Nutrients and Heavy Metals Contamination in an Urban Estuary of Northern New Jersey

Hun Jung

doi:10.3390/geosciences7040108

Abstract

The Newark Bay Estuary in northern New Jersey contains one of the largest urban wetland complexes in the United States, but the majority of the wetlands and habitats have been lost due to urbanization and industrialization. Field and laboratory research was conducted to understand the impacts of human activities on the biogeochemistry of nutrients and heavy metals in the urban estuary. Concentrations of dissolved nutrients such as nitrate, ammonia, and phosphate were higher in the Hackensack River than in the Passaic River or the Newark Bay, while the Hackensack River was more deficient in dissolved oxygen. Sediment oxygen demand and mobilization of nutrients were higher in sediments with higher organic matter content as a result of microbial decomposition of organic matter. Heavy metals (Cr, Cu, Pb, and Zn) and organic matter were more enriched in finer sediment grains such as silt and clay. There were positive correlations among heavy metals as well as organic matter in sediments. The results suggest that fine grained sediments, which can be readily suspended and transported during tidal cycles, may play a significant role in biogeochemical cycling of nutrients and heavy metals in the urban estuary. It appears that the current sources of nutrients and heavy metals in the water and sediment of the Newark Bay Estuary are mainly domestic effluents from sewage treatment plants during non-storm periods as well as combined sewer overflows during storm events, but further research including more frequent and pervasive water and sediment quality monitoring during dry and wet periods is needed.

Highlights

Estuaries are zones of biogeochemical and biological mixing and are considered to be one of the most highly productive ecosystems [1]
It should be noted that water samples were collected from the Hackensack River during the transition from high tide to low tide, whereas water samples were collected from the Passaic River during the transition from low tide to high tide (Table 1)
Different tidal levels could have affected the electrical conductivity of two tidal rivers in summer 2016, the ion chromatography data for water samples collected from both rivers during the transition from low tide to high tide in summer demonstrate that the Hackensack River is more saline than the Passaic River (Table 2)

Summary

Introduction

Estuaries are zones of biogeochemical and biological mixing and are considered to be one of the most highly productive ecosystems [1]. Estuarine wetlands combine chemical transformation and transport processes in the biogeochemical cycling of nutrients and trace metals [2]. Prolonged periods of excess nutrients may lead to unsustainable primary production and eutrophication. Toxic trace metals such as arsenic, copper, and lead may have complex effects on primary and secondary production in estuarine systems [3]. The urban estuary is located in the heavily industrialized and densely populated New York–Newark–Jersey City metropolitan area. The coastal and marine waters of the estuary were known to support diverse populations of fish and shellfish, but the metropolitan region surrounding the urban estuary has been heavily impacted by both industrial and municipal activities [5].

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