共查询到20条相似文献,搜索用时 93 毫秒
1.
Dissolved inorganic nutrient elements were analyzed from the samples collected in the South Passage of the Changjiang (Yangtze River) Estuary in March 2003, including NH4 , NO3-, NO2- and PO43-. The water samples were collected with a Niskin sampler hourly at the near-surface, middle and near-bottom depths at the three stations -A1, A2 and A3-during two complete tidal cycles of neap tide and spring tide. Results showed that 1) the concentrations of NH4 , NO3- and NO2- were a little higher respectively during the neap tide than those during the spring tide, while PO43- showed an opposite trend, and each was higher in the ebb tide than in the flood tide, either for the neap tidal cycle or the spring tidal cycle; 2) higher stratification of the nutrients existed obviously in this area, with the concentrations of which increased from the bottom to the surface, especially for NH4 and NO3-; 3) the coefficient of variation (C.V.) values of all dissolved inorganic nutrients varied from 4.06% to 36.8% beyond different influences of the tidal current and Changjiang runoff; 4) with increasing suspended matter in the water column, the concentrations of PO43- became lower in the filtered water; and 5) the total transport of each tidal cycle was much more in the spring tide than in the neap tide, and the positive values indicated that the nutrients had been exported to the East China Sea. Studies on the variations and net transport of dissolved inorganic nutrients in the South Passage of the Changjiang Estuary will provide the scientific basis for the study of the mechanism of red tide in the East China Sea. 相似文献
2.
Modeling runoff and soil erosion in a catchment area, using the GIS, in the Himalayan region, India 总被引:1,自引:0,他引:1
Remote sensing data and GIS techniques have been used to compute runoff and soil erosion in the catchment area along the NH-1A between Udhampur and Kud covering an area of approximately 181 km2. Different thematic layers, for example lithology, a landuse and landcover map, geomorphology, a slope map, and a soil-texture map, were generated from these input data. By use of the US Soil Conservation Service curve number method, estimated runoff potential was classified into five levels—very low, low, moderate, high, and very high. Data integration was performed by use of the weighting rating technique, a conventional qualitative method, to give a runoff potential index value. The runoff potential index values were used to delineate the runoff potential zones, namely low, moderate, high, and very high. Annual spatial soil loss estimation was computed using the Morgan–Morgan–Finney mathematical model in conjunction with remote sensing data and GIS techniques. Greater soil erosion was found to occur in the northwestern part of the catchment area. When average soil loss from the catchment area was calculated it was found that a maximum average soil loss of more than 20 t ha−1 occurred in 31 km2 of the catchment area. 相似文献
3.
This paper estimates CO2 fluxes in a municipal site for final disposal of solid waste, located in Gualeguaychu, Argentina. Estimations were made using
the accumulation chamber methods, which had been calibrated previously in laboratory. CO2 fluxes ranged from 31 to 331 g m−2 day−1. Three different populations were identified: background soil gases averaging 46 g m−2 day−1, intermediate anomalous values averaging 110 g m−2 day−1 and high anomalous values averaging 270 g m−2 day−1. Gas samples to a depth of 20 cm were also taken. Gas fractions, XCO2 < 0.1, XCH4 < 0.01, XN2 ~0.71 and XO2 ~0.21, δ13C of CO2 (−34 to −18‰), as well as age of waste emplacement, suggest that the study site may be at the final stage of aerobic biodegradation.
In a first approach, and following the downstream direction of groundwater flow, alkalinity and δ13C of dissolved inorganic carbon (−15 to 4‰) were observed to increase when groundwater passed through the disposal site. This
suggests that the CO2 generated by waste biodegradation dissolves or that dissolved organic matter appears as a result of leachate degradation. 相似文献
4.
The changes in the water chemistry of rivers can reflect influence of anthropogenic activities on the water environment to
some extent. To understand the relationship between the spatial distribution of the eco-environment of the watershed and the
characteristics of water chemistry and geochemistry of rivers, firstly, the digital Wujiang watershed was built, and then
the sub-watersheds were delineated, taking the sample points as sub-watershed outlets based on GIS. Secondly, using the function
of spatial analyst of GIS, the statistical features of eco-environment (such as lithology and land use/cover) of each sub-watershed
were calculated according to their respective classification. Finally, the correlation between the spatial distribution of
lithology of the sub-watersheds and their corresponding 87Sr/86Sr ratio of river water, the correlation between NO3
−/HCO3
−, Cl−/HCO3
−, SO4
2−/HCO3
− and anthropogenic activities, respectively, and the correlation between the fraction of green vegetation of the sub-watershed
and their corresponding flux of TDS (total dissolved solids) were analyzed quantitatively. The results justify that the 87Sr/86Sr ratio of river water is highly dependent on the lithologic feature of the watershed and indicate that anthropogenic activities
are one of the main sources of NO3
− and SO4
2− of river waters. The output of TDS is highly dependent on the percentage of vegetation cover of the watershed. 相似文献
5.
