Current Pollution Reports最新文献

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

Purpose of Review

The ability to monitor soil moisture wirelessly can deliver immense benefits to annual crops. Real-time soil moisture monitoring allows for accurate and on-demand irrigation to achieve optimal growth and avoid overwatering. It is also an effective pollution prevention method, eliminating excessive run-off to prevent soil erosion, sediment discharge, and the dispersion of key water pollutants such as nitrogen and phosphorus to natural waterway. Current soil moisture sensors require constant a power supply or battery. Wiring can be used for soil moisture sensing of perennial crops but is also not suitable for annual crops that require significant tillage. This review aims to delineate the readiness of moisture sensors and wireless power transfer technology for developing a wireless soil moisture sensing network.

Recent Findings

Of the many types of soil moisture sensors, only a few are compatible to a wireless network. They either are too expensive, have unreliable measurement accuracy, or require too much power. This review shows that capacitive sensor is a potential candidate for underground sensor networks in terms of affordability, measurement reliability, and power consumption. In addition, among all currently available wireless power transfer technologies, inductive power transfer has the potential to supply adequate power for wirelessly charging underground sensors and meet other requirements of an underground sensing network.

Summary

This review evaluates available soil moisture sensing and wireless power transfer techniques for wireless underground moisture sensing. The combination of capacitive sensing and inductive power transfer technologies has been identified as a potential solution for wireless underground sensor networks. Future research should focus on improving the calibration and post-processing algorithm for capacitive sensor while the misalignment and impact of soil need to be considered to enhance the performance of the inductive power transfer system.