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1.
Wind Characteristics of Mesquite Streets in the Northern Chihuahuan Desert, New Mexico, USA 总被引:2,自引:0,他引:2
Past research has shown that the most important areas for active sand movement in the northern part of the Chihuahuan Desert
are mesquite-dominated desert ecosystems possessing sandy soil texture. The most active sand movement in the mesquite-dominated
ecosystems has been shown to take place on elongated bare soil patches referred to as “streets”. Aerodynamic properties of
mesquite streets eroded by wind should be included in explaining how mesquite streets are more emissive sand sources than
surrounding desert land. To understand the effects of wind properties, we measured them at two flat mesquite sites having
highly similar soil textures but very different configurations of mesquite. The differences in wind properties at the two
sites were caused by differences of size, orientation, and porosity of the mesquite, along with the presence of mesquite coppice
dunes (sand dunes stabilized by mesquites growing in the dune and on its surface) found only at one of the two sites. Wind
direction, u* (friction velocity), z0 (aerodynamic roughness height) and D (zero plane displacement height) were estimated for 15-m tower and 3-m mast data. These aerodynamic data allowed us to distinguish
five categories with differing potentials for sediment transport. Sediment transport for the five categories varied from unrestricted,
free transport to virtually no transport caused by vegetation protection from wind forces. In addition, “steering” of winds
below the level of the tops of mesquite bushes and coppice dunes allowed longer parallel wind durations and increased wind
erosion for streets that aligned roughly SW–NE.
U.S. Government right to retain a non-exclusive royalty-free licence in and to any copyright is acknowledged. 相似文献
2.
Geographic patterns of non-carpeted floor dust loading in Syracuse, New York (USA) homes 总被引:1,自引:0,他引:1
Johnson DL Hunt A Griffith DA Hager JM Brooks J Stellalevinsohn H Lanciki A Lucci R Prokhorova D Blount SL 《Environmental geochemistry and health》2009,31(3):353-363
Residential floor dust loading was measured on the smooth floor surface of 488 houses in Syracuse, New York, during the summers
of 2003 and 2004. Using U.S. Environmental Protection Agency (EPA) wipe methods, pre-weighed Ghost Wipes, Lead Wipes, or Whatman
Filters were employed to collect duplicate samples from (predominantly) kitchens. The collection efficiency of the various
media was determined from multiple wipe tests and side-by-side comparisons. The results were normalized and aggregated at
the census tract level to determine whether spatial patterns of dust loading could be observed. Loading was found to be log-normally
distributed, with a geometric mean value of 0.311 g m−2 (29 mg of dust per square foot of floor); 95% of the observations fell in the range of 0.042–2.330 g m−2 (4–216 mg foot−2). The sampling for floor dust loading shows some bias for day of the week in which visits to the residential properties were
made. After a first-order correction for this effect, results were aggregated by census tract and mapped in a geographic information
system (GIS); strong spatial patterns can be identified in an inverse distance weighted mapping. The geographic patterns exhibit
a strong correlation with socio-economic/demographic covariates extracted from the 2000 census summaries. Dust mass on the
floors is positively correlated with renter-occupied properties and family size; it is negatively correlated with measures
of household income. 相似文献
3.
Alecos Demetriades Xiangdong Li Michael H. Ramsey Iain Thornton 《Environmental geochemistry and health》2010,32(6):529-552
In the Lavrion urban area study, Hellas, a five-step sequential extraction method was applied on samples of ‘soil’ (n = 224), affected by long-term mining and metallurgical activities, and house dust (n = 127), for the purpose of studying the potential bioaccessibility of lead and other metals to humans. In this paper, the
Pb concentrations in soil and house dust samples are discussed, together with those in rocks and children’s blood. Lead is
mainly associated with the carbonate, Fe–Mn oxides and residual fractions in soil and house dust. Considering the very low
pH of gastric fluids (1–3), a high amount of metals, present in soil (810–152,000 mg/kg Pb) and house dust (418–18,600 mg/kg Pb),
could be potentially bioaccessible. Consequently, children in the neighbourhoods with a large amount of metallurgical processing
wastes have high blood-Pb concentrations (5.98–60.49 μg/100 ml; median 17.83 μg/100 ml; n = 235). It is concluded that the Lavrion urban and sub-urban environment is extremely hazardous to human health, and the
Hellenic State authorities should urgently tackle this health-related hazard in order to improve the living conditions of
local residents. 相似文献
4.
