| With the rapid development of biogas business in our country, the solution to biogas manure after zymosis became the studying focus. It is an effective way to use biogas manure as fertilizer because there is abundant nutritional ingredient in it. But the safety solution received much concerns, such as is it hazardous to soils and plants? Does it can recover heavy metals polluted soils? Does biogas manure as fertilizer pollute soils? All above are items to be researched. In this article the evidence of safe and effective utilization to biogas fertilizer is provided through analysis to ingredient and status of heavy metals in soils and rapes.We compare configuration of heavy metals like Pb, Cu, Zn in basin planted Suzhou rape by BCR series extract method through choosing two kind of soils:common soils and polluted soils. In this case we use two kinds of basic fertilizer and extra fertilizer:one is biogas solid with biogas liquid, the other is pig manure with fertilizer. We compare the heavy metals ingredient in plants, the heavy metals ingredient in soils, different configuration affects in these two situations. Also affections of these two kinds of fertilizers to heavy metals plant effective configuration and heavy metals plant active configuration are discussed. Analyze the affections of these two kinds of fertilizers through calculations of pollution index of soils.We draw the following conclusions through above experiments:(1) The content of alkali-hydrolyzable nitrogen is decreased in common soils when biogas fertilizer is used, effective phosphorus and fast effect kalium are increased. The content of alkali-hydrolyzable nitrogen is decreased in polluted soils when biogas fertilizer is used, effective phosphorus and fast effect kalium are increased dramatically. Gross weights of rapes are raised dramatically when biogas fertilizer is used both to ordinary soils and polluted soils.(2) The content of heavy metal Pb is decreased in common soils when biogas fertilizer is used, also the heavy metals Cu and Zn are increased, and all of them are not exceed the country standard. The contents of heavy metals Pb, Cu and Zn are decreased in contaminated soils when biogas fertilizer is used, also lower than that in case of pig manure and fertilizer. On the whole, the co ntents of heavy metals Pb.Cu and Zn are decreased in polluted soils when biogas fertilizer is used, but the heavy metal Zn is exceeding the third national standards. It is hazardous to use biogas fertilizer in a long run in common soils.(3) For heavy metal contents in different organs of rape is, the content of Pb in rape stems grown in common soils is decreased when biogas fertilizer is used, however, the Cu, Zn content increased significantly, contents of Pb, Cu, Zn in roots and leaves have increased variously, indicating that biogas fertilizer application increased the rapes’ Pb, Cu and Zn contents. For contaminated soils, biogas fertilizer application decreased the rapes’ Pb, Cu and Zn contents in rape roots, stems, leaves, but dramatically improved the content of heavy metal Zn.(4)The contents of effective state heavy metals Pb and Cu decreased, content of effective Cu enhanced significantly in ordinary soils, suggesting that biogas fertilizer application can reduce heavy metals effective Pb, Cu contents, stable contents in soils increased, but at the same time, a substantial increase in effective state Zn of soils. For contaminated soils, effective state Pb decreased after biogas fertilizer application. A slight increase in contents of effective state Cu, effective Zn is basically unchanged. Overall, biogas fertilizer application is to reduce the content of effective state Pb in ordinary soils and contaminated soils.(5) Applying biogas fertilizer reduces contents of active state Pb, Cu, Zn in soils, increases contents of residue state Pb, Cu, Zn; excessive application of biogas fertilizer rises active state Pb, Cu, Zn contents variously.(6)The sequence of heavy metals bioconcentration factors to rapes in common soils when biogas fertilizer is used is Zn>Cu>Pb. But all heavy metals bioconcentration factors are increased when biogas fertilizer is used, and this shows that the heavy metals bioconcentration factors to rapes cannot be decreased. To contaminated soils, the sequence of heavy metals bioconcentration factors is is Zn>Pb>Cu when biogas fertilizer is used, and the heavy metals bioconcentration factors to rapes can be decreased when biogas fertilizer is used in general amount.(7)The pollution level is clear when biogas fertilizer is used supported by the analysis of single soils pollution index and Nemero comprehensive pollution index. This shows that biogas fertilizer cannot pollute soils. The level of soils pollution situation decreased from middle to little in contaminated soils when biogas fertilizer is used, showing that biogas fertilizer is benefit to recover heavy metals pollution in contaminated soils. |
