共查询到20条相似文献,搜索用时 15 毫秒
1.
Changes in soil quality indicators under long-term sewage irrigation in a sub-tropical environment 总被引:3,自引:0,他引:3
Reginald Ebhin Masto Pramod K. Chhonkar Dhyan Singh Ashok K. Patra 《Environmental Geology》2009,56(6):1237-1243
Though irrigation with sewage water has potential benefits of meeting the water requirements, the sewage irrigation may mess
up to harm the soil health. To assess the potential impacts of long-term sewage irrigation on soil health and to identify
sensitive soil indicators, soil samples were collected from crop fields that have been irrigated with sewage water for more
than 20 years. An adjacent rain-fed Leucaena leucocephala plantation system was used as a reference to compare the impact of sewage irrigation on soil qualities. Soils were analyzed
for different physical, chemical, biological and biochemical parameters. Results have shown that use of sewage for irrigation
improved the clay content to 18–22.7%, organic carbon to 0.51–0.86% and fertility status of soils. Build up in total N was
up to 2,713 kg ha−1, available N (397 kg ha−1), available P (128 kg ha−1), available K (524 kg ha−1) and available S (65.5 kg ha−1) in the surface (0.15 m) soil. Long-term sewage irrigation has also resulted a significant build-up of DTPA extractable Zn
(314%), Cu (102%), Fe (715%), Mn (197.2), Cd (203%), Ni (1358%) and Pb (15.2%) when compared with the adjacent rain-fed reference
soil. Soils irrigated with sewage exhibited a significant decrease in microbial biomass carbon (−78.2%), soil respiration
(−82.3%), phosphatase activity (−59.12%) and dehydrogenase activity (−59.4%). An attempt was also made to identify the sensitive
soil indicators under sewage irrigation, where microbial biomass carbon was singled out as the most sensitive indicator. 相似文献
2.
Effects of nitrogen fertilization on soil respiration in temperate grassland in Inner Mongolia,China 总被引:5,自引:0,他引:5
Qin Peng Yunshe Dong Yuchun Qi Shengsheng Xiao Yating He Tao Ma 《Environmental Earth Sciences》2011,62(6):1163-1171
Nitrogen addition to soil can play a vital role in influencing the losses of soil carbon by respiration in N-deficient terrestrial
ecosystems. The aim of this study was to clarify the effects of different levels of nitrogen fertilization (HN, 200 kg N ha−1 year−1; MN, 100 kg N ha−1 year−1; LN, 50 kg N ha−1 year−1) on soil respiration compared with non-fertilization (CK, 0 kg N ha−1 year−1), from July 2007 to September 2008, in temperate grassland in Inner Mongolia, China. Results showed that N fertilization
did not change the seasonal patterns of soil respiration, which were mainly controlled by soil heat-water conditions. However,
N fertilization could change the relationships between soil respiration and soil temperature, and water regimes. Soil respiration
dependence on soil moisture was increased by N fertilization, and the soil temperature sensitivity was similar in the treatments
of HN, LN, and CK treatments (Q
10 varied within 1.70–1.74) but was slightly reduced in MN treatment (Q
10 = 1.63). N fertilization increased soil CO2 emission in the order MN > HN > LN compared with the CK treatment. The positive effects reached a significant level for HN
and MN (P < 0.05) and reached a marginally significant level for LN (P = 0.059 < 0.1) based on the cumulative soil respiration during the 2007 growing season after fertilization (July–September
2007). Furthermore, the differences between the three fertilization treatments and CK reached the very significant level of
0.01 on the basis of the data during the first entire year after fertilization (July 2007–June 2008). The annual total soil
respiration was 53, 57, and 24% higher than in the CK plots (465 g m−2 year−1). However, the positive effects did not reach the significant level for any treatment in the 2008 growing season after the
second year fertilization (July–September 2008, P > 0.05). The pairwise differences between the three N-level treatments were not significant in either year (P > 0.05). 相似文献
3.
