By Christine A. Waters
I told myself I wouldn’t have to do this anymore. Whaaaat am I doing here?” As the sun beat down on us mercilessly, I played through memories: the incisive friction of Kevlar antennas and tie-downs tearing from my grip in the Chihuahuan Desert under gusts of wind, the swelling cramps in my neck and lower back from carrying 40 lb rucksacks full of gear through twelve miles of coniferous forest in Georgia, and the sweltering heat of Nuclear/Biological/Chemical contamination suit and mask training during monsoon season in Korea. The discomfort of my sunburn was magnified by those memories. Oh, shade! Oh, sundown!
Our ten-foot inflatable raft wafted up-and-down in the gentle, rolling waves of Kiholo Bay, off the west side of the Island of Hawaii. We were trolling along the shore, surveying waters along the coastline for radon. “Radon?” you say. “Affirmative, radon – the very same one that causes lung cancer when breathed.” Radon is enriched in groundwater from our islands, relative to the ocean (that is), and so we look for it and measure it and use its concentrations at sites (along with salinity, temperature, nutrient and chlorophyll-a concentrations) to tell us where and how groundwater is affecting the coastal zone. In areas like Kiholo Bay, this frying pan where I was currently baking, groundwater is the primary conveyor of nutrients and contaminants to the ocean. So, we survey nature’s bug juice.
A Hawaiian green sea turtle glides up to the raft and checks us out for a minute. (“Us” are a group of three: two undergraduates and me, a grad team chief, Jane-of-all-trades.) What makes the water do? Well, that’s what I imagine the turtle thinks in passing. This type of thinking helps me get the job done. Soon, we are finished – but not with the day. It is just lunchtime. As I throw on a coverall to protect the few remaining bits of my hide that aren’t lobster pink, we hastily get the raft ready for a new operation. Today’s special for lunch will be: wet crackers, salty cheese with bits of sand, some grapes (who doesn’t like grapes?), and don’t forget to drink water! Our dining facility is the raft, as we’re motoring out to the location of our first radium sample, past the reef, in the middle of the bay. Radium analyses, I will explain in a bit. For now, soldier, we are collecting water samples, and this is a need-to-know kind of job!
“Don’t look at my butt!” my undergrad (unofficial rank = specialist) yells, as she leans over the side of the raft to begin filling our 20 L cubitainer with water. (This is almost always the comment that is made by the poor battle buddy grabbing the sample.) And as we try to hold the raft in position with the oars, the afternoon’s typically choppy tide is beginning to fight with us. Oh no, you don’t! Beat your face, Water! The ocean does not assume the front-leaning position. I am not pleased.
Nonetheless, we are successful! Sample obtained and water quality parameters (salinity, temperature, pH, dissolved oxygen) recorded, we return to the shore to dump it into… a trash can. Ah, science is glamorous! Since there is so little radium in the ocean, we need to collect large volumes of it for measurement. We collect ~60 L of sample.
Radium is a radioactive, daughter product of thorium. Thorium likes to attach itself to particles, is very immobile, and is relatively deplete in ocean waters compared to those originating from land. Thus, little radium is measured on the ocean surface relative to the amount of radium we measure in rivers, lakes (or other bodies with shallow sediments), and groundwater. Radium attaches to particles in freshwater. Where freshwater meets saltwater, it begins to be replaced by chloride from the saltwater, and so it falls off of particles (and into the ocean water). This new supply (compared to the low ocean concentration) is what we’re actively looking for in the waters we sample.
Because radium is radioactive, it decays. So, we can use the radium that lives for the shortest time period to constrain how long the water we’ve sampled has been in nearshore waters and how much mixing with ocean water is taking place. This will be important for identifying things like: how long do groundwater-supplied nutrients stay in an area or how long does contamination persist in recreational waters, et cetera. In the lightest of sense, someday, soldiers in survival training will be forced to tread water in their ACUs in this stuff, and we want to make sure we know what quality of water they’re sucking up – but also how many and how well the phytoplankton (at the bottom of the food chain) are growing around them in the eight hours they’re doggie-paddling.
Trashcans lined up on the basalt, pebble beach, waiting for 60 L water samples for radium filtration at Kiholo Bay in Hawaii. On the shore, you can see the “Little, Little Bad”… just chillin’. Photo by Joseph Kennedy, 2010.
After eight radium trash cans are filled and filtered (Oh yes, there’s filtering!), we’re ready to roll-out for the day. The sun is setting, and the sky is a beautiful orange, pink, purple, and grey. Hurray! The white tern that is often at Kiholo Bay in the evening eyeballs us from his rock. It’s okay, tern. We’ll see you tomorrow! And tomorrow, I’ll wear long sleeves and sunscreen to the battle. With all the talking that goes on in my head, I wonder at the evidence we’ll discover in this place for groundwater’s impact on the nearshore environment and the coastal ecosystem. On top of this, I wish I could give the world a better answer for why I’m still here. But the truth is, given all my training and history, I really just enjoy this dialogue that’s happening. 😉
Christine A. Waters is a veteran of the United States Army and a third-year graduate student in the Marine Geology section of the Geology and Geophysics Department. She is working with, advisor, Dr. Henrieta Dulaiova, on submarine groundwater discharges off the Kona Coast of Hawaii.