排序方式： 共有3条查询结果，搜索用时 93 毫秒
1
1.
Analyses (n = 525) of chloride (Cl−), bromide (Br−), nitrate as nitrogen (NO3-N), sodium (Na+), calcium (Ca2+) and potassium (K+) in stream water, tile-drain water and groundwater were conducted in an urban-agricultural watershed (10% urban/impervious, 87% agriculture) to explore potential differences in the signature of Cl− originating from an urban source as compared with an agricultural source. Only during winter recharge events did measured Cl− concentrations exceed the 230 mg/L chronic threshold. At base flow, nearly all surface water and tile water samples had Cl− concentrations above the calculated background threshold of 18 mg/L. Mann–Whitney U tests revealed ratios of Cl− to Br− (p = .045), to NO3-N (p < .0001), to Ca2+ (p < .0001), and to Na+ (p < .0001) to be significantly different between urban and agricultural waters. While Cl− ratios indicate that road salt was the dominant source of Cl− in the watershed, potassium chloride fertilizer contributed as an important secondary source. Deicing in watersheds where urban land use is minimal had a profound impact on Cl− dynamics; however, agricultural practices contributed Cl− year-round, elevating stream base flow Cl− concentrations above the background level. 相似文献
2.
ZhaoHui Joey Yang 《寒旱区科学》2019,11(1):1-12
Winter maintenance operations are crucial for pedestrian and motorist safety and public mobility on urban streets and highways in cold regions, especially during winter storms. This study provides a comprehensive literature review of existing deicing technologies, with emphasis on electrical resistance-heating deicing technologies for possible applications in areas with concentrated traffic, such as street intersections and crosswalks. A thorough review of existing and emerging deicing technology for snow/ice melting was conducted. The performance of various deicing methods was evaluated and the installation and operation cost of the electrical resistance-heating methods compared. Finally, current state of the practice of intersection/crosswalk winter maintenance was surveyed among state departments of transportation in North America. The intersection/crosswalk winter maintenance procedure adopted by the State of Alaska Department of Transportation and Public Facilities was described, and the annual winter maintenance and operation cost per intersection was estimated. It was found that the annual energy cost of an electrical resistance-heating method such as the carbon-fiber-tape deicing technology is about the same as the average annual maintenance and operation cost of current practice. In addition, an automatic electrical resistance-heating deicing system will bring benefits such as minimized delay time and improved safety for pedestrian and vehicular traffic in an urban application. 相似文献
3.
Pathways and fate of road deicing salt (NaCl) applied during the 1994–1995 winter were studied for a 14-km section of a major highway that crosses the Oak Ridges Moraine in southern Ontario. Total salt applications over the winter ranged from 29 to 74 kg m−1 of highway, and NaCl concentrations in snow banks adjacent to the roadway reached 9400 mg l−1 during the later stages of snow cover development. This salt was released to the ground surface during snowmelt. Sodium chloride (NaCl) loadings to soil from snow cover during the final melt phase were relatively uniform along the study section (3–5 kg NaCl m−1 of highway). However, the snowpack at all transects retained <50% of applied NaCl, and this shortfall probably reflected direct runoff and infiltration of saline meltwater from the road surface into the adjacent shoulder and right-of-way. Cation exchange with Ca2+ in near-surface soils most likely resulted in preferential retention of Na+ relative to Cl−, although total storage of NaCl in upper soil horizons by winter's end was <15% of deicing salt applications. An environmental tracer (18O) was used to trace movement of saline meltwater through the unsaturated zone underlying the highway. Average meltwater particle velocities at a site underlain by loam soils were 0.02 m d−1, and ca. 280 mm of water was displaced below a depth of 1.86 m over a 78-day period in the spring and summer of 1995. Sodium ion and chloride ion concentrations in water sampled in late summer 1995 at depths >2 m exceeded 500 mg l−1 and 1000 mg l−1, respectively. Approximately 75% of the net flux of NaCl below the upper soil was retained in the 0–2.8 m depth interval at this site, and results from more permeable soils traversed by the highway indicate an even greater penetration of the annual NaCl application into the unsaturated zone along the moraine. This saline water likely recharges groundwater in this portion of the Oak Ridges Moraine. 相似文献
1