| Agricultural source(covering livestock breeding,crop farming and aquaculture industry)is included in the category of total emission reduction for major pollutant in“12th five-year”plan.In the agricultural emission reduction project,the emission base of livestock and poultry industry wastewater pollution is large,and the proportion is high.Among the main pollutants of agriculture,COD,TN and TP emissions,COD emissions from livestock and poultry sources accounted for 96%,TN and TP emissions accounted for38%and 57%.In many parts of our country,pig industry has long been the first place in livestock breeding.In Hunan,the annual output value of pig from 2001 to 2015 accounts for an average of over 20%of total agricultural output.In the Dongting Lake Eco-economic Zone(DLEZ),the pig is the main economic income source of local farmers,but with the expansion of the scale of farming,the industry of environmental problem is increasingly serious,has become the most major pollution sources.Now,The research on the contamination of the breeding industry of DLEZ is mainly focused on the cause analysis,the research method is more macro,the research degree is low.In this paper,the DLEZ in Hunan Province was selected as the study area.The inter-annual dynamics and spatial patterns of pollutants(COD,TN and TP)from the pig husbandry were studied.To find out the cause of the pollution,the methods of pollutant discharge coefficient and ArcGIS spatio-temporal analysis were applied.The primary data of the pig population were collected from the local Agricultural Statistics Yearbooks from2000 to 2014.And analyzes the influence factors of pig industry pollutant emissions and pollution prevention.So as to comprehensive development of the industry pollution and the region of Dongting lake water quality protection to provide important basis.The main conclusions are as follows:(1)Thepigpopulationandpollutantloadsgenerallyshowedan increase-decrease-increase trend during the last 15 years and peaked in 2007.The pig population increased from 14.7 million in 2000 to 20.1 million in 2014.The total loads of COD,TN,and TP increased from 112.99×10~4,11.75×10~4,and 1.10×10~4 t/a in 2000 to154.56×10~4,16.07×10~4,and 1.51×10~4 t/a in 2014.(2)In terms of spatial pattern,the areas with the highest pollutant loads distributed in Changde in the western DLEZ and Miluo and Wangcheng in the southeastern DLEZ.Furthermore,these areas expanded year by year.The COD reach level 3 and above pollution area increased from 3 to 6,TN reach level 4 and above pollution area increased from 11 to 13,TP reach level 4 and above pollution area increased from 7 to 11.(3)The main factors affecting the industry pollution emissions are:the technology in the process of breeding,feed ratio and feed system,aquaculture waste treatment and resource utilization.The control methods are mainly the following aspects:design of pig farm,scientific ratio of feed,resource utilization of pig husbandry residues,pig wastewater treatment and resource utilization,ecological protective measures.(4)The DLEZ in pig environmental priority area should choose of Changde,Miluo and Wangcheng.The best way to ensure sustainable development of pig industry and solve pig industry pollution problems are:reasonable site selection of pig farms,scientific feed system,adhere to the planting and raising,developing ecological circular agriculture,the multi-stage wetland system of wetland system with straw-Myriophyllum elatinoides algae. |
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