Panoramic stereo imaging system for efficient mosaicking: parallax analyses and system design.

Panoramic stereo images, captured by distributed devices then mosaicking, are competent contents for virtual reality applications. Mosaicking raw images with different perspectives into satisfying final results is still not efficient enough, even if state-of-the-art algorithms are employed. For improving this efficiency in optical methods, we delve into the potential of the capturing system. Two parallax factors, peak parallax and deviation of parallaxes, are proposed to assess the mosaicking capability. By controlling variables and numerical computation, rules between parallax factors and design parameters have been revealed. Validation by simulations, large capturing distance, more cameras, compact arrangement, and moderate overlaps are suggested as the general design strategy. Benefiting from efficient mosaicking, systems based on our design strategy would have potential for real-time applications.

Mercury concentration in the muscle of seven fish species from Chagan Lake, Northeast China.

Chagan Lake is located downstream of the Second Songhua River basin in Northeast China. It is one of the top ten inland freshwater lakes, and an important aquatic farm in China. The lake has been receiving large amounts (currently at 1.5 × 10(8) m(3)/a) of water from the river since 1984. This would pose a threat to the aquatic system of the lake because the river was seriously polluted with mercury in 1970s-1980s. The current study is the first to report the total mercury concentrations in fish found in the lake. Mercury concentrations in seven fish species collected from the lake in January 2009 were determined. The related human health risk from fish consumption was also assessed. The average concentration of mercury in the fish was 18.8 µg/kg of wet weight, ranging from 4.5 to 37.6 µg/kg of wet weight. A large difference in the mercury concentrations among the fish species was found. The mercury concentration was found to be higher in carnivorous species and lower in omnivorous and herbivorous species. This demonstrates greater mercury bioaccumulation in fish species at higher trophic levels. Mercury concentrations in fish showed significant positive correlations with age, length, and weight. No significant relationship was found between mercury concentrations in fish and the habitat preferences. Mercury concentrations in fish from the lake were within the limits of the international and national standards of China established for mercury. According to the reference doses established by the United States Environmental Protection Agency, the maximum safe consuming quantity considering all the fish was 297.3 g/day/person, which was more than five times as much as the current quantity (50 g/day/person) consumed by the local residents. This investigation indicates that the historical pollution of the Second Songhua River has not caused mercury bioaccumulation in fish muscle tissue of Chagan Lake. The present consumption of fish from the lake in the local area does not pose a threat to human health.

[Human hair mercury levels and the influencing factors of the residents living in Qianguo Irrigation Area].

To understand the current mercury exposure level of the residents living within the Second Songhua River basin, 120 hair samples were collected from Qianguo Irrigation Area in the downstream of the basin. The total mercury contents in hair samples were determined and the influencing factors were analyzed. The results showed that the range of the total mercury contents was 0.15-1.01 mg/kg and the average value was 0.56 mg/kg. The average hair mercury content of male residents was 0.55 mg/kg while that of female residents was 0.60 mg/kg. The total hair mercury firstly increased and then gradually decreased with the increasing of age. The lowest mean hair mercury value(0.47 mg/kg) was detected in the residents with the age of 0-20 and the highest mean hair mercury value (0.73 mg/kg) was detected in the residents with the age of 40-50. Among the other factors influencing human hair mercury contents, the gender, height, body weight, fish consumption, smoking and wine-drinking showed no significant correlations with the hair mercury contents. Only one hair sample was detected with greater mercury content than the limitation (1.00 mg/kg) established by USEPA, suggesting low mercury exposure risks in the area. This investigation indicated the historical pollution of the Second Songhua River hadn't lead health risks to the residents of the region and the irrigation using water from the river after the building of the Hadashan Reservoir would cause low environmental risks.

[Quantitative characteristics and source analysis of heavy metals in paddy soils in downstream of the Second Songhua River, Jilin Province].

In autumn 2008, a total of 65 plough layer soil samples were collected from the paddy fields in Qianguo Irrigation Area located at the downstream of the Second Songhua River. These paddy fields were irrigated with water from the River, and had different irrigation histories. The Cu, Pb, Zn, Cd, Ni, As, and Hg concentrations in the soil samples were determined, and the accumulation characteristics, input approaches, and pollution sources of these heavy metals were analyzed. The Cu, Pb, Zn, Cd, Ni, As, and Hg concentrations in the samples were 14.1-28.4 mg x kg(-1), 37.6-57.4 mg x kg(-1), 53.3-84.4 mg x kg(-1), 0.044-0.367 mg x kg(-1), 18.4-37.0 mg x kg(-1), 3.25-12.11 mg x kg(-1), and 0.031-0.155 mg x kg(-1), respectively. The Pb, Hg, and Cd exhibited an obvious accumulation trend, with their concentrations being 100.0%, 38.7%, and 66.1% higher than the baselines, respectively, while Cu, Zn, Ni, and As had less accumulation. With the increase of irrigation history, the Pb concentration showed a decreasing trend, while the Hg concentration was in reverse. There was no significant correlation between the Cd concentration and the irrigation history. According to source analysis, soil Pb mainly originated from the atmospheric Pb deposition via historical use of leaded gasoline, soil Hg was from the polluted irrigation water from the Second Songhua River, and soil Cd was from the use of chemical fertilizers, pesticides, and other agrochemicals. Though the Pb, Hg, and Cd had obviously accumulated in the paddy fields in Qianguo Irrigation Area, their potential ecological risk was still low, and would not pose threat on the local agricultural production and food security.