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A batch test approach was used to assess the in situ attenuation by natural reservoir systems of selected disinfection by-products ( DBPs). The aim was to determine which natural attenuation processes (volatilisation, photolysis and biodegradation) dominated for selected trihalomethanes ( THMs) and N-nitrosodimethylamine ( NDMA), common DBPs present in reclaimed water which could be used to potentially augment drinking water supplies. Attenuation rates for THMs were found to be all very similar, with half-lives ranging from 1.5-1.6 days for open batch tests. The dominant attenuation mechanisms for THMs were volatilisation with hydrolysis and biodegradation of potentially minor importance. NDMA had a half-life of 3.5-4.3 days for vials exposed to light. The most important attenuation mechanism for NDMA was photolysis with volatilisation and biodegradation of minor importance. The results indicate that the selected DBPs could be effectively attenuated by a natural reservoir system such as a surface water reservoir. [ABSTRACT FROM AUTHOR]

Triclosan (TCS) is an antimicrobial agent used widely in household products such as soaps, household cleaners, cosmetics, sportswear, mouthwash and toothpaste. It is a bioaccumulative compound known for its high toxicity to algae, daphnids, fish and other aquatic organisms. we investigated its occurrence in effluents, biosolids and surface waters in Australia, as well as its fate in Australian soils and wastewater treatment plants (WWTP5), including the effects on microbial processes in soils. The concentrations of TCS in 19 effluents ranged from 23 to 434 ng/L (median 108 ng/L) and in 17 biosolids from 0.09 to 16.79 mg/kg on dry weight basis (median 2.32 mg/kg). TCS at concentrations of up to 75 ng/L were detected in receiving waters from five creeks affected by effluent discharge from wWTP5. The removal rate of TCS in five selected WWTP5 ranged from 72 and 93%, ascribed mainly to sorption onto sludge and biological degradation. Biodegradation in a clay loam soil was noted with a half life of 18 days. However the half-lives under field conditions are expected to be very different. The studies on the effect of TCS on soil microbiological processes showed that triclosan can disrupt the nitrogen cycle in sensitive soils at concentrations ≥5 mg/kg. In view of the recent risk assessment by the Australian regulatory agency NICNAS, there is an urgent need to assess exposure to TCS and its effect on ecosystem health. [ABSTRACT FROM AUTHOR]

Reuse of biosolids on agricultural land is a common practice. Following the application of biosolids to land, contaminants in the biosolids have the potential to migrate offsite via surface runoff and/or leaching and pose a hazard to aquatic ecosystems. The aim of this screening-level assessment study was to determine the relative hazard posed to aquatic ecosystems by pharmaceuticals, personal care products, and endocrine-disrupting compounds (EDCs) that have been detected and quantified in biosolids. This involved estimating maximum possible runoff water concentrations of compounds, using an equilibrium partitioning approach and then comparing these with the lowest available aquatic toxicity data, using the hazard quotient (HQ) approach. A total of 45 pharmaceuticals, personal care products, and EDCs have been detected in biosolids. Ten of these compounds (tonalide, galaxolide, 17β-estradiol, 17α-ethinylestradiol, ciprofloxacin, doxycycline, norfloxacin, ofloxacin, triclosan, and triclocarban) posed a high (HQ >1.0) hazard to aquatic ecosystems relative to the other compounds. This hazard assessment indicated that further research into potential offsite migration and deleterious effects on aquatic ecosystems is warranted for the 10 organic contaminants identified, and possibly for chemicals with similar physicochemical and toxicological properties, in biosolids-amended soils. Because many antibiotic compounds (e.g., ciprofloxacin, norfloxacin, and ofloxacin) have ionic properties, the methods used may have overestimated their predicted aqueous concentrations and hazard. Further research that includes site-specific variables, e.g., dilution factors in waterways, rain intensity, slope of land, degradation, and the use of management strategies such as buffer zones, is likely to decrease the hazard posed by these high hazard compounds. Integr Environ Assess Manag 2010;6:663-676. © 2010 SETAC [ABSTRACT FROM AUTHOR]

Degradation rates of 14C ring labeled carbofuran and diazinon in selected Sri Lankan soils were studied using 0.1 μCi/10 g soil in Nuwara Eliya (red yellow podzolic), Pugoda (alluvials) Kalpitiya and Negombo (regosols) soils by incubating at 28 °C of temperature for 13 hours light and 11 hours dark conditions and measuring the activity of liberated CO2 using liquid scintillation counter after 0, 1, 3, 5, 7, 14, 28, 36, 42 and 58 days. During the total period the carbofuran mineralization was about 23% in Kalpitiya soils and less than 20% in other three soils and diazinon mineralization was about 25% in Negombo soil and very low in other soils. [ABSTRACT FROM AUTHOR]

