Lamontagne S, Taylor A R, Herpich D, Hancock G J
CSIRO Land and Water and CSIRO Water for a Healthy Country Flagship, Waite Campus, Waite Road, Urrbrae, SA 5064, Australia.
South Australian Department of Environment, Water and Natural Resources, 11 Helen Street, Mt Gambier, SA 5290, Australia.
J Environ Radioact. 2015 Feb;140:30-41. doi: 10.1016/j.jenvrad.2014.10.013. Epub 2014 Nov 25.
The Tertiary Limestone Aquifer (TLA) is one of the major regional hydrogeological systems of southern Australia. Submarine groundwater discharge (SGD) of freshwater from the TLA occurs through spring creeks, beach springs and diffusively through beach sands, but the magnitude of the total flux is not known. Here, a range of potential environmental tracers (including temperature, salinity, (222)Rn, (223)Ra, (224)Ra, (226)Ra, (228)Ra, and (4)He) were measured in potential sources of SGD and in seawater along a 45 km transect off the coastline to evaluate SGD from the TLA. Whilst most tracers had a distinct signature in the sources of water to the coastline, salinity and the radium quartet had the most distinct SGD signal in seawater. A one-dimensional advection-dispersion model was used to estimate the terrestrial freshwater component of SGD (Qfw) using salinity and the recirculated seawater component (Qrsw) using radium activity in seawater. Qfw was estimated at 1.2-4.6 m(3) s(-1), similar in magnitude to previously measured spring creek discharge (∼3 m(3) s(-1)) for the area. This suggests that other terrestrial groundwater discharge processes (beach springs and diffuse discharge through beach sands) were no more than 50% of spring creek discharge. The largest component of total SGD was Qrsw, estimated at 500-1000 m(3) s(-1) and possibly greater. The potential for wave, storm, or buoyancy-driven porewater displacement from the seafloor could explain the large recirculation flux for this section of the Southern Ocean Continental Shelf.
第三纪石灰岩含水层（TLA）是澳大利亚南部主要的区域水文地质系统之一。TLA的淡水通过泉水溪流、海滩泉以及通过海滩砂层以扩散方式发生海底地下水排放（SGD），但其总通量大小尚不清楚。在此，在SGD的潜在源以及沿离海岸线45公里断面的海水中测量了一系列潜在环境示踪剂（包括温度、盐度、²²²Rn、²²³Ra、²²⁴Ra、²²⁶Ra、²²⁸Ra和⁴He），以评估来自TLA的SGD。虽然大多数示踪剂在流向海岸线的水源中有明显特征，但盐度和镭四重奏在海水中具有最明显的SGD信号。使用一维平流 - 扩散模型，利用盐度估算SGD的陆地淡水成分（Qfw），利用海水中的镭活度估算再循环海水成分（Qrsw）。Qfw估计为1.2 - 4.6立方米/秒，其大小与该区域先前测量的泉水溪流量（约3立方米/秒）相似。这表明其他陆地地下水排放过程（海滩泉和通过海滩砂层的扩散排放）不超过泉水溪流量的50%。总SGD的最大组成部分是Qrsw，估计为500 - 1000立方米/秒，可能更大。海浪、风暴或浮力驱动的海底孔隙水置换的可能性可以解释南大洋大陆架这一部分的大量再循环通量。
