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Geology topics

R.A. Cahill

Publications and source records attributed to R.A. Cahill.

11 recordsLinked to original sources
USGS2005

Sediment quality and quantity issues related to the restoration of backwater lakes along the Illinois River waterway

Sedimentation has severely impacted backwater lakes along the Illinois River. The State of Illinois and the US Army Corps of Engineers are currently involved in a joint effort to address ecosystem degradation within the Illinois River Basin, and excessive sedimentation of backwater lakes and side channels is a primary cause of that degradation. Necessary parts of the overall restoration effort are to adequately characterize both the quality and quantity of backwater lake sediments prior to implementing any restoration efforts, and to identify potential beneficial reuses of dredged sediments. This paper summarizes some of our efforts in these areas with an emphasis on Peoria Lake which has received the most attention to date. Sediment characterization has included detailed bathymetric surveys, sediment dating with 137 Cs, chemical and mineralogical characterization of sediments to three meters depth, analysis of recent sediments (to 30 cm depth) for acid-volatile sulfide and simultaneously extracted metals, and analysis of ammonia and toxic metals in sediment pore waters. Dredged sediments have also been used in various trial projects to demonstrate potential handling and beneficial reuse strategies. Some significant findings of these studies are: 1) Long-term sedimentation rates are high, and average 1–3 cm y −1 ; 2) total concentrations of several trace metals (e.g., Pb, Cd, Ni) and PAH compounds sometimes exceed consensus-based probable effect levels for sensitive sediment-dwelling organisms; 3) pore water dissolved ammonia concentrations in Peoria Lake are potentially toxic to sensitive sediment-dwelling species; and 4) weathered sediments can make productive agricultural soils.

Illinois River↗
USGS2003

Compost: Brown gold or toxic trouble?

Limited data are available regarding the occurrence of potentially hazardous constituents in raw, uncomposted yard wastes, partially composted yard wastes, and finished compost (15, 16). Environmental monitoring at composting operations or facilities is lacking, and currently published research on the environmental fate of composted yard waste constituents is extremely limited. The cost of thoroughly investigating the fate of toxicants in yard waste may seem needlessly expensive, but it is much less than the cost of cleaning up contaminated sites and groundwater. Could yard waste compost sites become Superfund sites? The cost of a thorough testing program throughout the United States may be several million dollars, but that is only a fraction of the funds spent initiating and developing yard waste composting facilities, let alone the potentially much greater cost of environmental remediation. There is still time to address these problems and to develop sound state and federal guidelines for siting and operating yard waste compost facilities. The rush to implement landfill alternatives such as composting should not be the major driving force in determining legislation governing solid waste management. ?? 1991 American Chemical Society.

Environmental Science & Technology↗
USGS1999

Geomorphological assessment of sediment contamination in an urban stream system

Little is known about the influence of fluvial-geomorphological features on the dispersal of sediment-related contaminants in urban drainage systems. This study investigates the relation between reach-scale geomorphological conditions and network-scale patterns of trace-element concentrations in a partially urbanized stream system in East-Central Illinois, USA Robust statistical analysis of bulk sediment samples reveals levels of Cr, Cu, Pb, Ni, and Zn exceed contamination thresholds in the portion of the watershed in close proximity to potential sources of pollution-in this case storm-sewer outfalls. Although trace-element concentrations decrease rapidly downstream from these sources, substantial local variability in metal levels exists within contaminated reaches. This local variability is related to reach-scale variation in fluvial-geomorphic conditions, which in turn produces variation in the degree of sorting and organic-matter content of bed material. Metal concentrations at contaminated sites also exhibit considerable variability over time. Analytical tests on specific size fractions of material collected at a highly contaminated site indicate that Cr and Ni are concentrated in the 0.063 to 0.250 mm fraction of the sediment. This fraction also has elevated concentration of Zr. SEM analysis shows that the fine sand fraction contains shards of stainless steel within a matrix of zircon sand, an industrial material associated with a nearby alloy casting operation. Samples of suspended load and bedload at the contaminated site also have elevated amounts of trace metals, but concentrations of Ni and Cr in the bedload are less than concentrations in the bed material, suggesting that these trace elements are relatively immobile. Off the other hand, amounts of CU and Zn in the bedload exceed concentrations in the bed material, implying that these trace metals are preferentially mobilized during transport events.

Applied Geochemistry↗
USGS1995

Interlaboratory study of a method for determining nonvolatile organic carbon in aquifer materials

The organic carbon fraction in aquifer materials exerts a major influence on the subsurface mobilities of organic and organic-associated contaminants. The spatial distribution of total organic carbon (TOC) in aquifer materials must be determined before the transport of hydrophobic organic pollutants in aquifers can be modeled accurately. Previous interlaboratory studies showed that it is difficult to measure TOC concentrations <0.1% in aquifer materials, when total inorganic carbon (TIC) concentrations are >1%. We have tested a new analytical method designed to improve the accuracy and precision of nonvolatile TOC quantitation in geologic materials that also contain carbonate minerals. Four authentic aquifer materials and one NIST standard reference material were selected as test materials for a blind collaborative study. Nonvolatile TOC in these materials ranged from 0.05 to 1.4%, while TIC ranged from 0.46 to 12.6%. Sample replicates were digested with sulfurous acid, dried at 40??C, and then combusted at 950??C using LECO or UIC instruments. For the three test materials that contained >2% TIC, incomplete acidification resulted in a systematic positive bias of TOC values reported by five of the six laboratories that used the test method. Participants did not have enough time to become proficient with the new method before they analyzed the test materials. A seventh laboratory successfully used an alternative method that analyzed separate liquid and solid fractions of the acidified sample residues. ?? 1995 Springer-Verlag.

