Arsenic Cleanup Goals in Soil-Water-Rice-Human Continuum: Interplay of Amendments

Abstract

Calcium silicate (CaSiO3) can affect the bioavailability of arsenic (As) in the soil water-rice system, but it is not clear how its interaction with farmyard manure (FYM) and vermicompost (VC) affects As build up in the soil and in turn uptake by rice and human exposure. The mechanistic pathways for mitigating As toxicity in rice and its risk to human health were assessed using a contaminated paddy-rice system with seven amendment regimes involving CaSiO3, FYM, and VC. The bioavailable and total As build-up of 1243 and 2550 g ha−1 respectively from control plots, while the amended plots had 672.8 and 502 g ha−1 reduction on average. The transfer of As from soil to grain was lesser in treated (4.3%) compared to control (6.5%). In treated plots, grain nutrient quality, such as Zn and Fe concentration, improved by 4.1–28.4% and 10.2–30.2%, respectively. The average incremental lifetime cancer risk of As associated with ingestion of such rice is 2.4 and 1.5 times lower on combined (0.47× 10−3–0.54× 10−3) and individual (0.74× 10−3–0.86× 10−3) application of amendments over control (1.13 × 10−3). To achieve the desired hazard quotient of < 1, the cleanup goals for total As in root, shoot, grain, and polished and cooked rice are 11.72, 3.99, 1.03, 0.28, 0.25, and 0.075 (mg kg−1), respectively. CaSiO3 with and without organic can reduce As concentration in the root, shoot, grain, polished rice, and cooked rice below the cleanup goals.