Longitudinal chemical gradients in estuarine systems

• Autor(a) principal: Soares, José Alexandre Mano
• Data de Publicação: 2019
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/27756
• topic: Marine ecosystem; Estuarine systems; Major elements; Potential toxic elements; Longitudinal and tidal variation

Coastal ecosystems are subject to periodical changes on physico-chemical characteristics that influence the behavior of major, minor and potential toxic elements. Ria de Aveiro lagoon is a shallow and vertically homogenous estuarine system, located on the northwestern part of Portugal’s Atlantic coast (40° 38’N, 8° 45’W). It is composed of various narrow channels which converge onto a single opening to the ocean, resulting in an area with large mud flats and salt marshes. This system is subject to intensive anthropological pressure, which is the main source of the elevated levels of contaminants present within it. The objective of this work was to study the longitudinal and tidal variability of the distribution of major, minor and potential toxic elements in this well-known estuarine system with varying physico-chemical properties. The areas of study were two channels of the Ria de Aveiro estuary. Water column samples were collected from various points along the length of both channels, Mira and Ílhavo, as well as various measurements for water salinity, conductivity, temperature, pH, suspended particulate matter and dissolved oxygen. The partitioning in dissolved and particulate fractions as well, as the dispersion along both channels, were determined for Li, B, Mg, Al, K, Ca, Ti, Mn, Fe, Co, Ni, Cu, Zn, As, Sr, Ba, Hg and U. It was observed that the behavior of elements determined in one channel varied substantially in the other channel, with variations dependent on the physico-chemical parameters, as well as fresh water flow rate and proximity to anthropological pressures.