Current Pollution Reports最新文献

Purpose of Review

As an important type of light-absorbing aerosol in the atmosphere, brown carbon (BrC) is an effective driver for climate change. Field observations of BrC typically involve the extraction of filter samples (e.g., using water and methanol), followed by optical and chemical analyses. This review summarizes the concentration measurements, optical properties, and chemical characteristics of BrC in China, based on results from the extraction approach.

Recent Findings

We started with measurement techniques for the determination of BrC concentration and compared the extraction efficiencies of different solvents. Then we investigated the temporal and spatial variations of BrC’s absorption Ångström exponent (AAE) and mass absorption efficiency at 365 nm (MAE₃₆₅), two parameters relevant to climate studies. AAE and MAE₃₆₅ were found to be mainly influenced by the type of solvent used and BrC sources, respectively. Using the observed AAE and MAE₃₆₅, BrC was demonstrated to be a non-negligible contributor to climate forcing. Finally, BrC chromophores were discussed on a molecular level, with focus on the nitrogen-containing compounds and polycyclic aromatic hydrocarbons.

Summary

Despite studies on BrC concentrations measurements were widely conducted, standardized methods remain inconclusive. Regarding the optical properties of BrC, MAE₃₆₅ exhibited significant temporal and spatial patterns, while AAE showed the opposite results. Through chemical characterization, BrC chromophores were identified and their association with optical properties was highlighted. This review contributes to the understanding of BrC properties and has implications for future studies on BrC.

Graphical Abstract

Purpose of Review

During the past decade, weather and climate extremes, enhanced by climate change trends, have received tremendous attention because of their significant impacts on socio-economy, public health, and ecosystems. At the same time, many parts of the world still suffer from severe air pollution issues. However, whether and how air pollutants play a role in weather and climate systems through complex interactions and feedbacks with meteorology and ecosystems remains an open question. So far, only a relatively small number of studies have been conducted to understand and quantify air pollution interactions with weather and climate extremes. As a result, there is limited process-level knowledge of this topic and associated mechanisms. This review paper provides a concise synthesis of recent scientific advances, current knowledge gaps, and future directions on air pollution interactions with weather and climate extremes, such as extreme precipitation, floods, droughts, wildfires, and heat waves.

Recent Findings

There is evidence (albeit limited) that air pollution can contribute to or interact with each of the aforementioned extremes, and several possible mechanisms (e.g., physical, thermodynamical, dynamical, chemical, and ecological processes) have been identified and proposed to explain their relationships. However, there are still substantial knowledge gaps that need to be addressed in future studies, which will benefit from enhanced observational and modeling capabilities as well as interdisciplinary collaborations.

Summary

Overall, the air pollution interactions with weather and climate extremes are currently under-studied and less understood. More future research is needed for process-level investigations to improve the mechanistic understanding on this topic.

Purpose of Review

Environmental pollution stemming from industrial, agricultural, and domestic activities is constantly increasing. The removal of these hazardous pollutants from the environment is inevitable, so finding and developing convenient, cost-effective, and biocompatible treatment methods is imperative. As emerging adsorbents, green nanoparticles (NPs) have received significant attention in recent years due to their biocompatibility and promising capability for removing pollutants such as heavy metals from aqueous solutions. This study aims to provide a comprehensive and coherent review of the heavy metals removal via an adsorption technique using green nanoparticles, focusing on their synthesis and adsorption mechanisms.

Recent Findings

Currently, plants and microorganisms are used to synthesize green nano-adsorbents. The antioxidant compounds in the extracts of different parts of the plants could be used as reducing agents for the synthesis of zero-valent metal nanoparticles. Moreover, they can be applied to the surface of nanoparticles, which enhances the stability of synthesized nanoparticles. In addition to plant-derived compounds, microorganisms can play a significant role in synthesizing green nanoparticles.

