed by cowpea intercropping with pendimethalin and then by atrazine as a pre‐emergence treatment with wheat straw mulch.     

PGPR对莠去津污染土壤中结缕草生长及生理的影响

探究接种植物根际促生菌(PGPR)对结缕草幼苗生长与生理代谢的影响,为莠去津污染土壤中种植草坪草提供理论依据.采用双因素试验设计,以结缕草幼苗为材料,将幼苗分为PGPR(荧光假单胞杆菌,Pseudomonas fluorescens)接种和未接种两组,进行莠去津处理(浓度梯度为0、3、15、75 mg/kg),并测定不...     

湿地植物香蒲根系抗氧化酶活性和根系分泌物对阿特拉津胁迫的响应

为探明阿特拉津胁迫下水生植物根系的生理响应特征,以典型湿地植物香蒲（Typha angustifolia L.）为研究对象,采用水培实验,研究阿特拉津（0、0.2、0.4 mg·L^-1和2.0 mg·L^-1）胁迫45 d对香蒲根系阿特拉津积累、抗氧化酶活性以及根系分泌物的影响。结果表明：阿特拉津可以在香蒲根系积累且显著降低香蒲生物量。随阿特拉津胁迫的提升,根系丙二醛（MDA）含量持续升高;超氧化物歧化酶（SOD）活性显著降低（P<0.05）,过氧化氢酶（CAT）活性呈先增加再降低趋势（P<0.05）,且在0.4 mg·L^-1时达到最大值,较对照提高123.7%;阿特拉津胁迫对谷胱甘肽（GSH）活性无明显影响。香蒲根系分泌物中检出的化合物种类随着阿特拉津质量浓度的升高而增多,主要包括烷烃、烯烃、酯、胺、醇、酚、酮和有机酸类化合物,其中烷烃类化合物种类最多且相对含量最大;高浓度阿特拉津胁迫（2 mg·L^-1）抑制酯类和醇类化合物的分泌,而提高酚类和有机酸类化合物的分泌量;根系阿特拉津含量、MDA含量分别与酚类和有机酸类的相对含量呈正相关关系。研究发现,阿特拉津胁迫诱导的氧化应激激活了香蒲根系的抗氧化防御系统,植物通过调节分泌物的组成和含量应对胁迫,最终降低了生物量的积累。     

除草剂阿特拉津对血清体系中性激素干扰机理研究

为了进一步了解环境内分泌干扰物对人体内性激素平衡的影响,选择阿特拉津这种已被确认为环境内分泌干扰物的农药,通过研究阿特拉津、天然性激素（雌二醇、睾酮）加入血清后体系紫外吸收峰的变化、温度与体系荧光强度关系等方法,确定了阿特拉津、天然性激素对血清组分的荧光猝灭机理,认为阿特拉津可发生类似天然性激素和血清组分间的基态络合。此外,通过计算各二元体系的结合常数发现,阿特拉津与血清组分的结合常数与天然性激素常数较为接近,可以认为阿特拉津具有与天然性激素相近的对血清组分的结合能力,并可能与天然性激素发生竞争结合,由此影响生物体内正常的性激素水平。     

低浓度阿特拉津对鲫鱼超氧化物歧化酶(SOD)活性的影响

将鲫鱼分别暴露于浓度为0、0.1、0.5、1.0、5.0和10.0mg·L-1的阿特拉津溶液中,在染毒后的第3、6、10、14、19和24d对1.0和10.0mg·L-1两个浓度组的鲫鱼进行取样;在实验结束时(24d)对所有浓度组进行取样,分别测定其肝脏、肾脏和肌肉中SOD活性,研究在不同作用时间和不同暴露浓度下,阿特拉津对鲫鱼肝脏、肾脏和肌肉SOD活性的影响。结果表明,阿特拉津能使鲫鱼肝脏、肾脏和肌肉SOD活性产生显著变化。在染毒后的第24d,各浓度组肝脏SOD活性均受到抑制,肾脏SOD活性均受到诱导,肌肉SOD活性在低浓度下受抑制,高浓度下被诱导;且在本实验所设浓度范围内,阿特拉津与肝脏SOD活性之间存在剂量-效应关系,与肾脏SOD活性在1.0～10.0mg·L-1范围内存在剂量-效应关系。在14～24d内,阿特拉津与肌肉SOD活性之间存在时间-效应关系,与肝脏和肾脏SOD活性之间在任何时间范围内都不存在明显的时间-效应关系,但在整个实验期内,1.0和10.0mg·L-1两个暴露浓度对同一器官SOD活性的影响具有相同的变化趋势。     

