RESUMEN
Domestic wells serve as the primary drinking-water source for rural residents in the northern Appalachian Basin (NAB), despite a limited understanding of contaminant distributions in groundwater sources. We employ a newly collected dataset of 216 water samples from domestic wells in Ohio and West Virginia and an integrated contaminant-source attribution method to describe water quality in the western NAB and characterize key agents influencing contaminant distributions. Our results reveal arsenic and nitrate concentrations above federal maximum contaminant levels (MCLs) in 6.8 and 1.3% of samples and manganese concentrations above health advisory in 7.3% of samples. Recently recharged groundwaters beneath upland regions appear vulnerable to surface-related impacts, including nitrate pollution from agricultural activities and salinization from road salting and domestic sewage sources. Valley regions serve as terminal discharge points for long-residence-time groundwaters, where mixing with basin brines is possible. Arsenic impairments occurred in alkaline groundwaters with major-ion compositions altered by ion exchange and in low-oxygen metal-rich groundwaters. Mixing with as much as 4-10% of mine discharge-like waters was observed near coal mining operations. Our study provides new insights into key agents of groundwater impairment in an understudied region of the NAB and presents an integrated approach for contaminant-source attribution applicable to other regions of intensive resource extraction.
Asunto(s)
Arsénico , Agua Subterránea , Contaminantes Químicos del Agua , Arsénico/análisis , Monitoreo del Ambiente , Manganeso , Nitratos , Compuestos Orgánicos , Oxígeno , Aguas del Alcantarillado , Contaminantes Químicos del Agua/análisisRESUMEN
Eighteen patients with glaucoma who failed to respond (0 dB) to maximum intensity (1,000 apostilbs) No. 3 (4 mm2) stimuli during threshold static perimetry performed with an Octopus automated perimeter were retested using the same test program with No. 5 (64 mm2) stimuli. All responded to the larger stimulus at the 5-dB (315 apostilbs) level or higher in at least three previously undetected locations. Ten of the 18 patients responded in at least 80% of the locations they were unable to detect with smaller stimulus. After four patients were tested twice with the No. 5 stimulus the improvement in response was confirmed. The use of the larger-sized stimulus permitted us to measure visual function in areas that had been considered absolute scotomas with the standard-sized stimulus. In this way, we can monitor changes that may occur in these areas in the future.