| Improper disposal of livestock manure could cause non-point source contamination of estrogen.17?-Estradiol(E2)is the most biologically active of natural estrogens,and the migration of E2 in manure poses a potential threat to fish reproduction and human health.A portion of E2 from livestock manure can be degraded in aerobic composting process for the excrement,whereas there is still E2 residue in the compost product.Although biochar is used as an additive for aerobic composting,studies reported on the effects of biochar on E2 degradation and bioactivity during livestock manure composting are few.More research about utilization of biochar to remove E2 from livestock manure and to weaken bioactivity of estrogen is needed.Therefore,two sets of composting tests were carried out in this study.One group contained chicken manure/corn straw composting system and the other was chicken manure/corn stalk/mushroom residue composting system,with the treatment without biochar as control(Contro11 and Contro12).Wheat straw biochar and rice husk biochar were respectively added at ratios of 5%,10%and 15%(compared to dry weight of chicken manure)based on Control1 and Contro12 as treatments f'or adding biochar.In this study,the physicochemical properties of the compost with biochar,the degradation of E2,the proliferative effect of estrogen on human breast cancer cells(MCF-7 cells)and its influencing mechanism were investigated.The main findings and conclusions are as follows:1.The addition of 5%,10%,15%wheat straw biochar and rice husk biochar can promote the reduction of C/N ratio and reduce NH3 emission during composting.In the chicken manure/corn straw composting system and chicken manure/corn straw/mushroom residue composting system,adding two types of biochar maked the C/N reduction reach 6.59?9.26,which was higher than the corresponding control.The average NH3 concentration per day emitted by the piles can be reduced by 13.71%-89.34%in the biochar-supplemented treatments.At the same addition ratio,rice husk biochar with larger specific surface area and pore volume had stronger inhibition effect on NH3 volatilization than wheat straw biochar.Rice husk biochar is suggested to be added into compost at a ratio of 15%to reduce the volatilization of NH3.2.The addition of biochar accelerated the degradation of E2 during composting.The concentration of E2 in composting pile decreased the most on condition that the adding ratio of wheat straw biochar and rice husk biochar was 15%.In the chicken manure/corn straw composting system,the addition of two types of biochar reduced the E2 content by 70.72%?78.04%,which was higher than that of Controll(69.64%).In chicken manure/corn straw/mushroom residue composting system,the addition of wheat straw biochar and rice husk biochar reduced the E2 content by 73.52%?88.08%,which was higher than that of Control2(67.76%).3.The utilization of biochar promoted the growth of three kinds of E2 degrading bacteria{Bacillus licheniformis,Bacillus subtilis and Rhodococcus equi)in the composts.In the chicken manure/corn straw composting system and chicken manure/corn straw/mushroom residue composting system,the addition of biochar significantly(p<0.05)increased the total relative abundance of the three E2 degrading bacteria.At the same addition ratio of biochar,the total relative abundance of the three E2 degrading bacteria in treatment with rice husk biochar was higher than the total relative abundance of the three E2 degrading bacteria in treatment with wheat straw biochar.4.The cell proliferation effect of estrogen could be diminished by adding biochar during composting.In the biochar-amended treatments,the proliferation effect value of estrogen on cell in compost samples decreased by 1.23?1.40 during composting,and the reduction was greater than the corresponding control.At the same addition ratio,the treatment adding rice husk biochar with a larger specific surface area and pore volume was more effective in inhibiting the biological activity of estrogen than the treatment adding wheat straw biochar.5.Wheat straw biochar and rice husk biochar can inhibit the proliferative effect of E2 on MCF-7 cells by binding to E2.Moreover,the inhibitory effect on E2 bioactivity by using rice husk biochar with a larger specific surface area and pore volume was stronger than that by using wheat straw biochar at the same biochar application amount. |
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