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1.
The present study fills a gap in the knowledge in regards to the occurrence of banned pesticides at both coastal and inland locations at the Southwest Buenos Aires region, Argentina. Superficial sediment and soil samples were collected from different sites along the Bahia Blanca Estuary and surrounding sites to assess the concentration levels and spatial distribution of 12 selected organochlorine pesticides (OCs); 13 spatial locations including inland and shore-coast were sampled to evaluate occurrence and concentration levels of hexachlorocyclohexanes α-HCH, β-HCH, δ-HCH, γ-HCH, dichlorodiphenyltrichloroethane and its degradation products (DDXs: p,p′-DDT, o,p′-DDT, p,p′-DDE, o,p′-DDE, p,p′-DDD, o,p′-DDD) and the polychlorobenzenes PeCB (pentachlorobenzene) and HCB (hexachlorobenzene). After cleaning and extractions steps, samples were analyzed by means of gas chromatography/mass spectrometry. ∑OCs (sum of all studied compounds) ranged between 0.206 and 1040 ng g?1 dw (mean?=?82.4 and SD?=?277 ng g?1 dw). Total HCHs (sum of α-HCH, β-HCH, γ-HCH and δ-HCH) ranged from 0.0858 to 0.876 ng g?1 dw (mean?=?0.43 and SD?=?0.23 ng g?1 dw), DDXs (sum of p,p′and o,p′ isomers) from 0.080 to 1040 ng g?1 dw (mean?=?81.3 and SD?=?277 ng g?1 dw). Lower concentrations were found for PeCB (mean?=?0.095 and SD 0.17 ng g?1 dw) and HCB (mean?=?0.56 and SD 1.7 ng g?1 dw). Principal component analysis (PCA) permitted the extraction of underlying information about common factors, providing an overview of the distribution of pesticides and allowing the characterization of sites in regards to the major pesticide signature.  相似文献   

2.
To investigate the groundwater levels changes effects on the transpiration of Salix psammophila (S. psammophila) bush, systemic measurements of meteorological conditions, sap flow of S. psammophila, soil water contents and groundwater levels were conducted in the Hailiutu River catchment, NW of China. Based on the collected field data, Hydrus-1D software package was used to calibrate water movement for root uptake in the saturated–unsaturated zone. The soil hydraulic parameters and root uptake function parameters were calibrated. The simulated results of soil water contents and sap flow fitted well with the observed ones. Based on the calibrated hydraulic parameters, different groundwater levels were imposed at the low boundary to simulate the groundwater levels changes effects on the transpiration. The relationship between ratio of actual transpiration and potential (T/T p) and groundwater water table depth was established. The results shows that the ratio of actual transpiration and potential transpiration decreases with groundwater table depth increase as inverse ‘S’ shape. And the turn point is corresponding to the extinct depth, i.e., no groundwater contribution to S. psammophila transpiration. To further verify this phenomenon is universal, the soil hydraulic parameters were replaced with the other five groups in the calibrated forward model. The results confirmed the similar changes of T a/T p with the groundwater levels changed, i.e. inverse ‘S’ shape. However, the extinction depth is different corresponding to different soil hydraulic parameters. So, the research results indicated the relationship between transpiration and groundwater levels is non-linear function.  相似文献   

3.
The Miocene Ar Rajmah Group, exposed along the Soluq-Al Abyar road cut in southern Al Jabal Al Akhdar, NE Libya, is very rich in both micro- and macrofossils, especially molluscs and echinoids. Seven shell concentrations were recognized of which four from the Benghazi Formation; pectinids–small oyster concentration (BSC1), Echinolampas sp.–Clypeaster cf. martini concentration (BSC2), molluscan shell concentration (BSC3), and Echinolampas cf. amplus–Clypeaster acclivis concentration (BSC4). Three shell concentrations occur in the Wadi Al Qattarah Formation; large oyster concentration (QSC1), Crassostrea gryphoides–Chlamys zitteli concentration (QSC2), and Cubitostrea digitalina concentration (QSC3). The main factors controlling the formation of the shell concentrations were storm-induced waves and currents, reduced sediment input, settling behavior of benthic macro-invertebrates, and productivity.  相似文献   

