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1.
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
2.
Environmental geochemistry of high arsenic groundwater at Hetao plain was studied on the basis of geochemical survey of the
groundwater and a core sediment. Arsenic concentration in groundwater samples varies from 76 to 1093 μg/L. The high arsenic
groundwater mostly appears to be weakly alkaline. The concentrations of NO3− and SO42− are relatively low, while the concentrations of DOC, NH4+, dissolved Fe and sulfide are relatively great. Analysis of arsenic speciation in 21 samples shows that arsenic is present
in the solution predominantly as As(III), while particulate arsenic constitutes about 10% of the total arsenic. Methane is
detected in five samples with the greatest content being 5107 μg/L. The shallow aquifer in Hangjinhouqi of western Hetao plain
is of strongly reducing condition. The arsenic content in 23 core sediment samples varies from 7.7 to 34.6 mg/kg, with great
value in clay and mild clay layer. The obvious positive relationship in content between Fe2O3, Mn, Sb, B, V and As indicates that the distribution of arsenic in the sediments may be related to Fe and Mn oxides, and
the mobilization of Sb, B and V may be affected by similar geochemical processes as that of As. 相似文献
3.
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
4.
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
5.
Sarah E. Rothenberg Matthew E. Kirby Broxton W. Bird Margie B. DeRose Chu-Ching Lin Xinbin Feng Richard F. Ambrose Jennifer A. Jay 《Environmental Earth Sciences》2010,60(5):993-1005
In southern California, USA, wildfires may be an important source of mercury (Hg) to local watersheds. Hg levels and Hg accumulation
rates were investigated in dated sediment cores from two southern California lakes, Big Bear Lake and Crystal Lake, located
approximately 40-km apart. Between 1895 and 2006, fires were routinely minimized or suppressed around Big Bear Lake, while
fires regularly subsumed the forest surrounding Crystal Lake. Mean Hg concentrations and mean Hg accumulation rates were significantly
higher in Crystal Lake sediments compared to Big Bear Lake sediments (Hg levels: Crystal Lake 220 ± 93 ng g−1, Big Bear Lake 92 ± 26 ng g−1; Hg accumulation: Crystal Lake 790 ± 1,200 μg m−2 year−1, Big Bear 240 ± 54 μg m−2 year−1). In Crystal Lake, the ratio between post-1965 and pre-1865 Hg concentrations was 1.1, and several spikes in Hg levels occurred
between 1910 and 1985. Given the remote location of the lake, the proximity of fires, and the lack of point sources within
the region, these results suggested wildfires (rather than industrial sources) were a continuous source of Hg to Crystal Lake
over the last 150 years. 相似文献
6.
Among several salt lakes in the Thar Desert of western India, the Sambhar is the largest lake producing about 2 × 105 tons of salt (NaCl) annually. The “lake system” (lake waters, inflowing river waters, and sub-surface brines) provides a
unique setting to study the geo-chemical behavior of uranium isotopes (238U, 234U) in conjunction with the evolution of brines over the annual wetting and evaporation cycles. The concentration of 238U and the total dissolved solids (TDS) in lake water increase from ~8 μg L−1 and ~8 g L−1 in monsoon to ~1,400 μg L−1 and 370 g L−1, respectively, during summer time. The U/TDS ratio (~1 μg g−1 salt) and the 234U/238U activity ratio (1.65 ± 0.05), however, remain almost unchanged throughout the year, except when U/TDS ratio approaches to
3.8 at/or beyond halite crystallization. These observations suggest that uranium behaves conservatively in the lake waters
during the annual cycle of evaporation. Also, uranium and salt content (TDS) are intimately coupled, which has been used to
infer the origin and source of salt in the lake basin. Furthermore, near uniform ratios in evaporating lake waters, when compared
to the ratio in seawater (~0.1 μg g−1 salt and 1.14 ± 0.02, respectively), imply that aeolian transport of marine salts is unlikely to be significant source of
salt to the lake in the present-day hydrologic conditions. This inference is further consistent with the chemical composition
of wet-precipitation occurring in and around the Sambhar lake. The seasonal streams feeding the lake and groundwaters (within
the lake’s periphery) have distinctly different ratios of U/TDS (2–69 μg g−1 salt) and 234U/238U (1.15–2.26) compared to those in the lake. The average U/TDS ratio of ~1 μg g−1 salt in lake waters and ~19 μg g−1 salt in river waters suggest dilution of the uranium content by the recycled salt and/or removal processes presently operating
in the lake during the extraction of salt for commercial use. Based on mass-balance calculations, a conservative estimate
of "uranium sink" (in the form of bittern crust) accounts for ~5 tons year−1 from the lake basin, an estimate similar to its input flux from rivers, i.e., 4.4 tons year−1. 相似文献
7.
