杀虫剂类POPs对土壤中微生物群落多样性的影响

农药类持久性有机污染物(POPs)如DDT和HCH在我国2 0世纪5 0年代到80年代曾广泛使用,在停止使用2 0 a后,在土壤中仍然可以检测到DDT和HCH的残留。利用BIOL OG微平板研究土壤微生物群落功能多样性,意在反映有机氯杀虫剂类POPs对土壤微生物群落多样性的影响。结果表明,加了HCH后土壤微生物群落的颜色平均变化值(AWCD)的变化速度和最终能达到的AWCD值要高于空白土壤,并且随着农药浓度的加大,AWCD值的变化速率也越来越快,最终能达到的最大值也呈比例增大。加了DDT后的土壤与空白土壤的AWCD变化速度和程度相差不大。方差分析结果表明:空白土壤、HCH0 .5mg/kg、HCH1.5 mg/kg各处理间土壤的AWCD值有显著性差异(p<0 .0 1) ,空白土壤、DDT0 .5 m g/kg、DDT1.5 m g/kg各处理间土壤的AWCD值达不到显著性差异的水平(p>0 .0 5 ) ,表层土壤的AWCD值要高于第2层土壤(p<0 .0 1)。从多样性指数的变化来看,当加入到土壤中的DDT和HCH含量稍低时,微生物会利用农药为碳源进行分解作用,从而刺激了微生物的生长,这时表现出丰富度、均匀性和多样性都呈增长趋势。但当农药的浓度进一步加大时,反而会抑制某些种的微生物生长,另外一些种则对加入到土壤中的农药有一定的耐受性,从而表现出群落的均匀性下降,而丰富度升高。在相同施用浓     

Stability and Effects of Some Pesticides in Soil

The influence of 29 pesticides on CO(2) production and nitrification by soil microorganisms was determined. A few compounds were stable but without significant effect in soil (chlorinated hydrocarbons), some persisted and depressed respiration and nitrification (carbamates, cyclodienes, phenylureas, thiolcarbamates), and others displayed toxicity but were transformed by soil microorganisms (amides, anilides, organophosphates, phenylcarbamates, triazines). Some compounds of the last type induced an initial increase and subsequent decrease in CO(2) production by soil. No simple explanation of this effect is possible, but the results of studies of model systems having established activities suggest that in soil any one or a combination of the following mechanisms is responsible for the observed complex relation of CO(2) production to time: (i) a pesticide acts to uncouple oxidative phosphorylation in a manner analogous to 2,4-dinitrophenol; (ii) a pesticide lacking antimicrobial action is oxidized in part and transformed to a stable and toxic product; (iii) a pesticide that is selectively toxic inhibits CO(2) production by sensitive microorganisms but is subject to oxidation without detoxification by other members of the microbial population that are resistant to its initial action. Pesticide concentrations greatly in excess of those recommended for agricultural and home use were required to produce an effect, and supplementary organic matter (glucose) tended to reduce pesticide toxicity and increase the microbial degradation of pesticides in soil.     

Pesticide relevance and their microbial degradation: a-state-of-art

The extensive use of pesticide causes imbalance in properties of soil, water and air environments due to having problem of natural degradation. Such chemicals create diverse environmental problem via biomagnifications. Currently, microbial degradation is one of the important techniques for amputation and degradation of pesticide from agricultural soils. Some studies have reported that the genetically modified microorganism has ability to degrade specific pesticide but problem is that they cannot introduce in the field because they cause some other environmental problems. Only combined microbial consortia of indigenous and naturally occurring microbes isolated from particular contaminated environment have ability to degrade pesticides at faster rate. The bioaugumentation processes like addition of necessary nutrients or organic matter are required to speed up the rate of degradation of a contaminant by the indigenous microbes. The use of indigenous microbial strains having plant growth activities is ecologically superior over the chemical methods. In this review, we have attempted to discuss the recent challenge of pesticide problem in soil environment and their biodegradation with the help of effective indigenous pesticides degrading microorganisms. Further, we highlighted and explored the molecular mechanism for the pesticide degradation in soil with effective indigenous microbial consortium. This review suggests that the use of pesticide degrading microbial consortia which is an eco-friendly technology may be suitable for the sustainable agriculture production.     