Susana Torno Javier Toraño Mario Menendez Malcolm Gent Cristina Allende 《Environmental Fluid Mechanics》2011,11(1):99-112
Landfill sites have been the most common way of eliminating solid urban waste, as well as that of public and mining wastes.
Landfill sites are a constant source of environmental pollution and wind is the most important contributing factor to air
pollution, due to the erosion which it produces over the landfill site surfaces, transporting dust away from the source point.
This causes serious risks for human health and general dirt in the surrounding areas of the landfill site. The result of dust
air pollution produced in a landfill site is analysed through CFD3D (Computational Fluid Dynamics) by joining the LIDAR (Light
Detection and Ranging) technique and Ansys CFX 10.0 software. The CFD simulations determine the wind velocity distribution
on the landfill site surface and the different particle threshold friction velocities which determine the dust emission in
multiphase simulations (air-particles). These simulations are validated from field data obtained in three measurement programmes
for each type of landfill site surface treatment which has been studied. It was determined that the superficial landfill site
treatment with the lowest air pollution is tall grass and bushes. The methodology used can be applied to the dust emission
calculation in the design or evaluation of other landfill sites. 相似文献
5.
6.
Whilst a range of animals have been shown to respond behaviourally to components of the Earth’s magnetic field, evidence of
the value of this sensory perception for small animals advected by strong flows (wind/ocean currents) is equivocal. We added
geomagnetic directional swimming behaviour for North Atlantic loggerhead turtle hatchlings (Caretta
caretta) into a high-resolution (1/4°) global general circulation ocean model to simulate 2,925-year-long hatchling trajectories
comprising 355,875 locations. A little directional swimming (1–3 h per day) had a major impact on trajectories; simulated
hatchlings travelled further south into warmer water. As a result, thermal elevation of hatchling metabolic rates was estimated
to be between 63.3 and 114.5% after 220 days. We show that even small animals in strong flows can benefit from geomagnetic
orientation and thus the potential implications of directional swimming for other taxa may be broad. 相似文献
7.
The sea cucumber, Cucumaria frondosa, is a benthic suspension feeder that captures food particles on its tentacles and then inserts them into its mouth one at
a time. Previous studies have suggested that tentacle insertion rate (TIR) could be a useful indicator of food intake. The
present study determined whether flow velocity affects TIR and whether TIR is a good indicator of ingestion. Video observations
of sea cucumbers in Passamaquoddy Bay (45°01.70N, 66°55.74W) in August 1995 showed that TIRs increased with velocities up
to 55 cm s−1 and decreased steadily at flows above that up to 130 cm s−1. In October 2006, laboratory flume studies were carried out on specimens collected from the same site in the previous August.
Temperature and salinity (12°C and 32) in the flume were the same as in the field at the time of collection. There was high
individual variation in feeding behavior at free-stream velocities of 4–40 cm s−1 and TIR was independent of flow. As the number of tentacle insertions increased in the flume experiments, the amount of chloropigments
in the digestive tracts of the sea cucumbers also increased. This suggests that TIR, which can be measured non-intrusively
using remote video techniques, could be a good indicator of feeding behavior and ingestion in C. frondosa. 相似文献
8.
