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1.
Yongsik Sin Bonggil Hyun Quang-Dung Bach Sungryull Yang Chul Park 《Estuaries and Coasts》2012,35(3):839-852
Temporal and spatial variations in phytoplankton in Asan Bay, a temperate estuary under the influence of monsoon, were investigated
over an annual cycle (2004). Phytoplankton blooms started in February (>20 μg chl l−1) and continued until April (>13 μg chl l−1) during the dry season, especially in upstream regions. The percentage contribution of large phytoplankton (micro-sized)
was high (78–95%) during the blooms, and diatoms such as Skeletonema costatum and Thalassiosira spp. were dominant. The precipitation and freshwater discharge from embankments peaked and supplied nutrients into the bay
during the monsoon event, especially in July. Species that favor freshwater, such as Oscillatoria spp. (cyanobacteria), dominated during the monsoon period. The phytoplankton biomass was minimal in this season despite nutrient
concentrations that were relatively sufficient (enriched), and this pattern differed from that in tropical estuaries affected
by monsoon and in temperate estuaries where phytoplankton respond to nutrient inputs during wet seasons. The flushing time
estimated from the salinity was shorter than the doubling time in Asan Bay, which suggests that exports of phytoplankton maximized
by high discharge directly from embankments differentiate this bay from other estuaries in temperate and tropical regions.
This implies that the change in physical properties, especially in the freshwater discharge rates, has mainly been a regulator
of phytoplankton dynamics since the construction of embankments in Asan Bay. 相似文献
2.
Soil salinity and sodicity are environmental problems in the shrimp farming areas of the Cai Nuoc district, Ca Mau province,
Vietnam. In 2000, farmers in the district switched en masse from rice cropping to shrimp culture. Due to recent failure in
shrimp farming, many farmers wish to revert to a rotational system with rice in the wet season and shrimps in the dry season.
So far, all their attempts to grow rice have failed. To assess soil salinity and sodicity, 25 boreholes in shrimp ponds were
analysed in four consecutive seasons from 2002 to 2004. The results showed that soil salinity was quite serious (mean ECe 29.25 dS m−1), particularly in the dry season (mean ECe 33.44 dS m−1). In the wet season, significant amounts of salts still remained in the soil (mean ECe 24.65 dS m−1) and the highest soil salinity levels were found near the sea. Soil sodicity is also a problem in the district (exchangeable
sodium percentage range 9.63–72.07%). Sodicity is mainly a phenomenon of topsoils and of soils near the sea. Both soil salinity
and sodicity are regulated by seasonal rainfall patterns. They could together result in disastrous soil degradation in the
Cai Nuoc district. 相似文献
3.
Understanding of the role of oceanic input in nutrient loadings is important for understanding nutrient and phytoplankton
dynamics in estuaries adjacent to coastal upwelling regions as well as determining the natural background conditions. We examined
the nitrogen sources to Yaquina Estuary (Oregon, USA) as well as the relationships between physical forcing and gross oceanic
input of nutrients and phytoplankton. The ocean is the dominant source of dissolved inorganic nitrogen (DIN) and phosphate
to the lower portion of Yaquina Bay during the dry season (May through October). During this time interval, high levels of
dissolved inorganic nitrogen (primarily in the form of nitrate) and phosphate entering the estuary lag upwelling favorable
winds by 2 days. The nitrate and phosphate levels entering the bay associated with coastal upwelling are correlated with the
wind stress integrated over times scales of 4–6 days. In addition, there is a significant import of chlorophyll a to the bay from the coastal ocean region, particularly during July and August. Variations in flood-tide chlorophyll a lag upwelling favorable winds by 6 days, suggesting that it takes this amount of time for phytoplankton to utilize the recently
upwelled nitrogen and be transported across the shelf into the estuary. Variations in water properties determined by ocean
conditions propagate approximately 11–13 km into the estuary. Comparison of nitrogen sources to Yaquina Bay shows that the
ocean is the dominant source during the dry season (May to October) and the river is the dominant source during the wet season
with watershed nitrogen inputs primarily associated with nitrogen fixation on forest lands. 相似文献
4.