Effect of propanil,linuron, and dicamba on the degradation kinetics of 2,4‐dichlorophenoxyacetic acid by Burkholderia sp. A study by differential analysis of 2,4‐dichlorophenoxyacetic acid degradation data

The successive application of distinct pesticides, or mixtures of them, is a frequent practice that could adversely affect the microbial species inhabiting soil and aquatic ecosystems. The ability of soil or aquatic microbiota to degrade a pesticide could be affected by the presence of another. If the degradation rate of the first compound is inhibited, its dissipation half‐life in the environment could be hazardously enlarged. Few studies have been made to quantify the impact on the biodegradation rate of pesticides in soils or water by the presence of other pesticides. In this work, a method for assessing the effect of a pesticide on the biodegradation rate of another, measuring its effect on the biodegradation kinetics of a single bacterial strain is presented. The mathematical analysis is a powerful tool to study the stoichiometry and kinetics of microbial processes, which was used to evaluate independently, in detail, the effect of three pesticides (propanil, linuron, and dicamba) on the biodegradation kinetics of 2,4‐dichlorophenoxyacetic acid by a strain of Burkholderia sp. It was evidenced that linuron and dicamba caused a decay of more than 40% in the top instantaneous degradation rate of 2,4‐dichlorophenoxyacetic acid, while propanil showed a minimal effect.     

Impact of pesticides on soil microbiological parameters and possible bioremediation strategies

Intensive agriculture is spectacularly successful since last couple of decades due to the inputs viz; fertilizers and pesticides along with high yielding varieties. The mandate for agriculture development was to feed and adequate nutrition supply to the expanding population by side the agriculture would be entering to into new area of commercial and export orientation. The attention of public health and proper utilization natural resources are also the main issues related with agriculture development. Concern for pesticide contamination in the environment in the current context of pesticide use has assumed great importance [1]. The fate of the pesticides in the soil environment in respect of pest control efficacy, non-target organism exposure and offsite mobility has been given due consideration [2]. Kinetics and pathways of degradation depend on abiotic and biotic factors [6], which are specific to a particular pesticide and therefore find preference. Adverse effect of pesticidal chemicals on soil microorganisms [3], may affect soil fertility [4] becomes a foreign chemicals major issue. Soil microorganisms show an early warning about soil disturbances by foreign chemicals than any other parameters. But the fate and behavior of these chemicals in soil ecosystem is very important since they are degraded by various factors and have the potential to be in the soil, water etc. So it is indispensable to monitor the persistence, degradation of pesticides in soil and is also necessary to study the effect of pesticide on the soil quality or soil health by in depth studies on soil microbial activity. The removal of metabolites or degraded products should be removed from soil and it has now a day’s primary concern to the environmentalist. Toxicity or the contamination of pesticides can be reduced by the bioremediation process which involves the uses of microbes or plants. Either they degrade or use the pesticides by various co metabolic processes.     

Stability of bacterial populations in tropical soil upon exposure to Lindane

The effect of the pesticide Lindane on microbial populations was analyzed in soil with a history of contamination with various chemicals, including this pesticide. Soil microcosms were amended with 100 mg Lindane/kg soil and microbial populations were monitored for 70 days. Bacterial cell concentrations, metabolic versatility (whole community Biolog), and genetic diversity (16S rDNA/denaturing gradient gel electrophoresis) were used to monitor microbial communities. Results show the persistence of Lindane in the soil environment; at the end of the experiment, 70% of the added Lindane remained undegraded. A reduction of 50% in bacterial cell concentration was observed in Lindane-amended microcosms during the 2nd week of the experiment. This reduction was correlated with a reduction in the rate of substrate utilization as observed by Biolog. Overall, no effect of Lindane was observed on the metabolic versatility and genetic diversity in these soils, demonstrating the ability of these bacterial populations to tolerate the pressure caused by the addition of pesticides.     