Fernández-Caliani JC 《Environmental geochemistry and health》2012,34(1):123-139
The peri-urban soils of Huelva, one of the first industrial cities in Spain, are subject to severe pollution problems primarily
due to past poor management of industrial wastes and effluents. In this study, soil cores were collected in seven sites potentially
contaminated with toxic chemicals arising from multiple anthropogenic sources, in order to identify trace elements of concern
and to assess human health risks associated with them. In most soil core samples, total concentrations of As (up to 4,390 mg kg−1), Cd (up to 12.9 mg kg−1), Cu (up to 3,162 mg kg−1), Pb (up to 6,385 mg kg−1), Sb (up to 589 mg kg−1) and Zn (up to 4,874 mg kg−1) were by more than one order of magnitude greater than the site-specific reference levels calculated on the basis of regional
soil geochemical baselines. These chemicals are transferred from the hazardous wastes, mainly crude pyrite and roasted pyrite
cinders, to the surrounding soils by acid drainage and atmospheric deposition of wind-blown dust. Locally, elevated concentrations
of U (up to 96.3 mg kg−1) were detected in soils affected by releases of radionuclides from phosphogypsum wastes. The results of the human health
risk-based assessment for the hypothetical exposure of an industrial worker to the surface soils indicate that, in four of
the seven sites monitored, cancer risk due to As (up to 4.4 × 10−5) is slightly above the target health risk limit adopted by the Spanish legislation (1 × 10−5). The cumulative non-carcinogenic hazard index ranged from 2.0 to 12.2 indicating that there is also a concern for chronic
toxic effects from dermal contact with soil. 相似文献
9.
Incidental soil ingestion is a common contaminant exposure pathway for humans, notably children. It is widely accepted that
the inclusion of total soil metal concentrations greatly overestimates the risk through soil ingestion for people due to contaminant
bioavailability constraints. The assumption also assumes that the contaminant distribution and the bioaccessible fraction
is consistent across all particle sizes. In this study, we investigated the distribution of arsenic across five particle size
fractions as well as arsenic bioaccessibility in the <250-, <100-, <10- and 2.5-μm soil particle fractions in 50 contaminated
soils. The distribution of arsenic was generally uniform across the larger particle size fractions but increased markedly
in the <2.5-μm soil particle fraction. The marked increase in arsenic concentration in the <2.5-μm fraction was associated
with a marked increase in the iron content. Arsenic bioaccessibility, in contrast, increased with decreasing particle size.
The mean arsenic bioaccessibility increased from 25 ± 16% in the <250-μm soil particle fraction to 42 ± 23% in the <10-μm
soil particle fraction. These results indicate that the assumption of static arsenic bioaccessibility values across particle
size fractions should be reconsidered if the ingested material is enriched with small particle fractions such as those found
in household dust. 相似文献
10.
Residents in older homes may experience increased lead (Pb) exposures due to release of lead from interior paints manufactured
in past decades, especially pre-1960s. The objective of the study was to determine the speciation of Pb in settled dust from
an urban home built during WWII. X-ray absorption near-edge structure (XANES) and micro-X-ray diffraction (XRD) analyses were
performed on samples of paint (380–2,920 mg Pb kg−1) and dust (200–1,000 mg Pb kg−1) collected prior to renovation. All dust samples exhibited a Pb XANES signature similar to that of Pb found in paint. Bulk
XANES and micro-XRD identified Pb species commonly found as white paint pigments (Pb oxide, Pb sulfate, and Pb carbonate)
as well as rutile, a titanium-based pigment, in the <150 μm house dust samples. In the dust fraction <36 μm, half of the Pb
was associated with the Fe-oxyhydroxides, suggesting additional contribution of outdoor sources to Pb in the finer dust. These
results confirm that old paints still contribute to Pb in the settled dust for this 65-year-old home. The Pb speciation also
provided a clearer understanding of the Pb bioaccessibility: Pb carbonate > Pb oxide > Pb sulfate. This study underscores
the importance of taking precautions to minimize exposures to Pb in house dust, especially in homes where old paint is exposed
due to renovations or deterioration of painted surfaces. 相似文献
11.