R. E. Masto L. C. Ram P. R. Shandilya S. Sinha J. George V. A. Selvi 《Environmental Earth Sciences》2011,64(4):1107-1115
Coal handling, crushing, washing, and other processes of coal beneficiation liberate coal particulate matter, which would
ultimately contaminate the nearby soils. In this study, an attempt was made to determine the status of soil bio-indicators
in the surroundings of a coal beneficiation plant, (in relation to a control site). The coal beneficiation plant is located
at Sudamudih, and the control site is 5 km away from the contaminated site, which is located in the colony of Central Institute
of Mining and Fuel Research Institute, Digwadih, Dhanbad. In order to estimate the impact of coal deposition on soil biochemical
characteristics and to identify the most sensitive indicator, soil samples were taken from the contaminated and the control
sites, and analyzed for soil organic carbon (SOC), soil N, soil basal respiration (BSR), substrate-induced respiration (SIR),
and soil enzymes like dehydrogenase (DHA), catalase (CAT), phenol oxidase (PHE), and peroxidase (PER). Coal deposition on
soils improved the SOC from 10.65 to 50.17 g kg−1, CAT from 418.1 to 804.11 μg H2O2 g−1 h−1, BSR from 8.5 to 36.15 mg CO2–C kg−1 day−1, and SIR from 24.3 to 117.14 mg CO2–C kg−1 day−1. Soils receiving coal particles exhibited significant decrease in DHA (36.6 to 4.22 μg TPF g−1 h−1), PHE (0.031 to 0.017 μM g−1 h−1), PER (0.153 to 0.006 μM g−1 h−1), and soil N (55.82 to 26.18 kg ha−1). Coal depositions significantly (P < 0.01) decreased the DHA to 8.8 times, PHE to 1.8 times, and PER to 25.5 times, but increased the SOC to 4.71 times, CAT
to 1.9 times, SIR to 4.82 times, and BSR to 4.22 times. Based on principal component analysis and sensitivity test, soil peroxidase
(an enzyme that plays a vital role in the degradation of the aromatic organic compounds) is found to be the most important
indicator that could be considered as biomarkers for coal-contaminated soils. 相似文献
4.
Xu Naizheng Zhang Taolin Wang Xingxiang Liu Hongying 《Environmental Earth Sciences》2011,63(5):1021-1028
Soil carbon sequestration plays an essential role in mitigating CO2 increases and the global greenhouse effect. This paper calculates soil organic carbon (SOC) storage changes during the course
of industrialization and urbanization in Yangtze Delta region, China, based on the data of the second national soil survey
(1982–1985) and the regional geochemical survey (2002–2005), with the help of remote sensing images acquired in periods of
1980, 2000, 2005. The results show that soils in the top 0–20 and 0–100 cm depth in this region demonstrate the carbon sink
effect from the early 1980s to the early 2000s. The SOC storage in 0–20 cm depth has resulted in increase from 213.70 to 238.65 Tg,
which corresponds to the SOC density increase from 2.94 ± 1.08 to 3.28 ± 0.92 kg m−2, and mean carbon sequestration storage and rate are 1.25 Tg a−1, 17.14 g m−2 a−1, respectively. The SOC storage in 0–100 cm depth has resulted in increase from 690.26 to 792.65 Tg, which corresponds to
the SOC density increase from 9.48 ± 4.22 to 10.89 ± 3.42 kg m−2, and mean carbon sequestration storage and rate are 5.12 Tg a−1, 70.32 g m−2 a−1, respectively. Urban area in Yangtze Delta region, China, increased more than 3,000 km2 and the urban growth patterns circled the central city region in the past 20 years. The SOC densities in 0–20 cm depth decrease
gradually along urban–suburban–countryside and the urban topsoil is slightly enriched with SOC. Compared to the data of the
second national soil survey in the early 1980s, the mean SOC density in urban area increased by 0.76 kg m2, or up 25.85% in the past 20 years. With the characteristics of SOC storage changes offered, land-use changes, farming system
transition and ecological city construction are mainly attributed to SOC storage increases. Because of lower SOC content in
this region, it is assumed that the carbon sink effect will go on in the future through improved soil management. 相似文献
5.