Environmental geochemistry and quality assessment of mine water of Jharia coalfield,India 总被引:1,自引:0,他引:1
Abhay Kumar Singh M. K. Mahato B. Neogi B. K. Tewary A. Sinha 《Environmental Earth Sciences》2012,65(1):49-65
A long mining history and unscientific exploitation of Jharia coalfield caused many environmental problems including water
resource depletion and contamination. A geochemical study of mine water in the Jharia coalfield has been undertaken to assess
its quality and suitability for domestic, industrial and irrigation uses. For this purpose, 92 mine water samples collected
from different mining areas of Jharia coalfield were analysed for pH, electrical conductivity (EC), major cations (Ca2+, Mg2+, Na+, K+), anions (F−, Cl−, HCO3
−, SO4
2−, NO3
−), dissolved silica (H4SiO4) and trace metals. The pH of the analysed mine water samples varied from 6.2 to 8.6, indicating mildly acidic to alkaline
nature. Concentration of TDS varied from 437 to 1,593 mg L−1 and spatial differences in TDS values reflect the variation in lithology, surface activities and hydrological regime prevailing
in the region. SO4
2− and HCO3
− are dominant in the anion and Mg2+ and Ca2+ in the cation chemistry of mine water. High concentrations of SO4
2− in the mine water of the area are attributed to the oxidative weathering of pyrites. Ca–Mg–SO4 and Ca–Mg–HCO3 are the dominant hydrochemical facies. The drinking water quality assessment indicates that number of mine water samples
have high TDS, total hardness and SO4
2− concentrations and needs treatment before its utilization. Concentrations of some trace metals (Fe, Mn, Ni, Pb) were also
found to be above the desirable levels recommended for drinking water. The mine water is good to permissible quality and suitable
for irrigation in most cases. However, higher salinity, residual sodium carbonate and Mg-ratio restrict its suitability for
irrigation at some sites. 相似文献
6.
Water samples collected from dug wells and tube wells from the Kurunegala District of Sri Lanka have been studied for their
major hydrogeochemical parameters to understand the chemical quality of water in the terrain. The region is composed of Precambrian
metamorphic rocks where groundwater is only available in the regolith and along weak structural discontinuities. The study
of the major chemical constituents of groundwater revealed several relationships with the aquifer lithology. Groundwater from
mafic rocks have high dissolved solids, while quartzose metaclastic rocks yield water with low dissolved solids. The study
area displays very low SO4
2− contents of the groundwater. The chloride content is higher in the dry regions and in terrains underlain by pink granite
and marble/calc gneiss while areas with marble, as expected, show high concentrations of Ca and Mg ions. The waters in the
region can be classified into non-dominant cations to Na + K dominant and Cl− and HCO3
− dominant types. Water from charnockite-bearing areas tends to have non-dominant cations and more CO3
2− + HCO3
− types. Effects such as soluble salts in the regolith, fracture intensity and climatic variations play a significant role
in the behavior of the hydrogeochemistry in the area. 相似文献
7.
