Now a few weeks ago, two professors from Lamont, Dallas Abbott and William (Bill) Menke, took me out on kayaks, so I could deploy my particle size analyzer (the Laser In-Situ Scattering and Transmissometry Particle Size Analyzer from before, LISST for short)
in the Hudson. I’ve become very interested in the particle dynamics in the Hudson, as we know that combined sewer overflows (CSOs) release very turbid (particle heavy) flows when sewage is discharged. While taking the LISST out gives us information on what kind of particles are in the river, we also need to know what kind of microbes are attached to these particles and how we can track turbid plumes (water masses with high amounts of particles) to understand the transport of contaminants from CSOs. Currently, I’m advising an undergraduate on how to answer the first question, while I’m tackling the second question in a separate project. Check back here or on Twitter for answers to those questions!
The day looked to be nice, sunshine and comfortably warm temperatures, on the Friday that we decided to go out. In preparation, I rigged the LISST to dangle between two pontoons, allowing it to sink into the water column, but not very far. Because I’ll be looking at transport of particles via satellite, I know I need more information on the conditions in the surface water. Satellites aren’t able to capture signals much below the surface, so the in-situ (in the water) data I can compare with satellite data has to be from relatively shallow water. At the same time, we want the LISST to stay in the water column, despite any waves. The ring receptor captures light scattered from particles and exposing that sensitive receptor to sunshine would skew results and potentially damage the instrument.
Unfortunately, when we got out onto the water, we realized there was a lot more chop
(i.e. rougher water) than we had expected. Adding to the rough water was the heavy LISST, which was attached to the back of the kayak that Dallas and I were using. We paddled hard to keep away from the shoreline, which seemed magnetic. Despite my foot heavy on the rudder, the waves billowing towards shore kept knocking our kayak closer and closer to the beach and partially hidden rocks. I resorted to intentional yoga breathing with each stroke to give as much power to my motions, but it seemed to do little other than distract me from how hard we were working and how little we had to show for it.
Before we rounded Piermont Pier, Bill came over to us in his solo kayak, noting that our rudder was tangled up in the towing rope for the LISST. He began to untangle us, eventually removing the LISST briefly from our boat. At this moment, we realized how incredibly close we were to the coastline and Bill advised us to paddle away. Dallas and I turned our kayak and, with the sudden lightness and restored steering capabilities of our kayak, rocketed out into a much safer region. Bill followed after, though notably slowed down by the LISST and its rig. As he paddled towards us, we confirmed what I had suspected earlier: the LISST had not been dragging through the water like a torpedo – it had been dragging like an anchor. Twisting horizontally in the rough water, the LISST and its rig had become a highly inefficient package for towing.
Bill reattached the LISST to our boat, adjusting the towing line to avoid tangling our rudder and to encourage the LISST to flow straight behind us. At his encouragement (Dallas and I were both pretty tired and concerned about towing the LISST more by this point!), we decided to continue on our journey and at least make it around Piermont Pier. When our boat finally caught up with Bill, we decided we had to adjust the LISST again, because it was still towing inefficiently. Ever ingenious Bill began moving the LISST, so it could be propped on top of our kayak with the sensor end sticking into the water. Though this meant the LISST was protruding into the path of my natural paddle stroke, we no longer had an anchor. During this “pit stop,” Bill’s paddle floated away and one of the pins from the pontoon met a watery grave. By the time we collected Bill’s paddle, I had begun thinking what would happen if we just stopped paddling and let the water take us. Eventually we’d find land. And maybe even Manhattan.
Even if we were exhausted, we had to make our way back our docking area. We set our sights on that dock and doggedly paddled our way back. Crossing to the other side of the pier, we encountered strong waves again – waves that would roll over the kayak, soaking me to my waist. Strangely, these waves reawakened my sense of adventure and brightened my mood. While the last leg of the journey was difficult, it fell into the “delightfully challenging” category.
Three hours after we set out, we pulled up to the dock and hopped into the river to pull the LISST from the water and get our boats onto the dock. Dallas and I docked first and, while I shielded the UV sensitive portion of the LISST and stopped my GPS track, Dallas gathered our various items and made room for Bill to dock. Adding to our comedy of errors were a last minute canoe flip that cooled Bill off, a D-ring falling through the slats of the dock into the river (which was rescued through team fishing by Bill and I), and a forgetful graduate student (I wonder who) leaving our rope behind. At this point, we were all exhausted and ready to pack up the cars and head out.
The generosity of both Bill and Dallas extended even further, as they had me over for dinner and Dallas drove me to pick up the rope, drop off the LISST in the office, and then back into Manhattan. At their house, I washed off the salty water from the LISST and pontoon supplies (minus the abandoned pin) before toweling off the LISST and bringing it into the house. Dallas remarked that in true scientist fashion, I offloaded the data before showering/eating/drinking/resting.
Unfortunately, the LISST doesn’t have preprogrammed software that lets you view the data immediately. The week after we went out, I spent a chunk of time devising a MATLAB script (soon to also be in Python and R) to convert the data, combine it with time series GPS data, and generate a variety data plots. The goal is that, the next time we go out, I’ll be able to just change our initial conditions (time start/stop, file name) and then press run. We’ll see how well that goes! For now, you can see the plot of the sizes of particles we encountered and the total amount of particles along our trek. (As a caveat, there is a bit of fudging of GPS location during the few minutes where Bill had the LISST while Dallas and I paddled away from shore, since the GPS was in my pocket.) As you might expect, we found our highest concentrations of particles where we were docking, because the shallow waters allowed for lots of resuspension of sediment.
At the end of our evening, we had a TexMex feast while we chatted about everything from science in policy to their recent trip to Maine. Though we had a successful outing, we all agreed that the next time we took out the LISST, we needed a much bigger, motor-powered boat!