Arsenic distribution and metabolism genes abundance in Paddy soils from Punjab and Sindh provinces, Pakistan

Abstract

Arsenic (As) is naturally found in the Earth’s crust at certain concentration above which it refers as toxic. Due to various anthropogenic activities as well as natural processes, As concentration reaches the threshold level. The fate of As in soil is influenced by biotransformation, immobilization, confinement process, and soil properties. The aim of the present study was to examine the levels and species of As, metabolism genes, and correlation with paddy soils’ physico-chemical characteristics from Punjab and Sindh provinces, Pakistan. Results of the present study revealed the presence of significant levels of As and metabolism genes in different areas of Punjab and Sindh, Pakistan. The level of total As ranged 6–80 μg/kg, and relatively low levels of mono-As, di-As, and Tri-As were found in paddy soils. Higher abundance of arsM were recorded 1.5 × 104 (copy number/g) compared with other genes, suggesting arsM role in As biotransformation. Redundancy analysis (RDA) shows significant relationship of (i) aioA and arsM with Tri-As and organic matter (OM) and (ii) arrA with As and dimethylarsinic acid (DMA). The results suggest that the occurrence of As-methylated species in paddy soils is due to microorganisms and greatly influenced by the physico-chemical properties of paddy soils. The results will be helpful to higher authorities for the management of As-contaminated paddy soils in Pakistan.