Short-term inhalation exposure evaluations of airborne antibiotic resistance genes in environments

Antibiotic resistance is a sword of Damocles that hangs over humans. In regards to airborne antibiotic resistance genes (AARGs), critical knowledge gaps still exist in the identification of hotspots and quantification of exposure levels in different environments. Here, we have studied the profiles of AARGs, mobile genetic elements (MGEs) and bacterial communities in various atmospheric environments by high throughput qPCR and 16S rRNA gene sequencing. We propose a new AARGs exposure dose calculation that uses short-term inhalation (STI). Swine farms and hospitals were high-risk areas where AARGs standardised abundance was more abundant than suburbs and urban areas. Additionally, resistance gene abundance in swine farm worker sputum was higher than that in healthy individuals in other environments. The correlation between AARGs with MGEs and bacteria was strong in suburbs but weak in livestock farms and hospitals. STI exposure analysis revealed that occupational intake of AARGs (via PM₁₀) in swine farms and hospitals were 110 and 29 times higher than in suburbs, were 1.5 × 10⁴, 5.6 × 10⁴ and 5.1 × 10² copies, i.e., 61.9%, 75.1% and 10.7% of the overall daily inhalation intake, respectively. Our study comprehensively compares environmental differences in AARGs to identify high-risk areas, and forwardly proposes the STI exposure dose of AARGs to guide risk assessment.     

Dosing low-level ferrous iron in coagulation enhances the removal of micropollutants, chlorite and chlorate during advanced water treatment

Drinking water utilities are interested in upgrading their treatment facilities to enhance micropollutant removal and byproduct control. Pre-oxidation by chlorine dioxide (ClO₂) followed by coagulation-flocculation-sedimentation and advanced oxidation processes (AOPs) is one of the promising solutions. However, the chlorite (ClO₂^–) formed from the ClO₂ pre-oxidation stage cannot be removed by the conventional coagulation process using aluminum sulfate. ClO₂^– negatively affects the post-UV/chlorine process due to its strong radical scavenging effect, and it also enhances the formation of chlorate (ClO₃^–). In this study, dosing micromolar-level ferrous iron (Fe(II)) into aluminum-based coagulants was proposed to eliminate the ClO₂^– generated from ClO₂ pre-oxidation and benefit the post-UV/chlorine process in radical production and ClO₃^– reduction. Results showed that the addition of 52.1-µmol/L FeSO₄ effectively eliminated the ClO₂^– generated from the pre-oxidation using 1.0 mg/L (14.8 µmol/L) of ClO₂. Reduction of ClO₂^– increased the degradation rate constant of a model micropollutant (carbamazepine) by 55.0% in the post-UV/chlorine process. The enhanced degradation was verified to be attributed to the increased steady-state concentrations of HO^· and ClO^· by Fe(II) addition. Moreover, Fe(II) addition also decreased the ClO₃^– formation by 53.8% in the UV/chlorine process and its impact on the formation of chloro-organic byproducts was rather minor. The findings demonstrated a promising strategy to improve the drinking water quality and safety by adding low-level Fe(II) in coagulation in an advanced drinking water treatment train.     

Interactions between lead(II) ions and dissolved organic matter derived from organic fertilizers incubated in the field

This work was to study composition characteristics and the subsequent effect on the lead (Pb) binding properties of dissolved organic matter (DOM) derived from seaweed-based (SWOF) and chicken manure organic fertilizers (CMOF) during a one-year field incubation experiment using the excitation-emission matrix-parallel factor (EEM-PARAFAC) and two-dimensional correlation spectroscopy (2DCOS) analysis. Results showed that high aromatic and hydrophobic fluorescent substances were enriched in CMOF-derived DOM and SWOF-derived DOM and enhanced over time. And phenolic groups in the fulvic-like substances for SWOF-derived DOM and carboxyl groups in the humic-like substances for CMOF-derived DOM had the fastest responses over time, respectively. Moreover, both non-fluorescent polysaccharides and fluorescent humic-like substances or fulvic-like substances with aromatic (C=C) groups first participated in the binding process of Pb to SWOF-derived DOM on day 0 and 180 during the lead binding process. In contrast, humic-like substances associated with aromatic (C=C) and phenolic groups gave a faster response to Pb binding on day 360. Regarding CMOF-derived DOM, the fulvic-like substances associated with aromatic (C=C) and carboxylic groups displayed a faster response to Pb ions on day 0. Nonetheless, polysaccharides and humic-like associated with phenolic groups had a faster response on days 180 and 360. It is noteworthy that the polysaccharides, which participated in Pb binding to CMOF-derived DOM, posed a higher risk of Pb in the environment after 360 days. Therefore, these findings gave new insights into the long-term applications of commercial organic fertilizers for the amendment of soil.     

