Cover illustration
Front Cover Story (See: Yunpeng Xing, Boyuan Xue, Yongshu Lin, Xueqi Wu, Fang Fang, Peishi Qi, Jinsong Guo, Xiaohong Zhou, 2022, 16(12): 155) Due to the low cost, high versatility, easy miniaturization, and widespread ownership of cellphones, colorimetric analysis technologies for the commercial cellphone platform have got wide attention in in-field rapid environmental monitoring. This work demonstrates a cellphone-based colorimetric multi-channel sensor to detect multiple [Detail] ...
● Health hazards of plastic waste on environment are discussed. ● Microbial species involved in biodegradation of plastics are being reviewed. ● Enzymatic biodegradation mechanism of plastics is outlined. ● Analytical techniques to evaluate the plastic biodegradation are presented.
The abundance of synthetic polymers has increased due to their uncontrolled utilization and disposal in the environment. The recalcitrant nature of plastics leads to accumulation and saturation in the environment, which is a matter of great concern. An exponential rise has been reported in plastic pollution during the corona pandemic because of PPE kits, gloves, and face masks made up of single-use plastics. The physicochemical methods have been employed to degrade synthetic polymers, but these methods have limited efficiency and cause the release of hazardous metabolites or by-products in the environment. Microbial species, isolated from landfills and dumpsites, have utilized plastics as the sole source of carbon, energy, and biomass production. The involvement of microbial strains in plastic degradation is evident as a substantial amount of mineralization has been observed. However, the complete removal of plastic could not be achieved, but it is still effective compared to the pre-existing traditional methods. Therefore, microbial species and the enzymes involved in plastic waste degradation could be utilized as eco-friendly alternatives. Thus, microbial biodegradation approaches have a profound scope to cope with the plastic waste problem in a cost-effective and environmental-friendly manner. Further, microbial degradation can be optimized and combined with physicochemical methods to achieve substantial results. This review summarizes the different microbial species, their genes, biochemical pathways, and enzymes involved in plastic biodegradation.
● Mechanical behavior of MBT waste affected by loading rate was investigated. ● Shear strength ratio of MBT waste increases with an increase in loading rate. ● Cohesion is inversely related to loading rate. ● Internal friction angles are positively related to loading rate. ● MBT waste from China shows smaller range of φ.
Mechanical biological treatment (MBT) technology has attracted increasing attention because it can reduce the volume of waste produced. To deal with the current trend of increasing waste, MBT practices are being adopted to address waste generated in developing urban societies. In this study, a total of 20 specimens of consolidated undrained triaxial tests were conducted on waste obtained from the Hangzhou Tianziling landfill, China, to evaluate the effect of loading rate on the shear strength parameters of MBT waste. The MBT waste samples exhibited an evident strain-hardening behavior, and no peak was observed even when the axial strain exceeded 25%. Further, the shear strength increased with an increase in the loading rate; the effect of loading rate on shear strength under a low confining pressure was greater than that under a high confining pressure. Furthermore, the shear strength parameters of MBT waste were related to the loading rate. The relationship between the cohesion, internal friction angle, and logarithm of the loading rate could be fitted to a linear relationship, which was established in this study. Finally, the ranges of shear strength parameters cohesion c and effective cohesion c ´ were determined as 1.0–8.2 kPa and 2.1–14.9 kPa, respectively; the ranges of the internal friction angle φ and effective internal friction angle φ ´ were determined as 16.2°–29° and 19.8°–43.9°, respectively. These results could be used as a valuable reference for conducting stability analyses of MBT landfills.
● A novel Al-MOF was successfully synthesized by a facile solvothermal method. ● Al-MOF showed superior performance for phosphate detection. ● High selectivity and anti-interference for detection were demonstrated. ● The high coordination between Al-O and PO43− was the key in fluorescence sensing.
