Spatial Distributions of Mercury Deposition in the Lake Biwa Watershed, Japan

Abstract

To clarify the regional difference in mercury pollution the Lake Biwa watershed in central Japan, we monitored the mercury concentration in rainwater at four sites in the Lake Biwa watershed in Shiga prefecture. These observation sites were as follows Surumi as the northern site, Kutsuki as the western site, Aburahi as the southern site and Hikone as the eastern site. The total mercury average concentrations in Surumi, Kutsuki, Aburahi, and Hikone were 6.67±1.74 ng • L , 5.98±1.66 ng • L , 8.76±3.29 ng • L , and 7.45±2.08 ng • L , respectively. We estimated the annual mercury deposition in 2012 in Surumi, Kutsuki, Aburahi, and Hikone, and found into range from 10.4 to 17.5 μg • m . The Lake Biwa watershed is wide to the north and south, and the environmental conditions are different between sites. The mercury deposition markedly fl uctuates throughout the north and south of the Lake Biwa watershed. Therefore, it is necessary to evaluate the direct mercury load to Lake Biwa through rainwater at many sites.