Water Chloride Concentrations Research Articles

Vertical migration of leachate pollutants in clayey soils beneath an uncontrolled landfill at Huainan, China: A field and theoretical investigation

To assess the extent of leachate migration, continuous samples of clayey soils (about 9m) were obtained beneath a 17-year old uncontrolled landfill in southeastern China. The soil samples were sub sectioned and analyzed to determine the concentrations of chloride, sodium and COD in the pore water. Total nitrogen and soil organic matter content of the soil samples were also determined. Leachate-derived chloride was detected in the clayey soil to a maximum depth of 9m. Sodium and COD were found to migrate into the soils to depths of 3–4m due to the attenuation of solutes by the soil organic matter and clay minerals at the shallow soils. The estimated migration depths for the chloride are 3m in the case of pure diffusion. Advection and mechanical dispersion were found to be more important than molecular diffusion for this site with an 8m high leachate mound. By comparing the results obtained by the mathematical modeling for layered advection–dispersion problem with the measured concentration profiles, the ranges of the effective diffusion coefficient, retardation factor and dispersivity of the soils were estimated. Better fits are obtained by employing an artificial effective interface about 1m above the observed interface. The clayey soils showed a relatively high attenuation capacity for COD with the estimated retardation factor of 5.

Monitoring of chloride concentration in ground water of Sekket and Thomina areas, Misurata, Libya: correlation with some physical Parameters

Monitoring of chloride concentration in ground water of Sekket and Thomina areas, Misurata, Libya: correlation with some physical Parameters

Palaeohydrogeological insights from natural tracer profiles in aquitard porewater, Great Artesian Basin, Australia

The value of using environmental tracer profiles in aquitards to quantify fluid flux and to reveal information about palaeohydrology is largely unknown for parts of the world that were not glaciated during the Cenozoic. We present deep, continuous vertical profiles of aquitard pore water chloride concentration and δ2H/δ18O composition from the western margin of the Great Artesian Basin, Australia, where upward leakage is the dominant groundwater discharge mechanism. At the deeper of the two sites studied, the Cl− and δ2H profiles exhibit a distinctive S‐shape, which we interpret as a shift in the upper concentration boundary condition over time. Numerical simulations are used to support an hypothesis that the shallow phreatic aquifer was more saline and more enriched in δ2H compared to current conditions prior to ∼120 ka, followed by an extended freshening phase from ∼120 to 20 ka, then a saline phase similar to current conditions for the last ∼20 ka. These timeframes correspond favorably with results of previous studies into the palaeohydrology of nearby playa Lake Eyre. At the shallower site, the tracer profiles decrease exponentially with depth. We explore several models for the evolution of these profiles and adopt one of long‐term salt input at ground surface. At both sites, tracer concentrations for groundwater sampled from the underlying artesian aquifer provide conclusive evidence that recharge occurred within the last 10–20 ka. Chloride was a more useful tracer than δ2H in this study, primarily due to lack of recent glaciation in central Australia to provide a dynamic δ2H tracer signal.

Effects of Road Salt on Connecticut's Groundwater: A Statewide Centennial Perspective

This study examined the extent to which development and road salting has affected Connecticut's groundwater. We gathered water quality data from different time periods between 1894 and the present and analyzed the data using maps generated with ESRI ArcGIS. Historical reports illustrate a statewide baseline trend of decreasing chloride concentration northward across the State (average, 2 ppm). Since then, statewide chloride concentrations in ground water have increased by more than an order of magnitude on average. Analysis indicates spatial correlation between chloride impacts and major roadways. Furthermore, increases in statewide chloride concentration parallel increases in road salt application. Projected trends suggest that statewide baseline concentrations will increase by an amount equal to five times background levels between the present and the year 2030. The analytical process outlined herein can be readily applied to any region to investigate salt impacts on large spatial and temporal scales.

