Investigations of the determination and transformations of diazinon and malathion under environmental conditions using gas chromatography coupled with a flame ionisation detector

Degradation of two model insecticides, diazinon and malathion, and their degradation products 2-isopropyl-6-methyl-4-pyrimidinol--IMP (diazinon hydrolysis product) and malaoxon (malathion oxidation product) was compared and studied in the environment. The pesticides and their metabolites were extracted from samples (water, soil, chicory) with ethyl acetate and subsequently the extracts were analyzed by GC/FID. It was shown that hydrolysis is the major process in the degradation of these pesticides in water. In fact, 95% of diazinon was degraded, and only 10% of malathion was oxidised. In soil 30% of diazinon exposed to the sunlight was decomposed by photolysis, whereas in soil left in the darkness no degradation products were observed. In soil left under environmental conditions, 90% of diazinon was degraded and 40% from its initial concentration was transformed into IMP. The concentrations of the pesticides after 21 days on chicory were under maximal allowable concentration, which is 0.5 ppm for malathion and for diazinon. The concentration of malaoxon was more than twice as high as the allowable value, which is for the sum of malathion and malaoxon 3 ppm.     

Photodegradation of organophosphorus insecticides - investigations of products and their toxicity using gas chromatography-mass spectrometry and AChE-thermal lens spectrometric bioassay

Four organophosphorus compounds: azinphos-methyl, chlorpyrifos, malathion and malaoxon in aqueous solution were degraded by using a 125 W xenon parabolic lamp. Gas chromatography-mass spectrometry (GC-MS) was used to monitor the disappearance of starting compounds and formation of degradation products as a function of time. AChE-thermal lens spectrometric bioassay was employed to assess the toxicity of photoproducts. The photodegradation kinetics can be described by a first-order degradation curve C=C0e(-kt), resulting in the following half lives: 2.5min for azinphos-methyl, 11.6 min for malathion, 13.3 min for chlorpyrifos and 45.5 min for malaoxon, under given experimental conditions. During the photoprocess several intermediates were identified by GC-MS suggesting the pathway of OP degradation. The oxidation of chlorpyrifos results in the formation of chlorpyrifos-oxon as the main identified photoproduct. In case of malathion and azinphos-methyl the corresponding oxon analogues were not detected. The formation of diethyl (dimethoxy-phosphoryl) succinate in traces was observed during photodegradation of malaoxon and malathion. Several other photoproducts including trimethyl phosphate esters, which are known to be AChE inhibitors and 1,2,3-benzotriazin-4(3H)-one as a member of triazine compounds were identified in photodegraded samples of malathion, malaoxon, and azinphos-methyl. Based on this, two main degradation pathways can be proposed, both result of the (P-S-C) bond cleavage taking place at the side of leaving group. The enhanced inhibition of AChE observed with the TLS bioassay during the initial 30 min of photodegradation in case of all four OPs, confirmed the formation of toxic intermediates. With the continuation of irradiation, the AChE inhibition decreased, indicating that the formed toxic compounds were further degraded to AChE non-inhibiting products. The presented results demonstrate the importance of toxicity monitoring during the degradation of OPs in processes of waste water remediation, before releasing it into the environment.     

Effects of malathion and chlorpyrifos on acetylcholinesterase and antioxidant defense system in Oxya chinensis (Thunberg) (Orthoptera: Acrididae)

The study was undertaken to evaluate the effects of malathion and chlorpyrifos on acetylcholinesterase (AChE), esterase (EST) activity and antioxidant system after topical application with different concentration to Oxya chinensis. The results showed that malathion and chlorpyrifos inhibited EST, AChE activity and increased malondialdehyde (MDA) contents. A change in superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), glutathione peroxidase (GPx), and glutathione reductase (GR) activity combined with reduced glutathione (GSH) and total glutathione (tGSH) contents was found in O. chinensis after malathion and chlorpyrifos treatments. Malathion and chlorpyrifos increased SOD and CAT activity compared with the control. With the concentrations increasing, SOD and CAT activity showed the similar tendency, namely, SOD and CAT activity increased at the lower concentrations and decreased at the higher concentrations. The results showed that malathion and chlorpyrifos decreased significantly GR activity. GST and GPx activity at the studied concentrations of chlorpyrifos was lower than that of the control. However, no significance was observed. GPx and GST activity in malathion treated grasshoppers showed a biphasic response with an initial increase followed by a decline in its activity. Malathion and chlorpyrifos decreased GSH contents and the ratio of GSH/GSSG. The present findings indicated that the toxicity of malathion and chlorpyrifos might be associated with oxidative stress.     