Using differential SAR interferometry to map land subsidence: a case study in the Pingtung Plain of SW Taiwan 总被引:3,自引:2,他引:1
Hsieh Chia-Sheng Shih Tian-Yuan Hu Jyr-Ching Tung Hsin Huang Mong-Han Angelier Jacques 《Natural Hazards》2011,58(3):1311-1332
Synthetic aperture radar (SAR) interferometry (InSAR) is a geodetic tool widely applied in the studies of earth-surface deformation.
This technique has the benefits of high spatial resolution and centimetre-scale accuracy. Differential SAR interferometry
(DInSAR) is used to measure ground deformation with repeat-pass SAR images. This study applied DInSAR and persistent scatterers
InSAR (PSInSAR) for detecting land subsidence in the Pingtung Plain, southern Taiwan, between 1995 and 2000. In recent years,
serious land subsidence occurred along coastal regions of Taiwan as a consequence of over-pumping of underground water. Results
of this study revealed that the critical subsidence region is located on the coast near the estuary of Linpien River. It is
also found that subsidence was significantly higher during the dry season than the wet season. The maximum annual subsidence
rate of the dry season is up to −11.51 cm/year in critical subsidence region and the vertical land movement rate is much slower
during the wet season. The average subsidence rates in wet and dry seasons are −0.31 and −3.37 cm/year, respectively. As a
result, the subsidence rate in dry seasons is about 3 cm larger than in wet seasons. 相似文献
5.
Temporal variation in rainfall created a germination window for seedling establishment in the upper intertidal marshes of southern California. In this highly variable climate, total annual rainfall was highly variable, as was the timing and size of rainfall during the wet season. Daily rainfalls>3.0 cm were rare in the long-term record but created germination opportunities that had two components: low salinity and high moisture. During the 1996–1997 wet season, only one-day rainfalls>3.0 cm resulted in large increases in soil moisture and decreases in soil salinity. Germination in the upper intertidal marsh of three wetlands followed two large (>3.0 cm) rainfall events in the relatively dry 1996–1997 season and multiple medium and small rainfall events in the wetter 1997–1998 season. In addition to rainfall, plant cover and soil texture influenced, spatial and temporal variation in soil salinity and moisture. Daily and weekly sampling adequately described soil moisture and salinity so that germination could be predicted; monthly sampling would have missed the low-salinity and high-moisture events that trigger germination. 相似文献
6.
The hydroelectric reservoir of Petit Saut, French Guiana, was created in 1994–1995 by flooding 350 km2 of tropical forest. When sampled in 1999, the lake exhibited a permanent stratification separating the 3–5 m thick, oxygenated
epilimnion from the anoxic hypolimnion. The rate of anaerobic organic carbon mineralization below the oxycline was on the
order of 1 μmol C m−2 s−1 and did not show a pronounced difference between wet and dry seasons. Methanogenesis accounted for 76–83% of anaerobic carbon
mineralization, with lesser contributions of sulfate reduction and dissimilatory iron reduction. Upward mixing of reduced
inorganic solutes explained 90% of the water column O
2 demand during the dry season, while most O
2 consumption during the wet season was coupled to aerobic respiration of organic matter synthesized in the surface waters.
Inorganic mercury species represented 10–40% of total dissolved mercury in the epilimnion, but were of relatively minor importance
(≤10%) in the anoxic portion of the water column. Net production of soluble organic mercury compounds in the flooded soils
and anoxic water column did not vary significantly between wet and dry seasons. Methylmercury accounted for about 15% of total
dissolved mercury below the oxycline. Its estimated net production rate, 0.04 mg m−2 yr−1, is of the same order of magnitude as values reported for contaminated lakes and flooded terrestrial ecosystems. 相似文献
7.