We investigated the spatial distribution of Pb in soil and dust samples collected from 54 sites in Shenyang city, Liaoning province, Northeast China. Soil background Pb concentration was 22 mg kg−1 and control values from non-industrial areas were 33 mg kg−1 for soil and 38 mg kg−1 for dust. Soil Pb concentrations varied widely, ranging from 26 to 2911 mg kg−1, with a mean concentration of 200 mg kg−1, 9 times the background value and 6 times the control value. There was great variation in soil Pb, with a coefficient of variation (CV) of 1.06 and a standard deviation (SD) of 212 mg kg−1. Dust Pb concentrations fluctuated from 20 to 2810 mg kg−1, with a mean value of 220 mg kg−1, almost 6 times the control value. No significant differences in distribution were observed between soil Pb and dust Pb. The highest Pb concentration was observed in Tiexi district in an industrial area. Soil Pb concentration decreased with depth and with distance from the pollution source. Lead concentrations initially changed little but then decreased with distance from the roadside, and were generally higher on the east side of roads than on the west. Lead contents in different categories of urban area differed substantially with dust and soil Pb concentrations decreasing in the sequence: industrial >business >mixed (residential, culture and education)> reference areas. 相似文献
12.
In the indoor environment, settled surface dust often functions as a reservoir of hazardous particulate contaminants. In many
circumstances, a major contributing source to the dust pool is exterior soil. Young children are particularly susceptible
to exposure to both outdoor derived soil and indoor derived dust present in the indoor dust pool. This is because early in
life the exploratory activities of the infant are dominated by touching and mouthing behavior. Inadvertent exposure to dust
through mouth contact and hand-to-mouth activity is an inevitable consequence of infant development. Clean-up of indoor dust
is, in many circumstances, critically important in efforts to minimize pediatric exposure. In this study, we examine the efficiency
of vacuum cleaner removal of footwear-deposited soil on vinyl floor tiles. The study utilized a 5 × 10 foot (c. 152.5 × 305 cm)
test surface composed of 1-foot-square (c. 30.5 × 30.5 cm) vinyl floor tiles. A composite test soil with moderately elevated
levels of certain elements (e.g., Pb) was repeatedly introduced onto the floor surface by footwear track-on. The deposited
soil was subsequently periodically removed from randomly selected tiles using a domestic vacuum cleaner. The mass and loading
of soil elements on the tiles following vacuuming were determined both by wet wipe collection and by subsequent chemical analysis.
It was found that vacuum cleaner removal eliminated much of the soil mass from the floor tiles. However, a small percentage
of the mass was not removed and a portion of this residual mass could be picked up by moistened hand-lifts. Furthermore, although
the post-vacuuming tile soil mass was sizably reduced, for some elements (notably Pb) the concentration in the residual soil
was increased. We interpret this increased metal concentration to be a particle size effect with smaller particles (with a
proportionately higher metal content) remaining in situ after vacuuming. 相似文献
13.
On the heating environment in street canyon 总被引:1,自引:1,他引:0
This study investigates the impact of building aspect ratio (building-height-to-street-canyon-width-ratio), wind speed and
surface and air-temperature difference (Δθs−a) on the heating environment within street canyon. The Reynolds-averaged Navier-Stokes (RANS) and energy transport equations
were solved with Renormalization group (RNG) theory version of k-e{\varepsilon} turbulence model. The validation process demonstrated that the model could be trusted for simulating air-temperature and
velocity trends. The temperature and velocity patterns were discussed in idealized street canyons of different aspect ratios
(0.5–2.0) with varying ambient wind speeds (0.5–1.5 m/s) and Δθs−a (2–8 K). Results show that air-temperatures are directly proportional to bulk Richardson number (R
b
) for all but ground heating situation. Conversely, air-temperatures increase significantly across the street canyon with
a decrease in ambient wind speed; however, the impact of Δθs−a was negligible. Clearly, ambient wind speed decreases significantly as it passes over higher AR street canyons. Notably,
air-temperatures were the highest when the windward wall was heated and the least during ground heating. Conversely, air-temperatures
were lower along the windward side but higher within the street canyon when the windward wall was heated. 相似文献
14.
Simmons RW Noble AD Pongsakul P Sukreeyapongse O Chinabut N 《Environmental geochemistry and health》2009,31(1):71-79
Research undertaken over the last 40 years has identified the irrefutable relationship between the long-term consumption of
cadmium (Cd)-contaminated rice and human Cd disease. In order to protect public health and livelihood security, the ability
to accurately and rapidly determine spatial Cd contamination is of high priority. During 2001–2004, a General Linear Regression
Model Irr-Cad was developed to predict the spatial distribution of soil Cd in a Cd/Zn co-contaminated cascading irrigated
rice-based system in Mae Sot District, Tak Province, Thailand (Longitude E 98°59′–E 98°63′ and Latitude N 16°67′–16°66′).
