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1.
1 INTRODUCTION Lake Calumet is located 15 miles southeast of downtown Chicago. The geographical boundaries include 130th Street to the south, Stony Island Avenue to the east, an industrial area to the north, and interstate highway I-94 to the west. The major continuous water inflow to the lake is Pullman Creek, a drainage ditch, which carries the runoff from the nearby expressway, industries, and landfills into the lake at the northwest corner. The outlet of the Lake is the Calumet R… 相似文献
2.
Current study presents the application of chemometric techniques to comprehend the interrelations among sediment variables whilst identifying the possible pollution source at Langat River,Malaysia.Surface sediment samples（0-10 cm）were collected at 22 sampling stations and analyzed for total metals（~（48）Cd,~（29）Cu,~（30）Zn,~（82）Pb）,pH,redox potential（Eh）,salinity,electrical conductivity（EC）,loss on ignition（LOI）and cation exchange capacity（CEC）.The principal component analysis（PCA）scrutinized the origin of environmental pollution by various anthropogenic and natural activities：four principal components were obtained with 86.34%（5 cm）and88.34%（10 cm）.Standard,forward and backward stepwise discriminant analysis effectively discriminate 2variables（84.06%）indicating high variation of heavy metals accumulation at both depth.The cluster analysis accounted for high input of Zn and Pb at LA8,LA 10,LA 11 and LA 12 that mergers three（5 cm）and four（10cm）into clusters.This is consistent with the contamination factor（C_1）that shows high Cd（LA 1）and Pb（LA 7,LA 8,LA 10,LA 11 and LA 12）contaminations at 5cm.These indicate that Pb and Zn are the most bioavailable metals in the sediment with significant positive linear relationship at both sediment depths.Therefore,this approach is a good indication of environmental pollution status that transfers new findings on the assessment of heavy metals by interpreting large complex datasets and predicting the fate of heavy metals in the sediment. 相似文献
3.
Artificially triggered lightning and its characteristic discharge parameters in two severe thunderstorms 总被引：2，自引：0，他引：2
Qie XiuShu Zhang QiLin Zhou YunJun Feng GuiLi Zhang TingLong Yang Jing Kong XiangZhen Xiao QingFu Wu ShuJun 《中国科学D辑(英文版)》2007,50(8):1241-1250
The lightning-induced-damages in the mid-latitude regions are usually caused during severe thunder-storms. But the discharge parameters of natural lightning are difficult to be measured. Five lightning flashes have been artificially triggered with the rocket-wire technique during the passage of two severe thunderstorms. The discharge current and close electric field of return stroke in artificially triggered lightning have been obtained in microsecond time resolution by using current measuring systems and electric field change sensors. The results show that the five triggered lightning flashes include 1 to 10 return strokes, and the average return stroke current is 11.9 kA with a maximum of 21.0 kA and a mini-mum of 6.6 kA, similar to the subsequent return strokes in natural lightning. The half peak width of the current waveform is 39 μs, which is much larger than the usual result. The peak current of stroke Ip (kA) and the neutralized charge Q(C) has a relationship of Ip = 18.5Q0.65. The radiation field of return stroke is 5.9 kV·m-1 and 0.39 kV·m-1 at 60 m and 550 m, respectively. The radiation field decreases as r -1.119 with increase of horizontal distance r from the discharge channel. Based on the well-accepted transmission line model, the speed of return stroke is estimated to be about 1.4×108 m·s-1, with a variation range of (1.1―1.6)×108 m·s-1. Because of the similarities of the triggered lightning and natural lightning, the results in this article can be used in the protection design of natural lightning. 相似文献
4.