Oxygen and hydrogen isotopes for the characteristics of groundwater recharge: a case study from the Chih-Pen Creek basin,Taiwan 总被引:5,自引:2,他引:3
Assessing the seasonal variation of groundwater recharge is important for effective management of groundwater resources. Stable
isotopes of oxygen and hydrogen were used to estimate the sources of groundwater and seasonal contributions of precipitation
to groundwater recharge in Chih-Pen Creek basin of eastern Taiwan. Based on the isotopes of precipitation (n = 177), two different local meteoric water regression lines (LMWL) can be obtained for the different seasons: δD = 8.0618O + 10.08 for wet season precipitation (May through October) and δD = 8.65δ18O + 17.09 for dry season precipitation (November through April). The slope and intercept of regression line for wet season
precipitation are virtually identical to the global meteoric water line (GMWL) of Craig (1961). In contrast to during dry season precipitation due to evaporation effect the intercept of 17.09 is much higher than of
the GMWL of 10. The results show the stable isotopes compositions of precipitation decrease with increasing rainfall amount
and air temperature, due to the amount effect of precipitation is pronounced. The amount effect is clearly but do not show
the temperature effect from January to December 2007. Using a mass-balance equation, a comparison of deuterium excess or d values of precipitation and groundwater indicates the groundwater consist of 76% wet season precipitation and 24% dry season
precipitation, representing a distinct seasonal variation of groundwater recharge in study area. About 79% of the groundwater
is recharged from the river water of the mountain watershed and 21% is from the rain that falls on the basin. 相似文献
8.
John C. Ayers Gregory George David Fry Laura Benneyworth Carol Wilson Leslie Auerbach Kushal Roy Md. Rezaul Karim Farjana Akter Steven Goodbred 《Geochemical transactions》2017,18(1):4
To identify the causes of salinization and arsenic contamination of surface water on an embanked island (i.e., polder) in the tidal delta plain of SW Bangladesh we collected and analyzed water samples in the dry (May) and wet (October) seasons in 2012–2013. Samples were collected from rice paddies (wet season), saltwater ponds used for brine shrimp aquaculture (dry season), freshwater ponds and tidal channels (both wet and dry season), and rainwater collectors. Continuous measurements of salinity from March 2012 to February 2013 show that tidal channel water increases from ~0.15 ppt in the wet season up to ~20 ppt in the dry season. On the polder, surface water exceeds the World Health Organization drinking water guideline of 10 μg As/L in 78% of shrimp ponds and 27% of rice paddies, raising concerns that produced shrimp and rice could have unsafe levels of As. Drinking water sources also often have unsafe As levels, with 83% of tubewell and 43% of freshwater pond samples having >10 μg As/L. Water compositions and field observations are consistent with shrimp pond water being sourced from tidal channels during the dry season, rather than the locally saline groundwater from tubewells. Irrigation water for rice paddies is also obtained from the tidal channels, but during the wet season when surface waters are fresh. Salts become concentrated in irrigation water through evaporation, with average salinity increasing from 0.43 ppt in the tidal channel source to 0.91 ppt in the rice paddies. Our observations suggest that the practice of seasonally alternating rice and shrimp farming in a field has a negligible effect on rice paddy water salinity. Also, shrimp ponds do not significantly affect the salinity of adjacent surface water bodies or subjacent groundwater because impermeable shallow surface deposits of silt and clay mostly isolate surface water bodies from each other and from the shallow groundwater aquifer. Bivariate plots of conservative element concentrations show that all surface water types lie on mixing lines between dry season tidal channel water and rainwater, i.e., all are related by varying degrees of salinization. High As concentrations in dry season tidal channel water and shrimp ponds likely result from groundwater exfiltration and upstream irrigation in the dry season. Arsenic is transferred from tidal channels to rice paddies through irrigation. Including groundwater samples from the same area (Ayers et al. in Geochem Trans 17:1–22, 2016), principal components analysis and correlation analysis reveal that salinization explains most variation in surface water compositions, whereas progressive reduction of buried surface water by dissolved organic carbon is responsible for the nonconservative behavior of S, Fe, and As and changes in Eh and alkalinity of groundwater. 相似文献
9.
