Koyomi Nakazawa

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).

Foehnlike Wind with a Traditional Foehn Effect plus Dry-Diabatic Heating from the Ground Surface Contributing to High Temperatures at the End of a Leeward Area

AbstractA foehn wind is an important factor in the occurrence of many extreme high-temperature events in geographically complex regions. In this study, the authors verified the hypothesis that a foehnlike wind contributes to high temperatures at the end of the leeward (eastward) area using three difference approaches: field experiments, numerical experiments, and statistical analyses. According to the hypothesis, a foehnlike wind has the features of the sum of a traditional foehn effect with adiabatic heating, plus dry-diabatic heating from the ground surface along the fetch of the wind. Field experiments conducted at seven observational points on Nobi Plain, Japan, where a mesoscale westerly wind blew, revealed that the westerly wind clearly had the features of a traditional foehn effect in the western part of the Nobi Plain. In addition to field experiments, a simplified estimate using a simple mixed-layer model demonstrated that the wind was further heated by dry-diabatic heating (sensible heat supply)...

Hydrochemical Characteristics of the Mongolian Plateau and its Pollution Levels

Increasing large-scale and rampant small-scale mining activity in Mongolia is raising fears about the possibility of regional environmental pollution. To characterise the level of groundwater pollution related to large- and small-scale underground resource development in the Mongolian plateau, we analysed 10 groundwater and 3 surface water samples collected from three areas: the Oyu Tolgoi mining area (n = 3), the Tavan Tolgoi mining area (n = 9) and an abandoned small-scale gold-mining site in the suburban of Ulaanbaatar (n = 1). The samples were collected between 29 August and 5 September 2012. Measurement parameters included pH; electrical conductivity; dissolved organic carbon; dissolved nitrogen; and the concentrations of major ions and trace elements. Principal component analyses, Piper diagrams and enrichment factor analyses were applied to a set of hydrochemical data. Water samples were analysed to identify components that may adversely affect the regional environment and human health. Analytical measurements showed that the studied sites were highly affected by fossil salt water and trace elements derived from anthropogenic activity. We found that groundwater samples from the Oyu Tolgoi area were more polluted than those from the Tavan Tolgoi area. Because wells in the pasture area adjacent to the mining sites supply drinking water for livestock and nomads, it is especially important to monitor these wells for NO3−, As and Se, for which the World Health Organisation has established drinking-water guidelines. The concentrations of NO3−, As and Se in wells may be used as indicators to evaluate the human and livestock health risks related to mining activity in this area.