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1.
The aquifer system of the Upper Triassic Keuper Sandstone, an important source of drinking water in northern Bavaria, is
affected by elevated arsenic concentrations. Within the study area of 8000 km2, no evidence exists for any artificial source of arsenic. Data from about 500 deep water wells show that in approximately
160 wells arsenic concentrations are 10–150 μg/L. The regional distribution of arsenic in the groundwater shows that elevated
arsenic concentrations are probably related to specific lithofacies of the aquifers that contain more sediments of terrestrial
origin. Geochemical measurements on samples from four selected well cores show that arsenic has accumulated in the rocks.
This indigenous arsenic is the source of arsenic in the groundwater of certain facies of the middle unit of the Keuper Sandstone.
Received, June 1998 / Revised, January 1999, May 1999 / Accepted, June 1999 相似文献
2.
J. Pacheco Luis Marín Armando Cabrera Birgit Steinich Oscar Escolero 《Environmental Geology》2001,40(6):708-715
The nitrate concentration in 12 water-supply wells were monitored for the period April 1992 to March 1993. Each water-supply
well was sampled once a month. The nitrate concentrations in the 12 wells ranged from 7 to 156 mg/l. Two water-supply wells
(Chacsinkin and Peto) showed concentrations that reached 3.5 times the maximum permissible limit for the Drinking Water Standard
(45 mg/l). A third water-supply well (Akil) exceeds the norm for 7 out of 12 months. The use of nitrogen-rich fertilizers
are responsible for high nitrate concentrations in groundwater in the southern part of Yucatan, Mexico where intensive agricultural
practices exist.
Received: 14 December 1999 · Accepted: 2 May 2000 相似文献
3.
Philip T. Harte 《Environmental Earth Sciences》2017,76(6):251
A common assumption with groundwater sampling is that low (<0.5 L/min) pumping rates during well purging and sampling captures primarily lateral flow from the formation through the well-screened interval at a depth coincident with the pump intake. However, if the intake is adjacent to a low hydraulic conductivity part of the screened formation, this scenario will induce vertical groundwater flow to the pump intake from parts of the screened interval with high hydraulic conductivity. Because less formation water will initially be captured during pumping, a substantial volume of water already in the well (preexisting screen water or screen storage) will be captured during this initial time until inflow from the high hydraulic conductivity part of the screened formation can travel vertically in the well to the pump intake. Therefore, the length of the time needed for adequate purging prior to sample collection (called optimal purge duration) is controlled by the in-well, vertical travel times. A preliminary, simple analytical model was used to provide information on the relation between purge duration and capture of formation water for different gross levels of heterogeneity (contrast between low and high hydraulic conductivity layers). The model was then used to compare these time–volume relations to purge data (pumping rates and drawdown) collected at several representative monitoring wells from multiple sites. Results showed that computation of time-dependent capture of formation water (as opposed to capture of preexisting screen water), which were based on vertical travel times in the well, compares favorably with the time required to achieve field parameter stabilization. If field parameter stabilization is an indicator of arrival time of formation water, which has been postulated, then in-well, vertical flow may be an important factor at wells where low-flow sampling is the sample method of choice. 相似文献
4.
The San Antonio-El Triunfo mining district, located at a mountainous region 45 km south-east of La Paz, Baja California,
has been worked since the late 1700s. Mine waste material produced during 200 years of mineral extraction area poses a risk
of local groundwater pollution and eventually, regional pollution to the Carrizal (west basin) and the Los Planes (east basin)
aquifers. There are different types of deposits in the mining area. These are dominated by epithermal veins, in which arsenopyrite
is an important component. Carrillo and Drever (1998a) concluded that, even though the amount of mine waste is relatively
small in comparison to the large scale area, significant As in groundwater derived from the mine waste piles is found locally
in the groundwater. This paper shows the results of geochemical analyses of groundwater samples from the San Antonio-El Triunfo
area and the Carrizal and Los Planes aquifers during several years of monitoring (1993–1997). The highest values of total
dissolved solids (TDS) and As are in the mineralized area where the mining operations occurred (∼1500 ppm TDS and 0.41 ppm
As). The lowest concentrations of TDS and As are, in general, away from the mineralized area (∼500 ppm TDS and 0.01 ppm As).
