Aerobic and anaerobic degradation of profluralin and trifluralin

Abstract

The degradation of profluralin [N‐(cyclopropylmethyl)‐α,α,α‐trifluoro‐2,6‐dinitro‐N‐propyl‐]p‐toluidine] and trifluralin (α,α,α‐trifluoro‐2,6‐dinitro‐N,N‐dipropyl‐p‐toluidine) was studied under aerobic and anaerobic soil conditions. Three soils (Goldsboro loamy sand, Cecil loamy sand, Drummer clay loam) were each treated with 1 ppmw herbicide; anaerobic conditions were maintained by flooding. Soil samples were extracted monthly and subjected to TLC analysis. No degradation was detected in sterile controls. Aerobic degradation of both herbicides was greatest in the Cecil loamy sand soil over the entire incubation period. Degradation of profluralin in Cecil soil under aerobic conditions was 86 percent after 4 months with three products detected; 83 percent of the trifluralin was degraded with two products detected. Anaerobic degradation accounted for 72 percent of the profluralin and 78 percent of the trifluralin after 4 months. Degradation of both herbicides increased with incubation time for the first 3 months and decreased slightly thereafter. Generally there was more extensive degradation (percent and in number of products formed) of profluralin than trifluralin under the conditions tested. More degradation products were detected for both herbicides under aerobic conditions than under anaerobic conditions.     

超高效液相色谱-串联质谱法同时检测水中16种芳氧苯氧丙酸酯类除草剂

采用固相萃取-超高效液相色谱-串联质谱法(UPLC-MS/MS)通过对固相萃取柱、洗脱液、流动相等的优化,建立了水中16种芳氧苯氧丙酸酯类(APP)除草剂的分析方法。确定以Oasis HLB为固相萃取柱、丙酮-正己烷(1∶1,V/V)为淋洗液、水-乙腈(3∶7,V/V)为流动相进行水样预处理,在最优条件下,各目标物在水中的回收率均达到74.5%~124.9%,相对标准偏差为4.2%~9.6%,线性范围为1~2 000μg/L,各目标物标准品在UPLCMS/MS系统中有效的线性相关系数(R2)达到0.998以上。该方法具有检测限低、回收率高等优点,经实际样品测试,可适用于水中16种APP类除草剂的同时检测。     

Herbicide Transport in Goodwater Creek Experimental Watershed: II. Long‐Term Research on Acetochlor,Alachlor, Metolachlor,and Metribuzin1

Lerch, R.N., E.J. Sadler, C. Baffaut, N.R. Kitchen, and K.A. Sudduth, 2010. Herbicide Transport in Goodwater Creek Experimental Watershed: II. Long‐Term Research on Acetochlor, Alachlor, Metolachlor, and Metribuzin. Journal of the American Water Resources Association (JAWRA) 1‐15. DOI: 10.1111/j.1752‐1688.2010.00504.x Abstract: Farmers in the Midwestern United States continue to be reliant on soil‐applied herbicides for weed control in crop production, and herbicide contamination of streams remains an environmental problem. The main objective of this study was to analyze trends in concentration and load of acetochlor, alachlor, metolachlor, and metribuzin in Goodwater Creek Experimental Watershed (GCEW) from 1992 to 2006. A secondary objective was to document the effects of best management practices (BMPs) implemented within GCEW on herbicide transport trends. Median relative herbicide loads, as a percent of applied, were 3.7% for metolachlor, 1.3% for metribuzin, 0.36% for acetochlor, and 0.18% for alachlor. The major decrease in alachlor use and increase in acetochlor use caused shifts in flow‐weighted concentrations that were observed over the entire concentration range. The smaller decrease in metolachlor use led to a consistent decreasing time trend only for the upper end of the concentration distribution. Metribuzin also showed moderate decreases in concentration with time since 1998. Annual loads were generally correlated to second quarter discharge. Despite extensive education efforts in the watershed, conservation BMPs within GCEW were mainly implemented to control erosion, and therefore had no discernable impact on reducing herbicide transport. Overall, changes in herbicide use and second quarter discharge had the greatest effect on trends in flow‐weighted concentration and annual load.     

“百草枯”生产的环境风险评价

结合河北省桃园农药厂开发的百草枯新工艺(低温钠法),对百草枯生产过程中的环境风险进行评价。首先介绍了百草枯生产的工艺流程,然后系统分析了金属钠、吡啶、氯甲烷以及百草枯等危险物的性质及其危害性,并在上述分析的基础上,采用相应的评价模型对钠化釜及合成釜中吡啶可能造成的爆炸与扩散进行了评价。最后,就百草枯生产的环境风险提出了相应的对策和防范措施。     

多重环境因子对氟胺磺隆在土壤中降解的影响

氟胺磺隆作为普遍使用的一种磺酰脲类除草剂,已经对土壤和作物造成了危害,其环境行为受很多物理化学或生物因素的影响.为探明不同环境因素对氟胺磺隆在土壤中降解程度的影响,通过实验室内模拟培养的方法,研究了土壤微生物、不同土壤类型、水溶性有机物（dissolved organic matter,DOM）、温度、土壤含水量等因素对氟胺磺隆在土壤中降解的影响.结果表明,各种环境因子：温度、湿度、土壤微生物和土壤类型等均在不同程度上影响了氟胺磺隆的土壤降解速率.土壤微生物量、土壤有机质和DOM的增加均有利于氟胺磺隆在土壤中的降解,并且土壤pH的降低,也会促进氟胺磺隆在土壤中的降解.其中,土壤微生物是影响氟胺磺隆土壤降解的主要因素.该研究结果将为一些生物和物理化学因子调节氟胺磺隆在土壤中消散提供初步数据.     

