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11.
Giirkan Kuntasal Tai Y. Chang 《Journal of the Air & Waste Management Association (1995)》2013,63(10):1158-1163
A basin-wide air quality trend analysis for the South Coast Air Basin of California is conducted for hydrocarbons (HC), NOx, O3 and CO using multi-station composite daily maximum-hour average ambient concentrations for the third quarter (July, August and September) from 1968 to 1985. Emissions and air quality trends are compared for the period 1968-1984. Ambient HC and NOX trends are somewhat different from estimated emission trends of HC and NOx, while a definite, downward trend of ambient CO is consistent with vehicular emission control measures. Basin-wide ambient HC, NOx and O3 appear to show downward trends for the period 1970-1985, but because of high fluctuations it is difficult to delineate trends for shorter periods. The meteorology (850 mb temperature)-adjusted O3 shows a more consistent downward trend than does unadjusted O3. Polynomial and multiplicative regression models for basin-wide empirical O3-HC-NOx relationships Indicate that the O3 variation is explained largely by the meteorological variable (850 mb temperature) although model estimations are improved by adding HC and NOx concentration terms. 相似文献
12.
Lee TG Eom Y Lee CH Song KS 《Journal of the Air & Waste Management Association (1995)》2011,61(10):1057-1062
A simple and highly effective stabilization/solidification (S/S) technology of elemental mercury using only sulfur with paraffin is introduced. First, elemental mercury is mixed with an excess of sulfur powder and heated to 60 degrees C for 30 min until elemental mercury is converted into mercuric sulfide (HgS black, metacinnabar) (Step 1). Then, metacinnabar with additional sulfur is poured into liquid paraffin (Step 2). Finally, the mixture is melted at 140 degrees C and settles to the bottom of the vessel where it cools and solidifies under the layer of liquid paraffin (Step 3). The proposed S/S method with sodium sulfide nonahydrate (Na2S x 9H2O) as an additive is also tested for comparison. The average toxicity characteristic leaching procedure test values are 6.72 microg/L (no additive) and 3.18 microg/L (with additive). Theses concentrations are well below the Universal Treatment Standard (25 microg/L). Effective diffusion coefficient evaluated from accelerated leach test and average headspace concentration of Hg vapor after 18 hr are 3.62 x 10(-15) cm2/sec, 0.55 mg/m3 (no additive) and 5.86 x 10(-13) cm2/sec, 0.25 mg/m3 (with additive). 相似文献
13.
A pilot program focusing on municipal solid waste (MSW) source-separated collection was launched in eight major cities throughout China in 2000. Detailed investigations were carried out and a comprehensive system was constructed to evaluate the effects of the eight-year implementation in those cities. This paper provides an overview of different methods of collection, transportation, and treatment of MSW in the eight cities; as well as making a comparative analysis of MSW source-separated collection in China. Information about the quantity and composition of MSW shows that the characteristics of MSW are similar, which are low calorific value, high moisture content and high proportion of organisms. Differences which exist among the eight cities in municipal solid waste management (MSWM) are presented in this paper. Only Beijing and Shanghai demonstrated a relatively effective result in the implementation of MSW source-separated collection. While the six remaining cities result in poor performance. Considering the current status of MSWM, source-separated collection should be a key priority. Thus, a wider range of cities should participate in this program instead of merely the eight pilot cities. It is evident that an integrated MSWM system is urgently needed. Kitchen waste and recyclables are encouraged to be separated at the source. Stakeholders involved play an important role in MSWM, thus their responsibilities should be clearly identified. Improvement in legislation, coordination mechanisms and public education are problematic issues that need to be addressed. 相似文献
14.
拉索预应力空间网格结构的索张力计算及张拉全过程分析 总被引:1,自引:0,他引:1
实际工程中,对于拉索预应力空间网格结构的索张拉是一个需要反复调整的繁琐过程。对此,提出了一种针对多阶段多批次张拉施工全过程分析的计算方法,用以提高索张拉施工的效率。该法通过不断减小拉索实际张力与目标张力的差值来求解各索在张拉过程中应该产生的初始应变,最后只要利用计算结果并按照预定的顺序张拉,便可使所有索只经过一次张拉就能最终达到各自的目标张力值。对一个150 m跨度的拉索预应力球面巨型网格结构进行了计算,并利用计算结果,对结构的杆件内力和最大节点位移进行了张拉全过程跟踪分析。结果表明,在实际工程中采用上述方法进行计算与张拉是切实可行的,另外,在张拉过程中进行跟踪分析十分必要。 相似文献
15.
16.