Sulfate and bicarbonate (alkalinity) are, in general, high near the mineralized area and low away from it. The arsenic concentrations
vary seasonally, especially after the heavy summer thunderstorms. Geochemical modeling (MINTEQA2 and NETPATH) and analysis
of the regional geochemical evolution of the groundwater from the mining area towards the aquifer of Los Planes shows that
the most likely hydrochemical processes include: dilution, precipitation of calcite, and adsorption of As onto surfaces of
iron oxyhydroxides (ferrihydrite). These processes act as natural controls to the extent and amount of As pollution in the
Carrizal and Los Planes aquifers.
Received: 4 May 1999 · Accepted: 22 February 2000 相似文献
5.
Groundwater nitrate pollution in an alluvium aquifer, Eskişehir urban area and its vicinity, Turkey 总被引:1,自引:0,他引:1
A large amount of the water requirement (municipal, industrial, etc.) of Eskişehir city, Turkey, is supplied from groundwater
via wells in the urban area. The groundwater in the Eskişehir Plain alluvium has been polluted by municipal and industrial
wastewater, and agricultural activities. The nitrate concentrations at nine sampling points on Porsuk River, the main water
course in the plain, ranged from 1.5 to 63.3 mg/l during the period from July 1986 to August 1988. In the same period, the
nitrate concentrations measured in water from 51 wells ranged between 2.2–257.0 mg/l. The nitrate content of the groundwater
samples was 34.2% above 45 mg/l, the upper limit for nitrate in drinking water standards. High nitrate levels were observed
in water from wells in the central and eastern parts of the urban area. The nitrate content of the well water is subject to
seasonal fluctuation. In general, low nitrate concentrations were observed in wet seasons, and high ones in dry seasons.
Received: 16 April 1996 · Accepted: 2 October 1996 相似文献
6.
M. Ramakrishna Reddy N. Janardhana Raju Y. Venkatarami Reddy T. V. K. Reddy 《Environmental Geology》2000,39(3-4):342-352
Intensive application of surface water in command areas of irrigation projects is creating water logging problems, and the
increase of groundwater usage in agriculture, industry and domestic purposes (through indiscriminate sinking of wells) is
causing continuous depletion of water levels, drying up of wells and quality problems. Thus the protect aquifers to yield
water continuously at economical cost, the management of water resources is essential. Integrated geological, hydrological
(surface and groundwater) and geochemical aspects have been studied for the development and management of water resources
in drought-prone Cuddapah district. The main lithological units are crystallines, quartzites, shales and limestones. About
91 000 ha of land in the Cuddapah district is irrigated by canal water. A registered ayacut of about 47 000 ha is irrigated
by 1368 minor irrigation tanks. A total of 503 spring channels are identified in the entire district originating from the
rivers/streams, which has the capacity of irrigating about 8700 ha. The average seasonal rise in groundwater level is 7.32 m
in quartzites, 5.35 m in crystallines, 3.82 m in shales, 2.50 m in limestones and 2.11 m in alluvium. Large quantities of
groundwater are available in the mining areas which can be utilised and managed properly by the irrigation department/cultivators
for the irrigation practices. Groundwater assessment studies revealed that 584 million m3 of groundwater is available for future irrigation in the district. From the chemical analysis, the quality of groundwater
in various rock units is within the permissible limits for irrigation and domestic purposes, but at a few places the specific
conductance, chloride and fluoride contents are high. This may be due to untreated effluents, improper drainage system and/or
the application of fertilisers.
Received: 10 June 1998 · Accepted: 15 November 1998 相似文献
7.
