ENVIRONMENTAL CHEMISTRY OF A SNOW DISPOSAL SITE, BOSTON, MASSACHUSETTS

During the winter of 2014-2015, Boston received a record of 110.6 inches (2.81 meters) of snowfall. Roadside accumulations narrowed streets and buried sidewalks to the point that it had to be removed by truck and deposited in 11 “snow farms” to melt. The largest pile, at Tide Street in the Seaport District, was reported to have reached a thickness of 23 meters near the north end and an area of 16,000 square meters. Mixed with the snow was an array of refuse, soil, and pavement fragments. By July, following some periods of light rainfall and extensive melting, only a small core of ice was present under a mantle of refuse, surrounded by puddles in several areas of the paved surface. From the small remaining pile we collected eleven water samples from small active water flows, puddles on the ice surface and pavement, and drips off the ice surface. We also collected four soil samples from dried up puddles. We measured concentrations by ICP-OES for nineteen common cations in the water, by XRF for forty seven elements in the soil, and by ion chromatography for common cations and anions. Flow directions and puddle sources were estimated from Lidar data elevation data.

Drips from core ice had very low levels of all ions measured, close to that expected from rainwater. Some distal puddles were no longer connected directly to the ice and had elevated levels of calcium (24 and 38 mg/L) and sodium (10 and 50 mg/L), presumably from residual road deicers altered by rain flushing and evaporative concentration. These two samples generally had higher levels of elements such as boron, but were lowest in titanium and zinc. Among elements in the water with significant variation, iron correlated with zinc and titanium, and copper with zinc, and calcium with strontium and imperfectly with barium. Only lead and zinc were somewhat elevated in the soil samples relative to agricultural soils, but still well below common values in garden soil and compost in the Boston area. It seems certain that some dissolved elements may have been lost during melting and precipitation overflows into neighboring drains, so these results probably do not reflect the entire melting history of the pile.