ISSN:
1440-1770
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Geography
Notes:
This paper examines the hypothesis that the spatial pattern of metal accumulation rates in inland lake sediments provides insight into the causes of the historical and continued loadings of contaminants to the environment. To address this, copper and lead accumulation rates in the Great Lakes' watershed were studied. A multi-element approach was used, in which many non-toxic chemicals were measured along with the toxic chemicals of interest, rather than a target-specific approach. The multi-element approach also allowed for assessing the environmental state of the lake with respect to its surrounding watershed. Sediment cores were collected from the deepest portion of five Michigan inland lakes, sectioned, metals extracted by nitric acid, microwave digestion and leachates analysed for 26 metals using an inductively coupled, plasma, mass spectrometer with hexapole technology. Sedimentation rates, ages and focusing factors were calculated via 210Pb. Dasymetric mapping was used to estimate population distributions in lake watersheds. Watershed area was estimated from digital elevation data using Arc/INFO (ESRI, Redlands, California). The data show that as loadings from dominant (regional) sources decrease (e.g. atmospheric deposition in the case of lead), new patterns provide insight into causes for continued contaminant loadings (e.g. population density). The data also show the universal response of the watersheds to the onset of the anthropogenic loadings of lead but not that of copper. Individual watersheds had different onset times for anthropogenic copper loadings. Recent lead loadings to the environment can be related to population density, and those of copper reflect, in part, a spatial pattern that is similar to the regional pattern for lead during the mid-1970s. As this pattern for lead could be related to a regional gradient of lead concentrations in atmospheric deposition, the same relation cannot be made for copper. The cause for this spatial pattern for copper is not clear.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1046/j.1440-1770.2002.00190.x
