Microfibers Contents in High Mountain Salty Springs

Microfibers (MF) are unfortunately present in natural systems, and characterization of such pollution must be considered as a global health question. We have studied the content in MF in a high salinity spring in the Pyrenees (NE Iberian Peninsula). The salty composition of the water is sourced from fluids circulating in aquifers with Triassic evaporitic units. The water samples are from the spring and from evaporation ponds where the brine is conducted and where it has been historically evaporated to produce Table Salt. Brines have been carefully sampled and filtered following all the necessary requirements to avoid any potential MF additional contamination. We have done a manual counting of the number of fibers and their colors. Unexpectedly, all the analyzed brines have significant contents in MF (nor other anthropic particles are present), which do not correspond to particles of sediment dragged, but to anthropic contamination. The brine from the spring has an average concentration of 50 MF/L, and in evaporation ponds, it increases to 120 MF/L. The colors of the most common MF are black, blue, and white-transparent. Red and green can also be relevant. The origin of these fibers in non-marine brines is totally anthropic and may have originated from: (i) the contamination of the upper aquifer itself that has incorporated these particles into its circuit and (ii) the aerial fall of particles, which is more evident in the evaporation stages. Results suggest that the presence of MF is ubiquitous and are even found in unexpected geological environments and apparently disconnected from anthropic pollution, such as high mountain salt springs. Such fibers are finally incorporated to commercial Table Salts produced in the local non-marine saltworks.