## 4 Discussion
When analyzing the number of elements collected in the dried solids, heterogeneity can be observed in the composition. Significant amounts of Fe (6.6-8.4 ton), Al (2.4-3 ton) and MgCl\({}_{2}\) (1.2-4.0 ton) might be obtained as a dried solid conglomerate together with other elements for the three samples. But a significant amount of Sn (18 tons) would be obtained from dredged sediments, compared to mining residues (0.16-1.4 tons). However, according to the market price, the greatest revenues considering the high pre-concentrated amounts would be obtained as MgCl\({}_{2}\) (between 0.92 and 3.2 million USD). Iron is also a great contributor with revenues between 700 and 885 kUSD for the three samples. A second group of elements would also be potential economic target materials, such as B\({}_{2}\)O\({}_{3}\) (22.84 kUSD), CaCO\({}_{3}\) (130 kUSD from dredged materials), KCl (272.30 kUSD), or Sn (452.28 kUSD). Zinc sulphate is used by agrochemical industries as fertilizer, but also as animal feed and even toothpaste. As significant amounts of Zn sulphate are found in solid samples from Rio Tinto, it might be considered more economically valuable than the individual element. Some other trace elements catalogued as CRMs and technology metals, used as catalyzers, would be concentrated in lesser amounts, but with higher economic impacts in re-exploitation, such as Tm, Mn, Gd, Dy, Ga, Tb, Be, In, etc. (Table 2). The primary impact of the ASEC depuration process is the complete purification of water with a quality exceeding that required for direct or indirect consumption (Table 1) and the avoidance of pollution discharges into the environment. According to [PERSON] et al. (2018), the more polluted the site is, the greater the potential new revenue is. Sites such as the Odiel-Tinto River watershed and other highly metal-polluted bays might be considered ore deposits due to their high concentrations of elements with commercial interests. But also, market values will impact the decision to re-mine elements from solids. A secondary advantage of the reuse of these residues as metal resources is the facility of crush due to the very low degree of humidity and the small particle size. The removal of toxic elements from dredged material decreases the harmful charge of the sediments facilitating easier and cheaper the management, either for landfilling, deep-sea disposal or natural recovery (2018). On the other hand, the application of ASEC as a recovery method provides a monetary and environmental contribution to a circular economy treatment of residues from the Huelva and Ria rivers. The study of [PERSON] et al. (2018) widely reviews the traditional and new operation management of dredged sediments, including the characterization and regulations of European countries and some innovative projects. But it is also aware that management is moving towards a circular economy (sustainable, environmentally friendly, energy and cost-efficient, and low carbon and water footprint) that includes by-products but also impacts the sediment management scheme. Despite the economic profits that might potentially be obtained from mining and dredged material depuration, there are some other ecosystem services that would strongly benefit, for example, water regulation and water supply by providing important volumes for irrigation or industrial processes; waste treatment by removal of contaminants from aquatic ecosystems; increase of raw materials by revalorizing the by-products of dried solids. By applying ASEC to different industries, it would impact other global ecosystem services such as climate regulation (a decrease in GHG emissions for a reduction in the productive cycle of minerals and transport) and gas regulation and even food production by supplying products such as fertilizers and pesticides. According to [42], human well-being is affected by the interaction between social, human, built and natural capital.