This paper addresses temporal variability in bottom hypoxia in broad shallow areas of Mobile Bay, Alabama. Time-series data
collected in the summer of 2004 from one station (mean depth of 4 m) exhibit bottom dissolved oxygen (DO) variations associated
with various time scales of hours to days. Despite a large velocity shear, stratification was strong enough to suppress vertical
mixing most of the time. Bottom DO was closely related to the vertical salinity gradient (ΔS). Hypoxia seldom occurred when
ΔS (over 2.5 m) was <2 psu and occurred almost all the time when ΔS was >8 psu in the absence of extreme events like hurricanes.
Oxygen balance between vertical mixing and total oxygen demand was considered for bottom water from which oxygen demand and
diffusive oxygen flux were estimated. The estimated decay rates at 20°C ranging between 0.175–0.322 d−1 and the corresponding oxygen consumption as large as 7.4 g O2 m−2 d−1 fall at the upper limit of previously reported ranges. The diffusive oxygen flux and the corresponding vertical diffusivity
estimated for well mixed conditions range between 8.6–9.5 g O2 m−2 d−1 and 2.6–2.9 m2 d−1, respectively. Mobile Bay hypoxia is likely to be associated with a large oxygen demand, supported by both water column and
sediment oxygen demands, so that oxygen supply from surface water during destratification events would be quickly exhausted
to return to hypoxic conditions within a few hours to days after destratification events are terminated. 相似文献
10.
Marin F. D. Greenwood 《Estuaries and Coasts》2007,30(3):537-542
Organisms tend to inhabit predictable portions of estuaries along salinity gradients between the ocean inlets (salinity >
35 psu) and the freshwater tributaries (salinity = 0). Previous studies have suggested that the continuous change in biological
community structure along this gradient is relatively rapid at certain salinities. This is the basis for estuarine salinity
zonation schemes similar to the classic Venice System (i.e., 0–0.5, 0.5–5, 5–18, 18–30, 30–40, > 40). An extensive database
(n > 16,000 samples) of frequency of occurrence of nekton was used to assess evidence for estuarine salinity zones in two
southwest Florida estuaries: Tampa Bay and Charlotte Harbor. Rapid change in nekton community structure occurred at each end
of the estuarine salinity gradient, with comparatively slow (but steady) change in between. There was little strong evidence
for estuarine salinity zones at anything other than low salinities (0.1–1). As previously suggested by other authors, estuaries
may be regarded as ecoclines, because they form areas of relatively slow but progressive ecological change. The ends of the
estuarine salinity gradient appear to be ecotones (areas of rapid change) at the interfaces with adjacent freshwater and marine
habitats. This study highlights the rapid change that occurs in nekton community structure at low salinities, which is of
relevance to those managing freshwater inflow to estuaries. 相似文献
11.
