An Investigation of the Inorganic Geochemistry and Drinking Water Quality of Groundwater in St. Lawrence County, New York
Michael O’Connor, Dr. Jeff Chiarenzelli, Carol Cady
- Areas not covered in previous research (Zabik 2007) were of high priority.
- A random surveying technique was utilized.
- Water was run for at least 2 minutes before collection in pre-cleaned 125-mL Wheaton Cleanpack® sample containers and then put in a cooler to avoid contamination.
- Thirteen additional samples were collected in pre-cleaned 500-mL Wheaton Cleanpack® sample containers for Sr isotope analysis.
- GPS coordinates were taken at each sample locality and temperature and pH measurements were taken in the field when a pH meter was available.
- Homeowners completed a short survey which included any information on the well that could be provided.
- Seventy-two inorganic elements were analyzed by Inductively Coupled Plasma – Mass Spectrometry (ICP-MS) at ACME Analytical Laboratories in Vancouver, B.C.
- Two duplicate samples and two blanks were also analyzed to ensure data accuracy.
- The thirteen samples collected in the 500-mL containers underwent Strontium isotopic analysis on a Trition TI mass spectrometer at Carleton University in Ottawa, ON
- Water sample data was added to an ArcGIS geodatabase.
- Using Kriging Interpolation, maps showing element concentration trends have been modeled for groundwater in St. Lawrence County.
- Kriging layers produced have been superimposed onto a St. Lawrence County generalized bedrock geology layer.
- Ultimate product is a geodatabase with St. Lawrence County water quality data accessible to county officials
- Major Elements (> 10,000 ppb) for the 176 samples are Ca, Cl, Mg, Na, and S
- Minor Elements (100 – 10,000 ppb) for the 176 samples are K, Si, and Sr.
- Trace Elements (10 – 100 ppb) for the 176 samples are B, Ba, Br, Cu, Fe, Mn, and Zn
- Comparing the element concentration data for the 176 groundwater samples to the Environmental Protection Agency’s (EPA) primary drinking water standards, one sample exceeded the EPA standard for Arsenic.
- Comparing the element concentration data for the 176 groundwater samples to the EPA’s secondary drinking water standards (concerned with water aesthetics), thirty samples exceeded secondary standard concentration levels: Al (n = 1), Cl (n = 7), Cu (n = 5), Fe (n = 1), Mn (n = 10), and TDS (n = 6).
- Total Dissolved Solids (TDS) ranged from 13 ppm (undivided metamorphic rock and related migmatite ) to 1259 ppm (biotite-quartz-plagioclase paragneiss, amphibolite, and related).
- 87Sr/86Sr ratios for the 12 analyzed groundwater samples varied from .709000 (Beekmantown Group) to .715468 (Quartz-feldspar paragneiss, commonly leucogranitic.). There is an observable contrast between 87Sr/86Sr ratios from Paleozoic rock sources and Precambrian rock sources (see chart).
- Kriging analyses of various element concentrations for the 176 groundwater samples (Zn, As, and B included) show distinctive concentration trends which imply bedrock influence on groundwater geochemistry.
Multi-element analysis of 176 groundwater samples from private wells throughout St. Lawrence County suggests that the underlying bedrock is influencing the groundwater geochemistry. Elevated zinc concentrations are notable near two known zinc mines: the Balmat zinc mine and the inactive West Pierrepont zinc mine. Elevated arsenic concentrations appear to be focused in the Paleozoic rock units, especially close to the Paleozoic-Precambrian contact zone. The well sample that exceeded the EPA primary standard for As is located in close proximity to this contact. Additionally, pyrite deposits are known in the area and may provide an As source. Elevated boron concentrations are notable at Power’s Farm which has world-renowned black tourmaline (uvite) deposits, and in other regions that also possess tourmaline deposits suggesting that the mineral is interacting with the groundwater and influencing its geochemistry. Furthermore, other element concentration trends such as elevated B, Br, Li, and Sr in dolostones with evaporitic layers, and the abundance of Ca and Mg in groundwater derived from marble and dolostones which underlie large areas of the county further imply the influence of bedrock on the groundwater geochemistry.
Although only one sample exceeded EPA primary drinking water standards in this study (As) and thirty samples exceeded EPA secondary (aesthetic) drinking water standards, the study is important in terms of health aspects as this database will be accessible to county planners for use in future groundwater well development. Observable bedrock-influenced groundwater element concentration trends can be used to deter or encourage future well drilling in specific areas. Furthermore, future sampling and further analysis along with GIS interpolation could increase the precision of current results and increase its validity for county planners.