Appalachian surface coal mine overburden affects water quality as drainage percolates through spoil disposal fills. This study evaluated leaching potentials of 15 spoils from south-central Appalachia. Most bulk samples were non acid-forming, all were low in total-S, (≤0.34%), and initial saturated paste specific conductance (SC) ranged from 264 to 3560 μS cm−1. Samples were leached unsaturated (40 cycles) and leachates analyzed for pH, SC, and ion composition. Overall, leachates from unweathered spoils were higher in pH and SC than leachates from weathered spoils. Fine-textured spoils generally produced higher SCs than more coarsely textured spoils. Mean SC for all spoils decreased rapidly from an initial peak of 1468 μS cm−1 (±150) to 247 μS cm−1 (±23). Release patterns for most major ions reflected declining SC. Bicarbonate typically increased with successive leaches, replacing sulfate as the dominant anion. Column SC values were comparable to relevant published field data.

An important priority for any organism is to maintain internal cellular homeostasis including acid–base balance. Yet, the molecular level impacts of changing environmental conditions, such as low pH, remain uncharacterised. Herein, we isolate partial Na+/H+exchangers (NHE), carbonic anhydrase (CA), and calmodulin (CaM) genes from a polychaete, Platynereis dumerilii and investigate their relative expression in acidified seawater conditions. mRNA expression of NHE was significantly down-regulated after 1h and up-regulated after 7days under low pH treatment (pH 7.8), indicating changes in acid–base transport. Furthermore, the localisation of NHE expression was also altered. A trend of down regulation in CA after 1h was also observed, suggesting a shift in the CO2 and HCO3− balance. No change in CaM expression was detected after 7days exposure to acidified seawater. This study provides insight into the molecular level changes taking place following exposure to acidified seawater in a non-calcifying, ubiquitous, organism.

In this study, natural calcium-rich attapulgite (NCAP) was used to develop a low-cost adsorbent for removing fluoride (F⁻) from contaminated water. The results showed that calcination can dramatically increase the F⁻ sorption capacity of NCAP and that the maximum F⁻ sorption capacity occurred at 700 °C. The sorption of F⁻ on NCAP heated at 700 °C (NCAP700) followed pseudo-second-order kinetics and was described by the Langmuir equilibrium model. The estimated F⁻ sorption capacity was approximately 140.0 mg/g at pH 8.0, which was comparable with the sorption capacities of some nanomaterials. The sorption of F⁻ on NCAP700 performed well at pH values of 7 to 10. In addition, anions such as NO₃ ⁻ and SO₄ ²⁻ did not affect fluoride removal, but PO₄ ³⁻ and HCO₃ ⁻ moderately influenced fluoride removal. A column study conducted using NCAP700 with a particle size of 0.2–0.5 mm indicated that the adsorbent could effectively purify nearly 200 bed volumes (BV) of water containing 3.0 mg F/l at pH 8.5. The removal of F⁻ from water mainly resulted from the formation of calcium fluoride precipitates and the complexation of fluoride with the –OH group of NCAP700, which was further confirmed by scanning electron microscopy–energy dispersive spectrometry (SEM-EDS) and X-ray photoelectron spectroscopy (XPS).

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.

In this study, nanosized zero-valent iron-reduced graphene oxide (nZVI-rGO)-activated persulfate (PS) was used to investigate the generation of reactive oxygen species (ROS) for the degradation of trichloroethylene (TCE) in the aqueous solution. More than 98 % of TCE was degraded within 2 min under experimental conditions. The generation of ·OH increased when the pH was shifted toward the basic region while ·SO₄⁻ radicals’ intensity increased in the acidic pH. Different scenarios have been observed in ·O₂⁻ generation in the neutral and strong basic pH and decreased in acidic or slightly basic pH. In addition, the intensity of ·OH was increased with the addition of HCO₃⁻ (10 mM) and NO₃⁻ (100 mM) but decreased in the presence of Cl⁻ (10 and 100 mM), HCO₃⁻ (100 mM), and NO₃⁻ (10 mM). The degradation of anisole, probe for both ·OH and ·SO₄⁻, was slightly enhanced by 10 mM NO₃⁻ anions but decreased in 100 mM salt solution. ·O₂⁻ intensity was increased while HCO₃⁻ (10 and 100 mM) and NO₃⁻ (100 mM) anions were used. nZVI-rGO-activated PS process could remove TCE in aqueous effectively, and the ROS generation and intensity were influenced by solution pH values and anions.

Upland swamps of the Blue Mountains are unique and legislatively protected peat swamp communities. This study investigated water chemistry of surface waters from seven Blue Mountains Upland Swamps (BMUS), four within urbanised catchments and three from naturally vegetated catchments. The purpose of the study was to investigate any ionic contamination from urban development. Water chemistry of non-urban BMUS was acidic (mean pH 4.7) and dilute (mean EC 26.6 μS/cm) and dominated by sodium and chloride ions with most other major ions at low concentrations, often below detection limits. In contrast, urban BMUS had higher pH (mean 6.6) and salinity (mean 153.9 μS/cm) and were dominated by calcium and bicarbonate ions. The results of this study support the hypothesis that urban concrete contamination is modifying the geochemistry of urban BMUS. Further research is required to investigate ecological implications of the contamination and also to explore measures to protect such sensitive wetlands of high conservation value from urban development.

