The processing, storage, and flux of inorganic carbon in rivers and streams play an influential role in the lateral transfer of atmospheric and terrestrial carbon to the marine environment. Quantifying and understanding this transfer requires a rapid and accurate means of measuring representative concentrations of dissolved inorganic carbon (DIC) and CO₂in field settings. This paper describes a field method for the determination of DIC based on the direct measurement of dissolved CO₂using a commercial carbonation meter. A 100-mL water sample is combined with 10 mL of a high ionic strength, low-pH, citrate buffer, mixed well, and the dissolved CO₂concentration is measured directly. The DIC is then calculated based on the dissolved CO₂concentration, buffer-controlled ionic strength, pH, and temperature of the mixture. The method was accurate, precise, and comparable to standard laboratory analytical methods when tested using prepared sodium bicarbonate solutions up to 40 mM DIC, North Atlantic seawater, commercial bottled waters, and carbonate spring waters. Coal mine drainage waters were also tested and often contained higher DIC concentrations in the field than in subsequent laboratory measurements; the greatest discrepancy was for the high-CO₂samples, suggesting that degassing occurred after sample collection. For chemically unstable waters and low-pH waters, such as those from high-CO₂mine waters, the proposed field DIC method may enable the collection of DIC data that are more representative of natural settings.

Concentrated animal feeding operations (CAFOs) are the principal means of livestock production in the USA and Europe, and these industrial-scale facilities have a high potential to pollute nearby waterways. Chemical and biological stream water quality of a swine and poultry CAFO-rich watershed was investigated on 10 dates during 2013. Geometric mean fecal coliform counts were in the thousands at five of seven sites, especially in locations near swine waste sprayfields. Nitrate concentrations were very high and widespread throughout the watershed, with some individual samples yielding >10 mg-N/L. Ammonium concentrations were likewise high, but greatest near swine waste sprayfields, ranging up to 38 mg-N/L. Five-day biochemical oxygen demand (BOD5) concentrations exceeded 10 mg/L in 11 of 70 stream samples, reaching as high as 88 mg/L. BOD5 concentrations were significantly correlated with components of animal waste including total organic carbon, ammonium, and phosphorus, as well as the nutrient response variable chlorophyll a. The degree of nutrient and fecal contamination did not significantly differ between rainy and dry periods, indicating that surface and groundwater pollution occurs independently of stormwater runoff. This research shows that industrial-scale swine and poultry production leads to chronic pollution that is both a human health and ecosystem hazard. There are approximately 450,000 CAFOs currently operating in the USA, with the majority located in watersheds feeding major riverine and estuarine systems with known water quality problems. Current US waste management protocols for this widespread system of livestock production fail to protect freshwater and estuarine ecosystems along the US Mid-Atlantic, Southeast and Gulf coasts, and expansion into industrializing nations will likely bring severe pollution with it.

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.

The capability of W⁶⁺-impregnated ZnO photocatalysts for sunlight mineralization of a variety of structurally different dyes has been investigated. Compared to bare ZnO, the W⁶⁺-loaded photocatalysts showed significantly higher activity for the decolorization as well as mineralization of dyes, and complete mineralization was noticed in a short span of 150 min. The results obtained by various analytical tools were correlated to estimate the mechanistic aspects of the decolorization/mineralization process and to identify the nature of the oxidizing species involved in the process. A strong dependence of the decolorization/mineralization process was observed on the nature and number of auxochromes attached to color-generating conjugated system. The rapid decolorization/mineralization of the dyes and release of corresponding anions with the decolorization of dyes suggested the involvement of charged rather than radical reactive oxygen species (ROS) in the oxidation process. Langmuir-Hinshelwood kinetic model was found to be best suited for evaluating the kinetics of mineralization process. The effectiveness of the catalysts for the decolorization/mineralization of a mixture of dyes was also examined. The suitability of the catalysts for successive use in sunlight exposure was also evaluated.

The bioactivity of three kinds of multi-walled carbon nanotubes (MWCNT) towards the conidia of entomopathogenic fungus Isaria fumosorosea was examined in an in vitro study. Commercial—raw and functionalized—carboxylated MWCNT were applied. A fungal conidia suspension was placed in contact with dispersed MWCNT over different time-periods. After contact with the nanomaterial, the conidia were cultured on dishes and both the linear vegetative mycelium growth and the sporulation and germination of the spores derived from the culture were investigated. Also, the pathogenicity of the conidia after contact with MWCNT was examined in relation to test larvae. No fungistatic activity of MWCNT relative to I. fumosorosea conidia was demonstrated. Conidia contact with MWCNT resulted in the following changes in vital processes in the subsequent culture compared to the control standard culture: (1) raw MWCNT limited mycelium inoculation, but the growth rate observed later in the log-phase was more intense; (2) after 24-h conidia contact with all MWCNT types, the mycelium sporulated the most intensively; longer contact resulted in sporulation process limitation. Germination of conidia after contact with the MWCNT was not significantly modified. Raw MWCNT potentiated conidia pathogenicity towards test insects. It was observed that carboxylation of MWCNT reduces the bioactivity of this nanomaterial towards the investigated conidia.