Summary

For decades, human health and the environment have been threatened by exposure to heavy metals caused by the activities of mines, industries, and factories. Therefore, there is a need to provide solutions to remove these pollutants from the environment. One of the effective solutions is the adsorption method. The efficiency of this method is strongly influenced by the selection of suitable adsorbents. In recent years, special attention has been paid to nano-adsorbents. Utilizing green nano-adsorbents, as opposed to conventional materials, is a critical strategy for reducing environmental pollutants, particularly for heavy metal adsorption from contaminated water and wastewater. This paper also discusses the sources and occurrence of heavy metals, as well as a number of environmental issues of methods that employ green and eco-friendly nano-adsorbents for heavy metals removal, including (i) the type of heavy metals and their use pattern, (ii) influencing factors, (iii) heavy metal analysis methods and their potential toxicity, and (iv) different conventional and cutting-edge nanotechnologies for water and wastewater treatment. The literature review, which covered the years 2002–2023, provided a critical illustration of current concerns about heavy metal contamination and removal efforts, with a focus on green nano-adsorbents and the use of these environmentally friendly materials.

Purpose of Review

Growing algae in wastewater offers carbon-neutral biomass production and pollutant removal. However, practical applications of wastewater-grown algal biomass have social acceptability issues in the food and feed industries due to unexpected threats (such as human/animal pathogens and toxins) associated with the wastewater-grown biomass. Therefore, considering the substantial pollutant removal potential of microalgae and the abundance of wastewater as a growth media, alternative bioprocessing routes of the wastewater-grown biomass should be developed. This review highlights some non-food and non-feed applications of wastewater-grown algae biomass.

Recent Findings

Wastewater-grown algal biomass contains high amounts of carbohydrates, proteins, and lipids depending upon the composition of wastewater and algal species grown. These three significant metabolites are precursors to bioenergy and biomaterial products such as bioethanol, biogas, and bioplastics. Hydrolysis of the wastewater-grown algal biomass can be easily improved to enhance the microbial fermentation yields to produce bioethanol and biobutanol. Fresh algal biomass, residual biomass, or both can be used as feedstocks in anaerobic digestion/co-digestion to produce biogas. Depending upon the selected species, wastewater-grown algal biomass can also produce biopolymers whose productivity depends on growth conditions, wastewater composition, and biopolymer synthesis method. Enzymatic, eco-friendly chemicals and mechanical approaches used to prepare biopolymers from algal biomass should be optimized for higher yields of biopolymers.

Summary

Although wastewater-grown biomass has acceptability issues, it offers certain environmental benefits, including atmospheric carbon capture, phycoremediation of pollutants, and water recycling. This manuscript highlights the recent progress and emerging trends of wastewater-grown algal biomass as a feedstock with potential applications for fermentation, anaerobic digestion, and bioprocessing to produce clean energy and bioplastics.

Graphical Abstract

Purpose of Review

Calculating atmospheric aerosol radiative forcing is a crucial aspect of climate change research. The aerosol scattering phase function stands out as a vital parameter for radiative forcing computations and holds significant importance in the remote sensing retrievals of aerosols. Despite its significance, research on aerosol scattering phase function measurements has been limited over the years. This review article provides a comprehensive summary of relevant studies on the measurements of aerosol scattering phase functions.

Recent Findings

In recent times, the application of imaging detection techniques in the measurement of aerosol scattering phase functions has emerged, highlighting advantages such as portability and high temporal-angular resolution. In addition, the development of aerosol retrieval algorithms facilitates a broader application of the results obtained from aerosol scattering phase function measurements in estimating aerosol physical properties and satellite retrievals.

Summary

This review introduces the measurement techniques, instruments, and retrieval algorithms associated with aerosol scattering phase functions, encompassing laboratory experiments, in situ field measurements, and remote sensing retrieval. The measurement results and related research on aerosol morphological effects and physical property retrievals have been summarized. Finally, it outlines future research prospects, suggesting improvements in instruments, experimental expansion, and enhanced data analysis and application, providing feasible suggestions for further studies.