The diffusion and adsorption of two common volatile organic compounds, i. e., methanol and benzene, in different zeolite pellets were studied experimentally by using the single pellet moment technique. The experiments were conducted in a one‐sided single pellet adsorption cell at different temperatures in the range between 303 and 343 K. The results showed that both volatile organic tracers were adsorbed reversibly onto all zeolite samples. The overall adsorption equilibrium constants of both volatile organic compounds decreased with increasing temperature. The adsorption of the tracers onto the zeolite samples were found to increase in the order of NaY > clinoptilolite > 4A. In the range between 303 and 343 K, the adsorption constants of benzene range from 10.51 to 5.52 for zeolite 4A, from 11.90 to 6.37 for clinoptilolite and from 20.32 to 9.82 for NaY. The adsorption constants of methanol range from 19.05 to 8.26 for zeolite 4A, from 38.40 to 9.12 for clinoptilolite and from 74.21 to 14.70 for NaY at temperatures between 303 and 333 K. The effective diffusivities for benzene varied from 2.20·10–6 to 13.01·10–6 m2/s, whereas for methanol, they varied from 9.80·10–6 to 15.60·10–6 m2/s at the temperatures studied. 相似文献
5.
In situ measurements of lunar surface brightness temperatures made as a part of the Apollo Lunar Surface Experiments Package at the Apollo 15 Hadley Rille landing site are reported. Data derived from 5 thermocouples of the Heat Flow Experiment, which are lying on or just above the surface, are used to examine the thermal properties of the upper 15 cm of the lunar regolith using eclipse and nighttime cool-down temperatures. Application of finite-difference techniques in modeling the lunar soil shows the thermocouple data are best fit by a model consisting of a low-density and low-thermal conductivity surface layer approximately 2 cm thick overlying a region increasing in conductivity and density with depth. Conductivities on the order of 1 × 10?5 W/cm-°K are postulated for the upper layer, with conductivity increasing to the order of 1 × 10?4 W/cm-°K at depths exceeding 20 cm. An increase in mean temperature with depth indicates that the ratio of radiative to conductive transfer at 350°K is 2.7 for at least the upper few centimeters of lunar soil; this value is nearly twice that measured for returned lunar fines. The thermal properties model deduced from Apollo 15 surface temperatures is consistent with earth-based microwave observations if electrical properties measured on returned lunar fines are assumed. 相似文献
6.
A. B. Struminsky 《Geomagnetism and Aeronomy》2013,53(7):843-851
Giant X-ray events (>X17) in the 23rd solar cycle (October 28 and November 4, 2003, and September 7, 2005) are considered, which were almost completely observed in hard X rays (>150 keV) from the INTEGRAL satellite and partly from the RHESSI satellite. These events are compared with two events completely observed from the RHESSI satellite (X8.2 on November 2, 2003, and X7.1 on January 20, 2005). Time profiles of the plasma temperature, calculated from the GOES data on soft X rays during these events, have similar structures. This allowed us to choose a zero time point in each event and compare the dynamics of their evolution. Nonthermal radiation began approximately 10 min before the zero time point (preflare phase). During about 20 min after the zero point, bursts of nonthermal radiation were observed in all the three events, which pointed to several episodes of electron acceleration with variable spectra and plasma heating with different efficiency. It is shown that giant events are characterized by a large emission measure and a relatively low temperature of the flare plasma but not intensive acceleration processes. Observations of γ radiation from the decay of π0-mesons show that protons are accelerated to relativistic energies 4 min after the chosen zero point. 相似文献
7.
Lightning Applications in Weather and Climate Research 总被引：1，自引：0，他引：1
Colin G. Price 《Surveys in Geophysics》2013,34(6):755-767
Thunderstorms, and lightning in particular, are a major natural hazard to the public, aviation, power companies, and wildfire managers. Lightning causes great damage and death every year but also tells us about the inner working of storms. Since lightning can be monitored from great distances from the storms themselves, lightning may allow us to provide early warnings for severe weather phenomena such as hail storms, flash floods, tornadoes, and even hurricanes. Lightning itself may impact the climate of the Earth by producing nitrogen oxides (NOx), a precursor of tropospheric ozone, which is a powerful greenhouse gas. Thunderstorms themselves influence the climate system by the redistribution of heat, moisture, and momentum in the atmosphere. What about future changes in lightning and thunderstorm activity? Many studies show that higher surface temperatures produce more lightning, but future changes will depend on what happens to the vertical temperature profile in the troposphere, as well as changes in water balance, and even aerosol loading of the atmosphere. Finally, lightning itself may provide a useful tool for tracking climate change in the future, due to the nonlinear link between lightning, temperature, upper tropospheric water vapor, and cloud cover. 相似文献
8.
