Nitrogen dioxide (NO₂) is one of the major atmospheric pollutants, and the concentration of NO₂ is regarded as one of the indicators of air quality. In the past decades, China has experienced rapid economic growth and severe NO₂ pollution to match. We evaluate the trends and spatiotemporal patterns of tropospheric NO₂ over mainland China from 2005 to 2014 using vertical column density (VCD) datasets retrieved from the Ozone Monitoring Instrument (OMI). Results show that from 2005 to 2014, NO₂ pollution regions have enlarged at the national scale, and high NO₂ VCDs are mainly concentrated over highly populated regions in eastern China. The year 2011 is the turning point. Tropospheric NO₂ VCDs first significantly increase by 0.19 × 10¹⁵ molec cm⁻² year⁻¹ (R ² = 0.94, P = 0.002) from 2005 to 2011, and then decrease by 0.21 × 10¹⁵ molec cm⁻² year⁻¹ (R ² = 0.97, P = 0.016) from 2011 to 2014. Since 2011, tropospheric NO₂ VCDs over central-east China decrease remarkably. Tropospheric NO₂ VCDs is higher in November (3.630 × 10¹⁵ molec/cm²), December (4.758 × 10¹⁵ molec/cm²), and January (4.863 × 10¹⁵ molec/cm²), while lower in July (1.684 × 10¹⁵ molec/cm²), August (1.627 × 10¹⁵ molec/cm²), and September (1.703 × 10¹⁵ molec/cm²), indicating that winter and spring are the most polluted seasons. Due to the huge gap in population density and industry development between western and eastern China, the spatial pattern of tropospheric NO₂ VCDs shows large west-east difference.

Environmental pollution with chromium is due to residues of several industrial processes. Bioremediation is an alternative actually considered to remove Cr (VI) from the environment, using adapted organisms that grow in contaminated places. Have been conducted studies with fungi mechanisms of interaction with chromium, most of which have focused on processes biosorption, characterized it by passive binding of metal components of the cell surface, and bioaccumulation, wherein the metal entry to cells occurs with energy expenditure. The paper presents the results of studies carried out on sorption of chromium (VI) ions from aqueous solutions by Fusarium sp. and Myrothecium sp. Both biomasses have the ability to take up hexavalent chromium during the stationary phase of growth and as well inactive conditions. Fusarium sp. showed 26% of biosorption with active biomass and 64% in inactive biomass; meanwhile, Myrothecium sp. obtained 97 and 82%, respectively. Both fungi showed adjust to pseudo-second-order model in active (Fusarium sp. R ² = 0.99; Myrothecium sp. R ² = 0.96) and inactive biomass assay (Fusarium sp. R ² = 0.99; Myrothecium sp. R ² = 0.99). The data of the active biomass test also confirmed to the intraparticle diffusion model (Fusarium sp. R ² = 0.98; Myrothecium sp. R ² = 0.93). The results obtained through this investigation indicate the possibility of treating waste effluents containing hexavalent chromium using Fusarium sp. and Myrothecium sp.

Biochars, derived from rambutan (Nepheliumlappaceum) peel through slow pyrolysis, were characterised and investigated as potential adsorbent for the removal of copper ion, Cu(II) from aqueous solution. Characteristics of five biochars of rambutan peel with different pyrolytic temperatures ranging from 300 to 700 °C (B300, B400, B500, B600, B700) were studied, and adsorption abilities of respective biochars were evaluated. Adsorption experiments were carried out by varying adsorbent dosage (0.2, 0.4, 0.8, 1.0, 2.0, and 4.0 g/L) and initial copper ion, Cu(II) concentrations (50 and 100 mg/L) to determine the optimum pyrolytic temperature of biochar with high adsorption affinity. The adsorption kinetics were best described by the pseudo-second order model for all the tested biochars, while the adsorption equilibrium best fitted by Langmuir isotherm. The overall results showed that biochar derived at 600 °C can be used as an effective adsorbent for removal of Cu(II) from aqueous solutions. Furthermore, feedforward artificial neural network (FFBP) modelling was performed to compare the simulated results with experimental output data of Thermogravimetric analysis (TGA) and atomic absorption spectroscopy (AAS) analysis which were trained using Levenberg-Marquardt (LM) backpropagation algorithm. The FFBP structure for pyrolysis process comprised of TGA temperature as input and biomass final weight as output. The adsorption modelling was simulated using adsorption time, temperature, biochar dosage and initial Cu(II) concentration as input data, while final Cu(II) concentration was used as output data to the network. Finally, modelling structure of 1-9-1 and 4-8-1 gave best performance with regression, R ² value of 0.9999 and 0.9547 for TGA and AAS analysis, respectively.

