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1.
Described in this paper is an experiment on atmosphere-surface turbulent exchange and boundary layer turbulence properties conducted in July 1994 over the Kerqin Grassland,Jilin,China.The characteristics of the turbulent spectrum,and the relationships of the standard deviation of the turbulent velocity components and sensible heat flux with the atmospheric stability are studied using data from a sonic anemometer and a fast-response platinum resistance thermometer mounted on a 100 m tower.The results show that in the surface layer over a flat,uniform and open grassland,for a broad stability range(-22.12≤ZiL≤17.98),the velocity spectra obey the-2/3 power law in the inertial subrange,and 1 power law at low frequencies.Under near neutral stratification,σu/u*=1.20,σv/u*=1.23 and σw/u*=1.02.For Zi/L≤-0.2,the standard deviations of the turbulent velocity components follow a 1/3 power law.For Zi/L≤-0.1,the standard deviation of the temperature fluctuations follows a-1/3 power law,and as Zi/L≤-0.08,it exhibits nonlinear behavior.Sensible heat flux is well correlated to the stability parameter.  相似文献   

2.
This paper reports the analysis results (including pH,conductivity and ion concentrations) of the precipitation samples collected at the Chinese Great Wall Station,Antarctica (62°13'S, 58°58'W,ASL10.0 m) in 1998.The average pH value and conductivity were 5.62 and 85.16 μS/cm,respectively.The pH value and conductivity of precipitation were higher during autumn, but lower during other seasons.The major ions in the precipitation were Cl- and Na+,followed by SO42-,Mg2+,Ca2+,K+,NO3-,NH4+ with the lower concentrations in order.The positive correlation significantly existing between the major ions,except NO3- and NH4+,indicated that those major ions might come from same sources.The fact that the relative abundances of ions in precipitation were very close to that of seawater of Antarctic Ocean indicated that marine aerosol was the dominant source of the ions of precipitation.However,there were yet other sources which may contribute to Ca2+ ion in the precipitation.The precipitation at the area was characterized by marine type chemically.  相似文献   

3.
利用2004年以来东亚地区10个本底观测站大气φ(CO2)观测资料,分析了各站大气φ(CO2)的变化特征及其各站之间的差异,讨论了下垫面特征、源汇作用等对φ(CO2)变化的影响.结果表明:10个本底站大气月均φ(CO2)有明显的季节变化,高值多出现在冬春等寒冷季节,而低值则多出现在6—9月,属于北半球的夏季;大气φ(CO2)日变化趋势较为一致,15时(当地时间)前后达到全天最低,随后φ(CO2)升高,并在日落后继续积累,至清晨7时(当地时间)前后达到全天最高,之后φ(CO2)随着太阳辐射的增强而逐渐降低,且平均φ(CO2)水平与下垫面植被量成反比,φ(CO2)日变化的幅度与下垫面植被量成反比.作为全球基准站之一的瓦里关山站,2004—2008年φ(CO2)年均值逐年增加,年增长率为2.28×10-6/a.  相似文献   

4.
2014年3月13日至4月20日在福建三明市利用PM2.5中流量采样器采集大气中PM2.5膜样品,测定了PM2.5的质量浓度,并用热/光碳分析仪和离子色谱分析了其组分变化特征.结果表明,三明市观测期间PM2.5的平均质量浓度为73.61±0.73 μg/m3,有机碳(OC)和元素碳(EC)的平均质量浓度分别为7.26±1.00和5.63±0.27 μg/m3,水溶性离子中SO42-、NH4+、NO3-和Na+的质量浓度分别为18.08±12.19、4.18±3.56、2.77±1.16和2.73±0.23 μg/m3,总和占总水溶性离子的87.76%.结合后向轨迹分析了福建三明市的污染物来源特征.该地区OC/EC的平均比值小于2,SOC(二次有机碳)生成量很少,主要以一次有机污染物为主,OC、EC与K+的相关性分析表明OC、EC与K+的来源相近,可以判断OC、EC绝大部分来源是生物质燃烧产生的污染物.在水溶性离子分析中,观测期间NO3-/SO42-为0.159±0.02,表明三明市主要以固定源为主,机动车辆等移动源贡献较少.  相似文献   

