Assessment of arsenic availability in soils using the diffusive gradients in thin films (DGT) technique—a comparison study of DGT and classic extraction methods

Abstract

This study was conducted to evaluate the feasibility and accuracy of available arsenic (As) measurement in soils using the diffusive gradients in thin films (DGT) technique and to shed further light on the risk evaluation of As-contaminated soils. A bio-indicator method was used to evaluate the dependence of As concentrations in plant tissues (edible rape) on the As concentrations measured by other methods. DGT, extraction of soil pore water, 0.5 M NaHCO3, 1 M HCl, 1 M NH4Cl, 0.5 M NH4F, 0.1 M NaOH and 0.25 M H2SO4 extraction methods, as well as total As content in the soil were employed in this study. Edible rape was grown in 43 soils containing different concentrations of As. A better correlation was obtained between the As concentrations in plant tissues and the As concentrations measured by DGT than between plant concentrations and those measured by other methods. The coefficients of determination (R(2)) before and after growth of edible rape were 0.84 and 0.83, respectively. Levels of As in plants and in soil pore water were also closely related: the coefficients of determination (R(2)) between these variables before and after growth of edible rape were 0.83 and 0.81, respectively. Measurements from the chemical extraction methods were inferior to those from DGT and soil pore water. Levels of As in plants were more scattered and nonlinear with respect to total soil As content (R(2) = 0.27). The As measured by DGT closely reflected the pool of plant-adsorbed As. From the data obtained in this study, we can conclude that DGT is an effective technique for the prediction and assessment of As bioavailability in soils.

Effect of exogenous phosphate on the lability and phytoavailability of arsenic in soils

“…In a previous study from our research laboratory, DGT measured As concentration had a better correlation with plant As, and had a closer reflection of phyto-available As pool than chemical extracted As (Wang et al 2014). For measurement of P in soil, numerous researches had demonstrated the feasibility and accuracy of DGT method (Mason et al 2010, Six et al 2012, Six et al 2013, Six et al (2014) indicated that DGT method relates best with yields compared to the established soil P tests Olsen and AEM (anion exchange membranes).…”

“…However, extraction procedures provided an unrealistic response to given chemical agents, and the extracted P(As) species are unlikely to represent the true available fraction, especially when the speciation or complexes of P(As) changed during the P-As interaction processes. A more precise reflection of the phytoavailable pool of As could be achieved when using the method of DGT (Wang et al 2014). DGT method, which based on Fick's first law of diffusion, is a dynamic in-situ technique for the determination of labile metal/metalloid in soil (Zhang et al 2001).…”

“…As an analogue of P, arsenic could also be measured by FH-based DGT in various medium including soils and waters (Fitz et al 2003, Panther et al 2008. Wang et al (2014) ACCEPTED MANUSCRIPT 6 / 25 found that DGT measured soil labile As had a better correlation with plant As. It could reveal a more precise reflection of phytoavailable As pool than chemical extracted As.…”

“…Some areas in China, especially in Hunan province, have historical As contamination caused by realgar mine or tailing lagoon failure (Liao et al 2005). Total As in soil contains large fractions unavailable to biota (Wang et al 2014), therefore identifying the 'available' fraction of As in soils is urgently needed (McLaughlin et al 2000, Mojsilovic et al 2011. Manipulating the bioavailability of As in soils using chemical or biological means is an universal approach in remediation of Ascontaminated soils (Bolan et al 2013).…”

Monitoring the Activated Sludge Activities Affected by Industrial Toxins via an Early-Warning System Based on the Relative Oxygen Uptake Rate (ROUR) Index

“…Industrial wastewater harms the biochemical treatment units of WWTPs and seriously disturbs their operation by inhibiting the activated sludge activities in WWTPs [19]. The ratio of 5-day biological oxygen demand (BOD 5 ) to chemical oxygen demand (COD), designated as B/C, can be significantly reduced by industrial wastewater to <0.3, indicating a poor biodegradability and causing the paralysis of the biochemical treatment units [20,21]. Due to the shock load and intermittent impacts of PTEs, cyanide and other toxic substances in industrial wastewater, WWTPs might lose efficiencies in removing pollutants to some extent and the effluent quality is affected [21,22], consequently increasing the operation cost [23].…”