9.
利用无狭缝红外光谱仪, 获得山东地区闪电放电过程760~970 nm范围的近红外光谱.光谱特征分析得出: 近红外光谱主要是峰值电流之后、放电后期的辐射, 谱线主要是中性原子的贡献.首次讨论了放电后期的通道温度和光谱总强度沿放电通道的演化特征.结果表明, 通道温度较回击电流上升至峰值阶段降低, 约为16000 K; 不同闪电的光谱结构、通道温度差异不大, 反映了放电等离子体复合阶段的特性; 地闪通道的温度和光谱总强度沿放电通道略呈单调变化趋势, 接地点附近最大; 云闪通道的温度和光谱总强度沿放电通道非单调变化, 在通道的拐弯、分叉以及结点附近发生突变. 相似文献
10.
We studied the change of magnetic behaviour upon laboratory heating of altered mid-ocean ridge basalt (MORB) samples in the age range of 16-35 Ma to determine the influence of titanomaghemite inversion on the thermal demagnetisation of natural remanent magnetisation (NRM) of these basalts. MORB samples were heated to successively higher temperatures and at the same time the temperature dependence of either saturation magnetisation or NRM was monitored continuously. After each heating step, hysteresis loops and remanent magnetisation curves between 10 K and room temperature were measured. With this procedure, it is shown that the dominant magnetic remanence carrier in our MORB samples is cation deficient titanomaghemite. Moreover, it is demonstrated that the titanomaghemite is gradually changing to a Ti-poor titanomagnetite as the final inversion product. During inversion, both the Curie temperature as well as the maximum unblocking temperature of the NRM are gradually increasing. We show that the paradox of unblocking temperatures above the Curie temperatures often observed for altered MORBs is an artefact of this gradual, heating induced inversion process. 相似文献
11.
Lightning discharges monitored by the SAFIR network system in Poland have been additionally identified over the 100×100 km
area near Warsaw by single-point independent recordings of electric field and Maxwell current rapid changes. The data collected
in summer thunderstorm days of 2002 showed some untypical properties of the lightning discharges which are rarely observed.
Especially remarkable was a number of ground multi-stroke flashes with the return strokes (RS) which transported to the earth
charges of opposite signs. Bipolar flashes (BF) of this kind were mostly involved in the events in which the nearby intracloud
(ic) and cloud-to-ground (c-g) discharges were very closely associated in time. Events of such a close collocation of two
different types of lightning discharges, previously called the complex lightning discharge events (CLDE), were quite often
observed during summer thunderstorms in Poland.
The events of this kind, i.e. 8 flashes, identified by the SAFIR detection system as BF’s present the multiple stroke flashes
of the mean horizontal separation distance between striking points of particular RS equal to (2.8 ± 2.1) km and of the mean
time interval between strokes of (46.8 ± 74.4) ms. The time separation between the observed BF and the adjacent ic flashes
was from 0.1 to 335 ms, and horizontal separation distance between them ranged from 1.8 to 14.5 km. The multiplicity of the
recorded BF’s ranged from 2 to 4 strokes. Four of these BF’s followed the ic discharge, but the other three preceded the ic
and one was alone with no close ic. 相似文献
12.