Desiccation-crack-induced salinization in deep clay sediment

Abstract. A study on water infiltration and solute transport in a clayey vadose zone underlying a dairy farm waste source was conducted to assess the impact of desiccation cracks on subsurface evaporation and salinization. The study is based on five years of continuous measurements of the temporal variation in the vadose zone water content and on the chemical and isotopic composition of the sediment and pore water in it. The isotopic composition of water stable isotopes (δ18O and δ2H) in water and sediment samples, from the area where desiccation crack networks prevail, indicated subsurface evaporation down to ~ 3.5 m below land surface, and vertical and lateral preferential transport of water, following erratic preferential infiltration events. Chloride (Cl−) concentrations in the vadose zone pore water substantially increased with depth, evidence of deep subsurface evaporation and down flushing of concentrated solutions from the evaporation zones during preferential infiltration events. These observations led to development of a desiccation-crack-induced salinization (DCIS) conceptual model. DCIS suggests that thermally driven convective air flow in the desiccation cracks induces evaporation and salinization in relatively deep sections of the subsurface. This conceptual model supports previous conceptual models on vadose zone and groundwater salinization in fractured rock in arid environments and extends its validity to clayey soils in semi-arid environments.

Changes in riverine benthic diatom community structure along a chloride gradient

The application of salt is the primary means of deicing roads and highways in colder regions of north-eastern North America. This has increased the chloride concentrations of many lake and stream ecosystems. While this salinization has been documented, less is known about how increased salinity alters benthic communities in downstream ecosystems. Natural thresholds, at which there are large scale changes in community composition, have not yet been established for many types of contaminants, including chloride. The diatom community, which is sensitive to small changes in the ambient environment, has the potential to be a strong indicator of salinization effects on stream ecosystems. In this study, we sampled diatom communities in 41 streams across a salinity gradient throughout south central Ontario, Canada. We sampled benthic diatom assemblages in early May following complete snowmelt, when stream water chloride concentrations ranged from 5 to 502mg/L. Based on redundancy analysis, we confirmed a strong association between the species composition of the diatom community and water conductivity, a commonly used index of stream salinity. Taxa indicator threshold analyses (TITAN) indicated the community changed substantially at chloride concentrations greater than 35mg/L. We also found that, an indicator taxa, Meridion circulare, was extremely sensitive to high concentrations of salt and negatively correlated with chloride. In a wide synoptic survey of streams of our region, we found that streams in most developed watersheds exceed tolerance thresholds for benthic diatom communities. This work suggests that current chloride concentrations in urban watersheds are greatly exceeding the benthic community thresholds, for which improved management and regulatory practices are needed. Salinization thus appears to be an important feature of urban streams and needs to be considered as an important ecological driver in future studies.

Numerical modelling of seawater intrusion in Shenzhen (China) using a 3D density-dependent model including tidal effects

During the 1990s, groundwater overexploitation has resulted in seawater intrusion in the coastal aquifer of the Shenzhen city, China. Although water supply facilities have been improved and alleviated seawater intrusion in recent years, groundwater overexploitation is still of great concern in some local areas. In this work we present a three-dimensional density-dependent numerical model developed with the FEFLOW code, which is aimed at simulating the extent of seawater intrusion while including tidal effects and different groundwater pumping scenarios. Model calibration, using waterheads and reported chloride concentration, has been performed based on the data from 14 boreholes, which were monitored from May 2008 to December 2009. A fairly good fitness between the observed and computed values was obtained by a manual trial-and-error method. Model prediction has been carried out forward 3 years with the calibrated model taking into account high, medium and low tide levels and different groundwater exploitation schemes. The model results show that tide-induced seawater intrusion significantly affects the groundwater levels and concentrations near the estuarine of the Dasha river, which implies that an important hydraulic connection exists between this river and groundwater, even considering that some anti-seepage measures were taken in the river bed. Two pumping scenarios were considered in the calibrated model in order to predict the future changes in the water levels and chloride concentration. The numerical results reveal a decreased tendency of seawater intrusion if groundwater exploitation does not reach an upper bound of about 1.32 × 104 m3/d. The model results provide also insights for controlling seawater intrusion in such coastal aquifer systems.