The on-site monitoring of phosphate is important for environmental management. Conventional phosphate detection methods are not appropriate to on-site monitoring owing to the use of complicated detection procedures, and the consequent high cost and maintenance requirements of the detection apparatus. Here, a highly sensitive fluorescence-based method for phosphate detection with a wide detection range was developed based on a luminescent aluminum-based metal-organic framework (Al-MOF). The Al-MOF was prepared by introducing amine functional groups to conventional MIL to enhance phosphate binding, and exhibited excellent fluorescence properties that originated from the ligand-to-metal charge transfer (LMCT). The detection limit was as low as 3.25 μmol/L (0.10 mg/L) and the detection range was as wide as 3–350 μmol/L (0.10–10.85 mg/L). Moreover, Al-MOF displayed specific recognition toward phosphate over most anions and metal cations, even for a high concentration of the co-existent ions. The mechanism of phosphate detection was analyzed through the characterization of the combination of Al-MOF and phosphate, and the results indicated the high affinity between Al-O and phosphate inhibited that the LMCT process and recovered the intrinsic fluorescence of NH2-H2BDC. The recovery of the developed detection method reached a satisfactory range of 85.1%–111.0%, and the feasibility of on-site phosphate detection was verified using a prototype sensor for tap water and lake water samples. It was demonstrated that the prepared Al-MOF is highly promising for on-site detection of phosphate in an aqueous environment.
● The airborne bacteria in landfills were 4–50 times higher than fungi. ● Bioaerosols released from the working area would pose risk to on-site workers. ● The safe distance for the working area should be set as 80 m.
Landfills are widely complained about due to the long-term odor and landfill gas emissions for local residents, while the bioaerosols are always neglected as another threat to on-site workers. In this study, bioaerosols samples were collected from the typical operation scenes in the large-scale modern landfill, and the emission levels of airborne bacteria, pathogenic species, and fungi were quantified and co-related. The corresponding exposure risks were assessed based on the average daily dose via inhalation and skin contact. It was found that the levels of culturable bacteria and fungi in all landfill samples were around 33–22778 CFU/m3 and 8–450 CFU/m3, and the active-working landfill area and the covered area were the maximum and minimum emission sources, respectively, meaning that the bioaerosols were mainly released from the areas related with the fresh waste operation. Acinetobacter sp., Massilia sp., Methylobacterium-Methylorubrum sp. and Noviherbaspirillum sp. were the main bacterial populations, with a percentage of 42.56%, 89.82%, 70.24% and 30.20% respectively in total bioaerosols measured. With regards to the health risk, the health risks via inhalation were the main potential risks, with four orders of magnitude higher than that of skin contact. Active-working area showed the critical point for non-carcinogenic risks, with a hazard quotient of 1.68, where 80 m protection distance is recommended for on-site worker protection, plus more careful protection measures.
● Fermentation broth facilitates N removal and energy yields in tertiary CW-MFC. ● Carbon sources are preferred for nitrogen removal over electricity generation. ● A mutual promotion relationship exists between acetic and humic acid in N removal. ● Humic acid boosts the abundances of functional genes relate to nitrogen metabolism.
Constructed wetlands (CWs) are widely used as a tertiary treatment technology, and the addition of carbon sources can significantly improve advanced nitrogen removal. However, excessive carbon sources would lead to an increase in the effluent chemical oxygen demand in CWs, and microbial fuel cells (MFCs) can convert these into electricity. In this study, constructed wetland-microbial fuel cells (CW-MFCs) were built to achieve simultaneous nitrogen removal and electricity generation, using wetland plant litter fermentation broths as carbon sources. The total nitrogen removal in the groups with fermentation broth addition (FGs) reached 83.33%, which was 19.64% higher than that in the CG (group without fermentation broth), and the mean voltages in the FGs were at least 2.6 times higher than that of the CG. Furthermore, two main components of the fermentation broths, acetic acid (Ac) and humic acid (HA), were identified using a three-dimensional excitation emission matrix and gas chromatograph and added to CW-MFCs to explore the influence mechanism on the treatment performance. Denitrification and electrogenesis presented the same tendency: Ac&HA > Ac > CG’ (groups without Ac and HA). These results indicate that Ac and HA increased the abundance of functional genes associated with nitrogen metabolism and electron transfer. This study demonstrated that CW-MFC fermentation broth addition can be a potential strategy for the disposal of secondary effluent and bioelectricity generation.
