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1.
Chunfa Wu Yongming Luo Biao Huang Haibo Zhang Huoyan Wang 《Environmental Earth Sciences》2010,61(6):1239-1247
A total of 782 topsoil samples (0–20 cm) and 371 subsoil samples (20–40 cm) were collected from agricultural land in two rapidly
industrialized areas with a large number of small rural industries in southeast China, Zhangjiagang City (ZJG) and Changshu
City (CS), to measure soil chromium (Cr) concentrations. Kriging and cokriging were used to predict the spatial distribution
of Cr in the topsoils and subsoils. Paired-samples t test and spatial distribution maps were used to compare the Cr concentrations in topsoils and subsoils. The mean Cr concentration
in ZJG topsoils was significantly higher than that in ZJG subsoils and the mean Cr concentration in CS topsoils showed no
significant difference from that in CS subsoils. The Cr concentrations in topsoils were higher than those in subsoils over
most of the area of ZJG and part of CS, suggesting that Cr accumulation had occurred in these areas and extrinsic factors
have an important role controlling the distribution of Cr in topsoils. Semivariogram/cross-semivariogram was used to evaluate
soil Cr spatial variability. The Cr in ZJG topsoils, ZJG subsoils, and CS topsoils had moderate spatial dependence and the
Cr in CS subsoils had strong spatial dependence. Cr in ZJG subsoils had longer effective range than Cr in ZJG topsoils, suggesting
that the anthropogenic factors affecting Cr distribution in ZJG topsoils; and Cr in CS topsoils had longer effective range
than Cr in CS subsoils, indicating that soil formation may be the major explanation for the decrease in the variation of Cr
in topsoils. A significant correlation was found between the Cr in topsoils and Cr in subsoils, indicating that natural factors
also play an important role as extrinsic factors that control the distribution of Cr in topsoils. 相似文献
2.
The 137Cs tracer technique was used to study soil erosion of alpine meadow grassland in two small river basins in the headwater region
of the Yellow River. The results show that the levels of 137Cs in soil samples from this alpine meadow vegetation zone exhibit an exponential distribution, generally within a depth of
approximately 20 cm. Due to strong winds, freeze-thaw cycles and water, soil erosion was found to be stronger on the upper
slope than on the lower slope, and except for the slope crest, the intensity of soil erosion at other sites was as follows:
upslope < midslope < downslope. There was a significant negative correlation between the intensity of soil erosion and the
extent of alpine meadow vegetation cover (P < 0.01). The mean soil erosion modulus exhibited a linear reduction trend with an increase in vegetation cover, and the correlation
coefficient R
2 was ≥ 0.997. The higher the degradation degree of the alpine meadow grassland, the greater is the soil erosion. The mean
erosion modulus in the severely degraded meadow zone was 2.23 times greater than the one in the slightly degraded zone, and
the maximum erosion modulus reached 2.96 × 106 kg/km2/a. 相似文献
3.
Biogeochemical investigation in south eastern Andhra Pradesh: the distribution of rare earths, thorium and uranium in plants and soils 总被引:4,自引:0,他引:4
The concentration of rare earth elements (REE), thorium and uranium were determined by inductively coupled plasma mass spectrometry
(ICP−MS) in the plant species, Pterocarpus santalinus, P. marsupium and P. dalbergioides, and the soils on which they were growing. Higher concentrations of lanthanum (La), cerium (Ce) were observed in both plants
and soils. Large amounts of thorium and uranium were found in the soil. In all tree species, the concentration of REEs were
higher in the heartwood than the leaves. The heartwood of P. santalinus accumulated larger quantities of uranium (average concentration of 1.22 ppm) and thorium (mean value of 2.57 ppm) than the
other two species.
Received: 8 September 1999 · Accepted: 15 December 1999 相似文献
4.