5.
本文直接从定义出发证明:若μA和μB是凸模糊度,则μA μB也是凸模糊度。方法是先把μA和μB分成几种情况.然后逐一加以证明,这样可得出μA μB在一般情况下是凸模糊度的结论。  相似文献   

6.
南京市城市不同功能区PM10和PM2.1质量浓度的季节变化特征   总被引：1，自引：0，他引：1  
使用Anderson-Ⅱ型9级撞击采样器测量了南京市鼓楼商业区、江北工业区、钟山风景区和宁六高速公路交通源春、夏、秋三季的大气气溶胶质量浓度。分析结果表明:南京市PM2.1和PM10的质量浓度存在明显的季节变化,秋季>春季>夏季;ρPM10春季为167.47 μg/m3,夏季为 85.99 μg/m3,秋季为238.99 μg/m3;ρPM2.1春季为59.66 μg/m3,夏季为42.80 μg/m3,秋季为100.15 μg/m3。不同季节中ρPM10和ρPM2.1均存在较好的相关性,夏季相关性最好,相关系数为0.952;秋季次之,相关系数为0.783;春季相对较差,相关系数为0.613。城市不同功能区之间ρPM2.1和ρPM10的质量浓度值差异很大,交通源>工业区>商业区>风景区。城市不同功能区的质量浓度谱分布基本一致,均为双峰型分布,峰值分别位于0.43~0.65 μm/m3和9.0~10.0 μm/m3。南京市春、夏、秋三个季节大气粒子质量浓度谱为双峰分布,粒子主要集中在0.43~3.3 μm/m3的粒径段。江北工业区ρPM10和ρPM2.1质量浓度的相关系数为0.814,略高于鼓楼商业区的0.797。  相似文献   

7.
2018年1月,利用颗粒物采样器采集武汉市大气PM2.5样品并进行水溶性无机离子（F-、Cl-、NO3-、SO42-、Na+、NH4+、K+、Mg2+、Ca2+）的分析.结果表明,NO3-、SO42-、NH4+是PM2.5中最主要的3种水溶性无机离子,除Mg2+与Ca2+外,PM2.5与WSⅡs （水溶性无机离子）之间的相关性显著,且移动源贡献占主导地位.阴阳离子平衡表明武汉市冬季灰霾期PM2.5呈中性或弱酸性.通过混合单粒子拉格朗日综合轨迹模式模拟并采用分层聚类得出了4种主要的后向气流轨迹及相应的PM2.5和水溶性离子浓度,结果表明区域传输对此次灰霾期影响较大.  相似文献   

8.
使用Anderson-Ⅱ型9级撞击采样器测量了南京市鼓楼商业区、江北工业区、钟山风景区和宁六高速公路交通源春、夏、秋三季的大气气溶胶质量浓度。分析结果表明:南京市PM2.1和PM10的质量浓度存在明显的季节变化,秋季>春季>夏季;ρPM10春季为167.47 μg/m3,夏季为 85.99 μg/m3,秋季为238.99 μg/m3;ρPM2.1春季为59.66 μg/m3,夏季为42.80 μg/m3,秋季为100.15 μg/m3。不同季节中ρPM10和ρPM2.1均存在较好的相关性,夏季相关性最好,相关系数为0.952;秋季次之,相关系数为0.783;春季相对较差,相关系数为0.613。城市不同功能区之间ρPM2.1和ρPM10的质量浓度值差异很大,交通源>工业区>商业区>风景区。城市不同功能区的质量浓度谱分布基本一致,均为双峰型分布,峰值分别位于0.43~0.65 μm/m3和9.0~10.0 μm/m3。南京市春、夏、秋三个季节大气粒子质量浓度谱为双峰分布,粒子主要集中在0.43~3.3 μm/m3的粒径段。江北工业区ρPM10和ρPM2.1质量浓度的相关系数为0.814,略高于鼓楼商业区的0.797。  相似文献   