● A novel PRB configuration based on passive convergent flow effect was proposed. ● A 2D finite-difference hydrodynamic model, PRB-Flow, was developed. ● PC-PRB can significantly enhance the hydraulic capture capacity of PRB. ● The PRB geometric dimensions and materials cost are effectively reduced. ● The dominant influential factor of the PC-PRB capture width is pipe length, Lp.
A novel permeable reactive barrier (PRB) configuration, the so-called passive convergence-permeable reactive barrier (PC-PRB), is proposed to overcome several shortcomings of traditional PRB configurations, such as high dependency to site hydrogeological characteristics and plume size. The PC-PRB is designed to make the plume converge towards the PRB due to the passive hydraulic decompression-convergent flow effect. The corresponding passive groundwater convergence (PC) system is deployed upstream of the PRB system, which consists of passive wells, water pipes, and a buffer layer. A two-dimensional (2D) finite-difference hydrodynamic code, entitled PRB-Flow, is developed to examine the hydraulic performance parameters (i.e., capture width (W) and residence time (t)) of PC-PRB. It is proved that the horizontal 2D capture width (Wh) and vertical 2D capture depth (Wv) of the PC-PRB remarkably increase compared to that of the continuous reactive barrier (C-PRB). The aforementioned relative growth values in order are greater than 50% and 25% in this case study. Therefore, the PRB geometric dimensions as well as the materials cost required for the same plume treatment lessens. The sensitivity analysis reveals that the dominant factors influencing the hydraulic performance of the PC-PRB are the water pipe length (Lp), PRB length (LPRB), passive well height (Hw), and PRB height (HPRB). The discrepancy between the Wh of PC-PRB and that of the C-PRB (i.e., ΔWh) has a low correlation with PRB parameters and mainly depends on Lp, which could dramatically simplify the PC-PRB design procedure. Generally, the proposed PC-PRB exhibits an effective PRB configuration to enhance hydraulic performance.
● A cellphone-based colorimetric multi-channel sensor for in-field detection. ● A universal colorimetric detection platform in the absorbance range of 400–700 nm. ● Six-fold improvement of sensitivity by introducing a transmission grating. ● Quantifying multiple water quality indexes simultaneously with high stability.
The development of colorimetric analysis technologies for the commercial cellphone platform has attracted great attention in environmental monitoring due to the low cost, high versatility, easy miniaturization, and widespread ownership of cellphones. This work demonstrates a cellphone-based colorimetric multi-channel sensor for quantifying multiple environmental contaminants simultaneously with high sensitivity and stability. To improve the sensitivity of the sensor, a delicate optical path system was created by using a diffraction grating to split six white beams transmitting through the multiple colored samples, which allows the cellphone CMOS camera to capture the diffracted light for image analysis. The proposed sensor is a universal colorimetric detection platform for a variety of environmental contaminants with the colorimetry assay in the range of 400–700 nm. By introducing the diffraction grating for splitting light, the sensitivity was improved by over six folds compared with a system that directly photographed transmitted light. As a successful proof-of-concept, the sensor was used to detect turbidity, orthophosphate, ammonia nitrogen and three heavy metals simultaneously with high sensitivity (turbidity: detection limit of 1.3 NTU, linear range of 5–400 NTU; ammonia nitrogen: 0.014 mg/L, 0.05–5 mg/L; orthophosphate: 0.028 mg/L, 0.1–10 mg/L; Cr (VI): 0.0069 mg/L, 0.01–0.5 mg/L; Fe: 0.025 mg/L, 0.1–2 mg/L; Zn: 0.032 mg/L, 0.05–2 mg/L) and reliability (relative standard deviations of six parallel measurements of 0.37%–1.60% and recoveries of 95.5%–106.0% in surface water). The miniature sensor demonstrated in-field sensing ability in environmental monitoring, which can be extended to point-of-care diagnosis and food safety control.
● A series of mixed-LOFs and portable LOF-fibers were synthesized. ● LOF-S3 was selected as a luminescent sensor for antibiotics. ● Mixed-LOF was capable of decoding antibiotics by emission intensity ratios. ● Linear relationship between antibiotic concentration and I545nm/I618nm was observed.