Do Botanical Pesticides Alter the Structure of the Soil Microbial Community?

The effects of synthetic pesticides on the soil microbial community have been thoroughly investigated in the past mostly by culture-dependent methods and only few recent studies have used culture-independent approaches for this purpose. However, it should be noted that most of these studies have been conducted in microcosms where the soil microbial community is exposed to unrealistic concentrations of the pesticides, providing an unrealistic exposure scheme for soil microorganism. On the other hand, little is known regarding the potential impact of botanical pesticides on the soil microbial community. Therefore, a laboratory study and a field study were conducted to investigate the effects of synthetic (metham sodium [MS], sodium tetrathiocarbonate [SoTe], and fosthiazate) and botanical pesticides (azadirachtin, quillaja, and pulverized Melia azedarach fruits [PMF]) on the soil microbial community using phospholipid fatty acids (PLFA) analysis. Principal component analysis (PCA) on the results of the laboratory study indicated that the application of PMF resulted in significant changes in the soil microbial community. This was obvious by the proportional increase in the abundance of fatty acids 18:1ω9cis, 18:1ω9trans, which are common in gram-negative bacteria and saprotrophic fungi, and 18:2ω6,9, which is a fungal indicator. This response was attributed to the release of copious amounts of organic carbon and nutrients in the soil by the PMF. On the other hand, MS inhibited fungi and gram-negative bacteria, while fosthiazate and the botanical pesticides quillaja and azadirachtin did not impose significant changes in the soil microbial community. Similar results were obtained by the field study where application of the fumigants MS and SoTe significantly altered the structure of the soil microbial community with the former having a more prominent effect. Fosthiazate imposed mild changes in the soil microbial community, whereas quillaja and azadirachtin again did not show a significant effect. Overall, botanical pesticides, at their recommended dose, did not alter the structure of the soil microbial community compared to synthetic nonfumigant and fumigant pesticides which induced significant changes.     

农药污染对土壤微生物群落功能多样性的影响

根据95种不同的单一联底物上的BIOLOGGN微平板系统的反应所构造的多样性指数，结果表明农药严重污染的土壤微生物群落的Shannon指数和均度、Simpson指数、Mclntosh指数和均度均显著低于无污染的对照。说明农药严重污染导致土壤微生物群落功能多样性的下降，减少了能利用有关碳底物的微生物的数量，降低微生物对单一碳底物的利用能力。     

植物-微生物联合修复毒死蜱污染的土壤

本试验以毒死蜱污染土壤为研究材料,利用降解菌DSP-A分别与高丹草、紫花苜蓿、多花黑麦草进行联合修复,探讨了植物-微生物联合修复毒死蜱污染土壤的效果,以及影响联合修复的因素,结果表明,植物．微生物联合修复的效果优于单一的植物修复及单一的微生物修复效果。与DSP—A菌群较合适的植物是高丹草,该组合对毒死蜱的降解率达到96．44％,其次是多花黑麦草。研究了微生物数量、植株密度以及土壤湿度对联合修复效果的影响,结果表明,DSP．A菌菌液稀释倍数越大,联合修复的效果越差。植株密度对联合修复的影响,主要表现为对植物根系生长的影响。植株密度越大,对生存环境的竞争越激烈,植物根系的生长越不好。除了紫花苜蓿外,高丹草和多花黑麦草根系的生长均受到影响。高丹草种植密度为12株／盆时,与DSP—A菌的联合修复效果最好,多花黑麦草则为10株／盆。土壤湿度是影响联合修复的重要因素,不仅影响植物的生长,对微生物的生长也有影响。土壤湿度过大,造成土壤的含氧量降低,不利于植物根系和好氧细菌的生长,从而影响土壤中农药的降解。土壤湿度过小,容易造成植株缺水,根系生长和微生物的生长。高丹草与DSP．A菌、多花黑麦草与DSP—A菌联合修复最适浇水量都为20mL／d,紫花苜蓿与DSP—A菌联合修复最适浇水量都为15mL／d。     

