Nitrogen Flux Analysis and Its Implications for Environmental Management in Huizhou, China

This dissertation, "Nitrogen Flux Analysis and Its Implications for Environmental Management in Huizhou, China" by Xiaobo, Ma, 馬？波, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled Nitrogen Flux Analysis and Its Implications for Environmental Management in Huizhou, China Submitted by Ma Xiaobo for the degree of Master of Philosophy at the University of Hong Kong in November 2004 Nitrogen is one of the most serious water pollutants. Nitrogen pollution causes human health problems, produces eutrophication in waters, and increases water treatment cost, and nitrogen control has therefore become an important aspect of water quality management. The aim of this study was to understand and analyze nitrogen flows in Huizhou, a city in China's Guangdong province suffering from increasingly severe nitrogen water pollution. As 1998 was a normal hydrological year, and because data from this year is readily available, it was selected as the base year for this study. Material accounting, a relatively new method in environmental management and resource conservation, was employed in this study to analyze the nitrogen flux in Huizhou. This method involves looking not only at aspects of the environment such as air, water and soil, but also at the anthroposphere, including the biological and cultural demands which drive human activities. The study employs literature review, data collection, analysis, unification and mass balance calculation/estimation to track nitrogen sources, path ways and destinations, and to investigate linkages and interactions between the environment and anthroposphere. A number of important conclusions were reached: (1) Major nitrogen flows are rivers (16,900 tonne/yr and 43,200 tonne/yr entering and leaving the region respectively), chemical fertilizer (45,700 tonne/yr) and animal feedstuff (12,300 tonne/yr) imports, atmospheric deposition (22,300 tonne/year), animal manure volatilization (9,900 tonne/year) and combustion and other emission processes (12,400 tonne/yr). (2) Nitrogen import and export are mainly controlled by stream flows, because about 57% of total nitrogen generated in Huizhou ended in rivers and was exported. (3) The investigation of sources and pathways of nitrogen exported to rivers showed that about 35% nitrogen is from point sources while 65% is from nonpoint sources. Agriculture was the biggest contributor to rivers. Huizhou was compared with the Danube River Basin and the Changjiang River Basin, and it was found that Huizhou's total nitrogen exports per unit area were markedly higher than those of the Danube River Basin (i.e. 2.35 t/km -yr in 1998 in Huizhou vs. 0.31 2 2 t/km -yr in 1992 and 0.43 t/km -yr in 1988/89 in the Danube River Basin), and comparable to those of the Changjiang River Basin in 1998 (1.58 t/km -yr). The per capita nitrogen contributions were of the same magnitude in all three areas. It seems clear that the export of nitrogen is mainly related to human population, and that the area of the region and its physical situation - hydrological conditions, soil and economic activities, especially agriculture - are also of great importance. (4) Different dietary and consumption behavior produced differences in nitrogen consumption. About 13.6 g nitrogen was consumed per capita per day in Huizhou, higher than the 9.9 g per capita per day in Swiss households but lower than the consumption of Hong Kong households (16-25 g per capita per day). (5) Regional system retention was a