Due to the potential risk of antibiotics to the environment, the development of inexpensive, simple, and reliable antibiotic detection methods is significant but also faces challenges. In this work, several lanthanide-organic frameworks (LOFs), constructed from lanthanide ions (Eu3+ and/or Tb3+) and 1,3,5-benzene-tricarboxylic acid (BTC), were synthesized by solvothermal method. LOF-S3 with comparable emission peaks of 5D4 → 7F5 (Tb3+, 545 nm) and 5D0 → 7F2 (Eu3+, 618 nm) was selected as a luminescent sensor. In this system, the highly efficient energy transferred from the organic linker to lanthanide ions and from Tb3+ to Eu3+ occurs. LOF-S3 sensor was capable of decoding antibiotics by distinguishable emission intensity ratios. Therefore, a two-dimensional decoded map of antibiotics was established. The linear relationship between antibiotic concentration and emission intensity ratio indicated the quantitative determination of antibiotics was feasible. As a typical analyte, the response mechanism of nalidixic acid (NA) was investigated in detail. The competition of NA and BTC for UV light absorption, as well as the binding propensity of NA and Tb, affected the organic linkers-to-lanthanide ions and Tb-to-Eu energy transfer, resulting in the change of fluorescence intensity ratio. The self-calibrating mixed-LOF sensor overcame the uncontrollable errors of the traditional absolute emission intensity method and generated stable luminescent signals in multiple cycles. Furthermore, the integration of LOF-S3 with polymer fibers enabled the formation of a LOF-polymer fibrous composite with fluorescence detection capability, which is a promising portable sensor for practical applications.
● A PAA-ZnO-HDTMS flax fiber with UV-induced switchable wettability was developed. ● The property of flax fiber could be switched from hydrophobicity to hydrophilicity. ● The mechanism of the acquired UV-induced switchable wettability was discussed. ● The developed flax fiber was successfully used for multipurpose oil-water separation.
The large number of oily wastewater discharges and oil spills are bringing about severe threats to environment and human health. Corresponding to this challenge, a functional PAA-ZnO-HDTMS flax fiber with UV-induced switchable wettability was developed for efficient oil-water separation in this study. The developed flax fiber was obtained through PAA grafted polymerization and then ZnO-HDTMS nanocomposite immobilization. The as-prepared PAA-ZnO-HDTMS flax fiber was hydrophobic initially and could be switched to hydrophilic through UV irradiation. Its hydrophobicity could be easily recovered through being stored in dark environment for several days. To optimize the performance of the PAA-ZnO-HDTMS flax fiber, the effects of ZnO and HDTMS concentrations on its switchable wettability were investigated. The optimized PAA-ZnO-HDTMS flax fiber had a large water contact angle (~130°) in air and an extremely small oil contact angle (~0°) underwater initially. After UV treatment, the water contact angle was decreased to 30°, while the underwater oil contact angle was increased to more than 150°. Based on this UV-induced switchable wettability, the developed PAA-ZnO-HDTMS flax fiber was applied to remove oil from immiscible oil-water mixtures and oil-in-water emulsion with great reusability for multiple cycles. Thus, the developed flax fiber could be further fabricated into oil barrier or oil sorbent for oil-water separation, which could be an environmentally-friendly alternative in oil spill response and oily wastewater treatment.
● China’s implementation of the SC was systematically studied. ● Implementation process of the SC can be roughly divided into three stages. ● DDT and HCH concentrations in the air have been steadily decreasing. ● China has safely disposed of 6352.1 tons of pesticide POPs.
