磺酰脲类除草剂的残留分析

磺酰脲类除草剂是一类新型超高效除草剂，大约包括２Ｖ化合物，已被广泛用于禾谷作物防除阔叶杂草以及某些禾本科杂草，该类除草剂在环境中的残留浓度〈１μｇ．ｋｇ＾－１水平。常规的分析方法包括生物鉴定，酶免疫分析，气相色谱法和高效液相色谱法（ＨＰＬＣ）、ＨＰＬＣ／ＭＳ联用后，可以准确测定复杂环境样中磺酰脲类除草剂的痕量残留。     

磺酰脲类除草剂在硅胶G表面的光解

应用高效薄层析方法研究了苄嘧磺隆，甲磺隆，氯磺隆，氯嘧磺隆4种磺酰脲类除草剂在氙灯与太阳光下的光解动力学，以及8种有机色素对苄嘧磺隆光降解的影响。结果表明4种除草剂在硅胶G表面的降解呈一级动力学反应；有机色素对除草剂的降解均表现显著的猝灭效应。其中以姜黄素的猝灭作用最强，色素剂量与光解中的猝灭效应存在着显著的相关性。色素剂量加大，猝灭效应加强。     

Best Management Practices for Silvicultural Chemicals and the Science Behind Them

Silvicultural chemicals include fertilizers and pesticides applied for forest management. All states east of the Rockies have at least some form of silvicultural chemical best management practices (SCBMPs) and it is widely accepted that SCBMPs effect some protection of water quality. All SCBMPs recommend handling and application precautions and a minimum width streamside management zone (SMZ) on each side of streams for protection of water quality and aquatic ecosystems. Typically these zones increase in width as stream width increases. In areas where cold-water fish are present, additional widths are designated for their protection. Minimum SMZ widths range from 8 to 91 meters on each side of the stream bank for intermittent and perennial streams. Most SMZ recommendations do not cover ephemeral drainages, ditches or canals. SMZs are generally described as being site specific with width dependent on slope, soil type and other conditions as well as the stream's designation as perennial or intermittent. The science behind SCBMPs is often elusive. Spray drift can be controlled through proper selection and use of application technology while considering site specific conditions. SMZs greatly reduce the amount of herbicides reaching streams. Available toxicological data and research on aquatic ecosystem impacts from herbicide use suggest that additional protection from silvicultural chemicals may not be necessary. However, there is evidence to suggest that protection of ephemeral and intermittent channels can further reduce entry of silvicultural chemicals into streams and also reduce sedimentation. This may be the most fruitful area of research we can pursue in light of the knowledge gaps listed.     

Metabolites of the phenylurea herbicides chlorotoluron, diuron, isoproturon and linuron produced by the soil fungus Mortierella sp.

Phenylurea herbicides are used worldwide, and often pollute surface- and groundwater in concentrations exceeding the limit value for drinking water (0.1 μg l⁻¹). Bacteria degrade phenylurea herbicides by successive N-dealkylation to substituted aniline products. Little is known about the corresponding fungal pathways, however. We here report degradation of chlorotoluron, diuron, isoproturon and linuron by the soil fungus Mortierella sp. Gr4. Degradation was fastest with linuron and resulted in successively dealkylated metabolites and 3,4-dichloroaniline. A major new metabolite was detected that has not yet been fully identified. Thin layer chromatography and nuclear magnetic resonance spectroscopy indicate that it is a non-aromatic diol. Degradation of isoproturon, chlorotoluron and diuron involved successive N-demethylation and, in the case of isoproturon and chlorotoluron, additional hydroxylation. A new hydroxylated isoproturon metabolite was detected. The study thus shows that the fungal pathways differ from the bacterial pathways and yield new metabolites of possible environmental concern.     

高效液相色谱法测定土壤中三嗪类除草剂

建立了索氏提取、中性氧化铝小柱净化、高效液相色谱二极管阵列检测器测定土壤中7种三嗪类除草剂的方法,优化了检测波长、提取方法和溶剂、梯度淋洗程序等试验条件。7种三嗪类除草剂在0．10mg／L～2．00mg／L范围内线性良好,检出限为0．84μg／kg～2．07μg／kg,RSD为1．2％～5．6％,加标回收率为95.0％～107％。     

高效液相色谱法测定水中7种三嗪类除草剂

采用液液萃取和固相萃取两种方法预处理,高效液相色谱二极管阵列检测器测定水中7种三嗪类除草剂,选择了合适的检测波长和梯度淋洗条件。方法在0.100 mg/L~2.00 mg/L范围内线性良好,检出限为0.06μg/L~0.15μg/L,水样平行测定的RSD为1.6%~6.5%,加标回收率为95.0%~106%。     

The impact of pesticides on oxidative stress level in human organism and their activity as an endocrine disruptor

Pesticides cause serious environmental and health problems both to humans and animals. The aim of this review is to discuss selected herbicides and fungicides regarding their mode of action and their influence on basic oxidative stress parameters and endocrine disruption properties tested in selected cell cultures in vitro. Because of numerous difficulties which animal studies are subject to, cell cultures are an excellent experimental model reflecting human exposure to different pesticides through all relevant routes. This experimental model can be used to monitor aggregate and cumulative pesticide exposures.     

