Clean-soil Air Water最新文献

This study aims to examine the nitrogen removal characteristics and microbial community variation at low hydraulic retention time (HRT) in a shallow constructed wetland (SCW) using iron–carbon (Fe–C) porous filter material (PFM) as substrate. Effects of influent nitrogen forms and chemical oxygen demand (COD)/N ratio on nitrogen removal performance at HRT of 1 day were investigated. Results showed that total nitrogen (TN) removal declined with the decrease of influent NH₄⁺-N-to-NO₃⁻-N ratio. When the influent NH₄⁺-N/NO₃⁻-N ratio was 0.1, TN removal decreased by 15.4% compared with that at ratio of 2.0. The increase of influent COD/N ratio enhanced NO₃⁻-N reduction, and TN removal reached 74.5% at influent COD/N ratio 7.0. The microbial community was analyzed for the biofilm samples on Fe–C PFM at front (WF), middle (WM), and back (WB) of SCW. Proteobacteria, Bacteroidetes, Chloroflexi, and Firmicutes were dominant bacteria phyla. The relative abundance of genera involved in the nitrification and denitrification decreased with the influent flow. The iron autotrophic denitrifying and macromolecular organics degrading bacteria were abundant in the middle and back of SCW. Microbial nitrification and denitrification, plant uptake, and plant synergism contributed to 86.3%, 7.41%, and 19.9% of N removal, respectively. These results demonstrated that the SCW with Fe–C PFM as substrate was efficient in nitrogen removal at low HRT.

The former Lepanto landfill in the Santiago Metropolitan Region in Central Chile ceased operations in 2002 after 24 years. Currently, a biogas recovery center operates on this site. The objective of this pilot study was to evaluate the atmospheric concentrations of two polycyclic aromatic hydrocarbons (PAHs, i.e., phenanthrene and fluoranthene) at three points downwind from the former Lepanto landfill using passive air samplers and polyurethane foam disks to provide 3-month average concentrations of contaminants during winter months. The results showed concentrations ranging between 2 and 65 ng m⁻³ and decreasing with distance from the former landfill. Given that the distance to other potential sources was similar in all sampling sites, the evidence found suggested that the former Lepanto landfill may contribute to the local PAH inventory. Thus, we suggest that former landfills are potential candidates for long-term monitoring as they can represent a less-known environmental liability for residents. Additionally, we provide insights on how the Chilean environmental protection system can establish reclamation steps for their management after closure.

Excessive industrial release of trace elements may pose a great risk to the environment. Conventional remediation treatments have considerable limitations, making less expensive new technologies an important research area. Batch experiments were conducted at room temperature to investigate the use of two lignite-derived humic products (nano-humus and humic powder) and a cattle manure biochar as adsorbents in the removal of cadmium and zinc from laboratory synthesized water. Nano-humus was most effective in adsorbing Cd(II), wherein 89% adsorption was rapidly achieved in 15 min. The adsorbed amount of Cd(II) and Zn(II) both increased with initial metal ion concentrations from 25 to 125 mg L⁻¹. Despite being produced from the same sources, nano-humus and humic powder showed different properties and adsorption behaviors. The adsorption mechanism of nano-humus followed the Freundlich isotherm model and pseudo-second-order kinetic model, indicating multilayer chemisorption. Humic powder followed the pseudo-second-order kinetic model, although it had a low isotherm model fit, implying chemisorption-dominated adsorption. Cattle manure biochar followed the Freundlich isotherm and pseudo-first-order kinetics model, suggesting diffusion-dominated multilayer adsorption. Of the three adsorbents tested, nano-humus had greatest potential as an effective and inexpensive material for metal remediation.

There are very few reports about water purification and its influence on indigenous microorganisms by effective microorganisms (EM) in the fields. This study investigated the effect of EM on water purification and microbial community via in vitro and field experiments. In in vitro water purification experiments, we examined values for chemical oxygen demand (COD), total phosphorus, and total nitrogen (TN). In systems in which the active EM solutions were at a concentration of less than 1:2000 of the total water sample, the values after 28 days were equal to or lower than those of the control. In systems using 1:200 and 1:100 active EM solutions, COD and TN values were significantly lower in artificial wastewater compared to control. Conversely, they were significantly higher than the control in the pond water. When the active EM solutions were added to the pond water, total microbial plate counts were higher than the control after 28 days for all concentrations of the EM active solutions. Excessive use of EM caused deterioration of water quality and increase of microbial counts. The results of field experiments for 4 years suggested that EM treatment did not purify the pond water, establish introduced EM, or affect indigenous microorganisms.

The present study was conducted to address four key questions: (i) What are the levels of submicron particulate matter at the study area?, (ii) which are the major contributing sources of these particles?, and (iii) is there any seasonal changes in the levels of pollutants at the study site? Thus, the study was conducted at an urban residential site of Jaipur City, India, to determine the elemental and ionic composition of toxic elements associated with PM₁ using inductively coupled plasma optical emission spectroscopy and ion chromatography to reveal specific sources. Monitoring was done for a period of 8 months between October 2020 and May 2021 considering three seasons: winter (December–February), pre-monsoon (March–May), and post-monsoon (October–November). PM₁ samples were found to be highly enriched with Ag, Cd, B, Ni, and Zn. PM₁ mass concentrations were observed to be greater in winter (104.13 ± 30.16 µg m⁻³) and lower in the pre-monsoon season (83.62 ± 19.40 µg m⁻³). Ion concentrations (Cl⁻, NO₃²⁻, and SO₄²⁻) followed a similar pattern to PM₁ concentrations. Source apportionment by positive matrix factorization at the study site revealed six major sources of pollutants (soil dust, agro-based industry, automobile industry, salt aerosols, industrial activities, and biomass burning).

The analysis of UV filters (UVFs) in water has become increasingly important due to their adverse effects on aquatic organisms and humans. This study describes a method for the determination of benzophenone derivatives UVF in wastewater samples. The selected UVFs are 2-hydroxy-4-methoxybenzophenone (BP-3), 2,4-dihydroxybenzophenone (BP-1), 4-hydroxybenzophenone (4HB), 2,2′-dihydroxy-4-methoxybenzophenone (DHMB) and lastly, 4,4′-dihydroxybenzophenone (4DHB). The method includes solid-phase extraction (SPE) of analytes from wastewater followed by on-line derivatization with bis(trimethylsilyl)trifluoroacetamide (BSTFA) and analysis with GC-MS/MS. Method validation studies resulted in good recoveries (86–112%), relative standard deviation RSD = 0.8 and 7.3%, the limits of detection LODs = 1.00–10.8 ng/L, and the limits of quantification LOQs = 3.00–32.3 ng/L. The method was successfully applied to domestic wastewater samples collected from influent and effluent of touristic hotels’ biological wastewater treatment plants. BP-3 (24–1765 ng/L), BP-1 (8–703 ng/L), 4HB (26–96 ng/L), and 4DHB (20–22 ng/L) were the common benzophenone derivatives in the influent wastewater while effluent contained mainly BP-1 (8–32 ng/L), 4HB (12–57 ng/L) and 4DHB (20–102 ng/L). These results indicate that BP-3 and BP-1 are biodegraded in the treatment processes. However, 4HB and 4DHB are resistant to degradation and they are the main benzophenone metabolites discharged to receiving media.