Purpose of Review

Rapid economic development accompanied by urbanization, motorization, and industrialization, together with population growth, puts great pressure on the power sector in Southeast Asia (SEA) to meet energy demand. This paper reviews the past 20-year power generation in SEA countries to analyze potential impacts on atmospheric pollution using DPSIR framework.

Recent Findings

In 2020, total region electricity generation reached 1050 TWh, 3.1 times above that of 2000, and is projected to further increase by 2.5 times in 2050. During the period, the annual per capita generation increased 2.4 times. Indonesia, Malaysia, Thailand, and Vietnam were the main electricity producers, sharing 83% in 2020. Coal and natural gas based thermal power plants (TPPs) were dominant with 72% of the total electricity produced, whereas low-carbon renewable energy, although increased during the period, shared only 25% in 2020. In 2018, the sectoral atmospheric emissions of different species increased by 2.4–11.5 times above 2000, contributing 55.3%, 26.8%, and 26.7% to the region’s total anthropogenic emissions of SO₂, CO₂, and NO_x, respectively.

Summary

Heavy reliance on fossil fuels makes the power sector a key emission source of air pollutants and greenhouse gases. SEA governments have promulgated policies and regulations for TPPs and set net zero emissions targets. These policies, directly and/or indirectly address atmospheric pollution, once fully implemented, bring in more secure and sustainable power sources in the region, along with multiple benefits to air quality, human health, environment, ecosystem, and the climate.

Purpose of Review

As the most abundant alkaline trace gas in the atmosphere, NH₃ plays a critical role in the formation of atmospheric particulate matter and nitrogen cycling in ecosystems. NH₃ emissions have been increasing globally over the past few decades. To provide a clearer understanding of atmospheric NH₃, this paper presents a systematic review of the literature on the sources and variability of atmospheric NH₃ and describes the contribution of atmospheric NH₃ to PM_2.5.

Recent Findings

(1) The primary source of atmospheric NH₃ emissions is agriculture; other sources include combustion-related emissions and volatilization from soil and oceans. However, recent studies have revealed the major role of nonagricultural sources in urban areas. (2) The spatiotemporal variability of atmospheric NH₃ is complex, and its mechanisms are not entirely clear. (3) Atmospheric NH₃ can participate in multiple atmospheric chemical processes and to the formation of fine particulate matter.

Summary

This review summarizes the latest knowledge on the sources and variability of atmospheric NH₃ and highlights the necessity of controlling atmospheric NH₃ emissions. However, significant knowledge gaps still exist in understanding the sources, trends, and effects of atmospheric NH₃. Therefore, further research is essential to investigate the influencing factors and environmental effects of atmospheric NH₃ concentrations, providing a scientific basis for the development of effective NH₃ control strategies.

Purpose of Review

Complex air pollution has spread in the conurbation areas of China along with chemically complicated air pollution processes. Classic secondary-pollutant formation toward high concentrations of fine particulate matter (PM_2.5) and ozone (O₃) is imperfectly understood in the currently accepted chemical mechanisms. The combustion-produced fine particles contain abundant nanosized black carbon (BC) internally mixed with transition metal ions (TMI) and contribute to the complicated oxidation pathways and products substantially. Based on current understandings of multiphase sulfate formation, we propose that the surface-enhanced heterogeneous reaction processes can play critical roles in the fast formation of “haze chemistry smog” pollution.

Recent Findings

Pathways of sulfate enhancement by BC and TMI have been identified to explain the formation mechanisms of the missing sulfate sources. Responsible for additional production of secondary gas molecules and aerosols, the heterogeneous chemistry is initiated with surface photosensitive catalysis. In addition, unidentified atmospheric oxidizing capacity is recognized as part of the heterogeneous processes. Given unique surface-specific profiles and electronically excited dismutation reactions, BC and TMI particles can steadily generate reactive oxygen species (ROS) such as hydroxyl radicals (OH) and promote the oxidation of SO₂. This phenomenon provides an extended insight into atmospheric free-radical chemistry. As such, the heterogeneous catalytic oxidation of SO₂ on aerosol surfaces accounts for up to 69.2% of sulfate formation in haze episodes.

