Determination of Suitable Extractant for Estimating Plant Available Arsenic in Relation to Soil Properties and Predictability by Solubility-FIAM

Abstract

Extractant for estimating plant available arsenic (As) in soil has not been universally established. Moreover, to assess and monitor the complex chemical behaviour of arsenic (As) in soil and subsequently its transfer in crops, a suitable extraction protocol considering the soil properties in relation to crop uptake is required. For this purpose, a pot experiment was conducted to evaluate the suitability of the extractants for determination of extractable As in soil and risk assessment by solubility-free ion activity model (FIAM) with rice (variety: Sushk Samrat) as the test crop. Soil in bulk was collected from six locations of Indo-Gangetic Plain of Bihar, India, varying in physicochemical properties to conduct the pot experiment using five doses of As (0, 10, 20, 40 and 80 mg kg−1). Six extractants namely 0.2 (M) NH4-oxalate, 0.05 (N) HCl + 0.025 (N) H2SO4, 0.5 (M) KH2PO4, 0.5 (N) NH4F, 0.5 (M) NaHCO3 and 0.5 (M) EDTA were used. The results revealed that 0.5 (M) KH2PO4 gave the best correlation with the soil properties and crop uptake and can be considered a suitable extractant of As. Regardless of the As dose and the soil type used, in rice tissue, concentration of As followed the order root > straw > leaf and grain. As high as 94% variation in As content in rice grain could be explained, when 0.5 (M) KH2PO4 extractable As is being used as input for solubility-FIAM. Extractable As cannot be determined by atomic absorption spectrophotometer (AAS) coupled with vapour generation accessory (VGA) when 0.5 (M) EDTA was used as an extractant.

Evaluation of Different Extractants to Estimate Bioavailable Arsenic in Soil

“…The problem with CaCl 2 is the presence of chloride. The existence of chloride (Cl) in nal prepared samples leads to polyatomic ions 40 Ar 35 Cl and 35 Cl 16 O formation in a smaller concentration of As in samples and hamper its determination in ICP-MS. Thus an acidbased extractant may be a suitable option for As determination in ICP-MS. Further, some studies suggested that due to higher viscosity and variation in surface tension of H 3 PO 4 and H 2 SO 4 , changes in droplet size distribution and nebulization e ciency reduce the signal intensity in ICP-OES (Yoshimura et al, 1990).…”

“…Some reports have correlated bioaccessible As with in-vitro analysis or human oral bioaccessibility of As (Bari et al, 2021;Li et al, 2015;Fernández-Caliani et al, 2019). A few studies have set out to derive relationships between forms of As in soils and plant As content (Raj et al, 2021;Yu et al, 2016). Therefore, a suitable analytical approach is necessary to assess readily available forms of As in soil.…”

Varietal Differences Influence Arsenic and Lead Contamination of Rice Grown in Mining Impacted Agricultural Fields of Zamfara State, Nigeria

“…There are both direct and indirect evidences to suggest that As is held in soils by sediments by oxides (e.g. of Fe, Mn, Zn) through the formation of inner-sphere complexes via ligand exchange mechanism (Kumari et al, 2021;Raj et al, 2021). Iron appeared highly efficient to sequester As and to restrict As acquisition by rice (Chowdhury et al, 2018a).…”

Determination of bioavailable arsenic threshold and validation of modeled permissible total arsenic in paddy soil using machine learning

“…Arsenic in soil is present in both the solution and solid phases. The As may be in the form of organic and inorganic complexes (present in soil solution), adsorbed ions and compounds (clay and organic colloids), bound to secondary minerals and precipitated oxides of iron (Fe) and manganese (Mn), carbonates, and phosphates or complexed with organic matter and free ions (Raj et al., 2021). Total elemental concentrations within the soil offer little insight into the potential bioavailability of the elements (such as As), which may cause metal(loid) sequestration and recycling within the soil environment under the influence of various soil parameters (Kumari et al., 2021).…”