WATER AND SEDIMENT QUALITY OF URBAN RIVERS IN NEW JERSEY

Passaic River, Hackensack River, and Newark Bay in New Jersey have been heavily impacted by both industrialization and urbanization for more than two centuries. Water and riverbed sediment samples were collected from the tidal section of the Passaic River (n=8) and Hackensack River (n=9), as well as Newark Bay (n=3) in the summer of 2015. Water samples were analyzed for pH, electrical conductivity (EC), dissolved oxygen (DO), nitrate, ammonia, phosphate, and chloride in the field using CHEMetrics test kits and Hach DR/890 Colorimeter. Both rivers are characterized with slightly alkaline pH (average 7.9) and a sufficient level of DO (average 6-7 mg/L). The EC and chloride concentrations were significantly higher for the Hackensack River (1.21-23.30 ms/cm and 280-7000 mg/L) than Passaic River (0.59-1.54 ms/cm and 90-360 mg/L), indicating that tidal water can intrude further upstream through the Hackensack River than the Passaic River. Average nitrate concentration was higher in the Passaic River (4.6 mg/L) than the Hackensack River (2.8 mg/L), while average ammonia and phosphate concentrations were higher in the Hackensack River (0.80 mg/L and 1.42 mg/L) than the Passaic River (0.10 mg/L and 0.73 mg/L). The Newark Bay is characterized with high EC (average 29.4 ms/cm) and chloride concentration (average 7700 mg/L), circumneutral pH (average 7.5), high level of DO (average 8 mg/L), and low concentrations of nitrate, ammonia, and phosphate (average 0.7 mg/L, 0.30 mg/L, and 0.59 mg/L).

Organic matter content of riverbed sediments determined by Loss-on-Ignition was on average 6.2 wt% for the Passaic River and 7.0 wt% for the Hackensack River, while sediments from Newark Bay contained significantly lower amounts of organic matter (average 1.9 wt%). Sediment oxygen demand experiments showed that a significant depletion of dissolved oxygen (8 mg/L to 2-3 mg/L) was associated with a high amount of sediment organic matter. The field and laboratory results indicate that Passaic River and Hackensack River pose little concern regarding general water quality including pH, DO, and nutrients. However organic rich river bed sediment may deplete dissolved oxygen and cause environmental damage to aquatic ecosystems in the urban rivers.