Chemical and Strontium Isotopic Compositions of the Hanjiang Basin Rivers in China: Anthropogenic Impacts and Chemical Weathering 总被引:1,自引:0,他引:1
The Hanjiang River, the largest tributaries of the Changjiang (Yangtze) River, is the water source area of the Middle Route
of China’s South-to-North Water Transfer Project. The chemical and strontium isotopic compositions of the river waters are
determined with the main purpose of understanding the contribution of chemical weathering processes and anthropogenic inputs
on river solutes, as well as the associated CO2 consumption in the carbonate-dominated basin. The major ion compositions of the Hanjiang River waters are characterized by
the dominance of Ca2+ and HCO3
−, followed by Mg2+ and SO4
2−. The increase in TDS and major anions (Cl−, NO3
−, and SO4
2−) concentrations from upstream to downstream is ascribed to both extensive influences from agriculture and domestic activities
over the Hanjiang basin. The chemical and Sr isotopic analyses indicate that three major weathering sources (dolomite, limestone,
and silicates) contribute to the total dissolved loads. The contributions of the different end-members to the dissolved load
are calculated with the mass balance approach. The calculated results show that the dissolved load is dominated by carbonates
weathering, the contribution of which accounts for about 79.4% for the Hanjiang River. The silicate weathering and anthropogenic
contributions are approximately 12.3 and 6.87%, respectively. The total TDS fluxes from chemical weathering calculated for
the water source area (the upper Hanjiang basin) and the whole Hanjiang basin are approximately 3.8 × 106 and 6.1 × 106 ton/year, respectively. The total chemical weathering (carbonate and silicate) rate for the Hanjiang basin is approximately
38.5 ton/km2/year or 18.6 mm/k year, which is higher than global mean values. The fluxes of CO2 consumption by carbonate and silicate weathering are estimated to be 56.4 × 109 and 12.9 × 109 mol/year, respectively. 相似文献
8.
Hydrochemical characteristics and quality assessment of shallow groundwater in a coastal area of Southwest Bangladesh 总被引:4,自引:3,他引:1
In this study, the hydrochemical characteristics of shallow groundwater in a coastal region (Khulna) of southwest Bangladesh
have been evaluated based on different indices for drinking and irrigation uses. Water samples were collected from 26 boreholes
and analyzed for major cations and anions. Other physico-chemical parameters like pH, electrical conductivity (EC), and total
dissolved solids were also measured. Most groundwater is slightly alkaline and largely varies in chemical composition, e.g.
EC ranges from 962 to 9,370 μs/cm. The abundance of the major ions is as follows: Na+ > Ca2+ > Mg2+ > K+ = Cl− > HCO3
− > SO4
2− > NO3
−. Interpretation of analytical data shows two major hydrochemical facies (Na+–K+–Cl−–SO4
2− and Na+–K+–HCO3
−) in the study area. Salinity, total hardness, and sodium percentage (Na%) indicate that most of the groundwater samples are
not suitable for irrigation as well as for domestic purposes and far from drinking water standard. Results suggest that the
brackish nature in most of the groundwaters is due to the seawater influence and hydrogeochemical processes. 相似文献
9.
Behzad Mortazavi Ashley A. Riggs Jane M. Caffrey Hélène Genet Scott W. Phipps 《Estuaries and Coasts》2012,35(3):862-877
Benthic oxygen, dinitrogen, and nutrient fluxes (NH4+, NO3−, and PO43−) were measured monthly during a 1-year period at two locations in Weeks Bay, a shallow (1.4 m) and eutrophic estuary in Alabama.
Gross primary productivity (GPP), ecosystem respiration (R), and net ecosystem metabolism were determined from high-frequency
dissolved oxygen measurements. Peak water column NO3− (55 μM) and chlorophyll a (138 μg/l) concentrations were measured during spring and fall, respectively. Sediments were a net source of NH4+ (102 μmol m−2 h−1) and PO43− (0.9 μmol m−2 h−1) but a sink for NO3− (−30 μmol m−2 h−1). Benthic N2 fluxes indicated net N fixation (12 μmol N m−2 h−1). Sediment oxygen demand (0.55 g O2 m−2 day−1) accounted for <10% of R (7.3 g O2 m−2 day−1). Despite high GPP rates (4.7 g O2 m−2 day−1), the estuary was net heterotrophic. Benthic regeneration supplied, on average, 7.5% and 4% of primary productivity N and
P demands, respectively. These results contrast with the conventional view that benthic regeneration accounts for a large
fraction of phytoplankton nutrient demand in shallow estuaries. 相似文献
10.
Jenifer E. Dugan David M. Hubbard Henry M. Page Joshua P. Schimel 《Estuaries and Coasts》2011,34(4):839-850
We investigated the role of sandy beaches in nearshore nutrient cycling by quantifying macrophyte wrack inputs and examining
relationships between wrack accumulation and pore water nutrients during the summer dry season. Macrophyte inputs, primarily
giant kelp Macrocystis pyrifera, exceeded 2.3 kg m−1 day−1. Mean wrack biomass varied 100-fold among beaches (range = 0.41 to 46.43 kg m−1). Mean concentrations of dissolved inorganic nitrogen (DIN), primarily NOx−-N, and dissolved organic nitrogen (DON) in intertidal pore water varied significantly among beaches (ranges = 1 to 6,553 μM
and 7 to 2,006 μM, respectively). Intertidal DIN and DON concentrations were significantly correlated with wrack biomass.