Ahmed Melegy Igor Slaninka Tomas Pa?es Stanislav Rapant 《Environmental Earth Sciences》2011,64(2):549-555
Inputs of As to a small catchment due to chemical weathering of bedrock, mechanical weathering of bedrock, and atmospheric
precipitation were 71.53, 23.98 and 0.02 g ha−1 year−1, respectively. The output fluxes of As due to mechanical erosion of soil, biological uptake, stream discharge, and groundwater
flow were 6.32, 4.77, 0.37 and 0.02 g ha−1 year−1, respectively. The results indicate that arsenic accumulates in soil and regolith with a very high rate. This is attributed
to the selective weathering and erosion with respect to arsenic and fixation of arsenic in the secondary solids produced by
weathering. The output fluxes of As in stream and groundwater in Vydrica catchment in Slovak Republic (0.39 g ha−1 year−1) based on muscovite–biotite granites and granodiorites were much lower compared to catchments in a gold district in the Czech
Republic. These results may be ascribed to the low levels of arsenic pollution measured in Vydrica catchment. The arsenic
fluxes were estimated by calculation of mechanical and chemical weathering rates of the bedrocks in Vydrica catchment from
mass balance data on sodium and silica. The justification of the steady state of Na and Si is that neither of the elements
is appreciably accumulated in plants and in exchangeable pool of ions in soil. 相似文献
6.
Claire M. C. Rambeau Denis Baize Nicolas Saby Virginie Matera Thierry Adatte Karl B. Föllmi 《Environmental Earth Sciences》2010,61(8):1573-1585
Cadmium (Cd) is a highly toxic element and its presence in the environment needs to be closely monitored. Recent systematic
surveys in French soils have revealed the existence of areas in eastern and central France, which show systematically high
cadmium concentrations. It has been suggested that at least part of these anomalous levels are of natural origin. For the
Lower Burgundy area in particular, a direct heritage from the Jurassic limestone bedrock is highly suspected. This potential
relationship has been studied in several localities around Avallon and this study reports new evidence for a direct link between
anomalously elevated cadmium contents of Bajocian and Oxfordian limestone and high cadmium concentrations in deriving soils.
Soils in this area show cadmium concentrations generally above the average national population values, with contents frequently
higher than the ‘upper whisker’ value of 0.8 μg g−1 determined by statistical evaluation. In parallel, limestone rocks studied in the same area exhibit cadmium concentrations
frequently exceeding the mean value of 0.030–0.065 μg g−1 previously given for similar rocks by one order of magnitude, with a maximum of 2.6 μg g−1. Mean ratios between the cadmium concentrations of limestone bedrock and deriving soils (Cdsoil/Cdrock), calculated for different areas, range from 4.6 to 5.7. Calculations based on the analyses of both soils from a restricted
area and fragments of bedrock sampled in the immediate vicinity of high-concentration soils are around 5.5–5.7. Cdsoil/Cdrock is useful in determining the potential of soils in Lower Burgundy to reflect and exacerbate the high concentrations of cadmium
present in parent bedrocks. 相似文献
7.
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
8.
M. M. Saç E. Yumurtaci G. Yener B. Camgöz A. Uğur B. Özden 《Environmental Geology》2008,55(3):477-483
Gediz Basin is one of the regions where intense agricultural activities take place in Western Turkey. Erosion and soil degradation
have long been causing serious problems to cultivated fields in the basin. This work describes the application of two different
137Cs models for estimating soil erosion rates in cultivated sites of the region. Soil samples were collected from five distinct
cultivated regions subject to soil erosion. The variations of 137Cs concentrations with depth in soil profiles were investigated. Soil loss rates were calculated from 137Cs inventories of the samples using both proportional model (PM) and simplified mass balance model (SMBM). When PM was used,
erosion and deposition rates varied from −15 to −28 t ha−1 year−1 and from +5 to +41 t ha−1 year−1, respectively; they varied from −16 to −33 t ha−1 year−1 and from +5 to +55 t ha−1 year−1 with SMBM. A good agreement was observed between the results of two models up to 30 t ha−1 year−1 soil loss and gain in the study area. Ulukent, a small representative agricultural field, was selected to compare the present
data of 137Cs techniques with the results obtained by universal soil loss equation (USLE) applied in the area before. 相似文献
9.
