Sorption of antibiotics to clay minerals is a key process controlling their transport and fate in environment. In this study, the effects of pH, ionic strength, and Cu(II) on ofloxacin (OFL) sorption to kaolinite were investigated by batch sorption experiments. The results of sorption edge experiments suggested that OFL sorption to kaolinite was pH and ionic strength dependent. Cation exchange was a major contributor to the sorption of OFL⁺ to kaolinite. The decreased OFL sorption with increasing ionic strength indicated the formation of outer-sphere complexation. When solution pH was lower than 7.0, Cu-OFL complexes facilitated OFL sorption through electrostatic attraction or formation of kaolinite-Cu-OFL and kaolinite-OFL-Cu ternary surface complexes. However, existence of free Cu(II) cation in solution competed for sorption sites, and thus suppressed OFL sorption. When solution pH was higher than 7.0, Cu(II) existed as Cu(OH)₂, and the Cu-OFL complexes in aqueous phase and solid phase (precipitation) enhanced OFL removal efficiency from solution. The results imply that Cu(II) effects should be taken into account in the evaluation of OFL mobility in environment.

Spherical biochar derived from saccharides (glucose, sucrose, and xylose) was prepared through two steps: pre-hydrothermal carbonization at 190 °C and calcination at low temperatures (200–325 °C). The spherical biochar was characterized by Brunauer–Emmett–Teller (BET) surface area analysis, Fourier transform infrared spectroscopy, zeta potential, scanning and transmission electron microscopies, and X-ray diffraction. The result indicated that the spherical biochar exhibited low S BET (15–22 m²/g), but abundant superficial active oxygen-containing functional groups. The spherical biochar possessed a negatively charged surface within solution pH 2.0–11. The adsorption process of Pb²⁺, Cu²⁺, and methylene green 5 (MG5) was strongly dependent on the solution pH and reached fast equilibrium at approximately 60 min. The maximum Langmuir adsorption capacity (Q°ₘₐₓ) exhibited the following order: glucose-biochar > sucrose-biochar > xylose-biochar prepared at 300 °C. The selective adsorption order of glucose-biochar was Cu²⁺ (0.894 mmol/g) > Pb²⁺ (0.848 mmol/g) > MG5 (0.334 mmol/g). The electrostatic attraction played a determining role in the adsorption mechanism of pollutant cations. The adsorption of anionic dye (acid red 1) on the spherical biochar was negligible because of electrostatic repulsion. The spherical biochar can serve as a newer and promising adsorbent to remove toxic pollutant cations from water media.

Ammonia-oxidizing archaea (AOA) have aroused great attention since it can supplement nitrogen cycle and show extensive existence relative to its bacterial counterpart, ammonia-oxidizing bacteria (AOB). This study compared the abundance and community compositions of AOA and AOB between natural and constructed wetlands under low temperature. More complex community structures were obtained in the constructed wetland, which may be ascribed to the differences in available nutrient contents. Nitrosospira-like organisms predominated AOB communities in both wetlands. Nitrososphaera cluster dominated the AOA community in the constructed wetland, while both Nitrososphaera and Nitrosopumilus clusters were dominant in the natural wetland. AOA dominated over AOB in both the natural and constructed wetlands, and AOA to AOB ratio ranged from 1.47 to 8.13. The natural wetland showed higher nitrification potential at low temperature, mainly due to its higher AOA to AOB ratio. This also explained why a better ammonia treatment performance was observed in the natural wetland even when it had high influent concentrations. The present results provided some new insights to ammonia removal in the wetlands under low temperature.

Multiphase flow and transport simulations were conducted to investigate the impact of soil heterogeneity and non-aqueous phase liquid (NAPL) presence on the distribution of stable carbon isotope signatures during contaminant transport with biodegradation. At a later time during the simulation of a homogeneous case with dense NAPL presence, significant carbon isotope signature (δ¹³C) values could only be observed in a narrow area at the bottom of the aquifer where NAPL accumulated. After this, the δ¹³C distribution remained relatively stable for a long time until all NAPL was dissolved into the groundwater and removed via biodegradation and groundwater flushing. These characteristics of δ¹³C distribution may only be captured when considering NAPL migration and dissolution. The simulation results demonstrated that δ¹³C values and their distribution significantly differed between the heterogeneous case and the homogeneous case, with respect to the maximum δ¹³C value and the shape of δ¹³C contours. When reaction rate constant varied for each soil type (each grid block) by relating it to soil permeability, the δ¹³C distribution demonstrated different patterns. In addition to geological heterogeneity, this indicates that the distribution of δ¹³C highly depends on the biological heterogeneity in the field. Therefore, this study suggests that, to avoid misinterpretation of isotope signature changes, geological and biological soil heterogeneities should be investigated. If a NAPL is present in the system, the NAPL phase transport and dissolution should be considered in addition to dissolved phase transport.

Elemental sulfur is the most commonly found form of sulfur in anaerobic sediments. Accurate determination of elemental sulfur is the key step to know physical chemistry and biogeochemical processes in the sediments. A novel method was developed for the analysis of elemental sulfur using high-performance liquid chromatography (HPLC) with a C18 column. The procedure of determination of elemental sulfur concentrations from 0.1 to 100 mg/g (on a basis of the dry weight of sediment) is based on the direct injection of acetone extracts of sediments into a chromatographic column. The linearity range of 20–110 mg/L showed an excellent linearity of response (r = 0.999). The limit of detection and limit of quantitation for elemental sulfur were 9.41 and 4.18 μg/L, and converted sulfur mass per sediment mass was 1.88 × 10⁻² and 8.36 × 10⁻³ μg/kg. Besides, a repetitive experiment (ten times) was carried out and the average chromatographic peak area was 141.47 mg L⁻¹. The sulfur concentration in the solution used for the determination of standard deviation and relative standard deviation was 1.02 and 0.727%, respectively. The average recovery ranges between 98 and 100%. The quantitation of elemental sulfur in sediment samples from anaerobic digestion reactor is obvious, and the average concentration of elemental sulfur on the basis of the dry weight of the sediment is 5.24 mg/g. The method was sensitive and exhibited good signal-to-noise ratio, as well as linear responses over a wide concentration range.

