Anthropic processes degrade quality of estuarine environments, resulting in a worrying form of water pollution. The objective of the study was to describe and discuss interannual and seasonal changes of water quality based on indicators monitored in Goiana River estuary, as well as identifying the main drivers of such changes. We considered three estuarine areas or habitats (upper estuary, middle estuary and lower estuary), and two seasons (dry and rainy) for anchoring sample design. The information collected for surface and bottom water include water temperature (• C), salinity, dissolved oxygen (mg L −1), saturation (%) and Secchi depth (cm) (n = 864). The monthly total rainfall (mm) was compiled from public database. Multivariate analyses highlight inter dependency among these parameters. Water quality was reduced in dry periods (including episodes of hypoxia), but generally increased toward the mouth of estuary. Rainfall is the most important factor in the renewal and maintenance waters of small tropical estuaries. Regions most sensitive to climate change where water resources are depleted and/or compromised should pay even more attention to upcoming changes in rainfall (seasonal) and climatic patterns in addition to better water management practices.
The effect of different additives on the cloud point (CP) of an octylphenol ethoxylate (OPEO30) aqueous solution was investigated. The CP of OPEO30 is higher than 100°C due to its approximately 30 oxyethylene units per molecule, which limits its use in cloud point extraction (CPE) procedures at room temperature. However, the presence of additives can promote a decrease in CP, allowing its use in CPE. Halide presence decreased the CP of OPEO30 in the following order F -[ Cl -[ Br -. It was also observed that the addition of divalent anions resulted in a more pronounced salting-out effect than monovalent anions. Blends of OPEO30 and its counterpart with 7.5 units of ethylene oxide (OPEO7.5) were also investigated, and it was verified that the CP of OPEO30 decreased linearly with increasing OPEO7.5 concentration, showing that mixing surfactants is a strategy to be explored. In the presence of small amounts of alcohols that are partially soluble in aqueous solution, such as isobutanol and pentanol, cloudiness was observed at temperatures below the CP of pure OPEO30 solution.
Waters entering the small estuaries of the Brazilian north-east originate from drainage basins that cross semi-arid and tropical rainforest areas at various levels of use and conservation. Such rivers are often under heavy demand for water supply and other services, such as effluent dilution. The present study examines four consecutive years (2006-2009) of water quality-monitoring data divided by season (rainy and dry) just before the Goiana River enters its estuary. The environmental variables are largely controlled by rainfall patterns. The water temperatures are consistently above 25 °C, which impairs dissolved oxygen levels (3.1 to 6.7 mg L) and may suggest eutrophication. By contrast, biochemical oxygen demand, percentage O saturation and total phosphorous (which are eutrophication indicators) do not show non-compliant levels, according to local legislation. Although the monitoring stations surround a municipal centre, the estuary is downstream from this area, the main uses of which are artisanal fisheries, nature conservation, leisure and aquaculture. Therefore, continuous monitoring and long-term analysis of the resulting water quality are important.
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