Chapter 31 Arsenic speciation in soils: an analytical challenge for understanding arsenic biogeochemistry

Occurrence, fate, and potential impacts of wood preservatives in the environment: Challenges and environmentally friendly solutions

Wood preservation has gained global prevalence in recent years, primarily owing to the renewable nature of wood and its capacity to act as a carbon sink. Wood, in its natural form, lacks intrinsic resilience and is prone to decay if left untreated; hence, wood preservatives (WPs) are used to improve wood's longevity. The fate and potential hazards of wood preservatives to human health, ecosystems, and the environment are complex and depend on various aspects, including the type of the preservative compounds, their physicochemical properties, application methods, exposure pathways, environmental conditions, and safety measures and guidelines. The occurrence and distribution of WPs in environmental matrices such as soil and water can result in hazardous pollutants seeping into surface water, groundwater, and soil, posing health hazards, and polluting the environment. Bioremediation is crucial to safeguarding the environment and effectively removing contaminants through hydrolytic and/or photochemical reactions. Phytoremediation, vermicomposting, and sustainable adsorption have demonstrated significant efficacy in the remediation of WPs in the natural environment. Adsorbents derived from biomass waste have been acknowledged for their ability to effectively remove WPs, while also offering cost-efficiency and environmental sustainability. This paper aims to identify wood preservatives' sources and fate in the environment and present a comprehensive overview of the latest advancements in environmentally friendly methods relevant to the removal of the commonly observed contaminants associated with WPs in environmental matrices.

The changes in the physicochemical properties of calcareous soils and the factors of arsenic (As) uptake by wheat were investigated after the cessation of effluent irrigation for nearly 20 years

It is not known what the buffering capacity of soils and arsenic (As) enrichment by crops is for calcareous agricultural soils after the end of long-term effluent irrigation. In this study, changes in soil physicochemical properties and factors of influencing As uptake by wheat were investigated in agricultural soils where sewage irrigation had been ceased for nearly 20 years. The results showed that the content of CaCO₃ and pH in soil increased compared to the period before the cessation of sewage irrigation, but remained below the soil background value. Furthermore, CaCO₃ is by far the main buffering substance in agricultural soils and indirectly contributes to the increase in pH. The As concentration in the soil was 36.4 ± 34.8 mg/kg, which was 0.56-10.28 times and 0.28-5.18 times higher than the soil background and risk screening values, respectively, but showed a decreasing trend. pH and Fe dissolution were the main reasons for the lower As concentration in the soil. Total As in soil was a better predictor of As in wheat, and soil electrical conductivity (EC) and soil organic matter (SOM) promoted As uptake by wheat. The competitive uptake of As by dissolved Si was an important reason for the mismatch between As concentrations in soil and wheat. This study highlighted the key issues of As transport transformation in soil-wheat systems after cessation of effluent irrigation, using agricultural soils, and provided a reference for soil risk management in agricultural soils in mining areas.

In situ arsenic speciation at the soil/water interface of saline-alkaline lakes of the Pantanal, Brazil: A DGT-based approach

Arsenic (As) is a naturally occurring element in the Earth's crust, exhibiting toxicity towards a wide range of living organisms. Its properties and environmental dynamics are strongly regulated by its speciation, and the species As(III) and As(V) are the most commonly found in environmental systems. Recently, high concentrations of As were found in saline-alkaline lakes of the Pantanal (Brazil), which is the largest wetland area in the world. Therefore, we evaluated As contamination and its redox speciation (As(III) and As(V)) at the soil/water interface of biogeochemically distinct saline-alkaline lakes of Pantanal wetlands (Brazil). Both conventional sampling and in situ diffusive gradients in thin films (DGT) technique were employed. Zirconium oxide and 3-mercaptopropyl were used as ligand phases in DGT to selectively bind As species. High concentrations of total dissolved As in a shallow water table were found (<2337.5 μg L^-1), whereas levels in soils were up to 2.4 μg g^-1. Distinct scenarios were observed when comparing speciation analysis through spot sampling and DGT. Considering spot sampling, As(V) was the main species detected, whereas As(III) was only detected in only a few samples (<4.2 μg L^-1). Conversely, results obtained by DGT showed that labile As(III) dominated arsenic speciation at the soil/water interface with levels up to 203.0 μg L^-1. Coupling DGT data and DGT induced fluxes in sediments and soils model allowed obtaining kinetic data, showing that the soil barely participated in the arsenic dynamics on the shore of the lakes, and that this participation depends on the evapoconcentration process occurring in the region. Therefore, soil acts like a nonreactive matrix depending on the natural concentration process. In addition, our results reinforced the different geochemical characteristics of the studied saline-alkaline lakes and highlights the importance of robust passive sampling techniques in the context of metal/metalloid speciation in environmental analysis.