Micro-scale modeling of pesticide degradation coupled to carbon turnover in the detritusphere: model description and sensitivity analysis

Microbiologically active biogeochemical interfaces are excellent systems to study soil functions such as pesticide degradation at the micro-scale. In particular, in the detritusphere pesticide degradation is accelerated by input of fresh organic carbon from litter into the adjacent soil. This observed priming effect suggests: (i) pesticide degradation is strongly coupled to carbon turnover, (ii) it is controlled by size and activity of the microbial community and (iii) sorption and transport of dissolved carbonaceous compounds and pesticides might regulate substrate availability and in turn decomposition processes. We present a new mechanistic 1D model (PEsticide degradation Coupled to CArbon turnover in the Detritusphere, PECCAD) which implements these hypotheses. The new model explicitly considers growth and activity of bacteria, fungi and specific pesticide degraders in response to substrate availability. Enhanced pesticide degradation due to availability of a second source of carbon (dissolved organic carbon) is implemented in the model structure via two mechanisms. First, additional substrate is utilized simultaneously with the pesticide by bacterial pesticide degraders resulting in an increase in their size and activity. Second, stimulation of fungal growth and activity by additional substrates leads directly to higher pesticide degradation via co-metabolism. Thus, PECCAD implicitly accounts for litter-stimulated production and activity of unspecific fungal enzymes responsible for co-metabolic pesticide degradation. With a global sensitivity analysis we identified high-leverage model parameters and input. In combination with appropriate experimental data, PECCAD can serve as a tool to elucidate regulation mechanisms of accelerated pesticide degradation in the detritusphere.     

Application of GMOs in the U.S.: EPA research & regulatory considerations related to soil systems

During the last 20 years recombinant biotechnology has resulted in the development of organisms with unique genetic compositions, some of which are for intentional release to the environment. While concerns have been raised that such organisms may be capable of inducing transient unintended environmental effects, longer-term perturbations to soil processes and non-target species effects have yet to be demonstrated. In parallel with the growth of the commercial biotechnology industry has come a significant growth in regulatory review processes intended to evaluate the risks of these GMO products. Under the Toxic Substances Control Act (TSCA), certain new microbial products that undergo pre-manufacture review are examined for human and environmental risks using data and other information received in accordance with the U.S. Environmental Protection Agency’s (EPA’s) “Points to Consider” guidance document. In the risk assessment process, carried out under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) and the Federal Food, Drug and Cosmetic Act (FFDCA) authorities, EPA evaluates both microbial pesticide products and plants with pesticidal properties to determine if Federal safety standards are met. For all pesticide products, including genetically engineered pesticides, EPA receives testing of product composition and chemical properties, human health effects, environmental effects on non-target pests, and the fate of the pesticide in the environment. The EPA’s Office of Research and Development supports risk assessment research related to such GMO products. This paper focuses on relevant EPA research and regulatory examples related to soil effects considerations for GMOs.     

Development,registration and commercialization of microbial pesticides for plant protection

