共查询到20条相似文献,搜索用时 890 毫秒
1.
The EI-Dabaa area is located on the northwestern coastal zone of Egypt and is considered to be one of the most important regions for land reclamation and agriculture. In addition, it has been selected as a potential site for constructing Egypt's first nuclear power plant.In April 1989, 14 groundwater samples were collected from the area as well as collecting samples from the Mediterranean sea and from local rainwater. These samples were subjected to chemical and environmental isotope analyses. The results of the analyses for stable isotopes (oxygen-18 and deuterium) indicate that the main recharge source of the groundwater in El-Dabaa is the local precipitation during the rainy season. Variation of the environmental tritium content as well as in the chemical composition of both major cations (Na,K,Ca,Mg) and major anions (Cl,SO 4,HCO 3) between different groundwaters in the studied area reflect the high degree of inhomogeneity of the aquifer and different recharging conditions due to permeability of the water bearing formation.The chemical water type of the El-Dabaa groundwater is sodium sulphate (Na 2SO 4) and the SAR values illustrate the suitability of these groundwaters for agricultural purposes. 相似文献
2.
This study presents the groundwater quality assessment in the north of Isfahan, Iran. In the study area, assessment and measurement of groundwater hydrochemical parameters such as pH, total dissolved solids (TDS), electrical conductivity (EC), sodium absorption ratio (SAR), total hardness, major cations (K +, Na +, Ca 2+ and Mg 2+) and major anions (Cl ?, \({\text{HCO}}_{ 3}^{ - } ,{\text{CO}}_{3}^{2 - }\) and \({\text{SO}}_{4}^{2 - }\)) concentrations were performed. Accordingly, the 66 water samples from different locations were collected during April and May 2015. Water samples collected in the field were analyzed in the laboratory for cations and anions using the standard methods. In this research, the analytical results of physiochemical parameters of groundwater were compared with the standard guideline values as recommended by the world health organization (WHO) for drinking and public health purposes. The pH values of groundwater samples varied from 7.05 to 8.95 with a mean of 7.78, indicating a neutral to slightly alkaline water. TDS values showed that 14% of the samples exceeds the desirable limit given by WHO. EC values varied from 213 to 4320 µS/cm, while 23% of the samples were more than the standard limit. Gibbs diagram had shown that 90% of the samples in the study area fall in the rock weathering zone, and this means that chemical weathering of rock-forming minerals is the main factor controlling the water chemistry in the study area. Irrigation suitability and risk assessment of groundwater are evaluated by measuring EC, %Na, SAR and RSC. According to the dominant cations and anions, five types of water were identified in the water samples: Ca-HCO 3, Ca-SO 4, Na-Cl, Na-HCO 3 and Na-SO 4. The results show that the majority of samples (30 samples, 45%) belongs to the mixed Na-SO 4 water type. Correlation analysis and principal component analysis was used to identify the relationship between ions and physicochemical parameters. Results indicated that 18 stations of the study area had the best quality and can be used for irrigation and drinking purposes in the future. 相似文献
3.
The gametogenic periodicity of the cold seep mussel “ Bathymodiolus” childressi was analysed from a time series of samples from depths of ∼ 650 m surrounding the Brine Pool cold seep on the continental
slope of the northern Gulf of Mexico. Occasional samples were retrieved from Bush Hill and GC 234 for comparison. At the Brine
Pool, both females and males showed strong reproductive periodicity with the initiation of gametogenesis from December to
March, followed by a period of gamete growth or proliferation and spawning from October to February. Gametogenesis was synchronized
at all three sites. Gametogenic periodicity appears to be correlated with surface production that peaks during the winter
months. Downward flux of detritus during this period may provide food for the planktotrophic larvae and also supplementary
nutrition for the adult, which has chemosynthetic bacterial symbionts but is also capable of filter feeding. Individuals in
all three populations carried parasites and these were especially common at Bush Hill and GC234, where it is suggested they
have a major impact on reproductive output. 相似文献
4.