Effects of a long term water level reduction on the ecology and water quality in an eastern Mediterranean lake

Water level fluctuations play a significant role in the lake nutrient dynamics, and consequently may have a strong influence on the biological communities and productivity. In this article we investigated the effects of a long term water level reduction on key chemistry parameters and major biological communities in an eastern Mediterranean lake. Our approach is based on temporal data regarding water quality, fish, zooplankton and aquatic vegetation that are representative of different water level periods. The results revealed significant correlations between water level, conductivity and chloride concentration suggesting a clear effect of the water level reduction on the water quality. Among the key findings of this study is the significant increase of zoobenthivorous fish (roach and carp) from 1973 to 1999 that correlates with the water level reduction. A decline of charophytes is also noted whereas the reed beds appear to have expanded at the shallower parts of the lake. The zooplankton composition of the lake is mostly dominated by nauplii, rotifer and small-sized crustaceans indicating a possible effect of fish predation. Overall, this article has ascertained an alarming shift of water quality and composition of biological communities that can be attributed to the combined effects of eutrophication and the extreme water level decrease.

The role of recharge and evapotranspiration as hydraulic drivers of ion concentrations in shallow groundwater on Everglades tree islands, Florida (USA)

Recently, evapotranspiration has been hypothesized to promote the secondary formation of calcium carbonate year-round on tree islands in the Everglades by influencing groundwater ions concentrations. However, the role of recharge and evapotranspiration as drivers of shallow groundwater ion accumulation has not been investigated. The goal of this study is to develop a hydrologic model that predicts the chloride concentrations of shallow tree island groundwater and to determine the influence of overlying biomass and underlying geologic material on these concentrations. Groundwater and surface water levels and chloride concentrations were monitored on eight constructed tree islands at the Loxahatchee Impoundment Landscape Assessment (LILA) from 2007 to 2010. The tree islands at LILA were constructed predominately of peat, or of peat and limestone, and were planted with saplings of native tree species in 2006 and 2007. The model predicted low shallow groundwater chloride concentrations when inputs of regional groundwater and evapotranspiration-to-recharge rates were elevated, while low evapotranspiration-to-recharge rates resulted in a substantial increase of the chloride concentrations of the shallow groundwater. Modeling results indicated that evapotranspiration typically exceeded recharge on the older tree islands and those with a limestone lithology, which resulted in greater inputs of regional groundwater. A sensitivity analysis indicated the shallow groundwater chloride concentrations were most sensitive to alterations in specific yield during the wet season and hydraulic conductivity in the dry season. In conclusion, the inputs of rainfall, underlying hydrologic properties of tree islands sediments and forest structure may explain the variation in ion concentration seen across Everglades tree islands. Copyright © 2012 John Wiley & Sons, Ltd.

Quantifying the effects of stream channels on storm water quality in a semi-arid urban environment

Summary Stormwater drainage systems can have a large effect on urban runoff quality, but it is unclear how ephemeral urban streams alter runoff hydrochemistry. This problem is particularly relevant in semi-arid regions, where urban storm runoff is considered a renewable water resource. Here we address the question: how do stream channels alter urban runoff hydrochemistry? We collected synoptic stormwater samples during three rainfall–runoff events from nine ephemeral streams reaches (three concrete or metal, three grass, three gravel) in Tucson, Arizona. We identified patterns of temporal and spatial (longitudinal) variability in concentrations of conservative (chloride and isotopes of water) and reactive solutes (inorganic-N, soluble reactive phosphorous, sulfate-S, dissolved organic carbon (DOC) and nitrogen, and fecal indicator bacteria). Water isotopes and chloride (Cl) concentrations indicate that solute flushing and evapoconcentration alter temporal patterns in runoff hydrochemistry, but not spatial hydrochemical responses. Solute concentrations and stream channel solute sourcing and retention during runoff were significantly more variable at the grass reaches (CV = 2.3 − 144%) than at the concrete or metal (CV = 1.6 − 107%) or gravel reaches (CV = 1.9 − 60%), which functioned like flow-through systems. Stream channel soil Cl and DOC decreased following a runoff event (Cl: 12.1–7.3 μg g −1 soil; DOC: 87.7–30.1 μg g −1 soil), while soil fecal indicator bacteria counts increased (55–215 CFU g −1 soil). Finding from this study suggest that the characteristics of the ephemeral stream channel substrate control biogeochemical reactions between runoff events, which alter stream channel soil solute stores and the hydrochemistry of subsequent runoff events.