4.
Understanding the changes in permeability of soil, when soil is subjected to high confining pressure and flow pressure, which may alter the textural and geomechanical characteristics of soil, is of great importance to many geo-engineering activities such as, construction of high-rise buildings near the coast or the water bodies, earthen dams, pavement subgrades, reservoir, and shallow repositories. It is now possible to evaluate the changes in permeability of soil samples under varying conditions of confining pressure and flow pressure using flexible wall permeameter (FWP). In the present study, investigation was carried out on a cylindrical sample of granular soil employing FWP under varied conditions of confining pressure (σ3)—50–300 kPa, which can simulate the stress conditions equivalent to depth of about 20 m under the earth’s crust, and a flow pressure (fp)—20–120 kPa, which is mainly present near the small earthen embankment dams, landfill liners, and slurry walls near the soft granular soil with high groundwater table. The obtained results indicate a linear relationship between hydraulic conductivity (k) with effective confining pressure (σeff.), k, decreasing linearly with an incremental change in σeff.. Further, k increases significantly with an increase in fp corresponding to each σeff., and q increases significantly with increase in the fp corresponding to each (σ3). It was also observed that corresponding to the low fp of 20 kPa, the reduction in k is nonlinear with σ3. The percentage reduction in k is observed to be 9, 13, and 27% corresponding to σ3 of 50–100, 100–200, and 200-300 kPa, respectively.  相似文献   

5.
Pathogen removal is essential for wastewater treatment and its potential reuse in agriculture. Three field-scale wastewater treatment systems consisting of free surface flow were operated around 1.5 years receiving water from urban domestic, rural domestic and industrial sources. The study was conducted to evaluate seasonal performance of constructed wetland systems in removing Escherichia coli, Enterococci and total coliforms under continuous hydraulic flow. Results displayed that all three wetlands gain recognition in removing pathogen load with high removal efficacy till water reaches output ports. Removal efficiencies were even higher, 66–93, 78–92 and 80–94% for E. coli, Enterococci and total coliforms, respectively, within constructed wetlands. Remarkably at shorter temporal scales in CW-A, greater homogeneity of pathogen concentrations was assessed at wetland outlet sites. In outlet ports, results displayed a highly effective removal of E. coli concentration 80–90% (June 2015), 86–92% (October 2015) and 79–92% (February 2016), Enterococci 80–94% (June 2015), 83–94% (October 2015) and 80–94% (February 2016) and total coliforms 85–93% (June 2015), 87–95% (October 2015) and 88–96% (February 2016). Positive correlation was observed between bacterial indicators (E. coli–Enterococci, r = 0.038; p < 0.01 and E. coli–total coliforms, r = 0.142; p < 0.01). Removal of bacterial indicators in constructed wetland was also displayed by PCA in which three-component analysis of variance was 98.39% and showed a clear decrease in measured parameter gradients toward samples from outlet ports. Constructed wetlands provide cost-effective treatment systems for reducing the pathogen load in wastewater in variable agro-climatic conditions and thus improve water quality.  相似文献   

6.
This study investigates the characteristics of geothermal water in 10 geothermal fields in Beijing. The relationships between the deuterium excess parameter (d) and temperature, depth, age of geothermal groundwater, groundwater flow field, and Eh were investigated using geothermal groundwater samples. Results showed that (1) the average d value of geothermal water is 5.4, whereas that of the groundwater in normal temperature is 6.04. The differences are induced by the oxygen isotope exchange during the water–rock interaction, which may be more easily completed in geothermal water than in cold groundwater. (2) The d value increases remarkably with the age of the geothermal groundwater. The d value increases from 11.2 to 14.6 when the age of the geothermal water is 12,760 ± 130 a and 38,960 ± 630 a, respectively. Moreover, the isotope heat exchange for composition of the hydrogen and oxygen isotopes in the geothermal groundwater proceeds sufficiently with time. (3) The d value decreases from 5.72 to 3.03 when the depth increases from 125.13 to 3221 m. Generally, in the same area, the d value decreases with depth because the temperature is increasing. (4) The d value of the groundwater gradually reduces from the northern recharge area to the southern discharge area. The average d value is 7.31 in the northern recharge area and 5.68 in the middle Beijing Depression, whereas the d value in the southern area of Fengheying is ?9.20. The larger difference in d values between the recharge and discharge areas is due to the slower velocity of underwater flow, which induces longer time for oxygen exchange. (5) The relationship between the d and Eh is complex. When Eh is <200 mV, the d value of the geothermal water decreases with the decrease in Eh. When Eh is higher than 200 mV, the d value increases slightly with the decrease in Eh. The study of the characteristics of deuterium excess parameters for geothermal water could provide a scientific isotopic evidence for assessment and exploitation measures in geothermal groundwater systems.  相似文献   