Studying spatial and temporal variation of soil loss is of great importance because of global environmental concerns. Understanding
the spatial distribution of soil erosion and deposition in the high-cold steppe is important for designing soil and water
conservation measures. Measured 137Cs losses (Bq m−2) from long-term high altitude (4,000 m above sea level) watershed plots on the Qinghai–Tibet plateau and derived soil erosion
estimates (Mg ha−1 year−1) were significantly correlated to directly measured soil losses from the same plots, over the same period (1963–2005). The
local reference inventory was estimated to be 2,468 Bq m−2. The result of analyzing 137Cs distribution and its intensity in the soil profiles in this area shows similarities to 137Cs distribution in other areas. 137Cs is basically distributed in the topsoil layer of 0–0.3 m. Soil erosions vary greatly in the entire sampled area, ranging
from 5.5 to 23 Mg ha−1 year−1, with an average of 16.5 Mg ha−1 year−1 which is a moderate rate of erosion. 相似文献
10.
Mohsen Jalali 《Environmental Geology》2009,57(5):1011-1020
In areas of intensive crop production, continual phosphorous (P) applications as P fertilizer and farmyard manure have been
made at levels exceeding crop requirement. As a result, surface soil accumulations of P have occurred to such an extent that
loss of P in surface runoff and a high risk for P transfer into groundwater in concentrations exceeding the groundwater quality
standard has become a priority management concern. Phosphorous content of groundwater was determined in order to examine dissolved
P concentration and species in the groundwater and mineral solubilitiy in a semi-arid region of southern Malayer, western
Iran. The speciation for P in groundwater was calculated using geochemical speciation model PHREEQC. The concentration of
total P in the groundwater (0.01–2.56 mg P l−1) and estimated concentrations of HPO4
2− (49.5–89%), H2PO4
− (1.5–17.3%), CaHPO4
+ (5.7–36.1%), and CaPO4
− (1.4–12.2%) varied considerably amongst the groundwater. Results suggest that the concentration of P in the groundwater could
be primarily controlled by the solubility of octacalcium phosphate and β-tricalcium phosphate. Large amounts of P fertilizer,
inadequate management of P fertilization, and low irrigation efficiency, coupled with sandy soils in some parts of the study
area could be mainly responsible for the greater P in the groundwater. In general, the greater the dissolved P concentration
in the groundwater, the closer the solution was to equilibrium with respect to the more soluble Ca-phosphate minerals. The
groundwater P content could be potentially used to identify areas where management approaches, such as P applied and crop
type planted, could be adjusted to different types of soils, geology and topography. 相似文献
11.
Source and distribution of trace metals and nutrients in Narmada and Tapti river basins,India 总被引:2,自引:1,他引:1
The study was designed to establish the distributions of trace metals, dissolved organic carbon, and inorganic nutrients as
well as to assess the extent of anthropogenic inputs into the Narmada and Tapti rivers. Water and sediment qualities are variable
in the rivers, and there are major pollution problems at certain locations, mainly associated with urban and industrial centers.
The metal concentrations of samples of the aquatic compartments investigated were close to the maximum permissible concentration
for the survival of aquatic life, except for higher values of Cu (5–763 μg l−1), Pb (24–376 μg l−1), Zn (24–730 μg l−1), and Cr (70–740 μg l−1) and for drinking water except for elevated concentrations of metals such as Pb, Fe (850–2,060 μg l−1), Cr, and Ni (20–120 μg l−1). In general, the concentrations of trace metals in the rivers vary down stream which may affect the “health” of the aquatic
ecosystem and may also affect the health of the rural community that depends on the untreated river water directly for domestic
use. The assessment of EF, I
geo, and PLI in the sediments reveals overall moderate pollution in the river basins. 相似文献
12.
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
13.