Absorption and translocation of sulfometuron-methyl in sugarcane (Saccharum officinarum L.) at different growth stages

ABSTRACT

In Brazil, weed management in sugarcane fields is mainly done with the use of selective herbicide formulations. For many years, diuron+hexazinone was one of the main herbicide mixture formulations used in sugarcane. Later, sulfometuron-methyl was included in the same mixture, which was marketed as a new herbicide formulation for residual in-season weed control in sugarcane. The mixture diuron+hexazinone+sulfometuron-methyl has been widely used in commercial sugarcane fields in Brazil. However, recent field observations have shown that sugarcane plants at different growth stages varied in their phytotoxicity levels after treatment with diuron+hexazinone+sulfometuron-methyl. Greenhouse and laboratory studies were conducted to determine ¹⁴Csulfometuron-methyl absorption and translocation, as well as ¹⁴C distribution in sugarcane at two growth stages, 2 to 3 leaves and 5 to 6 leaves. ¹⁴Csulfometuron-methyl absorption by sugarcane did not differ between the two growth stages. Different patterns of ¹⁴C accumulation were observed, which may explain variations in sulfometuron-methyl phytotoxic responses observed in the field.     

Inhibition kinetics of acid and alkaline phosphatases by atrazine and methomyl pesticides

The main objective of this work was to investigate the kinetic characteristics of acid and alkaline phosphatases isolated from different sources and to study the effects of the herbicide atrazine and insecticide methomyl on the activity and kinetic properties of the enzymes. Acid phosphatase (ACP) was isolated from the tomato plant (Solanum lycopersicum L. var. lycopersicum); alkaline phosphatase (ALP) was isolated from two sources, including mature earthworms (Aporrectodea caliginosa) and larvae of the Egyptian cotton leafworm (Spodoptera littoralis). The specific activities of the enzymes were 33.31, 5.56 and 0.72 mmol substrate hydrolyzed per minute per milligram protein for plant ACP, earthworms ALP and cotton leafworm ALP, respectively. The inhibition kinetics indicated that atrazine and methomyl caused competitive–non-competitive inhibition of the enzymes. The relationships between estimates of K_m and V_max calculated from the Michaelis–Menten equation have been explored. The extent of the inhibition was different, as estimated by the values of the inhibition constant K_i that were found to be 3.34 × 10^?3, 1.12 × 10^?2 and 1.07 × 10^?2 mM for plant ACP, earthworms ALP and cotton leafworm ALP, respectively, with methomyl. In the case of atrazine, K_i were found to be 8.99 × 10^?3, 3.55 × 10^?2 and 1.36 × 10^?2 mM for plant ACP, earthworms ALP and cotton leafworm ALP, respectively.     

Mobility and efficacy of 2,4-D herbicide from slow-release delivery systems based on organo-zeolite and organo-bentonite complexes

This research aimed to develop slow-release formulations (SRFs) of 2,4-dichlorophenoxyacetic acid (2,4-D) using zeolite and bentonite minerals modified with cetyltrimethylammonium (CTMA) surfactant. Adsorption–desorption, greenhouse bioassay and column experiments were carried out to assess the potential of the SRFs to control weeds while reducing the herbicide leaching losses to deep layers of soil. The results showed that only 6.5 mmol 2,4-D kg^?1 was retained by Na-bent, and the herbicide was not adsorbed by Na-zeol at all. The surface modification with CTMA surfactant, however, improved the 2,4-D adsorption capacity of the zeolite and bentonite up to 207.5 and 415.8 mmol kg^?1, respectively. The synthesized organo-minerals slowly released the retained 2,4-D discharging 22 to 64% of the adsorbed 2,4-D to the solution phase within 7 days. The SRFs significantly (P = 0.05) reduced the herbicide mobility within the soil columns keeping a great portion of the herbicide active ingredient in the upper 5 cm soil layer. The SRFs were significantly (P = 0.05) as effective as the free technical herbicide in weed control without harming the ryegrass as the main plant. Therefore, the synthesized SRFs could be considered as useful tools for weed control in sustainable agriculture.     

单嘧磺酯的除草活性及其对玉米的安全性初探

用生物测定的方法比较了创制除草剂单嘧磺酯和其他几种磺酰脲类除草剂对稗草(Echinochloa phyllopogon(staf) Koss.)和苋菜(Acalypha australis L.)生长的影响,以明确其除草活性.盆栽试验结果表明,鲜重和株高是生物测定很好的指标,不同化学结构的磺酰脲类除草剂对杂草和作物生长的影响存在差异,单嘧磺酯对稗草和苋菜的生长有强烈的抑制作用,其除草活性与氯磺隆相当;室内研究结果表明,单嘧磺酯对玉米(Zea mayz L.)的安全性介于测定的几种磺酰脲类除草剂之间;田间试验结果表明,22.5 g·hm-2单嘧磺酯对当茬玉米的生长有一定的抑制作用,添加安全剂后,10%单嘧磺酯可湿性粉剂对玉米的出苗和生长以及产量均无显著影响.     

Nitrite and nitrate induced photodegradation of monolinuron in aqueous solution

Here we evidenced the photo-induced degradation of monolinuron, a phenylurea herbicide, through the 300–450 nm light excitation of nitrite and nitrate species. The degradation pathways were compared to those obtained under direct photolysis at 254 nm. When using NO₃^– and NO₂^– as photoinducers, hydroxyphenyl-substituted photodegradation products were found to be formed specifically through the involvement of OH° radicals. NO^– and NO₂-phenyl substituted compounds were also observed as a result of the production of NO° and NO₂° radicals. Half-lives of monolinuron in aqueous solutions were measured in various conditions of concentrations of substrate and inducer, oxygen content and pH.