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1.
Batch experiments were performed to investigate cephapirin (a widely used veterinary antibiotic) adsorption on various size
sands of low total organic carbon content (0.08–0.36 wt%). In the aqueous concentration range investigated (11–112 μmol/L
cephapirin), adsorption to nearly pure quartz filter sands (0.50–3.35 mm diameter) is low. Isotherms are S-shaped and most
display a region of minimum adsorption, where decreased adsorption occurs with increasing solution concentration, followed
by increased adsorption at higher concentrations. Cephapirin adsorption to quartz-rich, feldspar-bearing dune sands (0.06–0.35 mm
diameter), and the smallest quartz filter sand investigated (0.43–0.50 mm), can be described by linear sorption isotherms
over the range of concentrations investigated. Distribution coefficients (K
d) range from 0.94 to 3.45 L/kg. No systematic relationship exists between grain size and amount of adsorption for any of the
sands investigated. Cephapirin adsorption is positively correlated to the feldspar ratio (K-feldspar/(albite + Ca-plagioclase).
Feldspar-ratio normalization of distribution coefficients was more effective than organic carbon normalization at reducing
variability of K
d values in the dune sands investigated. 相似文献
2.
Wind tunnel experiments were carried out with respect to the vertical distributions of wind-blown sand flux and the processes
of aeolian erosion and deposition under different wind velocities and sand supplies above beds with different gravel coverage.
Preliminary results revealed that the vertical distribution of wind-blown sand flux was a way to determine whether the gobi
sand stream was the saturated one or not. It had different significances to indicate characteristics of transport and deposition
above gobi beds. Whether bed processes are of aeolian erosion or deposition was determined by the sand stream near the surface,
especially within 0–6 cm height, while the sand transport was mainly influenced by the sand stream in the saltating layer
above the height of 6 cm. The degree of the abundance of sand supply was one of the important factors to determine the saturation
level of sand stream, which influenced the characteristic of aeolian erosion and deposition on gravel beds. Given the similar
wind condition, the sand transport rates controlled by the saturated flow were between 2 and 8 times of the unsaturated one.
Those bed processes controlled by the saturated flow were mainly of deposition, and the amount of sand accumulation increased
largely as the wind speed increased. In contrast, the bed processes controlled by the unsaturated flow were mainly of aeolian
erosion. Meanwhile, there was an obvious blocking sand ability within the height of 0–2 cm, and the maximal value of sand
transport occurred within the surface of 2–5 cm height. 相似文献
3.
Soil hydraulic properties such as soil infiltration rate and hydraulic conductivity are closely linked to runoff generation
and infiltration processes but little is known about them on karst hillslopes. The objectives of this paper were to investigate
the change in soil stable infiltration rate (q
s) and near-saturated hydraulic conductivity (K
ns) in different slope positions and to understand their relationship with rock fragment content and soil texture within the
topsoil in subtropical karst regions of southwest China. Tension infiltrometers (20 cm in diameter) were used to measure q
s and K
ns at pressure head of −20 mm on hillslopes 1 (a disintegrated landslide failure) and 2 (an avalanche slope). The change of
q
s and K
ns was great and they mostly had a moderate variability with coefficient of variations (CV) between 0.1 and 1.0 in the different
slope positions. On average, q
s ranged from 0.43 to 4.25 mm/min and K
ns varied from 0.75 to 11.00 mm/min. These rates exceed those of most natural rainfall events, confirming that overland flow
is rare on karst hillslopes. From bottom to top, q
s and K
ns had a decrease–increase–decrease trend due to the presence of large rock outcrops (>2 m in height) on hillslope 1 but had
an increasing trend on hillslope 2 with less complex landform. They tended to increase with increase in total rock fragment
content (5–250 mm) within the topsoil as well as slope gradient on both hillslopes. Pearson correlation analysis suggested
that higher coarse pebble (20–75 mm), cobble (75–250 mm), and sand (2–0.05 mm) contents as well as total rock fragment content
could significantly facilitate water infiltration into soils, but higher clay (<0.002 mm) content could restrict water movement.
