HYDROGEOCHEMISTRY COMPARISON OF A PRISTINE WATERSHED TO AN ANTHROPOGENICLY INFLUENCED WATERSHED

This research compares the hydrogeochemistry between two watersheds having very different land uses. The study areas are located in south-central Alaska and northwestern Missouri. The watershed of the Upper Matanuska River Valley, Alaska, is a sparsely populated area with minor recreational land uses. Local bedrock is highly fractured metasedimentary with felsic intrusions. Surficial deposits are glacial and glaciofluvial in origin and reflect the local bedrock. Conversely, the watershed of the One-hundred-two River Valley, Missouri, is a heavily agriculturalized area, with row crops and small livestock operations dominating the land use. In addition to agricultural land uses a few industries are also located within this watershed. Local bedrock consists of limestone and shale cyclothems. The area has surficial deposits of alluvium and till.

The objective of this study is to make a comparison of water quality between the watersheds in an attempt to quantify anthropogenic effects. Water quality was tested using an Inductively Coupled Plasma-Mass Spectrometer (ICP-MS), to measure concentrations of selected ions. Additional indicators of water quality that were measured include temperature, pH, dissolved oxygen, conductivity, salinity, phosphate, nitrate, and alkalinity.

Manganese proved to be the most complex of the ions selected for the study. Concentrations of Manganese in groundwater were approximately twice as great in Alaska as in Missouri, however, the One-hundred-two River had the highest concentrations of any water tested. The higher groundwater concentration in Alaska may be due to differences in bedrock. Elevated levels of Manganese in the One-hundred-two River is hypothesized to be site contamination from the effluent of either a water purification plant, or a dry cell battery industry, or both. Sample collection was within a half-mile of both industries. This hypothesis is justified by the use of manganese as an oxidizing agent in water treatment facilities and as a component of dry cell battery manufacturing. Anthropogenic inputs in this area directly influence the water quality.