Plant protection against pathogens, pests and weeds has been progressively reoriented from a therapeutic approach to a rational use of pesticide chemicals in which consumer health and environmental preservation prevail over any other productive or economic considerations. Microbial pesticides are being introduced in this new scenario of crop protection and currently several beneficial microorganisms are the active ingredients of a new generation of microbial pesticides or the basis for many natural products of microbial origin. The development of a microbial pesticide requires several steps addressed to its isolation in pure culture and screening by means of efficacy bioassays performed in vitro, ex vivo, in vivo, or in pilot trials under real conditions of application (field, greenhouse, post-harvest). For the commercial delivery of a microbial pesticide, the biocontrol agent must be produced at an industrial scale (fermentation), preserved for storage and formulated by means of biocompatible additives to increase survival and to improve the application and stability of the final product. Despite the relative high number of patents for biopesticides, only a few of them have materialized in a register for agricultural use. The excessive specificity in most cases and biosafety or environmental concerns in others are major limiting factors. Non-target effects may be possible in particular cases, such as displacement of beneficial microorganisms, allergenicity, toxinogencity (production of secondary metabolites toxic to plants, animals, or humans), pathogenicity (to plants or animals) by the agent itself or due to contaminants, or horizontal gene transfer of these characteristics to non-target microorganisms. However, these non-target effects should not be evaluated in an absolute manner, but relative to chemical control or the absence of any control of the target disease (for example, toxins derived from the pathogen). Consumer concerns about live microbes due to emerging food-borne diseases and bioterrorism do not help to create a socially receptive environment to microbial pesticides. The future of microbial pesticides is not only in developing new active ingredients based on microorganisms beneficial to plants, but in producing self-protected plants (so-called plant-incorporated pesticides) by transforming agronomically high-value crop plants with genes from biological control agents     

Evaluation of Sampling Strategies for Pesticides in a Macroporous Sandy Loam Soil

It is not straightforward to sample and demonstrate the presence and transport of pesticides in heterogeneous soil. Following leaching experiments with four differently structured 50-cm-long soil columns (tilled and untilled soil), the objective of this study was to investigate the extent that visual tracing of the dye Brilliant Blue could support in soil sampling for two strongly sorbing pesticides (¹⁴C-labeled glyphosate and pendimethalin). About 830 samples were collected. No pesticide was found below 10– 25 cm depth by random sampling, even though 0.21–0.31% of the applied amounts were leached, and 0.18% of the soil volume was sampled. With similar sampling efforts, the pesticides could generally be traced throughout the columns by sampling from stained soil volumes, only. None of the two particular sampling strategies for pesticides produced accurate mass balances or balances that were obviously better than the other. No pesticide was detected outside stained soil volumes, except for glyphosate in one sample. Below 30 cm, stained soil comprized on average 5% of the total soil volume, leaving 95% as expectedly pesticide-free. The results suggest that much more efficient sampling for sorbing pesticides can be obtained by using the dye and focusing on stained soil volumes.     

Adjustments of the Pesticide Risk Index Used in Environmental Policy in Flanders

Indicators are used to quantify the pressure of pesticides on the environment. Pesticide risk indicators typically require weighting environmental exposure by a no effect concentration. An indicator based on spread equivalents (ΣSeq) is used in environmental policy in Flanders (Belgium). The pesticide risk for aquatic life is estimated by weighting active ingredient usage by the ratio of their maximum allowable concentration and their soil halflife. Accurate estimates of total pesticide usage in the region are essential in such calculations. Up to 2012, the environmental impact of pesticides was estimated on sales figures provided by the Federal Government. Since 2013, pesticide use is calculated based on results from the Farm Accountancy Data Network (FADN). The estimation of pesticide use was supplemented with data for non-agricultural use based on sales figures of amateur use provided by industry and data obtained from public services. The Seq-indicator was modified to better reflect reality. This method was applied for the period 2009-2012 and showed differences between estimated use and sales figures of pesticides. The estimated use of pesticides based on accountancy data is more accurate compared to sales figures. This approach resulted in a better view on pesticide use and its respective environmental impact in Flanders.     

2,4-D impact on bacterial communities, and the activity and genetic potential of 2,4-D degrading communities in soil

