In order to successfully establish vegetation on bauxite residue, properties such as aggregate structure and stability require improvement. Spontaneous plant colonization on the deposits in Central China over the last 20 years has revealed that natural processes may improve the physical condition of bauxite residues. Samples from three different stacking ages were selected to determine aggregate formation and stability and its relationship with iron-aluminium oxides and organic carbon. The residue aggregate particles became coarser in both dry and wet sieving processes. The mean weight diameter (MWD) and geometry mean diameter (GMD) increased significantly, and the proportion of aggregate destruction (PAD) decreased. Natural stacking processes could increase aggregate stability and erosion resistant of bauxite residues. Free iron oxides and amorphous aluminium oxides were the major forms in bauxite residues, but there was no significant correlation between the iron-aluminium oxides and aggregate stability. Aromatic-C, alkanes-C, aliphatic-C and alkenes-C were the major functional groups present in the residues. With increasing stacking age, total organic carbon content and aggregate-associated organic carbon both increased. Alkanes-C, aliphatic-C and alkenes-C increased and were mainly distributed in macro-aggregates, whereas aromatic-C was mainly distributed in <0.05-mm aggregates. Organic carbon stability in micro-aggregates was higher than that in macro-aggregates and became more stable. Organic carbon contents in total residues, and within different aggregate sizes, were all negatively correlated with PAD. It indicated that organic materials had a more significant effect on macro-aggregate stability and the effects of iron-aluminium oxides maybe more important for stability of micro-aggregates.

The performance of a field grassed swales (GSs) coupled with wetland detention ponds (WDPs) system was monitored under four typical rainfall events to assess its effectiveness on agricultural runoff pollution control in Taihu Basin, China. The results indicated that suspended solids (SS) derived from the flush process has significant influence on pollution loads in agricultural runoff. Determination of first flush effect (FFE) indicated that total suspended solids (TSS) and total phosphorus (TP) exhibited moderate FFE, while chemical oxygen demand (COD) and total nitrogen (TN) showed weak FFE. Average removal efficiencies of 83.5 ± 4.5, 65.3 ± 6.8, 91.6 ± 3.8, and 81.3 ± 5.8 % for TSS, COD, TN, and TP were achieved, respectively. The GSs played an important role in removing TSS and TP and acted as a pre-treatment process to prevent clogging of the subsequent WDPs. Particle size distributions (PSDs) analysis indicated that coarse particles larger than 75 μm accounted for 80 % by weight of the total particles in the runoff. GSs can effectively reduce coarse particles (≥75 μm) in runoff, while its removal efficiency for fine particles (<75 μm) was low, even minus results being recorded, especially for particles smaller than 25 μm. The length of GSs is a key factor in its performance. The WDPs can remove particles of all sizes by sedimentation. In addition, WDPs can improve water quality due to their buffering and dilution capacity during rainfall as well as their water purification ability during dry periods. Overall, the ecological system of GSs coupled with WDPs is an effective system for agricultural runoff pollution control.

Magnetic polyoxometalate nanohybrid was prepared by the surface modification of γ-Fe₂O₃/SrCO₃ nanoparticles with PW ₁₂ O ₄₀ ³ ⁻ polyoxometalate (POM) anions. The results of Fourier transform infrared (FTIR) and energy-dispersive X-ray (EDX) confirm the presence of POM on the surface of γ-Fe₂O₃/SrCO₃ nanoparticles. TEM results revealed the ellipsoid-like structure of nanohybrid which was 23 nm in length and 6 nm in width. The activity of the photocatalyst was investigated by the photocatalytic degradation of ibuprofen (IBP) in an aqueous solution under solar light. It was found that in comparison with the γ-Fe₂O₃/SrCO₃, the degradation of IBP after 2-h exposure to the solar light irradiation was significantly higher for POM-γ-Fe₂O₃/SrCO₃ nanohybrids. The degradation of IBP was enhanced by the addition of H₂O₂ to the air saturated solution, while the addition of NaHCO₃ and isopropanol restricted the degradation process. In the presence of H₂O₂, the Fenton photocatalyst degradation under solar light irradiation led to relatively complete degradation of IBP. Furthermore, the photocatalytic activity and magnetization properties of this magnetic photocatalyst nanohybrid provide a promising solution for the degradation of water pollutants and photocatalyst recovery. Graphical Abstract Schematic illustration for preparation of POM-γ-Fe₂O₃/SrCO₃ nanohybrid and photocatalytic reaction of IBP on POM-γ-Fe₂O₃/SrCO₃ nanohybrid.

