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41.
Mr. M. T. Rebello C. T. H. Gray D. E. Rooney J. H. Smith G. A. Hackett F. E. Loeffler D. H. Horwell R. W. Beard D. V. Coleman 《黑龙江环境通报》1991,11(1):35-40
One hundred and fourteen samples of amniotic fluid taken before 15 weeks of gestation were cultured for cytogenetic studies. The results of culturing these early amniotic fluid (EAF) samples were compared with the results of culturing 114 standard amniotic fluid (SAP) samples taken after 15 weeks of gestation matched for maternal age and received in the laboratory within the same week. Cell culture was successful in all 114 of the EAF samples and in 111 SAP samples. There was no significant difference in the days to harvesting and days to reporting in the two groups. Three samples of SAP failed to grow and two EAF samples produced tetraploid karyotypes, so that in these five cases amniocentesis had to be repeated. These problems were attributed to toxicity of a fungicide used in the culture medium. Pseudomosaicism was noted in two EAF samples and one SAP sample; and maternal cell contamination was noted in one EAF and one SAP sample. Thus, culturing and karyotyping cells harvested from EAF and SAP are similar, indicating that EAF samples from 12–14-week pregnancies could be used for prenatal diagnosis. 相似文献
42.
In a preliminary study, the uptake and the mobility of uranium (U) by black oak trees (Quercus velutina) were assessed by measuring the isotopic composition of tree rings in two mature oak trees in a heavy metal contaminated bog in Concord, MA. The bog is adjacent to a nuclear industrial facility that has been processing depleted uranium (DU) since 1959. Over the past 40 years, DU has been leaking from an onsite holding basin and cooling pond down gradient to the bog where the oaks are located. Because DU has no source outside the nuclear industry, contamination from the industrial facility is readily discernable from uptake of natural U by measuring isotopic compositions. Isotope ratio analysis confirms the occurrence of DU in bark, sapwood and heartwood tree rings dating back to 1937, pre-dating the introduction of DU at the site by at least 20 years. Isotope dilution analysis indicates high concentrations of U (>3 ppb) in sapwood that drop rapidly to relatively constant concentrations (0.3-0.4 ppb) in heartwood. These data indicate that once incorporated into tree cells, U is mobile, possibly by diffusion through the tree wood. Concentrations of U in sapwood are approximately equal to average U concentrations in groundwater onsite over the past 10 years, suggesting that oak trees can be used as present-day bioindicators of U-contaminated groundwater. We suggest that regional sampling of oak bark and sapwood is a reasonable, inexpensive alternative to drilling wells to monitor shallow groundwater U contamination. 相似文献
43.
44.
PROBLEM: Mining in the United States remains one of the most hazardous industries, despite significant reductions in fatal injury rates over the last century. Coal mine fatality rates, for example, have dropped almost a thousand-fold since their peak in 1908. While incidence rates are very important indicators, lost worktime measures offer an alternative metric for evaluating job safety and health performance. The first objective of this study examined the distributions and summary statistics of all injuries reported to the Mine Safety and Health Administration from 1983 through 2004. Over the period studied (1983-2004), there were 31,515,368 lost workdays associated with mining injuries, for an equivalent of 5,700 person-years lost annually. The second objective addressed the problem of comparing safety program performance in mines for situations where denominator data were lacking. By examining the consequences of injuries, comparisons can be made between disparate operations without the need for denominators. Total risk in the form of lost workday sums can help to distinguish between lower- and higher-risk operations or time periods. METHOD: Our method was to use a beta distribution to model the losses and to compare underground coal mining to underground metal/nonmetal mining from 2000 to 2004. RESULTS: Our results showed the probability of an injury having 10 or more lost workdays was 0.52 for coal mine cases versus 0.35 for metal/nonmetal mine cases. In addition, a comparison of injuries involving continuous mining machines over 2001-2002 versus 2003-2004 showed that the ratio of average losses in the later period to those in the earlier period was approximately 1.08, suggesting increasing risks for such operations. DISCUSSION: This denominator-free safety measure will help the mining industry more effectively identify higher-risk operations and more realistically evaluate their safety improvement programs. IMPACT ON INDUSTRY: Attention to a variety of metrics concerning the performance of a job safety and health program will enhance industry's ability to manage these programs and reduce risk. 相似文献
45.
Environmental Economics and Policy Studies - This paper examines the interaction of different policies used to control two types of agricultural pollution. Pollution control policy is efficient... 相似文献
46.
