关键词: 碳同位素, 草原类型, 土壤, 放牧, 植被

Abstract: To understand the environmental status of Jiulong River basin, water samples from the river were collected in July 2017. The pH value of water ranged from 6.7 to 7.9, with an average of 7.2, indicating slightly alkaline. The average value of total dissolved solids (TDS) was 90.9 mg·L^-1, lower than the global mean value of the rivers. The average value of electrical conductivity and dissolved oxygen was 116.5 μS·cm^-1 and 7.5 mg·L^-1, respectively. Ca²⁺ was the dominant cation, accounting for 47.9% of the total cations, whereas K⁺ and Na⁺ together accounted for 29.6% of the total cations. HCO₃^- and SO₄^2- were main anions, which together accounted for 68.6% of the total anions. Those results suggested that the hydrogeochemical type of Jiulong River was HCO₃SO₄Ca. The forward method was used to estimate the contribution of each end member, the results of which showed that carbonate and chemical weathering of silicate contributed to 50.6% and 30.7% of the total cations, respectively. Precipitation had an obvious influence on the water chemistry, presenting a contribution of 12.9% to total cations. The influence of anthropogenic input could not be ignored, especially for the contents of SO₄^2- and NO₃^-. The water chemistry of North River was heavily affected by industrial production due to the industrial and agricultural layout, while that of West River and South River were affected by agricultural activities. Therefore, the discharge of wastewater from industrial production as well as urban sewage should be strictly controlled in North River. In addition to urban sewage, the use of fertilizers also should be strictly controlled in West River and South River.

Key words: carbon isotopic discrimination, vegetation, soil, grassland type, grazing