Runoff and leaching of atrazine and alachlor on a sandy soil as affected by application in sprinkler irrigation

Abstract

Rainfall simulation was used with small packed boxes of soil to compare runoff of herbicides applied by conventional spray and injection into sprinkler‐irrigation (chemigation), under severe rainfall conditions. It was hypothesized that the larger water volumes used in chemigation would leach some of the chemicals out of the soil surface rainfall interaction zone, and thus reduce the amounts of herbicides available for runoff. A 47‐mm rain falling in a 2‐hour event 24 hours after application of alachlor (2‐chloro‐N‐(2,6‐diethylphenyl)‐N‐(methoxymethyl)‐acetamide) and atrazine (6‐chloro‐N‐ethyl‐N‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine) was simulated. The design of the boxes allowed a measurement of pesticide concentrations in splash water throughout the rainfall event. Initial atrazine concentrations exceeding its’ solubility were observed. When the herbicides were applied in 64000 L/ha of water (simulating chemigation in 6.4 mm irrigation water) to the surface of a Tifton loamy sand, subsequent herbicide losses in runoff water were decreased by 90% for atrazine and 91% for alachlor, as compared to losses from applications in typical carrier water volumes of 187 L/ha. However, this difference was not due to an herbicide leaching effect but to a 96% decrease in the amount of runoff from the chemigated plots. Only 0.3 mm of runoff occurred from the chemigated boxes while 7.4 mm runoff occurred from the conventionally‐treated boxes, even though antecedent moisture was higher in the former. Two possible explanations for this unexpected result are (a) increased aggregate stability in the more moist condition, leading to less surface sealing during subsequent rainfall, or (b) a hydrophobic effect in the drier boxes. In the majority of these pans herbicide loss was much less in runoff than in leachate water. Thus, in this soil, application of these herbicides by chemigation would decrease their potential for pollution only in situations where runoff is a greater potential threat than leaching.     

Persistence of the herbicide butachlor in soil after repeated applications and its effects on soil microbial functional diversity

Effects of repeated applications of the herbicide butachlor (N-(butoxymethyl)-2-chloro -N-2′,6′-dimethyl acetanilide) in soil on its persistence and soil microbial functional diversity were investigated under laboratory conditions. The degradation half-lives of butachlor at the recommended dosage in soil were calculated to be 12.5, 4.5, and 3.2 days for the first, second, and third applications, respectively. Throughout this study, no significant inhibition of the Shannon-Wiener index H′ was observed. However, the Simpson index 1/D and McIntosh index U were significantly reduced (P ≤ 0.05) during the initial 3 days after the first application of butachlor, and thereafter gradually recovered to a similar level to that of the control soil. A similar variation but faster recovery in 1/D and U was observed after the second and third Butachlor applications. Therefore, repeated applications of butachlor led to more rapid degradation of the herbicide, and more rapid recovery of soil microorganisms. It is concluded that repeated butachlor applications in soil had a temporary or short-term inhibitory effect on soil microbial communities.     

Uptake,translocation, and control of trumpet flower (Tecoma stans) with aminocyclopyrachlor

To gain a better understanding of the physiology of the herbicide aminocyclopyrachlor in young plants of trumpet flower, the uptake and translocation were evaluated after the application of herbicide. This was determined by treating individual leaves with formulated herbicides plus ¹⁴C-aminocyclopyrachlor after the application of the formulated herbicide. This experiment used a randomized experimental design with three replications. In addition, field studies were conducted to assess the effectiveness of foliar applications of aminocyclopyrachlor in association with metsulfuton-methyl. The plant absorbed 20% of the herbicide applied. The translocation percentage did not surpass 5% of the total amount applied. Only 1% of the herbicide applied was translocated to the roots. Rate of 40 + 13 g a.i. 100 L^?1 of aminocyclopyrachlor+metsulfuron-methyl was effective to control T. stans.     

O3／UV预处理磺酰脲类除草剂生产废水的研究

采用O3／UV工艺预处理磺酰脲类除草剂生产废水,考察了初始pH值、臭氧投量、叔丁醇投加等因素对废水处理效果的影响,并初步探讨了该工艺处理废水的反应机理。实验结果表明,在废水初始pH为13．59和臭氧投量为65．08mg／min的条件下,预处理80min后废水COD去除率达63．47％,BOD5／COD由0．03提高至0．56,EC50从11％提高至55％。随着叔丁醇浓度的增加,废水COD去除率明显降低,证明该反应体系有·OH存在;体系中加入MnO2后废水COD去除率下降了16％,氧化效率明显下降,证明该反应体系内中间产物HO2O在O3／UV降解有机废水过程中起到了重要的作用。     