Ilhami Bayramin Mustafa Basaran Gunay Erpul Melda Dolarslan Mustafa R. Canga 《Environmental Geology》2009,56(8):1563-1575
In highlands of semiarid Turkey, ecosystems have been significantly transformed through human actions, and today changes are
taking place very rapidly, causing harmful consequences such as soil degradation. This paper examines two neighboring land
use types in Indagi Mountain Pass, Cankiri, Turkey, to determine effects of the conversion of Blackpine (Pinus nigra Arn. subsp. pallasiana) plantation from grassland 40 years ago on soil organic carbon (SOC) and soil erodibility (USLE-K). For this purpose, a total
of 302 disturbed and undisturbed soil samples were taken at irregular intervals from two sites and from two soil depths of
0–10 cm (D1) and 10–20 cm (D2). In terms of SOC, conversion did not make any statistical difference between grassland and plantation; however, there were
statistically significant differences with soil depth within each land use, and SOC contents significantly decreased with
the soil depth (P < 0.05) and mostly accumulated in D1. SOC values were 2.4 and 1.8% for grassland and 2.8 and 1.6% for plantation, respectively, at D1 and D2. USLE-K values also statistically differed significantly with the land use, and in contrast to the statistics of SOC, there
was no change in USLE-K with the soil depth. Since USLE-K was estimated using SOC, hydraulic conductivity (HC) and soil textural
composition––sand (S), silt (Si), and clay (C) contents of soils––as well as SOC did not change with the land use, we ascribed
the changes of USLE-K with the land uses to the differences in the HC as strongly affected by the interactions between SOC
and contents of S, Si, and C. On an average, the soil of the grassland (USLE-K = 0.161 t ha h ha−1 MJ−1 mm−1) was more erodible than those of the plantation (USLE-K = 0.126 t ha h ha−1 MJ−1 mm−1). Additionally, topographic factors, such as aspect and slope, were statistically effective on spatial distribution of the
USLE-K and SOC. 相似文献
14.
The Cu–Co–Ni Texeo mine has been the most important source of Cu in NW Spain since Roman times and now, approximately 40,000 m3 of wastes from mine and metallurgical operations, containing average concentrations of 9,263 mg kg−1 Cu, 1,100 mg kg−1 As, 549 mg kg−1 Co, and 840 mg kg−1 Ni, remain on-site. Since the cessation of the activity, the abandoned works, facilities and waste piles have been posing
a threat to the environment, derived from the release of toxic elements. In order to assess the potential environmental pollution
caused by the mining operations, a sequential sampling strategy was undertaken in wastes, soil, surface and groundwater, and
sediments. First, screening field tools were used to identify hotspots, before defining formal sampling strategies; so, in
the areas where anomalies were detected in a first sampling stage, a second detailed sampling campaign was undertaken. Metal
concentrations in the soils are highly above the local background, reaching up to 9,921 mg kg−1 Cu, 1,373 mg kg−1 As, 685 mg kg−1 Co, and 1,040 mg kg−1 Ni, among others. Copper concentrations downstream of the mine works reach values up to 1,869 μg l−1 and 240 mg kg−1 in surface water and stream sediments, respectively. Computer-based risk assessment for the site gives a carcinogenic risk
associated with the presence of As in surface waters and soils, and a health risk for long exposures; so, trigger levels of
these elements are high enough to warrant further investigation. 相似文献
15.
Effect of addition of organic residues on phosphorus release kinetics in some calcareous soils of western Iran 总被引:2,自引:0,他引:2
We investigated the effects on phosphorus (P) release of the addition of potato, wheat, and sunflower residues and fruit compost
to five calcareous soils. Residue was added at the rate of 20 g kg−1. After 2 months of incubation, P values in control and amended soils were used for kinetic studies and fractionated by a
sequential extraction procedure. The relative contribution of available P fraction (KCl-P) increased from 1.4% in control
soils to 1.8%, 1.9%, 2.2%, and 2.3% in soils amended by fruit, wheat, potato, and sunflower residue addition, respectively,
indicating that organic residues increased P in this fraction. In soils amended with different residues, the percentage of
Olsen-P released over 86-h successive extractions with 0.01 M CaCl2 ranged from 57.6% for fruit residue addition (average of five soils) to 60.5% for potato residue addition. The ability of
residues to release P depended on the soil properties, with 21.9 mg kg−1 (average of all residues) released to soil 2 and 77.4 mg kg−1 released to soil 4. Also residues behaved differently, with 31.5 mg kg−1 (average of five soils) released by fruit residues and 40.0 mg kg−1 released by sunflower residues. Release of P was best described by a parabolic diffusion model. The corresponding rate constant
(mg kg−1 h−1/2) for P release for amended soils, defined as the release rate averaged for five soils, was found to decrease in the order:
potato (2.73) > sunflower (2.61) > wheat (2.56) > fruit (2.50). The present study demonstrates that addition of residues improves
P availability of these calcareous soils by increasing extractable P and the release rate and could be an alternative, indigenous
source of P. However, the increase in P availability and the release rate following organic residue application suggests high
potential mobility to water sources. 相似文献
16.