This result indicated that rock fragment, sand, and clay contents may remarkably affect water flow in the topsoil layers,
and should be considered in hydrological modeling on karst hillslopes in subtropical regions. 相似文献
4.
Mark P. S. Krekeler Erin P. Argyilan Jill Lepp Lance E. Kearns 《Environmental Earth Sciences》2009,59(2):411-420
Constructed wetlands can be a low-cost, ecologically based technology to locally treat domestic wastewater prior to discharge.
Wetland systems implemented in the resort village of Akumal in the state of Quintana Roo, in the Yucatan Peninsula of Mexico
have been considered moderately successful over approximately 10 years of operation. Yet the wide-scale implementation of
constructed wetlands has not occurred in the region nor throughout Mexico due largely to the cost of the crushed aggregate
used in these systems. Variation in the geotechnical and mineralogical properties of 29 samples of local calcareous beach
sands collected from the tourist areas of Akumal and Tulum in the Yucatan, Mexico were analyzed and compared to those of crushed
aggregate currently used in constructed wetland systems in Akumal. Powder X-ray diffraction on beach sand samples from Akumal
and Tulum indicates that the proportion of aragonite varies from 24 to 84%, calcite varies from 7 to 38% and Mg-calcite varied
from 8 to 57% compared to crushed aggregate which consists of 0–25% aragonite and 75–100% calcite. Compared to crushed aggregate
beach sands are unimodal and have better uniformity coefficients, making them a better geotechnical choice than crushed sands
with respect to these properties. Grain-size of the beach sands is much smaller compared to that of the crushed aggregate
currently used in the constructed wetland systems in Akumal which should enhance the efficiency of the filtration of organic
matter and bacteria. The average hydraulic conductivity measurements of 0.010 and 0.016 cm/s for beach sands from Akumal and
Tulum, respectively are comparable or less than the average of 0.016 cm/s for crushed aggregate currently used in engineered
wetland systems. Yet a combination of high bulk porosity, intragranular pores, and the presence of Mg-calcite observed in
beach sands may likely result in higher dissolution rates versus the crushed aggregate. Preliminary assessment suggests that
the use of local sand may be a technical, economic, and perceptual enhancement to the systems. Still a careful and thorough
analysis of the potential environmental and aesthetic impacts of mining beach sands is necessary. 相似文献
5.
In this paper, an experimental investigation of cement treated sand is performed under triaxial tests in order to quantify
the effects of cementation on the stress–strain behavior, stiffness and shear strength. Samples were cured up to 180 days.
The results show that the stress–strain behavior of cemented sands is nonlinear with contractive–dilative stages. The stress–strain
response is strongly influenced by effective confining pressure and cement content. Stiffness and strength are greatly improved
by an increase in binder content. An increase of the angle of shearing resistance and cohesion intercept with increasing cement
content is observed consistently. Brittle behavior is observed at low confining pressure and high cement content. After yielding,
the increase in the dilatancy accelerates. Two competing related processes determine the peak strength: Bond breakages cause
a strength reduction but the associated dilatancy leads to a strength increase. This finding and the experimental observation
that the dilatancy at the peak state increases with increasing cement content explain why the measured peak-state strength
parameters, c′ and φp′, are relevant to the binder content. 相似文献
6.
A worldwide dataset of organic material from 553 samples belonging to coal and carbonaceous materials was used to analyze
the evolution of hydrogen index (HI) and bitumen index (BI) with increasing thermal maturity. Basic statistical analyses were
applied to detect the boundary lines of HImax and BImax in delineating the upper and lower limits of the HI and BI bands for the majority of samples. In addition, cross-plots of
HI or BI versus maturity (Ro% and T
max) also provide criteria for defining the HImax and BImax boundary lines. The constructed HI and BI bands are broad at low maturities and become narrower with increasing thermal maturities.