Winter fog over the Indo-Gangetic Plains: mapping and modelling using remote sensing and GIS 总被引:1,自引:1,他引:0
Arun K. Saraf Ajoy K. Bora Josodhir Das Vineeta Rawat Kanika Sharma Sanjay K. Jain 《Natural Hazards》2011,58(1):199-220
Almost every year in the winter months (December–February), the vast Indo-Gangetic Plain south of the Himalaya is affected
by dense fog. This fog is considered as radiational fog, and sometime it becomes smog (when it mixes with smoke). The typical
meteorological, topographic and increasing pollution conditions over the Indo-Gangetic Plain are perhaps the common contributing
factors for fog formation. In the present study, the North Indian fog has been successfully mapped and analysed using NOAA-AVHRR
satellite data. In the winter seasons of 2005–06, 2006–07 and 2007–08, the fog-affected area has been found to cover about
575,800 km2, 594,100 km2 and 478,000 km2, respectively. Less fog in 2007–08 may be the consequence of high fluctuations in the meteorological parameters like temperature,
relative humidity and wind speed as related to the prevailing synoptic regime for that season. The dissipation and migration
pattern of fog in the study area has also been interpreted on the basis of the analysis of both meteorological and satellite
data. Further analysis of the fog-affected area allowed identifying more fog-prone regions. Analysis of past fog-affected
days and corresponding meteorological conditions enabled us to identify favourable conditions for fog formation viz. air temperature
3–13°C, relative humidity >87%, wind speed <2 m/s and elevation <300 m. Based on the observations of past fog formation and
corresponding governing parameters, fog for few selected days could be predicted in hind-sight and later verified with NOAA
images. 相似文献
12.
Nan D. Walker 《Estuaries and Coasts》2001,24(4):498-508
Changes in circulation, water level, salinity, suspended sediments, and sediment flux resulted from Tropical Storm Frances and Hurricane Georges in the Vermilion-Atchafalaya Bay region during September 1998. Tropical Storm Frances made landfall near Port Aransas, Texas, 400 km west of the study area, and yet the strong and long-lived southeasterly winds resulted in the highest water levels and salinity values of the year at one station in West Cote Blanche Bay. Water levels were abnormally high across this coastal bay system, although salinity impacts varied spatially. Over 24 h, salinity increased from 5 to 20 psu at Site 1 on the east side of West Cote Blanche Bay. Abnormally high salinities were recorded in Atchafalaya Bay but not at stations in Vermilion Bay. On September 28, 1998, Hurricane Georges made landfall near Biloxi, Mississippi, 240 km east of the study area. On the west side of the storm, wind stress was from the north and maximum winds locally reached 14 m s−1. The wind forcing and physical responses of the bay system were analogous to those experienced during a winter cold-front passage. During the strong, north wind stress period, coastal water levels fell, salinity decreased, and sediment-laden bay water was transported onto the inner shelf. As the north wind stress subsided, a pulse of relatively saline water entered Vermilion Bay through Southwest Pass increasing salinity from 5 to 20 psu over a 24-h period. National Oceanic and Atmospheric Administration (NOAA)-14 reflectance imagery revealed the regional impacts of wind-wave resuspension and the bay-shelf exchange of waters. During both storm events, suspended solid concentrations increased by an order of magnitude from 75 to over 750 mg l−1. The measurements demonstrated that even remote storm systems can have marked impacts on the physical processes that affect ecological processes in shallow coastal bay systems. 相似文献
13.
Restoration of Florida’s Everglades requires scientifically supportable hydrologic targets. This study establishes a restoration
baseline by developing a method to simulate hydrologic and salinity conditions prior to anthropogenic changes. The method
couples paleoecologic data on long-term historic ecosystem conditions with statistical models derived from observed meteorologic
and hydrologic data that provide seasonal and annual variation. Results indicate that pre-drainage freshwater levels and hydroperiods
in major sloughs of the Everglades were about 0.15 m higher and two to four times greater, respectively, on average compared
to today’s values. Pre-drainage freshwater delivered to the wetlands and estuaries is estimated to be 2.5 to four times greater
than the modern-day flow, and the largest deficit is during the dry season. In Florida Bay, salinity has increased between
5.3 and 20.1 with the largest differences in the areas near freshwater outflow points. These results suggest that additional
freshwater flows to the Everglades are needed for restoration of the freshwater marshes of the Everglades and estuarine environment
of Florida Bay, particularly near the end of the dry season. 相似文献
14.