Persistent organic pollutants (POPs) are extremely harmful to the environment and human health; the Stockholm Convention on Persistent Organic Pollutants was therefore adopted by the international community in 2001 to eliminate or reduce the production, use, and emissions of POPs. China is the largest developing country that has signed the Stockholm Convention, and thus plays an important role in its implementation. This paper systematically studies the practice and achievements of China since it signed the Stockholm Convention 20 years ago. China has established an implementation guarantee system including institutions, implementation mechanisms, policies, law enforcement, and scientific and technological support. During the 20 years since the implementation of the Stockholm Convention, dichlorodiphenyltrichloroethane (DDT) and hexachlorocyclohexane (HCH) concentrations in the air have been steadily decreasing, and Perfluorooctane sulfonic acid/Perfluorooctane sulfonyl fluoride (PFOS/PFOSF) concentrations in water bodies have decreased. In the past 20 years, China has safely disposed of 6352.1 tons of pesticide persistent organic pollutants and 36998 sets of electrical equipment containing polychlorinated biphenyls (PCBs), with a disposal rate of 100%. In the future, China will further strengthen the construction of persistent organic pollutant monitoring networks, scientific research, publicity, education, and international cooperation to improve environmental quality, providing a reference for other countries to implement the Stockholm Convention.
● nZVI, S-nZVI, and nFeS were systematically compared for Cd(II) removal. ● Cd(II) removal by nZVI involved coprecipitation, complexation, and reduction. ● The predominant reaction for Cd(II) removal by S-nZVI and nFeS was replacement. ● A simple pseudo-second-order kinetic can adequately fit Fe(II) dissolution.
Cadmium (Cd) is a common toxic heavy metal in the environment. Taking Cd(II) as a target contaminant, we systematically compared the performances of three Fe-based nanomaterials (nano zero valent iron, nZVI; sulfidated nZVI, S-nZVI; and nano FeS, nFeS) for Cd immobilization under anaerobic conditions. Effects of nanomaterials doses, initial pH, co-existing ions, and humic acid (HA) were examined. Under identical conditions, at varied doses or initial pH, Cd(II) removal by three materials followed the order of S-nZVI > nFeS > nZVI. At pH 6, the Cd(II) removal within 24 hours for S-nZVI, nFeS, and nZVI (dose of 20 mg/L) were 93.50%, 89.12% and 4.10%, respectively. The fast initial reaction rate of nZVI did not lead to a high removal capacity. The Cd removal was slightly impacted or even improved with co-existing ions (at 50 mg/L or 200 mg/L) or HA (at 2 mg/L or 20 mg/L). Characterization results revealed that nZVI immobilized Cd through coprecipitation, surface complexation, and reduction, whereas the mechanisms for sulfidated materials involved replacement, coprecipitation, and surface complexation, with replacement as the predominant reaction. A strong linear correlation between Cd(II) removal and Fe(II) dissolution was observed, and we proposed a novel pseudo-second-order kinetic model to simulate Fe(II) dissolution.
● The physicochemical and structural properties of DBC were characterized. ● The effects of DBC on DBPs and DBPFP generation during disinfection were evaluated. ● The DBPs and DBPFP generation during chlor(am)ination were compared.
Dissolved black carbon (DBC) released from biochar can be one of the potential disinfection by-products (DBPs) precursors in the dissolved organic matter pool. However, the physiochemical and structural properties of DBC and the effects on the development of DBPs and DBP formation potential (DBPFP) during the disinfection process remain unclear. In this study, the characteristics of two kinds of DBC, namely, animal-derived DBC (poultry litter DBC, PL-DBC) and plant-derived DBC (wheat straw DBC, WS-DBC), were investigated. The effects of different kinds of DBC on the evolution of DBPs and DBPFP in chlorine and chloramine disinfection processes were compared with natural organic matter (NOM). The results showed that the total DBPs concentrations derived from PL-DBC, WS-DBC and NOM were similar during chlorination (i.e., 61.23 μg/L, 64.59 μg/L and 64.66 μg/L, respectively) and chloramination (i.e., 44.63 μg/L, 44.42 μg/L and 45.58 μg/L, respectively). The lower total DBPs and DBPFP concentrations in chloramination could be attributed to the fact that the introduction of ammonia in chloramine inhibited the breaking of the bond between the disinfectant and the active group of the precursor. Additionally, DBC presented much lower total DBPFP concentrations than NOM in both chlorination and chloramination. However, both kinds of DBC tended to form more monochloroacetic acids and haloacetamides than NOM, which could result from the higher organic strength, higher protein matter, and nitrogen-rich soluble microbial products of DBC.