Jonathan Levy Gordon Chesters Daniel P. Gustafson Harry W. Read 《Hydrogeology Journal》1998,6(4):483-499
A field study from October 1989 through July 1992, conducted on a 4.1-km2 area in south-central Wisconsin, USA, examined the distributions of atrazine and its chlorinated metabolites in groundwater
and related those distributions to the groundwater flow system. MODFLOW and PATH3D were used to assess bedrock-aquifer susceptibility
to contamination. Estimated travel time from water table to bedrock surface ranges from <0.25 to >512 yr. Spatial distribution
of the estimates demonstrates that increased travel time to bedrock can result from the presence of shallow surface-water
bodies, greater depths to bedrock, and smaller hydraulic conductivities. Estimated travel times to local domestic wells are
inversely related to atrazine and desethylated atrazine concentrations observed in water from those wells.
The potential impact of long-term atrazine use on aquifer water quality was investigated using MT3D in two best-case scenarios.
Uncertainties associated with predicted atrazine concentrations at various depths and times were estimated. For shallow groundwater,
widespread violations of Wisconsin's current preventive action limit were predicted, but with large uncertainty stemming from
uncertain estimates of input parameter values. The simulations indicate, however, that moderate inputs at the water table
are very unlikely to produce violations of Wisconsin's standards deeper in the aquifer.
Received, October 1997 Revised, July 1998 Accepted, July 1998 相似文献
8.
S. J. Appleyard 《Environmental Geology》1996,28(2):106-110
Drilling of 15 boreholes at a disused liquid waste disposal site near Perth, Western Australia, has indicated that a contamination
plume extends about 1000 m in a southerly direction from the site in the direction of groundwater flow. The plume is up to
600 m wide and 5–40 m thick. Chemical and microbiological analyses have indicated that contaminated groundwater contains high
concentrations of ammonia, iron, and bacteria at levels that commonly exceed national drinking water guidelines. It is likely
that a proposed water supply production well in the path of the contamination plume will have to be abandoned, and additional
wells may have to be abandoned if the plume continues to extend in the direction of groundwater flow. There is currently insufficient
information to indicate whether the plume is continuing to expand, but studies on similar plumes in the Perth metropolitan
area have indicated that contaminated groundwater can move at rates up to 100 m yr–1. Several other liquid waste disposal sites are now located in residential areas of Perth where wells are used for garden
irrigation. Further work is required to ensure that there is no potential impact of groundwater contamination on public health
in these areas.
Received: 31 July 1995 · Accepted: 18 September 1995 相似文献
9.
Irina Gaus 《Hydrogeology Journal》2000,8(2):218-229
Pesticides are a potential threat to the quality of extracted groundwater when the water-supply area is used for agricultural
activities. This problem is discussed for the water-supply area of Sint-Jansteen, The Netherlands, where measured pesticide
concentrations in the extracted water regularly exceed EU limits (0.1 μg/L). Groundwater samples taken from the aquifer within
the water-supply area show low contamination, but samples taken from the extracted water occasionally contain pesticides,
making the water inadequate for drinking-water purposes. The more intense contamination of the extracted water is caused by
the change in the natural groundwater flow pattern near the extraction wells. In this area, pesticide use cannot be avoided
easily, and an approach is given to differentiate pesticide use in the area according to expected travel time toward the wells
and the chemical characteristics of the pesticides. A groundwater flow model for the area is developed and the effects of
groundwater extraction on the natural flow pattern are evaluated. Using particle tracking, the travel-time zones are determined.
Combining these results and the degradation behavior of certain pesticides led to an optimal scheme to integrate agricultural
activities and groundwater extraction in the area. This is illustrated for five different types of pesticides (atrazine, simazine,
bentazone, MCPA, and mecoprop).
Received, October 1998/Revised, July 1999, September 1999/Accepted, November 1999 相似文献
10.
