Record of mercury pollution in sediments of lakes Nakaumi and Shinji in Japan

Abstract

Two sediment core profiles from lakes Shinji and Nakaumi were studied in order to understand the level of mercury (Hg) pollution in lakes in northwestern Japan. The sedimentation rates were established on the basis of the activity of [210Pb] and [131Cs] in the sediments. In Lake Shinji, the highest level of Hg (130 ng g–1) in the sediment was found at a depth of 20–22 cm, while 195 ng g–1 was found at a depth of 10–12 cm in the core profiles from Lake Nakaumi. The relative increase in Hg concentration in lake sediments started after 1960 and significant contamination events occurred in the early 1960s. Mercury profiles in lake sediments from lakes Shinji and Nakaumi are found to reflect the anthropogenic Hg released into the environment in the 1950s and 1960s. A pronounced maximun concentration of Hg is found in both lakes, where sediment accumulation rates differ.

Historical change in lake sedimentation in Lake Takkobu, Kushiro Mire, northern Japan over the last 300 years

“…The 137 Cs concentration has been used to estimate the rate of lake sediment accretion Foster and Lees, 1999;Walling et al, 2003). The peak activity has been used to determine the depths of the 1963 surface (Robbins and Edgington, 1975;Mahara, 1993;Walling and He, 1997;Chandrajith et al, 2001;Walling et al, 2003), and the lowest depths that have significant 137 Cs concentrations have been used to identify sediments from the mid-1950s. However, in both cases, it was necessary to take account of the post-depositional redistribution of radiocaesium in the sediment core, since redistribution by bioturbation and molecular diffusion influences the concentration of radiocaesium (Davis et al, 1984;Sholkovitz and Mann, 1984;Smith and Comans, 1996).…”

Mercury Contamination in Costa Rica

“…Clement and Horn, 2001 Similar to the total Hg profiles the calculated Hg MAR rates varied considerably between lakes (Table 5-3), with averages for each core ranging from 1.80-38.75 ng Hg cm -2 yr -1 . Increased Hg MAR in response to increased emissions have been clearly documented (Chandrajith et al, 2001). For example, in New England background Hg MAR is ~1-4 ng Hg cm -2 yr -1 , and peak accumulation, in response to anthropogenic input is ~9-35 ng Hg cm -2 yr -1 (Varekamp et al, 2000).…”

“…Although the ratio of mercury released may be much greater for other industrial activities (Zinc smelting for example has an emission factor of 7.5-8.0g Hg per tonne), the sheer quantity of coal burned globally makes coal combustion the largest contributor by far to anthropogenic mercury emissions. The increase in coal emissions over the last century has led to a corresponding increase in mercury present in the environment (Mason et al, 1994) and is clearly reflected in natural archives (Chandrajith et al, 2001). In Connecticut, for example, increased atmospheric deposition of mercury corresponding to the onset of the industrial revolution is documented in sediment cores from lakes and coastal marshes (Varekamp at al., 2003).…”