Air Quality Criteria for Lead Volume II of II - (NEPIS)(EPA) - US ...

However, in other cases multivariate techniques were used. Therefore, where appropriate, some
detail on the statistical methods used is presented.
Although most of the available studies discussed in this section focus on the biotic
condition, one case study examining multiple components of the EPA conceptual framework is
also included. The remainder of this section describes the effects of Pb on the biotic condition.
AX7.2.5.1 Case Study: Coeur d’Alene River Watershed
The Coeur d’Alene River watershed is an area of Idaho impacted by Pb and other metals
from historic mining waste releases. Maret et al. (2003) examined several ecological
components to determine any negative associations with metals and the watershed communities.
The variables examined and associated ecological conditions are presented in Table AX7-2.5.1.
In addition to measurements of non-metal variables (e.g., dissolved oxygen levels, water
temperature and pH, embeddedness), Cd, Pb, and Zn levels were also compared in affected sites
versus reference sites.
Some of the above non-metal variables are important to macroinvertebrate communities.
For example, a stream with highly embedded substrate can have a lower number of individuals
within a species or a different species composition compared to a stream with less embeddedness
(Waters, 1995). Macroinvertebrates from the Ephemeroptera (mayflies), Plecoptera (stoneflies),
and Trichoptera (caddisflies) (EPT) group inhabit the surface of cobble and the interstitial spaces
between and underneath cobble. When substrate is embedded, these interstitial spaces are filled,
leaving less habitat space for EPT taxa. In another example, water temperature is important;
some macroinvertebrates (e.g., stoneflies) are usually only found in cooler water (Harper and
Stewart, 1984).
Of the variables examined only metal concentrations, mine density, site elevation, and
water temperature were significantly different between reference and mine-affected sites.
A Mann-Whitney t-test was used to evaluate statistical differences between reference and
test sites for physical and water quality parameters, while Spearman’s rank correlation matrices
were used to compare all possible response and explanatory variables. Lead concentrations were
significantly correlated with the number of mines in proximity to the watershed. Lead
concentrations in sediment and water were strongly correlated to Pb levels in whole caddisflies,
r 2 = 0.90 and 0.63, respectively. Furthermore, mine density was significantly correlated to Pb in
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