The Faminin area in the semi-arid Hamadan state, western Iran is facing a serious deficiency in groundwater resources due
to an increasing demand associated with rapid population growth and agricultural development. The chemical composition of
78 well samples throughout the Faminin area was determined with the aim of evaluating the concentration of the background
ions and identifying the major hydrogeochemical processes that control the groundwater chemistry. The similarity between rock
and groundwater chemistries in the recharge area indicates a significant rock-water interaction. The hydrochemical types Na–HCO 3 and Na–SO 4 are the predominate forms in the groundwater, followed by water types Ca–HCO 3 and Na–Cl. The high values of electrical conductivity and high concentrations of Na +, Cl −, SO 42− and NO 3− in the groundwater appeared to be caused by the dissolution of mineral phases and would appeared to be caused by anthropogenic
activities, such as intense agricultural practices (application of fertilizers, irrigation practice), urban and industrial
waste discharge, among others. 相似文献
5.
Groundwater quality of the Banana Plain (Mbanga, Njombe, Penja—Cameroon) was assessed for its suitability for drinking, domestic,
and agricultural uses. A total of 67 groundwater samples were collected from open wells, springs, and boreholes. Samples were
analyzed for physicochemical properties, major ions, and dissolved silica. In 95% of groundwater samples, calcium is the dominant
cation, while sodium dominates in 5% of the samples. Eighty percent of the samples have HCO 3 as major anion, and in 20%, NO 3 is the major anion. Main water types in the study area are CaHCO 3, CaMgHCO 3, CaNaHCO 3, and CaNaNO 3ClHCO 3. CO 2-driven weathering of silicate minerals followed by cation exchange seemingly controls largely the concentrations of major
ions in the groundwaters of this area. Nitrate, sulfate, and chloride concentrations strongly express the impact of anthropogenic
activities (agriculture and domestic activities) on groundwater quality. Sixty-four percent of the waters have nitrate concentrations
higher than the drinking water limit. Also limiting groundwater use for potable and domestic purposes are contents of Ca 2+, Mg 2+ and HCO 3
− and total hardness (TH) that exceed World Health Organization (WHO) standards. Irrigational suitability of groundwaters in
the study area was also evaluated, and results show that all the samples are fit for irrigation. Groundwater quality in the
Banana Plain is impeded by natural geology and anthropogenic activities, and proper groundwater management strategies are
necessary to protect sustainably this valuable resource. 相似文献
6.
Understanding the mechanism of arsenic (As) mobilization from sediments to groundwater is important for water quality management
in areas of endemic arsenic poisoning, such as the Datong basin in northern China. The bulk geochemistry analysis of sediment
samples from three 50-m boreholes drilled specifically for this study at As-contaminated aquifers, the groundwaters of which
have an As concentration up to 1060 μg/l, revealed that the average bulk concentrations of major and trace elements of the
samples are similar to those of the average upper continental crust. The average As content of the sediment samples (18.7 mg/kg)
is higher than that of modern unconsolidated sediments (5–10 mg/kg). Moreover, the abundance of elements varied with grain
size, with higher concentrations in finer fractions of the sediments, such as silt and clay. The concentration of NH 2OH–HCl-extracted iron (Fe) strongly correlated with that of extracted As, suggesting that Fe oxyhydroxides may be the major
sink of As in the aquifer. The results of microcosm experiments showed that As mobilization from sediments to groundwater
is probably mainly related to changes in the redox conditions, with moderately reducing conditions being favorable for As
release from sediments into groundwater. 相似文献
7.
The groundwater samples collected from the shallow and deep groundwater aquifers of an industrial area of the Kanpur city (Uttar Pradesh, India) were analyzed for the concentration levels and distribution pattern of nitrogenous species, such as nitrate-nitrogen (NO 3-N), nitrite-nitrogen (NO 2-N), ammonical-nitrogen (NH 4-N), organic-nitrogen (Org-N) and total Kjeldahl-nitrogen (TKN) to identify the possible contamination source. Geo-statistical approach was adopted to determine the distribution and extent of the contaminant plume. In the groundwater aquifers NO 3-N, NO 2-N, NH 4-N, TKN, Org-N and Total-N ranged from 0.10 to 64.10, BDL (below detection limit)-6.57, BDL-39.00, 7.84–202.16, 1.39–198.97 and 8.89–219.43 mg l −1, respectively. About 42% and 26% of the groundwater samples of the shallow and deep groundwater aquifers, respectively, exceeded the BIS (Bureau of Indian Standards) guideline value of 10 mg l −1 for NO 3-N and may pose serious health hazards to the people of the area. The results of the study revealed that the groundwater aquifers of the study area are highly contaminated with the nitrate and indicates point source pollution of nitrate in the study area. 相似文献
8.