Enhancing anoxic denitrification of low C/N ratio wastewater with novel ZVI composite carriers

External organic carbon sources are needed to provide electron donors for the denitrification of wastewater with a low COD/NO₃^--N（C/N） ratio, increasing the treatment cost. The economic strategy is to enhance the bioactivity and/or biodiversity of denitrifiers to efficiently utilize organic substances in wastewater. In this study, novel zero-valent iron（ZVI） composite carriers were prepared and implemented in a suspended carrier biofilm reactor to enhance the bioactivity an...     

Evidence on the causes of the rising levels of CODMn along the middle route of the South-to-North Diversion Project in China: The role of algal dissolved organic matter

As the biggest inter-basin water transfer scheme in the world,the South-to-North Water Diversion Project（SNWD） was designed to alleviate the water crisis in North China.The main channel of the middle route of the SNWD is of great concern in terms of the drinking water quality.In this study,we tested the hypothesis that the dissolved organic matter（DOM） derived from the planktonic algae causes the rising levels of COD_Mn along the middle route by monitoring data on water quality（2015-20...     

Novel eco-friendly spherical porous adsorbent fabricated from Pickering middle internal phase emulsions for removal of Pb(II) and Cd (II)

Spherical porous materials prepared from the emulsion template used in the water treat-ment have displayed a vast prospect,as the high surface area,abundant porous structure,convenient operation and excellent adsorption performance.But the tedious fabrication process,high consumption of organic solvent and surfactant limited the application widely.Herein,a facile and eco-friendly spherical porous adsorbent (SPA) is fabricated from the green surfactant-free (corn oil)-in-water Pickering medium internal phase emulsions (Pick-ering MIPEs) via the convenient ion crosslinking procedure.The Pickering MIPEs synergis-tically stabilized with the semi-coke (SC),which is the natural particle produced from the shale oil distillation,and sodium alginate (SA) has excellent storage and anti-coalescence stability.The as-prepared porous adsorbent possessed the abundant pore structure,which provided favorable conditions for effective mass transfer in adsorption,and could be tuned by varying the SA dosage.The saturation adsorption capacities of Pb(Ⅱ) and Cd(Ⅱ) can be achieved with 460.54 and 278.77 mg/g within 45 min at 25℃,respectively.Overall,this study supplied a viable and eco-friendly route for fabricating the spherical porous adsorbent with a tunable porous structure for heavy metal ion wastewater.     

Phenol degradation in waters with high iodide level by layered double hydroxide-peroxodisulfate: Pathways and products

Recently, layered double hydroxide-peroxodisulfate (LDH-PDS) as an advanced oxidation system can effectively remove organics by the pathway of free radical. However, little has been known if there is a potential risk regarding the formation of high toxic iodine byproducts through another pathway when LDH-PDS is used in high iodide waters at coastal areas. Therefore, this study investigated phenol degradation pathways and transformation products to evaluate both removal mechanism and potential risk by LDH-PDS in high iodide waters. The results showed that in LDH-PDS system, with the degradation of PDS, phenol degraded till below detection limit in 1 hr in the presence of iodide, while PDS and phenol were hardly degraded in the absence of iodide, indicating iodide accelerated the transformation of PDS and the degradation of phenol. What is more, it reached the highest phenol removal efficiency under the condition of 100 mg/L LDH, 0.1 mmol/L PDS and 1.0 mmol/L iodide. In LDH-PDS system, iodide was rapidly oxidized by the highly active interlayer PDS, resulting in the formation of reactive iodine including hypoiodic acid, iodine and triiodide instead of free radicals, which contributed rapid degradation of phenol. However, unfortunately toxic iodophenols were detected. Specifically, 2-iodophenol and 4-iodophenol were formed firstly, afterwards 2,4-diiodophenol and 2,6-diiodophenol were produced, and finally iodophenols and diiodophenols gradually decreased and 2,4,6-Triiodophenol were produced. These results indicated that LDH-PDS should avoid to use in high iodide waters to prevent toxic iodine byproduct formation although iodide can accelerate phenol degradation.     

