Mercury [Hg, 80]
205
inputs from North America, Asia, and Europe, linked especially to coal burning
and solid waste incineration. There are some suggestions that Hg concentrations
were higher in snow dated from the late 1940s to the mid-1960s, than in more
recent snow. Luckily, various forecasts for the Hg emission in Europe are lower
for 2020 than those for 2010. However, these estimations highly vary and are 64,
125, and 180 t/yr, depending on the authors. The general tendency in reducing
Hg emission from the anthropogenic sources is clearly shown by its significant
decrease in the 1990s (by 60%) compared to its emission in the 1970s (Pacyna
and Pacyna 2001).
Mosses are very sensitive indicators for Hg concentration in air. Its average
content was 0.08 mg/kg of moss sampled in Norway during 1990–1995 (Berg and
Steinnes 1997). Mean Hg content of mosses (Hylocomium splendens) from Poland
was 0.084 mg/kg, whereas of those collected in Southern Alaska was 0.131 mg/kg
(Migaszewski et al. 2009). The authors concluded that this variation in Hg contents
of mosses is linked to both the location of emission point sources and underlying
geology.
Me
27.5 PLANTS
rcury is easily phytoavailable; therefore, in most cases, its concentrations in
plants increase with its elevated contents in soils. Plants differ in their ability to
uptake Hg, and can develop a tolerance to its high contents in growth media. Plants
uptake Hg mainly by roots, where it is accumulated. Its translocation to shoots is
relatively small. This is well illustrated by Asparagus acutifolius from the Almaden
district (Hg mine in Spain), which contains Hg (in mg/kg) 7.7 in stems and 298.2 in
roots. Mercury is also taken up from the atmosphere. Some plants, such as lettuce,
spinach, and mushrooms are likely to take up more Hg than other plants, most
probably also from the air (Table 27.3). Some plants (e.g., Indian mustard, Brassica
juncea) reveal the ability to uptake great amounts of Hg from contaminated soil.
The highest contents of Hg in this plant grown in soils with Hg at 1000 mg/kg, was
as follows (in mg/kg): 264–325 in shoots and 1775–2089 in roots (Su et  al. vide
Kabata-Pendias 2011).
All forest berries grown in the polluted area of the Northern Europe (Kola
Peninsula) contain similar amounts of Hg, <0.04 mg/kg (Reimann et al. 2001).
Common mushroom, chanterelles (Cantharellus cibarius) grown in mountains
of Poland and in the Baltic Sea coast contain similar amounts of Hg, about
0.037 mg/kg (Falandysz et  al. 2012). Another mushroom, red aspen boletes
(Leccinum aurantiacum) contain Hg within the range of 0.27–1.3  mg/kg.
Bioconcentration factor was much higher for mushroom caps than for stipes
(Falandysz et al. 2012).
Mercury content of plants has recently received much attention because of its pathway into the food chain. The background levels of Hg in vegetables and fruits vary
from about 0.003 to 0.09 mg/kg DW, and from 0.006 to 0.07 mg/kg FW. However,
plants cultivated in industrial regions may contain its higher concentrations. The Hg
contents of cereal grains seem to be fairly similar for the same kind of plants grown
in various countries, and vary from <0.0001 to 0.034  mg/kg. In countries where