Surf zone concentrations of DIN were also strongly correlated with wrack biomass and with intertidal DIN, suggesting export
of nutrients from re-mineralized wrack. Our results suggest beach ecosystems can process and re-mineralize substantial organic
inputs and accumulate dissolved nutrients, which are subsequently available to nearshore waters and primary producers. 相似文献
11.
Hydrochemical characteristics of groundwater in the Zhangye Basin, Northwestern China 总被引:3,自引:0,他引:3
The Zhangye Basin, located in arid northwest China, is an important agricultural and industrial center. In recent years rapid
development has created an increased demand for water, which is increasingly being fulfilled by groundwater abstraction. Detailed
knowledge of the geochemical evolution of groundwater and water quality can enhance understanding of the hydrochemical system,
promoting sustainable development and effective management of groundwater resources. To this end, a hydrochemical investigation
was conducted in the Zhangye Basin. Types of shallow groundwater in the Zhangye Basin were found to be HCO3
−, HCO3
−–SO4
2−, SO4
2−–HCO3
−, SO4
2−–Cl−, Cl−–SO4
2− and Cl− . The deep aquifer groundwater type was found to be HCO3−–SO42− throughout the entire area. Ionic ratio and saturation index calculations suggest that silicate rock weathering and evaporation
deposition are the main processes that determine the ionic composition in the study area. The suitability of the groundwater
for irrigation was assessed based on the US Salinity Laboratory salinity classification and the Wilcox diagram. In the study
area, the compositions of the stable isotopes δ18O and δD in groundwater samples were found to range from −4.00 to −9.28‰ and from −34.0 to −65.0‰, respectively. These values
indicate that precipitation is the main recharge source for the groundwater system; some local values indicate high levels
of evaporation. Tritium analysis was used to estimate the ages of the different groundwaters; the tritium values of the groundwater
samples varied from 3.13 to 36.62 TU. The age of the groundwater at depths of less than 30 m is about 5–10 years. The age
of the groundwater at depths of 30–50 m is about 10–23 years. The age of the groundwater at depths of 50–100 m is about 12–29 years.
For groundwater samples at depths of greater than 100 m, the renewal time is about 40 years. 相似文献
12.
Microelectrode Study of Oxygen Uptake and Organic Matter Decomposition in The Sediments of Xiamen Western Bay 总被引:2,自引:0,他引:2
Sediment cores were sampled from Xiamen Western Bay at five sites during the summer and winter of 2006 and Hg–Au microelectrodes
were used to make on board measurements of the concentration gradients of dissolved oxygen, Mn2+, and Fe2+ within the sediments. The O2 concentrations decreased sharply from about 200 μmol L−1 in the bottom seawater to zero within a depth of a few millimeters into the sediment. Dissolved Mn2+ was detected below the oxic zones with peak concentrations up to 600 μmol L−1, whereas dissolved Fe2+ had peak concentrations up to 1,000 μmol L−1 in deeper layers. The elemental contents of organic carbon and nitrogen within the sediments were analyzed and their C/N
ratios were in the range of 9.0 to 10.1, indicative of heavy terrestrial origin. Sediments from two sites near municipal wastewater
discharge outlets had higher organic contents than those from the other sites. These high organic contents corresponded to
shallow O2 penetration depths, high dissolved Mn2+ and Fe2+ concentrations, and negative redox potentials within the sediments. This indicated that the high organic matter content had
promoted microbial respiration within the sediments. Overall, the organic content did not show any appreciable decrease with
increasing sediment depths, so a quadratic polynomial function was used to fit the curve of O2 profiles within the sediments. Based on the O2 profiles, O2 fluxes across the seawater and sediment interface were estimated to be in the range 6.07 to 14.9 mmol m−2 day−1, and organic carbon consumption rates within the surface sediments were estimated to be in the range 3.3 to 20.8 mgC cm−3 a−1. The case demonstrated that biogeochemistry within the sediments of the bay was very sensitive to human activities such as
sewage discharge. 相似文献
13.