Summary

Unlike in-cloud aqueous oxidation, representative heterogeneous reaction pathways (i.e., TMI aqueous catalysis pathway and surface catalysis pathway) enhance sulfate formation via surface radical reactions in both winter and summer. The heterogeneous processes are thought to reduce gaps between model-predicted and measured sulfate levels. The physically and chemically active BC and TMI can change the composition, morphology, hygroscopicity, and optical properties of PM in their atmospheric aging processes. Therefore, the heterogeneous pathways facilitate rapid particle growth for haze pollution and help to understand and develop a new type of air pollution chemistry (i.e., “haze chemistry” processes) in China and other developing countries.

Purpose of Review

The purpose of this review is to evaluate the effectiveness of biochar in immobilizing arsenic (As) in contaminated paddy soils and its impact on As availability and bioaccumulation in rice, as well as rice plant biomass.

Recent Findings

Recent studies have focused on managing As contamination in agricultural fields, with a particular focus on South and Southeast Asia, where rice, a primary food source and As accumulator, is of significant concern. Biochar, a product of biomass pyrolysis, has emerged as a viable solution for environmental remediation due to its effectiveness in immobilizing metal(loid)s in water and soil. The successful implementation of biochar as a soil amendment strategy has led to growing interest in its use as an effective means of reducing the bioaccumulation and availability of metal(loid)s, including As.

Summary

A meta-analysis of 25 studies revealed that biochar generated from maize and sewage sludge successfully reduced As availability and bioaccumulation in rice grains. In addition, the use of biochar led to higher biomass and yield of rice crops compared to control groups. Modified biochar was more effective in decreasing As availability, likely due to interactions with iron and calcium phases or complexes occurring in or on the biochars. Nevertheless, at elevated biochar dosages, As mobilization was noted in field conditions which warrants further investigation.

Purpose of Review

This review aims to evaluate and discuss the current advances in the measurement and assessment of the noise generated by unconventional aircraft, such as unmanned aircraft systems (UAS) and urban air mobility (UAM) vehicles. Building upon the findings of this review, research gaps are identified, and further work is proposed to enhance existing and emerging methods for the appropriate noise management of these advanced air mobility (AAM) technologies.

Recent Findings

Noise has been highlighted as one of the key concerns for the wider deployment of UAS and UAM operations. This is suggested to be due to having acoustic signatures with sound characteristics commonly associated with noise annoyance, such as ‘sharpness’ (the perceived proportion of high-pitched sonic energy) and ‘tonality’ (the perceptual prominence of concentrated sonic energy at discrete frequencies). These types of ‘psychoacoustic features’ are thought to be connected with observations of increased noise annoyance for AAM, compared with conventional aircraft and road vehicles, at the same level of sound exposure.

Summary

In the last few years, there has been a growing body of research on UAS and UAM noise. Research has focused on a comprehensive understanding of the sound sources of these unconventional aircraft under a wide range of operating and operational conditions. Based on gathered evidence, measurement protocols for both laboratory and field studies are very advanced for the acoustic characterisation of UAS in terms of sound level, frequency and directivity. Looking at the human response to UAS and UAM noise, loudness has been consistently reported as the main contributor to noise annoyance, with second-order contributions from other psychoacoustic features, such as sharpness, tonality and ‘amplitude modulation’ (fluctuations in loudness over time), varying among studies. Noise targets for UAS certification have been derived from existing regulations for conventional aircraft and rotorcraft, but might not account for the usually reported annoyance offset between UAS/UAM and conventional vehicles. Key research gaps identified include the lack of studies focusing on multiple events, and deeper understanding of the influence that personal or contextual factors may have on responses, which will be important for the development of robust methods for the assessment and minimisation of community noise annoyance due to the operation of these unconventional aircraft.

Graphical Abstract