Geology topics

Scott Clifford

Publications and source records attributed to Scott Clifford.

7 recordsLinked to original sources

USGS2008

Real-Time and Delayed Analysis of Tree and Shrub Cores as Indicators of Subsurface Volatile Organic Compound Contamination, Durham Meadows Superfund Site, Durham, Connecticut, August 29, 2006

This study examined volatile organic compound concentrations in cores from trees and shrubs for use as indicators of vadose-zone contamination or potential vapor intrusion by volatile organic compounds into buildings at the Durham Meadows Superfund Site, Durham, Connecticut. The study used both (1) real-time tree- and shrub-core analysis, which involved field heating the core samples for 5 to 10 minutes prior to field analysis, and (2) delayed analysis, which involved allowing the gases in the cores to equilibrate with the headspace gas in the sample vials unheated for 1 to 2 days prior to analysis. General correspondence was found between the two approaches, indicating that preheating and field analysis of vegetation cores is a viable approach to real-time monitoring of subsurface volatile organic compounds. In most cases, volatile organic compounds in cores from trees and shrubs at the Merriam Manufacturing Company property showed a general correspondence to the distribution of volatile organic compounds detected in a soil-gas survey, despite the fact that most of the soil-gas survey data in close proximity to the relevant trees were collected about 3 years prior to the tree-core collection. Most of the trees cored at the Durham Meadows Superfund Site, outside of the Merriam Manufacturing Company property, contained no volatile organic compounds and were in areas where indoor air sampling and soil-gas sampling showed little or no volatile organic compound concentrations. An exception was tree DM11, which contained barely detectable concentrations of trichloroethene near a house where previous investigations found low concentrations of trichloroethene (0.13 to 1.2 parts per billion by volume) in indoor air and 7.7 micrograms per liter of trichloroethene in the ground water. The barely detectable concentration of trichloroethene in tree DM11 and the lack of volatile organic compound detection in nearby tree DM10 (adjacent to the well having 7.7 micrograms of trichloroethene) may be attributable to the relatively large depth to water (17.6 feet), the relatively low soil-vapor trichloroethene concentration, and the large amount of rainfall during and preceding the tree-coring event. The data indicate that real-time and delayed analyses of tree cores are viable approaches to examining subsurface volatile organic compound soil-gas or vadose-zone contamination at the Durham Meadows Superfund Site and other similar sites. Thus, the methods may have application for determining the potential for vapor intrusion into buildings.

Scientific Investigations Report↗

USGS2002

Distribution of volatile organic compounds in sediments near Sutton Brook Disposal Area, Tewksbury, Massachusetts, May 2001

Ground water at the Sutton Brook Disposal Area, a former municipal landfill in Tewksbury, Massachusetts, located adjacent to Sutton Brook, a tributary of the Shawsheen River, is contaminated by volatile organic compounds (VOCs). Results from the use of passive-vapor-diffusion samplers show vapor concentrations of petroleum hydrocarbons as high as 500,000 parts per billion by volume in pore waters of streambed sediments along an approximate 2,000-foot reach of Sutton Brook where it flows between lobes of the former landfill. Petroleum hydrocarbons were also detected in the sediments on the eastern shore of Quarry Pond, which is south of the southern landfill lobe, with a maximum vapor concentration near 2,000 parts per billion by volume. Vapor concentrations of petroleum hydrocarbons in the sediments of Sutton Brook vary by two to three orders-of-magitude over distances of 50 to 100 feet. Chlorinated hydrocarbons also were detected with passive-vapor-diffusion samplers, but generally at locations downstream of where petroleum hydrocarbons were detected, and mostly at vapor concentrations of less than 100 parts per billion by volume.

Open-File Report↗

USGS2002

Volatile Organic Compounds, Specific Conductance, and Temperature in the Bottom Sediments of Mill Pond, Ashland, Massachusetts, April 2001

