Fate and Transport of Hydrophobic Organic Chemicals in the Lower Passaic River: Insights from 2,3,7,8-Tetrachlorodibenzo-p-Dioxin

Abstract

The fate and transport of hydrophobic organic chemicals (HOCs) is particularly complex in estuaries because of bidirectional longitudinal currents, density stratification, the tendency to trap sediments, and significant dilution in the downstream bay or ocean. Investigations of HOCs in estuaries are further complicated because HOCs typically enter from multiple sources. The distribution of contaminants in estuarine sediment beds reflect a time integration of a complex balance of time-and space-variable fate and transport processes and loading history. A unique opportunity to study HOC fate and transport exists in the Lower Passaic River (LPR), where a pesticide manufacturer was the dominant source of 2, 3,7,3,7, to the estuary and the distribution of this "tracer of opportunity" provides insights about fate and transport processes in estuarine systems. This paper presents observed sediment 2,3,7,8-TCDD patterns within the LPR and the adjacent Newark Bay, and interprets them in terms of fate and transport processes that likely distributed the contaminant from its dominant source, drawing upon other physical datasets as needed. Major observations include that estuarine transport processes have distributed 2,3,7,8-TCDD approximately 18 km upstream of the source and downstream across Newark Bay, and that, generally, HOC trapping processes within the LPR have been highly effective, particularly near the 2,3,7,8-TCDD source and in downstream areas. The present LPR surface sediment 2,3,7,8-TCDD distribution indicates spatially variable recovery, which appears broadly driven by historical net sedimentation patterns, though the dominant processes may be shifting as the system continues to evolve.

Fingerprinting 2,3,7,8‐tetrachlorodibenzodioxin contamination within the lower Passaic River

“…The slightly higher proportion of 2,3,7,8-TCDD observed in the RM 14 to RM 17.4 bin (relative to upstream) suggests some site influence on this region. This is consistent with the physical understanding of the system, which indicates that transport associated with tidal resuspension and salinity intrusion would have moved contaminants from the site upstream 23,46. As discussed in Chant et al 46 and Israelsson et al 23, during low-flow conditions, a net upstream transport of solids is observed within the estuarine portion of the lower Passaic River, attributable to the estuarine circulation and tidal pumping.…”

“…This is consistent with the physical understanding of the system, which indicates that transport associated with tidal resuspension and salinity intrusion would have moved contaminants from the site upstream 23,46. As discussed in Chant et al 46 and Israelsson et al 23, during low-flow conditions, a net upstream transport of solids is observed within the estuarine portion of the lower Passaic River, attributable to the estuarine circulation and tidal pumping. Although the salt front typically resides in the lower 8 miles of the lower Passaic River, it can extend above RM 14 under extreme, persistent low-flow conditions (such as those experienced during the drought conditions in the mid-1960s).…”

“…The match strongly indicates that the Lister Avenue site is the dominant source of the examined PCDD/Fs over this region. The upstream influence of the site, which extends to approximately RM 14 (congener ratios indicate a gradually declining influence over the RM 13–15 interval in particular), is consistent with upstream contaminant transport and salinity intrusion considerations, particularly during the peak site discharge period 19,23.…”

“…Although the salt front typically resides in the lower 8 miles of the lower Passaic River, it can extend above RM 14 under extreme, persistent low-flow conditions (such as those experienced during the drought conditions in the mid-1960s). The upstream solids transport implies an upstream contaminant transport that is consistent with the lower Passaic River sediment data patterns, and moreover, net upstream contaminant transport is plausible above the salt front in the presence of longitudinal gradients in contaminant concentration (see Israelsson et al 23 for additional discussion).…”

“…In 2004, a remedial investigation and feasibility study for Newark Bay, including portions of the Hackensack River, Arthur Kill, and Kill Van Kull, was initiated. Sediment chemistry data from the Passaic River and Newark Bay studies indicate that 2,3,7,8-TCDD is present within the lower Passaic River at levels that are much higher than those found in other regional sediments (i.e., those in the Passaic River above the Dundee Dam, in lower Passaic River tributaries, and in Newark Bay [23]). In 2012, Occidental Chemical and Tierra Solutions removed approximately 40 000 cubic yards of lower Passaic River sediments containing 2,3,7,8-TCDD levels as high as 35 mg/kg from the immediate vicinity of the site (i.e., the phase 1 removal area shown in Supplemental Data, Figure S1).…”