Arsenic contamination of the soil-wheat system irrigated with high arsenic groundwater in the Hetao Basin, Inner Mongolia, China

- Arsenic-contaminated groundwater led to As accumulation in irrigated soils.
- High As groundwater irrigation increased As bioavailability in topsoils.
- Wheat grain As was positively correlated with bioavailable As forms in topsoils.
- Elevated As in wheat grains was related to high As groundwater irrigation.
- Less problematic water resources were suggested for wheat irrigation.

As one of the most important crop in the world, wheat (Triticum aestivum L.) was irrigated with low As water and high As water. However, little is known about As cycling in the soil-wheat-water system. Two wheat fields (site G and site Y), irrigated with high dissolved As (178 μg L− 1) groundwater and low dissolved As (8.2 μg L− 1) surface water, respectively, were systematically sampled in the Hetao Basin, including irrigation water, soils and plants. The annual As (including dissolved As and suspended As) input per m2 was estimated at 140 and 36.7 mg in site G and site Y, respectively. Topsoils of site G contained relatively higher As content (average 18.8 mg kg− 1) than those of site Y (13.8 mg kg− 1). Arsenic content of wheat grains in site G is systematically higher than in the site Y, which were positively correlated with non-specifically sorbed-As and amorphous Fe/Al oxide-bound As in topsoils. Arsenic-contaminated groundwater led to As accumulation in irrigated soils and the increase in As bioavailability, and subsequently resulted in the increase in As content of wheat grain. It suggested that less problematic water resources should be used for wheat irrigation in order to avoid As accumulation in the soil-plant system.