Departamento de Química, Pontifícia Universidade Católica, 22453-900 Rio de Janeiro, RJ, Brazil.
J Environ Radioact. 2010 Jul;101(7):564-70. doi: 10.1016/j.jenvrad.2009.11.001. Epub 2009 Dec 9.
Multitracers were used to study water mixing in the Paraíba do Sul River estuary region in August 2007 (dry season) and March 2008 (rainy season) and to evaluate the reach of the river plume in the direction of the open ocean. Two sampling campaigns were carried out, each in a different season. Based on these results, it was possible to conclude that the multitracers used in this study (salinity, Si, Ba and U, as well as the radium isotopes 223Ra, 224Ra, 226Ra and 228Ra) presented satisfactory results toward defining the plume reach and determining the residence time and water-mixing processes in the estuary. A strong correlation was observed between tracers and the distance to the coast. During the low river water discharge period, the riverine water took about 10 days to reach open ocean waters (salinity approximately 35). During the rainy period this value decreased to 6 days. Based on the radium results, it was possible to calculate diffusion coefficients (K(h)) of 23 km(2) d(-1) and 38 km(2) d(-1) for 224Ra and 223Ra, respectively, during the dry season (winter). Values of 65 km(2) d(-1) and 68 km(2) d(-1) for 223Ra and 224Ra, respectively, were found for the rainy period (summer).
多踪剂被用于研究 2007 年 8 月（旱季）和 2008 年 3 月（雨季）期间 Paraíba do Sul 河口地区的水混合情况，并评估河口羽状流在向开阔海域延伸的程度。进行了两次采样活动，每次都在不同的季节。基于这些结果，可以得出结论，本研究中使用的多踪剂（盐度、硅、钡和铀，以及镭同位素 223Ra、224Ra、226Ra 和 228Ra）在定义羽状流范围和确定河口停留时间和水混合过程方面取得了令人满意的结果。示踪剂与距海岸的距离之间存在很强的相关性。在河流径流量较低的时期，河水大约需要 10 天才能到达开阔海域的海水（盐度约为 35）。在雨季，这一时间减少到 6 天。基于镭的结果，可以计算出在旱季（冬季），224Ra 和 223Ra 的扩散系数（K(h)）分别为 23 和 38km2d-1。对于雨季（夏季），223Ra 和 224Ra 的扩散系数分别为 65 和 68km2d-1。