Salt-water discharges from a fault system in the crystalline basement of the Black Forest into the gravel aquifer of the
Kinzig River valley near Ohlsbach, upper Rhine River valley, southwestern Germany. The salt water (TDS, 16 g/kg) ascends from
a reservoir at 1 3 km depth. Once discharged into the gravel aquifer, the saline deep water mixes with fresh groundwater
and is carried along the groundwater flow path to the middle of the Rhine River valley. There, the natural geogene salt-water
plume merges with a man-made chloride-rich infiltration zone along the Rhine River. The plume was mapped using (1) chloride
data from groundwater observation wells, and (2) resistivity data from geoelectric sounding. Background chloride is about
7 mg/kg. In the central region of the plume, chloride concentration exceeds 200 mg/kg. A continuous area of Cl 1 50 mg/kg
is distinguished from the discharge fault to the Rhine River over a distance of 12 km. Resistivities range from 1 50 Ω in
uncontaminated regions to <7 Ω in the 700 m-long central region of the plume. A low resistivity plume (7–10 Ω) stretches for
1 7 km into the Rhine River valley. The two plume maps are in good agreement.
Received, April 1998 / Revised, November 1998, January 1999 / Accepted, January 1999 相似文献
11.
Geoffrey D. Smith Robbert Wetselaar James J. Fox Robert H. M. van de Graaff Doeljachman Moeljohardjo Joko Sarwono Wiranto Sri Rahajoe Asj'ari Suharto Tjojudo Basuki 《Hydrogeology Journal》1999,7(6):576-589
The causes and nature of nitrate pollution of wells in a village within Kotagede, a subdistrict of the city of Yogyakarta,
Indonesia, were investigated in a detailed hydrological study. Nitrate concentrations in groundwater frequently exceeded the
WHO recommended limit of 50 mg L − 1. Groundwater nitrate concentrations were measured over a 19-month period in monitoring wells and in piezometers placed strategically
in relation to sewage tanks within the village. Results indicate that the tanks are major sources of nitrate in the groundwater
and that the input is markedly dependent on rainfall, resulting in a surge of nitrate into the groundwater at the beginning
of each wet season. That the tanks are a major source was confirmed by measuring nitrate in soil cores obtained by augering
close to selected tanks. Washrooms, where people wash themselves, are not significant sources of nitrate. Faecal coliform
counts in groundwater from a random selection of wells are very high. The results have implications for the siting of wells
and toilets within villages in Indonesia.
Received, January 1999/Revised, August 1999/Accepted, August 1999 相似文献
12.
The CO2-rich thermal groundwater in the Betic Cordilleras in Spain has been studied with regard to the geological and hydrogeological
setting, physical and chemical characteristics, and 13C-isotope content. The study area is about 60 km northeast of Almería city, in southeastern Spain. The thermomineral waters
are plentiful and are related to regional geothermal anomalies. Temperatures of 20 −41°C, high bicarbonate concentrations
(183–1824 mg/L), and high amounts of PCO2 (<1.1 bar) characterize the groundwater. CO2 spatial variations are related to proximity to the Carboneras, Palomares, and Guadalentín fault systems, which may be the
surface representation of the zone of crustal thinning and magmatism. δ
13C values probably indicate a deep source for the CO2, either the mantle or perhaps carbonate rocks in the metamorphic substratum. The high amount of CO2 in the groundwater causes problems in wells and severely restricts water usage. The hydrothermal features of this area are
probably related to neotectonic activity.
Received, September 1998/Revised, June 1999, September 1999/Accepted, December 1999 相似文献
13.
