Key factors influencing arsenic phytotoxicity thresholds in south China acidic soils

Fenghua Ding; Guo Wang; Shuxin Liu; Zhenli L He

doi:10.1016/j.heliyon.2023.e19905

Key factors influencing arsenic phytotoxicity thresholds in south China acidic soils

Heliyon. 2023 Sep 6;9(9):e19905. doi: 10.1016/j.heliyon.2023.e19905. eCollection 2023 Sep.

Authors

Fenghua Ding^{1

2

3}, Guo Wang², Shuxin Liu⁴, Zhenli L He³

Affiliations

¹ Institute of Ecology, Lishui University, Lishui, Zhejiang 323000, China.
² Department of Resources and Environmental Sciences, Fujian Agriculture and Forestry University, Fuzhou, Fujian 350002, China.
³ Institute of Food and Agricultural Sciences, Indian River Research and Education Center, University of Florida, Fort Pierce, FL 34951, USA.
⁴ Department of Environmental Engineering, Lishui Vocational & Technical College, Lishui, Zhejiang 323000, China.

Abstract

Arsenic (As) toxicity threshold values (TTVs) for plants are fundamental to both establishing regional As reference values in soil and performing risk assessment. However, TTVs vary with plant species and soil types. In this study, a hydroponic experiment with 16 plant species was conducted to screen the most As-sensitive plant species. The results showed that the EC₂₀ (available As concentration at which shoot biomass or height is inhibited by 20%) values were 1.38-104.4 mg L^-1 for shoot height and 0.24-42.87 mg L^-1 for shoot fresh biomass. Rice was more sensitive to As toxicity than the other species. Therefore, it was chosen as the ecological receptor in the pot experiment on As phytotoxicity in nine types of soils collected from Fujian Province in South China. The EC₁₀ and EC₂₀ with respect to rice shoot height were 3.72-29.11 mg kg^-1 and 7.12-45.60 mg kg^-1, respectively. Stepwise regression analysis indicated that free iron oxide concentration is the major factor that affects As bioavailability in soil, and EC_x (x = 10, 20, and 50) of soil available As for shoot height was positively related to free iron oxide concentration in soil. In addition, soil cation exchange capacity, clay (<0.002 mm) content, and exchangeable magnesium content are also important factors influencing As phytotoxicity in acidic soils. The regression models can be used to predict As phytotoxicity in acidic soils.

Keywords: Free iron oxide; Plant tolerance index; Regression model; Rice; Risk assessment; ecological receptor.