Largely influenced by the passage of the Swamp Land Act of 1849, many wetlands were lost in the coastal plain region of the southeastern United States, primarily as a result of drainage for agricultural activities. To better understand the chemical response of soils during wetland conversion, soil core samples were collected from the converted beef cattle pastures and from the natural wetland at Plant City, FL in the summers of 2002 and 2003. Data collected from the natural wetland sites were used as reference data to detect potential changes in soil properties associated with the conversion of wetlands to improved beef cattle (Bos taurus) pastures from 1940 to 2003. The average concentration of total phosphorus (TP) in pasture soils (284 mg kg(-1)) was significantly (p = 0.001) lower than its levels in natural wetland soils (688 mg kg(-1)). Compared with the adjoining natural wetlands, the beef cattle pasture soils, 63 yr after being drained exhibited: (1) a decrease in TOC (-172 g kg(-1)), TN (-10 g kg(-1)), K (-0.7 mg kg(-1)), and Al (-130 mg kg(-1)); (2) an increase in soil pH (+1.8), Ca (+88 mg kg(-1)), Mg (+7.5 mg kg(-1)), Mn (+0.3 mg kg(-1)), and Fe (+6.9 mg kg(-1)); and (3) no significant change in Na, Zn, and Cu. Wetland soils had higher concentrations (mg kg(-1)) of Al-P (435), CaMg-P (42), FeMn-P (43), and Org-P (162) than those of 172, 11, 11, and 84 mg kg(-1), respectively, found in the pasture soils. The levels of water-soluble P and KCl-bound P were comparable between wetland and pasture soils in 2003. Results of this study therefore suggest that wetland conversion to beef cattle pastures did not function as a source of nutrients, especially P and N, even with manure and urine additions due to the presence of grazing cattle. 相似文献
47.
Burnley S Phillips R Coleman T Rampling T 《Waste management (New York, N.Y.)》2011,31(9-10):1949-1959
Waste management policies and legislation in many developed countries call for a reduction in the quantity of biodegradable waste landfilled. Anaerobic digestion, combustion and gasification are options for managing biodegradable waste while generating renewable energy. However, very little research has been carried to establish the overall energy balance of the collection, preparation and energy recovery processes for different types of wastes. Without this information, it is impossible to determine the optimum method for managing a particular waste to recover renewable energy. In this study, energy balances were carried out for the thermal processing of food waste, garden waste, wood, waste paper and the non-recyclable fraction of municipal waste. For all of these wastes, combustion in dedicated facilities or incineration with the municipal waste stream was the most energy-advantageous option. However, we identified a lack of reliable information on the energy consumed in collecting individual wastes and preparing the wastes for thermal processing. There was also little reliable information on the performance and efficiency of anaerobic digestion and gasification facilities for waste. 相似文献
48.
John M. Cheeseman Steven C. Lund Coleman A. Doggett Thomas O. Perry 《Journal of the Air & Waste Management Association (1995)》2013,63(12):1213-1216
Meteorological dispersion modeling and pine trees used as "integrating monitors" were used to consider the probable source of a phytotoxic pollutant producing symptoms previously un-reported in the literature. Two sources, a chemical plant (A) and a fabric finishing plant (B) north of Raleigh, NC, were considered using the Air Quality Display Model (AQDM). Using the ability of this model to accommodate extra receptors corresponding to "monitoring" sites, we found good correlation between observed injury and predicted relative concentrations due to assumed emissions from source A. The poor agreement between predicted and observed injury if source B alone were modeled (or both sources together) suggested that source A alone emitted the causal agent. 相似文献
49.
Quantifying phosphorus levels in soils, plants, surface water, and shallow groundwater associated with bahiagrass-based pastures 总被引:1,自引:1,他引:0
Gilbert C. Sigua Robert K. Hubbard Samuel W. Coleman 《Environmental science and pollution research international》2010,17(1):210-219
Background, aim, and scope
Recent assessments of water quality status have identified eutrophication as one of the major causes of water quality ‘impairment’ not only in the USA but also around the world. In most cases, eutrophication has accelerated by increased inputs of phosphorus due to intensification of crop and animal production systems since the early 1990s. Despite substantial measurements using both laboratory and field techniques, little is known about the spatial and temporal variability of phosphorus dynamics across landscapes, especially in agricultural landscapes with cow-calf operations. Critical to determining environmental balance and accountability is an understanding of phosphorus excreted by animals, phosphorus removal by plants, acceptable losses of phosphorus within the manure management and crop production systems into soil and waters, and export of phosphorus off-farm. Further research effort on optimizing forage-based cow-calf operations to improve pasture sustainability and protect water quality is therefore warranted. We hypothesized that properly managed cow-calf operations in subtropical agroecosystem would not be major contributors to excess loads of phosphorus in surface and ground water. To verify our hypothesis, we examined the comparative concentrations of total phosphorus among soils, forage, surface water, and groundwater beneath bahiagrass-based pastures with cow-calf operations in central Florida, USA. 相似文献50.
Kiran Liversage Victoria J. Cole Christopher D. McQuaid Ross A. Coleman 《Marine Biology》2012,159(12):2777-2786
Patchy distributions within landscapes may be caused by migration in response to different types of habitat patches. Intertidal boulder fields are landscapes in which boulders are discrete habitat patches, often with chitons attached to their under-surfaces. Chiton densities and associations with patch edges differed between boulders overlying coarse- versus fine-sediment types, with greater densities occurring over fine sediments. We tested whether adult migration caused between-boulder distributions by measuring immigration and emigration following experimental replacement of coarse sediments with fine sediment under boulders. We also assessed whether the manipulations altered chiton positions relative to patch edges, and large-scale generality was tested by including data from two continents. The manipulations did not influence the association of chitons with edges or amounts of emigration, but chitons did display positive density-dependent immigration that mirrored their distributional patterns, indicating the importance of immigration. Strikingly, all results were consistent between continents despite involving different species and even genera of chitons. By using boulder fields as a small-scale, easily manipulated landscape, we show that, even in sedentary organisms, patchy distributions within landscapes can be caused by migration alone, without the need to invoke mortality or larval recruitment. 相似文献