畜禽粪便冻融作用后磷形态分布及其释放特征

畜禽粪便中磷(P)释放特性与其赋存的形态密切相关,冻融循环可通过改变畜禽粪便的理化性质而影响粪便中P形态的分布,进而影响其后续的释放过程.本研究通过一系列室内模拟实验,探究了冻融循环对不同含水率猪粪中P形态分布的影响,以及冻融循环后粪便中P释放特征及其影响因素.结果表明,与未经冻融猪粪相比,冻融后低含水率粪便中Ca-P、Oc-P和Res-P含量分别下降了47.38%、29.76%和55.19%,NH_4Cl-P和Al-P分别增加了36.82%和23.13%;高含水率猪粪中Ca-P、Oc-P和Res-P含量分别减少了49.59%、41.59%和76.96%,NH_4Cl-P、Al-P和Fe-P含量分别增加了37.34%、32.84%和8.96%.经冻融处理的粪便P的释放速率和累积释放量明显大于未冻融处理的粪便.伪一级动力学方程、Elovich方程、权函数方程均能较好的拟合粪便P释放动力学过程,其中Elovich方程的拟合效果最佳,表明粪便中P释放动力学过程是以扩散为主的反应过程.雨水pH值和共存阴离子会影响粪便P的释放,溶液pH越低或NO~-_3/SO■比值越小,越有利用于粪便P的释放.依据统计数据估算,我国冻融区域内畜禽粪便因冻融导致的P最大释放增量总和约为3.20万t·a~(-1),为降低其面源污染风险需要更好的粪便储存处理措施.

Form distribution of Phosphorus and its release after freeze-thaw process of animal manure

The freeze-thaw cycles may influence the manure P distribution via changing the animal manure''s physicochemical properties, and then affect the manure P release which is closely related to the forms of P existence in animal manure. In this study, a series of laboratory simulation experiments were performed to explore the effects of freeze-thaw on P distribution in pig manure with different moisture contents, and to investigate P release process and its influencing factors after freeze-thaw treatment. Compared to the non-freeze-thaw manure, Ca-P, Oc-P and Res-P decreased by 47.38%~49.59%, 29.76%~41.59% and 55.19%~76.96% while NH₄Cl-P and Al-P increased by 36.82%~37.34% and 23.13%~32.84% after freeze-thaw process, respectively. The release rate and accumulated amounts of manure P release after freeze-thaw were significantly higher than those in control. The kinetic models, including pseudo first order equation, Elovich model and power function equation fitted the P release data well, and the Elovich model indicated that the release of manure P mainly involved diffusion. The pH value and co-existing anions in rainfall would affect the manure P release, showing that the lower pH or ratio of NO₃^-/SO₄^2- could accelerate the P release. It was estimated that the total amounts of maximum release increment of manure P caused by freeze-thaw process maybe 32000 t annually in China. Therefore, the better management policy is urgently needed to reduce non-point pollution by animal manure.