Gadolinium-based contrast agents are worldly used for medical magnetic resonance imaging and are an emerging contaminant in natural waters. We investigated the dissolved fraction of Gd in coastal waters from Fortaleza city and observe positive Gd anomalies in the wastewater outfall area as well as in two local river estuaries indicating that the city is a significant source of anthropogenic Gd (Gd_anth) to the ocean. Based on this synoptic study and on the conservative behavior of Gd_anth we trace a highly concentrated sewage-based source which accounts for 2200 pmol kg⁻¹ and to an annual discharge of 25 kg of Gd to the ocean. We also trace minor sources from the two rivers and estimate that the levels of wastewater dilution within freshwater prior to mixing with seawater accounted for 4.8%–14% of the Cocó River discharge and 1.4%–3.9% of the Ceará River discharge at the time of the sampling. Gd is consequently a suitable and promising tracer for water management and forensic purposes in Fortaleza. In order to guide the application of this method to other coastal waters impacted by metropolitan areas in the world, we propose a conceptual model for Gd_anth behavior within salinity gradients and apply it to revisit previous studies.

d基造影剂已广泛用于医学磁共振成像，是天然水中新兴的污染物。我们调查的Gd溶解分数在沿海水域从福塔雷萨市，并在污水排放口区域看到积极的Gd异常以及在表明城市是人为钆（Gd的显著源的两个地方河口_蒽）的海洋。基于此概要研究和Gd _anth的保守行为，我们找到了一个高浓度的污水源，占2200 pmol kg ^-1每年向海洋排放25公斤Gd。我们还追踪了两条河流的次要来源，估计当时与海水混合之前淡水中的废水稀释水平占Cocó河排放量的4.8％–14％和Ceará河排放量的1.4％–3.9％采样。因此，Gd是福塔莱萨（Fortaleza）中用于水管理和取证目的的合适且有前途的示踪剂。为了指导该方法在世界上受大都市区影响的其他沿海水域中的应用，我们提出了盐度梯度内_an蒽蒽磷行为的概念模型，并将其用于重新研究以前的研究。