Modeling the mass balance and fate of copper in San Diego Bay

Abstract

Because of its presence in antifouling coatings, stormwater, and industrial and municipal discharges, copper is a ubiquitous contaminant in estuarine and coastal environments. We integrated a system-wide field program with a one-dimensional model to evaluate the overall mass balance of copper in a representative coastal harbor, San Diego Bay, California. Field results from four surveys over 1 yr showed remarkably similar distributions of total copper, with a general increase from the ocean into the Bay followed by a slight decrease in the inner Bay. Total copper concentrations ranged from 5 nmol L Ϫ1 to nearly 60 nmol L Ϫ1. Highest levels for both total and dissolved copper were observed during the winter. Results from a one-dimensional model accounting for the balance of sources, flushing, and losses to the sediment illustrated the importance of accounting for losses of copper to the sediment, without which water column concentrations are overestimated by as much as a factor of five. The time scale for the loss term is on the order of 8-10 d. The model reproduced the field measurements quite well with a loss term controlled by partitioning and settling parameters. The overall balance of total copper in the Bay appears to be split between losses to the ocean via tidal flushing and losses to the sediments via settling. Settling plays an important role in the fate of copper in the Bay, and the sediments are a key endpoint for copper.

Increased Bioavailability of Mercury in the Lagoons of Lomé, Togo: The Possible Role of Dredging

“…The Western lagoon also seems to experience less tidal flushing circulation with the coastal waters (hence the eutrophication events repeatedly observed), which takes place through a discharge channel that is longer for the Western lagoon when compared to the Eastern lagoon, and thus less exposed to fresh oceanic seawater input. As a result, lagoonal waters from the Western lagoon might have a greater residence time when compared to the Eastern lagoon, which might contribute to the observed differences (Chadwick and Largier 1999;Chadwick et al 2004).…”

Sediment Ecosystem Assessment Protocol (SEAP): An Accurate and Integrated Weight-of-Evidence Based System

“…Sediment at this station was very organic in nature, consisting of large masses of detrital material including twigs and leaves. This, in combination with the shallow depth (1.5-2.5 m) and high residence time expected from this tributary of San Diego Bay (Chadwick et al 2004) . It is also well established that marine polychaetes metabolize PAHs , facilitated by cytochrome 9-51 P450 enzyme induction, which may result in transformation of bioaccumulated PAHs to more soluble, excretable products.…”

The Role of Suspended Particles in Estuarine and Coastal Biogeochemistry

“…where k 1 is the sorption rate constant (l mg −1 d −1 ), k −1 the deso rption rate constant (d −1 ), w the particle settling velocity (m d −1 ), and h water column depth (m) (Chadwick et al, 2004). If…”

“…Values of k −1 in marine environ ments are in the range 0.12-0.43, 0.31-1.01, and 0.03-1.99 d −1 for Cu, Cd, and Zn, respectively (Wood et al, 1995;Chadwick et al, 2004). In the southern North Sea, with few exceptions, the maximum water depth is approximately 40 m. As particle set tling velocities are in the range <1-375 m d −1 (Tappin et al, 2008), then w/h < 0.025-9.4 d −1 .…”