Extensive use of synthetic pyrethroids has resulted in concerns regarding their potential effects on human health and ecosystems. In the present study, we evaluated the influence of coexisting Cu²⁺, Zn²⁺, soil water contents (15%, 25%, 40% by weight and waterlogged) and temperature levels (15°C, 25°C, 35°C, and 45°C) on the dissipation of cypermethrin, fenvalerate and deltamethrin in red soil. To further clarify the influence of Cu²⁺ and Zn²⁺ on biological and chemical dissipation processes, serial concentrations of the synthetic pyrethroids containing Cu²⁺ (21.3, 50, 100, and 400 mg kg⁻¹) and Zn²⁺ (35.8, 100, 250, and 500 mg kg⁻¹) were used to spike the soil and then incubated at 25°C in the dark at 25% moisture. The results revealed a very severe inhibitory effect on the dissipation rates with increasing Cu²⁺ and Zn²⁺ levels. Conversely, there were no significant decreases in dissipation rates in response to exposure to 50 mg kg⁻¹ Cu²⁺ or 100 mg kg⁻¹ Zn²⁺, and the dissipation rates decreased significantly (p < 0.05) when the Cu²⁺ and Zn²⁺ concentration increased to 100 and 250 mg kg⁻¹, respectively, which were the respective maximum field recommended rates. When compared with unsterilized batch treatments, the t ₁/₂ in sterilized (chemical dissipation) batch treatments increased by 1.0-4.8-fold. Additionally, there was a highly significant difference in the dissipation of pyrethroids in the 15% water content treatments and waterlogged treatments (p < 0.05). Finally, the difference in the dissipation rates at 15°C and 25°C was significant (p < 0.05).

The arsenic contamination of Bangladesh groundwater involves heavy arsenic inputs to irrigated rice fields. Beside adsorption on soil colloids, iron-arsenic co-precipitation phenomena can affect arsenic retention in soils. In paddy fields of Satkhira District, Bangladesh, the study of the arsenic and iron forms in the irrigation waters and in soils at different times and distances from the irrigation well evidenced that a higher Fe/As ratio in the well water was related to a faster oxidation of Fe(II) and As(III) in water and to a close Fe-As association in soils, together with a greater accumulation of arsenic and poorly ordered iron oxides. The concentration of arsenic and of labile iron forms decreased with the distance from the well and with the depth, as well as the reversibility of arsenic binding. The fate of the arsenic added to the soils by irrigation hence resulted strongly influenced by iron-arsenic co-precipitation, depending on the Fe/As ratio in water. Irrigation systems favouring the sedimentation of the Fe-As flocks could help in protecting the rice from the adverse effects of dissolved arsenic.

Literature reports on N₂O and NO emissions from organic and mineral agricultural soil amended with N-containing fertilizers have reached contradictory conclusions. To understand the influence of organic manure (OM) and chemical fertilizer application on N₂O and NO emissions, we conducted laboratory incubation experiments on an agricultural sandy loam soil exposed to different long-term fertilization practices. The fertilizer treatments were initiated in 1989 at the Fengqiu State Key Agro-ecological Experimental Station and included a control without fertilizer (CK), OM, mineral NPK fertilizer (NPK), mineral NP fertilizer (NP), and mineral NK fertilizer (NK). The proportion of N emitted as NO and N₂O varied considerably among fertilizer treatments, ranging from 0.83% to 2.50% as NO and from 0.08% to 0.36% as N₂O. Cumulative NO emission was highest in the CK treatment after NH ₄ ⁺ -N was added at a rate of 200 mg N kg⁻¹ soil during the 612-h incubation period, whereas the long-term application of fertilizers significantly reduced NO emission by 54-67%. In contrast, the long-term application of NPK fertilizer and OM significantly enhanced N₂O emission by 95.6% and 253%, respectively, compared to CK conditions. The addition of NP fertilizer (no K) significantly reduced N₂O emission by 25.5%, whereas applications of NK fertilizer (no P) had no effect. The difference among the N-fertilized treatments was due probably to discrepancies in the N₂O production potential of the dominant ammonia-oxidizing bacteria (AOB) species rather than AOB abundance. The ratio of NO/N₂O was approximately 24 in the CK treatment, significantly higher than those in the N-fertilized treatments (3-11), and it decreased with increasing N₂O production potential in N-fertilized treatments. Our data suggests that the shift in the dominant AOB species might produce reciprocal change in cumulative NO and N₂O emissions.

