Brazilian solar saltworks - ancient uses and future possibilities

Coastal solar saltworks are anthropogenic supratidal habitats exploited for sea salt, which becomes progressively concentrated by evaporation [1]. This multi-pond ecosystem provides a range of environments with different salinity levels, from that of seawater up to sodium chloride saturation and sometimes even beyond [2]. As water evaporates and salinity increases, water is pumped or fed by gravity to the next pond, so that the salinity in each particular pond is kept within narrow limits, essentially constant [3].Brazilian largest saltworks are located in coastlines, more specifically on the shores of estuaries in the northern coast of Rio Grande do Norte State. The establishment of the saltworks in the coastal zones of Rio Grande do Norte occurred with the use of salt plains of rivers. The saltwork ponds located in this stretch of the Brazilian coast account for 95% of sea salt produced in the country and exported, directly influencing the local and regional economies by creating jobs and payment of taxes [4].Considering the form of exploration and harvesting of salt, we can classify the Brazilian solar saltwork ponds into two categories: craft (manual) and mechanized. The craft harvest is small, with an average area of 2-50 ha, divided into 10-20 tanks (evaporators and crystallizers), with manual harvesting of salt and a production of approximately 200-20,000 ton.year-1. The short retention time of the brine in each evaporator prevents the full development of a stable ecosystem [1-3,5]. The result is a salt regarded as second quality by chemical, especially its content of organic and inorganic impurities, and lead tiny crystal and brittle [5,6]. On the other hand, a typical mechanized saltwork pond usually produces over 150,000 ton.year-1, with a production area over 500 ha. The retention time of the brines is longer and the sea water abstracted by the saltwork arises as concentrated brine in the area of crystallization approximately three months later. In this w