宁夏固原市原州区高氟地区氟对人体健康的影响 总被引:1,自引:0,他引:1
近年来随着人们生活质量的提升,对健康的关注度也不断提高,氟中毒性地方病越来越受到人们的重视。在关注氟污染源分析及暴露途径研究的同时,开展氟暴露途径评价健康风险研究也十分必要。据调查,固原市原州区彭堡镇地区表层土壤氟含量高于当地区域背景值,本文针对当地存在氟超标导致地方病的实际情况,重点采集了固原市原州区彭堡镇地区表层土壤、地层岩石、农作物、地下水等样品,主要采用电感耦合等离子体发射光谱法(ICP-OES)、原子荧光光谱法(AFS)等分析方法对相关元素进行分析测试,研究固原市原州区彭堡镇高氟区氟超标对人体健康的影响,并运用健康风险评价模型对人体健康风险进行评价。评价结果表明:谷物和蔬菜氟暴露途径健康风险指数HQ<1,没有非致癌风险。当地人体氟暴露风险主要途径为饮用地下水摄入,相关的健康风险指数HQ>1,这表明通过饮用氟超标的地下水,可能具有潜在的非致癌风险。年度总健康风险为1.69×10-8,低于国际辐射防护委员会(ICRP)建议的最大可接受年健康风险水平5.0×10-5,属于人类可接受的风险水平。根据氟健康风险评价结果,本文提出该地区饮用水安全性方面还需多给予关注。 相似文献
5.
In order to investigate the distribution characteristics of stable carbon isotope ratios (δ
13C) in the desert plant Reaumuria soongorica, the δ
13C values of leaves were measured in 407 individuals of 21 populations. Soil physicochemical properties including soil water
content, soil total dissolved solids, soil total nitrogen, soil total phosphorus and soil organic content were also analyzed
in order to survey the major factors influencing δ
13C values on spatial variation. Leaves and soil samples were simultaneously collected from the ten major distribution areas
in Northwest China at altitudes from 394 m to 1 987 m above sea level, at latitudes from 36°10′N to 44°33′N, and at longitudes
from 81°43′E to 106°37′E. These ten areas include Shihezi, Baicheng, Yiwu areas in Xinjiang Uygur Autonomous Region; Anxi,
Zhangye, Baiyin, Lanzhou areas in Gansu Province; Shapotou, Yinchuan areas in Ningxia Hui Autonomous Region; and Alashan County
in Inner Mongolia Autonomous Region. The results show that the δ
13C value of R. soongorica ranges from −22.77‰ to −29.85‰ with an average of −26.52‰. Foliar d13C values in R. soongorica are not significantly correlated with altitude, latitude or longitude, and a spatial distribution trend of d13C values of
R. soongorica is not obvious on a large scale. However, when d13C values of two R. soongorica populations under the same climate conditions are compared, δ
13C values increase obviously from east to west and from north to south. As none of the soil total dissolved solids, soil total
nitrogen, soil total phosphorus, and soil organic content shows a uniform trend from east to west and from north to south,
we suppose that the small-scaled spatial distribution pattern of δ
13C values of R. soongorica is mainly controlled by the soil water content.
Translated from Quaternary Sciences, 2006, 26(6): 947–954 [译自: 第四纪研究] 相似文献
6.
Arsenic derived from mining activity may contaminate water, soil and plant ecosystems resulting in human health and ecotoxicological risks. In this study, exposure assessment of arsenic (As) in soil, spoil, pondwater and plants collected from the areas contaminated by mine tailings and spoils in and around the La Parrilla mine, Caceres province, Spain, was carried out using AAS method. Water solubility, bioavailability and soil–plant transfer coefficients of As and phytoremediation potential of plants were determined. Arsenic concentrations varied from 148 to 2,540 mg/kg in soils of site 1 and from 610 to 1,285 mg/kg in site 2 exceeding the guideline limit for agricultural soil (50 mg/kg). Arsenic concentrations in pond waters varied from 8.8 to 101.4 μg/l. High concentrations of water-soluble As in the soils that ranged from 0.10 to 4.71 mg/kg in site 1 and from 0.46 to 4.75 mg/kg in site 2 exceeded the maximum permitted level of water-soluble As (0.04 mg/kg) in agricultural soils. Arsenic concentrations varied from 0.8 to 149.5 mg/kg dry wt in the plants of site 1 and from 2.0 to 10.0 mg/kg in the plants of site 2. Arsenic concentrations in plants increased in the approximate order: Retama sphaerocarpa < Pteridium aquilinum < Erica australis < Juncus effusus < Phalaris caerulescens < Spergula arvensis in site 1. The soil–plant transfer coefficients for As ranged from 0.001 to 0.21 in site 1 and from 0.004 to 0.016 in site 2. The bioconcentration factor based on water-soluble As of soil varied from 3.2 to 593.9 in the plants of site 1 whereas it varied from 2.1 to 20.7 in the plants of site 2. To our knowledge, this is the first study in Europe to report that the fern species P. aquilinum accumulates extremely low contents of As in its fronds despite high As levels in the soils. Therefore, the S. arvensis, P. caerulescens and J. effusus plant species grown in this area might be used to partly remove the bioavailable toxic As for the purpose of minimization of mining impacts until hypothetical hyperaccumulating and/or transgenic plants could be transplanted for the phytoremediation of As contaminated soils. 相似文献
7.
