1,463 research outputs found
REGIONAL AND FUNCTIONAL DISAGGREGATION OF THE COTTON INDUSTRY IN A NATIONAL INPUT-OUTPUT MODEL
Crop Production/Industries,
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Using deuterated PAH amendments to validate chemical extraction methods to predict PAH bioavailability in soils
Validating chemical methods to predict bioavailable fractions of polycyclic aromatic hydrocarbons (PAHs) by comparison with accumulation bioassays is problematic. Concentrations accumulated in soil organisms not only depend on the bioavailable fraction but also on contaminant properties. A historically contaminated soil was freshly spiked with deuterated PAHs (dPAHs). dPAHs have a similar fate to their respective undeuterated analogues, so chemical methods that give good indications of bioavailability should extract the fresh more readily available dPAHs and historic more recalcitrant PAHs in similar proportions to those in which they are accumulated in the tissues of test organisms. Cyclodextrin and butanol extractions predicted the bioavailable fraction for earthworms (Eisenia fetida) and plants (Lolium multiflorum) better than the exhaustive extraction. The PAHs accumulated by earthworms had a larger dPAH:PAH ratio than that predicted by chemical methods. The isotope ratio method described here provides an effective way of evaluating other chemical methods to predict bioavailability
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Geology of Sierra Del Carmen, West Texas and Mexico: A General Geologic Framework to Support Mapping of Biologic (Botanical) Resources
The purpose of this study is to provide geologic base maps to support the mapping of biological (botanical) resources in the Sierra del Carmen, Coahuila, Mexico, and adjacent areas in Big Bend National Park, Brewster County, Texas. Sierra del Carmen, which generally trends north-northwestward, includes the eastern part of Big Bend National Park and extends southerly into adjacent Coahuila. The range, which is within the Chihuahuan Desert, rises abruptly from the desert floor and has topographic relief that exceeds 2,000 m. The terrain is rugged, and the range is marked by numerous narrow and steep-sided canyons and valleys. The stratigraphic framework of the range is one aspect that controls the distribution of vegetation throughout the area. In general, different rock types can weather into soils of different composition, and the rocks and soils may contain different amounts of moisture. Thus, different plant species may be associated with specific rock lithologies. Geologic structures such as faults, folds, and fracture zones control the position of the rock units and influence landforms, drainage directions, and canyon development. Structures may also influence the concentration and retention of surface moisture. The geologic map of this region is intended to assist other scientists, students, and interested visitors in understanding the geology of this fascinating area and in interpreting the influence of the geologic framework on related sciences. The map emphasizes bedrock and surficial units that can be important controls on the distribution of plant communities.Bureau of Economic Geolog
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Regional Geologic Setting of the Eagle Flat Study Area, Hudspeth County, Texas
The Eagle Flat study area lies near the eastern limit of the Basin and Range geologic province in Trans-Pecos Texas. The geologic features of the region record a long history of geologic events. By describing the regional geologic setting, we can place the Eagle Flat study area within a larger context, and the significance of the site-specific investigations can be more properly understood. In general, the discussions are arranged chronologically, from oldest to youngest; each characterizes the regional geologic framework and describes how the proposed site at Faskin Ranch fits within that geologic setting.
The oldest rocks in the region are metamorphosed Precambrian sedimentary and igneous rocks. Precambrian rocks crop out about 6 miles (9 km) east of the proposed repository site and are extensively exposed in the hills in the northeast part of the study area and in the Carrizo Mountains east of the Eagle Flat study area. Precambrian rocks are also present in isolated occurrences on the northeast flank of the Eagle Mountains, southeast of the site, on the Diablo Plateau, and in the Franklin Mountains, and in New Mexico. In northeastern Chihuahua, Precambrian rocks are present in limited outcrops but are known primarily from deep exploratory drilling. The Precambrian rocks show evidence of sedimentation, magmatism, metamorphism, and deformation before deposition of overlying Paleozoic and younger strata. The greater depth of burial of Precambrian rocks in Chihuahua is interpreted to be partly a manifestation of Precambrian faulting and subsidence associated with a wide northwest-trending zone that parallels the Rio Grande. This zone, the Texas Lineament, broadly trends through the study area and locally coincides with younger geologic structures.Bureau of Economic Geolog
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Summary Report for the El Paso, Texas STATEMAP Project, 1996
The El Paso STATEMAP project has focused on mapping the El Paso/Rio Grande Border area in far west Texas. Geologic mapping is critical in this area because of the pressures of development, exploitation of natural resources, and degradation of the environment by increased industrialization. In addition, the North American Free Trade Agreement (NAFTA) is stimulating additional growth in this area. El Paso is growing rapidly northward along the flanks of the Franklin Mountains and eastward along the Rio Grande valley, the valley border margins, and the Hueco Bolson floor paralleling Interstate Highway 10 and U.S. Highway 62/184. Much of the land north of U.S. Highway 62/184 is Fort Bliss military land and, thus, unavailable for urbanization.
This third and final year of 1:24,000-scale geologic mapping of the El Paso, Texas, region resulted in the completion of 11 quadrangles. The completed Canutillo and Smeltertown quadrangles cover an area that extends westward from the west part of the Franklin Mountains to the Rio Grande. The Padre Canyon, TP Well, and Whiterock Hills quadrangles encompass the south edge and foothills of the Hueco Mountains and the northeast margins of the basin floor. The Isla, Tornillo, Fort Hancock NW, Acala, McNary, and Esperanza quadrangles contain the basin floor and Rio Grande valley and valley border.Bureau of Economic Geolog
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