Adsorption, desorption and oxidation of arsenic affected by clay minerals and aging process 总被引:20,自引:0,他引:20
Adsorption/desorption and oxidation/reduction of arsenic at clay surfaces are very important to the natural attenuation of
arsenic in the subsurface environment. Although numerous studies have concluded that iron oxides have high affinities for
the adsorption of As(V), very little experimental work has addressed the arsenic attenuation capacities of different clay
minerals and aging process affecting the transformation of arsenic. The abundance of clay minerals in a variety of geochemical
environments and their influence on adsorption of contaminants suggests a need for more experimental work to characterize
the adsorption desorption, and oxidation of arsenic on clay minerals. In this investigation three types of clay mineral were
studied: the 1 : 1 layer clays [halloysite (IN), sedimentary M-kaolinite, and weathered EPK-kaolinite]; the 2 : 1 layer clays
[illite (MT) and illite/montmorillonite (MT)]; the 2 :>: 1 layer clay [chlorite (CA)]. The halloysite and the chlorite had
much greater As(V) adsorption (25–35 folds) than the other clay minerals. The clay minerals had lower As(III) adsorption than
As(V) adsorption, and the adsorption was affected by pH. Desorption of arsenic from the clay minerals was significantly influenced
by the aging process. The quantities of extractable As(III) and As(V) decreased with increasing aging time. The results demonstrated
that oxidation of As(III) to As(V) occurred on the clay surfaces, whereas reduction of As(V) to As(III) was not found in any
of the clay minerals studied. The oxidation of As(III) was affected by the types of clay and aging time.
Received: 22 March 1999 · Accepted: 15 April 1999 相似文献
8.
Ana Carolina Ruiz-Fernández José Luis Marrugo-Negrete Roberth Paternina-Uribe Libia Hascibe Pérez-Bernal 《Estuaries and Coasts》2011,34(6):1117-1128
With the aim of evaluating temporal changes in sedimentation and organic carbon (Corg) supplied over the last ~100 years, a sediment core was collected at Soledad Lagoon, a costal ecosystem surrounded by mangroves,
located in the Cispatá Estuary (Caribbean coast of Colombia). The core sediments were characterized by low concentrations
of calcium carbonate (0.2–2.9%), organic matter (3–8%), total nitrogen (0.11–0.38%), and total phosphorus (0.19–0.65 mg g−1). Fe and Al concentrations ranged from 4% to 5%, and Mn from 356 to 1,047 μg g−1. The 210Pb-derived sediment and mass accumulation rates were 1.54 ± 0.18 mm year−1 and 0.08 ± 0.01 g cm−2 year−1, respectively. The sediment core did not provide evidence of human impact, such as enhancement of primary production or nutrient
enrichment, which may result from recent land uses changes or climate change. The Corg fluxes estimated for Soledad Lagoon core lay in the higher side of carbon fluxes to coastal ecosystems (314–409 g m−2 year−1) and the relatively high Corg preservation observed (~45%) indicate that these lagoon sediments has been a net and efficient sink of Corg during the last century, which corroborate the importance of mangrove areas as important sites for carbon burial and therefore,
long-term sequestration of Corg. 相似文献
9.