Arsenic contamination in groundwater is of increasing concern because of its high toxicity and widespread occurrence. This
study is an effort to trace the factors responsible for arsenic enrichment in groundwater of the middle Gangetic Plain of
India through major ion chemistry, arsenic speciation, sediment grain-size analyses, and multivariate statistical techniques.
The study focuses on the distinction between the contributions of natural weathering and anthropogenic inputs of arsenic with
its spatial distribution and seasonal variations in the plain of the state Bihar of India. Thirty-six groundwater and one
sediment core samples were collected in the pre-monsoon and post-monsoon seasons. Various graphical plots and statistical
analysis were carried out using chemical data to enable hydrochemical evaluation of the aquifer system based on the ionic
constituents, water types, hydrochemical facies, and factors controlling groundwater quality. Results suggest that the groundwater
is characterized by slightly alkaline pH with moderate to strong reducing nature. The general trend of various ions was found
to be Ca 2+ > Na + > Mg 2+ > K + > NH 4
+; and HCO 3
− > Cl − > SO 4
2− > NO 3
− > PO 4
3− > F − in both seasons. Spatial and temporal variations showed a slightly higher arsenic concentration in the pre-monsoon period
(118 μg/L) than in the post-monsoon period (114 μg/L). Results of correlation analyses indicate that arsenic contamination
is strongly associated with high concentrations of Fe, PO 4
3−, and NH 4
+ but relatively low Mn concentrations. Further, the enrichment of arsenic is more prevalent in the proximity of the Ganges
River, indicating that fluvial input is the main source of arsenic. Grain size analyses of sediment core samples revealed
clay (fine-grained) strata between 4.5 and 7.5 m deep that govern the vertical distribution of arsenic. The weathering of
carbonate and silicate minerals along with surface-groundwater interactions, ion exchange, and anthropogenic activities seem
to be the processes governing groundwater contamination, including with arsenic. Although the percentage of wells exceeding
the permissible limit (50 μg/L) was less (47%) than that reported in Bangladesh and West Bengal, the percentage contribution
of toxic As(III) to total arsenic concentration is quite high (66%). This study is vital considering that groundwater is the
exclusive source of drinking water in the region and not only makes situation alarming but also calls for immediate attention. 相似文献
9.
In Tunisia, the water resources are limited, partially renewable and unequally distributed between the wet north and the dry south of the country. The Sminja aquifer in Zaghouan city is located in north-east of Tunisia, between latitudes 36°38′ and 36°47′ and longitudes 9°95′ and 10°12′. This aquifer is used to satisfy the population needs for their domestic purposes and agricultural activities. Water analyses results are expressed by many methods, among which are geochemical methods combined with the geographic information system (GIS) (all schematic presentations of the diagram software (Piper, Riverside, Wilcox…), which can be used to assess the suitability of the Sminja aquifer groundwater for human consumption and irrigation purposes. A total of 23 wells were sampled in January 2013, and the concentrations of major cations (Na +, Ca 2+, Mg 2+ and K +), major anions (Cl ?, SO 4 2? and HCO 3 ?), electrical conductivity and total dissolved solids were analysed. In the Sminja groundwater, the order of the cations dominance was Na > Ca > Mg > K and that of the anions was Cl > HCO 3 > SO 4. All of the analysed samples of the study area exceed chemical values recommended by the World Health Organisation guidelines and Tunisian Standards (NT.09.14) for potability but with different percentages. The aquifer spatial distribution of saturation indices reveals that all groundwater samples are under-saturated with gypsum, halite and anhydrite and are over-saturated with respect to calcite and dolomite based on water quality evaluation parameters for irrigation purposes; here, 87 % of samples in Sminja aquifer groundwater are suitable, whereas 13 % are unsuitable for irrigation uses. 相似文献
10.