The protection and conservation of natural resources is one of the main priorities of modern society. Water is perhaps our most valuable resource, and thus should be recycled. Many of the current recycling techniques for polluted water only concentrate the pollutant without degrading it or eliminating it. In this sense, advanced oxidation processes are possibly one of the most effective methods for the treatment of wastewater containing organic products (effluents from chemical and agrochemical industries, the textile industry, paints, dyes, etc.). More conventional techniques cannot be used to treat such compounds because of their high chemical stability and/or low biodegradability. This article describes, classifies, and analyzes different types of advanced oxidation processes and their application to the treatment of polluted wastewater.

An outdoor pot experiments was conducted to investigate the effects of enhanced ultraviolet-B (UV-B) radiation on nitrous oxide (N₂O) emissions from soil-winter wheat systems. The enhanced UV-B radiation treatments were simulated by 20% increase in its intensity. N₂O fluxes were measured with a static opaque chamber-gas chromatograph method. The results showed that enhanced UV-B radiation did not change the seasonal patterns of N₂O emissions. Compared to the controls, the enhanced UV-B radiation reduced N₂O fluxes by 16.4% (p = 0.015) during the elongation-booting stage, while it had no significant effects on N₂O fluxes in the turning-green and heading-maturity phases. During the turning green-overall heading span, the accumulative N₂O was largely decreased by the enhanced UV-B radiation (p < 0.05). From the overall heading to maturity, however, the effects of enhanced UV-B on N₂O emissions were not pronounced (p > 0.10). At the elongation-booting stage, enhanced UV-B increased soluble proteins content in leaves, NO ₃ ⁻ -N and NO ₄ ⁺ -N content in rhizosphere soil, and soil microbial biomass C (C mic) and N (N mic; p < 0.05), as well as microbial biomass C:N ratio changing from 5.0 to 6.8. Our findings suggest that the effects of enhanced UV-B radiation on N₂O emissions differed with winter wheat developmental stages. To assess the overall effects of enhanced UV-B radiation on N₂O emissions from agroecosystems, nevertheless, more field measurements deserve to be carried out in various cropping systems.

Alkanolamines in the wastewater from gas treating plants are not readily biodegradable. In this work, we have investigated the effectiveness of the Fenton's reagent (H₂O₂-Fe²⁺) to treat monoethanolamine (MEA) as a model compound in simulated wastewater. Degradation studies were carried out in a jacketed glass reactor. The effects of concentrations of ferrous sulfate, hydrogen peroxide, and the pH of a solution on the rate of reaction were determined. A pH of 3 was found to be the optimum. The degradation reaction proceeds very fast at the beginning but slows down significantly at a longer time. A larger fractional degradation of the organics in solution was observed if the initial chemical oxygen demand (COD) of the feed solution was high. Gradual addition of H₂O₂ to the reaction mixture increased the COD removal by about 60% compared to one-time addition of the reagent at the beginning of the process. A rate equation for mineralization of the amine was developed on the basis of a simplified mechanistic model, and the lumped value of the rate constant for COD removal was determined. A partially degraded MEA solution as well as “pure” MEA was subjected to biological oxidation by activated sludge. The former substrate degraded much faster. The degradation rate and biomass generation data could be fitted by the Monod kinetic equations.

Considering the importance of the oral route for human exposure to atrazine, we have investigated the possible effect of this herbicide on the human intestinal cells and the integrity of the epithelial barrier, using Caco-2 cells as the intestinal model in vitro. We evaluated possibile cytotoxic and genotoxic effects of atrazine in concentrations ranging from 1 to 250 μM on the Caco-2 cells at different stages of growth after short- and long-term exposure. Results from the tetrazolium blue (MTT) test and the Trypan blue exclusion assay showed that atrazine cytotoxicity was dose- and time-dependent. Obtained data indicated that atrazine at high concentrations (50 and 250 μM) was able to induce effects on Caco-2 proliferation and viability. Moreover, it was found that the long-term exposure to atrazine at the non-cytotoxic dose caused inhibition of the intestinal cell maturation and decreased the transepithelial electrical resistance, the indicator of the epithelial barrier integrity. Studies on the atrazine genotoxicity determined using the single cell microelectrophoresis assay indicated that atrazine did not induce DNA damages in the Caco-2 cells at concentrations of up to 50 μM, whereas enhancement in the DNA damage was observed at 250 μM. Altogether, our results indicate that atrazine at expected human oral exposure concentrations is not able to induce effects on the Caco-2 cell proliferation and viability, but may suppress the intestinal cell differentiation and reduce the cell monolayer integrity. We suggest that chronic exposure on low levels of atrazine may lead to alteration in the expression of the morphological and functional features of the Caco-2 cells related to the transport and barrier function of small intestinal enterocytes. In consequence, this may lead to alterations in the intestinal absorption process.