The surface layers of the Bay of Bengal along the east coast of India exhibit intricate stratification owing to the differential
distribution of freshwaters. The winter (January–February) cooling of the salinity-induced stable layers results in the development
of thermal inversions that deteriorate toward the end of the season. The study focuses on the behavior of the thermal inversions
in the light of the variable stratification and the monsoon imposed reversing coastal current. To address the associated processes,
a three-dimensional Princeton Ocean Model is applied for the east coast of India, and numerical experiments carried out to
study the means by which the thermal inversions tend to perish with the passage of winter. The model domain with variable
curvilinear grid uses input fields that comprise realistic bathymetry and initial temperature/salinity conforming to winter/specified
stratification. The surface forcing comprises wind stress and diurnal pattern air–sea heat fluxes. The body forcing is derived
from the periodic tidal elevations at the open boundaries. It has been found that the thermal inversions tend to sustain as
the equator-ward flowing East India Coastal Current (EICC) traps the cool low saline waters between Paradip and Kakinada.
The current off Paradip is weak and variable and is not a part of EICC. Consequently, in the absence of replenishment of cool
and freshsurface waters, the temperature/salinity gradients get eroded steadily. No thermal inversions are noticed south of
Kakinada because of relatively weak current with diminished vertical salinity gradient. As the nature of stratification encountered
in the bay is highly variable due to diverse reasons, the behavior of internal waves under different stratification scenarios
is also addressed. Numerical experiments indicate that the energy/amplitude of the internal waves are comparable in the surface
layers for any stratification, where as it is certain orders exalted in the deeper waters of the strong stratification scenario.
Further, it is found that the energies and pattern of the temperature oscillations conform to the nature of mixed tide at
the corresponding latitude. The underneath stratification is found to be more responsible for the generation of internal waves compared to the local stratification. This implies that the body forcing emanating from below is the cardinal contributor for the generation of internal waves.
The numerical experiment with a flat and uniform bottom showing weak manifestation of internal waves endorses the same. This
connotes that the continental slopes are an effective generator of the internal waves and the energy flux conversion of the
barotropic tide to internal waves seems to be heavily dependent on the shoaling bottom. 相似文献
15.
The intra-seasonal variability observed in the salinity field of the upper layers at a few locations in the east central Arabian
Sea and the northern Bay of Bengal during the summer monsoon seasons of 1977 and 1979 is documented with the aid of short
time series (1–2 weeks) of salinity measurements made from USSR and Indian ships deployed during MONSOON-77 (1977) and MONEX-79
(1979) field experiments. In the Arabian Sea a typical subsurface maxima observed beneath the mixed layer base either disappeared
or considerably weakened due to strong vertical mixing caused by the monsoonal forcing. In the northern Bay of Bengal the
salinity variability in the top 30 m water column was rapid and appeared to be influenced by large amounts of fresh water
from rain and probably from the major adjoining rivers. Some simple diagnostic calculations are presented to assess the relative
importance of various processes which control the observed salinity variability. 相似文献
16.
Physical and chemical parameters were measured in a subtropical estuary with a blind river source in southwest Florida, United States, to assess seasonal discharge of overland flow and groundwater in hydrologic mixing. Water temperature, pH, salinity, alkalinity, dissolved inorganic carbon (DIC), δ18O, and δ13CDIC varied significantly due to seasonal rainfall and climate. Axial distribution of the physical and chemical parameters constrained by tidal conditions during sampling showed that river water at low tide was a mixture of freshwater from overland flow and saline ground-water in the wet season and mostly saline groundwater in the dry season. Relationships between salinity and temperature, δ18O, and DIC for both the dry and wet seasons showed that DIC was most sensitive to seawater mixing in the estuary as DIC changed in concentration between values measured in river water at the tidal front to the most seaward station. A salinity-δ13CDIC model was able to describe seawater mixing in the estuary for the wet season but not for the dry season because river water salinity was higher than that of seawater and the salinity gradient between seawater and river water was small. A DIC-δ13CDIC mixing model was able to describe mixing of carbon from sheet flow and river water at low tide, and river water and seawater at high tide for both wet and dry seasons. The DIC-δ13CDIC model was able to predict the seawater end member DIC for the wet season. The model was not able to predict the seawater end member DIC for the dry season data due to secondary physical and biogeochemical processes that altered estuarine DIC prior to mixing with seawater. The results of this study suggest that DIC and δ13CDIC can provide additional insights into mixing of river water and seawater in estuaries during periods where small salinity gradients between river water and seawater and higher river water salinities preclude the use of salinity-carbon models. 相似文献
17.