This study attempts to address the processes controlling the chemical composition of the Kavaratti aquifer system of Lakshadweep Island in India. Major ions and other physico-chemical parameters were determined for the premonsoon period in the Kavaratti of the Lakshadweep Island system. The trilinear diagram confirms the ingress of sea water into the shallow lens of freshwater in the islands by the changing water types. The abundance of major cations varied in the order Na>Ca>Mg>K and anions in the order Cl>HCO 3>SO 4. The ionic relations suggest that the higher concentration Na and Cl are the results of ion exchange and evaporation. The plots of data on the Gibbs diagram suggest that chemical weathering of rock-forming minerals and evaporation are the dominant factors controlling groundwater chemistry in the area. The hydrochemistry concept was deduced by the multivariate analysis for better understanding on the dynamic and complexity of the groundwater chemical processes. By the multivariate analytical techniques, the samples were grouped into two: one with saline water dominance and the other with freshwater characteristics. Thus proper management of these aquifers should be assured to retain their freshwater yield in the future. 相似文献
11.
Chattonella marina, a raphidophycean flagellate, is a highly toxic red tide phytoplankton which causes severe damage to fish farming. Recent
studies demonstrated that Chattonella spp. continuously release superoxide anions (O 2
−) while they are living. Heterosigma akashiwo, another raphidophycean flagellate, also produces O 2
−. In the present study, we found that lectins such as concanavalin A (Con A), wheat germ agglutinin (WGA), and castor bean
hemagglutinin (CBH) stimulated C. marina and H. akashiwo to generate enhanced amounts of O 2
− in a concentration-dependent manner. The lectin-specific sugars potently inhibited the lectin-induced increase of O 2
− production, suggesting that the effects of lectins are mediated mainly through the interaction of these lectins with carbohydrate
moiety present on the flagellate cell surface. In contrast to the potent ability of native Con A (tetravalent), succinylated
Con A (divalent) showed only a slight stimulative effect on these flagellates. O 2
− production was totally inhibited by treatment with proteinase K for 30 min, without affecting the viabilities of flagellates.
These results suggest that cell-surface redox enzymes may be involved in O 2
− production, and such enzymes are responsible for the lectin-stimulation.
Received: 21 August 1997 / Accepted: 8 January 1998 相似文献
12.
Uranium is a radioactive element normally present in hexavalent form as U(VI) in solution and elevated levels in drinking water cause health hazards. Representative groundwater samples were collected from different litho-units in this region and were analyzed for total U and major and minor ions. Results indicate that the highest U concentration (113 µg l ?1) was found in granitic terrains of this region and about 10 % of the samples exceed the permissible limit for drinking water. Among different species of U in aqueous media, carbonate complexes [UO 2(CO 3) 2 2? ] are found to be dominant. Groundwater with higher U has higher pCO 2 values, indicating weathering by bicarbonate ions resulting in preferential mobilization of U in groundwater. The major minerals uraninite and coffinite were found to be supersaturated and are likely to control the distribution of U in the study area. Nature of U in groundwater, the effects of lithology on hydrochemistry and factors controlling its distribution in hard rock aquifers of Madurai district are highlighted in this paper. 相似文献
13.
Groundwater, accessed using wells and municipal springs, represents the major source of potable water for the human population
outside of major urban areas in northwestern Romania, a region with a long history of metal mining and metallurgy. The magnitude
and spatial distribution of metal contamination in private-supply groundwater was investigated in four mining-affected river
catchments in Maramureş and Satu Mare Counties through the collection of 144 groundwater samples. Bedrock geology, pH and
Eh were found to be important controls on the solubility of metals in groundwater. Peak metal concentrations were found to
occur in the Lapuş catchment, where metal levels exceed Dutch target and intervention values in up to 49% and 14% of samples,
respectively. A 700 m wide corridor in the Lapuş catchment on either side of the main river channel was identified in which
peak Cd (31 μg l −1), Cu (50 μg l −1), Pb (50 μg l −1) and Zn (3,000 μg l −1) concentrations were found to occur. Given the generally similar bedrock geologies, lower metal levels in other catchments
are believed to reflect differences in the magnitude of metal loading to the local environment from both metal mining and
other industrial and municipal sources. Sampling of groundwater in northwestern Romania has indicated areas of potential concern
for human health, where heavy metal concentrations exceed accepted environmental quality guidelines. The presence of elevated
metal levels in groundwater also has implications for the implementation of the EU Water Framework Directive (WFD) and achieving
‘good’ status for groundwater in this part of the Danube River Basin District (RBD). 相似文献
14.