9.
From July to September of 1990,CH4 flux measurements were made in Lin'an rice paddies using gradient profile techniques.Some characteristics of the turbulence structure under the stable conditions have been verified in the surface layer according to the in situ measurements.The semi-empirical turbulent parameters βm,βh and βc and their changes with the stability parameter Ri are given.Observed results indicate that CH4 flux in the rice-paddy is mainly decided by the methnogenesis and the process of CH4 transport from internal soils to the atmosphere,and that the CH4 vertical transfer is depressed in the stable surface layer.The CH4 flux shows that its obvious diurnal changes,and the mean CH4 flux are higher in nighttime and lower in daytime,and the peaks appear at about 2000 BST at night and 0300 BST in the early morning,respectively.The mean value of CH4 flux is about 4.18±2.3 mg/m2 h.  相似文献   

10.
为研究尺寸和镉(Cd2+)质量浓度对罗非鱼积累和转移水环境中Cd2+的影响,用室内培养的方法,选取4种尺寸的罗非鱼,设置不同质量浓度Cd2+的暴露试验,分别测定其半致死率、Cd2+积累量和对Cd2+的转移系数以及罗非鱼的相对增长率.结果表明:不同尺寸的罗非鱼对Cd2+的响应不同,其中,幼龄鱼的LC50浓度最低,体长为31.5±3.4 cm的罗非鱼LC50最高;低质量浓度Cd2+(0.5 mg/kg)处理下,罗非鱼尺寸不同,相同鱼组织对Cd2+的吸收积累量差异显著(P< 0.05),而高质量浓度Cd2+处理时,不同尺寸罗非鱼的同一组织对Cd2+的积累量无显著性差异;除体长27.4±2.9 cm罗非鱼外,相同尺寸的罗非鱼Cd2+转移系数都是低质量浓度显著大于高质量浓度(P< 0.05);高质量浓度Cd2+处理对各种尺寸罗非鱼质量增加的抑制率显著高于低质量浓度Cd2+处理的抑制率.此外,不同Cd2+质量浓度对相同尺寸的罗非鱼也产生不同的影响.因此,罗非鱼的尺寸和Cd2+质量浓度都对罗非鱼积累和转移Cd2+产生影响.  相似文献   

11.
以美人蕉、芦苇、香蒲、黄色鸢尾、水菖蒲、茭白为供试植物,以河沙和青砂为供试基质,通过模拟不同的人工湿地系统研究了植物生长特征及其人工湿地净化能力的变化.结果表明:与河沙处理相比,河沙+蚯蚓处理和河沙+青砂+蚯蚓处理中美人蕉的株高分别增加了42%和47%,叶长分别增加了36%和49%,株径分别增加了28%和20%;同样地,黄花鸢尾的株高分别增加了33%和23%,叶长分别增加了39%和29%,且水菖蒲的株高分别增加了53%和32%.与河沙处理相比,河沙+蚯蚓处理,河沙+青砂+蚯蚓处理中水菖蒲的SPAD值分别增加了20%和30%,黄花鸢尾的SPAD值分别增加了59%和65%,美人蕉的SPAD值分别增加了18%和11%.与对照人工湿地(CK)相比,人工湿地Ⅰ(河沙+植物)、人工湿地Ⅱ(河沙+植物+蚯蚓)和人工湿地Ⅲ(河沙+青砂+植物+蚯蚓)对COD的去除率分别增加了20%,24%和26%,对TP的去除率分别增加了14%,15%和19%,对NH4-N的去除率分别增加了17%,23%和21%,对TN的去除率分别增加了5%,15%和12%.人工湿地Ⅱ中茭白、芦苇、水菖蒲和黄花鸢尾的密度高于人工湿地Ⅲ.粒径较小的河沙有利于植物的生长和氮的去除,而粒径较大的青砂对磷有较高的去除率.  相似文献   