Effects of glyphosate and foliar amendments on activity of microorganisms in the soybean rhizosphere

A field study was conducted to determine the effects of glyphosate on microbial activity in the rhizosphere of glyphosate-resistant (GR) soybean and to evaluate interactions with foliar amendments. Glyphosate at 0.84 kg ae ha^{? 1} was applied GR soybean at the V4–V5 development stages. Check treatments included a conventional herbicide tank mix (2003 study only) and no herbicides (hand-weeded). Ten days after herbicide application, a commercially available biostimulant and a urea solution (21.0% N) were applied to soybean foliage at 33.5 mL ha^{? 1} and 9.2 kg ha^{? 1}, respectively. Soil and plant samples were taken 0, 5, 10, 15, 20 and 25 days after herbicide application then assayed for enzyme and respiration activities. Soil respiration and enzyme activity increased with glyphosate and foliar amendment applications during the 2002 growing season; however, similar increases were not observed in 2003. Contrasting cumulative rainfall between 2002 and 2003 likely accounted for differences in soil microbial activities. Increases in soil microbial activity in 2002 suggest that adequate soil water and glyphosate application acted together to increase microbial activity. Our study suggests that general soil microbial properties including those involving C and N transformations are not sensitive enough to detect effects of glyphosate on rhizosphere microbial activity. Measurements of soil-plant-microbe relationships including specific microbial groups (i.e., root-associated Fusarium spp.) are likely better indicators of impacts of glyphosate on soil microbial ecology.     

Photocatalytic degradation of five sulfonylurea herbicides in aqueous semiconductor suspensions under natural sunlight

In the present study, the photocatalytic degradation of five sulfonylurea herbicides (chlorsulfuron, flazasulfuron, nicosulfuron, sulfosulfuron and triasulfuron) has been investigated in aqueous suspensions of zinc oxide (ZnO), tungsten (VI) oxide (WO₃), tin (IV) oxide (SnO₂) and zinc sulfide (ZnS) at pilot plant scale under natural sunlight. Photocatalytic experiments, especially those involving ZnO photocatalysis, showed that the addition of semiconductors in tandem with the oxidant (Na₂S₂O₈) strongly enhances the degradation rate of the herbicides in comparisons carried out with photolytic tests. The degradation of the herbicides follows a first order kinetics according to the Langmuir-Hinshelwood model. In our conditions, the amount of time required for 50% of the initial pesticide concentration to dissipate (t_½) ranged from 8 to 27 min (t_30W = 0.3-1.2 min) for sulfosulfuron and chlorsulfuron, respectively in the ZnO/Na₂S₂O₈ system. None of the studied herbicides was found after 120 min of illumination (except chlorsulfuron, 0.2 μg L⁻¹).     

Bioherbicidal activity of terpenes and phenylpropenes against Echinochloa crus-galli

Abstract

This study was undertaken to evaluate the herbicidal activity of twelve natural compounds belonging to monoterpenes, phenylpropenes, and sesquiterpenes against Echinochloa crus-galli under laboratory and glasshouse conditions. Experiments were conducted to determine the impact of different concentrations (0.5, 1, 2, 4 and 8?mM) of these compounds on the seed germination and root and shoot growth of barnyard grass. trans-Cinnamaldehyde, eugenol, and thymol caused the highest impact on barnyard grass reducing its seed germination and shoot growth. p-Cymene (EC₅₀ = 0.22?mM) and trans-cinnamaldehyde (EC₅₀ = 0.34?mM) were the most potent compounds in limiting the root growth of the E. crus-galli. In a post-emergent experiment, thymol, trans-cinnamaldehyde, eugenol, farnesol, and nerolidol significantly reduced the shoot growth, fresh and dry weight of two-leaf stage barnyard grass after 2 days of the foliar treatment with the concentrations of 0.5, 1.0 and 2.0%. These compounds induced severe visible injury symptoms where trans-cinnamaldehyde, eugenol, farnesol and nerolidol showed a complete weed control at 1.0 and 2.0%. These compounds were successfully formulated as emulsifiable concentrates and showed higher herbicidal activities against barnyard grass. Altogether, our data showed that trans-cinnamaldehyde, eugenol, thymol, farnesol, and nerolidol can be developed as novel bioherbicides for managing E. crus-galli.