Phytotoxicity of Radish (Raphanus sativus) Seedling By Acids Introduced into Agricultural Soil By Chemical Incidents.

Acids are used in various chemical processes; pickling, purifying, neutralization, alkylation, and mining processing, etc. There have been many reports of acid spill into agricultural soil during transportation and storage. Acids in soil may lower the soil pH and increase the bio-accessibility of heavy metals in the soil. We assessed phytoxicity of sulfuric acid (H₂SO₄) and nitric acid (HNO₃) on radish (Raphanus sativus) seedling emergence and growth and investigated the cause of toxicity of radish seedling by H₂SO₄ and HNO₃. We selected three agricultural soil; one was soil nearby abandoned mine, other was soil around the road, and the other was uncontaminated field soil. We mixed H₂SO₄ and HNO₃ in the three soil uniformly and adjusted the acid concentration in soil to 7 different levels (0, 10, 100, 500, 1000, 2000, and 5000 mg kg^-1). Radish seeds were exposed at the test soil during 14 days in plant growth chamber. After 14 days, germination rate, fresh weight, elongation, and chlorophyll content of leaves of radish seedlings were used as toxicity endpoints. We predicted the toxic values (LC₅₀, EC₅₀, NOEC, and LOEC, etc.) of sulfuric acid and nitric acid on radish seedling emergence and growth using Probit model (germination rate) and Gompertz model (fresh weight, elongation, and chlorophyll content). Also, we measured the pH and dissolved heavy metal concentration of acid-mixed soil. Through the correlation analysis of toxic value of two acids on radish and soil pH and dissolved metal concentration, we have identified toxic factors of acid contaminated soil for germination and seedling growth of radish.

Acknowledgement: This subject is supported by Korea Ministry of Environment(MOE) as "The Chemical Accident Prevention Technology Development Project."(2016001970003)

Keywords: Chemical spill, Radish (Raphanus sativus), Sulfuric acid, Nitric acid, Dissolved heavy metal