The Research On Phytoremediation And Passivation In The Acid Red Soil Of Low Cadmium Pollution

The heavy metal pollution condition of farmland soil is not optimistic in our country, especially cadmium pollution of acid red soil region, south "cadmium rice" happened frequently, a serious threat to our country's food safety and human health, so, pollution control is imminent. In the recent years, stabilization and phytoextraction have attracted more and more attention as the two important methods for in-situ remediation of heavy metal contaminated soil. Based on previous investigation and research, the study conduct phytoextraction and stabilization on field scale demonstration and efficiency evaluation in southern typical low cadmium pollution of acid red soil. The main results were as follow:?1? Demonstration area is located in Xiangtan county of Hunan province, with soil pH 4.7 and soil total Cd concentration in arable layer 0.49⁰.71 mg kg^-1. In demonstration area, the growth of Sedum plumbizincicola is in good condition, shoot dry weight is 1.8⁵.9 t hm^-2, Cd concentration is 53.1⁹4.9 mg kg^-1, Cd removal amount is 169³53 g hm^-2, the average is 244 g hm^-2. After the first season of phytoextraction, soil Cd concentration?1 hm2? decreased from 0.49⁰.71 mg kg^-1 to 0.32⁰.56 mg kg^-1, with removal rate of 11.5³4.7%, on average 21.7%. After the second season phytoextraction soil Cd concentration in one plot decreased from 0.64 mg kg^-1 to 0.29 mg kg^-1, which is lower than the soil environmental quality of the second grade standard limits 0.3 mg kg^-1?GB 15618-1995?. The total removal rate reached 54.7% after two times of phytoextraction. Soil profile analysis showed that lower concentration of cadmium soil is mainly focused on the 2¹5 cm, in line with S. plumbizincicola root system distribution.?2? Field and pot experiment results showed that brown rice Cd concentration of low accumulation rice varieties grown in remediated soil was lower than 0.2 mg kg^-1, but for ordinary rice varieties proper stabilization was still needed.?3? The field demonstration of stabilization results indicated that the application of sepiolite and lime composite agents increased soil pH by 1.5².3 units, decreased soil CaCl₂ extractable Cd concentration by 85% or more, and the rice grain Cd kept less than national standard.This research provides the basic data for the remediation of large areas of low cadmium pollution soils in our country.