The results indicate that Irr-Cad accounted for 98% of the variance in mean Field Order total soil Cd. Preliminary validation
indicated that Irr-Cad ‘predicted’ mean Field Order total soil Cd, was significantly (p < 0.001) correlated (R
2 = 0.92) with ‘observed’ mean Field Order total soil Cd values. Field Order is determined by a given field's proximity to
primary outlets from in-field irrigation channels and subsequent inter-field irrigation flows. This in turn determines Field
Order in Irrigation Sequence (Field OrderIS). Mean Field Order total soil Cd represents the mean total soil Cd (aqua regia-digested) for a given Field OrderIS. In 2004–2005, Irr-Cad was utilized to evaluate the spatial distribution of total soil Cd in a ‘high-risk’ area of Mae Sot
District. Secondary validation on six randomly selected field groups verified that Irr-Cad predicted mean Field Order total
soil Cd and was significantly (p < 0.001) correlated with the observed mean Field Order total soil Cd with R
2 values ranging from 0.89 to 0.97. The practical applicability of Irr-Cad is in its minimal input requirements, namely the
classification of fields in terms of Field OrderIS, strategic sampling of all primary fields and laboratory based determination of total soil Cd (T-CdP) and the use of a weighed coefficient for Cd (CoeffW). The use of primary fields as the basis for Irr-Cad is also an important practical consideration due to their inherent ease
of identification and vital role in the classification of fields in terms of Field OrderIS. The inclusion of mean field order soil pH (1:5water) to the Irr-Cad model accounted for over 79% of the variation in mean Field Order bio-available (DTPA (diethylenetriaminepentaacetic
acid)-extractable) soil Cd. Rice is the staple food of countries of the Greater Mekong Sub-region (includes Vietnam, Myanmar,
Lao PDR, Thailand and Yunnan Province, China). These countries also have actively and historically mined Zn, Pb, and Cu deposits
where Cd is likely to be a potential hazard if un-controlled discharge/runoff enters areas of rice cultivation. As such, it
is envisaged that the Irr-Cad model could be applied for Cd hazard assessment and effectively form the basis of intervention
options and policy decisions to protect public health, livelihoods, and export security. 相似文献
15.
Carl Van Colen J. Lenoir A. De Backer B. Vanelslander M. Vincx S. Degraer T. Ysebaert 《Marine Biology》2009,156(10):2161-2171
The role of multi-species benthic diatom films (BDF) in the settlement of late pediveliger larvae of the bivalve Macoma balthica was investigated in still-water bioassays and multiple choice flume experiments. Axenic diatom cultures that were isolated
from a tidal mudflat inhabited by M. balthica were selected to develop BDF sediment treatments characterized by a different community structure, biomass, and amount of
extracellular polymeric substances (EPS). Control sediments had no added diatoms. Although all larvae settled and initiated
burrowing within the first minute after their addition in still water, regardless of treatment, only 48–52% had completely
penetrated the high diatom biomass treatments after 5 min, while on average 80 and 69% of the larvae had settled and burrowed
into the control sediments and BDF with a low diatom biomass (<3.5 μg Chl a g−1 dry sediment), respectively. The percentage of larvae settling and burrowing into the sediment was negatively correlated
with the concentration of Chl a and EPS of the BDF. This suggests higher physical resistance to bivalve penetration by the BDF with higher diatom biomass
and more associated sugar and protein compounds. The larval settlement rate in annular flume experiments at flow velocities
of 5 and 15 cm s−1 was distinctly lower compared to the still-water assays. Only 4.6–5.8% of the larvae were recovered from BDF and control
sediments after 3 h. Nonetheless, a clear settlement preference was observed for BDF in the flume experiments; i.e., larvae
settled significantly more in BDF compared to control sediments irrespective of flow speed. Comparison with the settlement
of polystyrene mimics and freeze-killed larvae led to the conclusion that active selection, active secondary dispersal and,
at low flow velocities (5 cm s−1), passive adhesion to the sediment are important mechanisms determining the settlement of M. balthica larvae in estuarine biofilms. 相似文献
16.