7.
Soil erosion is a major environmental problem in arid and semi-arid areas. Although bioengineering is important in preventing soil erosion, plant architecture and mechanical properties in these areas are rarely studied. In this study, in order to evaluate the potential of native plants to reduce soil erosion in semi-arid regions, their above-ground (e.g., stem density, radius of the stem, etc.) and below-ground (e.g., root area ratio, root tensile strength, etc.) characteristics were measured in the field and laboratory. Five indicators, namely, stem density (SD), sediment obstruction potential (SOP), plant stiffness (MEI), relative soil detachment (RSD), and root cohesion (Cr), were taken into account. Each indicator was scored according to a five-point scale (0?=?low, 4?=?high), and then, the score of each indicator was represented on an ameba diagram. Finally, for understanding traits of plants and evaluating their potential to control rill and gully erosion, the area occupied by the ameba diagram was studied. The results indicated that the shrub Ziziphus spina-christi (MEI?=?108.35 N, RSD?=?0.398, Cr?=?8.34 kPa, SOP?=?0.097, and SD?=?0.00270) is a very suitable native plant species for controlling both the gully and rill erosion. In addition, Scariola orientalis is effective for sediment obstruction, but its low scores on the MEI and RSD indicators imply that it is not able to control gully development. Furthermore, Noaea mucronata, Platychaete glaucescens, Astragalus gummifer, Alhagi persarum, Lycium shawii, and Prosopis farcta have a distinct potential to reduce the rate of gully erosion. These results have wide applicability for adopting soil conservation measures to other semi-arid environments.  相似文献   

8.
The city of Tulum, in the state of Quintana Roo (Mexico) depends almost exclusively on groundwater for water supply. The groundwater is exploited from a coastal aquifer which contains a karst network that is considered as one of the largest ones on earth. Given the nature of karst aquifers, the whole area is very sensitive to contaminants and bacteria transport, because flow paths, residence time and degradation rates differ significantly from what can be observed in the porous aquifer. The present study focuses on isotopes (18O and 2H), dissolved ions’ concentration and Escherichia coli (E. coli). The result of our survey points out the anthropic impact on groundwater quality. Furthermore, the chloride concentrations illustrate the influence of seawater mixing and geological heterogeneity over the study area. Due to an exponential growth of the tourism industry, the needs in terms of water supply and water treatment increase significantly. Tulum is a coastal city, facing a coral reef and is bordered by the Sian Ka’an biosphere reserve, therefore, an environmental issue is added to the sanitary issue, both being the basis of the local economic development. Our results show that E. coli remains a major issue, as several samples tested were contaminated, in particular those in the city center. Ions’ survey shows an anthropic impact through nitrate, phosphate and fluoride concentrations, but the obtained values are not alarming. Considering the saline intrusion, chloride concentrations indicate that the area below the Tulum city center seems to be less permeable (and maybe less karstified) than the surrounding areas, as groundwater is less subject to seawater mixing than other sampling sites at similar distance to the coast.  相似文献   