除草剂阿特拉津生物降解研究进展

本文综述了近年来国内外在阿特拉津降解菌及降解途径方面的研究进展 ,及在微生物产生的阿特拉津降解酶、其操作基因方面的研究现状 ,并提出了阿特拉津生物降解的研究趋势     

Transgenics and Vertebrate Cloning as Tools for Species Conservation

Abstract:  It has been suggested that transgenics and vertebrate cloning have a role to play in conservation. Now is the time to evaluate their risks and benefits, before these technologies are widely implemented in our field. Direct risks of transgenics include escape and introgression of transgenes into wild populations; weedy invasion by transgenic organisms; toxicity or pathogenicity of engineered organisms and their products; and human error in the field testing and tracking of transgenic organisms. Indirect risks include environmental effects of increased herbicide use; the danger that engineered organisms may aid the development of bioweapons; the likelihood that gene patenting will lead to the privatization of natural resources; and the diversion of support from less glamorous forms of conservation. Formal risk assessments are commonly used to evaluate transgenic procedures, but our incomplete understanding of both ecosystem processes and the action of transgenes renders most of these assessments scientifically and socially unjustified. Nevertheless, a few, low-risk applications of transgenics may be possible: for example, "super-sterile" ornamental cultivars. Vertebrate cloning poses little risk to the environment, but it can consume scarce conservation resources, and its chances of success in preserving species seem poor. To date, the conservation benefits of transgenics and vertebrate cloning remain entirely theoretical, but many of the risks are known and documented. Conservation biologists should devote their research and energies to the established methods of conservation, none of which require transgenics or vertebrate cloning.     

Quantifying hysteresis of atrazine desorption from a sandy loam soil

Batch experiments were carried out to investigate the effects of initial atrazine concentrations and consecutive desorption steps on the desorption characteristics of atrazine from a sandy loam soil.As initial atrazine concentration increased,the average percentage of atrazine desorption on the sandy loam soil ranged gradually from 23.1% to 38.5% after five consecutive desorption steps.The values of the Freundlich capacity parameter,kdes,derived from the initial concentration and time-dependent desorption isotherm were consistently higher than those associated with sorption.The opposite trend was observed only for the values of nonlinear parameter,ndes,from the initial concentration-dependent desorption isotherms.Atrazine hydrolysis to hydroxyatrazine and bound residue formation were mainly responsible for the observed hysteresis in its sorption and desorption isotherms.For the initial concentration-dependent desorption isotherms,as initial atrazine concentration increased,the values of hysteretic coefficients ω and λ decreased,and H values increased.However,the relationships between initial atrazine concentration and hysteretic coefficients were not pronounced for ω,H,or λ.For the time-dependent desorption isotherms,λ and H values increased as the atrazine desorption step proceeded.The correlation between hysteretic coefficient and desorption step was highly significant for λ (P 0.0001),but not for H.     

水中BPMC等残留农药的分析方法研究

BPMC、Propyzamide、TPN、Diazinon、IBP、MEP、Benthiocarb、Isoxathion、EPN等农药是目前广泛使用的除草剂和杀虫剂,其中部分农药如BPMC被列为毒害品,然而目前还没有可行有效的、针对以上物质的统一检测方法。选用了合适的有机溶剂对多种组分进行同时萃取,经过净化后采用气相色谱-质谱法测定,分析效果较好。     

Enantioselective separation and zebrafish embryo toxicity of insecticide beta-cypermethrin

Enantioselectivity of chiral pollutants is receiving growing concern due to the difference in toxicology and environment fate between enantiomers.In this study,enantiomers of insecticide beta-cypermethrin (beta-CP) were separated on selected chiral column by HPLC,and the toxicity of enantiomers was evaluated using the zebrafish embryo-larval assays.The enantiomers of beta-CP were baseline separated on Chiralcel OD and Chiralpak AD columns and detected by circular dichroism (CD) at 236 nm.Better separation could be achieved at lower temperature (e.g.,20°C) and with lower levels of polar modifiers.Pure enantiomers were obtained on Chiralcel OD.The CD spectra of enantiomers were recorded.By comparing the elution order with a previous similar study,the absolute configuration of beta-CP enantiomers was determined.The individual enantiomers were used in zebrafish embryo test,and the results showed that beta-CP enantioselectively induced yolk sac edema,pericardial edema and crooked body.The 1R-cis-αS and 1R-trans-αS enantiomers showed strong developmental toxicities at concentration of 0.1 mg/L,while the 1S-cis-αR and 1S-trans-αR induced no malformations at higher concentration (e.g.,0.3 mg/L).The results suggest that the enantioselective toxicological effects of beta-CP should be considered when evaluating its ecotoxicological effects.     

敌草快在水溶液中的光解动力学研究

常温常压条件下,用500 w高压汞灯和太阳光分别照射处理敌草快水溶液,考察光照和初始浓度对敌草快在水溶液中光降解的影响。研究表明,分别用500 w高压汞灯和太阳光照射下,敌草快的光解反应均符合一级动力学规律,降解半衰期分别为0.11 d和240.63 d;敌草快的初始浓度越大,其光解率越小,光解率与其初始浓度呈负相关。