New research reveals the mechanism of nitrogen pollution in water sources

Recently, the relevant research results of the ecological restoration research team of the Institute of Subtropical Forestry of the Chinese Academy of Forestry were published in the international journals Journal of Forestry Research and Ecological Indicators, which initially revealed the mechanism of nitrogen pollution in water sources.

Water sources under the influence of human activities. Photo courtesy of interviewee

At present, the global nitrogen fertilizer use reaches 120 million tons, which is twice the Earth’s limit threshold, but only 40% of the nitrogen is absorbed by crops, and more than 50% of the nitrogen fertilizer enters the environment. About 60% of China’s rivers and lakes are polluted to varying degrees, of which 50% are caused by non-point source pollution, while nitrogen pollution contributes 81% to water pollution.

The team focused on the study of surface runoff migration pathway of Taihu Lake Basin, carried out continuous positioning observation in the field, and preliminarily revealed the mechanism of nitrogen pollution: high-intensity rainfall can migrate nitrogen in leaves and soil with surface runoff through leaching and washing, which is the main driving force for nitrogen loss.

Water sources under the action of forest wetlands. Photo courtesy of interviewee

Therefore, the rainy season (June-September) with abundant rainfall is the main period of nitrogen loss, accounting for 85.9–95.9% of the annual nitrogen loss. From the perspective of spatial dimension, the spatial level of water sources gradually increased from high to low, and the nitrogen loss intensity gradually increased. In the process of runoff migration, anthropogenic activities such as domestic sewage discharge and white tea cultivation can increase nitrogen pollution in runoff trenches, while the construction of forest wetlands can effectively reduce the concentration of nitrogen pollutants in water bodies. The study also found that through stand optimization, changing the structure of the bamboo forest and mixing evergreen trees and legumes in the pure forest of the bamboo can effectively control nitrogen loss and reduce nitrogen leakage from water sources by 38.2%.

The research results not only enrich and expand the theoretical connotation of soil physics, hydrology and other related disciplines, but also clarify the key factors of nitrogen pollution in water under the cover of high-intensity economic forests, which is conducive to establishing a sustainable vegetation management mode in this type of water source area and promoting the control of water source ground source pollution.

Wang Rongjia, a doctoral student graduated from the Yalin Institute of the Chinese Academy of Forestry, is the first author of the paper, and Zhang Jianfeng, a researcher at the Yalin Institute of the Chinese Academy of Forestry, is the corresponding author. (Source: China Science News, Li Chen, Yang Yingying)

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