9.
A high-spatial resolution study design was used to investigate the relationship between land use practices, stream physicochemistry, hydroclimate, and stream Escherichia (E) coli concentrations in a mixed-land-use watershed in the Appalachian region. Stream samples were collected daily from six monitoring sites and analyzed for total E. coli counts using an enzyme metabolism indicator method. Statistical comparison of E. coli concentration time series showed significant (p?<?0.05) differences between study sites. Although highest average E. coli concentrations were observed at two agricultural sites (534 and 582 colony-forming counts (CFU) per 100 mL, respectively), highest total loadings were observed within the receiving stream, with values increasing downstream (2?×?1012 and 4.2?×?1012 study total CFU for bracketed upstream and downstream sites, respectively). No single physical variable displayed a significant correlation (p?<?0.05) with observed E. coli concentration at every site. However, sites displayed different patterns of significant correlations (p?<?0.05) between E. coli concentration and both physicochemical (e.g. pH, dissolved oxygen saturation) and hydroclimate variables (e.g. streamflow and precipitation). Percent agricultural land cover was the only land use category that showed significant (p?<?0.04) correlation with study average E. coli concentrations, thereby emphasizing the importance of land use practices to stream pathogen regimes. Results validate the analytical method and provide high-resolution, detailed, quantitative characterizations of stream E. coli regimes, thereby supplying land and water resource managers with science-based information to advance management decisions and improve public health.  相似文献   

10.
The present study explores the spatial and temporal deviations in temperature using Monte Carlo (MC) and Sen’s slope (SS) approaches in the Hindu Kush (HK) region. Climate change holds sturdy association against the temperature trend that has generated adverse impacts in the form of floods. In this attempt, for trend analysis, temperature has been selected as a meteorological parameter. This study mainly focuses on exploring the tendency in average temperature with respect to time and the consequential flood recurrences in the region. For the current study, data regarding temperature were typically collected from Pakistan Meteorological Department. In the study region, there are a total of seven meteorological station falls namely Dir, Chitral, Drosh, Saidu, Malam Jabba, Kalam, and Timergara. The temperature time series data was calculated and analyzed using MC and SS approaches for trend detection in order to demonstrate the kind of fluctuation in the Hindu Kush region. The resultant analysis further revealed that in the meteorological station of Dir, a more significant positive trend (α?=?0.0001) was found in mean monthly maximum, minimum, and monthly normal temperature. Likewise, at Drosh, a positive trend is detected in mean monthly maximum (α?=?0.04), monthly minimum (α?=?0.003), and monthly average (α?=?0.0005). Moreover, at Saidu met station, there is also a trend detected in temperature sub-variables such as monthly maximum (α?=?0.0001) and monthly minimum (α?=?0.001). In addition to these, at Kalam, there is a temperature trend noted for monthly minimum (α?=?0.01) and monthly average (α?=?0.02). Furthermore, the analysis demonstrates that there is no trend detected in the remaining stations, i.e., Chitral, Malam Jabba, Drosh, and Timergara. The overall analysis discovered that there is a sturdy relationship between climate change phenomenon and temperature variability. After using SS test to the temperature data of mean monthly maximum (TMMMax), the results explored that Kalam station grips the highest magnitude, i.e., Q?=?0.76; however, Timergara shows the lowermost, i.e., Q?=???0.34. For the monthly minimum temperature (TMMMin), at Kalam again, the highest value (Q?=?0.005) was detected; however, other stations revealed a negative trend, except Drosh which express no change in terms of magnitude. Similarly, in terms of monthly normal temperature (TMNor), Timergara station (Q?=???0.4) verified a negative trend magnitude and Malam Jabba station again trendless. Among all, the met station of Malam Jabba which holds an altitude of 2591 m is a hilly station just followed by Kalam having 2103 m height; however, Dir holds 1375 m height and the rest of the met stations show low elevation. The main reason for the temperature difference is the altitude of the study region.  相似文献   