A plume of volatile organic compounds in ground water extends northward from the former Nyanza Property in Ashland, Massachusetts, and discharges into the Sudbury River and the upstream end of Mill Pond. A network of polyethylene-membrane passive-vapor-diffusion samplers was installed in February 2001 to help define the lateral extent of the plume under the pond, including an area vegetated by wetland herbs, sedges, and shrubs. Chlorobenzene and trichloroethene were detected with passive-vapor-diffusion samplers at five locations in the bottom sediments of the southern part of the approximate one acre of vegetated area in Mill Pond. Vapor concentrations of chlorobenzene ranged from 178 to 2,210 parts per billion by volume, and vapor concentrations of trichloroethene ranged from 20 to 96 parts per billion by volume. Chlorobenzene also was detected in one sediment-pore-water sample extracted with a push-point sampler in this area; the concentration was 25 micrograms per liter. Toluene was detected with passive-vapor-diffusion samplers at three sites in the open pond area north of the vegetated areas. Vapor concentrations of toluene ranged from 20 to 90 parts per billion by volume. Specific conductance and temperature of sediment-pore waters were measured at selected sampling sites in Mill Pond to examine their possible associations with the presence of volatile organic compounds. Temperature in the sediment-pore water also was measured to convert vapor concentrations of volatile organic compounds collected with diffusion samplers to equivalent water concentrations. These equivalent water concentrations were then to be compared with water concentrations collected with a push-point sampler. Because of the limited detections of volatile organic compounds at sites where water samples were collected and where specific conductance and temperature were measured, these potential associations and conversions could not be assessed.

Open-File Report↗

USGS2000

Distribution of selected volatile organic compounds determined with water-to-vapor diffusion samplers at the interface between ground water and surface water, Centredale Manor site, North Providence, Rhode Island, September 1999

Volatile organic compounds are present in soils and ground water at the Centredale Manor Superfund Site in North Providence, Rhode Island. In September 1999, water-to-vapor diffusion samplers were placed in the bottom sediments of waterways adjacent to the site to identify possible contaminated ground-water discharge areas. The approximate12-acre site is a narrow stretch of land between the eastern bank of the Woonasquatucket River, downstream from the U.S. Route 44 bridge and a former mill raceway. The samplers were placed along a 2,250-foot reach of the Woonasquatucket River, in the former mill raceway several hundred feet to the east and parallel to the river, and in a cross channel between the river and former mill raceway. Volatile organic compounds were detected in 84 of the 104 water-to-vapor diffusion samplers retrieved. Trichloroethylene and tetrachloro-ethylene were the principal volatile organic compounds detected. The highest vapor concentrations measured for these two chemicals were from diffusion samplers located along an approximate 100-foot reach of the Woonasquatucket River about 500 feet downstream of the bridge; here trichloroethylene and tetrachloroethylene vapor concentrations ranged from about 2,000 to 180,000 and 1,600 to 1,400,000 parts per billion by volume, respectively. Upstream and downstream from this reach and along the former mill raceway, trichloroethylene and tetrachloroethylene vapor concentrations from the diffusion samples were generally less than 100 parts per billion by volume. Along the lower reaches of the river and mill raceway, however, and in the cross channel, vapor concentrations of trichloroethylene exceeded 100 parts per billion by volume and tetrachloroethylene exceeded 1,000 parts per billion by volume in several diffusion samples. Although diffusion sample vapor concentrations are higher than water concentrations in surface waters and in ground water, and they should only be interpreted qualitatively as relative values, these values provide important information as to potential discharge areas of contaminants.

Rhode Island↗

USGS2000

Field tests of polyethylene-membrane diffusion samplers for characterizing volatile organic compounds in stream-bottom sediments, Nyanza Chemical Waste Dump Superfund site, Ashland, Massachusetts

A plume of volatile organic compounds (VOCs) in ground water extends from the Nyanza Chemical Waste Dump Superfund site in Ashland, Massachusetts, northward toward a mill pond on the Sudbury River and eastward toward the Sudbury River and former mill raceway downstream from the mill pond. Polyethylene-membrane water-to-vapor (vapor) and water-to-water (water) diffusion samplers were installed January 1999 in bottom sediments along the Sudbury River and former mill raceway in a pilot study to determine if vapor samplers would be useful in this setting for delineating a plume of contaminants in ground water near the river and raceway, to evaluate equilibration time for vapor-diffusion samplers, and to determine if diffusion samplers might be an alternative to seepage meters (inverted steel drums) and sediment sampling for evaluating concentrations of VOCs in bottom sediments. Of five tested compounds (benzene, trichloroethene, toluene, tetrachloroethene, and chlorobenzene), chlorobenzene and trichloroethene were most frequently detected in vapor from vapor-diffusion samplers. The distribution of VOCs was generally consistent with a previously mapped plume of contaminants in ground water. The field evaluation of equilibration times for vapor-diffusion samplers was inconclusive because of changing hydrologic conditions that may have affected concentrations of VOCs, possible variations in concentrations ofVOCs over short distances, and imprecise sampling and analytical methods. The limited data, however, indicated that equilibration may require 3 weeks or more in some settings. VOCs detected in samples from water-diffusion samplers and their concentrations were comparable to results from seepage meters, and VOCs detected in vapor-diffusion samplers correlated with VOCs detected in water-diffusion samplers. These results indicate that either vapor-or water-diffusion samplers would serve as an economical alternative to seepage meters for sampling of VOCs in pore water from stream-bottom sediments. Results from diffusion samplers correlated poorly with results from sediment samples, partly because of high quantitation limits for chemical analyses of sediments. In general, results from the diffusion samplers better represented the distribution of VOCs than the results from the sediment samples. This pilot study indicates that diffusion samplers are an economical means of identifying 'hotspots' for contaminants in bottom sediments and can provide insights on transport pathways for contaminants near surface-water bodies. After establishing equilibration times for a particular site, diffusion samplers also may be useful for studying variations in concentrations of VOCs over short distances, variations with time and changing hydrologic conditions, and processes such as chemical transformations by biodegradation and exchanges between surface water and ground water in the hyporheic zone.