Comparison of degradation studies in a biosimulator by continuous cultivation of Pseudomonas and indigenous microorganisms with varied dissolved oxygen concentrations

The aim of this study was to compare the potential of a pure bacterial culture of Pseudomonas with the potential of an indigenous microorganism for malathion degradation by continuous cultivation using two different sets of conditions (with-culture: Pseudomonas, and without-culture: indigenous microorganisms) at varied dissolved oxygen (DO) concentrations (4.0 and 8.0 mg/L) in a biosimulator. The samples were analysed for pH, DO and COD (unfiltered). Gas chromatography (GC) revealed that almost 90% of malathion removal was achieved within ten hours of treatment in both studies of with-culture using 4.0 and 8.0 mg/L DO, whereas COD was considerably reduced during the treatment process and the removal efficiency was found to be above 90% in both conditions. The removal of COD was found to be in direct relation to retention time. However, the unfiltered COD and malathion removal efficiency was significantly influenced by DO. The percentage degradation of malathion using 4.0 mg/L DO, with-culture after 10 hours was 90.01%, whereas after 51 hours it was 99.03%. The without-culture studies showed percentage values which were 38.29% after 10 hours, whereas the corresponding value after 51 hours was 96.84%. Similarly, the percentage degradation of malathion using 8.0 mg/L DO, with-culture studies revealed that almost 89.40% malathion degradation was achieved after 10 hours, whereas it was 96.91% after 51 hours after inoculation of the culture. However, for the without-culture studies the value after 10 hours was 52.34%, whereas 96.86% malathion degradation was achieved after 51 hours without added culture. Although no significant variation in the pH was observed during the study the pH values increased gradually during the treatment process in all of the conditions. A critical evaluation of data presented revealed that the degradation potential of Pseudomonas was better when compared to the degradation potential of indigenous microorganisms.     

Fungal degradation of metsulfuron-methyl in pure cultures and soil

A fungal strain capable of utilizing metsulfuron-methyl as sole carbon and energy sources was isolated from a metsulfuron-methyl treated soil. The degradation characteristics of metsulfuron-methyl by this fungal strain were investigated in liquid culture and soil. More than 79% of metsulfuron-methyl at concentrations of 0.10 mgl(-1), 1.0 mgl(-1) and 10.0 mgl(-1) in pure culture was degraded by strain MD after incubation for 7 days, whereas only 5.6%, 8.6% and 13.1% of metsulfuron-methyl were degraded at levels of 0.10 mgl(-1), 1.0mgl(-1) and 10.0 mgl(-1) in the controls, respectively. The incorporation of strain MD into soil was found to substantially increase the degradation of metsulfuron-methyl. Degradation was 7.5 and 3.8 times faster in strain MD amended soils than in sterilized and fresh soils. The results show that addition of the isolated strain MD enhances degradation of metsulfuron-methyl in water and soil.     

Kinetics and mechanism of TNT degradation in TiO2 photocatalysis

The photocatalytic degradation of TNT in a circular photocatalytic reactor, using a UV lamp as a light source and TiO(2) as a photocatalyst, was investigated. The effects of various parameters such as the initial TNT concentration, and the initial pH on the TNT degradation rate of TiO(2) photocatalysis were examined. In the presence of both UV light illumination and TiO(2) catalyst, TNT was more effectively degraded than with either UV or TiO(2) alone. The reaction rate was found to obey pseudo first-order kinetics represented by the Langmuir-Hinshelwood model. In the mineralization study, TNT (30 mg/l) photocatalytic degradation resulted in an approximately 80% TOC decrease after 150 min, and 10% of acetate and 57% of formate were produced as the organic intermediates, and were further degraded. NO(-)(3) NO(-)(2), and NH(+)(4) were detected as the nitrogen byproducts from photocatalysis and photolysis, and more than 50% of the total nitrogen was converted mainly to NO(-)(3)in the photocatalysis. However, NO(-)(3) did not adsorbed on the TiO(2) surface. TNT showed higher photocatalytic degradation efficiency at neutral and basic pH.     