Ozone episodes during and after the 2018 Chinese National Day holidays in Guangzhou: Implications for the control of precursor VOCs

The impact of reducing industrial emissions of volatile organic compounds (VOCs) on ozone (O₃) pollution is of wide concern particularly in highly industrialized megacities. In this study, O₃, nitrogen oxides (NOx) and VOCs were measured at an urban site in the Pearl River Delta region during the 2018 Chinese National Day Holidays and two after-holiday periods (one with ozone pollution and another without). O₃ pollution occurred throughout the 7-day holidays even industrial emissions of VOCs were passively reduced due to temporary factory shutdowns, and the toluene to benzene ratios dropped from ∼10 during non-holidays to ∼5 during the holidays. Box model (AtChem2-MCM) simulations with the input of observation data revealed that O₃ formation was all VOC-limited, and alkenes had the highest relative incremental reactivity (RIR) during the holiday and non-holiday O₃ episodes while aromatics had the highest RIR during the non-pollution period. Box model also demonstrated that even aromatics decreased proportionally to levels with near-zero contributions of industrial aromatic solvents, O₃ concentrations would only decrease by less than 20% during the holiday and non-holiday O₃ episodes and ozone pollution in the periods could not be eliminated. The results imply that controlling emissions of industrial aromatic solvents might be not enough to eliminate O₃ pollution in the region, and more attention should be paid to anthropogenic reactive alkenes. Isoprene and formaldehyde were among the top 3 species by RIRs in all the three pollution and non-pollution periods, suggesting substantial contribution to O₃ formation from biogenic VOCs.     

Investigation of PM2.5 pollution during COVID-19 pandemic in Guangzhou, China

The COVID-19 pandemic has raised awareness about various environmental issues, including PM_2.5 pollution. Here, PM_2.5 pollution during the COVID-19 lockdown was traced and analyzed to clarify the sources and factors influencing PM_2.5 in Guangzhou, with an emphasis on heavy pollution. The lockdown led to large reductions in industrial and traffic emissions, which significantly reduced PM_2.5 concentrations in Guangzhou. Interestingly, the trend of PM_2.5 concentrations was not consistent with traffic and industrial emissions, as minimum concentrations were observed in the fourth period (3/01-3/31, 22.45 μg/m³) of the lockdown. However, the concentrations of other gaseous pollutants, e.g., SO₂, NO₂ and CO, were correlated with industrial and traffic emissions, and the lowest values were noticed in the second period (1/24-2/03) of the lockdown. Meteorological correlation analysis revealed that the decreased PM_2.5 concentrations during COVID-19 can be mainly attributed to decreased industrial and traffic emissions rather than meteorological conditions. When meteorological factors were included in the PM_2.5 composition and backward trajectory analyses, we found that long-distance transportation and secondary pollution offset the reduction of primary emissions in the second and third stages of the pandemic. Notably, industrial PM_2.5 emissions from western, southern and southeastern Guangzhou play an important role in the formation of heavy pollution events. Our results not only verify the importance of controlling traffic and industrial emissions, but also provide targets for further improvements in PM_2.5 pollution.     

极端梯度提升与随机森林融合的天然气露点预测方法

目的 解决目前水露点数据多为人工采用测量仪器测得,时效性低且成本高昂的问题。方法 建立一种基于极端梯度提升(XGBoost)和随机森林(RF)的天然气水露点预测方法。采用XGBoost方法对所有监测工艺参数进行分析,筛选出主要影响水露点的关键工艺特征参数,以排除无关特征参数对预测的干扰。建立RF预测模型,输入关键特征集参数,实现对水露点的实时预测。以重庆气矿某脱水监测系统监测数据与生产数据为例,对所提预测方法进行对比分析验证。结果 相较于XGBoost、SVM等预测方法,RF模型具有最佳的预测性能,且经过XGBoost特征选择后,RF预测结果的MAE值降低了0.016 9 ℃,RMSE值降低了0.014 6 ℃。结论 基于极端梯度提升与随机森林融合的水露点预测方法具有更优的预测精度与鲁棒性,对指导脱水现场生产具有积极作用。