Characteristic analysis of non-point source pollution in Qinghai province

In China, the agricultural non-point source pollution threatening water environment is a serious problem. The main agricultural non-point source pollution sources include fertilizers, pesticides, straws, mulching films and livestock and poultry mature. The characteristics of the agricultural non-point source pollution in different provinces are different. The paper was to study the characteristic and development tendency of the agricultural non-point source pollution in Qinghai province based on the history data and export coefficient method. Qinghai province is located in the northeast of Qinghai-Tibet Plateau. It has the characteristics of low temperature, large gap in temperature between day and night, less and concentrated rainfall, long sunshine and strong solar radiation. In Qinghai province, many mulching films are used and large numbers of livestock and poultry are dispersedly raised in pastoral and semi-pastoral areas. With the development of agriculture and animal husbandry, the problem of agricultural non-point source pollution has become more obvious. The pollution loads including 4 parameters of chemical oxygen demand (COD), ammonia nitrogen (NH3-N), total nitrogen (TN) and total phosphorus (TP) produced by fertilizers, straws, livestock and poultry had been calculated. Considering the special situation that there were many livestock and poultry by dispersion raising in pastoral and semi-pastoral areas, the calculate methods of the agricultural non-point source pollution of livestock and poultry under different breeding modes were proposed. The pollution contributions and threats of the different pollution sources were revealed and the main prevention measures were given. The results showed that fertilizers and pesticides consumption, crop and straw yield, plastic mulch, livestock and poultry manure had presented an increased tendency in the past 30 years and the crop and straw yield had slowly declined in the past 5 years in Qinghai province. In 2015, the total nitrogen (TN), total phosphorus (TP) pollution loads and ammonia nitrogen (NH3-N) produced by fertilizers were 2 721, 217 and 226 t, which were 2%,15% and 2% higher than that in 2013. When the fertilizer efficiency increased to 40%, the TP load was still larger than that in 2013. The TN and TP loads produced by crop straws are 2 418 and 224 t respectively which were close to the fertilizers in 2015. The COD load was 1889 t. Oil crops produced the largest pollution, beans and tuber crops produced less pollution in Qinghai province. The COD, NH3-N, TN and TP loads produced by livestock and poultry were 1289.1, 8.5, 350.4 and 51.8 thousand ton. Under different breeding modes, the agricultural non-point source pollution load produced by small-scale rear livestock in pens was the maximum, and the NH3-N pollution loads from the large-scale breeding sites and specialized households were large,the NH3-N and TP pollution loads from the free-ranging livestock and poultry were also noticeable. In 2015, 98.8% of COD, 90.2% of NH3-N, 93.8% of TN and 93.9% of TP of agricultural non-point source pollution loads were produced by livestock and poultry manure. Additionally, based on the Environmental State Bulletin of Qinghai province, we obtained that the agriculture non-point pollution was the main source of COD which contributes 66 percentages of the total COD loads in 2015. In view of the main prevention measures, the pollution control of the animal husbandry should be strengthened, an ecosystem circulation mode considering the combination of crop farming and animal husbandry combination should be built. This paper can provide valuable information for the agricultural non-point source pollution control in Qinghai province. © 2019, Editorial Department of the Transactions of the Chinese Society of Agricultural Engineering. All right reserved.