Spatial Distribution of As and Cd in Co-contaminated Soils Within the Rice Root Microzone

Soil samples were collected from the As and Cd co-contaminated demonstration area to analyze the spatial distributions of As and Cd in soils within the rice root microzone using the treatment of soil cubes (50 mm × 50 mm × 50 mm). The results indicated that there was no significant difference in the spatial distributions of total As or Cd in the microzone with the percentage of root weight, horizontal distances (HD), and vertical depths (VD). Interestingly, available As or Cd increased with the increasing HD, and both of them showed a significant difference (p < 0.05) between < 75 mm and ≥ 120 mm. The availability of As or Cd increased from the center to the edge of the rice root microzone. Moreover, the risk assessment code (RAC) showed that the site with a high potential risk of As or Cd was located on the edge of the rice root microzone. This phenomenon implied that cultivating paddy rice in the low potential risk microzone might have a low accumulative risk.