Study The Changes And Biological Toxicity Of Heavy Metals Species In The Process Of Composting Fermentation Adding The Attapulgite

With the rapid development of scale, specialization, intensive aquaculture in China, the feed additives containing a lot of heavy metals are widely used, which results in the heavy metal elements in livestock and poultry dung exceeds badly. Therefore the long-term application of organic fertilizer in the farming process can not only lead to the accumulation of heavy metals in soil and plants, improper handling can also cause serious environmental problems and endanger human health. So the analysis of dynamic change rule of heavy metals in the chicken manure composting fermentation process, the passivation mechanism of attapulgite, and the biological toxicity of heavy metals in different forms for guiding the utilization of waste in livestock and poultry breeding industry and application in the composting process of the attapulgite has a realistic significance.This study took the chicken manure collected from Xiangxiang breeding farmers’ professional co-operatives in Ganzhou district, Zhangye, Gansu province and the attapulgite provided by the Shuangtai Attapulgite science and technology LTD in Gansu province as the experimental materials. The experiment setting 6 processing, adds different proportions of attapulgite in chicken manure respectively to proceed the aerobic composting. By measuring the amount of Cd, Cr, Cu, Ni, and Zn in different samplings and time points(1, 4, 12, 20, 25, 32 days) in the process of chicken manure composting fermentation, the species distribution obtained by BCR continuous extraction method, the correlation of different heavy metals and seed germination characteristics in different species, to study the changes and biological toxicity of heavy metals species in the process of composting fermentation adding the attapulgite. The results show that:(1) In the process of chicken manure composting fermentation adding the attapulgite, after 32 days the composting was rotten, the concentration of Cd, Cr, Cu, Ni, and Zn were greater than the original samples, and with the increasing percentage of attapulgite adding, it showed relatively concentrated effect more significantly.(2) In the process of chicken manure composting fermentation adding the attapulgite, after 32 days the composting was rotten, the species of heavy metal Cd, Cr, Ni, and Zn in each treatment are showed the trend that from the unstable form to stable form. Then the heavy metal Cu showed the trend from unstable form(exchangeable fraction) and stable form(residual fraction) to other forms. The different proportion plan in every treatment, to the passivation effect of heavy metals in the process of chicken manure composting fermentation, it differs from the heavy metal element. In the treatment of A3(attapulgite: chicken manure for 3:20), the passivation effect of heavy metal Cd and Cr is best; the passivation effect of heavy metal Cu and Ni is best in the treatment of A9(attapulgite: chicken manure for 9:20); the passivation effect of heavy metal Zn is best in the treatment of A6(attapulgite: chicken manure for 6:20).(3) Adding attapulgite has significant influence on the forms of heavy metals in the compost. To the exchangeable fraction of Cd, Cr, Cu, Ni, and Zn, at the same time, their concentration are reducing along with the increasing ratio of attapulgite. To the same attapulgite adding proportion treatments, the concentration reduced with the extension of time. To the reducible fraction of Cd, Cr, Cu, Ni, and Zn, at the same time, their concentration are reducing along with the increasing ratio of attapulgite. To the same attapulgite adding proportion treatments, the concentration of reducible fraction of Cr reduced with the extension of time. The concentration of Cd, Cu, Ni and Zn in reducible fraction increased with the extension of time. To the oxidisable fraction of Cr, Cu, Ni and Zn, at the same time, their concentration are reducing along with the increasing ratio of attapulgite; while the oxidisable fraction Cd is increasing. To the same attapulgite adding proportion treatments, the concentration of Cd, Cr, Cu and Ni in oxidisable fraction increased with the extension of time; while the concentration of Zn in oxidisable fraction reduced with the extension of time. To the Cd, Cr, Ni, and Zn in residual fraction, at the same time, their concentration are reducing along with the increasing ratio of attapulgite; To the same attapulgite adding proportion treatments, the concentration increased with the extension of time. For Cu in residual fraction, at the same time, its concentration increased with the increase of attapulgite adding ratio; To the same attapulgite adding proportion treatments, its concentration increased with the extension of time. It shows that the adding of attapulgite in chicken manure composting fermentation process, has a promoting effect in increasing the stable form and reducing the unstable form of heavy metals, and inhibiting effect in reducing the stable form and increasing the unstable form of heavy metals.(4) In the process of chicken manure composting fermentation adding the attapulgite, to conduct the six treatments, it shows significant correlation between every heavy metals in different forms.(5) For plant seeds, the sort of the correlation of morphological changes of heavy metals: cabbage > wheat > pea > maize; for seed germination indexes, the sort of the correlation of morphological changes of heavy metals: germination index > vigor index > germination percentage > germination potential. For different heavy metals, the order of biological toxicity of heavy metals in the process of chicken manure composting fermentation is Zn > Cd > Cu > Cr > Ni. For different forms of heavy metals, the heavy metals of high effectiveness has certain inhibitory effect on seed germination.