During the design of a natural gradient tracer experiment, it was noticed that the hydraulic gradient was too small to measure reliably on an approximately 500-m(2) site. Additional wells were installed to increase the monitored area to 26,500 m(2), and wells were instrumented with pressure transducers. The resulting monitoring system was capable of measuring heads with a precision of +/-1.3 x 10(-2) m. This measurement error was incorporated into Monte Carlo calculations, in which only hydraulic head values were varied between realizations. The standard deviation in the estimated gradient and the flow direction angle from the x-axis (east direction) were calculated. The data yielded an average hydraulic gradient of 4.5 x 10(-4)+/-25% with a flow direction of 56 degrees southeast +/-18 degrees, with the variations representing 1 standard deviation. Further Monte Carlo calculations investigated the effects of number of wells, aspect ratio of the monitored area, and the size of the monitored area on the previously mentioned uncertainties. The exercise showed that monitored areas must exceed a size determined by the magnitude of the measurement error if meaningful gradient estimates and flow directions are to be obtained. The aspect ratio of the monitored zone should be as close to 1 as possible, although departures as great as 0.5 to 2 did not degrade the quality of the data unduly. Numbers of wells beyond three to five provided little advantage. These conclusions were supported for the general case with a preliminary theoretical analysis. 相似文献
13.
Variability and comparison of hyporheic water temperatures and seepage fluxes in a small Atlantic salmon stream 总被引：2，自引：0，他引：2
Ground water discharge is often a significant factor in the quality of fish spawning and rearing habitat and for highly biologically productive streams. In the present study, water temperatures (stream and hyporheic) and seepage fluxes were used to characterize shallow ground water discharge and recharge within thestreambed of Catamaran Brook, a small Atlantic salmon (Salmo salar) stream in central New Brunswick, Canada. Three study sites were instrumented using a total of 10 temperature sensors and 18 seepage meters. Highly variable mean seepage fluxes, ranging from 1.7 x 10(-4) to 2.5 cm3 m(-2) sec(-1), and mean hyporheic water temperatures, ranging from 10.5 degrees to 18.0 degrees C, at depths of 20 to 30 cm in the streambed were dependent on streambed location (left versus right stream bank and site location) and time during the summer sampling season. Temperature data were usefulfor determining if an area of the streambed was under discharge (positive flux), recharge (negative flux), or parallel flow (no flux) conditions and seepage meters were used to directly measure the quantity of water flux. Hyporheic water temperature measurements and specific conductance measurements of the seepage meter sample water, mean values ranging from 68.8 to 157.9 microS/cm, provided additional data for determining flux sources. Three stream banks were consistently under discharge conditions, while the other three stream banks showed reversal from discharge to recharge conditions over the sampling season. Results indicate that the majority of the water collected in the seepage meters was composed of surface water. The data obtained suggests that even though a positive seepage flux is often interpreted as ground water discharge, this discharging water may be of stream water origin that has recently entered the hyporheic zone.The measurement of seepage flux in conjunction with hyporheic water temperature or other indicators of water origin should be considered when attempting to quantify the magnitude of exchange and the source of hyporheic water. 相似文献
14.
The Physics of Lightning 总被引：1，自引：0，他引：1
V. A. Rakov 《Surveys in Geophysics》2013,34(6):701-729
An overview of the physics of cloud-to-ground lightning is given, including its initiation, propagation, and attachment to ground. Discharges artificially initiated (triggered) from natural thunderclouds using the rocket-and-wire technique are discussed with a view toward studying properties of natural lightning. Both conventional and runaway breakdown mechanisms of lightning initiation in thunderclouds are reviewed, as is the role of the lower positive charge region in facilitating different types of lightning. New observations of negative-leader stepping and its attachment to ground are compared to similar processes in long laboratory sparks. The mechanism and parameters of compact intracloud lightning discharges that are thought to be the most intense natural producers of HF-VHF (3–300 MHz) radiation on Earth are reviewed. The M-component mode of charge transfer to ground and its difference from the leader/return-stroke mode are discussed. Lightning interaction with the ionosphere and the production of energetic radiation (X-rays and gamma radiation) by cloud-to-ground leaders are considered. 相似文献
15.
Lightning and electrification at volcanoes are important because they represent a hazard in their own right, they are a component
of the global electrical circuit, and because they contribute to ash particle aggregation and modification within ash plumes.