11.
Nutrient inputs have degraded estuaries worldwide. We investigated the sources and effects of nutrient inputs by comparing water quality at shallow (< 2m deep) nearshore (within 200 m) locations in a total of 49 Chesapeake subestuaries and Mid-Atlantic coastal bays with differing local watershed land use. During July–October, concentrations of total nitrogen (TN), dissolved ammonium, dissolved inorganic N (DIN), and chlorophyll a were positively correlated with the percentages of cropland and developed land in the local watersheds. TN, DIN, and nitrate were positively correlated with the ratio of watershed area to subestuary area. Total phosphorus (TP) and dissolved phosphate increased with cropland but were not affected by developed land. The relationships among N, P, chlorophyll a, and land use suggest N limitation of chlorophyll a production from July–October. We compared our measurements inside the subestuaries to measurements by the Chesapeake Bay Program in adjacent estuarine waters outside the subestuaries. TP and dissolved inorganic P concentrations inside the subestuaries correlated with concentrations outside the subestuaries. However, water quality inside the subestuaries generally differed from that in adjacent estuarine waters. The concentration of nitrate was lower inside the subestuaries, while the concentrations of other forms of N, TP, and chlorophyll a were higher. This suggests that shallow nearshore waters inside the subestuaries import nitrate while exporting other forms of N as well as TP and chlorophyll a. The importance of local land use and the distinct biogeochemistry of shallow waters should be considered in managing coastal systems.  相似文献   

12.
The b-value of the Gutenberg–Richter’s frequency–magnitude relation and the p-value of the modified Omori law, which describes the decay rate of aftershock activity, were investigated for more than 500 aftershocks in the Aksehir-Afyon graben (AAG) following the 15 December 2000 Sultandagi–Aksehir and the 3 February 2002 Çay–Eber and Çobanlar earthquakes. We used the Kandilli Observatory’s catalog, which contains records of aftershocks with magnitudes ≥2.5. For the Çobanlar earthquake, the estimated b-values for three aftershock sequences are in the range 0.34 ≤  b ≤ 2.85, with the exception of the one that occurred during the first hour (4.77), while the obtained p-values are in the range 0.44 ≤ p ≤ 1.77. The aftershocks of the Sultandagi earthquake have a high p-value, indicating fast decay of the aftershock activity. A regular increase of b can be observed, with b < 1.0 after 0.208 days for the Çay–Eber earthquake. A systematic and similar increase and decrease pattern exists for the b- and p-values of the Çobanlar earthquakes during the first 5 days.  相似文献   

13.
The enzyme-labeled fluorescence (ELF-97®) substrate produces an insoluble, fluorescent yellow-green product at the site of alkaline-phosphatase (AP) activity. Fifteen coastal phytoplankton species were tested to determine if AP activity could be detected in phosphate-depleted media. All species tested, except Synechococcus bacillaris, expressed AP activity. Subsequently, threshold concentrations of soluble reactive phosphate (SRP) at which AP activity could be detected by ELF-97® were determined for Chaetoceros neogracile, Chlorella autotrophica, Isochrysis sp., Prorocentrum minimum, and Tetraselmis chui. Microalgal species differed significantly in the SRP concentration at which AP activity was first detectable (10.1–16.4 µM), well above concentrations normally considered limiting for phytoplankton. P. minimum began to express AP activity at a higher SRP concentration than the other algal species; this may be attributable to a relatively high DNA/cell ratio in P. minimum, compared to the other phytoplankton. Thus, phytoplankton species may respond to phosphorus deficiency at high SRP concentrations.  相似文献   

14.
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15.
The accuracies of three different evolutionary artificial neural network (ANN) approaches, ANN with genetic algorithm (ANN-GA), ANN with particle swarm optimization (ANN-PSO) and ANN with imperialist competitive algorithm (ANN-ICA), were compared in estimating groundwater levels (GWL) based on precipitation, evaporation and previous GWL data. The input combinations determined using auto-, partial auto- and cross-correlation analyses and tried for each model are: (i) GWL t?1 and GWL t?2; (ii) GWL t?1, GWL t?2 and P t ; (iii) GWL t?1, GWL t?2 and E t ; (iv) GWL t?1, GWL t?2, P t and E t ; (v) GWL t?1, GWL t?2 and P t?1 where GWL t , P t and E t indicate the GWL, precipitation and evaporation at time t, individually. The optimal ANN-GA, ANN-PSO and ANN-ICA models were obtained by trying various control parameters. The best accuracies of the ANN-GA, ANN-PSO and ANN-ICA models were obtained from input combination (i). The mean square error accuracies of the ANN-GA and ANN-ICA models were increased by 165 and 124% using ANN-PSO model. The results indicated that the ANN-PSO model performed better than the other models in modeling monthly groundwater levels.  相似文献   