Linear and non-linear chemometric modeling of THM formation in Barcelona's water treatment plant

The complex behavior observed for the dependence of trihalomethane formation on forty one water treatment plant (WTP) operational variables is investigated by means of linear and non-linear regression methods, including kernel-partial least squares (K-PLS), and support vector machine regression (SVR). Lower prediction errors of total trihalomethane concentrations (lower than 14% for external validation samples) were obtained when these two methods were applied in comparison to when linear regression methods were applied. A new visualization technique revealed the complex nonlinear relationships among the operational variables and displayed the existing correlations between input variables and the kernel matrix on one side and the support vectors on the other side. Whereas some water treatment plant variables like river water TOC and chloride concentrations, and breakpoint chlorination were not considered to be significant due to the multi-collinear effect in straight linear regression modeling methods, they were now confirmed to be significant using K-PLS and SVR non-linear modeling regression methods, proving the better performance of these methods for the prediction of complex formation of trihalomethanes in water disinfection plants.

Comparative Study on Water Aging of Rubber Asphalt and TOR Rubber Asphat

Brookfield Viscometer, Dynamic Shear Rheometer (DSR) and Bending Beam Rheometer (BBR) are employed to analyze properties of rubber asphalt and TOR rubber asphalt after water aging. Through simulating, the influences of parameter changes of water on the performances of asphalts after aging were studied. The results show that the PH value and sodium chloride content of water affects the aging properties of asphalt, and as the parameter changes, the high temperature performance of TOR rubber asphalt are better than rubber asphalt. DSR and BBR tests reveal that the higher the acidity (or the lower PH value) and the sodium chloride content of water are, the more seriously rubber asphalt and TOR rubber asphalt age in water aging; the lower the temperature is, the larger the S value and the smaller the m value become, and the worse the low temperature performance and dissipation of temperature stress of rubber asphalt and TOR rubber asphalt get.

Fluoride bioaccumulation in the signal crayfish Pacifastacus leniusculus (Dana) as suitable bioindicator of fluoride pollution in freshwater ecosystems

Fluoride bioaccumulation in the signal crayfish Pacifastacus leniusculus (Dana) was examined through field and laboratory studies, considering in the latter the effects of several biotic and abiotic factors: water chloride content, developmental stage, sex, and tissue. The potential use of P. leniusculus as bioindicator of fluoride pollution in freshwater ecosystems was also assessed by testing the capability of juvenile crayfish to release fluoride during depuration periods. After discussing the obtained results, we concluded that: (1) fluoride pollution by industrial effluents may significantly increase the fluoride content in signal crayfish inhabiting polluted freshwater ecosystems; (2) although high chloride levels in the aquatic medium may significantly reduce the fluoride content in signal crayfish exposed to fluoride pollution conditions, fluoride bioaccumulation can still occur in significant amounts; (3) sex does not seem to be an important biotic factor affecting fluoride bioaccumulation in signal crayfish; (4) in contrast, the type of tissue is an important biotic factor affecting fluoride bioaccumulation in signal crayfish, with the exoskeleton accumulating more fluoride than the muscle, in absolute terms, but with the muscle accumulating more fluoride than the exoskeleton, in relative terms (in relation to pre-effluent/control values); (5) the developmental stage seems to be another important biotic factor affecting fluoride bioaccumulation in signal crayfish, with juveniles being able to accumulate fluoride more rapidly than adults under fluoride pollution conditions; (6) although, during depuration periods, signal crayfish may significantly release fluoride, they can still retain significant amounts of the fluoride previously bioaccumulated during exposure periods. We can overall conclude that fluoride bioaccumulation in signal crayfish may be used as suitable bioindicator of fluoride pollution in those freshwater ecosystems where it is already present. However, this notable capability to accumulate and retain fluoride poses a potential risk to human health when signal crayfish from fluoride polluted areas are consumed.