The petroleum generation potential is completely exhausted at the vitrinite reflectance of 2.0–2.2% or T
max of 510–520°C. An increase in HI implies extra petroleum generation which was related to changes in structure of organic materials.
A declining BI means that the oil expulsion window starts to occur at the vitrinite reflectance range of 0.75–1.05%. The petroleum
potential can be divided into four different areas based on the cross-plot of HI versus Ro%. The highest petroleum potential
area is located in section II with Ro = 0.6–1.0% and HI > 100. The oil generation potential is rapidly exhausted at section
III with Ro > 1.0%. This result is also in accordance with the result of curve regression of HI versus Ro% based on 80 samples
with Ro = 1.02–3.43% (R
2 = 0.72). Overall, the total oil window can be extended up to Ro = ~1.25–1.95%. Finally, in the cross-plots of S1 versus S2,
shale or C-shale exhibits a higher and slowly decreased slope, compared with a lower and then sharply increased slope of coal
samples, which is attributable to their compositional difference in organic material. 相似文献
7.
Mobility and ecological risk assessment of heavy metals in surface sediments of Xiamen Bay and its adjacent areas,China 总被引:4,自引:1,他引:3
Xiamen Bay (XMB) has received substantial loadings of pollutants from industrial and municipal wastewater discharged since
the 1980s. To assess ecological risks and the current spatial changes of metal contaminants in bottom surface sediments, 12
samples were collected. Samples were subjected to a total digestion technique and analyzed by ICP–OES for Cu, Pb, Zn, Cr,
and Cd, and by AFS for Hg and As. Among these metals, Zn had the highest values (68–268 mg kg−1), followed by Pb (27–71 mg kg−1), and lower concentrations were found for Cd (42–1,913 μg kg−1) and Hg (0–442 μg kg−1). In comparison with the average crustal abundance values, the results indicated that nearly half of the sediment samples
of XMB and its adjacent areas were contaminated by Cd, Pb, Zn, and As. Furthermore, based on the modified BCR sequential extraction
procedure, the chemical speciation of heavy metals (Cd, Cr, Cu, Pb, Zn, Hg, and As) in selected sediment samples were evaluated
in this study. Data from BCR sequential extractions indicated that Cd posed a medium ecological risk, whereas, Cr posed low
risk since its exchangeable and carbonate fractions were below 4%, and the mobility of heavy metals in XMB decreased in the
order Cd > Pb > Cu > Zn > Hg > As > Cr. By applying mean effects range median quotients (mERMQ), the results showed that Yuandang
Lagoon with mERMQ value >0.5 would be expected to have the greatest potential toxic risk in amphipod within XMB and its adjacent
areas. 相似文献
8.
Asmae Mhamdi Alaoui Mohamed Choura Mohamed Maanan Bendahhou Zourarah Marc Robin Maria Freitas Conceição César Andrade Mehdi Khalid Christian Carruesco 《Environmental Earth Sciences》2010,61(2):275-286
The metal content in surface sediments (0–2 cm, 26 samples), in a sediment core (120, 1 cm slices), taken from Moulay Bousselham
(Morocco) was investigated. Concentrations of Al, Fe, Mn, Pb, Zn, Cu, Ni, Cr, Cd, As, and Hg were evaluated in surface and
cored sediments of Moulay Bousselham lagoon. Significantly high concentrations in μg g−1 dw of Pb (31.7–6.2), Zn (758.9–167), Cu (310.7–22), Ni (96–10.5), Cr (113–18.9), Cd (0.84–0.02), As (1–0.1), and Hg (0.61–0.02)
were found in sediment samples from Moulay Bousselham lagoon. Calculated enrichment factors [EFMe = (Me/Al)sample/(Me/Al)background], using Al as a normalizer, and correlation matrices showed that metal pollution in Merja Zerga of Moulay Bousselham lagoon
was the product of anthropogenic sources, while the metal content in Merja Kehla was of natural origins. The results suggest
that a major change in the sedimentary regime of the lagoon, associated with internal trapping and re-distribution of heavy
metal, has been occurring in the past few decades. The cause would appear to be the construction of a Nador Canal at the lagoon.
