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991.
992.
ABSTRACT: Country level electoral data were used to analyze the voting patterns of eight water related constitutional amendment elections. Both water quality enhancement amendments (1971, 1976), and three of six water development amendments (1957, 1962, 1966) have been ratified, thus establishing a statewide policy of reservoir development, a funding mechanism to implement such a policy, and the creation of a water management agency. Begining with the 1969 election, a West Texas-East Texas regionalized voting pattern has emerged, resulting in the defeat of three amendments (1969, 1976, 1981) intended to provide additional funding for water development. This regionalization reflects different climatic, physiographic, economic, and locational factors, and represents a potential obstacle to coordinated water management in Texas. 相似文献
993.
Bloss WJ Gravestock TJ Heard DE Ingham T Johnson GP Lee JD 《Journal of environmental monitoring : JEM》2003,5(1):21-28
A tuneable, high pulse-repetition-frequency, solid state Nd:YAG pumped titanium sapphire laser capable of generating radiation for the detection of OH, HO2, NO and IO radicals in the atmosphere by laser induced fluorescence (LIF) has been developed. The integration of the laser system operating at 308 nm into a field measurement apparatus for the simultaneous detection of hydroxyl and hydroperoxy radicals is described, with detection limits of 3.1 x 10(5) molecule cm(-3) (0.012 pptv in the boundary layer) and 2.6 x 10(6) molecule cm(-3) (0.09 pptv) achieved for OH and HO2 respectively (30 s signal integration, 30 s background integration, signal-to-noise ratio = 1). The system has been field tested and offers several advantages over copper vapour laser pumped dye laser systems for the detection of atmospheric OH and HO2 radicals by LIF, with benefits of greater tuning range and ease of use coupled with reduced power consumption, instrument footprint and warm-up time. NO has been detected in the atmosphere at approximately 1 ppbv by single photon LIF using the Alpha 2Sigma+ <-- Chi 2Pi1/2 (0,0) transition at 226 nm, with absolute concentrations in good agreement with simultaneous measurements made using a chemiluminescence analyser. With some improvements in performance, particularly with regard to laser power, the theoretical detection limit for NO is projected to be approximately 2 x 10(6) molecule cm(-3) (0.08 pptv). Whilst operating at 445 nm, the laser system has been used to readily detect the IO radical in the laboratory, and although it is difficult to project the sensitivity in the field, an estimate of the detection limit is < 1 x 10(5) molecule cm(-3) (< 0.004 pptv), well below previously measured atmospheric concentrations of IO. 相似文献
994.
Marine sediment toxicity tests are widely applied in monitoring programs, yet relatively little is known about the comparability of data from different laboratories. The need for comparability information is increased in cooperative monitoring programs, where multiple laboratories (often with variable skill levels) perform toxicity tests. An interlaboratory comparison exercise was conducted among seven laboratories in order to document the comparability of sediment toxicity measurements during the Bight'98 regional sediment survey in southern California. Sediments from four stations in Los Angeles and Long Beach Harbors were tested using a 10-day survival test of the amphipod Eohaustorius estuarius. All laboratories successfully performed the sediment test and associated reference toxicant test. Statistically significant differences were found in mean amphipod survival rates among some laboratories for the field-collected sediments, but there was little evidence of a consistent bias among laboratories. Although the reference toxicant test indicated a five-fold variation in test sensitivity among laboratories, these results were not accurate predictors of interlaboratory performance for the sediment tests. The laboratories demonstrated excellent concordance (Kendall's W = 0.91) in ranking the field-collected sediments by toxicity. Agreement on classifying the sediments into categories (nontoxic, moderately toxic, and highly toxic) based upon the percent of survival was best for highly toxic sediments. An analysis of test precision based upon the variance among replicates within a test indicated that the measured survival rate for a sample may vary by up to 12 percentage points from the actual response. 相似文献
995.
Sock Khim Yeo Chye Peng Ong Hian Kee Lee Sam Fong Yau Li 《Environmental monitoring and assessment》1991,19(1-3):47-53
The applications of Freon-22 (R22) as a mobile phase and as a modifier in supercritical fluid chromatography were investigated. For the purpose of this investigation, the separation of eleven phenols listed by the United States Environmental Protection Agency as priority pollutants was studied. It was found that the use of neat R22 greatly reduced the retention times of the phenols compared with the use of neat carbon dioxide as mobile phase. Satisfactory separation of all the eleven phenols could be achieved using 5% R22 as modifier in carbon dioxide. The promising results obtained in this preliminary investigation indicate the potential for the use of R22 in supercritical fluid separation processes. 相似文献
996.