Soil erosion along with soil particles and nutrients losses is detrimental to crop production. We carried out a 5-year (2010 to 2014) study to characterize the soil erosion and nitrogen and phosphorus losses caused by rainfall under different fertilizer application levels in order to provide a theoretical evidence for the agricultural production and coordinate land management to improve ecological environment. The experiment took place under rotation cropping, winter wheat-summer maize, on a 15° slope purple soil in Chongqing (China) within the Three Gorges Region (TGR). Four treatments, control (CK) without fertilizer, combined manure with chemical fertilizer (T1), chemical fertilization (T2), and chemical fertilizer with increasing fertilization (T3), were designed on experimental runoff plots for a long-term observation aiming to study their effects on soil erosion and nutrients losses. The results showed that fertilization reduced surface runoff and nutrient losses as compared to CK. T1, T2, and T3, compared to CK, reduced runoff volume by 35.7, 29.6, and 16.8 %, respectively and sediment yield by 40.5, 20.9, and 49.6 %, respectively. Regression analysis results indicated that there were significant relationships between soil loss and runoff volume in all treatments. The combined manure with chemical fertilizer (T1) treatment highly reduced total nitrogen and total phosphorus losses by 41.2 and 33.33 %, respectively as compared with CK. Through this 5-year experiment, we can conclude that, on the sloping purple soil, the combined application of manure with fertilizer is beneficial for controlling runoff sediments losses and preventing soil erosion.

The action mode of sulfonylurea herbicides is the inhibition of the acetohydroxyacid synthase (AHAS) required for the biosynthesis of amino acids valine and isoleucine in plants. However, this enzyme is also present in a range of non-targeted organisms, among which soil microorganisms are known for their pivotal role in ecosystem functioning. In order to assess microbial toxicity of sulfonylurea herbicide nicosulfuron (NS), a tiered microcosm (Tier I) to field (Tier II) experiment was designed. Soil bacteria harboring AHAS enzyme tolerant to the herbicide nicosulfuron were enumerated, isolated, taxonomically identified, and physiologically characterized. Results suggested that application of nicosulfuron drives the selection towards NS-tolerant bacteria, with increasing levels of exposure inducing an increase in their abundance and diversity in soil. Tolerance to nicosulfuron was shown to be widespread among the microbial community with various bacteria belonging to Firmicutes (Bacillus) and Actinobacteria (Arthrobacter) phyla representing most abundant and diverse clusters. While Arthrobacter bacterial population dominated community evolved under lower (Tier II) nicosulfuron selection pressure, it turns out that Bacillus dominated community evolved under higher (Tier I) nicosulfuron selection pressure. Different NS-tolerant bacteria likewise showed different levels of sensitivity to the nicosulfuron estimated by growth kinetics on nicosulfuron. As evident, Tier I exposure allowed selection of populations able to better cope with nicosulfuron. One could propose that sulfonylureas-tolerant bacterial community could constitute a useful bioindicator of exposure to these herbicides for assessing their ecotoxicity towards soil microorganisms.

In the present study, the trace elements partitioning behavior during cement manufacture process were systemically investigated as well as their distribution behaviors in the soil surrounding a cement plant using hazardous waste as raw materials. In addition to the experimental analysis, the thermodynamic equilibrium calculations were simultaneously conducted. The results demonstrate that in the industrial-scale cement manufacture process, the trace elements can be classified into three groups according to their releasing behaviors. Hg is recognized as a highly volatile element, which almost totally partitions into the vapor phase. Co, Cu, Mn, V, and Cr are considered to be non-volatile elements, which are largely incorporated into the clinker. Meanwhile, Cd, Ba, As, Ni, Pb, and Zn can be classified into semi-volatile elements, as they are trapped into clinker to various degrees. Furthermore, the trace elements emitted into the flue gas can be adsorbed onto the fine particles, transport and deposit in the soil, and it is clarified here that the soil around the cement plant is moderately polluted by Cd, slightly polluted by As, Cr, Ba, Zn, yet rarely influenced by Co, Mn, Ni, Cu, Hg, and V elements. It was also estimated that the addition of wastes can efficiently reduce the consumption of raw materials and energy. The deciphered results can thus provide important insights for estimating the environmental impacts of the cement plant on its surroundings by utilizing wastes as raw materials.