The role of water substance (water in all forms) in particular has not been well studied. Here data are presented from a comprehensive
global database of volcanic lightning. Lightning has been documented at 80 volcanoes in association with 212 eruptions. The
Volcanic Explosivity Index (VEI) could be determined for 177 eruptions. Eight percent of VEI = 3–5 eruptions have reported
lightning, and 10% of VEI = 6, but less than 2% of those with VEI = 1–2. These findings suggest consistent reporting for larger
eruptions but either less lightning or possible under-reporting for small eruptions. Ash plume heights (142 observations)
show a bimodal distribution with main peaks at 7–12 km and 1–4 km. The former are similar to heights of typical thunderstorms
and suggest involvement of water substance, whereas the latter suggest other factors contributing to electrical behavior closer
to the vent. Reporting of lightning is more common at night (56%) and less common in daylight (44%). Reporting also varied
substantially from year to year, suggesting that a more systematic observational strategy is needed. Several weak trends in
lightning occurrence based on magma composition were found. The bimodal ash plume heights are obvious only for andesite to
dacite; basalt and basaltic-andesite evenly span the range of heights; and rhyolites are poorly represented. The distributions
of the latitudes of volcanoes with lightning and eruptions with lightning roughly mimic the distribution of all volcanoes,
which is generally flat with latitude. Meteorological lightning, on the other hand, is common in the tropics and decreases
markedly with increasing latitude as the ability of the atmosphere to hold water decreases poleward. This finding supports
the idea that if lightning in large (deep) eruptions depends on water substance, then the origin of the water is primarily
magma and not entrainment from the surrounding atmosphere. Seasonal effects show that more eruptions with lightning were reported
in winter (bounded by the respective autumnal and vernal equinoxes) than in summer. This result also runs counter to the expectations
based on entrainment of local water vapor. 相似文献
16.
Joseph Holden Catherine S. Moody T. Edward Turner Rebecca McKenzie Andy J. Baird Mike F. Billett Pippa J. Chapman Kerry J. Dinsmore Richard P. Grayson Roxane Andersen Clare Gee Gemma Dooling 《水文研究》2018,32(4):550-561
Perennial pools are common natural features of peatlands, and their hydrological functioning and turnover may be important for carbon fluxes, aquatic ecology, and downstream water quality. Peatland restoration methods such as ditch blocking result in many new pools. However, little is known about the hydrological function of either pool type. We monitored six natural and six artificial pools on a Scottish blanket peatland. Pool water levels were more variable in all seasons in artificial pools having greater water level increases and faster recession responses to storms than natural pools. Pools overflowed by a median of 9 and 54 times pool volume per year for natural and artificial pools, respectively, but this varied widely because some large pools had small upslope catchments and vice versa. Mean peat water‐table depths were similar between natural and artificial pool sites but much more variable over time at the artificial pool site, possibly due to a lower bulk specific yield across this site. Pool levels and pool‐level fluctuations were not the same as those of local water tables in the adjacent peat. Pool‐level time series were much smoother, with more damped rainfall or recession responses than those for peat water tables. There were strong hydraulic gradients between the peat and pools, with absolute water tables often being 20–30 cm higher or lower than water levels in pools only 1–4 m away. However, as peat hydraulic conductivity was very low (median of 1.5 × 10?5 and 1.4 × 10?6 cm s?1 at 30 and 50 cm depths at the natural pool site), there was little deep subsurface flow interaction. We conclude that (a) for peat restoration projects, a larger total pool surface area is likely to result in smaller flood peaks downstream, at least during summer months, because peatland bulk specific yield will be greater; and (b) surface and near‐surface connectivity during storm events and topographic context, rather than pool size alone, must be taken into account in future peatland pool and stream chemistry studies. 相似文献
17.