B. J. M. Goes 《Hydrogeology Journal》1999,7(3):294-304
The Hadejia–Nguru Wetlands are annually inundated flood plains in semi-arid northeastern Nigeria. The area has a unique ecosystem
that forms a natural barrier against the encroachment of the Sahara desert. Both the rich wetland vegetation and local farmers
using shallow tube wells depend on a groundwater mound (with a water table less than 6 m below the surface) that is present
in the unconfined aquifer under the flood-plain area. Using well records (1991–97) and a hydrogeologic profile based on piezometers
that were monitored for two years, it is shown that recharge through the annually inundated flood plains is the source of
the groundwater mound. Maintenance of the groundwater-recharge function of the flood plains depends on wet-season releases
from two large upstream dams. On the basis of a water-budget method, the mean (1991–97) wet-season unconfined groundwater
recharge in the flood-plain area between Hadejia and Nguru and in the immediate vicinity (1250 km2) is estimated to be 132 mm (range, 73–197 mm). Outflow from the unconfined flood-plain aquifer to the unconfined upland aquifer
is approximately 10% of the wet-season flood-plain recharge. The unconfined groundwater outflow from the flood-plain area
can provide a significant contribution to the present-day rural water supply in the surrounding uplands, but it does not offer
much potential for additional groundwater abstraction. In addition to outflow to the upland aquifer (∼14 mm), the distribution
of the annually recharged water volume of the shallow flood-plain aquifer is (1) domestic uses (3 mm), (2) small-scale irrigation
(∼15 mm), and (3) evapotranspiration ( 1 100 mm). Along the hydrogeologic profile, the recharge in the upland (i.e., outflow
from the unconfined flood-plain aquifer and possibly diffuse rain-fed recharge) is in balance with the water uses (i.e., domestic
uses, groundwater outflow, and evapotranspiration). The absence of a seasonal water-level trend in the two piezometers in
the upland indicates that no rain-fed recharge occurs through preferential path-way (macropore) flow.
Received, June 1998 / Revised, November 1998, January 1999 / Accepted, January 1999 相似文献
14.
Salt-water intrusion and nitrate contamination in the Valley of Hermosillo and El Sahuaral coastal aquifers, Sonora, Mexico 总被引:1,自引:0,他引:1
The Valley of Hermosillo coastal aquifer, state of Sonora, northwestern Mexico, has been over-exploited for the last four
decades, in order to maintain agricultural activity in one of the most important irrigation districts of the Mexican Republic.
The over-exploitation has resulted in the development of several drawdown cones and in the lowering of the water table to
as much as 50 m below mean sea level. Contamination of the aquifer in the form of salt-water intrusion from the Gulf of California
and high nitrate concentrations is the consequence of human activities. A hydrogeochemical zonation of the aquifer, based
on the presence of different water families, led to the identification of a coastal band approximately 30 km wide that is
affected by salt-water intrusion. Conductivity of the sampled water and the interpretation of the ratio Na/Cl×1000 was used
to identify the location of three major intrusion plumes in this coastal band. The background nitrate contamination of the
aquifer is about 4 ppm, but contents as great as about 17 ppm occur in some wells. Irrigation with raw sewage and movement
of contaminants in areas of high hydraulic gradients within the drawdown cones probably are responsible for localized peaks
of the nitrate concentration.
Received, October 1996 Revised, September 1997, May 1998 Accepted, July 1998 相似文献
15.
Geochemistry, genesis, and health implications of fluoriferous groundwaters in the upper regions of Ghana 总被引:9,自引:2,他引:9
The most appropriate and widely used source of drinking water for the populations of the upper regions of Ghana is groundwater.