Probable effects concentrations (PEC) were often exceeded for heavy metals in the lagoon sediments, especially for Zn, Cu,
Ni, and Cr, and four stations, stations MZ-11, MZ-12, MZ-13, MZ-14, MZ-16, and MZ-17, had multiple metals at presumptively
toxic levels. These comparisons suggest that sediment metal levels in the river are clearly high and probably pose an environmental
risk at some stations. The levels of most of the metals were not greatly enriched, a consideration that is of the utmost importance
when contamination issues are at stake. Metal concentrations found in Moulay Bousselham lagoon were comparable to aquatic
systems classified as contaminated from other regions of the world. 相似文献
9.
Geochemistry of Cu, Co, Ni, Zn, Cd and Cr in the surficial sediments of a tropical estuary, southwest coast of India: a granulometric approach 总被引:3,自引:0,他引:3
Geochemical characteristics of six trace metals – Cu, Co, Ni, Zn, Cd and Cr – in the bulk sediment and sand, silt and clay
fractions of a tropical estuary on the southwest coast of India have been studied and discussed. In bulk sediment, the trace
metal concentration is controlled mainly by the textural composition of the sample. Mud, sandy mud and sandy silt register
higher concentrations of trace metals than that in sand-dominant sediments. The granulometric partitioning studies also re-affirmed
the role of particle size in enriching the trace metals. The silt and clay fractions exhibit 7–8 times the enrichment of Cu
and Cd compared to that in sand. The enrichment factors of Zn, Cr, Ni and Co in the silt and clay fractions, compared to that
in sand, are 5–6, 4–5, 2–5 and 2–3 times, respectively. The trace metals in the sand fraction, particularly Ni and Cr, exhibit
strong positive correlation with the heavy mineral content of the samples. It clearly indicates a heavy mineral pathway to
the trace metals in the sand fraction. Cu and Co in silt and clay fractions exhibit a marked decrease towards the high saline
zones of the estuary. This is attributed to the desorption of Cu and Co from particulate phases during estuarine mixing. Contrary
to Cu and Co, the content of Zn in the clay fraction shows a marginal increase towards the estuarine mouth. This could be
explained by the influx of Zn-rich contaminant discharges from Zn-smelting industries located slightly north of the estuarine
mouth. The released Zn will effectively be held in the lattices of the clay mineral montmorillonite, which also exhibits a
marked increase towards the estuarine mouth. The anomalously high values of Cd in some places of the Central Vembanad estuary
is attributed to the local pollution.
Received: 10 July 1995 · Accepted: 3 June 1996 相似文献
10.
Distribution and enrichment of trace metals in marine sediments of Bay of Bengal,off Ennore,south-east coast of India 总被引:1,自引:0,他引:1
In order to avoid the pollution of trace metals in marine environment, it is necessary to establish the data and understand
the mechanisms influencing the distribution of trace metals in marine environment. The concentration of heavy metals (Fe,
Mn, Cr, Cu, Ni, Pb, Zn, Co and Cd) were studied in sediments of Ennore shelf, to understand the metal contamination due to
heavily industrialized area of Ennore, south-east coast of India. Concentration of metals shows significant variability and
range from 1.7 to 3.7% for Fe, 284–460 μg g−1 for Mn, 148.6–243.2 μg g−1 for Cr, 385–657 μg g−1 for Cu, 19.8–53.4 μg g−1 for Ni, 5.8–11.8 μg g−1 for Co, 24.9–40 μg g−1 for Pb, 71.3–201 μg g−1 for Zn and 4.6–7.5 μg g−1 for Cd. For various metals the contamination factor (CF) and geoaccumulation index (I
geo) has been calculated to assess the degree of pollution in sediments. The geoaccumulation index shows that Cd, Cr and Cu moderately
to extremely pollute the sediments. This study shows that the major sources of metal contamination in the Ennore shelf are
land-based anthropogenic ones, such as discharge of industrial wastewater, municipal sewage and run-off through the Ennore
estuary. The intermetallic relationship revealed the identical behavior of metals during its transport in the marine environment. 相似文献
11.
