ABSTRACT: A nutrient mass balance — accounting for nutrient inputs from atmospheric deposition, fertilizer, crop nitrogen fixation, and point source effluents; and nutrient outputs, including crop harvest and storage — was calculated for 18 subbasins in the Mobile River Basin, and trends (1970 to 1997) were evaluated as part of the U.S. Geological Survey National Water Quality Assessment (NAWQA) Program. Agricultural nonpoint nitrogen and phosphorus sources and urban nonpoint nitrogen sources are the most important factors associated with nutrients in this system. More than 30 percent of nitrogen yield in two basins and phosphorus yield in eight basins can be attributed to urban point source nutrient inputs. The total nitrogen yield (1.3 tons per square mile per year) for the Tombigbee River, which drains a greater percentage of agricultural (row crop) land use, was larger than the total nitrogen yield (0.99 tons per square mile per year) for the Alabama River. Decreasing trends of total nitrogen concentrations in the Tombigbee and Alabama Rivers indicate that a reduction occurred from 1975 to 1997 in the nitrogen contributions to Mobile Bay from the Mobile River. Nitrogen concentrations also decreased (1980 to 1995) in the Black Warrior River, one of the major tributaries to the Tombigbee River. Total phosphorus concentrations increased from 1970 to 1996 at three urban influenced sites on the Etowah River in Georgia. Multiple regression analysis indicates a distinct association between water quality in the streams of the Mobile River drainage basin and agricultural activities in the basin. 相似文献
Environmental Pollution now persist in Nigeria especially the oil-rich regions of Delta State. One of these problems is due
to gas flaring. Thermal gradient resulting from the gas flared at Kwale/Okpai gas plant is hereby reported. Surface temperature
variations with distance from the flare point were investigated for the four cardinal directions. The results show a surface
temperature elevation of about 3.7° C above the mean normal daily temperature within a radius of 270 M. Hence the thermal
equilibrium has been altered. This increase in temperature has undesirable effect on man and his environment especially on
the socio-economic lives and activities of the inhabitants. It is therefore necessary that Government Agencies empowered to
monitor environment such as Federal Environmental Protection Agency (FEPA) should embark on adequate remediation activities
in order to stop the environmental degradation before enormous and permanent damage is caused. Furthermore, the companies
involved in the gas flaring should be made to be concerned with the danger they may be causing the inhabitants in particular
and the populace in general. 相似文献
The paper outlines an experimental study of influence of the ignition position and obstacles on explosion development in premixed methane–air mixtures in an elongated explosion vessel. As the explosion vessel, 1325 mm length tube with 128.5 mm diameter was used. Location of the ignition was changeable, i.e., fitted in the centre or at one of ends of the tube, when the tube was in a horizontal position. When it was in a vertical position, three locations of the ignition (bottom, centre and top) were used. In the performed study, the influence of obstacles on the course of pressure was investigated. Two identical steel grids were used as the obstacles. They were placed 405 mm from either end of the tube. Their blockage ratio (grid area to tube cross-section area) was determined as 0.33 for most of experiments. A few additional experiments (with smaller blockage ratio—0.16) were also conducted in order to compare the influence of the blockage ratio on the explosion development. Also some experiments were conducted in a semi-cylindrical vessel with volume close to 40 l.
All the experiments were performed under stabilized conditions, with the temperature and pressure inside the vessel settled to room values and controlled by means of electronic devices. The pressure–time profiles from two transducers placed in the centreline of the inner wall of the explosion vessel were obtained for stoichiometric (9.5%), lean (7%) and rich (12%) methane–air mixture. The results obtained in the study, including maximum pressures and pressure–time profiles, illustrate a quite distinct influence of the above listed factors upon the explosion characteristics. The effect of ignition position, obstacles location and their BR parameters is discussed.
The additional aim of the performed experiments was to find the data necessary to validate a new computer code, developed to calculate an explosion hazard in industrial installations. 相似文献
On 17 August 1999 at 3:04 a.m., an earthquake of 7.4 magnitude (Richter scale) struck the Marmara region in Turkey. The city of Adapazari suffered 2,680 fatalities with approximately 5,300 injured. The Israeli Defence Forces (IDF) field hospital arrived at Adapazari, on day four after the quake. The team consisted of 102 personnel. The field hospital acted as a secondary referral centre. A total of 1,205 patients were treated in the field hospital between day four and day 14 of the earthquake. The frequency distribution of the medical problems seen in the field hospital was 32 per cent internal medicine, 13 per cent general surgery including plastic, 21 per cent orthopaedic surgery, 23 per cent paediatric disease, 10 per cent obstetrics and gynaecology and 1 per cent major psychiatric disorders. A mean number of 35 patients per day were hospitalised in the field hospital for between 24 hours to one week. The rapid establishment of the field hospital enabled the local medical facilities to 'buy time' in order to organise and restore surgical and hospitalisation abilities in this disastrous situation. 相似文献
The isotopic and molecular compositions of organic matter buried in lake sediments provide information that helps to reconstruct
past environmental conditions and to assess impacts of humans on local ecosystems. This overview of sedimentary records from
the North American Great Lakes region describes examples of applications of organic geochemistry to paleolimnological reconstructions.
These lakes experienced a succession of human-induced environmental changes that started after completion of the Erie Canal
in 1825. Agricultural deforestation in the mid-nineteenth century released soil nutrients that increased algal productivity
and caused an associated increase in algal biomarkers in sediment records. Eutrophication that accompanied magnified delivery
of municipal nutrients to the lakes in the 1960s and 1970s created excursions to less negative δ13C values in sediment organic matter. Increased organic carbon mass accumulation rates mirror the isotopic evidence of eutrophication
in the Great Lakes. 相似文献