Latest Score:


in 2019

score trend is flat over time
Weight: 2%

Mercury is a persistent bioaccumulative toxin, which means that it stays in the environment for a long time, cycling through air, water, and soil. Mercury can be deposited by wet and dry deposition, and is assimilated into plants and soils. It accumulates in organisms, leading to damage with long-term consequences1. Elevated mercury can cause reductions in growth and reproduction, and increases the rate of wildlife mortality. Here, we quantify the annual amount of mercury deposited at an air quality site in Underhill, Vermont. Annual scores are computed as the difference between the target concentration of 0 µg/m2 and the maximum (the maximum value in record + 10% of the range).

1Driscoll, C.T., Han, Y.J., Chen, C.Y., Evers, D.C., Lambert, K.F., Holsen, T.M., Kamman, N.C. and Munson, R.K., 2007. Mercury contamination in forest and freshwater ecosystems in the northeastern United States. BioScience, 57(1), pp.17-28.

-- Expert interpretation for Mercury Deposition is not available--

The score is calculated using a target value and the historical range of the the entire long-term dataset. The higher the score, the closer this year's value is to the target.

Once the score is computed for each year, the trend in scores over time is calculated. If the trend is significantly positive or negative, the long-term trend is marked as increasing or decreasing respectively.

Component Description
Scored as

Distance between target and maximum (scaled 1-5)

Target value


Directionality of scores

Lower values in the data are better.

Minimum value used in scoring


Maximum value used in scoring

Data maximum + 10% of range

Data on mercury deposition (µg/m2) were accessed from the National Atmospheric Deposition Program (NADP) Mercury Deposition Network (MDN) for sites at Underhill, Vermont1. Annual values are computed from weekly samples collected at the site. We set the target for mercury deposition to zero2. The annual score was computed as the difference between the target concentration of 0 µg/m2 and upper scoring bounds (maximum value in the data plus 10% of the range). This difference was then scaled between 1-5.

1 National Atmospheric Deposition Program. 2017. Mercury Deposition Network Available at: