The gas absorption/chemical reaction (GACR) method developed in chemical engineering to measure gas–fluid interface in reactor systems is adapted for natural porous geologic media. Several series of column experiments were conducted using model glass beads and a natural sand to determine optimal operational conditions for measuring air–water interfacial area with the adapted method. The impacts of operational variables were investigated, including liquid and gas volumetric flow rates, solution concentration, and temperature. The results show that the magnitude of the measured air–water interfacial area is dependent upon all of these variables to greater or lesser degrees. Larger fluid flow rates promote distribution and mixing of the fluids, enhancing absorption and reaction. Increasing the concentration of NaOH in solution reduced the relative utilization of NaOH, promoting pseudo-first-order reaction conditions. The results elucidate the optimal operational conditions for application of the method to geomedia systems.

Agricultural intensification has led to the use of high inputs of chemical fertilizers into rice-cultivated lands, and nitrogen and heavy metals in runoff loss from land were a major environmental problem. It is important to mitigate nitrogen and heavy metal pollution for the water body. The nitrogen and heavy metal transformation in the rice field surface water was studied by applied combined organic and inorganic nitrogen fertilizer plus the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) in the sandy loam paddy soil and blue clayey paddy soil. The results showed that, the application of DMPP in the rice field in organic and inorganic fertilizer combined application models decreased the heavy metal average concentration of total Cu, Zn, and Cd by 22.1 to 30.2, 33.1 to 36.9, and 10.9 to 17.5% in surface water, respectively. Furthermore, in the sandy loam paddy soil and blue clayey paddy soil, the nitrate, nitrite, and total inorganic nitrogen concentrations decreased by 44.4 and 59.6, 90.3 and 88.6, and 14.2 and 25.4% in the rice field surface water with the DMPP addition, in the organic and inorganic fertilizer combined application models in the rice field, respectively. DMPP could be used as an effective nitrification inhibitor to decline the potential nitrogen and heavy metals runoff loss in the combined application models of organic and inorganic fertilizers in some rice fields, minimizing the nitrogen and heavy metal transformation risk from agricultural fields to the water body and being beneficial for protecting the ecological environment.

The aim of this study was to determine if benthic diatoms can be used as effective and reliable indicators of ionic composition and conductivity in different stream order categories. Samples were collected on two occasions from 22 sampling sites within the Bloukrans River system, Eastern Cape Province, South Africa. The data collected were subjected to multivariate statistical technique, i.e. CCA, to determine environmental gradients along which the diatom species were distributed as well as to elucidate hypothesised differences in community structure per stream order. Significant differences between the two sampling periods were observed in dissolved oxygen, temperature, Na, B, Ca, Zn, Cu, Cr, K, Fe, phosphate, conductivity, salinity and nitrate, while significant stream order variation was observed for conductivity, salinity, Mg, Ca and sediment nitrates. Study sites were grouped into two broad categories (stream order 1 and 2/3 sites) based on CCA. As pollution increased, low to moderate pollution-tolerant species such as Fragilaria tenera, Cyclostephanos dubius and Gyrosigma acuminatum were replaced by high pollution-tolerant species such as Nitzschia palea, Gomphonema parvulum, Tryblionella apiculata, Diploneis vulgaris and Staurosira elliptica. This shows that diatom assemblages are appropriate indicators of ionic composition/conductivity and hydromorphological characteristics (e.g. stream size) of running waters. The results highlight the importance of creating regional calibration datasets which will make it possible to develop procedures to determine conductivity and ion concentration effects on biota.

With an annual production of about 10 Gt concrete is by far the most used solid man-made material. In order to adjust the workability of fresh concrete most often so-called superplasticisers, essentially water-soluble organic polymers, are utilised. As concrete is commonly in direct contact with soil or water, the leaching of organic and inorganic compounds and their environmental impact need to be assessed. The present study contributes to this purpose by investigating leachates from hardened cement pastes gained using the horizontal dynamic surface leaching test. Pastes were prepared with and without superplasticiser. The root growths as well as the germination behaviour of cress (Lepidium sativum) and white mustard (Sinapis alba) were examined with respect to phytotoxicity. Different proportions (100, 50, 25 and 12.5%) of the leachates were considered in the test scheme. The results indicate a positive effect of most of the leachates on seed germination and root growth, although statistical significance was only found in some cases. Both test species showed no or only slight harmful effects as relative root growth exceeded always 66% for S. alba and 74% for L. sativum. Seed germination was not negatively influenced by the leachates. Slight beneficial effects on both test species could be observed for leachates containing superplasticiser compared to samples in absence of superplasticiser.

Except for the specific surface area and pore size, the hydroxyl groups on the surface of the ferric oxides were determined as the key factor in arsenic adsorption in this study. Two synthetic mesoporous ferric oxides, amorphous ferric oxyhydroxide (AFO) and goethite, were used to adsorb As(III) and As(V) in aqueous solution. The experimental results showed that the AFO had a higher hydroxyl group density, resulting in a higher arsenic adsorption capacity than that on the goethite for both As(III) and As(V). Also, it was found that the adsorption of As(III) on both the goethite and AFO was faster than that of As(V), and the adsorption rate fitted the pseudo-second-order kinetics. The findings indicated a promising modification of adsorbents for arsenic remediation.