Although the chemical composition of soil organic matter (SOM) is known to significantly influence sorption of pesticides and other pollutants, it has been difficult to determine the molecular nature of SOM in situ. Here, using 13C nuclear magnetic resonance (NMR) data and elemental composition in a molecular mixing model, we estimated the molecular components of SOM in 24 soils from various agro-ecological regions. Substantial variations were revealed in the molecular nature of SOM. As a proportion of soil carbon the proportion of the carbonyl component ranged from 0.006 to 0.05, charcoal from 0 to 0.15, protein from 0.09 to 0.29, aliphatic from 0.14 to 0.30, carbohydrate from 0.21 to 0.31, and lignin from 0.05 to 0.42. The relationships between Koc (sorption per unit mass of organic carbon) of carbaryl (1-naphthyl methylcarbamate) and phosalone ( S-6-chloro-2,3-dihydro-2-oxobenzoxazol-3-ylmethyl O,O-diethyl phosphorodithioate) and the molecular nature of organic matter in the soils were significant. Of the molecular components estimated, lignin and charcoal contents correlated best with sorption of carbaryl and phosalone. Aliphatic, carbohydrate and protein contents were found to be negatively correlated with the Koc of both pesticides. The study highlights the importance of the molecular nature of SOM in determining sorption affinities of non-ionic pesticides and presents an indirect method for sorption estimation of pesticides. [ABSTRACT FROM AUTHOR]

Transport of pesticide to groundwater is governed in part by sorption of the pesticide to soil particles. Sorption may be dependent on soil moisture conditions, but limited data are available from which to elucidate the effect. Our objective was to determine the effect of soil water content on the sorption coefficient of a hydrophilic pesticide. Sorption of dicamba (3,6-dichloro-2-methoxybenzoic acid) was measured in three soils, each at two initial water contents. At low water contents (∼0.05 kg kg-1), sorption coefficients were similar for all three soils, ranging from 0.01 L kg-1 for the loamy sand to 0.07 L kg-1 for the silty clay loam. At higher water contents (0.19–0.24 kg kg-1), the sorption coefficient for the loamy sand was unchanged, for the silt loam it was doubled, and for the silty clay loam it was increased almost sixfold. Multiple regression analysis revealed a strong linear relationship between the sorption coefficient and the product of soil water content and organic C content (r² = 0.86). The number of dicamba sorption sites probably increases with soil organic C content, while the accessibility of these sites appears to increase with soil water content. This may be caused by the decreasing hydrophobicity of soil organic matter with increasing water content. The effects of water content on pesticide sorption require further research and may ultimately have implications for the methods used to determine sorption and for managing pesticide application. [ABSTRACT FROM AUTHOR]

The article presents a study to evaluate the effectiveness of few montmorillonite organoclays to absorb and retain highly water soluble fenamiphos, therefore sorption-desorption behavior of fenamiphos was compared in natural and cationic-surfactant-modified clays. In the present study we have used the K-montmorillonite clay as standard natural clay. K-montmorillonite was prepared by replacing the sodium in Na- montmorillonite clay by potassium. Therefore, Na-montmorillonite clay was equilibrated with 1M potassium chloride solution for 24 hour.

A bacterium, identified as Brevibacterium sp. MM1, readily hydrolysed fenamiphos, a widely used organophosphorus insecticide and its toxic oxides (fenamiphos sulfoxide, fenamiphos sulfone), which all contain a common P–O–C bond, in a mineral salts medium. The bacterium also hydrolysed fenamiphos and its oxides in soil and groundwater. Interestingly, fenamiphos phenol, fenamiphos sulfoxide phenol and fenamiphos sulfone phenol, formed during bacterial hydrolysis of fenamiphos and its oxides, persisted in the mineral salts medium, but were transitory in soil and groundwater due to their further metabolism by indigenous micro-organisms. The cell-free preparation (crude enzyme) of this bacterium was very effective in hydrolysing fenamiphos. This is the first report on exceptionally rapid hydrolysis of fenamiphos by a bacterium in pure cultures, soil and groundwater. [ABSTRACT FROM AUTHOR]

This article focuses on endosulfan which has been widely used as a broadspectrum cyclodiene insecticide on a wide range of crops including upland cotton and wetland rice systems. It persists in soil and water environments for 3 to 6 months or more. However, it is generally less persistent in environment than other cyclodienes. Endosulfan can undergo degradation to non-toxic or less toxic endosulfan diol or oxidation to equally or more toxic endosulfan sulfate in plants, microbial cultures and soils. Endosulfan sulfate appears to be the most persistent metabolite of endosulfan in soils, but undergoes rapid degradation in cotton foliage.

The article investigates sorption of seven pesticides namely bifenthrin, pho salone, carbaryl, ametryn, imazethapyr, monocrotophos and dichiorvos by various syringe microfilters and to evaluate the compatibility of the filters with these pesticides. Filtration is an essential step to remove solid particles from the soil solution or particulate matter from aqueous solution prior to the pesticide analysis. The pesticides that were studied in the article represent a wide spectrum of chemical properties.

