Continuous use of recycled water (treated sewage effluent) over a long period of time may lead to the accumulation of salt in the root zone soil. This is due to the relatively higher levels of salt content in the recycled water compared to surface water. In this study, a laboratory column study was carried out to validate the HYDRUS 1D model under no rain condition. During the validation, the relative error and the % bias between observed and simulated soil water electrical conductivity (ECSW) were found to be low and varied in a range of 5–10 and 5–6 %, respectively. The validated model was then used to predict long-term (5 years) salt accumulation under drought conditions. The analysis of model predicted salt values showed a cyclical pattern of salt accumulation in the root zone, and this related to the variation in rainfall and evapotranspiration. The mean root zone ECSWin the 5th year was found to be within the highest salinity tolerance threshold for pasture (11.2 dS/m); however, the maximum root zone ECSWwas found to be about 63 % more than the threshold. Irrespective of seasons, in 5 years time, ECSWat the depth of 1.0 m increased from 3.0 to 7.0 dS/m, which may pose a salinity risk to the groundwater table if there is a perched water table at a depth <1 m below the field surface. One of the management options to minimise long-term salt accumulation was also examined. By reducing the salt in recycled water by 50 %, it was possible to keep the ECₛwwithin the recommended threshold values. Overall, the methodology developed in this study can be used to identify appropriate management options for sustainable recycled water irrigation.

Electric arc furnace (EAF) dust and slag, materials which contain high metals in their composition, were improperly disposed in an industrial steel mill site between 1963 and 1999. Previous environmental investigations identified anomalous concentrations of metals in local groundwater but failed to relate these abnormalities to the disposed material or to natural geochemical processes. Aiming to identify the origin of such abnormalities, exploratory and spatial data analysis (EDA-SDA) method was applied on a hydrogeochemical data set obtained through 5 sampling campaigns in 32 groundwater monitoring wells installed upstream and downstream of the area impacted by the steel mill activities. Boxplot class-based and Eh vs. pH maps of physicochemical log-transformed data identified that wells located under the influence of EAF slag deposits in topographic hollows had lower Eh potential and increased electrical conductivity and pH, when compared to wells in the topographical nose of the surveyed area. Metal distribution maps showed that Al, Ca, K, Mg, Na, and Sr were consistently higher in topographic hollows while concentrations of Co, Cu, Cr, and Li were higher near the former steel-making plant, located in the topographical nose. Ba, Fe, Mn, and Zn, important indicators of EAF slag and dust, were observed in both topographic settings. Variable clustering was able to capture the relations among metals and thus validate the log-normalized data structure to be used into wells clustering. Clustering through the mclust algorithm carried out for two and three clusters allowed the distinction among localities that received an input of metals from dust or slag and those not influenced by either residue. This paper demonstrates that EDA-SDA is an effective method to identify areas under the influence of contamination from industrial activities from areas not affected by anthropogenic contamination.

This study examined a single underground coal mine and investigated two aspects of its operation: the disposal of the mine waste through a discharge to a nearby river and the impact of subsidence from an underground longwall to a small waterway above. Water quality of the two waterways was monitored over a 2-year period with a monthly investigation over a 6-month period, which included collection of stream macroinvertebrates. Both mine activities modified surface water geochemistry and macroinvertebrate communities. Mean electrical conductivity (EC) increased in surface waters below the mine discharge, rising 4.8 times from (186 μS/cm) upstream to 1078 μS/cm below the waste inflow. Mean EC increased in a small stream that was disturbed by subsidence from longwall mining, rising 3.8 times from (247 μS/cm) upstream to 1195 μS/cm below. The mineral constituents of the increased salinities were different. The coal mine wastewater discharge was enriched with sodium and bicarbonate ions compared to sodium and chloride ions in the subsidence affected creek. Both the waste discharge and the subsidence caused increases in the concentrations of zinc by about four times and nickel by 20 to 30 times the background levels. The subsidence reduced dissolved oxygen to ecologically stressful levels and increased iron and manganese concentrations by about 20 times the background levels. Two of the key changes in stream ecosystems were a reduction in the proportion of mayfly larvae downstream of the mine waste discharge and mosquito larvae dominating (60–70 % of total abundance) the invertebrate community in the subsidence affected creek.