Pei-Yi Lin Yi-Ya Fang Su-Ping Wang Mei-Yun Tai Yuan-Feen Tsai 《Die Naturwissenschaften》2012,99(3):185-189
After extinction, the reappearance of a conditioned response induced by an unconditioned stimulus which is weaker than that
used during the conditioning training indicates that the extinction procedure does not eliminate the original conditioned
memory. Recent studies on fear conditioning have shown that rats exhibited little or no recovery of conditioned responding
if the time interval between fear acquisition and extinction was short, suggesting that the extinction process may erase the
original conditioning trace in this situation. In the present study, a saving experiment was conducted in rats to investigate
whether an aversive response could be recovered following extinction training with different time intervals after acquisition
of conditioned taste aversion (CTA). Male Long–Evans rats developed CTA by associating a 0.2% sucrose solution with malaise
induced by intraperitoneal injection of 4 ml/kg 0.15 M LiCl and were subjected to extinction training with an interval of
5 h (5H group) or 24 h (24H group) after acquisition of CTA. Rats in the 5H group, but not in the 24H group, exhibited no
aversive responding to the sucrose solution followed by the injection of a lower dose of LiCl (1 ml/kg). These findings indicate
that the extinction procedure administered at different time points following the acquisition of CTA affects recovery of extinguished
aversive memory and suggest that an unlearning process may be involved in the mechanisms of CTA extinction with short intervals
between acquisition and extinction. 相似文献
17.
A nonlinear least squares procedure and a log transformation procedure for calculating first-order rate coefficients from experimental concentration-versus-time data were compared using laboratory measurements of the volatilization from water of 1,1,1-trichloroethane and 1,2-dichloroethane and the absorption of oxygen by water. Ratios of the nonlinear least squares to log transformation volatilization and absorption coefficients for 77 tests ranged from 0.955 to 1.08 and averaged 1.01. Comparison of the maximum, minimum, and mean root-mean-square errors of prediction for six sets of coefficients showed that the errors for the nonlinear least squares procedure were almost always smaller than the errors for the log transformation procedure. 相似文献
18.
北京市大气PM2.5中矿物成分的污染特征 总被引:7,自引:1,他引:6
为了解北京市大气细粒子中矿物成分的浓度水平和污染特征,在清华园和车公庄进行了连续1a的PM2.5累积周采样和全样品分析.Al、Si、Ca、Mg和Fe等地壳元素的周变化相似,最大周均浓度均出现在春季有强沙尘天气的一周;其季节变化显著,显示季节性的源排放以及气象条件对矿物成分的含量影响显著.土壤尘的季节平均浓度从夏季逐步上升,至次年春季达到最高(21.1 μg·m-3),表明春季频繁发生的沙尘天气对土壤尘细粒子有重要贡献.大量的建筑活动可能大大增加了北京细粒子中Ca的负荷,应加强其排放控制. 相似文献
19.
本文根据前屯煤矿矿井水排放规律和原水水质特征,采用KJS型一体化净水器,锰砂除铁滤器及消毒等处理工艺,处理后水质完全达到国家饮用水标准,工程投资和运行费用均较合理。 相似文献
20.
The Influence of Mycorrhiza on Uranium and Phosphorus Uptake by Barley Plants from a Field-contaminated Soil (7 pp) 总被引:3,自引:0,他引:3
Chen B Zhu YG Zhang X Jakobsen I 《Environmental science and pollution research international》2005,12(6):325-331
Background Recent studies indicated that arbuscular mycorrhizal fungi (AMF) play important roles in plant accumulation of uranium (U)
from contaminated environments, but the impacts of fertilization practices on functioning of the symbiotic associations, which
are crucial factors influencing plant nutrition and growth responses to mycorrhiza, have rarely been considered.
Materials and Methods In a greenhouse experiment, a bald root barley mutant (brb) together with the wild type (wt) were used to test the role of
root hairs and AMF in uranium (U) uptake by host plants from a U contaminated soil. Nil, 20 and 60 mg KH2PO4-P kg–1 soil were
included to investigate the influences of phosphorus (P) fertilization on plant growth and accumulation of U.
Results Dry matter yield of barley plants increased with increasing P additions and wt produced significantly higher dry weight than
brb. Mycorrhiza markedly improved dry matter yield of both genotypes grown at nil P, whereas only brb responded positively
to mycorrhiza at 20 mg P kg-1. At the highest P level, mycorrhiza resulted in growth depressions in both genotypes, except
for the roots of wt. In general, plant P concentrations increased markedly with increasing P additions and in response to
mycorrhiza.
Mycorrhiza and P additions had no significant effects on shoot U concentrations. However, root U concentrations in both genotypes
were significantly increased by mycorrhiza. On the other hand, shoot U contents increased with increasing P levels, while
20 mg P kg-1 stimulated, but 60 mg P kg-1 marginally affected the U accumulation in roots. Root length specific U uptake was
moderately enhanced both by root hairs and strongly enhanced by mycorrhiza. Moreover, non-inoculated plants generally had
higher shoot-root ratios of U content than the corresponding inoculated controls.
Conclusion Our study shows that AMF and root hairs improves not only P acquisition but also the root uptake of U, and mycorrhiza generally
decreases U translocation from plant root to shoot. Hence, mycorrhiza is of potential use in the phytostabilization of U contaminated
environments.
Perspectives The complex impacts of P on U accumulation by barley plants suggested that U behavior in mycorrhizosphere and translocation
along the soil-fungi-plant continuum as affected by fertilization practices deserve extensive studies for optimizing the function
of mycorrhizal associations for phytoremediation purposes. 相似文献