Contamination of water and soil by the Erdenet copper–molybdenum mine in Mongolia

As one of the largest copper–molybdenum (Cu–Mo) mines in the world, the Erdenet Mine in Mongolia has been active since 1978 and is expected to continue operations for at least another 30 years. In this study, the potential impacts of mining activities on the soil and water environments have been evaluated. Water samples showed high concentrations of sulfate, calcium, magnesium, Mo, and arsenic, and high pH values in the order of high to low as follows: tailing water > Khangal River > groundwater. Statistical analysis and the δ²H and δ¹⁸O values of water samples indicate that the tailing water directly affects the stream water and indirectly affects groundwater through recharge processes. Soil and stream sediments are highly contaminated with Cu and Mo, which are major elements of ore minerals. Based on the contamination factor (CF), the pollution load index (PLI), and the degree of contamination (C_d), soil appears to be less contaminated than stream sediments. The soil particle size is similar to that of tailing materials, but stream sediments have much coarser particles, implying that the materials have different origins. Contamination levels in stream sediments display a tendency to decrease with distance from the mine, but no such changes are found in soil. Consequently, soil contamination by metals is attributable to wind-blown dusts from the tailing materials, and stream sediment contamination is caused by discharges from uncontained subgrade ore stock materials. Considering the evident impact on the soil and water environment, and the human health risk from the Erdenet Mine, measures to mitigate its environmental impact should be taken immediately including source control, the establishment of a systematic and continuous monitoring system, and a comprehensive risk assessment.     

GNSS integration with vision-based navigation for low GNSS visibility conditions

In urban canyons, buildings and other structures often block the line of sight of visible Global Navigation Satellite System (GNSS) satellites, which makes it difficult to obtain four or more satellites to provide a three-dimensional navigation solution. Previous studies on this operational environment have been conducted based on the assumption that GNSS is not available. However, a limited number of satellites can be used with other sensor measurements, although the number is insufficient to derive a navigation solution. The limited number of GNSS measurements can be integrated with vision-based navigation to correct navigation errors. We propose an integrated navigation system that improves the performance of vision-based navigation by integrating the limited GNSS measurements. An integrated model was designed to apply the GNSS range and range rate to vision-based navigation. The possibility of improved navigation performance was evaluated during an observability analysis based on available satellites. According to the observability analysis, each additional satellite decreased the number of unobservable states by one, while vision-based navigation always has three unobservable states. A computer simulation was conducted to verify the improvement in the navigation performance by analyzing the estimated position, which depended on the number of available satellites; additionally, an experimental test was conducted. The results showed that limited GNSS measurements can improve the positioning performance. Thus, our proposed method is expected to improve the positioning performance in urban canyons.     

Spring Distribution of Ciliate Plankton in the Southeastern Yellow Sea in 2019

Ocean Science Journal - As planktonic ciliates have been recognized as important players in marine microbial food webs, relevant studies have been conducted in the western coastal waters of the...     

Seasonal variations in the low-salinity intermediate water in the region south of sub-polar front of the East Sea (Sea of Japan)

Seasonal variations in the low-salinity intermediate water (ESIW) in the region south of the sub-polar front of the East Sea were investigated by using historical hydrographic data. The salinity of the representative density (sigma-0=27.2) of the ESIW was minimal in summer and maximal in winter in the region south of the sub-polar front. The selected four subregions showed different salinity variations. In the west of Oki Spur and the Yamato Basin, salinity fluctuated similarly, with a minimum during summer. In the Ulleung Basin and northwest of Sado Island, however, variations in salinity showed two minima, one is in winter and the other is in summer. These results imply differences in the flow path of the ESIW into the region south of the sub-polar front over time.