Nitrate contamination of groundwater in an agroecosystem in Zhangye Oasis,Northwest China 总被引:5,自引:2,他引:3
In order to assess the extent of groundwater contamination by nitrate (NO3
−–N) and to provide information about the deterioration of the groundwater quality in Zhangye Oasis, Northwest China, a study
was conducted in this area. The mean value of NO3
−–N concentrations in groundwater samples was 10.66 ± 0.19 mg l−1. NO3
−–N concentrations exceeding 10 mg l−1 (the threshold for drinking water set by the World Health Organization) were found in 32.4% of 71 wells, and were 13, 33.3,
52.4 and 50.0% in the groundwater samples from drinking wells, irrigation wells, hand-pumping wells and groundwater table
observation wells, respectively. The result showed that the groundwater samples that had NO3
−–N concentrations exceeding the threshold for drinking water were mostly collected from a depth of less than 20 m. Groundwater
NO3
−–N concentrations in areas used for the cultivation of vegetables, seed maize and intercropped maize were significantly higher
than those in urban or paddy areas. NO3
−–N contamination of groundwater in areas with sandy soil was more severe than in those with loam soil. 相似文献
17.
Compositional fractionation of polyaromatic hydrocarbons in the karst soils, South China 总被引:1,自引:0,他引:1
Yinghui Wang Rui Xue Jie Li Hongxiang Zhu Yiyin Xu Baoming Xue Shihua Qi Daoxian Yuan Oramah I. Theodore 《Environmental Earth Sciences》2012,66(7):2013-2019
This study aims to explore the condensation and fractionation trends of persistent organic pollutants (POPs) in the karst soils. The tiankeng is a karst surface expression that can act as a focal point for introduction of contaminants to a karst aquifer, which may serve both as condenser for vapor phase POPs and as barrier/sink for particulate associated less volatile POPs. The fractionation of POPs in soils from the upper rim and floor of tiankeng is of interest in understanding the role of tiankeng in the long-distance transport of POPs. In the present study, polycyclic aromatic hydrocarbons (PAHs) in the surface soils from the upper rim and floor of Dashiwei tiankeng in Southern China were analyzed. The total PAH concentrations in soils were 23.40–190 ng g−1, with phenanthrene being the most abundant. The distribution patterns of PAH compounds in the soil samples matched well with their properties. It indicated the heavy PAHs were susceptible to retention by the floor soils of tiankeng than light PAHs. A plot of Cfloor/Crim against PAH molecular weight gave a good positive relationship in the molecular weight range of 152–276. It is suggested that the floor soils can be focal points of more concentrated PAH and deserve attention. The concentrations of total PAHs in the floor soils (43.40–190 ng g−1, mean 87.76 ng g−1) were higher than those in the upper rim (23.40–88.94 ng g−1, mean 57.74 ng g−1). In addition, there was a shift in compound pattern with an increase in the proportion of light PAHs (2–3 rings), a decrease in heavy PAHs (5–6 rings) and a relatively stable content of 4-ring PAHs. A combination of particulate scavenging and cold condensation is proposed as the major mechanism for the compositional fractionation of PAHs in the soils from the upper rim and floor of tiankeng. 相似文献
18.
Mohsen Jalali 《Environmental Geology》2007,53(2):365-374
Phosphorus (P) application in excess of plant requirement may result in contamination of drinking water and eutrophication
of surface water bodies. The phosphorous buffer capacity (PBC) of soil is important in plant nutrition and is an important
soil property in the determination of the P release potential of soils. Phosphorus sorption greatly affects both plant nutrition
and environmental pollution. For better and accurate P fertilizer recommendations, it is necessary to quantify P sorption.