Saidur Rahman Chowdhury Ernest K. Yanful Allen R. Pratt 《Environmental Earth Sciences》2011,64(2):411-423
In this study, magnetite–maghemite nanoparticles were used to treat arsenic-contaminated water. X-ray photoelectron spectroscopy
(XPS) studies showed the presence of arsenic on the surface of magnetite–maghemite nanoparticles. Theoretical multiplet analysis
of the magnetite–maghemite mixture (Fe3O4-γFe2O3) reported 30.8% of maghemite and 69.2% of magnetite. The results show that redox reaction occurred on magnetite–maghemite
mixture surface when arsenic was introduced. The study showed that, apart from pH, the removal of arsenic from contaminated
water also depends on contact time and initial concentration of arsenic. Equilibrium was achieved in 3 h in the case of 2 mg/L
of As(V) and As(III) concentrations at pH 6.5. The results further suggest that arsenic adsorption involved the formation
of weak arsenic-iron oxide complexes at the magnetite–maghemite surface. In groundwater, arsenic adsorption capacity of magnetite–maghemite
nanoparticles at room temperature, calculated from the Langmuir isotherm, was 80 μmol/g and Gibbs free energy (∆G0, kJ/mol) for arsenic removal was −35 kJ/mol, indicating the spontaneous nature of adsorption on magnetite–maghemite nanoparticles. 相似文献
10.
Ahmed I. Rushdi Peter U. Clark Alan C. Mix Vasile Ersek Bernd R. T. Simoneit Hai Cheng R. Lawrence Edwards 《Environmental Earth Sciences》2011,62(6):1245-1261
We analyzed speleothem calcite from the Oregon Caves National Monument, southwestern Oregon, to determine the preservation,
distribution, concentrations and sources of aliphatic lipid compounds preserved in the calcite. Maximum speleothem growth
rate occurs during interglaciations and minimum during glacial intervals. Concentrations of the total lipid compounds range
from 0.5 to 12.9 μg g−1. They increase at times of low speleothem growth rate, suggesting dilution, whereas the apparent accumulation rate of lipid
compounds tends to be highest during times of fastest speleothem growth rate. Such increased accumulation generally corresponds
to times of warm (interglacial) climate, suggesting either a greater source of organic materials during interglacial times
and/or greater efficiency of compound capture during more rapid calcite growth. Aliphatic lipid compounds include homologous
n-alkanoic acids, n-alkanols and methyl n-alkanoates and sterols with concentrations ranging from 0.3 to 7.8 μg g−1, 0.4 to 1.1 μg g−1, 0.5 to 9.6 μg g−1 and 0.1 to 2.7 μg g−1, respectively. Minor amounts of branched methyl n-alkanoates and dimethyl n-alkanedioates are also present. The high concentrations of methyl n-alkanoates are the result of esterification reactions of free fatty acids in alkaline solutions with high pH values associated
with the dripping cave waters. The distribution patterns and geochemical parameters and indices indicate that the major sources
of the aliphatic lipids involved leaching from higher plants and microbial residues derived from the soil zone above the cave
system. The estimated percentage of microbial inputs ranged from 42 to 90% of the total lipids and also showed an increase
in accumulation during warm climates. These well-preserved lipid compounds in speleothem calcite could be used as biomarkers
for paleoenvironmental study. 相似文献
11.
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
12.
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
13.
Pyritization of trace metals in estuarine sediments and the controlling factors: a case in Jiaojiang Estuary of Zhejiang Province,China 总被引:1,自引:0,他引:1
Siyuan Ye Edward A. Laws Qiang Wu Shaojun Zhong Xigui Ding Guangming Zhao Shaojun Gong 《Environmental Earth Sciences》2010,61(5):973-982
Three undisturbed sediment samples were collected from the intertidal zone of the Jiaojiang Estuary of Zhejiang Province,
China. The sediments were found to contain remarkably low concentrations of organic carbon (<0.6%) and acid volatile sulfide
(AVS) (<30 μmol g−1). The availability of these two substrates likely constrained sulfate reduction and pyritization of several trace metals,
respectively. This was especially true at one station where AVS concentrations in the upper 20 cm averaged less than 0.05 μmol g−1. Although the depth dependence of the degree of trace metal pyritization was generally consistent with expectations based
on redox conditions, depth profiles of reactive-metal and pyrite-metal concentrations in several cases revealed more complex
behavior and a positive correlation between reactive-metal concentrations and pore water metal concentrations. 相似文献
14.
