Effects Of Amendments And Nutritional Regulation On Uptake Of Arsenic With Plants In As-contaminated Soils

In this paper, in order to find new methods and ways in safe utilization of fields with high arsenic content, laboratory incubation experiments and pot culture experiments were conducted to investigate the regulating effects of several amendments (ferrihydrite, goethite, gibbsite and Mg/Al layered double oxides) and nutrient elements (N, P, K, Ca, Mg, Fe, Mn) addition during the seedling stage on the bioavailability of arsenic in contaminated soils. The main results were as follows:1. Goethite and ferrihydrite showed a better immobilization effect of arsenic (As) than Mg/Al-LDO and gibbisite, and could be applied as amendments to immobilize As in soils. The contents of available As in soils were decreased by1.89%-64.15%by adding goethite, ferrihydrite and gibbsite, while they were increased by adding Mg/Al layered double oxides. The contents of residual As in soils by adding goethite and ferrihydrite were obviously elevated.2. The application of four amendments reduced the contents of arsenic in crops, ferrihydrite showed the best effect, gibbisite was better, and goethite showed the worst results. Compared to the control pots, not only the enrichment of arsenic in pakchio cabbage, but also the arsenic concerntration and enrichment capacity of overground and underground part of pakchio cabbage were dropped dramatically when adding ferrihydrite, gibbsite and Mg/Al layered double oxides; In addition, the application of four amendments inhibited the transport of arsenic form underground part to the overground part in pakchio cabbage at the same time, it dropped greatest when adding ferrihydrite, and the range was34.03%-69.44%; Compared with four different adding proportion, the availability of the arsenic to crops showed the largest decline under the addition level of1.0%by adding ferrihydrite, goethite and Mg/Al layered double oxides, while0.25%or0.5%was proved to be the best addition level for gibbsite.3. The pakchoi cabbage showed a greater enrichment capacity of arsenic than maize, so pakchoi cabbage is more suitable than maize for planting in the soils with high arsenic concentration. The arsenic concentrations in the overground part (edible part) of the pakchoi cabbage were reached up to0.80mg·kg-1when grown in soils with190mg·kg-1of total arsenic concentration, which substantially exceeded the limited value of national food safety standards (0.5mg·kg-1), however, the grains of maize harvested from the same soils were safely edible; With the increasing concentration of total arsenic in soils, the arsenic concentrations in different organs and the enrichment of arsenic in plants both showed a corresponding growth, but they were presented different correlation. Arsenic concentrations in the overground part of pakchoi cabbage were significantly lower than that in the root, and the distribution trends of arsenic in mature maize was:root> leaf> straw> grain.4. The addition of different levels of N、P、K、Ca、Mg、Fe and Mn inhibited the transportation of arsenic upto the overground part from the underground part; Futher more, the addition of N、P、K、Ca、Mg and Fe was able to reduce the arsenic content in the grain of maize, the enrichment amount of arsenic in mazie, and inhibited the transportation of arsenic upto the grain from the root;The addition level of N1536mg·kg-1、P355mg·kg-1、K1071mg·kg-1、Ca549mg·kg-1, Mg220mg·kg-1and Fe25.60mg·kg-1showed a better results in reducing the absorption capacity; Arsenic with N、P、K、Ca and Fe existed a dual effect, it was closely related with the addition amount of the nutrients.