Nutrient Inputs to Boston Harbor

Total nitrogen, total phosphorus, total suspended solids, and particulate organic carbon inputs to the harbor have declined by 82–95% since 1990–1991. Almost all those decreases can be accounted for by reductions in wastewater-associated discharges.

Total loadings of nutrients and solids to Boston Harbor, 1990-2007.
TN=total nigrogen, TP=total phosphorus, TSS=total suspended solids, POC=particulate organic carbon, Sludge=end of biosolids discharge, 1°=upgrade of primary treatment plant, 2°=implementation of secondary treatment, I-I=ending of discharge to the southern harbor with construction of the inter-island tunnel, OFF=ending of effluent discharge to the harbor with the commissioning of the new outfall.

Increases in the ratios of total nitrogen to total phosphorus and total suspended solids to particulate organic carbon show a shift in the dominant input away from sewage sources to rivers and other sources. Now, riverine inputs contribute most of the loadings of all the contaminants associated with eutrophication. Total nitrogen loadings to Boston Harbor are now lower than those in many other urban estuaries.

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