Influence Of Chemical Additives On Bioavailability Of Soil Arsenic And Its Preliminary Mechanisms

Arsenic is a priority pollutant to be controled in China. With the development of socio-economy and industry, many countries around the world are facing serious arsenic contamination. Nowadays, remediation of arsenic contaminated soil is a hotspot of scientific research and application around the world. Chemical remediation is a feasible and practical method to repair polluted soil. The purpose of this project was to study the influence of chemical additives on bioavailability of soil arsenic and its preliminary mechanisms, to select the best effective chemical additives used in agricultural production, and then to provide reliable measures to control soil arsenic contamination and to assure the security of agricultural products. Based on the status quo of the soil pollution in China, a constant temperature and humidity experiment and pot experiments using a hyperaccumulator Pteris vittata L., a food crop Triticum aestivum L. , and an oil crop Brassica napus L. were carried out to understand the effects of adding different chemical additives on the growth of the plant, the uptake and accumulation of arsenic by the plants as well as its preliminary mechanisms. The main results were as follows:1. Application of limestone, ersatz zeolite, iron powder, titania, red mud and cinder reduced markedly the soil available As under the conditions of constant temperature and humidity experiment, with the percentage decreased by 63.7%, 63.6%, 53.8%, 41.5%, 54.6% and 49.9%, respectively; application of EDTA, compost, calcium superphosphate, rock phosphate and sodium polyacrylate increased significantly the soil available As, with the percentage increased by 32.3%, 50.2%, 58.7%, 44.6% and 104%, respectively, of which the sodium polyacrylate was the most effective. The results showed that application of chemical additives could passivate or activate As in polluted soil by reducing or increasing the availability and movability of soil As.2. Application of EDTA, compost, calcium superphosphate, rock phosphate and sodium polyacrylate increased the amount of the soil available As and the growth and arsenic uptake of P. vittata L. in pot experiment. Calcium superphosphate was the most markedly effective additives, with an increasing percentage of 76% in biomass over the control. EDTA was the most markedly effective in increasing arsenic uptake by P. vittata L., with the increasing percentage of 21%. And the greatest arsenic accumulation of P. vittata L. went to calcium superphosphate, which the increasing percentage was 69%.3. Application of limestone, ersatz zeolite, iron powder, titania, red mud and cinder reduced the soil available As and arsenic uptake of wheat and promoted its growth in pot experiment. Iron powder, red mud and cinder reduced markedly arsenic uptake of wheat with a decreasing percentage of 26% and 35% over the control.4. Application of EDTA, compost, calcium superphosphate, rock phosphate and sodium polyacrylate increased soil neutral phosphatase activity and soil urease enzyme activity, but reduced soil sucrose enzyme activity of potting soil grown P. vittata L. The change range of soil neutral phosphatase activity, urease enzyme activity and sucrose enzyme activity are 2%-lll%, 3%-19% and 9%-36%, respectively. Application of limestone, ersatz zeolite, iron powder, red mud and cinder increased soil neutral phosphatase activity and soil urease enzyme activity, and reduced soil sucrose enzyme activity of wheat and rape, with the change range of soil neutral phosphatase activity, urease enzyme activity and sucrose enzyme activity over the control being 2%-111%, 3%-19% and 9%-36%, and 19%-54%, 4%-16% and 0.6%-33%, respectively.5. Application of iron powder and titania promoted the growth and reduced arsenic uptake of vegetables in pot experiment, with the decreasing percentages of 24% and 25%, 3% and 8%, 31% and 11%, 45% and 66% and 2% and 42%, respectively, for B. campestris L.ssp.chinensis, B. juncea var.50-1, B. juncea var.Minxianniuweishao, B. napus var.Suyou15 and B. napus var.D050-1.6. Application of iron powder and titania reduced soluble protein content in vegetables in pot experiment and the decreases of soluble protein content in napus var.Suyou15 were 21% and 39%, respectively. There was no obvious difference among the content of Chlorophyll a, Chlorophyll b and total Chlorophyll after addition of iron powder and titania. 7. Application of iron powder and titania relieved oxidative stress in vegetables, which was mainly showed as a decrease in activity of SOD and CAT, and the content of GSH and MDA in the shoots of vegetables, with the change range of 6%-40%, 1%-22%, 1%-20%, and 0.3%-23%, respectively.