Howard W. Mielke Chris R. Gonzales Elise Cahn Jessica Brumfield Eric T. Powell Paul W. MielkeJr 《Environmental geochemistry and health》2010,32(5):431-440
Arsenic (As) ranks first on the 2005 and 2007 hazardous substances priority lists compiled for the Comprehensive Environmental
Response, Compensation, and Liability Act (CERCLA). This study describes two New Orleans soil As surveys: (1) a survey of
composite soil samples from 286 census tracts and (2) a field survey of soil As at 38 play areas associated with the presence
of chromated-copper-arsenate (CCA)-treated wood on residential and public properties. The survey of metropolitan New Orleans
soils revealed a median As content of 1.5 mg/kg (range <0.2–16.4) and no distinctive differences between the soils of the
city core and outlying areas. Play area accessible soils associated with CCA-treated wood (N = 32) had a median As of 57 mg/kg and 78% of the samples were ≥12 mg/kg, the Louisiana soil As standard. The field survey
of play areas for CCA-treated wood (N = 132 samples at 38 sites) was conducted with a portable energy-dispersive X-ray fluorescence (XRF) analyzer. Seventy-five
of 132 wood samples (56.8%) were deemed CCA-treated wood. Of the 38 play areas surveyed, 14 (36.8%) had CCA-treated wood.
A significant association (Fisher’s exact p-value = 0.348 × 10−6) was found between CCA-treated wood and soil As (N = 75). At one elementary school CCA-treated woodchips (As range 813–1,654 mg As/kg) covered the playgrounds. The situation
in New Orleans probably exists in play areas across the nation. These findings support a precautionary program for testing
soils and wood for hazardous substances at all play areas intended for children. 相似文献
17.
Energy dissipation, flow resistance and gas-liquid interfacial area in skimming flows on moderate-slope stepped spillways 总被引:2,自引:2,他引:0
With the re-evaluation and revision of a number of design floods, several embankment overtopping protection systems have been
developed and a common technique is the construction of a stepped spillway on the downstream slope. For such moderate slope
stepped channels, detailed air–water flow measurements were performed in a large facility with a focus on the rate of energy
dissipation, flow resistance, air–water interfacial areas and re-aeration rates. Past and present experimental results showed
a significant aeration of the flow. The median dimensionless residual head was about 3 × dc for the 21.8° sloping chute and smaller than that for flatter slopes (θ = 3.4° and 15.9°). The flow resistance results yielded an equivalent Darcy friction factor of about 0.25 implying a larger
flow resistance for the 21.8° slope angle than for smaller slope angles. The re-aeration rate was deduced from the integration
of the mass transfer equation using measured air–water interfacial areas and air–water flow velocities. The results suggested
an increasing re-aeration rate with increasing rate of energy dissipation. The stepped invert contributed to intense turbulence
production, free-surface aeration and large interfacial areas. The experimental data showed however some distinctive seesaw
pattern in the longitudinal distribution of air–water flow properties with a wave length of about two step cavities. While
these may be caused by the interactions between successive adjacent step cavities and their interference with the free-surface,
the existence of such “instabilities” implies that the traditional concept of normal flow might not exist in skimming flows
above moderate-slope stepped spillways. 相似文献
18.
