Clean-soil Air Water最新文献

The treatment of leachate from the Antanas Landfill in the municipality of Pasto, Colombia, was evaluated by means of aerobic three-phase airlift fluidized bed reactors with internal circulation (ATPAFBRWIC) with an external and internal diameter ratio of 2 and an individual effective volume of 53 L. Silica sand was used as a carrier at a concentration of 104 g L⁻¹, and the reactors were operated with hydraulic retention times (HRT) of 1, 2 and 4 h. For a period of 45 days, the following parameters were monitored at the influent and effluent of the reactors: biochemical oxygen demand (BOD), chemical oxygen demand (COD), total phosphorus (TP), total ammonia nitrogen (TAN), total Kjeldahl nitrogen, nitrites and nitrates, where the respective average concentrations recorded in the influent were 4225.9, 7115.2, 14.1, 1664.1, 1591.1, 0.41, and 31.8 mg L⁻¹. The best performance in the removal of organic matter and nutrients was recorded for a 2-h HRT, with average removal efficiency of 52.9% for BOD and 26.8% for COD, and 52.5, 5.6, and 56.2% for TP, TAN, and nitrates, respectively. The low volumes required for ATPAFBRWIC suggest their potential use as compact leachate treatment units.

The evaluation of the impact of landuse on soil organic carbon (SOC) is required to understand the long-term productivity and possible sustainability of a landuse system. The effect of landuse on SOC was studied in the Shaheed Bhagat Singh Nagar district of Punjab (India). Surface (0–15 cm) and subsurface (15–30 cm) soil samples were collected under different land uses (cropland, forest, scrubland, and plantation) using stratified random sampling. Soil samples were analyzed for soil texture, bulk density, pH, electrical conductivity, organic carbon, Olsen P (available P), NH₄OAc–extractable K (available K), and CaCl₂ extractable S (available S) using standard methods. Ordinary kriging was used to study the distribution of soil properties in different land uses. Soil organic carbon under future climate was simulated using Rothamsted carbon (RothC) model with current landuse and management practices. Organic carbon in surface and subsurface soils was in the order: Forest > scrubland > plantation > cropland. The content of organic carbon, available P, K, and S decreased with increasing soil depth. The simulated SOC content in cropland soils under future climate may reduce, and in soils under forest, plantation and scrubland may increase by the year 2100. These results suggest that the landuse system is one of the major factors affecting SOC stocks. The study of organic carbon in different landuses could help the famers and policy makers to take measures for increasing SOC stocks to mitigate the climate change and also for sustainable agriculture.

Benzalkonium chloride (BAC) is a quaternary ammonium compound (QAC) widely used as the active ingredient of disinfectants. Its excessive discharge into wastewater is constant and in high concentrations, likely affecting the physiology of microbial communities. We compared the physiological community profile of activated sludge (AS) bacteria with and without prior in vitro exposure to a high concentration of BAC (10 mg L⁻¹). We measured the community functional diversity, carbon substrate multifunctionality, and the median effective concentration that inhibits carbon respiration (EC₅₀) using Biolog EcoPlates supplemented with a gradient of 0–50 mg L⁻¹ of BAC. Surprisingly, we did not find significant differences in the physiological parameters among treatments. Certain abundant bacteria, including Pseudomonas, could explain the community's tolerance to high concentrations of BAC. We suggest that bacterial communities in wastewater treatment plants’ AS are “naturally” adapted to BAC due to frequent and high-dose exposure. We highlight the need to understand better the effects of QACs in wastewater, their impact on the selection of tolerant groups, and the alteration in community metabolic profiles.

Metals in soils exert toxic effects on soil quality and human health. In order to carry out metal contamination assessment and human health risk assessment of agricultural soils, a total of 662 cultivated soil samples were collected from two industrially oriented towns and three agriculturally oriented towns of Shifang City, Southwest China. Various indices were applied to analyze the pollution levels of soils caused by metals (Cr, Fe, Pb, Sr, Ti, V, Zn, and Zr). The relatively high values of the geo-accumulation index (I_geo) and the enrichment factor (EF) suggested that Sr, V, and Zn had cumulative trends in the soils. The average pollution load index (PLI) values of the industrial towns (1.19 and 0.99) were higher than those of the agricultural towns (0.92, 0.53, and 0.43), demonstrating the contribution of industrial activities to soil metal enrichment. The health risk assessment from the five towns indicated that Cr and V were the dominant contaminants in soils with high potential health risks. Dermal contact was the major pathway of the exposure of children and adults to Cr and V. This study improved the understanding of the pollution levels of metals in Shifang agricultural soils and put forward the necessity of minimizing the health risk of Cr and V in agricultural soil.

