海南岛干季化学风化产物输出及其控制因素

根据2014年1月实测的海南岛昌化江径流化学组成,运用物质平衡法和相关分析法估算化学径流组成的来源和控制因素,探讨流域化学风化产物HCO_3~-和溶解性硅(DSi)的输出及生态环境意义。结果表明昌化江流域水体呈中偏弱碱性,化学径流组成阴离子以HCO_3~-为主,阳离子以Ca~(2+)、Na~+为主。其中,77.30%的离子源于流域内硅酸盐岩的化学风化,1.38%的离子来源于碳酸盐岩风化,大气沉降对化学径流的贡献为5.45%,人类活动对干、支流化学径流的贡献分别为15.90%与21.04%,差异显著(P0.01)。地貌条件、岩性及径流深度是影响流域化学径流组成的关键因素。昌化江流域干季输入南海的HCO_3~-和DSi量分别为2.12×10~8 mol、1.38×10~8 mol,是南海海洋生态系统初级生产力的主要物质来源之一,在南海生态系统物质循环预算中不可忽视。

The Output of Chemical Weathering Materials from Hainan Island and Its Controlling Factors in the Dry Season

On the basis of chemical compositions of the Changhuajiang River in Hainan Island investigated in January 2014, sources and controlling factors were studied, the output processes of HCO₃^- and DSi were evaluated, and the eco-environmental mass balance and its correlation were also analyzed. Results show that water from the Changhuajiang River presents gentle to middle alkalinities. The compositions of chemical runoff were dominated by HCO₃^- in anions and Ca²⁺ and Na⁺ in cations. In chemical runoff, 77.30% of ions originated from the silicate chemical weathering, and those from the carbonates chemical weathering accounted for 1.38%. The atmospheric precipitation contributed 5.45%. Additionally, 15.90% and 21.04% of chemical runoff components stemmed from human activities in trunk stream and tributaries, respectively, with a significantly difference (P<0.01). The chemical compositions of the Changhuajiang River are mainly controlled by the terrain, lithology and runoff depth. The Changhuajiang River had transported about 2.12×10⁸mol of HCO₃^- and 1.38×10⁸mol of DSi into the South China Sea during a dry season, which constituted one of the main material sources for primary productivity in marine ecosystems and could not be ignored on matter cycle budget.