Xia Dunsheng Jin Ming Liu Xiuming Chen Fahu Ma Jianying Zhao Hui Wang Xunming Wei Haitao 《Frontiers of Earth Science》2007,1(3):275-283
In this study, magnetic techniques were used to characterize the surface soil from different geomorphologies (i.e., sand desert,
oasis, Gobi, and dry lake) in Central Asia. Results demonstrate that the main magnetic minerals in the surface soil are magnetite,
maghaemite and haematite with some paramagnetic materials. Cross plots of M
rs/M
s versus B
cr/B
c and χfd% versus χarm/saturation isothermal remanent magnetization (SIRM) indicate that the main magnetic grain sizes in surface soil are pseudo
single domain (PSD) and multidomain (MD). The samples from West China (i.e., Tarim basin and Junggar basin) are dominated
by magnetic minerals with larger grain size, while those from North China (i.e., Alxa plateau, Erdos plateau, and Mongolia
plateau) are dominated by fine magnetic minerals. The similarity in magnetic mineral constitutions between the Chinese loess
and the surface soils from Central Asia implies that the loess originated from a vast area of arid, semi-arid regions of Central
Asia. The low value of concentration-dependent magnetic parameters indicates that the low concentration of magnetic minerals
in the surface soils from Central Asia and the magnetic enhancement from the pedogenic take place in both the loess and the
paleosols, although the progress is stronger in the latter.
Translated from Quaternary Sciences, 2006, 26(6): 937–946 [译自: 第四纪研究] 相似文献
8.
Copper contamination in soils and vegetables in the vicinity of an abandoned copper mine in China was investigated. The Cu
concentrations of 93 soil samples ranged from 30.4 to 3,191 mg kg−1 soil for a mean of 816.8 mg kg−1 soil. Among 15 samples from a 0 to 20-cm soil layer used for the toxicity characteristic leaching procedure (TCLP) test,
the highest value of Cu-TCLP was 133.8 mg kg−1 soil and the TCLP values were positively correlated with the total Cu content of the soils. The sequential extraction of
soils in the 0–20-, 20–40-, and 40–60-cm soil layers showed that Cu existed mainly in the Fe–Mn oxide fraction, sulfide/organic
fraction, and residual fraction. The copper contamination of 21 species of vegetables from in situ sampling was also examined.
Cu concentrations in the edible portions of Brassica chinensis and Solanum melongena were higher than the FAO/WHO standard (40 mg kg−1 DW). The health risk of copper for local inhabitants from consuming these vegetables was assessed on the basis of the target
hazard quotient. Enriched concentrations of copper were also found in situ in eight cultivars of B. chinensis planted in the fields, with two levels of Cu concentration. The results showed that there is severe copper contamination
in this mine area, and the pollutant in soils show a high risk of leaching into the groundwater and diffusing through the
food chain. 相似文献
9.
