Osamu Nagafuchi

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).

Monitoring of nitrogen compounds on Yakushima Island, a world natural heritage site

Abstract The concentrations of NH 4 and NO 3 along with other cations and anions in atmospheric deposition (rain and snow) and river water were determined on Yakushima Island, a world natural heritage site. The results suggested that the major source of N compounds entering the ecosystem is atmospheric deposition, and that forest and river ecosystems in the high mountainous area are maintained on nutrient-poor granite bedrock. There was a seasonal change in the rainfall and in concentrations of NH 4 and NO 3 in rain. The amount of rainfall was relatively higher in April to October and the concentrations of N compounds were relatively higher in November to March. The NH 4 NO 3 ratio in rain water was about 1.0 in November to March, suggesting the equal amount of NH 4 and NO 3 is supplied to the forests of Yakushima Island as nutrients before the spring growth of plants. The concentrations of nutrients, especially NH 4 and NO 3 , in river water on this island are extremely low (e.g. St. Y1, Apr 1994–Dec 1995: NH 4 1.1 μeq l −1 NO 3 0.20 μeq l −1 , SO 4 29.6 μeq l −1 , Cl 105 μeq l −1 , K 5.3 μeq l −1 , Mg 25.7 μeq l −1 , Ca 33.4 μeq l −1 ). The difference in the concentration of NH 4 and NO 3 in atmospheric deposition compared with river water would suggest a limited nutrient supply on the granitic precipitous island. It also implicated a chemical and biological uptake system in the ecosystem, such as uptake of NH 4 and NO 3 by Cryptomeria japonica , as a background feature of the characteristically slow-growing but thick mature forest.

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.

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)...

Atmospheric nitrate leached from small forested watersheds during rainfall events: Processes and quantitative evaluation

To determine the availability of atmospheric NO3− deposition on forested ecosystems and to understand the interaction between the nitrogen cycle in a forest ecosystem and atmospheric nitrogen input/output, we quantitatively evaluated the atmospheric NO3− passing through forested watersheds by measuring δ18ONO3 leaching during rainfall events in two forest ecosystems (Su-A and Ab-S). Atmospheric NO3− leaching in rainfall events was clearly higher in Ab-S than in Su-A, even for a similar amount of rainfall, which demonstrated that atmospheric NO3− leaching differs among forested watersheds. Our observations suggest that a large part of the atmospheric NO3− leached from the watersheds was derived from surface soil, which was deposited before rainfall events occurred; however, direct atmospheric NO3− leaching via throughfall discharge also contributed, especially at the beginning of rainfall events. In Ab-S, 2.9–37.8% (average = 15.5%) of atmospheric NO3− deposition passed through the watershed, accounting for 3.1–49.8% (average, 26.4%) of the total NO3− leached during rainfall events. The NO3− input was not large, and the NO3− pool and net nitrification rate were small; therefore, nitrogen was not saturated in the soil at Ab-S. Nevertheless, some of the atmospheric NO3− deposition was not assimilated and was leached immediately. Moreover, our observations suggest that the hydrological characteristics of the watersheds, which control the ease of rainwater discharge, strongly influenced the rate of atmospheric NO3− leaching. This suggests that the hydrological characteristics of watersheds influence the availability of atmospheric NO3− deposition in forested ecosystems and the progression of nitrogen saturation.

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.