Risk assessment of fluoride and arsenic in groundwater and a scenario analysis for reducing exposure in Inner Mongolia.

In contrast to Mongolia, family-owned land in Inner Mongolia is separated by fences, preventing the free movement of nomads and leading people to rely heavily on the same source of groundwater for their domestic water needs. Therefore, it is important to clarify groundwater quality and understand the associated human health concerns. To evaluate the risks of drinking groundwater to human health in Inner Mongolia, we examined groundwater quality by field surveys, a human health risk analysis, and a scenario analysis. During the summer of 2015 in Inner Mongolia, we measured the concentrations of major ions, metals, metalloids, and rare earth metals in groundwater samples (n = 32) and river water samples (n = 10), for which there were no known anthropogenic contamination sources. In addition, as part of a scenario analysis, samples of tap water (n = 1), snowmelt (n = 1), and bottled water (n = 1) were also evaluated. We used our analytical results to calculate hazard quotient (HQ) ratios by means of a probabilistic risk assessment method. The results indicated that residents who drank groundwater every day might have risk concerns for F- (mean ± standard deviation, 2.51 ± 1.80 mg L-1; range, 0.07-7.70 mg L-1) and As (6.49 ± 9.64 µg L-1; 0.31-47.0 µg L-1). We observed no relationships between well depth or any geophysical variation and groundwater quality. On the basis of the scenario analysis results, we concluded that using snow as a source of drinking water in winter could reduce health risks associated with using groundwater for this population in Inner Mongolia.

Flagellum expression and swimming activity by the zoonotic pathogen Escherichia albertii.

Flagella are the well-known structural appendages used by bacteria for motility. Although generally reported to be non-motile, the enteropathogenic bacterial species Escherichia albertii produces flagella intermittently. We found that E. albertii expressed flagella under specific environmental conditions. After several generations (involving 4 to 12-h incubations), six of the twelve strains we investigated displayed swimming motility in various aquatic environments, including pond water containing nutrients from pigeon droppings (10% suspension) as well as in 20 × -diluted tryptic soy broth. The most significant motility determinant was a temperature between 15 and 30 °C. At 20 °C in the 10% pigeon-dropping suspension, microscopic observations revealed that some cells (1%-95% of six strains) showed swimming motility. Electron microscopy showed that the E. albertii cells expressed flagella. Lower concentrations of some substrates (including nutrients) may be of secondary importance for E. albertii flagella expression. Interestingly, the non-motile strains (n = 6/12) contained pseudogenes corresponding to essential flagella structural proteins. After being released from its host into surface water, E. albertii may express flagella to move toward nutrient sources or new hosts.

Non-carcinogenic risk assessment of groundwater in South Gobi, Mongolia.

Thirty-nine groundwater samples were collected from wells near the Tavan Tolgoi and Oyu Tolgoi mines in Mongolia and at a relatively pristine site in northern Mongolia during August to September 2013, and analyzed for the concentrations of F-, NO3-, Hg, As, Al, V, Mn, Co, Ni, Cu, Zn, Se, Mo, Cd, Sb, and Pb. A probabilistic risk assessment found that >95% of the population in the areas was at risk from drinking well water. The hazard index (HI) was >1, indicating a non-carcinogenic risk to human health. At Oyu Tolgoi, the hazard quotient (HQ) of the As concentration (mean 6.63 µg/L) was >1. At the northern site, the 95th percentile HQ was <1 but the 95th percentile HI was >1. The ratios of nitrogen and oxygen stable isotopes indicated that NO3- contamination of groundwater at Oyu Tolgoi and Tavan Tolgoi was caused by livestock waste. Mercury accumulation in livestock was examined from concentrations in livestock forage and in hair and wool samples from livestock in the South Gobi region. Sheep wool had the same level of mercury as in Japan, but camel, horse, and goat hair had high levels.

Human health risk assessment of mercury vapor around artisanal small-scale gold mining area, Palu city, Central Sulawesi, Indonesia.

Emissions of elemental mercury, Hg(0), from artisanal small-scale gold mining activities accounted for 37% of total global Hg(0) emissions in 2010. People who live near gold-mining areas may be exposed to high concentrations of Hg(0). Here, we assessed the human health risk due to Hg(0) exposure among residents of Palu city (Central Sulawesi Province, Indonesia). The area around the city has more than 60t of gold reserves, and the nearby Poboya area is the most active gold-mining site in Indonesia. Owing to its geography, the city experiences alternating land and sea breezes. Sampling was done over a period of 3 years (from 2010 Aug. to 2012 Dec.) intermittently with a passive sampler for Hg(0), a portable handheld mercury analyzer, and a mercury analyzer in four areas of the city and in the Poboya gold-processing area, as well as wind speeds and directions in one area of the city. The 24-h average concentration, wind speed, and wind direction data show that the ambient air in both the gold-processing area and the city was always covered by high concentration of mercury vapor. The Hg(0) concentration in the city was higher at night than in the daytime, owing to the effect of land breezes. These results indicate that the inhabitants of the city were always exposed to high concentrations of Hg(0). The average daytime point-sample Hg(0) concentrations in the city, as measured with a handheld mercury analyzer over 3 days in July 2011, ranged from 2096 to 3299ngm(-3). In comparison, the average daytime Hg(0) concentration in the Poboya gold-processing area was 12,782ngm(-3). All of these concentrations are substantially higher than the World Health Organization air-quality guideline for annual average Hg exposure (1000ngm(-3)). We used the point-sample concentrations to calculate hazard quotient ratios by means of a probabilistic risk assessment method. The results indicated that 93% of the sample population overall was at risk (hazard quotient ratio ≥1 and cut off at the 95th percentile value of the sample population) of mercury toxicity, that is, damage to the central nervous system due to chronic exposure. The corresponding percentages for the northern, central, southern, and western areas of the city were 83%, 84%, 95%, and 95%, respectively. Our results indicate that the residents of Palu city are at serious risk from exposure to high concentrations of atmospheric Hg(0).

Binding interactions of 1-naphthol with dissolved organic matter of Lake Biwa and treated sewage wastewater: The role of microbial fulvic acid.

The binding interactions of 1-naphthol with effluent and whole natural dissolved organic matter (DOM) samples were analyzed by using a fluorescence quenching technique. Nonfractionated DOM samples from Lake Biwa (Japan), creek water, treated sewage effluents, and an extracted Lake Biwa fulvic acid (LBFA) standard were used as quenchers and compared at the same 1-naphthol with DOM organic carbon ratios found for low natural dissolved organic carbon (DOC) levels (∼4.5 mg/L). Natural and effluent DOM (eDOM) samples were characterized by the DOC level, relative hydrophobicity (RH%), ultraviolet (UV)-visible absorbance and fluorescence excitation emission spectroscopy. These parameters were compared with those of the reference LBFA standard. Concave-up Stern-Volmer plots accounted for both the partitioning and the adsorptive binding in the eDOM-polycyclic aromatic hydrocarbons (PAH) system as compared with the nonspecific partitioning in the natural DOM-PAH system. Strong linear regressions (r(2) > 0.80) between the log K(DOC) values, the RH%, the UV absorbances, and the Fl(340-435) -UV(340) indices for the structural composition and molecular weights of the DOM samples were obtained. These results suggest that low molecular weight microbial fulvic acid (<800 Da) is dominant in the eDOM-PAH binding interactions, as well as in the distinct molecular structure of the eDOM samples, which resulted in fivefold to sixfold higher binding magnitude for 1-naphthol than for the other samples.