Effects of rock fragments on infiltration and evaporation in hilly purple soils of Sichuan Basin,China 总被引:5,自引:0,他引:5
Weihua Zhang Chaofu Wei Yan Li Gaigai Wang Deti Xie 《Environmental Earth Sciences》2011,62(8):1655-1665
This paper presents the results of laboratory experiments showing the effects of rock fragments contained in three different
purple soils of the Sichuan basin of southwest China. The experiments investigated how these rock fragments alter the soil’s
physical, chemical, and agronomical characteristics such as infiltration and evaporation. We found that the infiltration rate,
whether horizontal or vertical, in the three soils has the following order: gray brown purple soil < reddish brown purple
soil < brown purple soil. With increasing rock fragment contents the accumulated infiltration decreases, while the total time
decreases first and then increases. The minimum occurs at approximately 10–20% of fragment content by weight. The infiltration
rate also changes with the distance. In the 0–5 cm range, the initial infiltration rate increases with increasing rock fragment
contents, while in the 5–10 cm range, the slope of infiltration curve increases with increasing rock fragment contents. With
increasing distance, the slope gradually decreases and finally reaches a stable value. The presence of rock fragments reduces
soil water content, the minimal value appearing when the rock fragments were on top of the soil column (soil + rock sample),
decreasing with increasing rock fragments for other samples mixed with fragments. Under the constant 40°C temperature, the
accumulated evaporation and evaporation rate are minimal for soils covered by rock fragments, and the accumulated evaporation
decreases with increasing rock fragment for other soil samples. However, the evaporation rate increases with increasing rock
fragments in the first 4 days and decreases thereafter. 相似文献
12.
This paper presents results of analysis of full-scale pile load test data of 14 piles embedded in either loose or medium dense
sands. The analysis was performed using two methods, p–y curve approach and a more recently developed khmax approach. Comparison of the results obtained using both the methods is also presented. A step-by-step analysis procedure
is presented for predicting lateral load deflection response of single piles in sand using the khmax approach. The results presented show that the khmax approach has promise over the p–y curve approach because of its simplicity and the fact that it provides upper- and lower-bound curves, which are valuable
guides to making engineering decisions. For loose sands, a new range of khmax values is recommended to better predict the lateral load–deflection response of single piles. 相似文献
13.
Calculated phase equilibria involving minerals and H2O–CO2–NaCl fluid lead to predictions of how infiltration of rock by H2O–NaCl fluids with X
NaCl in the range 0–0.3 (0–58 wt% NaCl) drives the reactions calcite + quartz = wollastonite + CO2 and dolomite = periclase + calcite + CO2. Calculations focus on metamorphism in four aureoles that together are representative of the normal P–T conditions and processes of infiltration-driven contact metamorphic reactions. The effect of salinity on the spatial extent
of oxygen isotope alteration was also computed. The time-integrated input fluid flux (q°) that displaces the mineral reaction front an increment of distance along the flow path always increases with increasing
X
NaCl. For input fluids with salinity up to approximately five times that of seawater (X
NaCl ≤ 0.05), values of q° required to explain the spatial extent of decarbonation reaction are no more than 1.1–1.5 times that computed assuming the
input fluid was pure H2O. For more saline fluids, values of q° may be up to 1.4–7.9 times that for pure H2O. Except for reaction in the presence of halite and vapor (V), infiltration of H2O–NaCl fluids expands the region of oxygen isotope alteration relative to the size of the region of mineral reaction. The
expansion is significant only for saline fluids with X
NaCl ≥ ~0.1. Immiscible fluid phase separation and differential loss of the liquid (L) or V phase from the mineral reaction site increases the amount of reactive fluid required to advance the mineral reaction front
compared to conditions under which equilibration of minerals and fluid is attained with no loss of L or V. Decarbonation reactions driven by infiltration of fluids with even modest seawater-like salinity can explain the occurrence
of salt-saturated fluid and solid halide inclusions in contact metamorphosed carbonate rocks. 相似文献
14.