George P. Kraemer Robert H. Chamberlain Peter H. Doering Alan D. Steinman M. Dennis Hanisak 《Estuaries and Coasts》1999,22(1):138-148
Fluctuations in freshwater input may affect the physiology and survival of submerged aquatic vegetation (SAV) occurring in oligoaline to mesohaline estuarine regions. Controls on the distribution of the freshwater angiosperm Vallisneria americana, were investigated by transplanting ramets. Pots (3.8-1) containing ramets were distributed among four sites (upstream site [least saline], donor site, near downstream site, and far downstream site [most saline]) in the Caloosahatchee Estuary (Southwest Florida) during wet (May–August) and dry (October–February) seasons. During 2–4 mo of each season, physiological indicators were monitored, including photosynthesis, glutamine synthetase activity, and protein content in shoots, and carbohydrates and total nitrogen and carbon in shoot and subterranean tissues. Where the physical environment (light or salinity) was suboptimal, all physiological indices, except photosynthetic rate, showed similar stress responses, which ranged from a slow decline to a rapid drop in physiological function. Levels of soluble carbohydrates decreased in response to unfavorable conditions more rapidly than did insoluble carbohydrates. Shoot protein of V. americana declined prior to transplant death, suggesting that measuring protein content may provide a rapid assessment of physiological health. V. americana transplants at the low-salinity upstream site died during both wet and dry season experiments, likely in response to light limitation and/or partial burial by sediments. At the far downstream site, death occurred within 2–4 wk, and was attributable to elevated salinities (>ca. 15‰). Comparison of physiological responses with salinity and light regimes at the donor and near downstream sites suggest that light may ameliorate salinity stress. This study demonstrates that V. americana, nominally classed as a freshwater macrophyte, is capable of a remarkable degree of halotolerance. 相似文献
18.
This study assessed the levels of selected inorganic contaminants in streams and stream sediments in the effluent areas relating
to the pyrometallurgical and hydrometallurgical treatment of gold ores in the Obuasi gold mine, Ghana. Water and stream sediment
samples were taken from specific locations during the consecutive rainy and dry seasons, and concentrations of phosphate (PO4
3−), nitrate (NO3
−), chloride (Cl−), sulphate (SO4
2−), sodium (Na+), potassium (K+), calcium (Ca2+), magnesium (Mg2+), arsenic (As), copper (Cu), iron (Fe), zinc (Zn) and lead (Pb), were determined. Alkalinity, pH, temperature and specific
electrical conductivity were also measured. In the water samples, the average pH range for both the seasons is 6.9–7.4, most
anions and metals have relatively higher concentrations in the wet season than in the dry season at both the metallurgical
sites. Trace metals concentrations were comparatively low (<0.01–5.00 mg/l), higher in the dry season at the pyrometallurgical
sites. Irrespective of seasons, SO4
2− (0.80–949.50 mg/l) and PO4
3− (<0.01–6.30 mg/l) were pronounced at the pyrometallurgical sites, while NO3
− (0.01–98.45 mg/l) and Cl− (1.88-49.05 mg/l) were higher at the hydrometallurgical sites. In water samples, Ca2+ and SO4
2+ were the dominant cation and anion, respectively. In the stream sediments, except pH, NO3
−, Cl−, Na+ and Mg2+, all other parameter values were relatively higher at the hydrometallurgical areas. The average concentrations of Ca2+, Mg2+, As and Fe are remarkably high at both metallurgical sites (3,217–46,026 mg/kg). Overall, the level of parameters in the
water samples are pronounced at pyrometallurgical sites, whereas the levels in sediments are higher at the hydrometallurgical
sites. 相似文献
19.
