Microbial removal of C and N in soil-based wastewater treatment involves emission of CO₂, CH₄, N₂O, and N₂ to the atmosphere. Water-filled pore space (WFPS) can exert an important control on microbial production and consumption of these gases. We examined the impact of WFPS on emissions of CO₂, CH₄, N₂O, and N₂ in soil microcosms receiving septic tank effluent (STE) or effluent from a single-pass sand filter (SFE), with deionized-distilled (DW) water as a control. Incubation of B and C horizon soil for 1 h (the residence time of wastewater in 1 cm of soil) with DW produced the lowest greenhouse gas (GHG) emissions, which varied little with WFPS. In B and C horizon soil amended with SFE emissions of N₂O increased linearly with increasing WFPS. Emissions of CO₂ from soil amended with STE peaked at WFPS of 0.5–0.8, depending on the soil horizon, whereas in soil amended with SFE, the CO₂ flux was detectable only in B horizon soil, where it increased with increasing WFPS. Methane emissions were detectable only for STE, with flux increasing linearly with WFPS in C horizon soil, but no clear pattern was observed with WFPS for B horizon soil. Emissions of GHG from soil were not constrained by the lack of organic C availability in SFE, or by the absence of NO₃ availability in STE, and addition of acetate or NO₃ resulted in lower emissions in a number of instances. Emission of ¹⁵N₂ and ¹⁵N₂O from ¹⁵NH₄ took place within an hour of contact with soil, and production of ¹⁵N₂ was much higher than ¹⁵N₂O. ¹⁵N₂ emissions were greatest at the lowest WFPS value and diminished markedly as WFPS increased, regardless of water type and soil texture. Our results suggest that the fluxes of CO₂, CH₄, N₂O, and N₂ respond differently to WFPS, depending on water type and soil texture.

Biopurification systems (BPS) are employed for the treatment of pesticide-containing wastewaters. In this work, a biomixture (active core of BPS) complemented by the addition of the fungus Trametes versicolor was evaluated for the elimination of a mixture of pesticides under different treatment conditions. The biomixture achieved high removal of all the pesticides assayed after 16 d: atrazine (68.4%, t₁/₂: 9.6 d), carbendazim (96.7%, t₁/₂: 3.6 d), carbofuran (98.7%, t₁/₂: 3.1 d) and metalaxyl (96.7%, t₁/₂: 3.8 d). Variations in the treatment conditions including addition of the antibiotic oxytetracycline and co-bioaugmentation with a bacterial consortium did not significantly affect the removal performance of the biomixture. Bacterial and fungal community profiles determined by DGGE analyses revealed changes that responded to biomixture aging, and not to antibiotic or pesticide addition. The proposed biomixture exhibits very efficient elimination during simultaneous pesticide application; moreover, the matrix is highly stable during stressful conditions such as the co-application of antibiotics of agricultural use.

The effects of increased mining of seafloor massive sulfide deposits on marine ecosystems have not been characterized. In this study, the impact of leaching metals from a hydrothermal sulfide on photosynthetic protist and cyanobacterial communities in marine environments was investigated by amplicon analyses of small subunit rDNA (SSU rDNA) and rRNA (SSU rRNA). Seawater samples collected from the Iheya North region and Suruga Bay, Japan, were incubated with or without a leachate containing zinc, copper, cadmium, and manganese, of the actual seafloor hydrothermal sulfide from the Hakurei site in the Izena Hole region. The relative abundances of prasinophytes, diatom protists, and the cyanobacteria Synechococcus decreased substantially during incubation with leachate, indicating the vulnerability of these lineages to the leachate. Phylogenetic analysis based on the cyanobacterial phycocyanin cpcBA/rpcBA operon obtained from samples incubated with or without leachate indicated that the individual lineages of Synechococcus can determine sensitivity to heavy metals in different marine regions as well as particular clades and ecotypes.

The photolysis of bis(2-ethylhexyl) phthalate (DEHP) under simulated sunlight in the presence of the natural water photoreactive constituents was investigated. The presence of nitrate or ferric ions facilitated the photodegradation of DEHP via oxidation by generation of •OH. The fulvic acids (FAs), at low concentrations, promoted the photolysis of DEHP via energy transfer from the photoreaction-generated ³FA*. However, the DEHP photolysis was inhibited with high concentrations of FAs since the excess FAs at the surface of solution could act as light screening agents to keep FAs in bulk solution from the light irradiation, further reducing the ³FA* generation. When low concentrations of FAs and chloride ions coexist, the reactive chloride species Cl• and Cl₂•⁻ could generate via energy transfer from ³FA* to chloride ions and react with DEHP to enhance its degradation. Furthermore, the direct and •OH-initiated DEHP photodegraded intermediates and end products were identified by HPLC-MS² and its corresponding photolysis pathways were proposed.

The use of pyrolysis to produce oil from sludge by the evaporation–condensation process is a promising technique. However, the resulting lipids are prone to be acidized under exposure to oxygen, which can affect their quality and use. To eliminate the need for this oil separation process, the present work uses blended pyrolysis to preserve the oil in the char and to prevent it from deteriorating. At the same time, metals are eliminated to a secure level of combustion emissions. The sludge was pyrolyzed into a sintering fuel through blended pyrolysis with SiO₂, Al₂O₃, and sand. These materials are the main components of the sintered ceramsite obtained. Therefore, the influence of these substances and residence time on lipid formation and metal residue in the char were investigated. Non-blended pyrolysis required a 40-min duration, whereas sand-pyrolysis required 10 min to achieve the same yield. The concentration of C₁₆:₀ produced by blended pyrolysis with sand reached 2177 mg kg⁻¹, which is 57% higher than that of non-blended pyrolysis. Blended pyrolysis with SiO₂ required at least 20 min to immobilize As metal. In summary, blended pyrolysis simplifies the process, reduces time, and produces char with lipid-rich and low metal leaching, which can be used as a sintering fuel.