12.
湿地是人类生存和发展的重要环境之一,然而城镇化在带动经济发展的同时也严重影响了湿地生态系统。本文利用城乡梯度研究方法结合湿地分布特征,设置从沈阳城市中心到城市边缘的研究样带,沿着城镇密集区（浑河）—郊区（蒲河）—乡村（卧龙湖,仙子湖）梯度带选取典型湖泊和河流湿地样地为研究对象,系统分析城镇化对湿地水体碳氮磷含量的影响。研究发现湿地水体碳氮磷含量与城乡梯度具有相关性,总碳（TC）和可溶性有机碳（DOC）含量及SUVA280值沿城镇密集区—郊区—乡村梯度带逐渐增加,即远离市中心的乡村卧龙湖湿地最高,分别为（120.68±2.34）mg/L,（41.56±6.27）mg/L和（0.35±0.10）L/(mg·m),显著高于位于四环以外乡村仙子湖湿地、流经沈阳市四环蒲河和穿越三环浑河湿地水体。湿地水体氮磷含量总体上沿着城乡梯度带呈降低趋势,但蒲河湿地水体总氮（TN）和总磷（TP）含量最高,分别为（5.35±0.19）mg/L和（1.45±0.07）mg/L,显著高于位于城镇密集区的浑河湿地水体。城镇化作用总体上增加了湿地水体铵态氮（NH4+-N）和硝态氮（NO3--N）含量,其中,横穿城镇密集区的浑河湿地水体NH4+-N含量最高,为（1.28±0.14）mg/L;NO3--N含量则是位于郊区的蒲河湿地水体最高,为(1.42±0.15) mg/L。研究结果表明城镇化改变了湿地生态系统水体碳氮磷含量,使水体DOC含量降低,小分子化合物增多,不利于DOC在水体中的累积;同时由于人类活动的加剧也使氮磷排放增加,使水体氮磷超标,导致流经城镇密集区部分的浑河和蒲河湿地NH4+-N和NO3--N含量高于乡村。未来随着城镇化的不断发展,应严加控制和合理规划,防止城镇化导致的湿地水体污染和生态系统的破坏。  相似文献   

13.
A comprehensive study on the chemical compositions of rainwater was carried out from June 2007 to December 2008 in Guiyang, a city located on the acid rain control zone of southwest China. All samples were analyzed for pH, major anions (F−, Cl−, NO3−, SO42−), major cations (K+, Na+, Ca2+, Mg2+, NH4+), Sr2+ and Sr isotope. The pH increase is due to the result of neutralization caused by the alkaline dust which contain large amount of CaCO3. It was observed that Ca2+ was the most abundant cation with a volume-weighted mean (VWM) value of 217.6 μeq/L (52.7–1928 μeq/L), accounting for 66% (39%–88%) of the total cations. SO42− was the most abundant anion with VWM value of 237.8 μeq/L (49.6-1643 μeq/L). SO42− and NO3− were dominant among the anions, accounting for 66%–97% of the total measured anions. The Sr concentrations vary from 0.01 to 0.92 μmol/L, and strontium isotopic ratios vary in the range of 0.707684–0.710094, with an average of 0.708092. The elements ratios and the 87Sr/86Sr ratios showed that the solutes of rainwater mainly come from weathering of carbonate and secondary dust input. Moreover, urbanization results in the calcium-rich dust increased and the high concentrations of alkaline ions (mainly Ca2+) have played an important role to neutralize the acidity of rainwater, leading to the increase of arithmetic pH mean value by 0.5 units since 2002. It is worth noting that the emission of SO2 and NOx from the automobile exhaust is increasing and is becoming another important precursor of acid rain now.  相似文献   