Sulfonylurea herbicides in soil extracts were concentrated using off-line solid-phase extraction (SPE), and determined by capillary zone electrophoresis (CZE) and UV detection. The method involves extraction of soils with 0.1 M NaHCO3 solution and subsequent preconcentration by using C18 cartridges prior to separation of the pesticide using CZE. The results show that a C18 cartridge is suitable for the purification of sulfonylurea herbicides in soil extracts with the recoveries ranging from 65–103%. The separation conditions affecting the resolution and detection sensitivity was systematically investigated. The sulfonylureas were resolved well using 30 mM sodium acetate (NaAc)/acetic acid (HAc)+10% acetonitrile (ACN) buffer at pH 4.80. The calibration plots for the test solutes in the concentration of 0.2–50 mg L−1 were linear with detection limits in the range of 0.05–0.10 mgL−1. The proposed method has been successfully demonstrated for the determination of sulfonylurea herbicides in soil samples. [ABSTRACT FROM AUTHOR]

A method capable of simultaneously detecting residues of three sulfonylurea herbicides at µg/I and µg/kg level in water and alkaline soils has been described. The method is based on solid phase extraction and HPLC with UV detection. In alkaline soils especially those containing low organic carbon it was possible to extract the herbicides with de-ionised water and no clean up step was needed. Soil samples spiked with technical grade triasulfiiron, metsulfuron-methyl and chlorsulfuron were extracted twice by shaking with de-ionised water for one hour and centrifuging at 10000 rpm for 15 minutes. Supernatants filtered through glass micro-fibre filters were passed through C18 cartridges previously pre-conditioned with methanol and de-ionised water at a flow rate of < 20 ml/min. Residues of the herbicides retained on the cartridge were eluted with acidified methanol. The eluate was analysed by HPLC. A C18 column was used with a mobile phase of methanol/water (40 + 60, V/V for for the herbicide residues were 1.0 µg/l and 3 µg/kg in water and soil, respectively. The average recoveries for water samples ranged from 73 - 94%, while for soil samples recoveries were 77 - 97% for the three compounds studied. [ABSTRACT FROM AUTHOR]

The hydrolysis of triasulfuron, metsulfuron-methyl and chlorsulfuronin aqueous buffer solutions and in soil suspensions at pH values ranging from 5.2 to 11.2 was investigated. Hydrolysis of all three compounds in both aqueous buffer and soil suspensions was highly pH-sensitive. The rate of hydrolysis was much faster in the acidic pH range (5.2-6.2) than under neutral and moderately alkaline conditions (8.2-9.4), but it increased rapidly as the pH exceeded 10.2. All three compounds degraded faster at pH 5.2 than at pH 11.2. Hydrolysis rates of all three compounds could be described well with pseudo-first-order kinetics. There were no significant differences (P = 0.05) in the rate constants (k, day-1) of the three compounds in soil suspensions from those in buffer solutions within the pH ranges studied. A functional relationship based on the propensity of nonionic and anionic species of the herbicides to hydrolyse was used to describe the dependence of the 'rate constant' on pH. The hydrolysis involving attack by neutral water was at least 100-fold faster when the sulfonylureaherbicides were undissociated (acidic conditions) than when they were present as the anion at near neutral pH. In aqueous buffer solutionat pH > 11, a prominent degradation pathway involved O-demethylationof metsulfuron-methyl to yield a highly polar degradate, and hydrolytic opening of the triazine ring. It is concluded that these herbicides are not likely to degrade substantially through hydrolysis in most agricultural alkaline soils. [ABSTRACT FROM AUTHOR]

A method capable of simultaneously detecting residues of three sulfonylurea herbicides at mu g/l and mu g/kg level in water and alkaline soils has been described. The method is based on solid phase extraction and HPLC with UV detection. In alkaline soils especially those containing low organic carbon it was possible to extract the herbicides with de-ionised water and no clean up step was needed. Soil samples spiked with technical grade triasulfuron, metsulfuron-methyl and chlorsulfiaron were extracted twice by shaking with de-ionised water for one hour and centrifuging at 10000 rpm for 15 minutes. Supernatants filtered through glass micro-fibre filters were passed through C18 cartridges previously pre-conditioned with methanol and de-ionised water at a flow rate of < 20 ml/min. Residues of the herbicides retained onthe cartridge were eluted with acidified methanol. The eluate was analysed by BPLC. A C18 column was used with a mobile phase of methanol/ water (40 + 60, VN for for the herbicide residues were 1.0 mu g/l and 3 mu g/kg in water and soil, respectively. The average recoveriesfor water samples ranged from 73 - 94%, while for soil samples recoveries were 77 - 97% for the three compounds studied. [ABSTRACT FROM AUTHOR]