Single-particle analysis of short-term aerosol samplings can provide unique information on the rapid evolution of size distribution and chemical composition of industrial aerosols. In this work, the potential of scanning electron microscopy equipped with energy-dispersive X-ray spectrometry (SEM-EDX) for the time-resolved description of physicochemical properties of individual aerosol particles is investigated. Two sampling campaigns were carried out at a densely populated and industrialised coastal site. The first sampling campaign corresponded to low and stable atmospheric particle loads. Low temporal variations in PM₁₀ and PM₂.₅ mass concentrations during the preceding hours and during samplings were observed. In these conditions suitable to evaluate the accuracy of our sampling and analytical methodologies, very low temporal variation of physicochemical characteristics of atmospheric particles were observed, as expected. During the second sampling campaign, the ability of automated SEM-EDX to describe short temporal variation in PM₁₀ and PM₂.₅ chemical composition was demonstrated. We report the tracking of a steelworks emission plume transported over an urban area by means of short-term aerosol samplings and explore how this transient industrial emission contributed to ambient particulates. Steelworks are important point-source emitters of metallic pollutants such as iron, manganese, and zinc species. Detailed assessment of the microphysical and chemical properties of aerosols collected in the vicinity of steelworks enables to precisely describe how industrial aerosols affect the composition of urban particulate matter. The studied pollution event caused dramatic changes in the composition of urban aerosols by an input of fine metallic particles containing Fe, Mn or Zn oxides and mixed particles (Mn-Fe, Zn-Mn, Zn-Fe oxides). Metal-rich particles were often found internally mixed with marine and/or continental compounds, demonstrating how industrial aerosols efficiently coagulate with particles from other sources, thereby acting as carriers of heavy metals.

Ganga-Meghna-Bramhaputra basin is one of the major arsenic-contaminated hotspot in the world. To assess the level of severity of arsenic contamination, concentrations of arsenic in irrigation water, soil, rice, wheat, common vegetables, and pulses, intensively cultivated and consumed by the people of highly arsenic affected Nadia district, West Bengal, India, were investigated. Results revealed that the arsenic-contaminated irrigation water (0.318-0.643 mg l⁻¹) and soil (5.70-9.71 mg kg⁻¹) considerably influenced in the accumulation of arsenic in rice, pulses, and vegetables in the study area. Arsenic concentrations of irrigation water samples were many folds higher than the WHO recommended permissible limit for drinking water (0.01 mg l⁻¹) and FAO permissible limit for irrigation water (0.10 mg l⁻¹). But, the levels of arsenic in soil were lower than the reported global average of 10.0 mg kg⁻¹ and was much below the EU recommended maximum acceptable limit for agricultural soil (20.0 mg kg⁻¹). The total arsenic concentrations in the studied samples ranged from <0.0003 to 1.02 mg kg⁻¹. The highest and lowest mean arsenic concentrations (milligrams per kilogram) were found in potato (0.654) and in turmeric (0.003), respectively. Higher mean arsenic concentrations (milligrams per kilogram) were observed in Boro rice grain (0.451), arum (0.407), amaranth (0.372), radish (0.344), Aman rice grain (0.334), lady's finger (0.301), cauliflower (0.293), and Brinjal (0.279). Apart from a few potato samples, arsenic concentrations in the studied crop samples, including rice grain samples were found not to exceed the food hygiene concentration limit (1.0 mg kg⁻¹). Thus, the present study reveals that rice, wheat, vegetables, and pulses grown in the study area are safe for consumption, for now. But, the arsenic accumulation in the crops should be monitored periodically as the level of arsenic toxicity in the study area is increasing day by day.

Electrocoagulation (EC) has been evaluated as a treatment technology for arsenic (As) removal. Experiments were developed in an electrochemical reactor with three parallel iron plates. Current densities of 15, 30, and 45 A m⁻² were used to treat model water and 45 A m⁻² to treat underground water (GW). For both types of water, the EC process was able to decrease the residual arsenic concentration to less than 10 μg L⁻¹. However, the treatment time for As removal from GW was higher. This phenomenon was attributed to the competition of dissolved species present in GW such as silica and calcium with arsenic for the adsorption sites on the ferric oxyhydroxides flocs generated during the EC process. A procedure is proposed to reduce such interference by the addition of a silica adsorption inhibitor compound into the GW achieving a reduction in the process time. The adsorption of arsenic species over adsorbent was found to follow Lagergren adsorption model.