Abstract
AimIn this research, we aimed to model limnological parameters in the Salina Unidos (Macau-Brazil) using GIS technology. We hypothesized that in solar saltworks, the geochemical characteristics of the brines (i.e. the strong solution of salts) vary considerably through the salt ponds circuit, in which drastic changes can damage the entire salt production.MethodsGeochemical parameters were monitored in seven sampling points distributed along the salt ponds circuit, during a complete cycle of salt production, i.e., from January to December 2007. The open source software Spring 5.1.6 was used to build, store, analyze and model the spatial distribution of the parameters.ResultsWe identified a spatial gradient of the salinity and temperature, with values increasing from evaporation ponds to concentration ponds, showing a relationship with the salt production. The parameters, depth, dissolved oxygen concentrations and total dissolved reactive phosphorus showed a decrease from the evaporation ponds towards the concentration ponds. Among the dissolved inorganic nitrogen forms analyzed (NH3-, NO2- and NO3-), nitrate was the predominant, namely in the concentration ponds, where it reached the highest concentrations. The concentration of chlorophyll awas higher in the initial and intermediate evaporation ponds, showing a distinct dynamics of in relation to other environmental variables.ConclusionsThe increased concentration of the analyzed limnological parameters, from the evaporation ponds towards the concentration ponds, evidenced a heterogeneous distribution varying significantly with season. The geochemical spatialization of brine, as illustrated by GIS approach, is very important for the conservation of these environments because this spatial heterogeneity can provide a high diversity of habitat types. This spatial analysis proved to be a practical tool for an adequate management of solar saltworks considering the environmental (ecosystem) and the socio-economic aspects.
Highlights
Multi-pond solar saltworks provide a wide range of environments characterized by an increasing salinity, along the salt production circuit, that varies from seawater levels up to sodium chloride saturation and sometimes even above saturation (Rodríguez-Valera, 1988; Javor, 1989)
In accordance with the brine management, salinity showed a significant (F6,77= 246.17, p 0.05)
The salinity started with 32 gL–1 on initial evaporation sector, and gradually increased throughout the salt production circuit, reaching 269 gL–1 on the final concentration sector (Figures 2A, 3A)
Summary
Multi-pond solar saltworks provide a wide range of environments characterized by an increasing salinity, along the salt production circuit, that varies from seawater levels up to sodium chloride saturation and sometimes even above saturation (Rodríguez-Valera, 1988; Javor, 1989). Salters are a specific type of coastal wetlands characterized by the permanent flooding of 90% of the area with brine for salt production. This integrated coastal ecosystem is specially designed according characteristics of the area (e.g. geomorphology, climate, tides flux); they are unique in terms of their architecture, and by combining their production process with the conservation of the coastal biodiversity (e.g. phyto and zooplankton, fishes, birds) (Korovessis & Lekkas, 2009; López et al, 2010). Worldwide saltworks can vary greatly in terms of the concentrations of inorganic nutrients and of the brines (the solution of salts). These variations might depend on geographical location, season and management practices, among other factors (Oren, 2000). Nutrients (nitrogen and/or phosphorus) are sometimes added as fertilizers to enhance the development of benthic microbial mats or planktonic communities of light‐absorbing microorganisms (Oren, 2009)
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