N. Stark R. Wilkens V. B. Ernstsen M. Lambers-Huesmann S. Stegmann A. Kopf 《Geotechnical and Geological Engineering》2012,30(1):1-14
The societal usage of coastal zones (including offshore wind energy plants, waterway deepening, beach conservation and restoration)
is of emerging importance. Sediment dynamics in these areas result in sandy deposits due to strong tidal and wave action,
which is difficult to simulate in laboratory geotechnical tests. Here, we present data from in situ penetrometer tests using
the lightweight, free-fall Nimrod penetrometer and complementary laboratory experiments to characterize the key physical properties of sandy seafloors in areas
dominated by quartzose (North Sea, Germany) and calcareous (Hawaii, USA) mineralogy. The carbonate sands have higher friction
angles (carbonate: 31–37°; quartz: 31–32°) and higher void ratios (carbonate: 1.10–1.40; quartz: 0.81–0.93) than their siliceous
counterparts, which have partly been attributed to the higher angularity of the coral-derived particles. During the in situ
tests, we consistently found higher sediment strength (expressed in deceleration as well as in estimated quasi-static bearing
capacity) in the carbonate sand (carbonate: 68–210 g; quartz: 25–85 g), which also showed a greater compressibility. Values
were additionally affected by seafloor inclination (e.g., along a sub-aqueous dune or a channel), or layering in areas of
sediment mobilization (by tides, shorebreak or currents). The study shows that the differences in in situ measured penetration
profiles between carbonate sands and quartz sands are supported by the laboratory results and provide crucial information
on mobile layers overlying sands of various physical properties. 相似文献
15.
Evaluation of hydrogeochemical processes in arsenic-contaminated alluvial aquifers in parts of Mid-Ganga Basin,Bihar, Eastern India 总被引:1,自引:1,他引:0
Dipankar Saha Sreehari S. Sarangam Shailendra N. Dwivedi Kuldeep G. Bhartariya 《Environmental Earth Sciences》2010,61(4):799-811
The study region covers 1,650 km2 of the Mid-Ganga Basin in Bihar, experiencing intensive groundwater draft. The area forms a part of the Gangetic alluvial
plain where high incidence of arsenic groundwater contamination (>50 μg/l) has recently been detected. Seventy-seven groundwater
samples have been collected and analysed for major ions, iron and arsenic. Arsenic contamination (max 620 μg/l) is confined
in hand pump zones (15–35 m) within the newer alluvium deposited during Middle Holocene to Recent age. The older alluvial
aquifers are arsenic-safe and recorded maximum concentration as 9 μg/l. Out of 12 hydrochemical facies identified, four have
been found arsenic-affected: Ca–HCO3, Mg–HCO3, Ca–Mg–HCO3 and Mg–Ca–HCO3. The geochemical evolution of groundwater, as investigated by graphical interpretation and statistical techniques (correlation,
principal component analysis) revealed that dissolution of detrital calcite, dolomite and infiltration of rainwater are the
major processes shaping the groundwater chemistry in the newer alluvium. Arsenic and iron showed strong positive correlation.
Rainfall infiltration, carrying organic matter from recently accumulated biomass from this flood-prone belt, plays a critical
role in releasing arsenic and iron present in the sediments. Geochemical evolution of groundwater in older alluvium follows
a different path, where cation-exchange has been identified as a significant process. 相似文献
16.
