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    The arsenic-removing capacity of some low-cost materials was tested by passing aqueous arsenic solutions (16 and 57 ppb) of pH 7 through materials packed in plastic buckets. It was found that the initial concentration of arsenic solutions and their retention time in adsorbents greatly affected the removal of arsenic from the aqueous solution. Maximum arsenic removal was observed when the packed materials were exposed to 16 ppb of arsenic solution. With 57 ppb of arsenic solution, arsenic removal was reduced on that of 16 ppb; however, the reduced arsenic concentration was close to the recommendations of the World Health Organization drinking water quality guidelines.
    Abstract Globally significant quantities of carbon (C), nitrogen (N), and phosphorus (P) enter freshwater reservoirs each year. These inputs can be buried in sediments, respired, taken up by organisms, emitted to the atmosphere, or exported downstream. While much is known about reservoir-scale biogeochemical processing, less is known about spatial and temporal variability of biogeochemistry within a reservoir along the continuum from inflowing streams to the dam. To address this gap, we examined longitudinal variability in surface water biogeochemistry (C, N, and P) in two small reservoirs throughout a thermally stratified season. We sampled total and dissolved fractions of C, N, and P, as well as chlorophyll-a from each reservoir’s major inflows to the dam. We found that heterogeneity in biogeochemical concentrations was greater over time than space. However, dissolved nutrient and organic carbon concentrations had high site-to-site variability within both reservoirs, potentially as a result of shifting biological activity or environmental conditions. When considering spatially explicit processing, we found that certain locations within the reservoir, most often the stream–reservoir interface, acted as “hotspots” of change in biogeochemical concentrations. Our study suggests that spatially explicit metrics of biogeochemical processing could help constrain the role of reservoirs in C, N, and P cycles in the landscape. Ultimately, our results highlight that biogeochemical heterogeneity in small reservoirs may be more variable over time than space, and that some sites within reservoirs play critically important roles in whole-ecosystem biogeochemical processing.
    Biogeochemical Cycle
    Biogeochemistry