María del Carmen Blanco Juan Darío Paoloni Hector Morrás Carmen Fiorentino Mario Eduardo Sequeira Nilda N. Amiotti Oscar Bravo Silvana Diaz Martín Espósito 《Environmental Earth Sciences》2012,66(7):2075-2084
Excessive arsenic concentrations above the Argentinean and WHO guidelines for drinking water (10 μg L−1) affects shallow aquifers of the southern Pampean Plain (Argentina) hosted in the Pampean and the Post Pampean formations
(loess and reworked loess; Plio-Pleistocene–Holocene). Health problems related to high As concentrations in drinking waters
are known as Endemic Regional Chronic Hydroarsenicism. Hydrochemistry of shallow groundwaters and soil geochemistry were investigated
aiming to (1) understand the partition of As in the solid phase and its relationship with unacceptable As concentrations in
waters, (2) identify the provision source of As to groundwaters. Only 5% of the samples had As concentrations <10 μg L−1; in 27% As concentrations ranged from 10 to 50 μg L−1 and in 58% it reached 60–500 μg L−1. The coarse fraction (50–2,000 μm) hosts about 27% of the total As in the solid phase, being positively correlated to Ba
(p < 0.01; r
2 = 0.93). About 70% is included in the <2 μm fraction and had positive correlations of As–Fe (p < 0.05; r
2 = 0.85) and As–Cr (p < 0.05; r
2 = 0.68). Soils and sediment sand fractions of vadose zones are the primary sources of As in shallow groundwater while adsorption–desorption
processes, codisolution–coprecipitation, and evaporation during the dry seasons raise As concentrations in waters exceeding
the guideline value for drinking water. 相似文献
10.
Sudip Jyoti Sahu Bibhash Nath Sharmi Roy Biswapati Mandal Debashis Chatterjee 《Environmental Earth Sciences》2012,65(3):813-821
Groundwater contaminated with arsenic (As), when extensively used for irrigation, causes potentially long-term detrimental
effects to surface soils. Such contamination can also directly affect human health when irrigated crops, such as rice, vegetable
and fruits, are used for human consumption. Therefore, an understanding of the leaching behavior of As in surface soils is
of high importance, because such behavior may increase the bioavailability of As in the soil horizon. In this study, we have
investigated the role of phosphate ions in leaching and bioavailability of As in the soil horizon, where drinking groundwater
contains elevated levels of As (≥50 μg/L). Soil and groundwater samples were characterized in the laboratory and measured
for physical and chemical constituents. The soils are generally neutral to slightly alkaline in character (pH range 7.5–8.1)
with low to moderate levels of free Fe2O3, Al2O3, CaCO3, organic carbon, and clay content. The measured electrical conductivity (mean 599 μS/cm) of the soils demonstrates their
non-saline nature. The Eh values (range −37 to −151 mV) of the groundwater indicate anoxic condition with low to moderate
levels of bicarbonate (range 100–630 mg/L) and phosphate (range 0.002–4.0 mg/L). The arsenic content (range 50–690 μg/L; mean
321 μg/L) in groundwater has exceeded both WHO recommended guideline values (10 μg/L) and the National safe drinking water
limit (50 μg/L). Regression analyses demonstrate that the bioavailability of As in the soil horizon is mainly controlled by
the composition of free Fe2O3 and CaCO3 content of the soils. However, application of P could increase bioavailability of As in the soil horizon and become available
to plants for uptake. 相似文献
11.
Edward Castañeda-Moya Victor H. Rivera-Monroy Robert R. Twilley 《Estuaries and Coasts》2006,29(5):751-764
The structural attributes and zonation patterns of mangrove forests in a dry environmental setting were evaluated in relation
to gradients of soil resources, soil regulators, and hydroperiod between October 2000 and August 2001 in the Gulf of Fonseca,
Honduras. Transects perpendicular to the edge of tidal channels were established at four mangrove sites, each sectioned into
three mangrove zones (fringe, transition, and scrub) based upon distinct tree-height gradients. Porewater sulfide concentrations
among zones were normally below levels of detection (<0.03 mM) and mean redox values ranged from 163.4±9.9 to −42.4±15.8 mv,
indicating slightly reducing conditions in all zones. Mean porewater NOx
− and PO4
3− concentrations were not significantly different among zones and ranged from 3.3±0.5 to 4.5±0.4 μM and from 0.05 ±0.02 to
0.18±0.04 μM, respectively. Soil nitrogen concentrations were 1–3 mg g−1 in all zones, and mean nitrogen:phosphorus atomic ratios were <20 (range: 12.9–14.9), indicative of fertile wetland soils.
Mean basal areas were significantly different among mangrove zones (fringe > transition) and were coupled with differences
in height within species and zones.Avicennia germinans occupied areas with higher elevations associated with higher salinities ranging from 80 to 140 g kg−1 in the dry season.Rhizophora mangle dominated lower elevations where salinities ranged from 38 to 57 g kg−1 in both the dry and wet seasons. Spatial analysis on mangrove seedlings along transects confirmed that seedling distribution
along the intertidal profile was statistically correlated with conspecific adults, indicating that survival and growth of
seedlings in different intertidal locations are closely matched to canopy membership. The sharp transition (<100 m) in forest
structure and distribution of mangrove species along the intertidal zone of subhumid coastal environments demonstrate common
zonation patterns where species distribution and species-specific habitat suitability are mediated closely with tolerance
to soil regulators (high soil salinity) rather than resource availability. 相似文献
12.