Namin Koo Kwon-Rae Kim Youn-Jung Choi Sang-Hwan Lee Gary Owens Jeong-Gyu Kim 《Environmental Earth Sciences》2012,65(3):689-697
To determine the appropriate allocation of resources for the future restoration of the abandoned mining district of Kangwon
in Korea, identification of the main pollutants and the main sources discharging these pollutants is crucial. Therefore, a
2-year study was undertaken to quantify the amount of pollutants in the Uchen stream (a potential sink for contamination),
which runs through the district, and to determine the potential sources of these pollutants, including mine drainage and soil.
Arsenic (As) was the main pollutant in mine drainage and soils showing concentrations above the Korean regulated standard
levels of 50 μg L−1 and 50 mg kg−1 for water and soil, respectively. In addition, the pollution index (PI) showed that mine drainages were polluted by As to
a moderate (2 ≤ PI < 3) or strong (4 ≤ PI < 5) degree. Consequently, As load in mine drainage and soil contributed to increased
amounts of As in the stream. The As loads in mine drainages (11 and 587 g month−1 for mine adit 1 and 2, respectively) accounted for only 9% of the total As load to the stream (6,378 g month−1); and the influence of mine drainages on As contents in the stream was more reliant on the total volume of mine drainage
generated rather than the As concentration in the mine drainage. Approximately 91% of the As in the stream was derived from
the soils within the study area. 相似文献
15.
Arsenic Geochemistry of the Great Dismal Swamp,Virginia, USA: Possible Organic Matter Controls 总被引:1,自引:0,他引:1
Shama E. Haque Jianwu Tang William J. Bounds David J. Burdige Karen H. Johannesson 《Aquatic Geochemistry》2007,13(4):289-308
Surface water samples for arsenic (As) concentration and speciation analysis were collected from organic matter-rich blackwaters
of the Lake Drummond portion of the Great Dismal Swamp in southeastern Virginia, USA. Arsenic concentrations and speciation
were determined by selective hydride generation, gas chromatography with photoionization detection. Surface waters from the
Great Dismal Swamp are high in dissolved organic carbon (DOC) concentrations (445–9,600 μmol/kg) and of low pH (4.2–6.4).
Total dissolved As concentrations [i.e., As(III) + As(V)], hereafter AsT, range from 2.2 nmol/kg to 21.4 nmol/kg. Arsenite, As(III), concentrations range from ∼1 nmol/kg to 17.7 nmol/kg, and As(V)
ranges from ∼1 nmol/kg to 14.1 nmol/kg. Arsenate, As(V), is the predominant form of dissolved As in the inflow waters to the
Great Dismal Swamp, whereas within the swamp proper arsenite, As(III), dominates. Arsenite accounts for 8–37% of AsT in inflow waters west of the Suffolk Scarp, and between 54% and 81% of AsT in Lake Drummond and Great Dismal Swamp waters east of the scarp. Arsenite is strongly correlated to DOC (r = 0.94) and inversely related to pH (r = −0.9), both at greater than the 99% confidence level. Arsenate is weakly related to pH and DOC (r = 0.4 and −0.37, respectively), and neither relationship is statistically significant. No statistical relationships exist
between As(V) or As(III) and PO4 concentrations. The predominance of As(III) and its strong correlation with DOC in Great Dismal Swamp waters suggest that
DOC may inhibit As(III) adsorption or form stable aqueous complexes with As(III) in these waters. Alternatively, phytoplankton
and/or bacterially mediated reduction of As(V) may be important processes in the organic-rich blackwaters and/or sediment
porewaters of the swamp, leading to the prevalence of As(III) in the water column. 相似文献
16.