Bedrock groundwaters in Geumsan County, Korea, were surveyed to investigate the distribution and geochemical behaviors of arsenic and fluoride, mobilized through geogenic processes. The concentrations were enriched up to 113 μg/L for arsenic and 7.54 mg/L for fluoride, and 16% of 150 samples exceeded World Health Organization drinking water guidelines for each element. Simple Ca-HCO3 groundwater types and positive correlations with pH, Ca, SO4, and HCO3 were characteristics of high (>10 μg/L) As groundwaters. The oxidation reaction of sulfide minerals in metasedimentary rocks and locally mineralized zones seems to be ultimately responsible for the existence of arsenic in groundwater. Desorption process under high pH conditions may also control the arsenic mobility in the study area. High (>1.5 mg/L) F groundwaters were found in the Na-HCO3 type and with greater depth. Fluoride seemed to be enriched by deep groundwater interaction with granitic rocks, and continuous supply to shallow Ca-HCO3-type groundwater kept the concentration high. In the study area, drinking water management should include periodic As and F monitoring in groundwater. 相似文献
15.
Leachates from the El Fraile tailings impoundment (Taxco, Mexico) were monitored every 2 months from October 2001 to August 2002 to assess the geochemical characteristics. These leachates are of interest because they are sometimes used as alternative sources of domestic water. Alternatively, they drain into the Cacalotenango creek and may represent a major source of metal contamination of surface water and sediments. Most El Fraile leachates show characteristics of Ca–SO 4, (Ca+Mg)–SO 4, Mg–SO 4 and Ca–(SO 4+HCO 3) water types and are near-neutral (pH=6.3–7.7). Some acid leachates are generated by the interaction of meteoric water with tailings during rainfall events (pH=2.4–2.5). These contain variable levels of SO 4
2− (280–29,500 mg l −1) and As (<0.01–12.0 mg l −1) as well as Fe (0.025–2352 mg l −1), Mn (0.1–732 mg l −1), Zn (<0.025–1465 mg l −1) and Pb (<0.01–0.351 mg l −1). Most samples show the highest metal enrichment during the dry seasons. Leachates used as domestic water typically exceed the Mexican Drinking Water Guidelines for sulfate, hardness, Fe, Mn, Pb and As, while acidic leachates exceed the Mexican Guidelines for Industrial Discharge Waters for pH, Cu, Cd and As. Speciation shows that in near-neutral solutions, metals exist mainly as free ions, sulfates and bicarbonates, while in acidic leachates they are present as sulfates and free ions. Arsenic appears as As (V) in all samples. Thermodynamic and mineralogical evidence indicates that precipitation of Fe oxides and oxyhydroxides, clay minerals and jarosite as well as sorption by these minerals are the main processes controlling leachate chemistry. These processes occur mainly after neutralization by interaction with bedrock and equilibration with atmospheric oxygen. 相似文献
16.
为弄清大同盆地地下水中影响砷的迁移、富集的主要地球化学与生物地球化学过程,为区域供水安全提供指导作用,针对高砷地下水系统开展了水文地球化学与含水层沉积物全岩地球化学研究;并在此基础上探讨了研究区高砷地下水成因。结果表明,研究区高砷地下水为偏碱性、强还原环境,砷含量为0.31~452μg·L-1,主要以砷酸盐形式存在,地下水中砷与三价铁的浓度有显著的相关性。高砷含水层沉积物中有机质、铁与砷含量表现出显著相关性。以上结果说明,碱性还原环境有利于地下水中砷的富集;微生物参与下,沉积物相有机质的氧化和Fe氧化物/氢氧化物的还原过程是本区高砷地下水形成的主控因素。 相似文献
17.
A field method is reported for the speciation of arsenic in water samples that is simple, rapid, safe to use beyond laboratory
environments, and cost effective. The method utilises solid-phase extraction cartridges (SPE) in series for selective retention
of arsenic species, followed by elution and measurement of eluted fractions by inductively coupled plasma mass spectrometry
(ICP-MS) for “total” arsenic. The method is suitable for on-site separation and preservation of arsenic species from water.
