Assessment of natural organic matter in Quabbin Reservoir

Quabbin Reservoir is a drinking water supply reservoir located in central Massachusetts. A study of natural organic matter (NOM) in Quabbin Reservoir was conducted using measures of total organic carbon (TOC), ultraviolet absorbance at 254 nm (UV-254), trihalomethane formation potential (THMFP), and apparent molecular weight distribution (AMWD) in Quabbin Reservoir and tributary waters. In general, NOM in Quabbin tributaries had elevated TOC, UV and THMFP, and different AMWDs as compared to Quabbin Reservoir. While distinct spatial (across the watershed) and temporal variations of NOM characteristics were observed in tributary inputs, the characteristics of reservoir NOM were relatively uniform with space and time. Measures of TOC, UV, THMFP and AMWD did not provide clear evidence of allochthonous and autochthonous NOM in the reservoir. One exception was the positive linear relationship observed between THMFP yield and blue-green algae density. Material balance analysis indicated that the net effect of waterbody processes on NOM inputs to the system was a reduction of 26% TOC, 71% UV-254 and 48% THMFP over a 2-year period, suggesting that waterbody processes differentially impact NOM characteristics.