In Aguascalientes, Mexico, there is a special concern about pesticides because of their intensive use on guava production areas, which are located in the vicinity of water reservoirs; thus, non-target organisms could be exposed. Thereafter, the aim of this work was to assess the effect of cypermethrin, Faena® (glyphosate), and malathion, which are the most used pesticides in Aguascalientes’ guava production, on the indigenous freshwater species Alona guttata (cladoceran) and Lecane papuana (rotifer). Acute 48-h toxicity tests were carried out, and LC₅₀ values were calculated. Then, five sublethal concentrations (1/80, 1/40, 1/20, 1/10, and 1/5 of the respective LC₅₀) were selected for the chronic assays: (a) intrinsic growth rate analysis in the rotifer and (b) partial life table analysis in the cladoceran. The results of the acute toxicity tests showed that A. guttata was more sensitive to malathion (LC₅₀ = 5.26 × 10⁻³ mg/L) at concentrations found in natural environments with continuous application on guava fields, whereas L. papuana was more sensitive to Faena® (LC₅₀ = 19.89 mg/L). The somatic growth of A. guttata was inhibited for the chronic exposure to cypermethrin. In addition, cypermethrin and Faena® seemed to exert endocrine disruptive effects on A. guttata. Moreover, malathion chronic exposure significantly decreased the survival of A. guttata. Moreover, L. papuana was affected chronically for the three pesticides.

Singapore is an island city state with an economy dependent on petrochemicals and shipping, but with severely limited water resources. This study aimed to establish a suitable methodology specifically for the translation of a laboratory-scale system to an industrial scale for the treatment of phenol-contaminated wastewater. A habitat-specific microbial consortium was developed and reconstituted from 22 pure cultures dominated by Acinetobacter sp., Bacillus sp. and Pseudomonas sp. to form a synthetic biofilm-forming community with the capacity to degrade phenol-contaminated wastewater. The laboratory experiment was scaled-up to 400 m³ by using biotrickling reactors to reduce the phenol level from 407 mg L⁻¹ to below detection limit over 104 days incubation. The results showed that the microbial consortia could also reduce the toxicity of the wastewater while degrading the phenol and lowering the wastewater COD. Further, this approach could be translated into the field without the need for a purpose-built primary treatment facility preventing the generation of excessive biomass and eliminating the need for sludge disposal.

The efficiency of phytoremediation is mainly dependent on the capacity of plants in absorption, translocation, and accumulation of Cd. This study was designed to investigate whether Cd translocation and accumulation in tall fescue plants was regulated by foliar application of KH₂PO₄. The results showed that the foliar application of KH₂PO₄ significantly increased Cd concentration and total Cd accumulated in leaves and the capacity of Cd extraction, compared to the root application. The water-soluble organic acid complexes and the pectate- and protein-integrated Cd were the two major Cd chemical forms deposited in leaves. The foliar application increased Cd in the pectate- and protein-integrated forms and decreased the water-soluble forms in leaves. Cd phosphates were not the major chemical forms deposited in leaves in both foliar and root applications. The results indicated that the foliar application of KH₂PO₄ enhanced Cd accumulation in leaves of tall fescue, which might be associated with the leaf deposit of the pectate- and protein-integrated Cd forms.

The establishment of a complementary grass cover on vineyard soils can promote sustainability of the affected environment. In this work, we used an acid vineyard soil with total Cu concentration 188 mg kg⁻¹ to study the influence of pine bark amendment on Lolium perenne growth and Cu uptake. The results indicate that the pine bark amendment did not cause a significant increase in the mass of the shoots of Lolium perenne, but favored the root biomass: 0.034 g for control and 0.061 g for soil samples amended with 48 g kg⁻¹ of pine bark. Moreover, the pine bark amendment decreased Cu concentration in both, shoots (50 mg kg⁻¹ for control soil and 29 mg kg⁻¹ for soil amended with 48 g kg⁻¹ pine bark) and roots (250 mg kg⁻¹ for control soil and 64 mg kg⁻¹ for soil amended with 48 g kg⁻¹ pine bark). The main factor responsible for these results was a significant decrease of the most mobile fractions of Cu in the soil. Those fractions were extracted using ammonium acetate, ammonium chloride, sodium salt of ethylene-diamine-tetraacetic acid (EDTA-Na), and diethylene-triamine-pentaacetic acid (DTPA).

To remove heavy metal contaminations from road runoff prior to discharge into surface water or groundwater, highly porous sorptive filter materials are used. One effective material is a technical product based on granular ferric hydroxide. To specify the removal mechanisms, lab-scale column experiments were performed preloading the material with Cd, Cu, Ni, Pb, and Zn. To identify removal mechanisms and the distribution of heavy metals in the material, investigations with scanning electron microscope (SEM)/energy-dispersive X-ray spectroscopy (EDX) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) were performed. With SEM/EDX, only Pb was detectable; all other heavy metals were not represented on the surface of the particles. To determine the intrusion of the metals, LA-ICP-MS was used. Thereby, the high porosity necessitated a special data evaluation that enabled the determination of the heavy metal removal and the leaching of other elements from the filter material as a function of depth. The measured depth profiles varied for each element and correlated with the metal mobility.