| The total amount of livestock feces in China will increase to 298 million tons by 2020,causing serious environmental pollution problems.Aerobic composting is one of the most economical and effective ways to treat feces.But due to the addition of trace elements in the feed,the compost products will cause heavy metal pollution in the soil after agricultural use.And the composting process will release some harmful genus to the atmosp Here to form bioaerosols,which will cause hidden dangers to the health of surrounding populations.Therefore,it is of great practical significance to effectively use fecal compost to improve the soil,control the heavy metal pollution of compost products,and reduce the release of harmful biological aerosols during the composting process.Swine,cow and chicken manure were used as raw materials for one month of composting and three months of mature,and the changing laws of fecal p Hysiochemical properties during the process were studied.The results showed that the moisture content,volatile solids,total p Hosp Horus,and total potassium content of three types of livestock showed a downward trend during the composting process.The proportion of water-soluble carbon in total carbon increased by about 15% after composting for 30 days.Similarly,the effective phosphorous content of swine cow,and chicken manure increased by 54.9%,25.7%,and 30.0%,respectively.After composting,and the available potassium content increased.74.1%,32.7% and 86.4%.These results show that the total amount of nutrients is reduced during the composting process,but the proportion of active ingredients increased.The total copper and total zinc content of cow dung and chicken dung are close to the limits set by the agricultural mud standard.The total copper and total zinc content of pig dung are beyond the standard value and are not suitable for use as agricultural organic fertilizer.After composting,the three types of feces and their composting products were mixed with the soil.The difference between the application of excrement,compost products,and the original soil was compared after 120 days.Compared with the direct return of feces,the total carbon,total p Hosp Horus,and total potassium content of the compost products were lower,but the contents of water-soluble carbon,available p Hosp Horus,and available potassium were higher.Swine,cow and chicken manure and their compost products will cause the total copper content in the soil to exceed the relevant standard.The correlation analysis showed that the water-soluble carbon content of fertilizer had a significant effect on total soil carbon content;the heavy metal content in soil was not only affected by the corresponding heavy metal content in the fertilizer,but also closely related to the humidity and organic matter content of the fertilizer.Aerosols were collected on the second,10 th,30th,and 60 th days of three kinds of fecal composting,and the changes of bacterial community structure in the aerosol were analyzed.Bacillus and Lactococcus are the dominant genus in all three aerosols during composting.Compared with the second day,the proportions of dangerous bacteria genera in the swine,cow and chicken manure aerosols of the 60 th day were reduced by 5.92%,55.29% and 10.68%,respectively.The gene function prediction results showed that the percentages of genes related to bacterial infectious diseases was highest in pig manure aerosol(2.24%),followed by cow manure aerosol(1.88%),and chicken manure aerosol(1.68%).RDA showed that water,VS/Ash and ORP were the most important factors affecting the succession of aerosol bacterial communities.These conclusions indicated that the composting process does bring health risks to the people working around. |
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