黄河流域农业农村氮流时空分布特征及演化规律研究

Spatiotemporal Distribution Characteristics and Evolution Pattern of Nitrogen Flow in Agricultural and Rural Areas of the Yellow River Basin

氮磷等营养元素过剩引发的面源污染问题,是黄河流域水质恶化的重要原因.为应对黄河流域氮素危机,从源头上降低面源污染负荷,本研究基于物质流和空间分析方法,刻画1949-2022年间黄河流域农业农村氮流时空格局演化规律,评估黄河流域面源污染关键氮流和高风险区.结果表明:(1)新中国成立以来,黄河流域的作物收获量整体呈现上升的趋势,2015年之后在氮输入水平持续下降的情况下,仍然能够保持年均2%的增长,黄河流域在氮素利用水平上得到了极大的提升.(2)黄河流域农业农村依然存在严重的氮流失现象,其中存贮和反硝化是氮流失的主要部分,1962年、1992年和2022年这两部分流失量分别占耕地氮输出流的51%、47%和36%.2015开始氮素流失(存储)量逐年下降,2022年比2015年减少了15.55%,但是每年仍有30.12×10^(8)kg氮素流失到大气、水体和土壤中,是当年作物收获氮量的1.64倍,氮素损失率高达62.05%.(3)降雨和地势地形是影响氮径流的决定因素,在高风险区内约有27%~45%的氮剩余流失到附近的地表水中,主要分布在甘肃省的最南部和东南角部分地区、陕西省的最南部和山东省东部地区.研究显示:黄河流域在氮素利用提升和氮污染治理方面取得一定成效,但是仍然存在严重的氮流失现象;需要持续推进化肥减量、粪便还田和农村污水治理,同时需要在高风险区采取构建缓冲带等工程措施,才能实现面源污染等氮危机的有效控制.

Non-point source pollution caused by excessive nitrogen and phosphorus is the main reason for the deterioration of water quality in the Yellow River Basin.In order to solve the nitrogen crisis and reduce the non-point source pollution load at the source,we described the spatial temporal pattern of agricultural and rural nitrogen flow in the Yellow River Basin during 1949-2022 based on the material flow and spatial analysis methods and evaluated the key nitrogen flow and high risk areas of non-point source pollution in the Yellow River Basin.The results showed that:(1)Since the founding of the People′s Republic of China,crop harvests have shown an increasing trend.After 2015,crop harvest still maintained an average annual growth rate of 2%even though nitrogen input continued to decline.Nitrogen use efficiency in the Yellow River Basin has gradually improved.(2)In spite of this,there is severe nitrogen loss in the Yellow River Basin,among which nitrogen storage and denitrification are the main parts.In 1962,1992 and 2022,these two parts accounted for 51%,47%and 36%of the total cultivated land nitrogen output,respectively.The amount of nitrogen loss(storage)began to decrease year by 8 year since 2015 and decreased by 15.55%in 2022 compared with 2015.There was still 30.12×10^(8) kg of nitrogen lost to the atmosphere,water body and soil every year.The amount of nitrogen loss was 1.64 times that of crop harvest,and the loss rate was as high as 62.05%.(3)Rainfall and geography are the decisive factors affecting the nitrogen runoff.About 27%-45%of the residual nitrogen in the high-risk area is lost to the nearby surface water,mainly distributed in the southernmost and southeastern parts of Gansu Province,the southernmost parts of Shaanxi Province and eastern parts of Shandong Province.These areas are the high-risk areas for the non-point source pollution.The study indicates that nitrogen utilization and pollution control in the Yellow River Basin have achieved certain results,but serious nitrogen loss still exists.To achieve effective control of nitrogen crises in the Yellow River Basin,it is necessary to continuously promote the reduction of fertilizer,the return of manure to the field and the treatment of rural sewage,and it is also necessary to take engineering measures such as the construction of buffer zones in high-risk areas.