University of California, Santa Cruz, Santa Cruz, California 95064, United States.
Environ Sci Technol. 2011 Nov 15;45(22):9634-40. doi: 10.1021/es2023626. Epub 2011 Oct 12.
We quantify relations between rates of in situ denitrification and saturated infiltration through shallow, sandy soils during managed groundwater recharge. We used thermal methods to determine time series of point-specific flow rates, and chemical and isotopic methods to assess denitrification progress. Zero order denitrification rates between 3 and 300 μmol L(-1) d(-1) were measured during infiltration. Denitrification was not detected at times and locations where the infiltration rate exceeded a threshold of 0.7 ± 0.2 m d(-1). Pore water profiles of oxygen and nitrate concentration indicated a deepening of the redoxocline at high flow rates, which reduced the thickness of the zone favorable for denitrification. Denitrification rates were positively correlated with infiltration rates below the infiltration threshold, suggesting that for a given set of sediment characteristics, there is an optimal infiltration rate for achieving maximum nitrate load reduction and improvements to water supply during managed groundwater recharge. The extent to which results from this study may be extended to other managed and natural hydrologic settings remains to be determined, but the approach taken in this study should be broadly applicable, and provides a quantitative link between shallow hydrologic and biogeochemical processes.
我们量化了在管理地下补给过程中，浅沙土中原位反硝化速率与饱和入渗之间的关系。我们使用热学法来确定特定点流速的时间序列，并用化学和同位素方法来评估反硝化进展。在入渗过程中测量到的零级反硝化速率在 3 到 300 μmol L(-1) d(-1)之间。当入渗速率超过 0.7 ± 0.2 m d(-1)的阈值时，在某些时间和位置未检测到反硝化作用。氧和硝酸盐浓度的孔隙水剖面表明，在高流速下氧化还原锋面加深，这减少了有利于反硝化的区域的厚度。反硝化速率与入渗阈值以下的入渗速率呈正相关，这表明对于给定的一组沉积物特征，存在一个最佳的入渗速率，可以在管理地下补给期间实现最大的硝酸盐负荷减少和供水改善。本研究的结果在多大程度上可以扩展到其他管理和自然水文环境仍有待确定，但本研究中采用的方法应该具有广泛的适用性，并为浅层水文和生物地球化学过程之间建立定量联系。
