黄河流域化学风化作用与大气CO_2的消耗

CHEMICAL WEATHERING PROCESSES AND ATMOSPHERIC CO_2 CONSUMPTION IN THE YELLOW RIVER DRAINAGE BASIN

通过对黄河水化学的相关分析和因子分析,得到大气CO2、碳酸盐、蒸发盐、硅酸盐风化过程对黄河水溶解质的贡献率分别为:9 78%、37 3%、37 6%和7 54%,表明黄河流域碳酸盐和蒸发盐的溶解是最主要的风化过程,对河水化学的总贡献率达到74 9%。黄河水中约90%的HCO3-来自碳酸盐风化过程,10%来自硅酸盐化学风化。由此对流域现代风化率和大气CO2消耗量进行了估算,得到黄河流域化学风化率和CO2消耗率分别为33 6t/km2·a和143 85×103mol/km2·a,其中碳酸盐和硅酸盐风化过程消耗的CO2分别为117 70×103和26 15×103mol/km2,黄河流域每年消耗的大气CO2总量达到108×109mol。与世界流域盆地年均消耗CO2量相比,虽然黄河流域的化学风化率属世界平均水平,但黄河流域风化作用的CO2消耗率却比世界平均值低约41%,这是因为黄河流域是世界上蒸发盐含量最高的地区之一,流域蒸发盐、碳酸盐风化作用占主导地位,而硅酸盐风化作用很微弱。

According to the correlation and principal composition analysis of the Yellow River water, the water chemistry is mainly controlled by the weathering processes of carbonates and evaporites,which are responsible for about 75% of total ion equivalent concentration. Around 10% of the dissolved load is imported in the form of HCO3- from the atmospheric CO2, while the silicate weathering input may have a contribution of only 754% of the total dissolved flux into the Yellow River water. The results suggest that no pronounced effect of silicate weathering on the Yellow River chemistry is found. The analysis of the composition loadings shows that 90% of HCO3- concentration originates from the carbonate weathering reactions, while only 10% is derived from silicate dissolution. The weathering rate is estimated at 336 t/km2.a deduced from HCO3- concentration from atmospheric CO2, close to the world average. The CO2 consumption rate by rock weathering amounts to 143.85×103 mol/km2 for the Yellow River basin annually, 40% lower than the world average level. The quantity of CO2 consumption sink is equal to 108×109 mol yearly, 818% from carbonate weathering and 182% from silicate weathering Compared with other world watersheds, the higher evaporite content and infirm silicate dissolution may result in the lower CO2 consumption rate and wastage budget in the Yellow River drainage basin.