Estuaries are unique water systems and represent a vital link between land and sea. River transported contaminants, among which trace elements are of major concern, are subjected to a variety of physical, chemical and biogeochemical processes in the estuarine mixing zone.

The Isonzo/Soča River is the main source of freshwater into the Gulf of Trieste (northern Adriatic Sea) and is known as the primary source of Hg due to long-term cinnabar (HgS) extraction from the Idrija mining district (Slovenia). Mercury distribution, cycling and speciation have been intensively studied at the Isonzo/Soča River mouth. Still, little information is currently available regarding other trace elements (As, Co, Cu, Cs, Cr, Fe, Ni, Mn, Pb and Zn). Indeed, this research aims to evaluate trace element occurrence and partitioning behaviour among suspended particulate matter (>0.45 μm), colloidal material (0.45 μm – 10 kDa) and the truly dissolved fraction (<10 kDa) at the mouth of the Isonzo/Soča River.

Generally, trace elements are mainly associated with suspended particulate matter, which represents their main effective vehicle to coastal environments. In addition, dilution effects between riverine and marine particles are responsible for the decrease in particulate trace element concentrations along the water column. Mercury was notably present in winter in the freshwater, as expected under conditions of high river discharge. As opposed to other trace elements, particulate Mn was found to be high in the marine water, particularly in summer when high water temperatures could promote oxidation and precipitation processes. The Isonzo/Soča River mouth is characterised by a strong salinity gradient and geochemical processes appear to affect trace element partitioning behaviour. In this context, Fe, Mn and Cu were found to be mainly associated with the suspended particles and displayed the highest concentration in the colloidal material. Conversely, the truly dissolved fraction prevailed for As and Cs, which are often present in ionic dissolved forms in natural water systems.

河口是独特的水系，代表着陆地和海洋之间的重要纽带。河流运输的污染物（其中微量元素是主要关注的污染物）在河口混合区经历了各种物理，化学和生物地球化学过程。

Isonzo /Soča河是流入的里雅斯特湾（北亚得里亚海）的主要淡水，由于从Idrija矿区（斯洛文尼亚）长期提取朱砂（HgS）而被称为Hg的主要来源。在伊森佐/索恰河河口已对汞的分布，循环和形态进行了深入研究。但是，有关其他痕量元素（As，Co，Cu，Cs，Cr，Fe，Ni，Mn，Pb和Zn）的信息很少。确实，这项研究旨在评估微量元素在悬浮颗粒物（> 0.45μm），胶体材料（0.45μm– 10 kDa）和Isonzo /Soča口中真正溶解的组分（<10 kDa）之间的分配行为。河。

通常，微量元素主要与悬浮颗粒物有关，这代表了它们是沿海环境的主要有效媒介。此外，河流和海洋颗粒之间的稀释作用是导致沿水柱中的痕量微量元素浓度降低的原因。如在高流量河流条件下所预期的那样，冬季淡水中尤其存在汞。与其他微量元素相反，海水中的Mn含量很高，尤其是在夏季，高水温会促进氧化和沉淀过程。Isonzo /Soča河口的特征是盐度梯度大，地球化学过程似乎会影响痕量元素的分配行为。在这种情况下，铁 发现Mn和Cu主要与悬浮颗粒相关，并且在胶体材料中显示出最高浓度。相反，砷和铯的真正溶解部分占优势，它们在自然水系统中通常以离子溶解形式存在。