Study On Chemical Speciation Of Cadmium In Acidic Soil And Its Inactivation

Due to acid rain, acidic wastewater emissions and unreasonable fertilization, soil acidification is more serious in some area of china, the activation degree of heavy metal in soil is increased day by day. Bioavailability and chemical speciation of heavy metal changes therefore. Cadmium is one of the most common pollutants of heavy metals in farml and in our country. The risk that heavy metals join the food chain in soil to plant is enhanced owing to the availability content of heavy metal increasing in the environment. At present, The experiment rarely studies the morphological changes of the cadmium in the different soil and the bioavailability of the cadmium. This study focuses on the effect of different fertilization, simulated acid rain and improvers added on chemical speciation of cadmium. Our study will provide the theoretical basis for the repair of contaminated soil and environmental risk assessment.In order to study optimization of single chemical extraction of cadmium in soil, different concentrations of CaCl2were used to extract available cadmium from sierozem and paddy soil with different extraction times. It indicated that0.1mol/L CaCl2was suitable in available cadmium extracting for acidic soil.Based on a long-term stationary experiment in the Ecological Experimental Station of Red Soil, Chinese Academy of Science, the characteristics of cadmium content and soil properties in the vertical distribution of long-term located fertilization plots were studied. Compared with chemical fertilizer, cadmium concentration and available contents were22.9times,5times in the0-20cm of organic manure plots respectively. It indicated that organic fertilizer can significantly increased the concentration of cadmium and its availability. Different simulated acid rain solution leached the paddy soil for48hours. The analysis on changes of cadmium chemical speciation,pH and cadmium content, Demonstrated that acid rain increased the activity of cadmium.The transformation processes of cadmium in the acid soils were characterized and the effect of three soil amendments (lime, superphosphate and sodium sulfide) on their chemical speciation in the soil studied Lime is suitable for remediating cadmium contaminated acid soils. With the increase of lime, soil pH gradually increased and exchangeable cadmium transformed to other speciation to reduce activity of cadmium; with the increase of superphosphate, the soil pH decreased, the content of exchangeable cadmium also decreased; the effects of sodium sulfide on soil pH and chemical speciation of cadmium were not obvious.