Degradation of polychlorinated dibenzo-p-dioxins in aqueous solution by Fe(II)/H2O2/UV system

The photodegradation of polychlorinated dibenzo-p-dioxins (PCDDs), which include tetra- to octa-CDDs (TeCDD, PeCDD, HxCDD, HpCDD and OCDD), was carried out in the presence of Fe(II) and H2O2 mixed reagent. The degradation efficiency was strongly influenced by UV irradiation, and the initial concentrations of H2O2 and Fe(II). An initial TeCDD concentration of 10 ng l(-1) was completely degraded within 20 min under the optimum conditions. All PCDDs tested were successfully degraded by Fe(II)/H2O2/UV treatment and complete degradation of TeCDD, PeCDD and HxCDD was achieved within 120 min. PCDD photodegradation rates decreased with the number of chlorine atoms. The degradation process of TeCDD by this system seems to be initiated by an oxidative reaction (OH* radical attack) because less chlorinated DDs as intermediate products were not detected. From the Frontier electron density calculation, the first OH* radical attack positions on TeCDD were found to be four C atoms neighboring two O atoms. The decomposition of TeCDD gave 4,5-dichlorocatechol as an intermediate product. A TeCDD degradation scheme was proposed based on the identified intermediate and the values of Frontier electron density. Based on these results, Fe(II)/H2O2/UV system could be useful technology for the treatment of wastewater containing persistent pollutants such as dioxins and polychlorinated biphenyls.     

Aerobic degradation of diuron by aquatic microorganisms

Abstract

Degradation of diuron [3‐(3,4‐dichlorophenyl)‐l,1‐dimethyl‐urea] by microorganisms obtained from pond water and sediment was determined under aerobic conditions. Enrichment procedures were used to isolate cultures capable of degrading the herbicide. Several mixed fungal/bacterial and mixed bacterial cultures were isolated that could degrade diuron. The mixed cultures degraded 67–99% of the added diuron forming from six to seven products which were separated via TLC. The major degradation product detected in most culture extracts was 3,4‐dichloroaniline. Other identified products formed were 3‐(3,4‐dichlorophenyl)‐1‐methylurea and 3‐(3,4‐dichlorophenyl)urea.     

Photodegradation of quinestrol in waters and the transformation products by UV irradiation

Quinestrol is synthetic estrogen used in contraceptive and hormone replacement therapy and occasionally for treating breast cancer and prostate cancer. It can make its way into the environment through sewage discharge and waste disposal produced by human excretions. In this study, the photodegradation kinetics of quinestrol in various conditions was investigated by UV and solar irradiation. The affecting factors were studied including concentration of hydrogen peroxide, different water types, and the initial concentrations of quinestrol. Concurrently, the transformation products and presumed pathways of quinestrol in distilled water by UV irradiation were identified and proposed. The results showed that the degradation of quinestrol in both irradiation conditions followed the pseudo-first-order kinetics. More rapid degradation was observed by UV irradiation (k = 0.018 min⁻¹) than solar irradiation (k = 0.004 h⁻¹), and the photodegradation rate of quinestrol depended on the concentration of hydrogen peroxide, the initial concentration of quinestrol and water types. The transformation products of quinestrol in distilled water were identified by gas chromatography/mass spectrometry. When exposed to UV irradiation, quinestrol in aqueous solution was rapidly degraded, giving at least ten photodegradation products. The chemical structures of ten degradation products were identified on the basis of mass spectrum interpretation and literature data.     

Effects of prochloraz and malathion on the red-legged partridge: a semi-natural field study

A semi-natural field study was carried out to assess the likelihood of a potentiation of toxicity between the ergosterol biosynthesis inhibiting (EBI) fungicide, prochloraz, and the organophosphorus (OP) insecticide, malathion, in the red-legged partridge (Alectoris rufa). Groups of partridges kept in four large grassland enclosures were exposed to either prochloraz-treated or control wheat for 7 days after which two of the enclosures were sprayed with malathion whilst the remaining two were sham-sprayed. Cytochrome P-450, aldrin epoxidase and 7-ethoxyresorufin-O-deethylase (EROD) activities were found to be significantly higher in the group exposed to prochloraz alone compared to controls, suggesting that induction of the hepatic microsomal monooxygenase system had occurred by ingestion of prochloraz-treated wheat. However, the level of induction produced was not sufficient to cause a potentiation of malathion toxicity. There was evidence for induction of several forms of P-450 recognised by antibodies raised against 1A1, 2C6 and 4A1 in the prochloraz-exposed partridges.     

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.     