Early detection of landfill leachate plumes may minimise aquifer degradation and financial expenditure for the landfill operator. Current methods of landfill leachate monitoring typically include analysis of groundwater field parameters such as electrical conductivity (EC), coupled with laboratory analysis of a selection of major cations and anions. In many instances, background influences can mask the impact of leachate, which only becomes apparent once a significant impact has occurred. Here, we investigate the potential for changes in fluorescent dissolved organic material (FDOM) concentration to be used as an indicator of leachate impact. The research was undertaken in a fractured rock aquifer located downgradient of a local government-operated putrescible landfill in Central West NSW, Australia. Field measurement of groundwater FDOM was undertaken using an in situ fluorometer (FDOM probe) which provides a relative measurement of FDOM. To quantify the FDOM values, a bench fluorescence spectrophotometer was used to collect excitation/emission spectra. A plume of elevated FDOM and EC levels within the fractured rock system up to 600 m downgradient of the landfill was identified, whereas analysis of major cations and anions from boreholes within the plume did not detect leachate impacts above background. Excitation/emission matrices of groundwater from these locations confirmed that similar fluorescence signatures to those collected from the landfill were present. Photodegradation experiments were conducted to determine if fluorescent whitening agents (FWAs) were a component of the fluorescence signal. Observed photodegradation of 40 % compared to background (8 %) suggests that a component of the fluorescence signal can be attributed to FWAs. FDOM in groundwater therefore provides an indicator of low-level (up to 98 % dilution) leachate influence, and the identification of FWAs within groundwater can be considered confirmation of a leachate signal.

The electrokinetic transport of sulfate was investigated as a means of treating and restoring a sulfate-accumulating saline soil. The electrokinetic treatment decreased the electrical conductivity of the soil, an indicator of soil salinity, to 58.6, 73.1, and 83.5 % for 7, 14, and 21 days, respectively. More than 96 % of the chloride and nitrate were removed within 7 days. However, the removal of sulfate was highly influenced by the anode material. An iron anode removed sulfate effectively, whereas sulfate was hyper-accumulated in the anodic region when an inert anode was used. The iron anode was oxidized in a sacrificial anodic reaction, which competed with the electrolysis reaction of water at the anode, and finally, the reaction prevented the severe acidification of the soil in the anodic region. However, the competing reactions produced hydrogen ions at the anode and the ions were transported toward the cathode, which, in turn, acidified the soil, especially in the anodic region. The acidification switched the surface charge of the soil from negative to positive, increasing the interaction between the soil surface and sulfate and thus inhibiting the transport of sulfate under the electric field. The zeta potential analysis of the soil provided an explanation. The results indicate that preventing severe acidification is an important factor which influences the transport of anions and iron anode for the enhanced removal of anionic pollutants by electrokinetic remediation.

In many parts of the world, fluoride in drinking water is responsible for notable public health issues. The present study is aimed to prepare a new adsorbent magnesia-hydroxyapatite (Mg-HAP) that can serve as a valuable defluoridating agent. Characterization of the synthesized adsorbent was done by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Transmission electron microscope (TEM), and Scanning electron microscope (SEM)/Energy-dispersive X-ray spectroscopy (EDX) analysis to reveal the bonding patterns, phase characteristics, and microstructural and morphological details. The influences of pH, adsorbent dose, contact time, and initial fluoride concentration and the effect of interfering anions were studied. The defluoridation capacity was evaluated to be 1.4 mg/g, and the adsorbent showed very good capability to remove fluoride from contaminated water over a wide range of pH. Equilibrium modeling was done, and the experimental data was fitted into Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherms. Study of the kinetic data for the adsorption process revealed that it follows pseudo-second-order reaction. It also indicated that the intraparticle diffusion contributes to the rate-determining step in the process. The quality of treated water was analyzed for total dissolved solids (TDS), turbidity, residual calcium, residual phosphorus content, electrical conductivity, hardness, and total alkalinity. The results obtained were very promising and confirmed the prospects of usage of Mg-HAP in defluoridation of drinking water.

