IMPORTANCE OF SOIL-SURFACE WATER INTERACTIONS - MODERN TRANSPORT AND SEQUESTRATION OF HISTORICAL ARSENIC AND LEAD POLLUTION IN THE SHETUCKET, QUINEBAUG, AND YANTIC WATERSHEDS, CONNECTICUT (Invited Presentation)

The interaction between soils and surface water are important for governing transport of toxic metals. Soils play and integral role in sequestration by sorption while surface waters actively transport metals in dissolved or suspended phases. Thus, stability of soils and their physicochemical properties while active erosion and chemical properties of water can facilitate mobilization. To explore their relative importance, we will examine the Shetucket, Quinebaug, and Yantic rivers of The Thames River Watershed in Connecticut. These rivers have a historical legacy of trace metal contamination from mills, tanneries, manufacturing, and waste dumping. At ten different locations that span the headwaters to estuary of the Thames River watershed, water was collected from February to December 2019 and sediment traps were deployed. Moreover, thirty-four riparian soils were sampled using an auger down to 30cm at 5cm depth intervals. Mobility of trace metals was determined using a weak acid extraction and total concentrations in soils was measured using XRF. All stream water samples showed low As and Pb < 1 ng L-1 with significant variations among rivers and seasonally. Eddy sediments and suspended sediments showed higher concentrations of As and Pb than stream water samples. Riparian soils showed great variation of trace element concentrations throughout the watershed with urban soils sequestering non-mobile As and Pb, with mobile fraction at <1% of total concentrations. The more developed and stable soil profiles sequestered higher metal concentrations, highlighting the importance of riparian soil stability. These results show soil play an important sink in trace metals and while erosion and mobilization of metals by suspended sediments control transport.