X. J. Wang R. M. Liu K. Y. Wang J. D. Hu Y. B. Ye S. C. Zhang F. L. Xu S. Tao 《Environmental Geology》2006,49(8):1208-1216
Polycyclic aromatic hydrocarbons (PAHs) in soil originate from various sources under different spatial scales. Coregionalization
analysis is more revealing than univariate geostatistical analysis. Scale-dependent spatial features of variables reflect
different sources of spatial variability. In this study, 188 topsoil samples in the Tianjin area were collected. The contents
of 16 PAHs and soil background properties were determined for all samples. A multivariate geostatistical approach was used
for multi-scale spatial analysis for PAH compounds. Results show that coal combustion was the major source for the spatial
distribution patterns of PAHs in the topsoil of the studied area. It worked mainly at the short-range scale (5–10 km). Significant
spatial variation patterns were identified. In contrast, no significant spatial distribution trends at the nugget (0–5 km)
or long-range scales (10–50 km) were seen. Long-range transport and site contamination of PAHs might not be key contributors
in forming the distribution pattern of PAHs in the topsoil of Tianjin area. 相似文献
13.
Heavy metals and rare earth elements (REEs) in soil from the Nam Co Basin,Tibetan Plateau 总被引:1,自引:0,他引:1
Chaoliu Li Shichang Kang Xiaoping Wang F. Ajmone-Marsan Qianggong Zhang 《Environmental Geology》2008,53(7):1433-1440
Twenty-eight soil samples collected from the Nam Co Basin, Tibetan Plateau, have been analyzed for heavy metals (Cd, Cr, Ni,
Cu, Zn, Pb and Mn), arsenic (As) and rare earth elements (REEs). In addition, for establishing the basic physio-chemical characteristics
of the soil, pH, total organic concentration, electrical conductivity, and effective cation exchange capacity were measured.
The results indicate that soil in the Nam Co Basin is still at an early alkaline weathering stage (pH = 7.94). Mean concentrations
of heavy metals and As decreased as follows: Mn > Cr > Zn > Pb > Ni > Cu > As > Cd. The values of Cd, Cr, As, Pb and REEs
in soil from the Nam Co Basin are higher relative to averaged background values over China. The chondrite-normalized diagrams
of REEs suggest high REE(ΣLa → Eu)—enrichment, HREE(ΣGd → Lu)—depletion and Eu—depletion. Vertical profiles indicate that
both heavy metals (except As) and REEs primarily exist in the surface soil. However, heavy metals and REEs vary in the surface
soil between the southern and the northern bank of Nam Co. These differences are controlled mainly by parent materials. 相似文献
14.
Taking limestone soil and yellow soil, the two major soil types in karst areas as examples, analyzing stable carbon isotope composition (δ13C value) of soil organic matter (SOM) in bulk soils and particle-size fractions of four soil profiles under three vegetable forms, the following results are reached: in the limestone soil profile, soil organic carbon contents are all above 1.0%, the highest value is 7.1% in the surface soil; however, they are between 0.3% and 4.6% in the three yellow soil profiles. From the surface to the bottom of the soil profiles, the variation of δ13C value of soil organic carbon for limestone soil profile is only between −24.1‰ and −23.0‰, however, it’s between −24.8‰ and −21.1‰ for yellow soil profiles. The variation range of δ13C value of soil organic carbon associated with particle-size separates is slight for limestone soil but is considerable for yellow soil. The contrast research indicates that the changes between the contents and the δ13C value of soil organic carbon with depth are complex. The vertical patterns of stable carbon isotope in soil organic matter have a distinct regional characteristic in karst areas. 相似文献
15.