16.
Detailed analyses were conducted of human impact on juniper forest landscapes occurring within the Zarafshan Range (Pamir-Alay). Juniperus seravschanica and J. semiglobosa belong to forest-forming species in Central Asia. At present, juniper forests all over Tajikistan are seriously threatened as a result of excessive logging and cattle grazing. The aim of this paper is to present juniper forest transformation as a result of human activities as well as the diversity of soil properties in the organic and humus horizons in the altitudinal system of soil zonation. Three groups of phytocoenoses were distinguished: those with a dominant share of Juniperus seravschanica; those with a dominant share of J. semiglobosa; and mixed. Associations with Juniperus seravschanica and J. semiglobosa feature several variants of phytocoenoses with dominant species: Artemisia lehmanniana, A. dracunculus, Eremurus olgae, Festuca sulcata, Ligularia thomsonii, Stipa turkestanica, Thymus seravschanicus, and Ziziphora pamiroalaica. The collected soil samples differ in their granulometric composition. Gravelly cobble fractions >2 mm are dominant; the share of sandy particles <2 mm is much lower (about 10–20%). Fraction 0.5–0.05 attains 35% on average. The Corg content of the soil varied from 0.26 to 11.40% in the humus horizon (A) and from 4.3 to 25% in the organic (O). Similar relationships were reported in the case of Ntot concentration. A clear relationship can be observed between concentrations of Corg and Ntot. Soil pH varied, ranging from very low acidic (pH 5.5) to neutral (pH 8.5). The content of available P varied; high concentrations were noted in organic (O) (40.46–211 mg kg?1) and mixed horizons (OA) (2.61–119 mg kg?1). Maximum accumulations of Pavail (1739.6 mg kg?1) and Ptot (9696 mg kg?1) were observed at a site heavily affected by intense grazing. Concentrations of Mgavail varied from 116 to 964 mg kg?1. Most of the analysed soil profiles lacked an organic horizon; only thin humus occurred.  相似文献   

17.
This paper examines the influence of porous media deformation on water-table wave dispersion in an unconfined aquifer using a numerical model which couples Richards’ equation to the poro-elastic model. The study was motivated by the findings of Shoushtari et al. (J Hydrol 533:412–440, 2016) who were unable to reproduce the observed wave dispersion in their sand flume data with either numerical Richards’ equation models (assuming rigid porous media) or existing analytic solutions. The water-table wave dispersion is quantified via the complex wave number extracted from the predicted amplitude and phase profiles. A sensitivity analysis was performed to establish the influence of the main parameters in the poro-elastic model, namely Young’s modulus (E) and Poisson’s ratio (ν). For a short oscillation period (T?=?16.4 s), the phase lag increase rate (k i) is sensitive to the chosen values of E and ν, demonstrating an inverse relationship with both parameters. Changes in the amplitude decay rate (k r), however, were negligible. For a longer oscillation period (T?=?908.6 s), variations in the values of E and ν resulted in only small changes in both k r and k i. In both the short and long period cases, the poro-elastic model is unable to reproduce the observed wave dispersion in the existing laboratory data. Hence porous media deformation cannot explain the additional energy dissipation in the laboratory data. Shoushtari SMH, Cartwright N, Perrochet P, Nielsen P (2016) The effects of oscillation period on groundwater wave dispersion in a sandy unconfined aquifer: sand flume experiments and modelling. J Hydrol 533:412–440.  相似文献   