Mean percentage accuracies ( n = 25) for synthetic solutions of arsenite (As III), arsenate (As V), monomethylarsonic acid (MA), and dimethylarsinic acid (DMA) containing 10 μg l −1 As, were 98, 101, 94, and 105%, respectively. Data are presented to demonstrate the effect of pH and competing anions on
the retention of the arsenic species. The cartridges were tested in the UK and Argentina at sites where arsenic was known
to be present in surface and groundwaters, respectively, at elevated concentrations and under challenging matrix conditions.
In Argentinean groundwater, 4–20% of speciated arsenic was present as MA and 20–73% as As III. In UK surface waters, speciated arsenic was measured as 7–49% MA and 12–42% DMA. Comparative data from the field method
using SPE cartridges and the laboratory method using liquid chromatography coupled to ICP-MS for all water samples provided
a correlation of greater than 0.999 for As III and DMA, 0.991 for MA, and 0.982 for As V ( P < 0.01). 相似文献
18.
The objective of this document is to report on the early success for sequestering 129I. Sorption coefficients ( K
d) for I − and IO 3
− onto delafossites, spinels and layered metal hydroxides were measured and compared for their applicability to sequester 129I. The studies were performed using a dilute fluid composition representative of groundwater indigenous to the Yucca mountain
area. Delafossites generally exhibited relatively poor sorption coefficients (<35 mL/g). In contrast, the composition of the
layered hydroxides significantly affects their ability to sorb I. Cu/Al and Cu/Cr layered hydroxide samples exhibit K
d’s greater than 1000 mL/g for both I − and IO 3
−. 相似文献
19.
In May and September, 2002, 14 private residential drinking water wells, one dewatering well at a lignite mine, eight surface
water sites, and lignite from an active coal mine were sampled in five Parishes of northwestern Louisiana, USA. Using a geographic
information system (GIS), wells were selected that were likely to draw water that had been in contact with lignite; control
wells were located in areas devoid of lignite deposits. Well water samples were analyzed for pH, conductivity, organic compounds,
and nutrient and anion concentrations. All samples were further tested for presence of fungi (cultures maintained for up to
28 days and colonies counted and identified microscopically) and for metal and trace element concentration by inductively-coupled
plasma mass spectrometry and atomic emission spectrometry. Surface water samples were tested for dissolved oxygen and presence
of pathogenic leptospiral bacteria. The Spearman correlation method was used to assess the association between the endpoints
for these field/laboratory analyses and incidence of cancer of the renal pelvis (RPC) based on data obtained from the Louisiana
Tumor Registry for the five Parishes included in the study. Significant associations were revealed between the cancer rate
and the presence in drinking water of organic compounds, the fungi Zygomycetes, the nutrients PO 4 and NH 3, and 13 chemical elements. Presence of human pathogenic leptospires was detected in four out of eight (50%) of the surface
water sites sampled. The present study of a stable rural population examined possible linkages between aquifers containing
chemically reactive lignite deposits, hydrologic conditions favorable to the␣leaching and transport of toxic organic compounds
from the lignite into the groundwater, possible microbial contamination, and RPC risk. 相似文献
20.
During the 2010/2011 Exploration vessel Nautilus expedition to the Mediterranean Sea, samples of Lamellibrachia (Siboglinidae, Annelida) were imaged in situ and collected from hydrothermal vent and methane “cold seeps.” An analysis of these Lamellibrachia and their endosymbiotic thioautotrophic gammaproteobacteria reveals two distinct endosymbiont phylotypes. Phylotype 1 was present in Lamellibrachia specimens from 947 m at the Eratosthenes seamount seep (a seep off Cyprus in the Eastern Mediterranean), and Phylotype 2 was found in siboglinids from 618 m at a hydrothermal vent within Palinuro volcanic complex in Tyrrhenian Sea. Both phylotypes coexist in siboglinids at 1,036 m from the Palmachim disturbance, a cold seep in the Eastern Mediterranean’s Levantine basin. Our results, combined with existing knowledge of siboglinid host and endosymbiotic bacteria biogeography, reveal that two major groups of endosymbionts coexist within lamellibranchids and escarpids. The phylogenetic clustering of these bacteria is primarily influenced by geographic location, rather than selection by the siboglinid host. 相似文献
|