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.

Removal of p-nitrophenol (PNP) from aqueous solutions using fibrous peat has been investigated in this study by batch adsorption experiments. Factors that can affect the adsorption process, such as pH, temperature, initial PNP concentration and contact time, have been investigated. Fourier transform infrared (FTIR) and thermogravimetric analysis (TGA) measurements have also been obtained in order to study the adsorption mechanism of PNP by peat. The Langmuir and Freundlich equations have been applied to investigate the equilibrium. The data fitted the Langmuir isotherm well, with the maximum adsorption capacity decreasing with temperature from 23.4 to 16.1 mg g⁻¹. In general, the adsorption equilibrium was attained within 100 min. For the kinetics study, the best fit was obtained by the pseudo-second-order model instead of the pseudo-first-order model, both of which applied to the experimental data, whereas the results of intraparticle diffusion show a two-step adsorption process. The activation energy value of 70.31 kJ mol⁻¹, calculated from the Arrhenius equation, indicated a predominantly chemical adsorption, whereas the thermodynamic parameters, obtained by the van’t Hoff equation, were exothermic and spontaneous in nature.

Dairy soiled water (DSW) is water from concreted areas, hard stand areas and holding areas for livestock that has become contaminated by livestock faeces or urine, chemical fertilisers and parlour washings. Losses of DSW occur as point (e.g. storage, pivot irrigators) and diffuse losses (e.g. during or shortly after land application). The concept of a permeable reactive interceptor (PRI), comprising a denitrifying bioreactor woodchip cell to convert nitrate (NO₃⁻) to dinitrogen (N₂) gas and an adsorptive media cell for phosphorus (P) and ammonium (NH₄⁺) mitigation, attempts to simultaneously treat mixed pollutants. This study is the first attempt to test this concept at laboratory-scale. Washing of woodchip media prior to PRI operation produced low NO₃⁻but high NH₄⁺, dissolved reactive P (DRP) and dissolved organic carbon losses. Dairy soiled water was then treated in replicated PRIs containing woodchip in combination with zeolite or gravel compartments. In general, all PRIs were highly efficient at reducing NO₃⁻, NH₄⁺, DRP, dissolved unreactive phosphorus (DUP) and dissolved organic nitrogen (DON) from an influent water replicating DSW. Longitudinal and hydrochemical PRI profiles, as well as zeolite batch experiments, showed that woodchip can both enhance NO₃⁻reduction and adsorb nutrients. Since woodchip is likely to become saturated, it is important to place the reactive media cell further into the sequence of treatment. Even though the majority of the dissolved nutrients were mitigated, the PRIs also emitted greenhouse gases, which would need further remediation sequences.

The current study focuses on the removal of perchlorate in water using single-walled carbon nanotubes (SWCNTs) and granular ferric hydroxide as sorbents. The randomly distributed tubes were observed by scanning electron microscopy. The influence of temperature and content of natural humic acid on the perchlorate adsorption capacity was examined at pH 3. The adsorption data were fitted with three models: modified Freundlich, pseudo-first order, and pseudo-second order. The modified Freundlich model produced the best fit to describe the kinetic adsorption processes. The adsorption capacities of perchlorate measured at 25 °C and pH 3 using single-walled carbon nanotubes and granular ferric hydroxide were about 6 and 3 mg/g, respectively. The influence of natural humic acid on perchlorate adsorption by SWCNTs was examined. Natural humic acid was derived from raw water in Gao-Ping River in south Taiwan. Lower adsorption reaction rates of perchlorate were obtained at higher humic acid concentrations. High humic acid concentrations induce the compression of the electric double layer that consequently reduces the surface potential energy and electrostatic repulsion.

A kind of volcanic tephra (VT) as abundant natural mineral in China was studied for phosphate (P) removal from rural micro-polluted wastewater. Physical and chemical properties of VT were investigated by scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDX), X-ray diffraction (XRD), UV-visible diffuse reflectance spectrometry, and Fourier transform infrared spectroscopy (FT-IR). The uptake of P decreased with the increase of the initial solution pH, and the optimum solution pH required for maximum P removal rate was 2.0. Zeta potential analyses were carried out to vividly describe the surface charges at different solution pH. The equilibrium data were both fitted well for Langmuir and Freundlich isotherm models. Thermodynamic parameters including changes in standard enthalpy (ΔH⁰), standard entropy (ΔS⁰), and standard Gibbs free energy (ΔG⁰) were calculated. The removal of P was predominantly based on ion-exchange process when the initial solution pH in the range of 2.0–6.0. A given dose of VT can be recycled for eight times. VT minerals were attempted for P removal from rural micro-polluted wastewater collected in Shanghai, China containing 50 mg L⁻¹P, and the removal rate was determined to be nearly 100 % with the capacity of 0.5 mg P/g VT minerals. All our results indicated that VT could be a promising choice for P removal from micro-polluted wastewater in rural area with the distinct advantages of being low cost and environmentally benign.