14.
In this work, the influence of South Asian biomass burning emissions on O3 and PM2.5 concentrations over the Tibetan Plateau (TP) is investigated by using the regional climate chemistry transport model WRF-Chem. The simulation is validated by comparing meteorological fields and pollutant concentrations against in situ observations and gridded datasets, providing a clear perspective on the spatiotemporal variations of O3 and PM2.5 concentrations across the Indian subcontinent, including the Tibetan Plateau. Further sensitivity simulations and analyses show that emissions from South Asian biomass burning mainly affect local O3 concentrations. For example, contribution ratios were up to 20% in the Indo-Gangetic Plain during the pre-monsoon season but below 1% over the TP throughout the year 2016. In contrast, South Asian biomass burning emissions contributed more than 60% of PM2.5 concentration over the TP during the pre-monsoon season via significant contribution of primary PM2.5 components (black carbon and organic carbon) in western India that were lofted to the TP by westerly winds. Therefore, it is suggested that cutting emissions from South Asian biomass burning is necessary to alleviate aerosol pollution over the TP, especially during the pre-monsoon season.  相似文献   

15.
Rainwater is a major source of dissolved iron to much of the world's oceans, including regions where iron may be a limiting nutrient for marine phytoplankton primary production. Rainwater iron is therefore potentially important in regulating global photosynthetic uptake of CO2, and hence climate. Two rainwater addition bioassay experiments (2% rain) conducted at the Bermuda Atlantic Time-series Station (BATS) during March 2000 using 50 or 100 nM FeCl2 or FeCl3 in synthetic rain (pH 4.5 H2SO4) showed an increase in chlorophyll a 50% greater than controls after three days. Addition of 20 μM hydrogen peroxide, a typical rainwater concentration at BATS, completely removed the chlorophyll a increase with both forms of iron additions, suggesting stimulation of phytoplankton growth by rainwater iron can be limited by rainwater H2O2. In laboratory experiments using Gulf Stream seawater, iron-enriched (100 nM Fe(III)) synthetic rain was mixed with seawater in a 5% rain 95% seawater ratio. Dissolved iron concentrations increased two times above concentrations predicted based on dilution alone. The increase in soluble iron probably resulted from release from seawater particles and was maintained for more than 24 hours. No increase was observed in controls that did not have iron added to the synthetic rain, or with synthetic rainwater containing both added iron and H2O2. The increase in iron concentration above that predicted by dilution indicates rain may have a larger effect on seawater iron concentrations than that calculated for rainwater iron addition alone.  相似文献   

16.
We investigated the acidity and concentrations of water-soluble ions in PM2.5 aerosol samples collected from an urban site in Beijing and a rural site in Gucheng, Hebei Province from November 2016 to January 2017 to gain an insight into the formation of secondary inorganic species. The average SO42–, NO3–, and NH4+ concentrations were 8.3, 12.5, and 14.1 μg m–3, respectively, at the urban site and 14.0, 14.2, and 24.2 μg m–3, respectively, at the rural site. The nitrogen and sulfur oxidation ratios in urban Beijing were correlated with relative humidity (with correlation coefficient r = 0.79 and 0.67, respectively) and the aerosol loadings. Based on a parameterization model, we found that the rate constant of the heterogeneous reactions for SO2 on polluted days was about 10 times higher than that on clear days, suggesting that the heterogeneous reactions in the aerosol water played an essential role in haze events. The ISORROPIA II model was used to predict the aerosol pH, which had a mean (range) of 5.0 (4.9–5.2) and 5.3 (4.6–6.3) at the urban and rural site, respectively. Under the conditions with this predicted pH value, oxidation by dissolved NO2 and the hydrolysis of N2O5 may be the major heterogeneous reactions forming SO42– and NO3– in haze. We also analyzed the sensitivity of the aerosol pH to changes in the concentrations of SO42–, NO3–, and NH4+ under haze conditions. The aerosol pH was more sensitive to the SO42– and NH4+ concentrations with opposing trends, than to the NO3– concentrations. The sensitivity of the pH was relatively weak overall, which was attributed to the buffering effect of NH3 partitioning.  相似文献   