Transformation of inorganic arsenic species has drawn great concern in recent decades because of worldwide and speciation-dependent pollution and the hazards that they pose to the environment and to human health. As(III) photooxidation in aquatic systems has received much attention, but little is known about photochemical transformation of arsenic species on top soil. As(III) photooxidation on natural montmorillonite under UV-A radiation was investigated by using a moisture- and temperature-controlled photochemical chamber with two black-light lamps. Initial As(III) concentration, pH, layer thickness, humic acid (HA) concentration, the presence of additional iron ions, and the contribution of reactive oxygen species (ROS) were examined. The results show that pH values of the clay layers greatly influenced As(III) photooxidation on montmorillonite. As(III) photooxidation followed the Langmuir–Hinshelwood model. HA and additional iron ions greatly promoted photooxidation, but excess Fe(II) competed with As(III) for oxidation by ROS. Scavenging experiments revealed that natural montmorillonite induced the conversion of As(III) to As(V) by generating ROS (mainly HO• and HO₂ •/O₂ •⁻) and that HO• radical was the predominant oxidant in this system. Our work demonstrates that photooxidation on the surface of natural clay minerals in top soil can be important to As(III) transformation. This allows understanding and predicting the speciation and behavior of arsenic on the soil surface.

Considering the time spent in enclosed spaces, indoor air pollutants are of major interest because of its possible impact on health. However, to date, few studies have analysed the air concentrations of a large set of indoor pollutants of respiratory health relevance in dwellings, particularly in Portugal. This study aimed to measure the concentrations of air pollutants that are present in residential buildings and to investigate whether some clustering pattern of indoor air pollutants exists in the dwellings of children with (case group) and without asthma (control group). Measurements were taken in 30 and 38 dwellings of asthmatic and non-asthmatic schoolchildren, respectively, located in the city of Porto, Portugal, during the cold season (October 2012–April 2013), to assess the concentrations of 12 volatile organic compounds (VOC), aldehydes, PM₂.₅, PM₁₀, bacteria and fungi. Toluene, d-limonene, formaldehyde, PM₂.₅, bacteria and fungi are widely present in dwellings, sometimes in relatively high concentrations in reference to WHO guideline values. Moreover, concentrations of CO₂ exceeding 1000 ppm were often encountered, indicating that 70 % of all dwellings had poor ventilation (<4 L/s person). While exposures to common dwelling indoor pollutants are similar for schoolchildren with and without asthma, except for d-limonene levels, the identification and control of VOC and PM sources is important and prudent, especially for vulnerable individuals.

Microbial fuel cells (MFCs) are emerging wastewater treatment systems with a proven potential for denitrification. In this study, we have developed a high-rate denitrifying MFC. The anode consisted of cow manure and fruit waste and the cathode consisted of cow manure and soil. The initial chemical oxygen demand (COD)/nitrate nitrogen (NO₃ ⁻-N) was varied from 2 to 40 at the cathode while keeping the anode ratio fixed at 100. NO₃ ⁻-N removal rate of 7.1 ± 0.9 kg NO₃ ⁻-N/m³ net cathodic compartment (NCC)/day was achieved at cathode COD/NO₃ ⁻-N ratio 7.31 with the current density of 190 ± 9.1 mA/m² and power density of 31.92 ± 4 mW/m² of electrode surface area. We achieved an open-circuit voltage (OCV) of 410 ± 20 mV at initial cathodic NO₃ ⁻-N of 0.345 g/l. The cathode COD/NO₃ ⁻-N ratio had a significant influence on MFC’s OCV and nitrate removal rate. Lower OCV (<150 mV) and NO₃ ⁻-N removal rates were observed at COD/NO₃ ⁻-N ratio >12 and <7. Experiments done at different cathode pH values indicated that the optimum pH for denitrification was 7. Under optimized biochemical conditions, nitrate removal rate of 6.5 kg NO₃ ⁻-N/m³ net cathodic compartment (NCC)/day and power density of 210 mW/m² were achieved in a low resistance MFC. The present study thus demonstrates the utility of MFCs for the treatment of high nitrate wastes.

Pesticides end up in soil where they interact with soil microorganisms in various ways. On the Yin Side of the interaction, pesticides could exert toxicity on soil microorganisms, while on the Yang side of interaction, pesticides could be used as energy source by a fraction of the soil microbial community. The LOVE TO HATE project is an IAPP Marie Curie project which aims to study these complex interactions of pesticides with soil microorganisms and provide novel tools which will be useful both for pesticide regulatory purposes and agricultural use. On the Yin side of the interactions, a new regulatory scheme for assessing the soil microbial toxicity of pesticides will be proposed based on the use of advanced standardized tools and a well-defined experimental tiered scheme. On the Yang side of the interactions, advanced molecular tools like amplicon sequencing and functional metagenomics will be applied to define microbes that are involved in the rapid transformation of pesticides in soils and isolate novel pesticide biocatalysts. In addition, a functional microarray has been designed to estimate the biodegradation genetic potential of the microbial community of agricultural soils for a range of pesticide groups.