2006—2016年间我国畜禽养殖业氮元素入水通量估算

Estimation of nitrogen loss fluxes from livestock farming into aquatic environments in China during 2006—2016

近年来,我国畜禽养殖业发展迅速,同时规模化养殖水平不断提高,大量畜禽养殖产生的不经有效处理的排泄物也给陆地水环境带来了严重负担,为了评估近十年来我国畜禽养殖氮元素排放通量的变化以及养殖模式转变带来的影响,本研究采用污染物排放因子法,估算了在2006—2016年期间,我国规模化和散养的畜禽养殖向陆地水环境中排放的氮元素通量,重点分析了不同地区(华北、华东、中南、西南和西北)和不同畜禽养殖类型(包括羊、猪、肉牛、奶牛、蛋鸡和肉鸡)氮元素入水通量分布特征。计算结果表明,在2006—2016年期间,全国由畜禽养殖排入水体中的氮元素平均通量为4384 Gg,最大和最小值分别为4832 Gg(2006年)和4010 Gg(2008年),中南和华北地区是我国的畜禽养殖氮元素排放的主要地区,华东和西南次之,西北地区最少,2016年华北、中南、华东、西南和西北地区的畜禽养殖氮元素水体流失通量比例分别为27%、26%、20%、17%、10%。2016年由规模化养殖所带来的氮元素入水通量占该年畜禽养殖业氮元素入水总通量的53%。在所有畜禽中,猪和肉牛是我国畜禽养殖氮元素进入水体的主要排放单元,2016年猪和肉牛养殖的氮元素入水通量占总量的68%。同时,不同畜禽养殖类型之间氮元素排放通量差异显著,在所有畜禽中,羊、肉牛和蛋鸡经散养排放的氮元素通量较大,而猪和肉鸡的氮元素排放则主要来源于规模化养殖。

In recent decades,the growing demand for animal meat has led to quick development of livestock farming in China,especially large-scale farming.Excreta from the animals that could not be effectively treated were discharged into aquatic systems directly.To assess the impact of changes in nitrogen fluxes owing to livestock farming and farming patterns in approximately the last decade,we estimated the nitrogen discharges into aquatic systems from livestock farming(including both scatter-feed farming and large-scale farming)from2006to2016.The differences in nitrogen discharges of five typical regions of China(north,east,south central,southwest,and northwest China)and from different animal species(sheep,pig,beef cattle,dairy cattle,laying hens,and broilers)were analyzed.The results showed that the total average nitrogen flux discharged into water from2006to2016was4384Gg,and the highest and lowest values were4832Gg(in2006)and4010Gg(in2008),respectively.South central China and north China were the major regions with the largest nitrogen discharges,followed by east China and southwest China,with the northwest region discharging the least.In2016,the proportions of nitrogen discharges from the livestock farming in north China,south central China,east China,southwest China,and northwest China were27%,26%,20%,17%,and10%,respectively.In2016,the proportion of nitrogen discharges from the large-scale livestock farming was53%of the total.Differences in nitrogen discharges existed among the different animal species.Pig and beef cattle produced the largest nitrogen discharges,occupying68%of the total discharges.Regarding the sheep,laying hens,and beef cattle,their nitrogen discharges from the scatter-feed farming were higher than those from the large-scale farming,whereas for the pigs and broilers,the nitrogen discharges from the large-scale farming were larger.