17.
Based on the CALIPSO (Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observation) Version 4.10 products released on 8 November 2016, the Level 2 (L2) aerosol product over the Tibetan Plateau (TP) is evaluated and the aerosol radiative effect is also estimated in this study. As there are still some missing aerosol data points in the daytime CALIPSO Version 4.10 L2 product, this study re-calculated the aerosol extinction coefficient to explore the aerosol radiative effect over the TP based on the CALIPSO Level 1 (L1) and CloudSat 2B-CLDCLASS-LIDAR products. The energy budget estimation obtained by using the AODs (aerosol optical depths) from calculated aerosol extinction coefficient as an input to a radiative transfer model shows better agreement with the Earth’s Radiant Energy System (CERES) and CloudSat 2B-FLXHR-LIDAR observations than that with the input of AODs from aerosol extinction coefficient from CALIPSO Version 4.10 L2 product. The radiative effect and heating rate of aerosols over the TP are further simulated by using the calculated aerosol extinction coefficient. The dust aerosols may heat the atmosphere by retaining the energy in the layer. The instantaneous heating rate can be as high as 5.5 K day–1 depending on the density of the dust layers. Overall, the dust aerosols significantly affect the radiative energy budget and thermodynamic structure of the air over the TP, mainly by altering the shortwave radiation budget. The significant influence of dust aerosols over the TP on the radiation budget may have important implications for investigating the atmospheric circulation and future regional and global climate.  相似文献   

18.
A comprehensive study on the chemical compositions of rainwater was carried out from Jan. to Dec. in 2008 in Chengdu, a city located on the acid rain control zone of southwest China. All samples were analyzed for pH and major ions (F–, Cl?, NO3?, SO42?, K+, Na+, Ca2+, Mg2+, and NH4+). The pH increased due to the result of neutralization caused by the base ions. It was observed that Ca2+ was the most abundant cation with a VWM value of 196.6 μeq/L (17.3–1568.7 μeq/L), accounting for 49.7% (9.4%–79.2%) of the total cations. SO42? was the most abundant anion with VWM value of 212.8 μeq/L (41.8–1227.6 μeq/L). SO42? and NO3? were dominant among the anions, accounting for 90.4%–99.1% of the total measured anions.The concentrations of NO3? were higher than the most polluted cities abroad, which indicated Chengdu has been a severe polluted city over the world. The high fuel consumption from urbanization and the rapid increase of vehicles resulted in the high emission of SO2 and NOx, which were the precursor of the high concentration of acidic ions NO3? and SO42?. It was the main reason of the severe acid rain in Chengdu.The high concentrations of alkaline ions (mainly Ca2+, NH4+) in Chengdu city atmosphere have played an important role to neutralize the acidity of rainwater and the pH value has increased by 0.7 units since 1989. It is worth noting that the emission of NOx from the automobile exhaust is increased and is becoming the important precursor of acid rain now.  相似文献   

19.
Uptake coefficient of I2 on aqueous surfaces was measured by using an impinging flow method. Dependence of the uptake coefficient on the gas-liquid contact time and pH was investigated. The uptake coefficient was (3.7± 2.0)×10–4 at 120 ms, 293 K and pH = 5.6. In the alkaline region, the uptake coefficient was larger by one order of magnitude than that in the neutral and acidic region. The I2 uptake on KI solutions and synthetic sea water solutions was also measured. According to the analysis by the reactive uptake model, the uptake of I2 was shown to be mainly determined by liquid phase reactions and the accommodation coefficient of I2 on aqueous surfaces was estimated to be 0.01.  相似文献   

20.
以生活污水为供试水样,通过讨论曝气时间、污泥负荷、厌氧好氧时间分配、pH值等因素对SBR反应器中污水COD去除效果的影响进行研究。结果表明:在室温(20±5)℃和进水pH值为6.45—7.55条件下,SBR反应器优化的运行参数为厌氧150 min、曝气120 min、沉淀60 min,污泥负荷为0.049—0.082 kg BOD5/kg MLSS,MLSS 3000—5000 mg.L-1。在此条件下,COD、BOD5、NH3—N、TP和SS的平均去除率分别为85.45%、95.23%、80.25%、95.04%和85.84%,出水水质可满足城镇污水处理厂污染物排放标准(GB18918-2002)一级A。  相似文献   

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