Nonlinear sorption of substituted phenols (degradation products of several pesticides) onto soils was often observed. This sorption nonlinearity at low solute concentration ranges could result in higher soil organic carbon-water distribution coefficient (K ₒc) values than those predicted by their hydrophobicity (K ₒw). In this study, nonlinear sorption characteristic of four substituted phenols (2,6-dimethylphenol, 2-chlorophenol, 2-nitrophenol, and 2,4-dichlorophenol) onto two agricultural soils was investigated. The sorption nonlinearity gradually approached apparent saturation at low solute activity ranges (e.g., a ᵢ < 0.01). At high a ᵢ ranges, linear sorption was observed. Thus, partition and adsorption of solutes were successfully evaluated by a dual-mode sorption model. The concentrations of substituted phenols in the environment are pretty low (e.g., usually lower than 1 mg/L). According to our results, nonlinear adsorption is dominant in such low concentration ranges in the environment. To predict varied log K ₒc values resulted from nonlinear adsorption, especially for low a ᵢ range, an expanded polyparameter linear free energy relationship (pp-LFER) is established: log K ₒc = [(1.829 ± 0.488) + (3.481 ± 0.462) log a ᵢ)]E+ [(− 4.307 ± 0.466) log a ᵢ]S+ [(− 0.876 ± 0.138) log a ᵢ]A+ [(− 0.086 ± 0.529) + (1.209 ± 0.218) log a ᵢ]B+ (6.280 ± 0.649)V – (6.814 ± 0.917) (E, the excess molar refraction; S, the dipolarity/polarizability parameter; A, the solute H-bond acidity; B, the solute H-bond basicity; and V, the molar volume). This model can provide a better prediction (within 0.3 log unit) than previous models. This study provides essential parameters for predicting and understanding the environmental behavior of substituted phenols in agricultural soils. Graphical Abstract ᅟ

Road dust impacts almost all terrestrial areas of the planet and may impact vegetation and nearby ecosystems. Therefore, research methods are needed for applying road dust in a controlled manner on targeted areas (e.g. plants). Three dust application methods, sifter, sieve, and sprayer, were investigated for their uniformity in applying dust in a 0.75 m × 0.75 m area. Within the treatment area 196, 37-ml cups were placed in a uniform fashion to collect dust applied at 15.8, 78.8, and 158 g. At the 15.8 and 78.8 g rates, the coefficient of uniformity for each method was >98% indicating a uniform amount of dust applied. At the 158 g rate, the sifter and sieve had coefficient of uniformities >95%, while the sprayer had a significantly lower (p < 0.05) coefficient of uniformity (46%). Although the sifter and sieve were simpler to use and the least expensive options, the sprayer may be more useful when applying dust to larger areas when the exact amount of dust entering and exiting the systems does not need to be controlled. This research is useful to anyone looking to apply road dust or similar sized particulates under controlled field or laboratory conditions.

The aim of this study was to investigate phosphate removal using crushed concrete granules (CCGs). The CCGs were thermally treated at different temperatures (300, 500, 700, and 900 °C) for 3 h under anoxic conditions. The results showed that CCGs thermally treated at 700 °C (700TT-CCGs) were the most effective for the removal of phosphate. The equilibrium adsorption data fitted well the Langmuir isotherm model with a maximum phosphate adsorption capacity of 21.522 mg/g, higher than that of granular adsorbents in the literature. In pH experiments, phosphate adsorption by 700TT-CCGs decreased as initial pH increased from 3 to 5, but sharply increased above pH 5 (final pH 9.1), which was favorable for the formation of calcium phosphate precipitate. The effect of competing anions on phosphate adsorption follows the order: HCO₃⁻ > SO₄²⁻ > NO₃⁻, which is consistent with the reverse order of the shared charge. Column experiments showed no breakthrough of phosphate in the column packed with half 700TT-CCGs and half sand for over 300 h. This study demonstrates that CCGs can be used for phosphate removal from aqueous solution after thermal treatment, which is a simple and cheap way to improve the phosphate removal capacity of CCGs.