A risk assessment of atrazine use in California: human health and ecological aspects

A risk assessment of the triazine herbicide atrazine has been conducted by first analyzing the toxicity database and subsequently estimating exposure. Margins of safety (MOS) were then calculated. Toxicity was assessed in animal studies and exposure was estimated from occupational and dietary sources. In acute toxicity studies, atrazine caused developmental toxicity in the rabbit [no observed effect level (NOEL) 5 mg kg(-1) day(-1)] and cardiotoxicity in a dog chronic study (NOEL 0.5 mg kg(-1) day(-1)); cancer (mammary glands) resulted from lifetime exposure. The mammary tumors, which occurred specifically in female Sprague-Dawley rats, were malignant, increased in a dose-dependent manner and were also observed with other, related triazines. Evidence for a genotoxic basis for these tumors was either equivocal or negative. Triazines have been shown to be clastogenic in Chinese hamster ovary cells, in vitro, but without showing a convincing dose/response relationship. Atrazine can be converted into genotoxic N-nitrosoatrazine in the environment or the digestive system, suggesting that N-nitrosamines derived from triazines could be oncogenic. However, it was concluded that N-nitrosotriazines are unlikely to play a significant role in triazine-induced rat mammary gland tumors. An endocrine basis for the mammary tumors, involving premature aging of the female SD rat reproductive system, has been proposed. A suppression of the luteinizing hormone surge during the estrus cycle by atrazine leads to the maintenance of elevated blood levels of 17beta-estradiol (E2) and prolactin. The mechanism for tumor development may include one or more of the following: the induction of aromatase (CYP19) and/or other P450 oxygenases, an antagonist action at the estrogen feedback receptor in the hypothalamus, an agonist action at the mammary gland estrogen receptor or an effect on adrenergic neurons in the hypothalamic-pituitary pathway. None of these has been excluded as a target because there has been a lack of a rigorous attempt to address the mechanism of action for mammary tumors at the molecular level. The potential occupational exposure to atrazine was assessed during mixing, loading and application. Absorbed daily dosage values were 1.8-6.1 microg kg(-1) day(-1). The MOS values (animal NOEL/human exposure) for short-term (acute) exposure were 820-2800. Longer-term occupational exposure and risk were also calculated. Detectable crop residues are generally absent at harvest. Theoretical calculations of acute dietary exposure used tolerance levels, along with secondary residues, and water, for which there is a maximum contamination level; atrazine plus the three main chlorotriazine metabolites were combined. MOS values were above 2000 for all population subgroups. Dietary exposure to atrazine is therefore extremely unlikely to result in human health hazard. Recent publications have reported a possible feminization of frogs, measured in laboratory and field studies. This is assumed to be due to the induction of aromatase, but no measurements of enzyme activity have been reported. In field studies, the water bodies with the greatest numbers of deformed frogs sometimes had the lowest concentrations of atrazine. Other studies have also cast doubt on the feminization theory, except perhaps at very high levels of atrazine. Epidemiology studies have investigated the possibility that atrazine may result in adverse effects in humans. Although some studies have claimed that atrazine exposure results in an elevated risk of prostate cancer, the published literature is inconclusive with respect to cancer incidence.     

Field experiments for the evaluation of pesticide spray-drift on arable crops

Two distinct approaches were used to characterise spray-drift during the application of atrazine and alachlor to a maize crop. The first consisted in determining the quantities which did not reach their target. A first experiment was carried in 2001 to improve the sampling method. A second experiment in 2002 showed that losses represented 46 and 38% for atrazine and alachlor, respectively. The second approach was to follow the spatiotemporal evolution of the cloud formed during application. The concentrations observed near the application zone during spraying reached 4.5 microg m(-3) for atrazine and 8.5 microg m(-3) for alachlor. With alachlor these concentrations decreased rapidly when increasing distance from the plot or time following treatment, whereas in the case of atrazine they stabilised rapidly (between 0.5 and 0.3 microg m(-3)) both in space and in time. Deposits around the plot were light and slightly higher for alachlor (from 20 to 130 microg m(-2)). Alachlor was more rapidly diluted in space than atrazine, reflecting a differentiated evolution of physical form during the process. Alachlor, being more volatile than atrazine, is quickly transferred to the gaseous phase which was more rapidly dispersed than aerosols.