In general, groundwater quality is acceptable except for some parts of the Bolgatanga and Bongo Districts, where there are
occurrences of elevated levels of natural groundwater fluoride. Concentrations of groundwater fluoride in excess of the World
Health Organization (WHO) maximum guideline value (1.5 mg/l) in the Bongo area have been known since 1978. However, the effect
of fluoride on people ingesting the water did not receive public and medical attention until October 1993, when health personnel
were asked to investigate the cause of stained teeth in school children. The investigation established that 62% of the total
population of school children in the Bongo area had dental fluorosis. Against this background, a study was initiated to understand
the geochemistry, genesis, and distribution of fluoride in relation to the geology of the area. Groundwater fluoride in the
upper regions ranges from 0.11 to 4.60 ppm, with the highest concentrations associated with the fluorine-enriched Bongo coarse-grained
hornblende granite and syenite suite. The source of groundwater fluoride within the Bongo granitoids is dissolution of the
mineral fluorite and dissolution of and anion exchange with micaceous minerals and their clay products. Applying the WHO recommended
guideline values for fluoride in drinking water reveals that 49% of wells in the area deliver water below the optimum level
of 0.5 mg/l F–; these populations are thus prone to dental caries. Twenty-eight percent of the wells fall within the optimum interval for
good dental health (0.5–1.5 mg/l F–). Twenty-three percent of the wells have concentrations above the recommended maximum guideline limit of 1.5 mg/l F–; this population is susceptible to dental and possibly skeletal fluorosis. Climatic conditions of the area suggest that the
individual water consumption is in the order of 3 to 4 l which is higher than the WHO estimate of 2 l/adult/day. In addition,
dietary intake for the upper region population is probably higher than WHO baseline values (0.2–0.5 mg/day). This implies
that a much higher population is susceptible to developing dental and skeletal fluorosis than originally suspected. Geochemical
symbol plot maps help geochemists understand factors controlling the distribution and uptake of fluoride in the upper regions,
but they are of minimal value to health officials responsible for planning epidemiological studies and dental health education
programs in the region. By casting fluoride data into contoured 'geochemical health-risk maps' using intake interval guidelines
more closely aligned to regional climatic and dietary conditions, health officals can better judge the impacts (regional and
population based) of fluoride on segments of the population, such as various sex and age groups.
Received: 11 March 1997 · Accepted: 17 June 1997 相似文献
16.
Toxic metal contamination in the lateral lakes of the Coeur d'Alene River valley, Idaho 总被引:3,自引:0,他引:3
K.F. Sprenke W.C. Rember S.F. Bender M.L. Hoffmann F. Rabbi V.E. Chamberlain 《Environmental Geology》2000,39(6):575-586
The 11 lateral lakes of Coeur d'Alene River valley in northern Idaho have received heavy metal contamination from over a
century of upstream mining. The lateral lakes lie within the flood plain of the Coeur d'Alene River, and in their bottom sediments
is preserved a stratigraphic record of the upstream mining operations. To characterize the contaminated sediments in the lateral
lakes, sampling techniques, including the Livingston piston corer and the Huttenen freeze box, have been developed by Quaternary
geologists to preserve the vertical stratigraphy in the samples. From 26 cm to over 55 cm of undisturbed tailing sediments,
commonly with “varve-like” features, have been found in each of the lateral lakes, with maximum concentrations by weight of
lead at 3.8%, zinc at 3.4%, arsenic at 340 mg/kg, cadmium at 120 mg/kg and mercury at 7 mg/kg. The contamination in the lakes
appears to be restricted to the shallow subsurface and heavy metal concentrations generally drop to background levels within
a meter of depth.
Received: 22 May 1998 · Accepted: 21 September 1998 相似文献
17.
To accurately measure the pH, Eh, EC and temperature of groundwater retrieved from boreholes, a deep groundwater sampling
apparatus was developed which provided sensory measurements both in situ and in a flow-through cell at ground level. Under
a pressure of 1×106 Pa the in situ accuracy of the apparatus sensor was within the following limits: pH ±0.2, temperature ±0.1°C, Eh ±10 mV,
and EC ±2.4%. The measuring and sampling of deep groundwater from a borehole of more than 1000 m in depth was performed continuously
for 30 days. Values of pH were the same for the in situ sensor, the flow-through cell sensor and the laboratory measurements
of the sampled water. At the beginning of the sampling period, Eh values of the in situ sensor indicated deep groundwater
conditions. The apparatus is particularly useful for Eh measurement. Chemical composition and stable isotope ratios indicated
that the groundwater sampled from more than 1000 m depth was a connate water with a chemical composition slightly different
from seawater of the present time, and the groundwater retrieved from 800 m depth was a meteoric water. Natural radioactive
elements are thought to be the origin of the tritium in the groundwater retrieved from the 1000 m depth.
Received: 6 August 1996 / Accepted: 22 October 1996 相似文献
18.