The key role of telluric microorganisms in pesticide degradation is well recognized but the possible relationships between the biodiversity of soil microbial communities and their functions still remain poorly documented. If microorganisms influence the fate of pesticides, pesticide application may reciprocally affect soil microorganisms. The objective of our work was to estimate the impact of 2,4-D application on the genetic structure of bacterial communities and the 2,4-D-degrading genetic potential in relation to 2,4-D mineralization. Experiments combined isotope measurements with molecular analyses. The impact of 2,4-D on soil bacterial populations was followed with ribosomal intergenic spacer analysis. The 2,4-D degrading genetic potential was estimated by real-time PCR targeted on tfdA sequences coding an enzyme specifically involved in 2,4-D mineralization. The genetic structure of bacterial communities was significantly modified in response to 2,4-D application, but only during the intense phase of 2,4-D biodegradation. This effect disappeared 7 days after the treatment. The 2,4-D degrading genetic potential increased rapidly following 2,4-D application. There was a concomitant increase between the tfdA copy number and the 14C microbial biomass. The maximum of tfdA sequences corresponded to the maximum rate of 2,4-D mineralization. In this soil, 2,4-D degrading microbial communities seem preferentially to use the tfd pathway to degrade 2,4-D.     

Pesticide desorption from soils facilitated by dissolved organic matter coming from composts: experimental data and modelling approach

Dissolved organic matter (DOM) interaction with pesticides was examined studying the ability of DOM to desorb 8 pesticides previously sorbed to soil. DOM was originating from municipal waste composts at two maturity degrees, recovered at 20°C and by hot-pressurised subcritical water. Pesticide desorption depended on their previous sorption on soil. When sorption was low (K_OC ≤ 50, sulcotrione, metalaxyl), water was more efficient than DOM for desorption. On the contrary, when sorption was high (K_OC ≥ 2000, trifluraline), little effect of DOM was observed. For the moderately sorbed pesticides, DOM favoured pesticide desorption compared to water. For the lowest sorbed pesticides (K_OC ≤ 100), hysteresis was increased with larger proportions of DOM extracted with subcritical-water. Dissolved organic matter extracted from fresh-immature compost had larger capacity to mobilize the sorbed pesticides than the DOM from the mature compost. The pesticide desorption resulted from the positive and competitive interactions between pesticide, DOM and soil surfaces. These interactions were modelled considering separate partitioning coefficients. A general equation allowed the deduction of specific coefficients describing interactions in solution between pesticides and the non-sorbed fraction of DOM remaining in solution. This fraction was supposed to contain the most hydrophilic fraction of DOM and was able to interact with the most polar pesticide (amitrol). When pesticide hydrophobicity increased, the partitioning between pesticide and DOM decreased. Modelling the three-phase system (liquid, DOM and solid phases) pointed out that the solid phase played the most important role on pesticide behaviour through the sorption process of DOM and pesticides.     

Impact of Polyacrylamide Treatment on Sorptive Dynamics and Degradation of 2,4-D and Atrazine in Agricultural Soil

High-molecular-weight, anionic polyacrylamide (PAM) is added to irrigation water to reduce soil erosion during furrow irrigation of crops. The chemical nature of PAM, together with the observation that the polymer can be biotransformed by soil bacteria, led us to question the impact of PAM treatment on the fate of coapplied agrochemicals. The herbicides, atrazine (nonionic) and 2,4-D (anionic), were tested for pesticide sorption, desorption, and degradation in PAM-treated and untreated soils. Sorption of atrazine and 2,4-D in soil was unaffected by PAMtreatment, as was atrazine desorption. However, 2,4-D desorbedmore readily from the PAM-treated soil than from untreated soil. With respect to pesticide degradation, mineralization of the 2,4-D aromatic ring was not impacted by PAM treatment, but decarboxylation of the 2,4-D carboxylic acid side chain was significantly reduced in the PAM-treated soil. Limited mineralization (7 to 10%) of atrazine was observed in both soils. However, in PAM-treated soils atrazine conversion to ¹⁴CO₂ and bound residue components was significantly reduced, and there was an increase in the level of methanol extractable metabolites. These results may indicate that PAM application can alter the environmental fate of some pesticides in soils, especially under the high dose treatment conditions examined in this study.     

A model study of pesticide biodegradation in soil

This study addresses the efficiency of microbial preparations to degrade pesticide residues in soil. A method to degrade pesticides DNOC and pendimethalin using Pseudomonas and Arthrobacter bacteria with a fertilizer is described.