AWRI Environmental Chemistry
Assessment of Contaminated Sediments in Mona Lake Watershed
Cooper, M.J., R.R. Rediske, D.G. Uzarski, and T.M. Burton. 2009. Sediment contamination and faunal communities in two subwatersheds of Mona Lake, Michigan. Journal of Environmental Quality. 38:1255-1265
A preliminary investigation of the nature and extent of sediment contamination in Little Black Creek, Cress Creek, and Mona Lake was performed that involved sediment chemistry and toxicity, ecological assessment, and metal transport modeling. Sediment chemistry and solid-phase toxicity were examined at 12 locations in Little Black Creek, 6 locations in Cress Creek, and 3 locations in Mona Lake. High levels of PAH compounds (40 – 60 mg/kg) were found in an area near Seaway Drive, downstream of Sherman/Getty culvert, and the stream reach between the Mona View wetlands and Airline Rd. Sediment toxicity also was observed at these locations. High levels of cadmium were found in the stream reach from
Peerless Plating (1,600 mg/kg) to the creek mouth at Mona Lake (11 mg/kg). Elevated levels of chromium, lead and zinc also were present. High mortality in both test organisms was observed near Peerless Plating (0-20% survival). Based on these results, the Little Black Creek system was found to be highly impacted by metals and PAH compounds. The Peerless Plating Superfund Site appears to be the source of most of the cadmium and chromium observed in the creek, although additional sources of metals are present near the Mona View Wetlands, Seaway Drive, and the Lower Wetlands.
Contaminated sediments were present in Mona Lake, with the basin near Little Black Creek containing higher concentrations of metals than Black Creek. Although the concentrations were above PEC levels, the only toxic response noted was a small reduction in midge growth in the basin near LBC. Sediment toxicity was not present in the station near the middle of the lake. Cress Creek was found to be an acceptable control site due to the absence of sediment toxicity.
A comparative assessment of the macroinvertebrate and fish populations in Little Black Creek was conducted using Cress Creek as a control site. Stream and wetland sites within each system were evaluated individually. The two sites were found to have similar water chemistry and physical characteristics. Nitrate, dissolved oxygen, and pH were slightly higher in Cress Creek while inorganic anions were higher in Little Black Creek. With respect to toxicants, Little Black Creek contained significantly higher levels of heavy metals and PAH compounds compared to Cress Creek. Taxon richness was higher in Cress Creek than LBC. In addition, higher densities of pollution sensitive Trichoptera and Plecoptera taxa were present in Cress Creek. The gradient in macroinvertebrate communities due to stream was more important than gradients related to either month or site, suggesting that anthropogenic disturbance associated with Little Black Creek substantially altered the macroinvertebrate community and these alterations overshadowed temporal and site-specific variability. The benthic macroinvertebrate fauna of Little Black Creek was found to be negatively impacted compared to the Cress Creek control site. The wetlands in both systems showed different trends with respect to physical and chemical parameters. Turbidity and sand size fraction sediments were greater in LBC while fine grained sediments and TOC were greater in Cress Creek. Toxicant levels (metals and PAH compounds) were significantly higher in the wetlands of Little Black Creek. Macroinvertebrate communities in the two systems appeared to respond more to substrate and turbidity than toxicant concentration.
A physically-based model was developed in this study for simulating metal (cadmium) and sediment transport in a coupled stream-wetland system that consisted of the water column, the underlying active bed, and the adjacent wetland subsystems. The model was tested by applying it to Little Black Creek. The simulated cadmium and sediment concentrations were compared against the observed ones and good agreement was achieved. The modeling results suggested that cadmium sorbed to the stream bed sediments was the primary source of cadmium contamination in the system. Resuspension of the cadmium-contaminated bed sediments played a critical role in the cadmium fate and transport. The modeling particularly emphasized the importance of the long-term, persistent cadmium accumulation process in Mona Lake and the wetlands, and the relevant threat to the ecosystem.
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