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We conducted batch studies to investigate the effect of phosphate and dominant cations present in tannery waste on desorption of chromium (Cr) from surface and subsurface soil horizons from a contaminated tannery waste site at Mount Barker, South Australia. The surface horizon (0-15 cm) of the soil profile was alkaline (pH 7.9) and the subsurface horizon (50-90 cm) was acidic (pH 3.9). Aqua-regia extractable Cr concentration ranged from 62 g/kg in the surface to 0.26 g/kg in the subsurface soils. X-ray diffraction and scanning electron microscopic studies revealed the predominance of carbonate and kaolin minerals in the surface soils, and highly weathered framboidal particles, with morphology similar to that of pyrites, in the subsurface soils. The amount of Cr desorbed from the contaminated soils varied considerably with both the electrolyte's cationic charge and soil properties. The effect of cations, [Ca.sup.2+] and [Na.sup.+] (Ca[Cl.sub.2], NaCl), and phosphate on desorption of Cr was investigated. While the ionic strength of the solutions was standardised at approximately 0.03 mol/L, the concentration of phosphate (as [KH.sub.2][PO.sub.4]) was varied from 0 to 3.2 mmol/L. On the basis of studies on solution to soil ratio and desorption kinetics we chose a 20:1 solution to soil ratio and 2 h equilibration time. In the surface alkaline soil, the amount of Cr released decreased in the order [Na.sub.+] (286 µg/L) [is greater than or equal to] water (256 µg/L) [is greater than] [Ca.sup.2+] (156 µg/L). In contrast subsurface acidic soil showed a reverse trend, i.e. [Ca.sup.2+] (52 µg/L) [is greater than] [Na.sup.+] (29 µg/L) [is greater than] water (20 µg/ L). Speciation of Cr in the extracts showed predominantly Cr(VI) in the alkaline surface soil and Cr(III) in the subsurface acidic soil. A strong effect of phosphate on the cumulative amount of chromate desorbed was observed. The study shows that the presence of high concentrations of [Na.sup.+] (0.03 mol/L) and phosphate (3.2 mmol/L) in soil solution enhances Cr(VI) mobility. In contrast, [Ca.sup.2+] may induce retention of Cr(VI) in Cr-contaminated alkaline soils. Additional keywords: hexavalent chromium, chromate, leaching, contaminated site., Introduction Tanning industries worldwide generate approximately 40 million [m.sup.3] of waste containing chromium (Cr) every year (Macchi et al. 1991). With inadequate regulatory guidelines, wastes were largely disposed on land [...]

Abstract Sorption of 2 nonionic pesticides, carbaryl (1-naphthyl methylcarbamate) and phosalone (S-6-chloro-2,3-dihydro-2-oxobenzoxazol-3-ylmethyl O,O-diethyl phosphorodithioate), was investigated for 48 soils from Australia, Pakistan, and the United Kingdom. A wide variation in [...]

A field study was conducted on an alkaline cropping soil (plot size 4 m by 1 m), representative of cereal growing regions in southern Australia, to examine the degradation and leaching behaviour of triasulfuron, metsulfuron-methyl, and chlorsulfuron (150 g a.i./ha), along with a non-reactive tracer (KBr, 50 kg/ha), under 2 water treatments (`rainfall' and `rainfall + irrigation'). The results showed that the distributions of water content, [Br.sup.-] and the 3 herbicides were influenced by the amount of rainfall/irrigation received, and the biological activity as well as the physico-chemical properties of the soil within the profile. The largest concentrations of [Br.sup.-] were detected in the 10-20 cm depth under both treatments. No additional peak of [Br.sup.-] was observed in the plots which received only rainfall; however, there was another peak at 100 cm depth after a cumulative rainfall and irrigation of 158 mm. The spatial distribution of [Br.sup.-] in the plots was attributed to preferential flow through cracks or the presence of `mobile' and `immobile' water, which gave rise to bimodal distribution in the profile. Metsulfuron-methyl showed the greatest mobility, followed by chlorsulfuron and triasulfuron under both the treatments, with metsulfuron-methyl being detected at 120 cm depth under rainfall + irrigation. A bimodal distribution was also observed for the 3 herbicides, but the location of peaks was dependent on the solute. Rates of degradation of the herbicides could be described reasonably well with first-order reaction kinetics ([r.sup.2] = 0.72-0.91). The half-lives for triasulfuron, metsulfuron-methyl, and chlorsulfuron were 44, 45, and 32 days, respectively, under rainfall (69 mm), and 46, 59, and 48 days under rainfall + irrigation (158 mm). Additional keywords: sulfonylureas, dissipation, preferential flow, rainfall, irrigation., Introduction Triasulfuron, metsulfuron-methyl, and chlorsulfuron are the 3 most commonly used sulfonylurea herbicides for controlling broad-leaved weeds in the cereal crops of southern Australia. The compounds are weak acids (p[K.sub.a] [...]

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]

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]

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]