Document Type

Technical Report

Publication Date



University of Washington: Department of Oceanography


The interstitial water chemistry of the sediments of Las Vegas Bay and Bonelli Bay in Lake Mead has been studied as part of a comprehensive water quality study of those locations. Pore water and solid phase analyses were completed from four stations in Las Vegas Bay and two stations in Bonelli Bay. At both locations the pore water compositions and organic matter diagenesis in the sediments are dominated by sulfate reduction. This major role of sulfate reduction is unusual for lake sediments and reflects the fact that SO4 is the major anion in the lake water. In addition, gypsum (CaSO4) is a common mineral in the surrounding geological formations and appears to supply additional SO4 to the interstitial waters through dissolution. The interstitial water and solid phase analyses have been used to calculate dissolved fluxes across the sediment-water interface. The average calculated PO4 flux out of the sediments was 1.3 mg P m-2 d-1 which is comparable with literature values of 1.2 to 9.6 mg P m-2 d-1 for aerobic water column conditions in rivers and lakes. The rate of burial of organic carbon averages about 6.2 kg m-2 yr-1. Our calculations suggest that this is about four times the loss due to decomposition of organic carbon by 02 and SO4. The extent of SO4 reduction was much more extensive in the sediments of Las Vegas Bay than Bonelli Bay and probably reflects a greater amount of utilizable organic carbon in the former observation.


Alkalinity; Bonelli Bay (Ariz.); Environmental monitoring; Lake Mead (Ariz. and Nev.); Las Vegas Bay (Nev.); Nitrogen; Ph; Phosphates; Sedimentation analysis; Sulfur dioxide; Water chemistry


Desert Ecology | Environmental Chemistry | Environmental Health and Protection | Environmental Indicators and Impact Assessment | Environmental Monitoring | Fresh Water Studies | Natural Resources and Conservation | Water Resource Management