Groundwater inflow to a shallow, poorly-mixed wetland estimated from a mass balance of radon
Groundwater inflow to a shallow, poorly-mixed wetland estimated from a mass balance of radon
复制标题
DOI：
10.1016/j.jhydrol.2008.03.016
复制
发表时间：
2008-06
影响因子：
6.4
通讯作者：
P. Cook;C. Wood;T. White;C. Simmons;T. Fass;P. Brunner
中科院分区：
文献类型：
--
作者：
P. Cook;C. Wood;T. White;C. Simmons;T. Fass;P. Brunner
2006年5月至10月期间，在澳大利亚南部的一个浅水湿地内测量了三次氡活动。地表水内的测量活动在每种情况下都显示出类似的空间变异模式，这表明它与地下水流入和混合过程的位置有关。平均地下水流入率已估计从平均氡活性使用质量平衡方法。氡收支的组成部分是：（i）地下水流入的贡献，（ii）湿地底部沉积物的扩散通量，（iii）气体交换造成的损失，（iv）放射性衰变造成的损失，（v）地下水或地表水流出造成的损失。完成水平衡还需要地表水流入率、湿地上的直接降水和蒸发率。氡扩散通量已估计从测量的沉积物内的氡生产和扩散运输模型，校准测量的氡活性在密封的房间，可以接收氡只从扩散和失去它只有通过放射性衰变。由于气体交换的氡损失是从SF6的损失率推断出来的，在其注入到湿地的孤立地区，而放射性衰变率是已知的。地下水入流中的氡活度是从湿地周围的采样测压计测量的。稳态和瞬态质量平衡方法产生类似的结果，地下水流入速率在12和18立方米/天之间变化。估计的地下水流入率是最敏感的地下水流入的氡活性，气体交换速度，地表水面积和准确性，在湿地中的平均氡活性可以测量。重要的是，它对地表水流入速率相对不敏感，而地表水流入速率知之甚少。
Radon activity within a shallow wetland in southern Australia has been measured on three occasions between May and October 2006. Measured activities within the surface water display a similar pattern of spatial variability on each occasion, suggesting that it is related to the locations of groundwater inflow and mixing processes. The mean groundwater inflow rate has been estimated from the mean radon activity using a mass balance approach. The components of the radon budget are (i) contribution from groundwater inflow, (ii) diffusive flux from wetland bottom sediments (iii) loss due to gas exchange, (iv) loss due to radioactive decay, (v) loss due to groundwater or surface water outflow. Also required to complete the water balance are the surface water inflow rate, direct precipitation on the wetland, and evaporation rate. The radon diffusive flux has been estimated from measurements of radon production within the sediments and a diffusive transport model, calibrated by measurements of radon activity in sealed chambers that can receive radon only from diffusion and lose it only by radioactive decay. Radon loss due to gas exchange is inferred from the loss rate of SF6, following its injection into isolated areas of the wetland, while the rate of radioactive decay is known. The radon activity in groundwater inflow is measured from sampling piezometers surrounding the wetland. Steady state and transient mass balance approaches yield similar results, with groundwater inflow rates varying between 12 and 18m3/day. Estimated groundwater inflow rates are most sensitive to the radon activity of groundwater inflow, the gas exchange velocity, surface water area and the accuracy with which the mean radon activity in the wetland can be measured. Importantly, it is relatively insensitive to the surface water inflow rate, which is poorly known.