Zinc oxide nanoparticles were evaluated for the removal of hydrogen sulfide from low-temperature gases, as well as swine manure gas using laboratory and semi-pilot scale systems. Effects of gas flow rate (200 and 450 mL min⁻¹), H₂S concentration (90–1500 ppmv), temperature (1–41 °C), and particle size (18, 80–200 nm) were investigated in the laboratory scale system using premixed gases (H₂S-balanced N₂). The breakthrough and equilibrium adsorption capacities increased with an increase of H₂S concentration. Application of high gas flow rates saturated the adsorbent faster and decreased the adsorption capacities. Adsorption capacities of 18 nm particles were higher than those of 80–200 nm. Regardless of H₂S concentration, the equilibrium adsorption capacity was not affected by temperature in the range 1 to 22 °C but increased when a higher temperature of 41 °C was applied. Among the evaluated isotherms, Langmuir-Freundlich described the equilibrium data obtained with 18 and 80–200 nm particles with a higher level of accuracy. Experiments in a semi-pilot scale adsorption system with 18 nm ZnO and gases emitted from the stored swine manure demonstrated the effectiveness of ZnO nanoparticles in removal of H₂S from these representative gases. Specifically, treatment of manure gas in the semi-pilot scale adsorption system decreased the level of H₂S from an average inlet value of 235.7 ± 85.2 ppmv to a negligible level.

The adsorption of some benzene derivatives—o-xylene, toluene, phenol, and benzyl alcohol onto dissolved humic acids (HA) was analyzed by equilibrium dialyses experiments. HA were extracted from compost and from leonardite. The humification index (E₄/E₆ ratio) and the distribution coefficient between ammonium sulfate/polyethylene glycol solutions show that HA from compost have a higher hydrophobicity. Assuming that the binding sites onto HA molecules are energetically equivalent, the binding curves were analyzed, and the amount of ligands bound per unit weight of HA and the association constants were derived. The binding capacity was higher for the HA from compost and for more hydrophobic ligands.

The potential of a membrane bioreactor (MBR) system to treat Fischer-Tropsch (FT) reaction water from gas-to-liquids (GTL) industries was investigated and compared with the current treatment system: a conventional activated sludge system followed by an ultrafiltration (CAS-UF) unit. The MBR and the CAS-UF systems were inoculated with municipal activated sludge and operated in parallel for 645 days with four interruptions using synthetic FT reaction water. Both treatment systems achieved a removal efficiency of 98 ± 0.1% within 60 days after inoculation, the COD influent concentration was 1014 ± 15 mg L⁻¹. This suggests that MBRs form a suitable alternative to CAS-UF systems for the treatment of FT reaction water from the GTL industries. Moreover, the total fouling rates (F ₜ) of the membranes used from day 349 till the end were assessed. The average F ₜ was 7.3 ± 1.0 10¹⁰ m⁻¹ day⁻¹ for CAS-UF membranes and 2.8 ± 00.7 10¹⁰ m⁻¹ day⁻¹ for MBR-MT membranes. This indicates that MBR systems for the treatment of FT reaction water from the gas-to-liquids industries are less prone to fouling than CAS-UF systems.

Climate change affects water resources worldwide, and Southern Europe is one of the areas where water scarcity is expected to increase in the future. Different water scarcity indicators discussed in this manuscript (e.g. total annual actual renewable water resources, water exploitation index and dependency ratio) showed that some parts of this region are already facing water stress and that climate change could have a great impact on their water supply sector. As agriculture is the biggest consumer of water in the world and also in this particular region, potential water scarcity will impose the need to find new water sources. Treated wastewater reuse would decrease the pressure on the environment and is especially suitable for reuse in agriculture since it already contains some nutrients required for plant growth. However, in order to use it safely, treated wastewater must reach a certain quality that should be regulated. In the south of Europe, 4 countries out of 15 have already adopted wastewater reuse regulations (Greece, Italy, Portugal and Spain). This review compares these regulations and discusses their differences.

The quantities of residual mulch film in the soil will further increase with the wide application of agricultural plastic mulch film, and the pollution of residual mulch film, which is a continuous pollutant and the one that is difficult to degrade, is a major limiting factor for the sustainable development of agriculture in China. Residual mulch film in the soil inevitably affects soil hydrodynamic parameters, destroys the homogeneity of the soil texture, seriously impedes the movement of soil water and solutes, and thus greatly influences crop growth and fruit quality. To unravel the effects of residual mulch film on tomato growth and fruit quality, pot experiments in the greenhouse were carried out in 2015 and 2016 in Northwest China. Six levels of residual mulch film were applied: 0 kg ha⁻¹ (CK), 80 kg ha⁻¹ (T1), 160 kg ha⁻¹ (T2), 320 kg ha⁻¹ (T3), 640 kg ha⁻¹ (T4), and 1280 kg ha⁻¹ (T5). Plant height, stem diameter, dry biomass, yield, root length, root surface area, fruit shape index (FSI), soluble sugar content (SSC), organic acid (OA), vitamin C (VC), lycopene, and nitrate content (NC) were measured. Plant height, stem diameter, dry biomass, and yield of tomato had a downward trend as the residual mulch film amount increased. Root length and root surface area were significantly decreased with an increasing amount of residual mulch film, but root volume and root diameter showed an inconspicuous decrease. When the amount of residual mulch film was more than 80 kg ha⁻¹, growth indexes, dry biomass, and yield of tomato showed a sharp decline. FSI, OA, and lycopene decreased as the residual mulch film amount increased, whereas SSC, VC, and NC showed an increase trend. With the increase in residual mulch film amount, the F and membership function values (X μ) all showed a declining trend in comparison to the CK. Therefore, residual mulch film can aggravate the negative effects on the comprehensive fruit quality of tomato.