The degradation of chlorpyrifos and diazinon in aqueous solution by ultrasonic irradiation: effect of parameters and degradation pathway

In this paper, elimination of two types of organophosphorus pesticides (OPPs), chlorpyrifos and diazinon spiked in aqueous solution by ultrasonic irradiation was investigated. Results showed that chlorpyrifos and diazinon could be effectively and rapidly degraded by ultrasonic irradiation, and the degradation of both pesticides was strongly influenced by ultrasonic power, temperature and pH value. Furthermore, two and seven products for the degradation of chlorpyrifos and diazinon formed during ultrasonic irradiation have been identified by gas chromatography-mass spectrometry, respectively. The hydrolysis, oxidation, hydroxylation, dehydration and decarboxylation were deduced to contribute to the degradation reaction and the degradation pathway for each pesticide under ultrasonic irradiation was proposed. Finally, the toxicity evaluation indicated that the toxicity decreased for diazinon solution after ultrasonic irradiation, but it increased for chlorpyrifos solution. The detoxification of OPPs by ultrasonic irradiation was discriminative.     

Effect of selected pesticides and their ozonation by-products on gap junctional intercellular communication using rat liver epithelial cell lines.

The non-genotoxic effects of two commonly used pesticides, 1,1-bis (p-chlorophenyl)-2,2,2-trichloroethane (DDT) and malathion, and one widely used commercial insect repellent N,N-diethy-m-toluamide (DEET) on gap junction intercellular communication (GJIC) were determined using a rat liver epithelial cell line. Malathion and DDT reversibly inhibited GJIC in a treatment time- and dose-dependent manner at non-cytotoxic doses, whereas, DEET did not inhibit GJIC. Malathion was very reactive with ozone, while DEET and DDT did not react to any appreciable extent with ozone. The mixtures of ozonation products from malathion and DEET did not inhibit GJIC. The mixtures of ozonation by-products formed from DDT inhibited GJIC, but to a lesser extent than did DDT, itself. These results suggest that ozone can effectively remove malathion from solution without forming GJIC-toxic products, but is less effective in eliminating DEET and DDT from solution.     

Isolation and characterization of an Alcaligenes sp. strain DG-5 capable of degrading DDTs under aerobic conditions

In this study, an Alcaligenes sp. strain DG-5 that can effectively degrade dichlorodiphenyltrichloro-ethanes (DDTs) under aerobic conditions was isolated from DDTs-contaminated sediment. Various factors that affect the biodegradation of DDTs by DG-5 were investigated. About 88 %, 65 % and 45 % of the total DDTs were consumed within 120 h when their initial concentrations were 0.5, 5 and 15 mg L?1, respectively. However, almost no degradation was observed when their concentration was increased to 30 mg L?1, but the addition of nutrients significantly improved the degradation, and 66 % and 90 % of the total DDTs were degraded at 336 h in the presence of 5 g L?1 peptone and yeast extract, respectively. Moreover, the addition of 20 mM formate also enhanced the ability of DG-5 to transform DDTs, and its DDT transformation capacity (T(c)) value was increased by 1.8 - 2.7 fold for the pure (p,p'-DDT or o,p'-DDT only) and mixed systems (p,p'-DDT, o,p'-DDT, p,p'-DDD and p,p'-DDE). Furthermore, it was found that competitive inhibition in the biodegradation by DDT compounds occurred in the mixed system.     

微囊藻毒素-RR的提取和臭氧氧化降解

在对采自云南滇池水华蓝藻细胞中的微囊藻毒素-RR(microcystin-RR,MC-RR)提取并发现其含量达到0.19mg/g(干重)的基础上,重点研究了臭氧氧化降解所提取的MC-RR。结果表明,当反应体系中臭氧浓度为5.7 mg/L时,初始浓度1.9 mg/L的MC-RR在15 min内被完全降解。利用HPLC/ESI/MS对提取的MC-RR及其氧化降解产物质荷比测定发现,降解前MC-RR的质谱图中出现特征离子m/z=1 038.7、m/z=519.8以及m/z=135.0。而降解后的产物质谱图中只有Adda基团中带苯环结构化合物(C9H10O)的特征离子峰m/z=135.0存在,其他2个离子峰完全消失。由此推断反应体系中MC-RR(m/z=1 038.2)在大量臭氧及其.OH自由基全面攻击下,分子结构中Adda基团以及单环结构中的不饱和双键直接被氧化而发生断链,最终形成小分子的有机物。     

Degradation of telone II in contaminated and noncontaminated soils

Abstract

Degradation of the nematicide Telone II (cis‐ and trans‐1,3‐dichloropropene comprise the active ingredients) in soil was studied using ¹⁴C‐l,3‐dichloropropene (DCP) along with soil samples collected from a field test site near Quincy, Florida. A mixed bacterial culture isolated from the soil in the presence of a second carbon source, glucose or yeast extract, completely degraded ¹⁴C‐DCP to ¹⁴CO₂, water‐soluble products, and microbial mass. ¹⁴C‐DCP in soil was also degraded to ¹⁴CO₂. After 28 days of incubation, the labeled chemical was completely degraded to ¹⁴CO₂, water‐soluble metabolites, bound‐residues, and possibly some microbial mass. Little or no difference was observed in the degradation of ¹⁴C‐DCP in soil samples collected one week prior to field application of Telone II, or two weeks and two years after application.     