Environmental Geology↗
USGS1993

Evaluation of the extent of contaminated sediments in the west branch of the Grand Calumet river, Indiana-Illinois, USA

The extent of contamination in river sediments is often not rigorously evaluated. In many cases, only surface sediment samples are taken. In other cases, entire sediment cores are composited for analysis, an approach that limits the ability to identify discrete zones of contamination. In addition, few studies include information on the rate of sedimentation. Composited sediment cores, subsamples of cores made at discrete intervals, and surface samples were obtained from locations in the West Branch of the Grand Calumet River. The organic carbon content and concentrations of up to 26 major, minor, and trace elements were determined. Sedimentation rates at the ten locations were estimated using 137Cs. The mean concentrations of metals in the surface samples were considerably higher than concentrations in samples obtained by the two coring approaches. Only by analyzing discrete subsamples was it possible to plot the concentrations by depth and location. This approach was used to demonstrate that high levels of organic carbon and trace elements are confined between river miles 5 and 7.5. Sedimentation rate information combined with chemical analyses of the same cores indicate that contamination of this part of the river began in the 1930s.The extent of contamination in river sediments is often not rigorously evaluated. In many cases, only surface sediment samples are taken. In other cases, entire sediment cores are composited for analysis, an approach that limits the ability to identify discrete zones of contamination. In addition, few studies include information on the rate of sedimentation. Composited sediment cores, subsamples of cores made at discrete intervals, and surface samples were obtained from locations in the West Branch of the Grand Calumet River. The organic carbon content and concentrations of up to 26 major, minor, and trace elements were determined. Sedimentation rates at the ten locations were estimated using 137Cs. The mean concentrations of metals in the surface samples were considerably higher than concentrations in samples obtained by the two coring approaches. Only by analyzing discrete subsamples was it possible to plot the concentrations by depth and location. This approach was used to demonstrate that high levels of organic carbon and trace elements are confined between river miles 5 and 7.5. Sedimentation rate information combined with chemical analyses of the same cores indicate that contamination of this part of the river began in the 1930s.

Conference Paper↗
USGS1987

Measurements of210Pb,137Cs, organic carbon and trace elements in sediments of the Illinois and Mississippi rivers

Radiometric dating of sediment accumulations by137Cs and210Pb has been successfully initiated in the Illinois and Mississippi Rivers. Sedimentation rates measured at 13 locations range from 0.7 to 3.6 cm/y. Chemical analysis has been completed for up to 45 major and trace elements in core samples. The upper Illinois River contains higher metal levels than the Mississippi River. The amount of carbon (energy) lost to sediments in large floodplain rivers is estimated between 370 and 4000 g/m2/y. ?? 1987 Akade??miai Kiado??.

Journal of Radioanalytical and Nuclear Chemistry A↗
USGS1986

137Cs as a tracer of recent sedimentary processes in Lake Michigan

To determine recent sediment movement, we measured the levels of 137Cs (an artificial radionuclide produced during nuclear weapons testing) of 118 southern Lake Michigan samples and 27 in Green Bay. These samples, taken from 286 grab samples of the upper 3 cm of sediment, were collected in 1975 as part of a systematic study of Lake Michigan sediment. 137Cs levels correlated well with concentrations of organic carbon, lead, and other anthropogenic trace metals in the sediment. 137Cs had a higher correlation with silt-sized than with clay-sized sediment (0.55 and 0.46, respectively). Atmospherically derived 137Cs and trace metals are being redistributed by sedimentary processes in Lake Michigan after being incorporated in suspended sediment. We determined a distribution pattern of 137Cs that represents areas of southern Lake Michigan where sediment deposition is occurring. ?? 1986 Dr W. Junk Publishers.

Hydrobiologia↗
USGS1983

Recent geologic development of Lake Michigan (U.S.A.)

The stresses placed on Lake Michigan since the advent of industrialization require knowledge of the sedimentology of the whole lake in order to make informed decisions for environmental planning. Sediment accumulation rates are low: areas of the lake receiving the most sediment average only 1 mm a-1; deep-water basins average 0.1 to 0.5 mm a-1; and large areas are not receiving any sediment. Sediment was deposited rapidly (typically 5 mm a-1), in the form of rock flour, during the deglaciation of both Lake Michigan and Lake Superior Basins. Then the rate of accumulation decreased by 80-90% and has remained relatively constant since final deglaciation. Because active sedimentation occurs mostly in the deep water areas of the lake, the sediment remains undisturbed and contains a record of the chemical history of the lake. ?? 1983 Dr W. Junk Publishers.

Hydrobiologia↗
USGS1977

Survey of trace elements in coals and coal-related materials by neutron activation analysis

Utilizing primarily instrumental neutron activation analysis (INAA) and other analytical methods as many as 61 elements were quantitatively surveyed in 170 U.S. whole coals, 70 washed coals, and 40 bench samples. Data on areal and vertical distributions in various regions were obtained along with extensive information on the mode of occurrence of various elements in the coal matrix itself. ?? 1977 Akade??miai Kiado??.

Journal of Radioanalytical Chemistry↗