Determination of fluoride physicochemical profile and topographic characteristics from water sources in four Huila municipalities

Objectives: To determine the topographic characteristics and physicochemical profile of fluoride in four-Huila municipalities water sources: Pitalito, Altamira, El-Agrado and Rivera, with high prevalence of fluorosis in 5-year (98%) and 12-year olds (94%).
Methods: Initially, the main tributary subbasins of each municipality water distribution system were identified. In each municipality samples of soil, rock, active sediment and water were taken from four locations: high-, middle-, low-subbasin, and the sanitation-office urban net checkpoint. Solid samples were dried and analyzed by X-ray diffractogram and water by fluoride-specific electrode.
Results: Seventy-six samples were obtained (Pitalito: n=22, Altamira: n=20, El-Agrado: n=19, Rivera: n=15). Main topographic characteristics were: Pitalito’s Guachicos subbasin-river showed many crops/grazing areas close to the riverbed. Altamira showed an evident environmental impact in El Cedro high-creek basin due to the agricultural limit widespread. El-Agrado´s basin, in spite of very steep slope, showed moderate-high coffee-growing intervention in the high part affecting the whole hydric system river down. Despite Rivera’s basin overall good preservation, agricultural limit advances significantly with high pesticides use near the riverbed. Fluoride concentrations are shown in the table. Pitalito’s El-Cedro creek increased fluoride concentration up to 50%. Altamira-riverbed fluoride levels remained constant, increasing slightly from the water intake (0.247 ppm) to tap water (0.271 ppm). El-Agrado’s El-Pescado creek had the highest fluoride concentration (0.925 ppm), continuing high when united to La-Mosca creek (0.907 ppm) in the riverbed middle. At Rivera´s riverbed top, fluoride concentration was 0.714 ppm, increasing slightly at middle riverbed (0.745 ppm) and water intake (0.739 ppm). Sedimentary materials were found: lapilli tuffs, lavas and agglomerates, granite, andesite and dacite materials, migmatites, granulites, gneisses, granites, quartzites and marbles.
Conclusions: Different groups of fluoride-containing minerals as secondary element and agrochemicals could be responsible for the high-fluoride water content and high-fluorosis prevalence in these municipalities.