This study was conducted to investigate available P and P sorption by calcareous soils in a semi-arid region of Hamadan, western
Iran. The soil samples were mainly from cultivated land. Olsen’s biocarbonate extractable P (Olsen P) varied among soils and
ranged from 10 to 80 mg kg−1 with a mean of 36 mg kg−1. Half of the soils had an Olsen P > 40 mg kg−1 and >70% of them had a concentration >20 mg kg−1, whereas the critical concentration for most crops is <15 mg P kg−1. Greater average Olsen P in soils occurred under garlic (56 mg kg−1) and potato (44 kg kg−1) fields than in dry-land wheat farming (24 mg kg−1), pasture (30 mg kg−1), and wheat (24 mg P kg−1) fields. A marked increase in fertilizer P rates applied to agricultural soils has caused P to be accumulated in the surface
soil. Phosphate sorption curves were well fitted to the Freundlich equation. The standard P requirement (SPR) of soils, defined
as the amount of P sorbed at an equilibrium concentration of 0.2 mg l−1 ranged from 4 to 102 mg kg−1. Phosphorus buffer capacity was relatively high and varied from 16 to 123 l kg−1 with an average of 58 l kg−1. In areas of intensive crop production, continual P applications as P fertilizer and farmyard manure have been used at levels
exceeding crop requirements. Surface soil accumulations of P are high enough that loss of P in surface runoff and a high risk
for P transfer into groundwater have become priority management concerns. 相似文献
19.
Spatio-temporal patterns of agricultural expansion and its effect on watershed degradation: a case from the mountains of Nepal 总被引:1,自引:1,他引:0
K. C. Krishna Bahadur 《Environmental Earth Sciences》2012,65(7):2063-2077
Expansion of agricultural at the cost of forested land is a common cause of watershed degradation in the mountain zones of
developing countries. Many studies have been conducted to demonstrate land use changes in such regions. However, current knowledge
regarding the changes, driving forces and implications of such change within the context of watershed development is limited.
This study analyses changes in spatial patterns of agricultural land use and their consequences for watershed degradation
during the 1976–2000 period along an altitude gradient in a watershed in Nepal, by means of remote sensing, GIS and the universal
soil loss equation. Estimated soil loss ranged from 589 to 620 t ha−1 y−1, while areas of extreme hazard severity (>100 t ha−1) increased from 9 to 14.5% from 1990 to 2000. Spatial distribution of soil loss in 2000 was characterized by 88% of total
soil losses being from upland agricultural areas. The study determined that without considering other forms of land degradation,
only water erosion was responsible for erosion of a substantial area in a short timeframe. Areas under upland cultivation
are in an extremely vulnerable state, with these areas potentially no longer cultivable within a period of 6 years. As sustainability
of the watershed is dependent on forests, continued depletion of forest resources will result in poor economic returns from
agriculture for local people, together with loss of ecosystem services. Thus, in order to achieve the goal of watershed development,
remaining forest lands must be kept under strict protection. 相似文献
20.
A study of arsenic,iron and other dissolved ion variations in the groundwater of Bishnupur District,Manipur, India 总被引:1,自引:1,他引:0
Jayalakshmi Devi Oinam AL. Ramanathan Anurag Linda Gurmeet Singh 《Environmental Earth Sciences》2011,62(6):1183-1195
The presence of arsenic (As) in groundwater and its effect on human health has become an issue of serious concern in recent
years. The present study assessed the groundwater quality of the Bishnupur District, Manipur, with respect to drinking water
standards. Higher concentrations of pH, iron and phosphate were observed at several locations. Phosphate and iron levels were
highest in the pre-monsoon, followed by monsoon and post-monsoon seasons. The arsenic concentrations were highest during post-monsoon
(1–200 μg L−1) as compared to pre-monsoon (1–108 μg L−1) and monsoon (2–99 μg L−1). Kwakta and Ngakhalawai show higher levels of arsenic concentration as compared to the prescribed World Health Organization
(WHO) and Bureau of Indian Standards (BIS) norms. Arsenic showed a strong positive correlation with phosphate and negative
correlation with sulphate, suggesting a partial influence of anthropogenic sources. The study suggests that the Bishnupur
area has an arsenic contamination problem, which is expected to increase in the near future. 相似文献