Garden plants can absorb and retain atmospheric particles and are important for remediating environmental pollution. As an important biological constituent of urban landscape, herbaceous plants can provide ecosystem service such as particulate matter (PM) retention. However, the evaluation of this ecosystem service for herbaceous plants has been seldom made. The present study compared the PM retention capacity of four herbaceous plants commonly used for urban greening in North China—Liriope spicata (Thunb.) Lour., Lolium perenne L., Festuca elata Keng ex E.B.Alexeev, and Poa pratensis L. and explored the correlation between leaf micromorphological traits and PM retention using an in situ experiment. PM with different particle sizes, including PM_>10 (10–100 µm), PM₁₀ (2.5–10 µm), and PM_2.5 (<2.5 µm), were separately evaluated. We found that L. spicata had the greatest PM retention capacity for all particle sizes among the four species. Electron microscopy revealed that leaves with higher groove proportion, larger stomatal size and greater densities of stomata and trichome generally had higher PM retention capacity. The study showed the correlation between leaf micromorphology and PM absorption, providing a scientific basis for further quantitative studies on the ecosystem service of PM absorption provided by herbaceous plants.

In this study, Fe₃O₄@TiO₂ was synthesized by a facile precipitation–impregnation method and applied as a magnetic photocatalyst for degrading synthetic and actual textile dyeing wastewater in the presence of peroxymonosulfate (PMS). In Rhodamine B (RhB) degradation, the removal efficiency reached 99.86% (for RhB) and 93.67% (for color) under optimal operating conditions of 80 mg L^–1 RhB, 0.5 g L^–1 PMS, 0.5 g L^–1 Fe₃O₄@TiO₂, at pH 6, and after 30 min of UVA irradiation. The influence levels of anions on the RhB removal and decolorization were in the order of Cl⁻ < SO₄²⁻ < CO₃²⁻ < PO₄³⁻. In addition, the Fe₃O₄@TiO₂ composite exhibited good applicability for treating other dyes (e.g., 99.6% of tartrazine and 60.3% of methylene blue after 30 min) in water and actual textile dyeing wastewater with high color (70.3% after 5 min) and COD removal (71.4% after 120 min). The radical scavenging tests indicated the role of reactive oxygen species in the order of O₂^•− ∼ ¹O₂ > h⁺ > SO₄^•− > HO^• for RhB degradation but O₂^•− > h⁺ > ¹O₂ > SO₄^•− > HO^• for decolorization. These results suggest the potential application of PMS activation using Fe₃O₄@TiO₂ in the photocatalytic treatment of textile and dyeing wastewater with the dominant role of O₂^•−.

The interactions of six typical antibiotics, including azithromycin, clarithromycin (CLR), ciprofloxacin, sulfathiazole, sulfamethoxazole, and tetracycline (TCY), with Microcystis aeruginosa were investigated, discussing the effects of antibiotics on algal growth in terms of mono- and co-antibiotics, and the removal of six antibiotics by the alga. The results showed that all the antibiotics showed “low-promoting and high-inhibiting” effects, except for sulfonamides, which showed a promotion trend on algal cell density and chlorophyll a. The tests of half effective concentrations (EC₅₀s) of antibiotics against M. aeruginosa showed that the antibiotics of the same category had similar EC₅₀s, and the toxicity effects of co-antibiotics were higher compared to mono-antibiotics. The toxic effects of antibiotics against M. aeruginosa were antagonistic in most binary co-antibiotics, and synergistic and simple additive effects in the ternary co-antibiotics. For removal tests of antibiotics by the alga, it could be seen that at the same concentration (10 µg L⁻¹), M. aeruginosa showed the best removal of TCY with 22.8% and the lowest removal of CLR with only 5.8%. It was found that both antibiotics and M. aeruginosa had mutual influences; therefore, the interaction might be favorable to the permanent removal of antibiotics and reduce the impact on the aquatic ecological environment.

As solid waste of coal-fired power plants, atmospheric environmental pollution is caused by fly ash during transportation. The purpose of this study was to improve the dust removal efficiency of fly ash fine particles by electrocoagulation and obtain reasonable operating parameters. The effects of particle concentration, gas velocity, AC frequency, and voltage on particle electrocoagulation efficiency were studied through the establishment of a discrete element soft sphere calculation model, and reasonable electrocoagulation operation parameters were obtained. The dust removal process was evaluated according to the particle number concentration, electrocoagulation efficiency, and particles microscopic characteristics due to the dust removal experiments of fly ash by electrocoagulation. The results demonstrated that increasing particle concentration, reducing gas velocity, and selecting reasonable AC frequency and voltage were effective to improve the real-time electrocoagulation efficiency and its stability. Under the suitable conditions: voltage of 3 kV, airflow velocity of 5 m s^–1, particle concentration of 30 mg m^–3 and AC frequency of 100 Hz, the electrocoagulation efficiency was higher than 40%. The electrocoagulation was effective to improve the dust removal efficiency of fly ash fine particles with a relative humidity of air below 70% and ambient temperatures above 20°C.