Lars Chresten Lund-Hansen Thorbjørn Joest Andersen Morten Holtegaard Nielsen Morten Pejrup 《Estuaries and Coasts》2010,33(6):1442-1451
Optical constituents as suspended particulate matter (SPM), chlorophyll (Chl-a), colored dissolved organic matter (CDOM),
and grain sizes were obtained on a transect in the arctic fjord-type estuary Kangerlussuaq (66°) in August 2007 along with
optical properties. These comprised diffuse attenuation coefficient of downwelling PAR (K
d(PAR)), upwelling PAR (K
u(PAR)), particle beam attenuation coefficient (c
p), and irradiance reflectance R(−0, PAR). PAR is white light between 400 and 700 nm. The estuary receives melt water from the Greenland Inland Ice and stations
covered a transect from the very high turbid melt water outlet to clear marine waters. Results showed a strong spatial variation
with high values as for suspended matter concentrations, CDOM, diffuse attenuation coefficient K
d(PAR), particle beam attenuation coefficients (c
p), and reflectance R(−0, PAR) at the melt water outlet. Values of optical constituents and properties decreased with distance from the melt water
outlet to a more or less constant level in central and outer part of the estuary. There was a strong correlation between inorganic
suspended matter (SPMI) and diffuse attenuation coefficient K
d(PAR) (r
2 = 0.92) and also for particle beam attenuation coefficient (c
p; r
2 = 0.93). The obtained SPMI specific attenuation—K
d*(PAR) = 0.13 m2 g−1 SPMI—and the SPMI specific particle beam attenuation—c
p* = 0.72 m2 g−1—coefficients were about two times higher than average literature values. Irradiance reflectance R(−0, PAR) was comparatively high (0.09−0.20) and showed a high (r
2 = 0.80) correlation with K
u(PAR). Scattering dominated relative to absorption—b(PAR)/a(PAR) = 12.3. Results strongly indicated that the high values in
the optical properties were related to the very fine particle sizes (mean = 2–6 μm) of the suspended sediment. Data and results
are discussed and compared to similar studies from both temperate and tropical estuaries. 相似文献
14.
Questions concerning the influence of soil type and crop cover on the fate and transport of nitrate (NO3−) were examined. During a growing season, soils derived from glacial material underlying either corn or soybeans were sampled
for levels of NO3− within the pore water. Measured levels of NO3− ranged from below detection limit to 14.9 g NO3− per kilogram of soil (g/kg). In fields with the same crop cover, the silty-clayey soil exhibited a greater decrease in NO3− levels with depth than the sandier soil. Crop uptake of NO3− occurs within the root zone; however, the type of crop cover did not have a direct impact on the fate or transport during
the growing season. The soils underlying soybeans had an increase in NO3− levels following harvest, suggesting that the decomposition of the soybean roots contributed to the net gain of NO3− in the shallow soil. For all of the soil types, conditions below 100 cm are conducive for microbial denitrification, with
both a high water saturation level (>60%) and moderate organic carbon content (1–2%). At depths below 100 cm, temporal differences
in NO3− levels of over a magnitude, up to a 95% reduction, were recorded in the soil units as the growing season progressed. Physical
properties that control the transport of NO3− or denitrification have a larger influence on NO3− levels than crop type.
相似文献
Eric W. PetersonEmail: |
15.
Groundwater nitrate contamination and risk assessment in an agricultural area,South Korea 总被引:2,自引:1,他引:1
Jae-Yeol Cheong Se-Yeong Hamm Jeong-Hwan Lee Kwang-Sik Lee Nam-Chil Woo 《Environmental Earth Sciences》2012,66(4):1127-1136
The nitrate of groundwater in the Gimpo agricultural area, South Korea, was characterized by means of nitrate concentration,
nitrogen-isotope analysis, and the risk assessment of nitrogen. The groundwaters belonging to Ca–(Cl + NO3) and Na–(Cl + NO3) types displayed a higher average NO3
− concentration (79.4 mg/L), exceeding the Korean drinking water standard (<44.3 mg/L NO3
−). The relationship between δ18O–NO3
− values and δ15N–NO3
− values revealed that nearly all groundwater samples with δ15N–NO3
− of +7.57 to +13.5‰ were affected by nitrate from manure/sewage as well as microbial nitrification and negligible denitrification.