Protease production by the keratinolytic Bacillus sp. CL18 through feather bioprocessing

Bacillus sp. CL18 was investigated to propose a bioprocess for protease production using feathers as organic substrate. In feather broth (FB), containing feathers as sole organic substrate (1–100 g l^?1), maximal protease production was observed at 30 g l^?1 (FB30) after 6 days of cultivation, whereas increased feather concentrations negatively affected protease production and feather degradation. Protease production peaks were always observed earlier during cultivations than maximal feather degradation. In FB30, 80% of initial feathers mass were degraded after 7 days. Addition of glucose, sucrose, starch, yeast extract (2 g l^?1), CaCl₂, or MgCl₂ (10 mmol l^?1) to FB30 decreased protease production and feather degradation. FB30 supplementation with NH₄Cl (1 g l^?1) resulted in less apparent negative effects on protease production, whereas peptone (2 g l^?1) increased protease yields earlier during cultivations (3 days). Through a central composite design employed to investigate the effects of peptone and NH₄Cl (0.5–4.5 g l^?1) on protease production and feather degradation, FB30 supplementation with peptone and NH₄Cl (0.5–1.1 g l^?1) increased protease production within a shorter cultivation time (5 days) and hastened complete feather degradation (6 days). Feather bioconversion concurs with sustainable production of value-added products.

     

Reduction of the movement and persistence of pesticides in soil through common agronomic practices

Laboratory and field studies were conducted in order to determine the leaching potential of eight pesticides commonly used during pepper cultivation by use of disturbed soil columns and field lysimeters, respectively. Two soils with different organic matter content (soils A and B) were used. Additionally, soil B was amended with compost (sheep manure). The tested compounds were cypermethrin, chlorpyrifos-methyl, bifenthrin, chlorpyrifos, cyfluthrin, endosulfan, malathion and tolclofos-methyl. In soil B (lower organic matter content), only endosulfan sulphate, malathion and tolclofos-methyl were found in leachates. For the soil A (higher organic matter content) and amended soil B, pesticide residues were not found in the leachates. In addition, this paper reports on the use of common agronomic practices (solarization and biosolarization) to enhance degradation of these pesticides from polluted soil A. The results showed that both solarization and biosolarization enhanced the degradation rates of endosulfan, bifenthrin and tolclofos-methyl compared with the control. Most of the studied pesticides showed similar behavior under solarization and biosolarization conditions. However, chlorpyrifos was degraded to a greater extent in the solarization than in biosolarization treatment. The results obtained point to the interest in the use of organic amendment in reducing the pollution of groundwater by pesticide drainage and in the use of solarization and biosolarization in reducing the persistence of pesticides in soil.     

Biodegradation and speciation of residual SS-ethylenediaminedisuccinic acid (EDDS) in soil solution left after soil washing

This paper aims to investigate the degradation and speciation of EDDS-complexes (SS-ethylenediaminedisuccinic acid) in soil following soil washing. The changes in soil solution metal and EDDS concentrations were investigated for three polluted soils. EDDS was degraded after a lag phase of 7-11 days with a half-life of 4.18-5.60 days. No influence of EDDS-speciation on the reaction was observed. The decrease in EDDS resulted in a corresponding decrease in solubilized metals. Changes in EDDS speciation can be related to (1) initial composition of the soil, (2) temporarily anoxic conditions in the soil slurry after soil washing, (3) exchange of EDDS complexes with Cu even in soils without elevated Cu and (4) formation of NiEDDS. Dissolved organic matter is important for metal speciation at low EDDS concentrations. Our results show that even in polluted soils EDDS is degraded from a level of several hundred micromoles to below 1 microM within 50 days.     

铈离子光催化降解茜素绿的性能和机理

主要研究了简单铈离子（Ce3＋）在紫外光（uv）的作用下对蒽醌染料茜素绿（AG）的光催化降解效果和反应机理。结果表明，UV／Ce3＋体系能够有效降解AG，初始反应速率随AG浓度的倒数值和Ce3＋浓度的增加而线性增加，随初始溶液pH的增加先降低后增加，在酸性条件下有很高的TOC去除率。荧光探针实验表明，反应过程中可以产生·OH自由基。UV／Ce3＋体系对其他类型染料和对硝基苯酚都有较好的降解效果。