Quantification and fractionation of mercury in soils from the Chatian mercury mining deposit,southwestern China 总被引:2,自引:0,他引:2
Contents of total Hg and Hg fraction, organic matter, pH, grain size and chemical composition were measured to investigate
the pollution characteristics and binding behavior of Hg in soils collected from the Chatian Hg mining deposit (CMD), southwestern
China. The average concentration of Hg concentration in the CMD soils was 155 and 1,315 times higher than that in control
soils and Chinese soils, respectively, suggesting that the CMD soils were heavily contaminated by the element. The finding
was confirmed by Müller geoaccumulation index assessment with 75% very seriously polluted, 6.25% highly to very highly polluted
and 18.75% moderately to highly polluted. Hg sources in the region were natural and anthropogenic: in addition to the pedogenic
process and original geochemical situation, human mining–refining activities have also seriously impacted the redistribution
of Hg in soils, especially in paddy soils. Based on the BCR protocol, soil Hg was divided into exchangeable (EXC), amorphous
Fe–Mn oxides (AFe–MnOX), organic-crystalline iron oxides (OM-CFe) and residual (RES) fraction. The average percentage of the
four fractions in the CMD followed the trend: RES (85.77%) > OM-CFe (12.44%) > AFe–MnOX (0.93%) ≥ EXC (0.86%), suggesting
that the majority proportion of soil Hg in the study area remained of residual form inside the soil mineral matrix. However,
their concentrations and percentages significantly varied among different locations and land use types. Soil physico-chemical
parameters were key factors affecting the presence of Hg fraction. Generally, Hg fraction concentrations were positively correlated
with the sand contents and soil pH values, which was presumably due to the basic anthropogenic input of Hg-containing materials
and their similarity to sand in physical characteristics. However, organic matter caused adsorption–fixation and reduction–volatilization
to coexist, which had opposite effects on Hg concentrations in soil, consequently exhibiting its dual nature. 相似文献
19.
Evaluation of the QUIC-URB fast response urban wind model for a cubical building array and wide building street canyon 总被引:3,自引:0,他引:3
Balwinder Singh Bradley S. Hansen Michael J. Brown Eric R. Pardyjak 《Environmental Fluid Mechanics》2008,8(4):281-312
This paper describes the QUIC-URB fast response urban wind modeling tool and evaluates it against wind tunnel data for a 7 × 11 cubical building array and wide building street canyon. QUIC-URB is based on the Röckle diagnostic wind modeling strategy that rapidly produces spatially resolved wind fields in urban areas and can be used to drive urban dispersion models. Röckle-type models do not solve transport equations for momentum or energy; rather, they rely heavily on empirical parameterizations and mass conservation. In the model-experiment comparisons, we test two empirical building flow parameterizations within the QUIC-URB model: our implementation of the standard Röckle (SR) algorithms and a set of modified Röckle (MR) algorithms. The MR model attempts to build on the strengths of the SR model and introduces additional physically based, but simple parameterizations that significantly improve the results in most regions of the flow for both test cases. The MR model produces vortices in front of buildings, on rooftops and within street canyons that have velocities that compare much more favorably to the experimental results. We expect that these improvements in the wind field will result in improved dispersion calculations in built environments. 相似文献
20.
Ravi Naidu Euan Smith S. M. Imamul Huq Gary Owens 《Environmental geochemistry and health》2009,31(Z1):61-68
The bioavailability of arsenic (As) in the soil environment is largely governed by its adsorption–desorption reactions with
soil constituents. We have investigated the sorption–desorption behaviour of As in four typical Bangladeshi soils subjected
to irrigation with As-contaminated groundwater. The total As content of soils (160 samples) from the Laksham district ranged
from <0.03 to approximately 43 mg kg−1. Despite the low total soil As content, the concentration of As in the pore water of soils freshly irrigated with As-contaminated
groundwater ranged from 0.01 to 0.1 mg l−1. However, when these soils were allowed to dry, the concentration of As released in the pore water decreased to undetectable
levels. Remoistening of soils to field moisture over a 10-day period resulted in a significant (up to 0.06 mg l−1) release of As in the pore water of soils containing >10 mg As kg−1 soil, indicating the potential availability of As. In soils containing <5 mg As kg−1, As was not detected in the pore water. A comparison of Bangladeshi soils with strongly weathered long-term As-contaminated
soils from Queensland, Australia showed a much greater release of As in water extracts from the Australian soils. However,
this was attributed to the much higher loading of As in these Australian soils. The correlation of pore water As with other
inorganic ions (P, S) showed a strongly significant (P < 0.001) relationship with P, although there was no significant relationship between As and other inorganic cations, such
as Fe and Mn. Batch sorption studies showed an appreciable capacity for both AsV and AsIII sorption, with AsV being retained in much greater concentrations than AsIII. 相似文献