Water quality impacts from artisanal and small-scale alluvial (placer) gold mining operations occur in developing economies across several continents including Asia, Africa, and South America. They often occur in remote and/or resource-poor settings in which mitigation strategies must contend with extreme seasonal variation in river flow as well as the economic incentive to periodically churn (mine) alluvial floodplains without riparian restoration. A novel strategy addressing these constraints is herein explored which employs the alluvial floodplain for filtration-driven removal of particulate contaminants and gold from streams. This process of lateral channel filtration is explored in the Rio Nambija of southern Ecuador, in terms of success in achieving the hydraulic objective of passively driven lateral flow, and the corresponding removal of particulate contaminants (e.g., total mercury, lead, iron, and manganese) by filtration. Accumulation of gold was examined to evaluate whether incorporation of this proposed practice in alluvial (placer) mining can reduce particle-bound contaminants in streams and simultaneously increase economic benefit. Excavation of channels lateral to mining-impacted streams was shown to achieve the hydraulic, water quality, and economic (gold accumulation) objectives. The modest flow capture for any given lateral segment, along with the months-long timescale associated with economic gold accumulation and clogging by suspended solids, dictate a “cultivation” process whereby multiple lateral segments are worked annually.

Whereas mining and non-mining sourced particulate metal/metalloids (PM) (> 0.45 μm) are present in the tributaries of the San Juan River, USA, the individual contributions of PM from the San Juan River tributaries to the sediment of the San Juan River Delta of Lake Powell were previously unknown. Suspended PM signatures, including enrichment factors (ratios of PM concentrations to ubiquitous metals such as aluminum), lead isotopes, color, and particle size, were used to tie layers in a San Juan River sediment core to upstream tributary sources. Tributary PM concentrations and loads were compared to Lower San Juan River suspended PM loads to estimate the relative contribution of tributary PM (both mining and non-mining sourced) directly upstream of Lake Powell. Results suggest elevated enrichment factors of lead, cadmium, copper, and zinc in deposited sediment were sourced from mined tributaries, whereas elevated manganese in deposited sediment was sourced from unmined tributaries. Sediment Pb isotope ratios reflected the depleted signature of the mineralized vein (present in the headwaters of mined tributaries), the enriched signature of the Chinle Sandstone (predominant underlying geology of unmined tributaries), or a mixture of these two endmembers. These independent lines of evidence were used to link probable tributary source and runoff category to sediment layers, where ~ 10% and 5% of the overall PM deposited in the sediment core was attributed to mining versus non-mining sources, respectively. Because traditional dating methods were not possible, runoff category signatures were used to estimate that the 3.37 m San Juan River Delta core was deposited over ~ 1.3 years.

Previous paleoclimate studies have suggested a warm/dry event during the mid-Holocene in páramo vegetation of the tropical Andes of South America. However, the timing of the mid-Holocene warm/dry event in Tres Lagunas, Ecuador, remains uncertain, since a previously reported bog core record characterized the warm/dry event during a hiatus in sediment deposition. In order to understand the timing of the warm/dry event in Tres Lagunas in relation to regional records, a lake sediment core was collected. Subsamples from the core were analyzed for radiocarbon dates, pollen, magnetic susceptibility, and charcoal to reconstruct the depositional, vegetational, and fire history of the area. A near-constant sedimentation rate in the lake core indicated that the lake did not dry, in contrast to the adjacent previously reported bog core. Increases in lower elevation pollen types suggest a warm period between 2700 and 2200 cal. yr BP, with the peak of warming at 2200 cal. yr BP co-occurring with the end of hiatus in the bog core record. Statistically significant increases in charcoal influx and magnetic susceptibility from 3900 to 800 cal. yr BP also suggest a dry climate during this period. While the lake record corroborates the presence of a warm/dry period in Tres Lagunas during the mid-Holocene, this record suggests a shorter period of warm/dry climate where the intensity was not sufficient to cause the lake to dry. However, anthropogenic alteration of the landscape, either vegetation or burning, must also be considered when interpreting Holocene records from this region.