The risk assessment of nitrate for groundwater in the study area was carried out using the risk-based corrective action model
since it was recognized that there is a necessity of a quantitative assessment of health hazard, as well as a simple estimation
of nitrate concentration. All the groundwaters of higher nitrate concentration than the Korean drinking water standard (<44.3 mg/L NO3
−) belonged to the domain of the hazard index <1, indicating no health hazard by nitrate in groundwater in the study area.
Further, the human exposure to the nitrate-contaminated soil was below the critical limit of non-carcinogenic risk. 相似文献
16.
Stable Carbon Isotope Biogeochemistry and Anthropogenic Impacts on Karst Ground Water, Zunyi, Southwest China 总被引:2,自引:0,他引:2
Si-Liang Li Cong-Qiang Liu Yun-Chao Lang Faxiang Tao Zhiqi Zhao Zhihua Zhou 《Aquatic Geochemistry》2008,14(3):211-221
Natural and anthropogenic impacts on karst ground water, Zunyi, Southwest China, are discussed using the stable isotope composition
of dissolved inorganic carbon and particulate organic carbon, together with carbon species contents and water chemistry. The
waters can be mainly characterized as HCO3–Ca type, HCO3 · SO4–Ca type, or HCO3 · SO4–Ca · Mg type, according to mass balance considerations. It is found that the average δ13CDIC values of ground waters are higher in winter (low-flow season) than in summer (high-flow season). Lower contents of dissolved
inorganic carbon (DIC) and lower values of δ13CDIC in summer than in winter, indicate that local rain events in summer and a longer residence time of water in winter play an
important role in the evolution of ground water carbon in karst flow systems; therefore, soil CO2 makes a larger contribution to the DIC in summer than in winter. The range of δ13CDIC values indicate that dissolved inorganic carbon is mainly controlled by the rate of carbonate dissolution. The concentrations
of dissolved organic carbon and particulate organic carbon in most ground water samples are lower than 2.0 mg C L−1 and 0.5 mg C L−1, respectively, but some waters have slightly higher contents of organic carbon. The waters with high organic carbon contents
are generally located in the urban area where lower δ13CDIC values suggest that urbanization has had an effect on the ground water biogeochemistry and might threaten the water quality. 相似文献
17.
Derrick Y. F. Lai 《Environmental Geology》2009,58(6):1197-1206
Peatlands are a large potential source of methane (CH4) to the atmosphere. In order to investigate the effects of climate change on CH4 emission from northern ombrotrophic peatlands, a simulation model coupling water table dynamics with methane emission was
developed for the Mer Bleue Bog in Ontario, Canada. The model was validated against reported values of CH4 flux from field measurements and the model outputs exhibited high sensitivity to acrotelm thickness, leaf area index, transmissivity
and slope of water table. With a 2–4°C temperature rise over the 4-year simulation period, the rate of CH4 release dropped significantly to under 0.1 mg m−2 day−1. On the other hand, mean CH4 emission increased by >26-fold when the increase in precipitation was >15%. When looking at the combined effects, the highest
CH4 release (13.3 mg m−2 day−1) was attained under the scenario of 2°C temperature rise and 25% precipitation increase. Results obtained in this study highlight
the importance of avoiding more extreme climate change, which would otherwise lead to enhanced methane release from peatlands
and further atmospheric warming through positive feedback. 相似文献
18.
The effect of the source water quality on As(V) removal by coagulation/microfiltration (C/MF) was investigated systematically
using a jar test and a lab-scale test; the results of the lab-scale test coincide with those of the jar test. It showed that
the increase of dissolved organic carbon (DOC), HPO4
2− and HCO3
− concentrations would moderately decrease As(V) removal, and the residual As(V) concentration in treated water is no more
than 10 μg L−1 when the concentration of DOC, HPO4
2− and HCO3
− in raw water is not beyond 9.22 mg L−1, 1.6 mg L−1 and 300 mg L−1, respectively. Other co-ions, such as Cl−, NO3
−, F−, SO4
2−, and counter-ions including K+, Ca2+ and Mg2+, have little effect on As(V) removal. Both results of the jar test and the lab-scale test demonstrate that Fe3+ dose of 6 mg L−1 is enough to eliminate the influence of HCO3
− whose concentration changes from 350 mg L−1 to 450 mg L−1. In the lab-scale test, As(V) removal ranged from 92.8 to 98.2% at Fe3+ dose of 4 mg L−1 and 5 mg L−1 when As(V) concentration in raw water was about 100 μg L−1. The results obtained in this study suggest that As(V) removal by C/MF process is sensitive to the quality of raw water,
and a jar test needs to be done before C/MF process is used for arsenic removal from drinking water. 相似文献
19.
