CHEMICAL VARIATIONS IN WATER QUALITY IN A SMALL STREAM DOWN FLOW FROM A DEICER STORAGE FACILITY

In an effort to evaluate the impact of dissolved deicer chemicals on water quality, we setup a 2-probe configuration to track stream water quality variations with one probe positioned at the bottom of the stream to monitor local baseflow discharge and the second probe 22.6 centimeters above the first one to monitor water quality of the main streamflow. A pair of AquaTroll 200 probes were placed in the center of the stream (42.3231, -71.3239) located downstream from a large deicer storage facility and are set to record at 15 min intervals data on water pressure, temperature, and specific conductivity, the latter calibrated to yield concentrations of NaCl. The contributing drainage area is a 7.79 km² subcatchment of the Charles River drainage basin in Eastern Massachusetts in a generally suburban residential setting. Each probe was lowered into a PVC pipe; the bottom of the PVC pipe of the near-bottom probe is open to stream seepage inflow (baseflow) while the PVC pipe of the upper probe has side openings to the stream to track water quality of the main throughflow. Stream water level occasionally drops below the sensor levels in the upper probe during the summer months, while the lower probe records data at all times. For the time periods when both probes were recording data there is a consistent, though not constant, difference in the deicer concentrations recorded by the probes. The near-bottom probe measures higher deicer concentrations that are as much as 20% higher than deicer concentrations measured within the main flow. During precipitation events the upper probe measures noticeably lower deicer concentrations as the stream flow gets progressively more diluted by the overland flow. In conclusion, it is important to note that inhomogeneities in dissolved deicer concentrations in the streams may not give the correct information in regards to the deicer concentrations and may not accurately represent the deicer dissolved loads.