A PCB Sensor Suite for Monitoring the Effects of Annual Variations in Precipitation Rates on Alpine Lakes in Rocky Mountain National Park

Alpine Lakes are fragile ecosystems of immense beauty and value. They occur in high elevations and are often subjected to wide variations in annual precipitation rates. As such, their electrochemistry is affected by these annual variations in precipitation rates, which in turn, affects the entire ecosystem. Low-cost sensors for monitoring these changes will help in improving the management of these ecosystems. Low-cost Printed Circuit Board (PCB) sensors are being applied to many useful environmental and agricultural applications, including measuring soil moisture content, detecting pollution, monitoring drought conditions in estuaries, and monitoring for saltwater intrusion into coastal freshwater bodies. These sensors consist of a low-cost PCB with patterned Cu electrodes designed so that the circuit board electromagnetically interacts with the surrounding media, where its electrochemistry affects the measurable electrical impedance of the patterned traces. Exposed electrodes can be used to measure ion content in aqueous solutions from dissolved ionic compounds. Insulated electrodes can be used to measure moisture content of object and materials, or to identify dissolved ions in aqueous solution by searching for their relaxation frequency. In this multiyear study, a 2-layer PCB sensor suite consisting of a Au coated dual exposed electrode sensor on one side and a solder mask insulated interdigitated fringing field sensor on the opposite side is used. SMA connectors are attached to the opposite end of the sensor board for easy connection too instrumentation. The resistance of the exposed electrode sensor is measured using an Agilent 4192A LF Impedance Analyzer. The complex impedance of the fringing field sensor is measured using an Agilent E5061B Network Analyzer. For this study, PCB sensor technology is being investigated for monitoring the electrochemical properties of water samples from four alpine lake ecosystems in the Loch Vale Drainage at Rocky Mountain National Park. These alpine lakes are The Loch, Sky Pond, Andrews Tarn and Lake of Glass. Water samples were collected from these ecosystems in August of 2016, taken into the laboratory and tested with the PCB sensor suite to determine a baseline for the five year study.