The mechanisms involved in immobilization of soil Cu and the role of extracellular polymeric substances (EPS) in Cu(II) adsorption by Bacillus subtilis DBM were investigated in this study. Adsorption and desorption experiments with intact DBM cells revealed that complexation with surface functional groups and intracellular accumulation were involved in the immobilization of soil Cu. The removal of EPS using cation exchange resin resulted in a 26.6% decrease in the Cu(II) adsorption capacity relative to untreated cells. Compared to intact cells, EPS-free cells showed a 9.9% decrease in the proportion of complexed Cu(II), while the intracellular fraction increased by 8.0%. Surface complexation modeling indicated that the total concentration of complexation sites on the intact DBM cell surface was 1.11 mmol/g dry biomass, which was decreased by 17% to 0.92 mmol/g after EPS removal. Infrared analysis revealed that the pKa values of the carboxyl and phosphate groups in the DBM cell wall differed from those in the EPS. Carboxyl, carbonyl, hydroxyl, amino, and phosphate groups were involved in binding Cu(II) by both intact and EPS-free cells, and Cu(II) was more likely to combine with organic rather than inorganic phosphates. The presence of the EPS increased the binding potential of surface functional groups and may help to prevent heavy metals from entering the cells.

Nanoparticles (NPs) have been reported to cause physiological effects on plant cells and tissue. This study traced the uptake and distribution of magnetic iron oxide nanoparticles (γ-Fe₂O₃ NPs) in citrus (Citrus reticulata) plants under hydroponic condition by fluorescent dye labeled γ-Fe₂O₃ NPs, and described a detailed evidence of physiological effects of 0–100 mg/L γ-Fe₂O₃ NPs on citrus plants by measuring the physiological parameters such as content of chlorophyll, malondialdehyde (MDA), soluble sugar, soluble protein, activity of antioxidant enzyme, and ferric reductase after 21 days exposure. Fluorescence images of citrus stem and root showed that citrus roots could absorb γ-Fe₂O₃ NPs but no translocation from roots to shoots was observed, since NPs aggregated or even clogged the vascular system. Physiological results showed that 20 mg/L γ-Fe₂O₃ NPs could significantly enhance chlorophyll content by 126.4%, while 50 and 100 mg/L of γ-Fe₂O₃ NPs decreased chlorophyll content by 27.8 and 35.4%, respectively. MDA contents in citrus leaves under 20–100 mg/L γ-Fe₂O₃ NPs exposure were increased by 37.8, 107.2, and 61.5%, respectively, while that in roots were decreased by 27.0,11.9, and 7.4%, respectively, with elevated SOD and CAT activity, suggesting that oxidative stress occurred in citrus leaves, but oxidative stress in roots was eliminated by antioxidant defense. It is noteworthy that although Fe(II)-EDTA treatment had a high level of chlorophyll content, it induced strong oxidative stress in citrus plants as well. Collectively, the various physiological responses of citrus plants to γ-Fe₂O₃ NPs exposure were closely correlated with the concentrations of NPs. γ-Fe₂O₃ NPs at proper concentrations, such as 20 mg/L, have the potential to ameliorate chlorosis of plants and be effective nanofertilizers for increasing agronomic productivity.

A quantitative microbial risk assessment method can be used to evaluate infections probabilities for microorganisms in a specific place. The methodology provides suitable information to generate strategies focusing on health problems. Giardia cysts (GC) and Cryptosporidium oocysts (CO) are considered emerging pathogens that can infect human and animals by ingesting contaminated food or water, where food and water are transport vehicles for these parasites. Studies for GC and CO have reported occurrences for these parasites in water up to 100%, and some of these studies documented a number of cases, about 403,000 people, infected worldwide. This review is focused on compiling the most relevant works assessing the risk for GC and CO and their presence in different water samples that are susceptible for direct and indirect human consumption. The annual risk infection probability for these parasites has been reported from different water sources, with a range between 1 × 10⁻⁶ and 1, while the world standard regulation is 1 × 10⁻⁴. The infection probability depends not only on water quality but also on water treatment implementations.

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.