Studies on the variations of heavy metals in the marine sediments off Kalpakkam,East Coast of India 总被引:1,自引:1,他引:0
K. K. Satpathy A. K. Mohanty M. V. R. Prasad Usha Natesan S. K. Sarkar 《Environmental Earth Sciences》2012,65(1):89-101
During the last two decades, the coastal environment of southeast India has experienced intense developments in industry,
urbanization and aquaculture. Moreover, the 2004 mega tsunami has devastated this coast, thus affecting the coastal sediment
characteristics. These two phenomena prompted a study to characterize the sediment, to understand the mechanisms influencing
the distribution of heavy metals and to create baseline data for future impact assessment. Results showed that the coastal
sediment was carpeted with a mosaic of sand and silty sand with a minor amount of clay. Heavy metal values showed maximum
variation for Fe and minimum for Cd. Their average values showed the following decreasing trend: Fe > Cu > Zn > Pb > Cr > Ni > Cd.
This study shows that the major source of metals at Kalpakkam coast are land-based anthropogenic ones, such as, discharge
from industrial waste, agricultural waste, urban, municipal and slum sewage into the Buckingham canal, which in turn discharges
into the sea through backwaters, particularly during northeast monsoon period. A clear signature of the role of backwater
discharge increasing the concentration of a few metals in the coastal sediments during monsoon period was observed. Assessments
of the degree of pollution, concentration factor (CF), geoaccumulation index (I
geo) and pollution load index (PLI) have been calculated. CF values and I
geo indicated that the coastal sediment is moderately polluted by Cu and Cd. Increase in Cu, Pb and Zn concentration during the
monsoon period (October–January) compared to the rest of the year was noticed. Factor analysis and correlation among the heavy
metals concluded that Cr, Ni, Cd and Fe are of crustal origin, whereas, Cu, Pb and Zn are from anthropogenic sources. Organic
carbon content in the sediment increased during monsoon period, pointing to the role of land runoff and backwater discharge
in enhancing its content. The study also elucidates the impact of the recent tsunami in depleting metal content in the coastal
sediment as compared to the pre-tsunami period. 相似文献
17.
Contamination and potential mobility assessment of heavy metals in urban soils of Hangzhou,China: relationship with different land uses 总被引:1,自引:0,他引:1
Concentration and distribution of heavy metals (Cd, Cu, Pb and Zn) in urban soils of Hangzhou, China, were measured based
on different land uses. The contamination degree of heavy metals was assessed on the basis of pollution index (PI), integrated
pollution index (IPI) and geoaccumulation index (I
geo). The 0.1 mol l−1 HCl extraction procedure and gastric juice simulation test (GJST) were used to evaluate the potential mobility and environmental
risk of heavy metals in urban soils. The average concentration of Cd, Cu, Pb and Zn in urban soils was measured at 1.2 (with
a range of 0.7–4.6), 52.0 (7.4–177.3), 88.2 (15.0–492.1) and 206.9 (19.3–1,249.2) mg kg−1, respectively. The degree of contamination increased in the order of industrial area (IA) > roadside (RS) > residential and
commercial areas (RC) > public park and green areas (PG). The PIs for heavy metals indicated that there is a considerable
Cd, Cu, Pb and Zn pollution, which originate from traffic and industrial activities. The IPI of these four metals ranged from
1.6 to 11.8 with a mean of 3.5, with the highest IPI in the industrial area. The assessment results of I
geo also supported that urban soil were moderately contaminated with Cd and to a lesser extent also with Cu, Pb and Zn. The IP
and I
geo values reveal the pollution degree of heavy metal was the order of Cd > Pb > Zn ≈ Cu. It was shown that mobility and bioavailability
of the heavy metals in urban soils increased in the order of Cd > Cu > Zn ≈ Pb. Owing to high mobility of Cd and Cu in the
urban soils, further investigations are needed to understand their effect on the urban environment and human health. It is
concluded that industrial activities and emissions from vehicles may be the major source of heavy metals in urban contamination.
Results of this study present a rough guide about the distribution and potential environmental and health risk of heavy metals
in the urban soils. 相似文献
18.