Re-evaluating dual-porosity effects at the site of a seminal groundwater modelling study: Tilmanstone, southern England

Abstract The first numerical model of solute transport to incorporate Fickian diffusive exchange between mobile fracture water and immobile porewater for an actual case of groundwater contamination at catchment scale was applied to the Chalk aquifer at Tilmanstone in SE England by Bibby ( Water Resources Research , 1981, 17 , 1075–1081). The unconfined aquifer at Tilmanstone had been contaminated by coalfield brine leaking from disposal lagoons operating throughout much of the twentieth century. Recent observations show that the Bibby model underestimates dual-porosity diffusive retardation, and hence underestimates the persistence of contamination, probably by several decades. 2D representation of the aquifer in plan ignored the hydrostratigraphy, and model calibration was limited by the lack of time-variant paired profiles of fracture water and porewater. Vertical profiles through the Chalk determined by packer testing, borehole dilution testing and geophysical logging, together with a new depth profile of chloride concentration in Chalk matrix porewater, are described. The hydrostratigraphy is interpreted in relation to the Chalk lithostratigraphy of SE England, and incorporated into a vertical-section model of chloride transport along the axis of the valley, consistent with the new and historical profiles of fracture water and porewater chloride concentrations. New predictions of the longevity of the chloride contamination at Tilmanstone are presented.

Effects of chlorides in effluents used for irrigation on the irrigated crops

Chloride is an essential micronutrient as a cofactor in the oxidation of water in photosynthesis and as an activator of enzymes. It is readily taken up by plants. Chloride also serves in the plant as a charge balance during cation transport, and contributes to cell hydration and turgor maintenance. In the soil, chloride balances the positive charge of the soluble cations Na, Ca, Mg, and potassium. Treated effluent water, which is increasingly used for agricultural irrigation, contains higher chloride levels then the potable water from which it is derived. High concentrations of chloride in the irrigation water or the soil are toxic to plants and may affect plant function and reduce productivity. Despite the voluminous literature on saline soils, it is difficult to answer the question: how long can water containing high chloride levels safely be used for agricultural purposes under given conditions before damage to soil and plants is observed. The answer to this question must take into consideration soil clay content and clay type, irrigation methods, evaporation conditions, and plant type and composition. The chloride anion is very stable and will not leave the soil system unless it is leached by an excess of good quality irrigation water, or removed from the soil by exported vegetative plant parts. Continuous long-term utilization of recycled water for irrigation may therefore increase the chloride content of the soil, and without proper leaching it will deteriorate soil fertility, and under extreme conditions may render the soil unproductive.

A Novel Approach to Overcome Adherence Property of Candida albicans

The study is aimed to introduce a procedure that mimic the adherence of microorganisms to the plastic tube and to assess the suitable solution to irrigate these microorganisms. Candida albicans broth was inoculated into a 30 cm plastic tube for a certain period of time to allow the adherence of microorganism to the inner surface of tube. Tubes were irrigated with distilled water, tap water or different concentrations of sodium chloride (0.1-0.9%). The results showed that the percentage of Candida albicans which adhered to the inner surface of tube ranged between 0.27% and 30% of the initial inoculum. Tap water was superior than distilled water in removing the adherent Candida. Sodium chloride in concentrations 0.3%, 0.6% and 0.9% completely removed the attached Candida while the other concentrations showed inconsistent results. It concludes that irrigation with water or certain sodium chloride concentrations, which interfere with the fluidity of Candida albicans, is the simple and best method to eliminate the adherent microorganisms.

Influence of microwave heating on fluoride, chloride, nitrate and sulfate concentrations in water

This paper describes a study about the influence of microwave radiation using closed vessels on fluoride, chloride, nitrate and sulfate concentrations in aqueous media. The experiments were processed by heating water using PFA vessels and a microwave cavity oven, determining the anions by ion chromatography. The influence of the exposure time, the atmospheric composition, the kind of heating (water bath or microwave radiation) and the possible formation of hydrogen peroxide were investigated. The limits of quantification for fluoride, chloride, nitrate and sulfate were respectively of 0.17, 0.15, 0.55 and 0.57μgL−1, and precision, expressed as RSD, was <4% for all considered anions. The hydrogen peroxide was quantified by spectrophotometry, and the limit of quantification and precision were 24μgL−1 and <5% (n=10), respectively. The results demonstrate a significant increase in the anion concentration levels (between 63 and 89%) when microwave heating was used in comparison with heating by water bath. In addition, these changes observed can be mainly attributed to the species transfers, either between gaseous (atmospheric gases) and liquid (water) phases for nitrate, or between vessels walls and water for fluoride, chloride and sulfate. Additionally, hydrogen peroxide concentration higher than 45μgL−1 was determined when water was exposed to microwave radiation.