V. V. S. Gurunadha Rao R. L. Dhar T. Jayachand C. S. Khoker 《Environmental Geology》2000,39(10):1138-1146
Mathura oil refinery was commissioned during 1977 and effluent storage ponds were constructed at the same time. These storage
ponds receive wastewater from the refinery at a rate of 10000 m3/day. After treatment, waste water is discharged through a 3-km pipeline to a stream leading to the Yamuna river. The groundwater-monitoring
as well as water-quality monitoring was carried at 24 observation wells in the refinery site during 1997. The water quality
measurements indicated total dissolved chloride and sulphate concentration of native groundwater as 400 mg/l, whereas elevated
levels up to 600 mg/l were found at the wells close to polishing ponds. Thus combined transport of chloride and sulphate was
simulated in the mass transport model. A three-dimensional flow, pathlines and mass transport model of the aquifer system
were constructed to analyze the impact of seepage from polishing ponds contaminating the groundwater regime. The permeability
of aquifer varies between 1.5–2.5 m/day. The porosity of formation was assumed as 0.2. The constant head and constant concentration
boundaries were assigned to the nodes representing effluent storage ponds. Longitudinal dispersivity of 100 m, horizontal
transverse dispersivity of 10 m and vertical transverse dispersivity of 0.01 m were assumed. The mass transport model was
calibrated for 20 years by comparing total dissolved chloride and sulphate concentrations from 1997. The model predictions
indicate further migration of contaminants on the east of effluent ponds in future.
Received: 4 January 1999 · Accepted: 12 July 1999 相似文献
19.
Influence of arsenic-bearing gold deposits on water quality in Zloty Stok mining area (SW Poland) 总被引:3,自引:2,他引:1
The Sudety Mountains contain polymetallic deposits which have been exploited since the Middle Ages. Distinct concentrations
of As, Hg, F, Cr in surface water near Zloty Stok suggested that groundwater in the area could also contain elevated metal
concentrations. Water samples from 15 locations including Zloty Stream, mine adit discharges, and selected springs generally
show low levels of dissolved components and near-neutral pH. However, arsenic concentrations range from 0.99 mg/l to 26.16 mg/l
at all 15 sample locations. Mercury concentrations were locally as high as 0.011 mg/l. These high arsenic and mercury concentrations
significantly exceed water quality standards and raise concerns for using Zloty Stream for potable water.
Recieved: 21 December 1998 · Accepted: 8 June 1999 相似文献
20.
Karstic aquifers are highly susceptible to rapid infiltration of river water, particularly during periods of high flow. Following
a period of sustained rainfall in the Suwannee River basin, Florida, USA, the stage of the Suwannee River rose from 3.0 to
5.88 m above mean sea level in April 1996 and discharge peaked at 360 m3/s. During these high-flow conditions, water from the Suwannee River migrated directly into the karstic Upper Floridan aquifer,
the main source of water supply for the area. Changes in the chemical composition of groundwater were quantified using naturally
occurring geochemical tracers and mass-balance modeling techniques. Mixing of river water with groundwater was indicated by
a decrease in the concentrations of calcium, silica, and 222Rn; and by an increase in dissolved organic carbon (DOC), tannic acid, and chloride, compared to low-flow conditions in water
from a nearby monitoring well, Wingate Sink, and Little River Springs. The proportion (fraction) of river water in groundwater
ranged from 0.13 to 0.65 at Wingate Sink and from 0.5 to 0.99 at well W-17258, based on binary mixing models using various
tracers. The effectiveness of a natural tracer in quantifying mixing of river water and groundwater was related to differences
in tracer concentration of the two end members and how conservatively the tracer reacted in the mixed water. Solutes with
similar concentrations in the two end-member waters (Na, Mg, K, Cl, SO4, SiO2) were not as effective tracers for quantifying mixing of river water and groundwater as those with larger differences in
end-member concentrations (Ca, tannic acid, DOC, 222Rn, HCO3).
Received, March 1999 / Revised, July 1999 / Accepted, July 1999 相似文献