Failures in either water systems or food systems, or a combination of system failures, could provide the underlying explanation for continued high levels of malnutrition in many regions. We focus on child health and offer the first spatially explicit analysis of the interaction between water source and food insecurity on children’s health in Burkina Faso, an African nation that continues to struggle with poor children’s health. We combine data from the 2010 Demographic and Health Survey, a small USAID water quality survey collected from community wells, and remotely sensed imagery. Results suggest that, in a few cases, reliable and clean water sources are positively correlated to children’s linear growth and weight gain, although in many regions, the interaction with community-level food production is critical to understanding health outcomes. The results also suggest that maternal health and nutrition during pregnancy and breastfeeding are foundational to the healthy development of young children. In all, the findings provide evidence of the importance of multi-sectoral interventions targeted at improving children’s health.

Arsenic contamination in groundwater is a public health and environmental concern in the United States (U.S.) particularly where monitoring is not required under the Safe Water Drinking Act. Previous studies suggest the influence of regional mechanisms for arsenic mobilization into groundwater; however, no study has examined how influencing parameters change at a continental scale spanning multiple regions. We herein examine covariates for groundwater in the western, central and eastern U.S. regions representing mechanisms associated with arsenic concentrations exceeding the U.S. Environmental Protection Agency maximum contamination level (MCL) of 10 parts per billion (ppb). Statistically significant covariates were identified via classification and regression tree (CART) analysis, and included hydrometeorological and groundwater chemical parameters. The CART analyses were performed at two scales: national and regional; for which three physiographic regions located in the western (Payette Section and the Snake River Plain), central (Osage Plains of the Central Lowlands), and eastern (Embayed Section of the Coastal Plains) U.S. were examined. Validity of each of the three regional CART models was indicated by values >85% for the area under the receiver-operating characteristic curve. Aridity (precipitation minus potential evapotranspiration) was identified as the primary covariate associated with elevated arsenic at the national scale. At the regional scale, aridity and pH were the major covariates in the arid to semi-arid (western) region; whereas dissolved iron (taken to represent chemically reducing conditions) and pH were major covariates in the temperate (eastern) region, although additional important covariates emerged, including elevated phosphate. Analysis in the central U.S. region indicated that elevated arsenic concentrations were driven by a mixture of those observed in the western and eastern regions.

Similar to fracking, the development of tar sand mining in the U.S. has moved faster than understanding of potential water quality impacts. Potential water quality impacts of tar sand mining, processing, and disposal to springs in canyons incised approximately 200m into the Tavaputs Plateau, at the Uinta Basin southern rim, Utah, USA, were evaluated by hydrogeochemical sampling to determine potential sources of recharge, and chemical thermodynamic estimations to determine potential changes in transfer of bitumen compounds to water. Because the ridgetops in an area of the Tavaputs Plateau named PR Spring are starting to be developed for their tar sand resource, there is concern for potential hydrologic connection between these ridgetops and perennial springs in adjacent canyons on which depend ranching families, livestock, wildlife and recreationalists. Samples were collected from perennial springs to examine possible progression with elevation of parameters such as temperature, specific conductance, pH, dissolved oxygen, isotopic tracers of phase change, water-rock interaction, and age since recharge. The groundwater age dates indicate that the springs are recharged locally. The progression of hydrogeochemical parameters with elevation, in combination with the relatively short groundwater residence times, indicate that the recharge zone for these springs includes the surrounding ridges, and thereby suggests a hydrologic connection between the mining, processing, disposal area and the springs. Estimations based on chemical thermodynamic approaches indicate that bitumen compounds will have greatly enhanced solubility in water that comes into contact with the residual bitumen–solvent mixture in disposed tailings relative to water that currently comes into contact with natural tar.