Keming Tian Jingshi Liu Shichang Kang Iain B. Campbell Fei Zhang Qianggong Zhang Wei Lu 《Environmental Geology》2009,57(8):1775-1784
Hydrothermal processes and the regimes of frozen soil formed in alpine regions with glaciers and lake area are complex and
important for ecological environment but have not been studied in Tibet. Based on soil temperature and moisture data from
October 2005 to September 2006 collected in the Nam Co lake basin, Tibetan Plateau (TP), those questions were discussed. The
mean annual air temperature was −3.4°C with 8 months below 0°C. Air and soil temperature varied between −25.3~13.1°C and −10.3~8.8°C,
respectively. Soil moisture variations in the active layer were small with the minimum value of 1.4%, but were influenced
greatly by snowmelt, rainfall and evaporation, varying up to 53.8%. The active layer froze later, thawed earlier and was thinner,
however, the lower altitude limit of permafrost is higher than that in most areas of TP. The effects of soil moisture (unfrozen
water content) on soil temperature, which were estimated through proposed models, were more significant near ground surface
than the other layers. The surface soil temperature decreased with snowcover, the effect of cold snow meltwater infiltration
on soil thermal conditions was negligible, however, the effect of rainfall infiltration was evident causing thermal disruptions. 相似文献
16.
A. Cachada S. M. Rodrigues C. Mieiro E. Ferreira da Silva E. Pereira A. C. Duarte 《Environmental Geology》2009,57(1):91-98
This study aims at assessing the extent of total mercury (Hg) contamination in urban and agricultural soils under long-term
influence of a chlor-alkali plant, located at about 1 km away from a town centre. Moreover, it aims at identifying the main
factors controlling Hg contents’ distribution and associated potential hazards to environment and human health. The median
value of total Hg for soil surface layer (0–10 cm) was 0.20 mg/kg (data ranging from 0.050 to 4.5 mg/kg) and for subsurface
layer (10–20 cm) 0.18 mg/kg (data ranging from 0.046 to 3.0 mg/kg). The agricultural area showed higher Hg concentrations
(ranging from 0.86 to 4.5 mg/kg) than urban area (ranging from 0.05 to 0.61 mg/kg), with some results exceeding target values
set by the Dutch guidelines. Mercury concentrations observed in the studied area are more likely to be associated with the
influence of the chlor-alkali plant and with the use of historically contaminated sludges and water from a nearby lagoon in
agriculture, than to the impacts of urban development. The statistical correlations between Hg concentrations and soil properties
suggest that anthropogenic metal sources should influence the spatial distribution more than the geological properties. Although
the Hg emissions were drastically reduced 10 years ago, the area under influence of the chlor-alkali plant is still facing
potential health and environmental threats arising from soil contamination. 相似文献
17.
P. Conde Bueno E. Bellido J. A. Martín Rubí R. Jiménez Ballesta 《Environmental Geology》2009,56(5):815-824
Mercury (Hg) is one of the elements with increasing environmental significance. A total of 22 samples (soils, rocks and gels)
were collected along a 6 km transect around the Valdeazogues River valley in the southwest of the Iberian Peninsula (Almadén,
Spain). Samples were characterized by different soil types of depositional sequences associated with mining tailings, type
and system tracts: 15 surface soil samples included in the transect; 3 of a Haploxerept soil profile developed on slates;
2 of quartzite and slates rocks (reference rocks in the area). Moreover, two of a gel substance (in the lower tract of the
river). Soil samples were analyzed for Hg, Cu, Ni, Cr, V, Pb, Cd and As, as well as for organic matter, pH abrasion and calcium
carbonate content. All samples were collected from the Almadén mining district. The level of occurrence of the elements (especially
Hg) and the effect of some properties on its concentration distributions were investigated. The total mercury contents varied
in the range 7,315–3.44 mg kg−1. The mean concentration of total mercury in soils and rocks was 477.03 mg kg−1dry mass. This value is very high compared to the regional background value of other areas. Only rarely is it higher than
1%: in one sample (7,315 mg kg−1) it was almost eight times in comparison with the affected zones, with a high value of 1,000 mg kg−1. Significant differences between samples were found in the total content of mercury. A large percentage of the samples registered
detectable levels of V, Cr, Ni, Pb, As and Cu. Cd readings were below the detectable range for all samples tested. Cr mean
concentration was 216.95 mg kg−1 (minimun concentration 86, maximun 358); V mean concentration was 119.09 mg kg−1 (minimun concentration 69, maximun 1,209); As mean concentration was 51.24 mg kg−1 (minimun 13.3 and maximun 319.4); Ni mean concentration was 45.64 mg kg−1 (minimun concentration 21.2 and maximun 125.6); Cu mean concentration was 33.25 mg kg−1 (minimun concentration 19.3 and maximun 135); Pb mean concentration was 15.19 mg kg−1 (minimun 1.12 and maximun 1013). Metal distribution generally showed spatial variability ascribed to significant anthropogenic
perturbation by mining tailing type. Hg showed vertical profile characterized by surface enrichment, with concentrations in
the upper layer (93.7–82.2 mg kg−1 in front of 3.4 of the rock value) exceeding, in several occasions, the background value. The results obtained denote a potential
toxicity of some heavy metals in some of the studied samples. Water-soluble mercury could enter the aquatic system and accumulate
in sediments. Mercury and other heavy metals contamination depended on the duration and intensity of mining activities. 相似文献
18.