A. C. Ruiz-Fernández M. Frignani C. Hillaire-Marcel B. Ghaleb M. D. Arvizu J. R. Raygoza-Viera F. Páez-Osuna 《Estuaries and Coasts》2009,32(3):551-564
210Pb geochronologies of Cd, Cu, Hg, and Pb fluxes were obtained from the intertidal mudflat sediments of the coastal lagoons
Chiricahueto, Estero de Urías, and Ohuira in the Mexican Pacific. The Cu and Hg sediment concentrations at the three lagoons
fell within the ranges of 6–76 μg g−1 and 0.1 to 592 ng g−1, respectively; Chiricahueto and Estero de Urías sediments had comparable Cd and Pb concentrations within the ranges of 0.2–2.1 μg
g−1 and 10–67 μg g−1, respectively; whereas in Ohuira lagoon, Cd concentrations were lower (0.1–0.5 μg g−1) and Pb concentrations were higher (115–180 μg g−1) than in the other lagoons. The metal fluxes (μg cm−2 y−1) for the three lagoons fell within the ranges of 0.02–0.15 for Cd, 0.7–6.0 for Cu, 0.001–0.045 for Hg, and 0.7–20 for Pb.
The Hg pollution in Estero de Urías was attributed to the exhausts of the thermoelectric plant of Mazatlan and the metal enrichment
in Chiricahueto and Ohuira was related to the agrochemical wastes from the croplands surrounding these lagoons. 相似文献
17.
Geochemical study of arsenic and other trace elements in groundwater and sediments of the Old Brahmaputra River Plain,Bangladesh 总被引:1,自引:1,他引:0
Faruque Ahmed M. Hawa Bibi Hiroaki Ishiga Takehiko Fukushima Teruyuki Maruoka 《Environmental Earth Sciences》2010,60(6):1303-1316
The geochemical study of groundwaters and core sediments from the Old Brahmaputra plain of Bangladesh was conducted to investigate
the distribution of arsenic and related trace elements. Groundwaters from tube wells are characterized by pH of 6.4–7.4, dissolved
oxygen (DO) of 0.8–1.8 mg/l, Ca contents of 5–50 mg/l, and Fe contents of 0.2–12.9 mg/l. Arsenic concentrations ranged from
8 to 251 μg/l, with an average value of 63 μg/l. A strong positive correlation exists between As and Fe (r
2 = 0.802; p = 0.001) concentrations in groundwater. The stratigraphic sequences in the cores consist of yellowish silty clays at top,
passing downward into grayish to yellowish clays and sands. The uppermost 3 m and lower parts (from 13 to 31 m) of the core
sediments are oxidized (average oxidation reduction potential (ORP) +170 and +220 mV, respectively), and the ORP values gradually
become negative from 3 to 13 m depths (−35 to −180 mV), indicating that anoxic conditions prevail in the shallow aquifers
of the Brahmaputra plain. Age determinations suggest that clay horizons at ~10 m depth were deposited at around 2,000 and
5,000 years BP (14C ages) during the transgressive phase of sea-level change. Elevated concentrations of As, Pb, Zn, Cu, Ni, Cr, and V are present
in the silts and clays, probably due to adsorption onto clay particles. Significant concentrations of As occur in black peat
and peaty sediments at depths between 9 and 13 m. A strong positive correlation between As and Fe was found in the sediments,
indicating As may be adsorbed onto Fe oxides in aquifer sediments. 相似文献
18.