18.
Antibiotic-resistant (pathogenic and non-pathogenic) organisms and genes are now acknowledged as significant emerging aquatic contaminants with potentially adverse human and ecological health impacts, and thus require monitoring. This study is the first to investigate levels of resistance among Irish groundwater (private wells) samples; Escherichia coli isolates were examined against a panel of commonly prescribed human and veterinary therapeutic antibiotics, followed by determination of the causative factors of resistance. Overall, 42 confirmed E. coli isolates were recovered from a groundwater-sampling cohort. Resistance to the human panel of antibiotics was moderate; nine (21.4%) E. coli isolates demonstrated resistance to one or more human antibiotics. Conversely, extremely high levels of resistance to veterinary antibiotics were found, with all isolates presenting resistance to one or more veterinary antibiotics. Particularly high levels of resistance (93%) were found with respect to the aminoglycoside class of antibiotics. Results of statistical analysis indicate a significant association between the presence of human (multiple) antibiotic resistance (p?=?0.002–0.011) and both septic tank density and the presence of vulnerable sub-populations (<5 years). For the veterinary antibiotics, results point to a significant relationship (p?=?<0.001) between livestock (cattle) density and the prevalence of multiple antibiotic resistant E. coli. Groundwater continues to be an important resource in Ireland, particularly in rural areas; thus, results of this preliminary study offer a valuable insight into the prevalence of antibiotic resistance in the hydrogeological environment and establish a need for further research with a larger geological diversity.  相似文献   

19.
Transmissivity (T) is one of the most important parameters in groundwater studies, and is generally estimated from pumping tests. T can also be deduced from abundantly available specific-capacity (Q/s) data by using analytical and/or empirical approaches, further upscaled by geostatistical methods. A different, remote sensing based, hydrogeomorphological approach is proposed, to upscale T from point- or well-scale to aquifer-scale, and it is applied to the piedmont alluvial aquifer system of Doon Valley in India. In the first step, Q/s and T data-pairs available from aquifer tests were used to establish an empirical, logarithmic relation. Subsequently, satellite imagery along with available data from published and unpublished maps, literature sources and ground surveys were used to divide the aquifer system into major hydrogeomorphological domains that control the groundwater occurrence and flow. Then, the T data derived from Q/s (using the empirical relation) and that available from pumping tests at well-scale were upscaled to aquifer-scale by averaging the T values within each hydrogeomorphological domain. Such a stratification approach is especially useful in areas where availability of only a few data-pairs of known Q/s and T limit the use of geostatistical techniques. A comparative study of the published empirical relations between Q/s and T in various hydrogeologic settings revealed that the relation obtained for Doon Valley aquifer system is close to that found for a similar alluvial aquifer system in Morocco.  相似文献   

20.
Stable isotope data of precipitation (δ18Op and deuterium excess), drip water (δ18Od), and modern calcite precipitates (δ18Oc and δ13Cc) from Yongxing Cave, central China, are presented, with monthly sampling intervals from June 2013 to September 2016. Moderate correlations between the monthly variation of δ18Op values (from ??11.5 to ??0.7‰) and precipitation amount (r = ??0.59, n?=?34, p?<?0.01) and deuterium excess (r?=?0.39, n?=?31, p?<?0.01) imply a combined effect of changes in precipitation amount and atmospheric circulation. At five drip sites, the δ18Od values have a much smaller variability (from ??9.1 to ??7.5‰), without seasonal signals, probably a consequence of the mixing in the karst reservoir with a deep aquifer. The mean δ18Od value (??8.4‰) for all drip waters is significantly more negative than the mean δ18Op value (??6.9‰) weighted by precipitation amount, but close to the wet season (May to September) mean value (??8.3‰), suggesting that a threshold of precipitation amount must be exceeded to provide recharge. Calculation based on the equilibrium fractionation factor indicates that the δ18Oc values are not in isotopic equilibrium with their corresponding drip waters, with a range of disequilibrium effects from 0.4 to 1.4‰. The δ18Oc and δ13Cc values generally increase progressively away from the locus of precipitation on glass plates. The disequilibrium effects in the cave are likely caused by progressive calcite precipitation and CO2 degassing related to a high gradient of CO2 concentration between drip waters and cave air. Our study provides an important reference to interpret δ18Oc records from the monsoon region of China.  相似文献   

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