ABSTRACT
Potentially toxic metals (PTEs) and antibiotic resistance genes (ARGs) present in bio-wastes were the major environmental and health risks for soil use. If pyrolyzing bio-wastes into biochar could minimize such risks had not been elucidated. This study evaluated PTE pools, microbial and ARGs abundances of wheat straw (WS), swine manure (SM) and sewage sludge (SS) before and after pyrolysis, which were again tested for soil amendment at a 2% dosage in a pot experiment with a vegetable crop of pak choi (Brassica campestris L.). Pyrolysis led to PTEs concentration in biochars but reduced greatly their mobility, availability and migration potential, as revealed respectively by leaching, CaCl2 extraction and risk assessment coding. In SM and SS after pyrolysis, gene abundance was removed by 4-5 orders for bacterial, by 2-3 orders for fungi and by 3-5 orders for total ARGs. With these material amended, PTEs available pool decreased by 25%-85% while all ARGs eliminated to background in the pot soil. Unlike a >50% yield decrease and a >30% quality decline with unpyrolyzed SM and SS, their biochars significantly increased biomass production and overall quality of pak choi grown in the amended soil. Comparatively, amendment of the biochars decreased plant PTEs content by 23-57% and greatly reduced health risk of pak choi, with total target hazard quotient values well below the guideline limit for subsistence diet by adult. Furthermore, biochar soil amendment enabled a synergic improvement on soil fertility, product quality, and biomass production as well as metal stabilization in the soil-plant system. Thus, biowastes pyrolysis and reuse in vegetable production could help build up a closed loop of production-waste-biochar-production, addressing not only circular economy but healthy food and climate nexus also and contributing to achieving the United Nations sustainable development goals.
ABSTRACT
Objective: To study the selenium(Se) chemical forms in Se enriched tea by fertilizing sodiums selenite in soil and tea naturally high in Se and compare their antioxidant function. Methods: The Se enriched tea was produced by fertilization of sodium selenite through biological transformation of tea tree in low Se content soil. Five groups of rats were fed basal low Se diet and basal diet with sodium selenite, extractions of low Se tea, Se enriched tea by fertilizing with sodium selenite, and tea naturally high in Se. The Se chemical forms and antioxidant function of rats fed with different Se resource were detemined after 8 wks. Results: The proportion of organic forms of Se and Se protein were almost the same in Se enriched tea and tea naturally high in Se. The Se absorption and utilization rates were 65.41%, 68.05% ,and 70.49% for sodium selenite, Se enriched tea and tea naturally high in Se respectively. It showed that the availability of Se in Se enriched tea was higher than that in sodium selenite. The Se content of blood and liver, GSH Px activity were significantly increased by feeding extraction of Se enriched tea compared with control, sodium selenite and low Se tea.. Conclusion: The biological effect of organic form Se in Se enriched tea is higher than that of sodium selenite, and the Se enriched tea produced by fertilizing sodium selenite in low Se soil is as effective as tea naturally high in Se. The Se enriched tea is safe and effective in increasing the Se intake of both human and animals in low Se area.