Nitrogen loss in karst sloping farmland will lead to declining land productivity and environmental pollution, in which the nitrogen loss through underground pore fissures will directly lead to groundwater pollution. The characteristics of total nitrogen (TN) production were studied by simulating the “dual structure” microenvironment of sloping farmland in a karst region using an artificial rainfall simulation method. The results show that rainfall was the main driving factor of TN loss in karst sloping farmland. TN was mainly lost through underground pore fissures when the rainfall intensity was ≤ 30 mm · h⁻¹. TN was lost at the surface and underground when the rainfall intensity was ≥ 50 mm · h⁻¹, TN loss on the surface accounted for a large proportion, and the surface flow was the main carrier of TN loss. The TN loss underground is easily ignored because it is hidden underground. Therefore, TN loss belowground in karst sloping farmland should receive increased attention. It would be interesting to explore the influences of connectivity and type of underground pore fissure system on TN loss in karst sloping farmland. The prevention and control of TN loss in karst sloping farmland should be considered both at the surface and underground. Reducing the formation of slope flows and slowing rainwater filtration by increasing slope vegetation coverage can be considered to reduce TN loss. The results of this study provide a theoretical reference for agricultural non-point source pollution control in a karst region. Graphical abstract

This study was aimed to investigate the adsorption and fixation effects of hydroxyapatite (HAP) on lead-contaminated soil. According to the experimental results, the microstructure of hydroxyapatite was observed by a scanning electron microscope (SEM). Fourier transform infrared spectroscopy (FTIR) showed that OH⁻ and PO₄³⁻ were the main functional groups in HAP. Optimum adsorption conditions of Pb²⁺ were obtained: 0.2 g/L, adsorbent; initial solution pH of 5.5; and contact time of 120 min. The kinetic adsorption experiments were carried out with the initial lead solution concentrations of 50 mg/L, 150 mg/L, and 250 mg/L. The kinetics fitting was consistent with the pseudo-second-kinetic model, which indicated that the main process of HAP adsorption of Pb²⁺ was mainly controlled by surface reactions and chemical reactions. The adsorption isotherms had a satisfactory fit with the Langmuir model, which indicated that the adsorption of Pb²⁺ by HAP was a monolayer adsorption. According to the experimental results, ion exchange, phosphorus supply, precipitate, and complexation are the main immobilization mechanisms for soil remediation with HAP. In remediation of Pb²⁺-contaminated soil experiments, the adsorption rate of Pb²⁺ by HAP was significantly higher than that of non-HAP soil with increasing immobilization days. With the increasing addition of HAP, the weak acid soluble (WA), reducible (RED), oxidizable (OX), and water soluble (WS) are transformed into residue (RES). The application of HAP in contaminated soil effectively reduced the leachable and exchangeable Pb²⁺, indicating that HAP is a potential material for remediating environmental pollution with Pb²⁺.

In this study, a high sensitive metamaterial sensor has been designed to detect quality of water for water treatment centre. The water samples have been obtained and electrical properties have been measured in microwave range to design the proposed sensor. These electrical properties have been assigned in microwave simulator. Water quality has been investigated by using parametric study and genetic algorithm approach to realize high sensitivity in terms of resonance frequency shift. Around 130 MHz frequency shift has been observed between the water samples. This shift is sufficient to detect instantaneously to the quality of water. This is the first study that metamaterial approach has been used to detect water quality in literature.

In this study, we investigated the effect of olive mill wastewater on selected soil physical and hydraulic properties. Olive mill wastewater was added to each column every week at different loading rates (0, 50, 100, and 200 m³ ha⁻¹). Physicochemical and hydraulic properties were determined for surface (0–8 cm) and subsurface layers (8–16 and 16–24 cm). The highest loading rate (200 m³ ha⁻¹) showed an increase in aggregate stability from 18% (control) to 31 and to 38%, penetration resistance from 1.8 kg cm⁻² (control) to 3.5 and to 4.5 kg cm⁻², hydraulic conductivity from 43 cm day⁻¹ (control) to 15.3 and 3.3 cm day⁻¹, and water repellency from < 5 s (control) to 120 and 261 s in the first and second months for the surface layer, respectively. The opposite was observed for the infiltration rate, where it decreased from 39.01 mm h⁻¹ (control) to 1.26 and 0.42 mm h⁻¹ for the first and second months, respectively. This study showed that application of olive mill wastewater deteriorated the physical and hydraulic properties of soil proportional to loading rates and more specifically at the surface layer.

The study explores the relationship between ecological footprint, urbanization, and energy consumption by applying the ARDL estimation technique on data spanning 1965–2014 for South Africa. After applying the unit root test that accounts for a break in the data, the Bayer and Hanck (J Time Ser Anal 34:83–95, 2013) combined cointegration test affirms cointegrating relationship among the variables. Findings further reveal that economic growth and financial development exact a deteriorating impact on the environment in the short run. However, the same was not true for both energy use and urbanization. While urbanization and energy use promote environmental quality in the long run, financial development and economic growth degrade it further. The long-run findings of our study are confirmed to be robust as reported by the fully modified OLS (FMOLS), dynamic OLS (DOLS), and the canonical cointegrating regression (CCR) estimates. The direction of causality supports the energy-led growth hypothesis for South Africa. Policy outcomes and directions, and the possibility of promoting sustainable growth without degrading the environment are discussed.