The dark side of the hyporheic zone: depth profiles of nitrogen and its processing in stream sediments

1. Although it is well known that sediments can be hot spots for nitrogen transformation in streams, many previous studies have confined measurements of denitrification and nitrate retention to shallow sediments (<5 cm deep). We determined the extent of nitrate processing in deeper sediments of a sand plains stream (Emmons Creek) by measuring denitrification in core sections to a depth of 25 cm and by assessing vertical nitrate profiles, with peepers and piezometers, to a depth of 70 cm. 2. Denitrification rates of sediment slurries based on acetylene block were higher in shallower core sections. However, core sections deeper than 5 cm accounted for 68% of the mean depth-integrated denitrification rate. 3. Vertical hydraulic gradient and vertical profiles of pore water chloride concentration suggested that deep ground water upwelled through shallow sediments before discharging to the stream channel. The results of a two-source mixing model based on chloride concentrations suggested that the hyporheic zone was very shallow (<5 cm) in Emmons Creek. 4. Vertical profiles showed that nitrate concentration in shallow ground water was about 10–60% of the nitrate concentration of deep ground water. The mean nitrate concentrations of deep and shallow ground water were 2.17 and 0.73 mg NO3-N L−1, respectively. 5. Deep ground water tended to be oxic (6.9 mg O2 L−1) but approached anoxia (0.8 mg O2 L−1) after passing through shallow, organic carbon-rich sediments, which suggests that the decline in the nitrate concentrations of upwelling ground water was because of denitrification. 6. Collectively, our results suggest that there is substantial nitrate removal occurring in deep sediments, below the hyporheic zone, in Emmons Creek. Our findings suggest that not accounting for nitrate removal in deep sediments could lead to underestimates of nitrogen processing in streams and catchments.

Modelling long term corrosion behaviour of copper canisters in KBS-3 repository

The well known KBS-3 repository design involves the disposal of spent fuel in copper canisters in a deep geological repository sealed with clay based buffer and backfill materials. A one-dimensional reactive transport model has been developed to predict the evolution of the general corrosion behaviour of the copper canisters by the initially trapped O2 and by sulphide ions. Various sources of sulphide are considered, including the microbial reduction of sulphate, the dissolution of pyrite impurities and the ground water itself. The model has been used to simulate the evolution of the canister corrosion behaviour for various scenarios, including both the Olkiluoto and Forsmark proposed repository locations, the vertical and horizontal KBS-3 design variants, increased ground water sulphide or chloride concentrations, different microbial scenarios, different rates of repository saturation, and with and without the dissolution of pyrite. Following a brief description of the model, the results of these and other simulations are described.

Salinity Effects from Evaporation and Transpiration under Flood Irrigation

Transpiration and evaporation rates from irrigated pastures can be adequately assessed by conventional methods and more recently, by the use of stable isotopes δH2 and δO18. However, the salinity effects that transpiration and evaporation have on infiltrating irrigation waters and residual soil-waters have not been independently assessed in a flood irrigation setting. In this study, oxygen-18, deuterium and chloride concentrations of irrigation water, soil-water, and groundwater were monitored with soil-water content over time to independently assess the salinization effects of evaporation and transpiration. This study was carried out across four flood irrigation sites that overlie a heterogeneous loam-sand and limestone vadose zone. Results showed that minor evaporation losses were detected across most flood irrigation sites through the use of stable isotopes δH2 and δO18. The associated increase in chloride concentration of irrigation water as a result of evaporation (minor fractionating water loss) was...