HAMBURG COVE, CT: SEDIMENT CORES REVEAL 20TH AND 21ST CENTURY “LEGACY” POLLUTION

Hamburg Cove, CT, is located near the mouth of the Connecticut River and has a daily tidal influx that brings in marine waters from the Long Island Sound. Its sediments contain high levels of inorganic mercury, among other pollutants, due to 20^th century industrialization. The toxicity of the mercury in the cove is significantly increased once it is methylated by bacteria, because methylmercury easily bioaccumulates up the food chain. Past work has correlated higher levels of mercury methylation with more brackish water brought in from tidal influx. These higher methylation levels were attributed to the higher sulfate levels in the water leading to more sulfate reducing bacteria (SRB) activity. However, there are many controls on mercury concentrations and methylation rates, one being the “type/quality” of organic matter (OM) in the sediment. In this study we examine 3 sediment cores representing a range of tidal influence in the cove. These span the “endmembers”- a freshwater site (HFW) and the site where salt water accumulates (HMB) as well as a core taken at a likely brackish site (HSR).

Total organic matter as determined on an elemental analyzer shows Using mercury profiles to date the sedimentation we found that the HSR site had a lower sedimentation rate and a lower total mercury content than the HFW site (0.4 cm/yr compared with 0.6 cm/yr; and 221 ppb to 510 ppb, respectively). Furthermore, using the iTRAX XRF core scanner we identified increases in potassium, iron, and titanium in the section of the core that corresponds to the mid-eighteenth century, when fertile land was becoming scarce due to the extensive expansion of agriculture in the Connecticut River Colony. This increase in K, Fe, and Ti may be indicative of the massive erosion occurring at that time due to the clearing of entire forests. There is also an increase in zinc (as well as mercury) beginning around the 1890’s which can be attributed to the Industrial Revolution.