Increasing land utilization through diverse forms of human activities, such as agriculture, forestry, urban growth, and industrial development, has led to negative impacts on the water quality of rivers. To find out how catchment attributes, such as land use, hydrologic soil groups, and lithology, can affect water quality variables (Ca²⁺, Mg²⁺, Na⁺, Cl⁻, HCO₃⁻, pH, TDS, EC, SAR), a spatio-statistical approach was applied to 23 catchments in southern basins of the Caspian Sea. All input data layers (digital maps of land use, soil, and lithology) were prepared using geographic information system (GIS) and spatial analysis. Relationships between water quality variables and catchment attributes were then examined by Spearman rank correlation tests and multiple linear regression. Stepwise approach-based multiple linear regressions were developed to examine the relationship between catchment attributes and water quality variables. The areas (%) of marl, tuff, or diorite, as well as those of good-quality rangeland and bare land had negative effects on all water quality variables, while those of basalt, forest land cover were found to contribute to improved river water quality. Moreover, lithological variables showed the greatest most potential for predicting the mean concentration values of water quality variables, and noting that measure of EC and TDS have inversely associated with area (%) of urban land use.

The photo-disinfection of natural alkaline surface water (pH 8.6 ± 0.3) for drinking purposes was carried out under solar radiation treatments. The enteric bacteria studied were the wild total coliforms/Escherichia coli (10⁴ CFU/ml) and Salmonella spp. (10⁴ CFU/ml) naturally present in the water. The photo-disinfection of a 25-l water sample was carried out in a solar compound parabolic collector (CPC) in the absence and in the presence of hydrogen peroxide (H₂O₂). The addition of H₂O₂ (10 mg/L) to the sample water was sufficient to enhance the photo-disinfection and ensure an irreversible lethal action on the wild enteric bacteria contents of the sample. The inactivation kinetic of the system was significantly enhanced compared to the one carried out without H₂O₂ addition. The effect of the solar radiation parameters on the efficiency of the photo-disinfection were assessed. The pH has increased during the treatment in all the photo-disinfection processes (hv and H₂O₂/hv). The Salmonella spp strain has shown the best effective inactivate time in alkaline water than the one recorded under acidic or near-neutral conditions. The evolution of some physico-chemical parameters of the water (turbidity, NO₂ ⁻, NO₃ ⁻, NH₄ ⁺, HPO₄ ²⁻, and bicarbonate (HCO₃ ⁻)) was monitored during the treatment. Finally, the possible mechanistic process involved during the enteric bacteria inactivation was suggested.

The photolysis of the antimicrobial triclocarban (TCC) in aqueous systems under simulated sunlight irradiation was studied. The effects of several abiotic parameters, including solution pH, initial TCC concentration, presence of natural organic matter, and most common inorganic anions in surface waters, were investigated. The results show that the photolysis of TCC followed pseudo-first-order kinetics. The TCC photolysis rate constant increased with increasing solution pH and decreasing the initial TCC concentration. Compared with the TCC photolysis in pure water, the presence of aqueous bicarbonate, nitrate, humic acids, and its sodium salt decreased the TCC photolysis rate, but fulvic acid increased the TCC photolysis rate. The electron spin resonance and reactive oxygen species scavenging experiments indicated that TCC may undergo two different types of phototransformation reactions: direct photolysis and energy transfer to generate¹O₂. The main degradation products were tentatively identified by gas chromatography interfaced with mass spectrometry (GC-MS), and a possible degradation pathway was also proposed.

The effects of seasonal groundwater level fluctuations on the contamination characteristics of total petroleum hydrocarbons (TPH) in soils, groundwater, and the microbial community were investigated at a typical petrochemical site in northern China. The measurements of groundwater and soil at different depths showed that significant TPH residue was present in the soil in this study area, especially in the vicinity of the pollution source, where TPH concentrations were up to 2600 mg kg⁻¹. The TPH concentration in the groundwater fluctuated seasonally, and the maximum variation was 0.8 mg L⁻¹. The highest TPH concentrations were detected in the silty clay layer and lied in the groundwater level fluctuation zones. The groundwater could reach previously contaminated areas in the soil, leading to higher groundwater TPH concentrations as TPH leaches into the groundwater. The coincident variation of the electron acceptors and TPH concentration with groundwater-table fluctuations affected the microbial communities in groundwater. The microbial community structure was significantly different between the wet and dry seasons. The canonical correspondence analysis (CCA) results showed that in the wet season, TPH, NO₃ ⁻, Fe²⁺, TMn, S²⁻, and HCO₃ ⁻ were the major factors correlating the microbial community. A significant increase in abundance of operational taxonomic unit J1 (97 % similar to Dechloromonas aromatica sp.) was also observed in wet season conditions, indicating an intense denitrifying activity in the wet season environment. In the dry season, due to weak groundwater level fluctuations and low temperature of groundwater, the microbial activity was weak. But iron and sulfate-reducing were also detected in dry season at this site. As a whole, groundwater-table fluctuations would affect the distribution, transport, and biodegradation of the contaminants. These results may be valuable for the control and remediation of soil and groundwater pollution at this site and in other petrochemical-contaminated areas. Furthermore, they are probably helpful for reducing health risks to the general public from contaminated groundwater.