海角禁区 grad student investigates the connection: volcanoes, lake trout and public health
by Keenan James Britt |
Residents of Southcentral Alaska have been preparing for the possible eruption of Mt. Spurr over the last few months, with concerns lingering about the effects of potential ashfall on local communities. Recent 海角禁区 alumnus Paul Gabriel, who defended his master鈥檚 thesis in geological sciences in April, is focused on another volcanic public health concern: mercury.
Originally from Wisconsin, Gabriel studied environmental science at the University of Wisconsin鈥揗adison where he gained experience examining water chemistry and nutrients in local lakes. After graduating from UW鈥揗adison, Gabriel relocated to Alaska to take a job with the National Park Service (NPS) monitoring water quality in Katmai National Park.
After seven years with NPS, Gabriel decided to pursue his master鈥檚 degree at 海角禁区, coming into the program with a thesis project already in mind. The project originated with an unsolved mystery from NPS about mercury levels in lake fish in Katmai National Park and Lake Clark National Park and Preserve.
鈥淸NPS] had this data set of fish mercury that had a lot of question marks about it 鈥� elevated levels really high in some lakes to the point where there鈥檚 health concerns,鈥� said Gabriel, who took up answering those questions with grant funding provided by the and the .
Sampling volcanic mercury in Katmai National Park
Gabriel hypothesized that the concentrations of mercury in lake fish were connected to the volcanoes in the two national parks. When volcanoes release trapped gas 鈥� a process known as outgassing 鈥� trace amounts of mercury (known as 鈥済aseous elemental mercury鈥� in this state) can be released as well.
The main chemical components of volcanic outgassing are water vapor, carbon dioxide and sulfur dioxide, though miniscule levels of mercury may be released depending on the volcano. Gabriel needed to sample outgassing from volcanoes within Katmai National Park in order to determine if they were responsible for releasing mercury into the environment.
Gabriel made trips to two volcanoes within Katmai National Park, Mt. Griggs and Novarupta, with an NPS team in order to measure mercury levels in outgassing using sophisticated equipment.
According to Gabriel, volcanic mercury has been understudied due to the miniscule concentrations in which it exists in outgassing.
鈥淲e're talking really tiny quantities. So it's really hard to measure and just even collecting it can be a challenge,鈥� Gabriel explained. 鈥淭here haven鈥檛 been the tools to just get an instantaneous reading. We had these sensors out for up to a week just to collect enough air to get a detectable amount of mercury.鈥�
Despite the technical and logistical challenges, Gabriel and the NPS team were able to detect gaseous elemental mercury from the volcanoes. 鈥淕enerally, the closer you are to the volcano, the higher the atmospheric concentration is,鈥� said Gabriel. 鈥淎nd then the assumption would be that it's also getting into the watershed at a higher rate.鈥�
Sampling mercury levels in lake trout
To confirm that volcanic mercury was precipitating out of the air and into local lakes, Gabriel took additional samples from lakes within the vicinity of the volcanoes via a beloved pastime of both Alaskans and Wisconsinites: fishing for lake trout.
鈥淚t鈥檚 a mix of hook and line, just going out and fishing like you would if you鈥檙e on your weekend and then also setting nets,鈥� Gabriel explained. 鈥淥ver the course of many years we've sampled more than a dozen lakes, and for each lake, you know, at least 20 fish. So I think we've sampled over 400 fish now for this project.鈥�
After catching the lake trout for sampling, the fish would be 鈥渟acrificed鈥� and filleted. Samples taken from the fillets were then sent for analysis to a U.S. Geological Survey Mercury Research Laboratory in Gabriel鈥檚 home state of Wisconsin.
The results confirmed that lakes closer to the volcanoes showed higher levels of mercury in the lake trout samples. The practical implications for public health were clear, especially for subsistence users and sport fishing enthusiasts fishing on the lakes.
鈥淧eople subsist on these lakes and they subsist on these fish. So there's a big human health component to it,鈥� Gabriel said. 鈥淎 lot of people go to Katmai for angling, right? It's a very big thing out there. So we would say, you know, maybe only eat one fish out of this lake a year, or just don't eat them all year if you're working out there.鈥�
