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Water-Quality Trends From Lake Cores Active

By Water Resources Mission Area February 27, 2019

Sediment cores let us look back in time at the contaminant history of a watershed. Learn about what lake and reservoir sediment cores tell us about trends in metals, organochlorine pesticides, polycyclic aromatic hydrocarbons, and other sediment-related contaminants.

Lake coring in Lake Lanier, Georgia
Sources/Usage: Public Domain.
A hydrologic technician collects a core of lake sediment from Lake Lanier, Georgia.  By examining changes in contaminant concentrations from the top of the core (most recent sediment) to the bottom (oldest sediment), contaminant histories can be reconstructed.

Water-quality trends can provide an assessment of the effectiveness of regulatory actions aimed at improving water quality, a warning of water-quality degradation, and an improved understanding of how human activities affect water quality.  

Sediment cores—long tubes of mud—are collected from a lake or reservoir and sliced into thin intervals.  Each slice represents an interval of time. By analyzing the sediments in each slice for the contaminants of interest, changes in the occurrence of contaminants and their use in the watershed can be reconstructed. The approximate date corresponding to deposition of the sediment in each slice is determined by analysis of radionuclides (cesium-137 and lead-210).

USGS studies of reconstructed trends in metals and hydrophobic organic contaminants have shed light on the effectiveness of restrictions on the use of leaded gasoline, DDT, and PCBs, and the effectiveness of the Clean Air Act in reducing concentrations of some heavy metals.  The studies also have identified some contaminants, like polycyclic aromatic hydrocarbons (PAHs), whose concentrations are increasing in urban areas, spurring efforts to identify the source or sources of these upward trends.

Find out more about coal-tar-based sealcoat, a potent source of PAHs to lake and streambed sediment, and related environmental health issues. 

Examining sediment core
Sources/Usage: Public Domain.
Preparing to cut open a sediment core to release the overlying lake water.

NATIONAL SUMMARIES

TOPICAL FINDINGS

Lake sediment core sample
Sources/Usage: Public Domain.
Lake sediment core sample.  A sediment core can represent from a few to many decades of sediment, depending on the sedimentation rate of the lake or reservoir.

LOCAL RESULTS

Processing sediment core samples
Sources/Usage: Public Domain.
Sediment cores are sliced into intervals for chemical analysis.  Each slice of sediment represents a "slice" of time.

Read about additional science related to sediment-associated contaminants and water-quality trends by following the links to web pages below.

Learn more about water quality trends as recorded in sediment cores at the publications below.

Trends in hydrophobic organic contaminants in urban and reference lake sediments across the United States, 1970-2001

A shift in national policy toward stronger environmental protection began in the United States in about 1970. Conversely, urban land use, population, energy consumption, and vehicle use have increased greatly since then. To assess the effects of these changes on water quality, the U.S. Geological Survey used sediment cores to reconstruct water-quality histories for38 urban and reference lakes acro
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Water-quality trends using sediment cores from White Rock Lake, Dallas, Texas

The U.S. Geological Survey National Water-Quality Assessment (NAWQA) Program has three objectives, one of which is "to define trends (or lack of trends) in water quality" (Leahy and others, 1990). Water-quality trends are of interest for at least three reasons: First, trends can improve our understanding of the influence of human activities on water-quality conditions; second, trends can indicate
By
Water Resources Mission Area, Oklahoma-Texas Water Science Center

Water-quality trends in White Rock Creek Basin from 1912-1994 identified using sediment cores from White Rock Lake Reservoir, Dallas, Texas

Historical trends in selected water-quality variables from 1912 to 1994 in White Rock Creek Basin were identified by dated sediment cores from White Rock Lake. White Rock Lake is a 4.4-km2 reservoir filled in 1912 and located on the north side of Dallas, Texas, with a drainage area of 259 km2. Agriculture dominated land use in White Rock Creek Basin before about 1950. By 1990, 72% of the basin was

Historical trends in organochlorine compounds in river basins identified using sediment cores from reservoirs

This study used chemical analyses of dated sediment cores from reservoirs to define historical trends in water quality in the influent river basins. This work applies techniques from paleolimnology to reservoirs, and in the process, highlights differences between sediment-core interpretations for reservoirs and natural lakes. Sediment cores were collected from six reservoirs in the central and sou
By
Ecosystems Mission Area, Toxic Substances Hydrology, Environmental Health Program

Organochlorine compounds in a sediment core from Coralville reservoir, Iowa

No abstract available.
By
Water Resources Mission Area, Central Midwest Water Science Center

Concentrations of polycyclic aromatic hydrocarbons (PAHs) and major and trace elements in simulated rainfall runoff from parking lots, Austin, Texas, 2003

Samples of creek bed sediment collected near seal-coated parking lots in Austin, Texas, by the City of Austin during 2001–02 had unusually elevated concentrations of polycyclic aromatic hydrocarbons (PAHs). To investigate the possibility that PAHs from seal-coated parking lots might be transported to urban creeks, the U.S. Geological Survey, in cooperation with the City of Austin, sampled runoff a
By
Water Resources Mission Area, Oklahoma-Texas Water Science Center

Identification of water-quality trends using sediment cores from Dillon Reservoir, Summit County, Colorado

Since the construction of Dillon Reservoir, in Summit County, Colorado, in 1963, its drainage area has been the site of rapid urban development and the continued influence of historical mining. In an effort to assess changes in water quality within the drainage area, sediment cores were collected from Dillon Reservoir in 1997. The sediment cores were analyzed for pesticides, polychlorinated biphen
By
Water Resources Mission Area, Colorado Water Science Center