Yoko Furukawa Janet L Watkins Jinwook Kim Kenneth J Curry Richard H Bennett 《Geochemical transactions》2009,10(1):2-11
Background
The dispersion-aggregation behaviors of suspended colloids in rivers and estuaries are affected by the compositions of suspended materials (i.e., clay minerals vs. organic macromolecules) and salinity. Laboratory experiments were conducted to investigate the dispersion and aggregation mechanisms of suspended particles under simulated river and estuarine conditions. The average hydrodynamic diameters of suspended particles (representing degree of aggregation) and zeta potential (representing the electrokinetic properties of suspended colloids and aggregates) were determined for systems containing suspended montmorillonite, humic acid, and/or chitin at the circumneutral pH over a range of salinity (0 – 7.2 psu). 相似文献20.
Meteorological fields variability over the Indian seas in pre and summer monsoon months during extreme monsoon seasons 总被引:1,自引:0,他引:1
U. C. Mohanty R. Bhatla P. V. S. Raju O. P. Madan A. Sarkar 《Journal of Earth System Science》2002,111(3):365-378
In this study, the possible linkage between summer monsoon rainfall over India and surface meteorological fields (basic fields
and heat budget components) over monsoon region (30‡E-120‡E, 30‡S30‡N) during the pre-monsoon month of May and summer monsoon
season (June to September) are examined. For this purpose, monthly surface meteorological fields anomaly are analyzed for
42 years (1958-1999) using reanalysis data of NCEP/NCAR (National Center for Environmental Prediction/National Center for
Atmospheric Research). The statistical significance of the anomaly (difference) between the surplus and deficient monsoon
years in the surface meteorological fields are also examined by Student’s t-test at 95% confidence level.
Significant negative anomalies of mean sea level pressure are observed over India, Arabian Sea and Arabian Peninsular in the
pre-monsoon month of May and monsoon season. Significant positive anomalies in the zonal and meridional wind (at 2 m) in the
month of May are observed in the west Arabian Sea off Somali coast and for monsoon season it is in the central Arabian Sea
that extends up to Somalia. Significant positive anomalies of the surface temperature and air temperature (at 2 m) in the
month of May are observed over north India and adjoining Pakistan and Afghanistan region. During monsoon season this region
is replaced by significant negative anomalies. In the month of May, significant positive anomalies of cloud amount are observed
over Somali coast, north Bay of Bengal and adjoining West Bengal and Bangladesh. During monsoon season, cloud amount shows
positive anomalies over NW India and north Arabian Sea.
There is overall reduction in the incoming shortwave radiation flux during surplus monsoon years. A higher magnitude of latent
heat flux is also found in surplus monsoon years for the month of May as well as the monsoon season. The significant positive
anomaly of latent heat flux in May, observed over southwest Arabian Sea, may be considered as an advance indicator of the
possible behavior of the subsequent monsoon season. The distribution of net heat flux is predominantly negative over eastern
Arabian Sea, Bay of Bengal and Indian Ocean. Anomaly between the two extreme monsoon years in post 1980 (i.e., 1988 and 1987)
shows that shortwave flux, latent heat flux and net heat flux indicate reversal in sign, particularly in south Indian Ocean.
Variations of the heat budget components over four smaller sectors of Indian seas, namely Arabian Sea, Bay of Bengal and west
Indian Ocean and east Indian Ocean show that a small sector of Arabian Sea is most dominant during May and other sectors showing
reversal in sign of latent heat flux during monsoon season. 相似文献