Influence of plants on the chemical extractability and biodegradability of 2,4-dichlorophenol in soil

This study investigated the fate and behaviour of [UL-(14)C] 2,4-dichlorophenol (DCP) in planted (Lolium perenne L.) and unplanted soils over 57 days. Extractability of [UL-(14)C] 2,4-DCP associated activity was measured using calcium chloride (CaCl(2)), acetonitrile-water and dichloromethane (DCM) extractions. Biodegradability of [UL-(14)C] 2,4-DCP associated activity was assessed through measurement of (14)CO(2) production by a degrader inoculum (Burkholderia sp.). Although extractability and mineralisation of [UL-(14)C] 2,4-DCP associated activity decreased significantly in both planted and unplanted soils, plants appeared to enhance the sequestration process. After 57 days, in unplanted soil, 27% of the remaining [UL-(14)C] 2,4-DCP associated activity was mineralised by Burkholderia sp., and 13%, 48%, and 38% of (14)C-activity were extracted by CaCl(2), acetonitrile-water and DCM, respectively. However, after 57 days, in planted soils, only 10% of the [UL-(14)C] 2,4-DCP associated activity was available for mineralisation, whilst extractability was reduced to 2% by CaCl(2), 17% by acetonitrile-water and 11% by DCM. This may be due to the effect of plants on soil moisture conditions, which leads to modification of the soil structure and trapping of the compound. However, the influence of plants on soil biological and chemical properties may also play a role in the ageing process.     

Removal of the herbicide amitrole from water by anodic oxidation and electro-Fenton

Here we demonstrate that an aqueous solution of the herbicide amitrole can be completely depolluted at pH 3.0 by anodic oxidation and electro-Fenton process. Anodic oxidation gives faster degradation with a boron-doped diamond anode than with a Pt anode. Electro-Fenton with a Pt anode and 1 mmol l ^–1 Fe²⁺ as catalyst yields the quickest depollution. Amitrole decay always follows a pseudo first-order reaction. NO₃^– and NH₄⁺ are accumulated in the medium during mineralization, although volatile N-products are also formed. These environmentally friendly electrochemical treatments could be applied to the remediation of wastewaters containing amitrole.     

Herbicidal activity of slow-release herbicide formulations in wheat stands infested by weeds

The present study reports the herbicidal activity of metribuzin and tribenuron-methyl embedded in the degradable matrix of natural poly-3-hydroxybutyrate [P(3HB)/MET and P(3HB)/TBM]. The developed formulations were constructed as films and microgranules, which were tested against the weeds such as white sweet clover Melilotus albus and lamb's quarters Chenopodium album in the presence of soft spring wheat (Triticum aestivum, cv. Altaiskaya 70) as the subject crop for investigation. The activity was measured in laboratory scale experiments by determining the density and weight of the vegetative organs of weeds. The study was also aimed at testing the effect of the experimental formulation on the growth of wheat crop as dependent on the method of herbicide delivery. The experimental MET and TBM formulations showed pronounced herbicidal activity against the weed species used in the study. The effectiveness of the experimental formulations in inhibiting weed growth was comparable to and, sometimes, higher than that of the commercial formulations (positive control). The amount of the biomass of the wheat treated with the experimental herbicide formulations was significantly greater than that of the wheat treated with commercial formulations.     

Photocatalytic degradation of dichlorvos in aqueous TiO<Subscript>2</Subscript> suspensions

Introduction  

In the present work, we explored the kinetics of dichlorvos (2,2-dichlorvinyl dimethyl phosphate, DDVP) decay through UV-A light-induced TiO₂ photocatalysis at pH 4 and 9, and the formation of degradation intermediates and final products under specific experimental conditions. Experimental observations and theoretical considerations allowed us to suggest the degradation mechanism of DDVP by the UV/TiO₂ process in aqueous solution.     

Esterase inhibition in tadpoles of <Emphasis Type="Italic">Scinax fuscovarius</Emphasis> (Anura,Hylidae) as a biomarker for exposure to organophosphate pesticides

Purpose  

Organophosphate pesticides (OPs) are among the most used insecticides in agriculture, causing the inhibition of esterases like acetylcholinesterase (AChE), butyrylcholinesterase (BChE) and carboxylesterase (CbE). Pesticides can reach the aquatic environment, posing risks to non-target organisms, including tadpoles.     

Transport and distribution of artificial gamma-emitting radionuclides in the River Yenisei and its sediment

Discharges from the Krasnoyarsk Mining and Chemical Industrial Complex (KMCIC) near Krasnoyarsk resulted in radioactive contamination of sediments of the River Yenisei. Between 1999 and 2006, 16 sediment cores were collected at different positions 15-1500 km downstream from the discharge point. The concentration of artificial gamma-emitting radionuclides (¹³⁷Cs, ⁶⁰Co, ¹⁵²Eu, and ²⁴¹Am) was determined with the objective to analyze the migration processes leading to the transport of these radionuclides along the river and to their vertical distribution within the sediment. In cores taken in the vicinity of the reactors, the average activity concentration of ¹³⁷Cs, ¹⁵²Eu, and ⁶⁰Co was about 1000 Bq kg⁻¹, and the activity concentration of ²⁴¹Am was about 20 Bq kg⁻¹. Contamination levels of artificial radionuclides were decreasing with increasing distance downstream the KMCIC: The fastest decrease of average activity by a factor of 10 over a distance of 300 km was observed for ²⁴¹Am, whereas for ¹³⁷Cs this decrease occurred over a distance of 1100 km. Sequential extraction experiments revealed that in all depths and at all distances the studied radionuclides were tightly bound to the sediment.To investigate the mechanisms of transport of the ¹³⁷Cs and ⁶⁰Co contamination, mathematical models have been used to describe the contamination in the river water and within the sediments.     

Abatement of spinosad and indoxacarb residues in pure water by photocatalytic treatment using binary and ternary oxides of Zn and Ti

The photodegradation of indoxacarb, a broad spectrum foliar insecticide and spinosad, a natural insecticide containing two active ingredients, spinosyn A (major component) and spinosyn D (minor component), was studied in aqueous suspensions of binary (ZnO and TiO₂) and ternary (Zn₂TiO₄ and ZnTiO₃) oxides under artificial light (300–460 nm) irradiation. As expected, the influence of the semiconductor materials on the degradation of both was very significant in all cases. Photocatalytic experiments showed that the addition of semiconductors in tandem with Na₂S₂O₈ as electron acceptor strongly improved the removal of indoxacarb and spinosad in water compared with the photolytic tests. The reaction rates significantly increased, especially for the ZnO/Na₂S₂O₈ and TiO₂/Na₂S₂O₈ systems. The first-order equation (monophasic model) satisfactorily explained the disappearance process, although it offered no explanation for the small concentrations remaining in the process.