Effects of alkaline liquid fertilizer on bioavailability,accumulation and migration of heavy metals in Sauropus androgynus-soil

【Objective】 To evaluate quality and safety of Sauropus androgynus in the high geological background area of Hainan, and to investigate effects of alkaline liquid fertilizer on heavy metal reduction in the soil, reduce heavy metal accumulation of S. androgynus from soil, with an aim to provide theoretical basis for improving soil environment and promoting safe production of S. androgynus.【Method】 A field experiment was carried out by using alkaline liquid fertilizer and compound fertilizer to determine heavy metal lead(Pb), chromium(Cr), arseic(As) speciation characteristics and migration regularity in S. androgynus-soil, and to investigate effects of alkaline liquid fertilizer on accumulation of migrated heavy metal in S. androgynus. Correlation analysis was operated to analyze relationship between soil property, heavy metal speciation and heavy metal content in parts of S. androgynus to determine the environmental factors affecting the migration of heavy metals Pb, Cr, As from S. androgynus to soil.【Result】 Compared with compound fertilizer treatment(CF), the soil organic matter(OM) and cation exchange capacity(CEC) in alkaline liquid fertilizer treatment(AF) increased by 9.1% and 8.4%, respectively. Pb, Cr and As mainly existed as residues in the soil. Alkaline liquid fertilizer reduced exchangeable Pb, Cr and As by 75.5%, 25.9% and 0.8%, respectively;while compound fertilizer increased exchangeable Pb and Cr by 36.8% and 26.5%, respectively. After applying alkaline liquid fertilizer, Pb, Cr and As in S. androgynus decreased by 73.0%, 59.4% and 34.0%, respectively, while Pb in CF significantly increased by 39.3%(P<0.05, the same below), but the content of Cr and As did not change significantly(P>0.05). Pb and Cr accumulation in S. androgynus decreased by the order of root>stem>leaf>branch>edible branch, migration decreased in the order of TF2(stem→leaf) ≥ TF1(root→stem) > TF3(leaf→branch) > TF4(root→edible branch), and Pb, Cr and As were mainly accumulated in the roots, which could well migrate to leaves, but poorly to edible branch.Enrichment coefficient of Pb decreased by 50.0%, while enrichment coefficients of Pb and Cr in all parts of S. androgynus were significantly increased by compound fertilizer. TF4 of Pb, Cr and As significantly decreased by 73.3%, 43.6% and 46.9% respectively in AF, while TF4 of Pb and TF1 of As significantly increased by 30.0% and 11.0% in the compound fertilizer treatment. Soil pH, CEC and OM were significantly or extremely significantly(P<0.01) negatively correlated with the content of Cr, Pb and As in branches and edible branches.【Conclusion】 Using alkaline liquid fertilizer is an agronomic measure that can provide plant nutrients, reduce heavy metal bioavailability and reduce accumulation and migration of heavy metals in S. androgynus, which provides an effective ecofriendly and sustainable method for the safe production of S. androgynus.