Water-Resources Investigations Report↗

USGS1999

Potential for advection of volatile organic compounds in ground water to the Cochato River, Baird & McGuire Superfund Site, Holbrook, Massachusetts, March and April 1998

In March and April 1998, a network of water-to-vapor diffusion samplers was installed along the Cochato River at the Baird & McGuire Superfund Site in Holbrook, Massachusetts, where a plume of volatile organic compounds (VOCs) is present in ground water. The purpose of installing the sampler network was to determine if VOCs were present in river-bottom sediments while a ground-water extraction system was operating and after the system had been shut down for two weeks. Water-to-water diffusion samplers placed at selected locations provided supplemental information about concentrations of VOCs in pore water in the river-bottom sediments. Water levels in piezometers and river stage were measured concurrently to determine if ground water was discharging to the river. Benzene, toluene, ethylbenzene and xylenes (BTEX compounds) were detected in water-tovapor and water-to-water diffusion samplers located in the area where the plume is known to pass beneath the river for both pumping and nonpumping conditions. Concentrations of total BTEX compounds in water-to-vapor diffusion samplers ranged from non-detect upriver and downriver from the plume area to greater than 200 parts per million by volume in the plume area. Concentrations of total BTEX compounds were not significantly different for pumping than for non-pumping conditions. Concentrations of total BTEX compounds in water-to-water diffusion samplers ranged from non-detect to 680 micrograms per liter. The limited number of water-to-water diffusion samplers did not indicate that concentrations were higher for pumping or non-pumping conditions. Trichloroethylene and tetrachloroethylene also were detected in water-to-vapor diffusion samplers downriver from the area where the BTEX compounds were detected. Water levels in four piezometers were consistently higher than the river stage, indicating an upward hydraulic gradient and ground-water discharge to the river. The concentrations of VOCs in riverbottom sediments and the upward hydraulic gradients observed indicate that contaminants from the Baird & McGuire ground-water plume were discharging to the Cochato River during the study period for both pumping and non-pumping conditions.

Massachusetts↗

USGS1999

Distribution of Trichloroethylene and Geologic Controls on Contaminant Pathways near the Royal River, McKin Superfund Site Area, Gray, Maine

Vapor-diffusion samplers were used in the autumn of 1997 to determine the lateral extent and distribution of concentrations of a trichloroethylene (TCE) plume in the ground-water discharge area near the McKin Superfund Site, Gray, Maine. Analyses of vapor in the samplers identified a plume about 800 feet wide entering the river near Boiling Springs, an area of ground-water discharge on the flood plain of the Royal River. The highest observed concentration of TCE in vapor was in an area of sand boils on the western bank of the river and about 200 feet downstream from Boiling Springs. Previous studies showed that most of the TCE load in the river originated in the area of the sand boils. In general, highest concentrations were observed on the western side of the river on the upgradient side of the plume, but TCE also was detected at numerous locations in the center and eastern bank of the river. The TCE plume discharges to the river where fine-grained glaciomarine sediments of the Presumpscot Formation are absent and where coarse-grained facies of buried glaciomarine fan deposits provide a pathway for ground-water flow. Based on results of analyses of vapor-diffusion samples and other previous studies, the plume appears to pass under and beyond the river near Boiling Springs and along the river for about 300 feet downstream from the sand boils. A coarse-grained, organic-rich layer at the base of the alluvial flood plain sediments is confined by overlying fine-grained alluvial sediments and may provide a conduit for ground-water leaking upward from buried glaciomarine fan deposits.

Water-Resources Investigations Report↗