J. Zhang 《Physics and Chemistry of Minerals》2000,27(3):145-148
Isobaric volume measurements for MgO were carried out at 2.6, 5.4, and 8.2 GPa in the temperature range 300–1073 K using
a DIA-type, large-volume apparatus in conjunction with synchrotron X-ray powder diffraction. Linear fit of the thermal expansion
data over the experimental pressure range yields the pressure derivative, (∂α/∂P)
T
, of −1.04(8) × 10−6 GPa−1 K−1 and the mean zero-pressure thermal expansion α0,
T
= 4.09(6) × 10−5 K−1. The α0,
T
value is in good agreement with results of Suzuki (1975) and Utsumi et al. (1998) over the same temperature range, whereas
(∂α/∂P)
T
is determined for the first time on MgO by direct measurements. The cross-derivative (∂α2/∂P∂T) cannot be resolved because of large uncertainties associated with the temperature derivative of α at all pressures. The
temperature derivative of the bulk modulus, (∂K
T/∂T)
P
, of −0.025(3) GPa K−1, obtained from the measured (∂α/∂P)
T
value, is in accord with previous findings.
Received: 2 April 1999 / Revised, accepted: 22 June 1999 相似文献
19.
An analytical method has been proposed to predict the ultimate uplift capacity of single vertical piles embedded in sand considering
arching effect. The present analysis takes into consideration of various pile and soil parameters such as length (L), diameter (d) of the pile, angle of internal friction of soil (ϕ), soil pile friction angle (δ) and unit weight of soil (γ). A modified value of coefficient of lateral earth pressure in uplift has been developed considering the arching effect of
soil. A comparative assessment of the uplift capacity of piles predicted by using proposed theory and the existing available
theories is made with the existing field and model test results. It has been observed that the present model considering the
arching effect predicts the results closer. 相似文献
20.
Role of selected riparian herbs in reducing soil erosion and nutrient loss under simulated rainfall 总被引:3,自引:2,他引:1
The native riparian herbs such as Leonotis nepetaefolia (L.) R. Br., Cassia tora L., Ageratum conyzoides L., Parthenium hysterophorus L. and Sida acuta burm f., dominant on the bank of River Damodar in Eastern Jharia Area, Dhanbad (India), were selected to assess experimentally
their quantitative role in conserving the soil and reducing water runoff and nutrient (N and P) losses. A total of 42.5 mm
simulated rainfall were applied at 30 cm h−1 rain intensity on both vegetated and bare plots. The collected runoff water and eroded soil from each plot were determined
in terms of soil, water and nutrient conservation value (CV). Among the vegetated plots, soil CV ranged from 30 to 85% and
water CV from 20 to 48%. Nutrient (N and P) CV varied from 22 to 65% for total-N, 48 to 80% for ammonia-N and 50 to 86% for
nitrate-N. CV for total-P varied from 40 to 62%, inorganic-P from 42 to 60% and organic-P from 20 to 58%. In a stepwise multiple
regression equation comprising four independent variables (canopy cover, litter mass, soil moisture and plant biomass), canopy
cover explained 70–88% (P < 0.01) of variability in conserving soil, water and nutrient. The losses through runoff water and eroded soil from vegetated
plots were found to be minimized to a great extent as compared to bare plots. The role of these species in maintaining the
texture and fertility status of riparian soil is discussed. 相似文献