HEAVY METAL CONTAMINATION OF STONY BROOK, WESTFORD, MA

Westford, MA has a history of industrial activity dating back to Stony Brook Railroad construction (1847). This study focuses on a site of interest (SOI) along Stony Brook: Westford Anodizing Corporation (EPA ID MAD062173497), Rustlick Industries (EPA ID MAD985276351), and the location of a train derailment (EPA ID MAN000100110). All three were reported to have released hazardous materials, were classified as Superfund sites, and are ~500 m upstream of a public drinking water well and conservation area. While cleanup efforts have occurred, research into the distribution of heavy metals (HMs) and their possible negative effects on the fluvial ecosystem is lacking.

Surface sediment grab samples (n=29) were taken in three distinct areas: up to 500 meters upstream of the SOI, within 100m downstream of the SOI, and between 100-4000m downstream of the SOI. Dried and homogenized samples were analyzed using a Niton XL5 Plus handheld XRF, and results show low concentrations of Pb, As, Ni, Cu, Zn, and Cr upstream, significantly higher concentrations at and around the SOI and a gradient to lower concentrations further downstream. ANOVA and Tukey’s post hoc tests support this, with p ≤ 0.03 between SOI and upstream and SOI and downstream, and p ≥ 0.2 between upstream and downstream. This suggests that elevated metal concentrations are a result of a point source at the SOI. Maximum concentrations of all HMs occurred within 100m downstream of the SOIs: As = 233±10, Cr =484±29, Ni = 518±42, Zn = 701±18, Cu = 971±33, Pb = 1637±27 ppm.

Freshwater probable effects concentration (PEC) sediment quality guidelines (MacDonald et al, 2000) predict concentrations at which it is probable that adverse ecological effects will occur. Of the grab samples, 72% exceed the As PEC, 17% Cr, 7% Cu, 31% Ni, 34% Pb, and 7% Zn.

As and Zn are the only two HMs of interest that correlate significantly with distance from SOI from 0 – 500 m downstream (r ≤ -0.7, p=0.02); these are the two HMs with the lowest partition coefficients (Kd = 3.6 and 3.7, respectively). This result suggests that As and Zn travel downstream more readily than the other HMs (Cu, Cr, Ni, Pb) which adsorb more strongly to the sediments at the SOI and are largely sequestered in these sediments.

Ongoing analysis of gravity cores (n=4) will aid in understanding the temporal distribution of HMs.