Multi-element signatures in solid and solution phases in a tropical mixing zone: A case study in the Cai River estuary, Vietnam

Anthropocentric perspective on climatic variability, potentially toxic elements, and health risk assessment in the Mansehra district: a case study of the Kunhar River, Pakistan

“…Using an HTC-2 hygrometer, the temperature and relative humidity were measured instantly. The pH and EC of Kunhar River water samples were measured using a pH meter (HI 2211, Hanna, USA) (Kandhro et al 2016) with a portable electrical conductivity tester (TET) (HI-98302, Hanna, USA) (Koukina et al 2021). The total dissolved solids (TDS), turbidity, total suspended solids (TSS), total hardness (TH), biological oxygen demand (BOD), phosphate, fluoride, nitrate, sulfate, and chloride ratio in the river samples were determined and tested according to a standard procedure (Gorde & Jadhav 2013).…”

Spatial and temporal variations of geochemical processes and toxicity of water, sediments, and suspended solids in Sibuti River Estuary, NW Borneo

“…The key drivers of such changes in a river’s ecosystem are always the inputs by the headwaters, in its catchment area or floodplains. On the other hand, estuaries are the transitional zone of the river where the mixing of two water masses (seawater and river water) of distinct physico-chemical properties takes place while working as a geochemical filter for contaminants carried in form of sediment (suspended and bed load) and dissolved load (Guinoiseau et al 2016 ; Koukina et al 2021 ). The origin of these contaminants generally attributes to anthropogenic sources such as agriculture and urbanized run-off (Somura et al 2012 ; Priya et al 2014 ; Frazar et al 2019 ; Asha et al 2020 ; Huang et al 2020 ) and natural sources such as weathering of rocks in the basinal region (Pavoni et al 2021 ), which contributes the majority of the solutes and solid matters to the river system (Martin and Whitfield 1983 ; Lintern et al 2018 ).…”

“…The study of sediment composition in estuaries helps to reflect the geochemical nature of the river basin and helps to elucidate the overall character of the material transported by rivers from adjacent land areas, derived from shoreline erosion, carried by marine currents from external sources, and produced in situ by organisms and contribution by human activities (Prabakaran et al 2020 ). On the other hand, rivers around the world carry 13.5 × 10 9 tons of suspended solids towards the sea (Eisma 1988 ), and estuaries work as geochemical and biochemical reactors that modify the river fluxes and composition of terrestrial inputs within its influencing territory (Sholkovitz and Szymczak 2000 ; Koukina et al 2021 ). Such processes are mainly controlled by physical and chemical factors such as hydrodynamic mixing due to volatile tidal gradient (Salas-Monreal and Valle-Levinson 2008 ; Mathew and Winterwerp 2020 ) whereas fluvial effect and geomorphological processes coupled with rock-water interaction contribute the majority of weathered inputs and are highly dependent on seasonal rainfall (Ralston et al 2013 ; Brantley et al 2017 ; Mathew & Winterwerp 2020 ).…”

“…The distribution of trace metals and nutrients in solid, liquid, and colloidal or particulate phases plays a major role in determining the water quality and health of estuarine and coastal ecosystems (Tomczak et al 2019 ; Iglesias et al 2020 ; Koukina et al 2021 ). As a result, these inputs work as a foundation for the survival of aquatic life while assisting in the primary production of nutrients such as N and P and the structural development of organisms; they also can aggravate adverse impacts on coastal and estuarine biota along with human health when present in overwhelming quantity (Jezierska et al 2009 ; Tchounwou et al 2012 ; Reiman et al 2018 ).…”

“…As a result, these inputs work as a foundation for the survival of aquatic life while assisting in the primary production of nutrients such as N and P and the structural development of organisms; they also can aggravate adverse impacts on coastal and estuarine biota along with human health when present in overwhelming quantity (Jezierska et al 2009 ; Tchounwou et al 2012 ; Reiman et al 2018 ). In the case of tropical river basins, intense rainfall coupled with warm and humid climate leads to intense weathering and transportation of terrestrial materials towards coastal regions in a shorter period compared to temperate climates (Koukina et al 2021 ). Therefore, the study of estuaries of such rivers are ideal to study the geochemistry of water, sediment, and suspended solids (SS).…”