Study On Co-remediation Effects Of Silicon Fertilizers And Birnessite-modified Biochar For Arsenic And Cadmium Pollution In Paddy Soils

The heavy metal pollutions of soil are serious with the economy and industry development,especially in the south of China where the mining and agriculture proceed simultaneously.the Cd and As pollution occurred simultaneously in most of payy soils,so we focus on the As and Cd remediation method in payy soils.At first,a field experiment was established to support the hypothesis that application of different silicon(Si)fertilizers can simultaneously reduce Cd and As concentration in rice grain.1?The “semi-finished product of Si-potash fertilizer” treatment at the high application of 9000 kg/ha(NP+S-KSi9000)significantly reduced the As concentration in rice grain by up to 20.1%,compared with the control.2?Si fertilization reduces the Cd concentration in rice considerably more than the As concentration.All Si fertilizers apart from sodium metasilicate(Na2Si O3)exhibited a high ability to reduce Cd concentration in rice grain.The Si-calcium(Ca Si)fertilizer is most effective in mitigation of Cd concentration in rice grain.The Ca Si fertilizer applied at 9000 kg/ha(NPK+Ca Si9000)and 900 kg/ha(NPK+Ca Si900)reduced the Cd concentration in rice grain about 71.5% and 48.0%,respectively.In the second experiment,a novel biochar was successfully prepared through birnessite modification to improve its capability to simultaneously adsorb As and Cd in water and soil.1? The saturated adsorption capabilities of birnessite-modified biochar(BRB)were as large as 3543 mg/kg for As(III),2412 mg/kg for As(V)and 9068 mg/kg for Cd calculated by Langumir isotherm model,much higher than the corresponding non-modified biochar(4335 mg/kg for Cd,no sorption for As).2? The amounts of As(III)or As(V)and Cd sorptions on BRB were both slightly increased in the coexistence of As and Cd in the aquatic solutions.3? After six weeks incubation in the contaminated soil,BRB show a potential trend in decreasing the As and Cd concentrations in pore water under unflooded and flooded conditions,respectively.These results suggest that the birnessite-modified biochar is a potential sorbent for simultaneous immobilization of heavy metals,especially As and Cd in environmental and agricultural systems.