Geochemistry of fluoride rich groundwater in Kolar and Tumkur Districts of Karnataka 总被引:2,自引:2,他引:0
Groundwater is a significant water resource in India for domestic, irrigation, and industrial needs. By far the most serious
natural groundwater-quality problem in India, in terms of public health, derives from high fluoride, arsenic, and iron concentrations.
Hydrogeochemical investigation of fluoride contaminated groundwater samples from Kolar and Tumkur Districts in Karnataka are
undertaken to understand the quality and potability of groundwater from the study area, the level of fluoride contamination,
the origin and geochemical mechanisms driving the fluoride enrichment. Majority of the groundwater samples did not meet the
potable water criteria as they contained excess (>1.5 mg/L) fluoride, dissolved salts (>500 mg/L) and total hardness (75–924 mg/L).
Hydrogeochemical facies of the groundwater samples suggest that rock weathering and evaporation–crystallization control the
groundwater composition in the study area with 50–67% of samples belonging to the Ca–HCO3 type and the remaining falling into the mixed Ca–Na–HCO3 or Ca–Mg–Cl type. The saturation index values indicated that the groundwater in the study area is oversaturated with respect
to calcite and under-saturated with respect to fluorite. The deficiency of calcium ion concentration in the groundwater from
calcite precipitation favors fluorite dissolution leading to excess fluoride concentration. 相似文献
19.
There is a pressing need of finding innovative and beneficial ways of using scrap tires in the construction of various geotechnical
structures because a large number of waste tires are generated and discarded every year throughout the world. One example
of such geotechnical application is the use of tire shreds mixed with soil as a backfill material for mechanically stabilized
earth (MSE) walls. In this paper, we report the results of laboratory pullout tests performed to study the interaction between
ribbed-metal-strip reinforcement and tire shred–sand mixtures prepared with various tire shred sizes (9.5 mm in nominal size,
50–100 mm in length, and 100–200 mm in length) and tire shred-to-sand mixing ratios (tire shred contents of 0, 12, 25, 100%
by weight). The pullout capacities of ribbed metal strips embedded in tire shred–sand mixtures were obtained for three confining
pressures (40, 65, and 90 kPa). The test results showed that the pullout capacity of ribbed metal strips embedded in tire
shred–sand mixtures is much higher than that of ribbed metal strips embedded in samples prepared with only tire shreds. Based
on the laboratory pullout test results, an equation was developed that can be used to estimate the pullout capacity of ribbed
metal strips embedded in tire shred–sand mixtures if the tire shred size, compacted unit weight of the mixture, mean particle
size of sand, and vertical effective stress acting at the interface are known. 相似文献
20.
Behavior of heavy metals in sulfide mine tailings and bottom sediment (Salair,Kemerovo region,Russia) 总被引:2,自引:1,他引:1
The given work focused on solving the problem of environmental geochemistry related to investigation of element speciation,
their mobility, and migration in polluted areas. The purpose was to describe quantitatively migration, distribution, and redistribution
of heavy metals by the example of the old tailings (Talmovaya sands) of the Lead Zinc Concentration Plant (Salair, Kemerovo
region, Russia) and technogenic bottom sediments of the Malaya Talmovaya river. Contents of elements in the sulfide tailings
range in the following limits: Zn: 1,100–27,000 ppm, Cd: 1.3–240 ppm, Pb: 0.01–0.81 ppm, Cu: 220–960 ppm, As: 15–970 ppm,
Fe: 19,000–76,000 ppm, and Ba: 80,000–1,00,000 ppm. Element concentrations in the river sediment are proportional to the element
contents in the sulfide tailings. Element speciations in the sulfide tailings and technogenic bottom sediments were investigated
by the modified sequential extraction procedure. Chemical forms of heavy metals in pore water and surface water were calculated
by WATEQ4F software. Principles of heavy metal migration in the sulfide tailings and technogenic bottom deposits were established.
The obtained results about element species in the sulfide tailings and sediment explain the main principles of element migration
and redeposition. In the mine waste and technogenic bottom deposits, there is vertical substance transformation with formation
of geochemical barriers. 相似文献