连续重力观测和GPS的技术结合能够监测到物质迁移和地壳垂直形变之间的量化关系.和相对重力测量以及绝对重力测量技术相比,其避免了时间分辨率和观测精度低,无法精细描述观测周期内的物质迁移过程问题.本文利用武汉九峰地震台超导重力仪SGC053超过13000 h连续重力观测数据;同址观测的绝对重力仪观测结果;气压数据;周边GPS观测结果;GRACE卫星的时变重力场;全球水储量模型等资料,采用同址观测技术、调和分析法、相关分析方法在扣除九峰地震台潮汐、气压、极移和仪器漂移的基础上,利用重力残差时间序列和GPS垂直位移研究物质迁移和地壳垂直形变之间的量化关系.结果表明:在改正连续重力观测数据的潮汐、气压、极移的影响后,不仅准确观测到2009年的夏秋两季由于水负荷引起的约(6~8)×10-8m·s-2短期的重力变化.而且在扣除2.18×10-8(m·s-2)/a仪器漂移和水负荷的影响后,验证了本地区长短趋势垂直形变和重力变化之间具有一致的负相关性规律.同时长趋势表明该地区地壳处于下沉,重力处于增大过程,增加速率约为1.79×10-8(m·s-2)/a.武汉地区重力梯度关系约为-354×10-8(m·s-2)/m. 相似文献
18.
YingXing Guo DuoJun Wang YaoLin Shi YongSheng Zhou YongSheng Dong Cai Li 《中国科学:地球科学(英文版)》2014,57(9):2071-2078
The electrical conductivity of Tibetan eclogite was investigated at pressures of 1.5–3.5 GPa and temperatures of 500–803 K using impedance spectroscopy within a frequency range of 10-1–106 Hz. The electrical conductivity of eclogite increases with increasing temperature(which can be approximated by the Arrhenius equation), and is weakly affected by pressure. At each tested pressure, the electrical conductivity is weakly temperature dependent below ~650 K and more strongly temperature dependent above ~650 K. The calculated activation energies and volumes are 44±1 kJ/mol and-0.6±0.1 cm3/mol for low temperatures and 97±3 kJ/mol and-1.2±0.2 cm3/mol for high temperatures, respectively. When applied to the depth range of 45–100 km in Tibet, the laboratory data give conductivities on the order of 10-1.5–10-4.5 S/m, within the range of geophysical conductivity profiles. 相似文献
19.
Over the last 50 years, about one-third of the original area of the seagrass Posidonia australis has been lost from Port Hacking (Australia) due to anthropogenic impacts. To assess the feasibility of restoring these seagrass meadows, healthy Posidonia rhizomes were transplanted to four impact sites and one control site. Survival rates of transplanted shoots were monitored in situ bi-monthly for 16 months and, at the end of the experiment, rhizome growth, shoot growth, shoot production and growth architecture were assessed by harvesting tagged rhizomes. A total of 575 shoots were transplanted and after 16 months 650 shoots were present. Four of the five sites exhibited high survival rates in the short term (less than six months) but only two impact sites, Burraneer Bay (BB) and Red Jacks Point (RJP), and the control site (CS) survived to the end of the experiment. Total number of shoots increased by 61% at CS, tripled at BB, but decreased by 22% at RJP. Rhizome growth varied significantly between site, from 22.3 +/- 1.4 cm yr(-1) at BB to 9.1 +/- 1.0 cm yr(-1) at RJP. Shoot growth did not vary significantly between sites and was approximately 2-3 cm yr(-1). At BB and CS there was substantial colonisation of the surrounding substrate, with new rhizomes, orthotropic shoots and transitional shoots produced. Survival of transplants appeared to depend on whether the factors that had caused the original loss of Posidonia were still operating in the study area. 相似文献
20.
依据在中国西藏高原地区得到的6幅云闪放电通道的光谱,由谱线波长、相对强度和跃迁几率等信息,结合等离子体理论,计算了云闪放电通道的温度和电子密度;进而,利用Saha方程、电荷守恒和粒子数守恒方程,得到了粒子处于各电离级上的数密度、通道质量密度、压强和平均电离度等参数,并对云闪通道内部粒子数分布特点进行了分析.结果表明,与地闪回击通道类似,云闪通道接近于完全电离,通道内部以单次电离的离子为主,且NII离子数密度最高.具有较高温度的通道位置处,中性和一次以上电离离子数密度的绝对值和相对值都较高,但是,不同温度下NII、OII、ArII粒子的相对浓度变化不大.与地闪回击通道不同,云闪同一放电通道内不同位置处粒子数密度差异较大,且沿通道没有显示规律性变化,通道压强从零点几到几兆帕. 相似文献