The decline of red spruce (Picea rubens Sarg.) in montane forests of the northeastern United States has been previously reported. The objective of this study was to assess spatial patterns, if any, in standing dead red spruce stems in the Adirondacks of New York and northern Appalachians of Vermont, New Hampshire, and Maine. A stratified random sample of 19 mountains along a west to east transect in the Adirondacks and the northern Appalachians showed that the live basal area of all species was highest in the White Mountains (34.6 m2 ha–1) and lowest in the Adirondack Mountains (23.7 m2 ha–1) in the Green Mountains was significantly lower than in any other region. Intact standing dead red spruce in the Adirondack and Green Mountains (30%) was significantly higher than that in the three eastern clusters (14%). The amount of intact standing dead red spruce trees increased with elevation in only the western part of the region. With the exception of the Adirondacks, there was a greater average percent dead red spruce on the west side than on the east side of each mountain. The sum of standing dead for other tree species (average 13%) showed no statistically significant patterns with region, elevation or aspect, and was significantly lower than the amount of total dead red spruce (average 42%). The standing dead red spruce patterns we observed cannot be associated with any specific causal factors at this time. 相似文献
997.
998.
Jackson WA Martino L Hirsh S Wrobel J Pardue JH 《Environmental monitoring and assessment》2005,107(1-3):155-171
A cylindrical dialysis sampler (1.2 m in length; 5 cm in diameter) was designed and constructed to sample small–scale phytoremediation processes in the root zone of poplar trees. The study site was a 183–tree plantation of hybrid poplars located at Aberdeen Proving Ground, Maryland, at the J–Field Area of Concern. The grove was planted in 1996 to intercept a chlorinated solvent plume containing 1,1,2,2–tetrachloroethane (1,1,2,2–TeCA, trichloroethene (TCE) and daughter products. Two dialysis samplers were installed: one directly in the poplar grove (approximately 0.3 m from the trunk of a mature tree) and the other outside of the grove but in the plume. Data collected included concentrations of chlorinated VOCs, organic acids, chloroacetic acids, Cl−, and dissolved gases (ethane, ethene, CH4, CO2). At the control location, the VOC profile was dominated by cis– 1,2–dichloroethene (cis–1,2–DCE) and trans–1,2–dichloroethene (trans–1,2–DCE) with concentrations ranging from 0.88-4.5 to 4.4-17.6 mg/L, respectively. Concentrations of VOCs were similar across the vertical profile. At the tree location, 1,1,2,2–TeCA and TCE were the dominant VOCs detected but as opposed to the control location were highly variable within the root zone, with the greatest variability associated with locations in the sampler where roots were observed. This highly variable profile at the tree location is indicative of VOC rhizosphere biodegradation and uptake near the active roots. This variability appears to be on the centimeter scale, emphasizing the importance of these high–resolution samplers for the study of rhizosphere influences. 相似文献
999.
Hong S Boutron CF Barbante C Do Hur S Lee K Gabrielli P Capodaglio G Ferrari CP Turetta C Petit JR Lipenkov VY 《Journal of environmental monitoring : JEM》2005,7(12):1326-1331
Lead (Pb), cadmium (Cd), copper (Cu) and zinc (Zn) have been measured by electrothermal atomic absorption spectrometry in various sections of the 3623 m deep ice core drilled at Vostok, in central East Antarctica. The sections were dated from 240 to 410 kyear BP (Marine Isotopic Stages (MIS) 7.5 to 11.3), which corresponds to the 3rd and 4th glacial-interglacial cycles before present. Concentrations are found to have varied greatly during this 170 kyear time period, with high concentration values during the coldest climatic stages such as MIS 8.4 and 10.2 and much lower concentration values during warmer periods, such as the interglacials MIS 7.5, 9.3 and 11.3. Rock and soil dust were the dominant sources for Pb, whatever the period, and for Zn and Cu and possibly Cd during cold climatic stages. The contribution from volcanic emissions was important for Cd during all periods and might have been significant for Cu and Zn during warm periods. 相似文献
1000.
A sediment quality index (SQI) was developed using an equation incorporating three elements; scope--the % of variables that did not meet guidelines; area frequency--the % of failed tests divided by the total number of tests in a group of sites; and amplitude - the magnitude by which failed variables exceeded guidelines. The SQI calculation produces a numerical score with a maximum value of 100 representing the highest sediment quality. A modified SQI was also developed using only the scope and amplitude elements, which computed a score per site with no grouping. The SQI was applied to assessment of sediment quality in Lakes Erie and Ontario using Canadian Federal and Ontario Provincial guidelines for 34 compounds, Spatial trends in sediment quality in both lakes reflected overall trends for most individual contaminant classes, including mercury and polychlorinated biphenyls. In Lake Erie, there was a trend toward lower SQI values from the eastern basin to the western basin, and from the northern area to the southern area of the central basin. Sediment quality in the eastern basin and the northern area of the central basin was classified as excellent (>95); sediments in other areas of Lake Erie ranged from fair to good. In Lake Ontario, the poorest sediment quality was associated with the three major depositional basins; sediment quality among the three basins was quite consistent. The SQI values based on all three elements (scope, frequency and amplitude) for the Niagara basin. Mississauga Basin and Rochester Basin were 67 (fair), 65 (fair) and 70 (fair), respectively. Comparison of SQI values for all lower lake basins showed generally poorer sediment quality in Lake Ontario, compared to Lake Erie. 相似文献