The different behaviour observed for lignins, carbohydrates and fatty acids highlights a potential chemical segregation based on their hydrophobicity. These findings fit with the mechanism of colloidal and particulate destabilization in the soil macroporosity. These analyses highlighted a modification of the DOM composition in soil solution controlled by the water-table dynamic and pre-event hydrological conditions. The molecular composition of the DOM was analysed by thermally assisted hydrolysis and methylation (THM) with tetramethylammonium hydroxide (TMAH) coupled to a gas chromatograph and a quadrupole mass spectrometer. To investigate these assumptions, soil solutions in the macropores, surface runoff and stream outlet were sampled at high frequency during three storm events in the Kervidy–Naizin catchment, part of the French critical zone observatory AgrHyS. Recent molecular investigations have challenged this view and hypothesized (i) a contribution of an in-stream partition of organic matter (OM) between eroded particles and the dissolved fraction and (ii) the modification of the composition of soil DOM during storm events. The latter was attributed to changing water pathways inducing the mobilization of DOM from the surface soil horizons. Storm events are responsible for more than 60 % of the export of dissolved organic matter (DOM) from headwater catchments due to an increase in both the discharge and concentration. This study has shown that NaCl, in combination with high-activity clay particles in solution, may effectively reduce turbidity to levels suitable for SODIS treatment, thereby expanding the number of people who can utilize the technology effectively.Ībstract. Results show that unlike kaolinite and illite, pure bentonite solutions were shown to be very responsive to NaCl and produced supernatants with as low as 4 NTU (98% particle removal efficiency). Supernatants were tested for sodium concentration for comparison against health and taste thresholds.
Three representative clays found in tropical soils (kaolinite, illite and bentonite) were tested at three levels of turbidity (50, 100 and 200 NTU) for their flocculating behavior with multiple NaCl concentrations to find the optimum. This study investigates the use of common table salt (NaCl) to reduce the turbidity of water containing suspended colloidal clay particles for use in the SODIS method. However, the SODIS method is limited to waters of low turbidity (<30 NTU). Solar water disinfection (SODIS) has proven to be effective at reducing diarrheal incidence in epidemiological intervention studies.
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