Inadequately treated effluents from industry have serious environmental and public health concerns. Even low level discharges create problems through accumulation in water and soil. In the present work, the pollutant accumulating capacity and the general environmental health status of soil which is a repository of treated and untreated effluent discharges and solid waste dumping of a giant pulp and paper mill have been evaluated with respect to some selected physicochemical parameters. The pollutant accumulating capacity of the soil in seven well-defined sites in and around the mill was found with reference to a “control” site with no history of receiving effluent discharges or solid wastes. The changes in texture, bulk density, water-holding capacity, electrical conductivity, pH, organic carbon, cation exchange capacity, exchangeable sodium, etc. of the soil up to the normal tilled depth were observed in different seasons. In most sites, the soil organic carbon was poorly correlated to the bulk density, water-holding capacity, pH, and clay and sand contents, indicating an unhealthy state of the soil and, correspondingly, nearly exhausted pollutant accumulating capacity. Considerable differences in pH, electrical conductivity, bulk density, and water-holding capacity were observed between the soil receiving effluent discharge and solid waste dumping and the control soil. The soil had accumulated considerable amounts of the exchangeable cations (Ca, Mg, Na, and K). The work has found that industrial activities have worked against the normal behavior of the soil and reduced its capacity to serve as a natural repository of carbon.

During the extraction of coal bed methane (CBM), entrapped in the deep layers of different coal beds, large amount of coal bed water (CBW) is also simultaneously released. The quality of this water is generally very poor which may often contaminate the adjoining soil environment adversely. In the present study, some major changes occurring in CBW-contaminated soils were assessed with relation to nearby non-affected soils. The CBW was found to be moderately saline and highly alkaline in nature with high sodium absorption ratio (SAR) values. Contamination with this water affected the soil environments substantially resulting in significantly increased pH and exchangeable sodium percentage (ESP) in the affected soils thus rendering the soils unsuitable for undertaking common agricultural practices. However, in spite of moderately high electrical conductivity values of this contaminating water, the resultant increments in salinity status of the soils were not observed to reach near the critical level. This behaviour was attributed to light texture of these soils which probably helped in leaching of a part of the soluble salts. Some microbial properties as well as availability of nitrogen and phosphorus were also found to decline in these CBW-affected soils. The study showed that utmost care needs to be exercised before release of CBW during extraction of CBM. In case of any contamination to nearby arable soils, suitable amendment practices for alkaline soils need to be adopted to mitigate the adverse effects of such water on soil environment.

Accumulations of mass loads of selected chemicals in roadside snowbanks were studied at five sites with various traffic densities in the city of Trondheim (Norway) by collecting snow samples throughout the winter period and analyzing them for 13 water quality constituents: pH, electrical conductivity (EC), alkalinity, Cl, Na, total suspended solids (TSS), Cd, Cr, Cu. Ni, Pb, W, and Zn. The resulting dataset was then supplemented by similar data collected earlier in the city of Luleå (Sweden). Regression analyses for individual sites indicated linear trends in unit-area constituent accumulations with time (0.65 < R ² < 0.95) and supported the assumption of linearity in further analyses. Principal component analysis (PCA) of the combined Luleå/Trondheim data revealed cause-effect relationships between the chemical mass loadings (TSS and trace metals) and three predictors: snow age (snow residence time (SRT)), traffic density (annual average density of traffic (AADT), and cumulative traffic volume (CTV = SRT × AADT). Cl and Na loads, originating from road salt applications in Trondheim only, did not display this trend. Two types of parsimonious models for predicting trace metal accumulations in winter-long roadside snowbanks were developed: (a) a linear regression model using CTV as a single predictor and predicting metal accumulations with a moderate certainty (0.37 < R ² < 0.66) and (b) multiple regression models using SRT, AADT, and snow water equivalent (SWE) as predictors. The latter models indicated good correlations between the mass loads and the predictors (0.64 < R ² < 0.77) and produced slightly better prediction accuracies (0.44 < R ² < 0.67) than the simpler model.

Long-term fire retardant (LTR) use for forest fire suppression and/or prevention purposes can result in chemical leaching, from soil to the drainage water, during the annual rainfall period. Also, wildland fires can have an impact on the leaching of various chemicals from treated forest soils. Large quantities of ions in leachates, mainly due to ammonium (one of the major LTR components) soil deposition, could affect the groundwater quality. The alteration of pH, total hardness (TH), and electrical conductivity (EC) values in leachates mainly due to nitrogen-based LTR application (Fire Trol 931) was investigated in this laboratory study. The values of pH, TH, and EC were measured in the resulting leachates from pots with forest soil and pine trees alone and in combination with fire after a simulated rainfall period. pH, TH, and EC values in leachates from all treated pots were significantly greater than those from control pots.