Morgane Lejart Jacques Clavier Laurent Chauvaud Christian Hily 《Estuaries and Coasts》2012,35(2):622-632
Respiration and calcification rates of the Pacific oyster Crassostrea gigas were measured in a laboratory experiment in the air and underwater, accounting for seasonal variations and individual size,
to estimate the effects of this exotic species on annual carbon budgets in the Bay of Brest, France. Respiration and calcification
rates changed significantly with season and size. Mean underwater respiration rates, deducted from changes in dissolved inorganic
carbon (DIC), were 11.4 μmol DIC g−1 ash-free dry weight (AFDW) h−1 (standard deviation (SD), 4.6) and 32.3 μmol DIC g−1 AFDW h−1 (SD 4.1) for adults (80–110 mm shell length) and juveniles (30–60 mm), respectively. The mean daily contribution of C. gigas underwater respiration (with 14 h per day of immersion on average) to DIC averaged over the Bay of Brest population was 7.0 mmol DIC m−2 day−1 (SD 8.1). Mean aerial CO2 respiration rate, estimated using an infrared gas analyzer, was 0.7 μmol CO2 g−1 AFDW h−1 (SD 0.1) for adults and 1.1 μmol CO2 g−1 AFDW h−1 (SD 0.2) for juveniles, corresponding to a mean daily contribution of 0.4 mmol CO2 m−2 day−1 (SD 0.50) averaged over the Bay of Brest population (with 10 h per day of emersion on average). Mean CaCO3 uptake rates for adults and juveniles were 4.5 μmol CaCO3 g−1 AFDW h−1 (SD 1.7) and 46.9 μmol CaCO3 g−1 AFDW h−1 (SD 29.2), respectively. The mean daily contribution of net calcification in the Bay of Brest C. gigas population to CO2 fluxes during immersion was estimated to be 2.5 mmol CO2 m−2 day−1 (SD 2.9). Total carbon release by this C. gigas population was 39 g C m−2 year−1 and reached 334 g C m−2 year−1 for densely colonized areas with relative contributions by underwater respiration, net calcification, and aerial respiration
of 71%, 25%, and 4%, respectively. These observations emphasize the substantial influence of this invasive species on the
carbon cycle, including biogenic carbonate production, in coastal ecosystems. 相似文献
20.
M. G. García K. L. Lecomte Y. Stupar S. M. Formica M. Barrionuevo M. Vesco R. Gallará R. Ponce 《Environmental Earth Sciences》2012,65(2):535-545
Symptoms of dental fluorosis have been observed in rural communities located in the Sierras Pampeanas de Córdoba, a mountainous
area in Central Argentina. The clinical assessment was performed in the Charbonier Department, where the fluoride (F−) intake was determined to be 3.90 ± 0.20 mg day−1 (n = 16). In this community, mild and severe fluorosis reach an incidence of 86.7% (total teeth surface = 636 teeth) among the
children population. To determine the origin and distribution of fluorine in natural waters from the Charbonier Department
and nearby regions, sampling was performed in the area covering the San Marcos River basin. The obtained results show that
F− concentrations vary between ~1 to ~2.5 mg l−1, with an outlier value of 8 mg l−1. The spatial distribution of F− shows that the lowest concentrations are found at the basin’s catchments. Maximum values are located in two sectors of the
basin: the Charbonier depression in the eastern part and at the San Marcos village, downstream the main collector, in the
western part of the basin. In these two regions, the F− contents in ground- and surface waters are >2.0 mg l−1 and nearly constant. Dissolved F− in natural waters from the study area has its origin in the weathering of F-bearing minerals present in the region’s dominant
lithology. The extent of mineral weathering is mostly determined by the residence time of water within the aquatic reservoir.
Longer residence times and a major solid–water interaction lead to enhanced release of F−. This explains the higher F− concentrations found in basin areas with lower run off. The removal of F− from water appears to occur by neither fluorite precipitation, nor by adsorption. Hence, variations in F− concentrations seem to be more related to regional hydrological conditions. 相似文献