Trends in phosphatase activity along a successional gradient of tidal freshwater marshes on the Cooper River South Carolina 总被引:1,自引:0,他引:1
Phosphatase activity was measured in sediments from tidal freshwater habitats adjacent to the Cooper River in South Carolina
representing different stages of ecological succession. It was found that sediment (0–5 cm) acid phosphatase activity, alkaline
phosphatase activity and phosphodiesterase activity increased with increasing successional stage and phytomass. Acid phosphatase
activity in creased from 7.5±1.2 (±1 SD) in subtidal sediment from a shallow open water habitat without vegetation to 61.2±4.9
μmol g−1 hr−1 (μmol of p-nitrophenol released per gram of dry sediment per hour) in intertidal sediments colonized by emergent macrophytes,
while alkaline phosphatase activity increased from 2.1±0.1 to 19.01±1.5 μmol g−1 hr−1. Phosphodiesterase activity increased from 1.8±0.1 to 20.2±2.0 μmol g−1 hr−1 along the same gradient. Acid phosphatase activity was highly correlated (R2=0.92, P<0.001) with the organic matter content of the sediment. A study of phosphatase kinetics showed that Vmax of all phosphatases also increased along the successional gradient. Trends in phosphatase activity and Vmax correlated positively with plant biomass and negatively with concentrations of soluble reactive phosphorus in porewater,
sediment extractable phosphorus, and total phosphourus. The porewater N∶P atom ratio decreased along the succession gradient
from 25.3 in an early stage, open water community to 13.0 in a community dominated by emergent vegetation. The data also show
that the distribution of the forms of phosphorus changed with successional stage. The change in distribution and the increased
biological demand for phosphorus that paralleled succession were mediated by the activity of phosphatase enzymes. 相似文献
19.
Slavica Matijević Natalia Bojanić Grozdan Kušpilić Živana Ninčević Gladan 《Environmental Earth Sciences》2009,59(4):853-866
Phosphorus (P) species concentrations in 0–2 cm surface sediment layer were investigated monthly from November 2001 to December
2002 at the bay, channel and open sea stations in the middle Adriatic. Modified SEDEX method was used for inorganic phosphorus
species determination [P in biogenic (P-FD), authigenic (P-AUT), detrital apatite (P-DET) and P adsorbed on to iron oxides
and hydroxides (P–Fe)], and organic phosphorus (P-ORG). P-FD, P-AUT and P-DET concentration ranges (1.5–5.4, 0–2.7 and 0.4–3.4 μmol g−1, respectively) were similar at all stations, and showed no obvious common trend of seasonal changes. P–Fe ranged from 1.9
to 11.9 μmol g−1 with the highest values at bay station and higher seasonal oscillations than other inorganic P forms. P-ORG ranged from 0.3
to 18.7 μmol g−1 with higher concentrations at stations of fine-sized sediments and showed increased concentrations in warm part of the year
at all stations. Correlation between concentrations of P–Fe in the surface sediment layer and orthophosphate sediment-water
interface concentration gradients at bay and channel stations indicated to P–Fe importance in the orthophosphate benthic flux.
For the bay station, linkage between sediment P-ORG and chlorophyll a concentrations, primary production and microzooplankton abundance was established, indicating a 1 month delay of sediment
response to production fluctuations in the water column. 相似文献
20.
A detailed study of arsenic cycling in the Huon estuary, south-east Tasmania, was undertaken October 1996–September 1998.
Arsenic species data were obtained during eight 3-monthly spatial surveys, and a time-series study at a single site in the
estuary over a 7-mo period. The data have been correlated with other chemical measurements, including nutrients, salinity,
and dissolved oxygen, and also with biological information about the microalgal species present. In the Huon estuary, arsenic
cycling is almost entirely biologically influenced. The seasonal cycle of reduced, methylated, and hydride refractory arsenic
species was similar to that found in other temperate estuaries of the Northern hemisphere, with greatest production occurring
during summer months. Inorganic arsenic concentrations in the Huon River were very low [As(V+III): 0.023–0.057 μg l−1], even when compared with other pristine systems. Concentrations at the seaward end of the estuary were typical of those
found in unpolluted coastal seawater. The behavior of As(V+III) in the estuary was nearly conservative in all surveys except
those conducted during summer (February), when significant depletion was observed at higher salinity. During these surveys,
up to 60% of inorganic arsenic was apparently depleted from the water column with only a small proportion (20–25%) recycled
as methylated and UV-labile arsenic species. This was particularly the case in a high salinity side-arm of the estuary, Port
Cygnet. The extent of inorganic arsenic depletion correlated with cell numbers of the phytoplanktonPseudo-nitzschia. The fate of the missing inorganic arsenic is unclear, but the co-existence ofPseudo-nitzschia blooms with commercial mussel leases in Port Cygnet could provide one explanation for the loss. 相似文献