Weathering rates as a function of flow through an alpine soil
Weathering rates as a function of flow through an alpine soil
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DOI：
10.1016/s0009-2541(96)00048-4
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发表时间：
1996-10-30
期刊：
影响因子：
3.9
通讯作者：
Drever, JI
中科院分区：
文献类型：
--
作者：
Clow, DW;Drever, JI
在1990-1994年的夏季，在科罗拉多落基山脉的一个39米（2）高山集水区测量了水流对土壤溶质释放速率的影响。通过土壤的流量变化，增加自然降雨与去离子灌溉水。在5个田间季节中，日水分输入平均为96 - 216 1天（-1），平均流量（输入减去蒸散）为35 - 175 1天（-1）。体积加权平均浓度的基础阳离子和二氧化硅下降只有适度的水输入量的增加。降水中溶质的输入通量在每个研究季节都是相似的，但盐基阳离子和表面流出的二氧化硅的输出通量随着季节平均水输入速率的增加而显著增加。增加似乎在很大程度上是由于高流量条件下，从土壤基质中的溶质运输增强。在高流量，物理冲洗微孔大概发生在更大的程度上比在低流量期间，因为更大的土壤湿度和更高的水文水头。增加冲洗也会导致溶质的扩散速度增加，从矿物表面的微裂纹和收缩的孔隙空间，以响应这些区域和土壤基质中相邻区域之间的浓度梯度增加。在高流量期间发生的冲刷增加的另一个后果是，整个土壤基质中的浓度往往较低，这可能会增加一些硅酸盐矿物（如微斜长石）的化学风化速率，这些矿物相对接近饱和。在高流量条件下的Si浓度降低，似乎促进溶解的无定形硅铝酸盐或从矿物表面的Si解吸，缓冲土壤溶液中的Si浓度。因此，物理运输的溶质和随后的化学效应似乎是负责的风化产物和水输入速率之间的通量观察到的正相关。
The effect of flow on release rates of solutes from soil in a 39-m(2) alpine catchment in the Colorado Rockies was measured during the summers of 1990-1994. Flow rates through the soil were varied by augmenting natural rainfall with deionized irrigation water. Daily water inputs averaged between 96 and 216 1 day(-1) during the five field seasons, and mean discharge (inputs minus evapotranspiration) varied from 35 to 175 1 day(-1). Volume-weighted mean concentrations of base cations and silica decreased only moderately in response to the increased water inputs. Input fluxes of solutes in precipitation were similar in each of the study seasons, but output fluxes of base cations and silica in surface outflow increased substantially in conjunction with the average water input rate for the season.Weathering rates calculated from the chemical fluxes increased substantially in response to increases in water input rates. The increases appear to be largely attributable to enhanced transport of solutes from the soil matrix under high flow conditions. At high flow, physical flushing of micropores presumably occurs to a greater extent than during low-flow periods because of greater soil wetness and higher hydrologic head. Increased flushing would also cause an increased rate of diffusion of solutes, from microcracks in mineral surfaces and constricted pore spaces in response to an increased concentration gradient between those regions and adjacent areas in the soil matrix. Another consequence of the increased flushing that occurs during periods of high flow is that concentrations throughout the soil matrix tend to be lower, which might increase chemical weathering rates of some silicate minerals such as microcline, which are relatively close to saturation. Decreased Si concentrations under high-flow conditions appear to promote dissolution of amorphous aluminosilicates or desorption of Si from mineral surfaces, buffering Si concentrations in the soil solutions. Thus, both physical transport of solutes and subsequent chemical effects appear to be responsible for the positive relation observed between fluxes of weathering products and water input rates.