Accurate and Precise Atmospheric Ammonia Measurement: From Emission Sources, Analytical Methods to Mitigation Strategies

Ammonia (NH₃) is a key reactive nitrogen species with critical roles in local, regional, and global nitrogen cycling, and it is increasingly recognized for its impact on environmental pollution and climate change. As a major precursor of secondary particulate matter, NH₃ contributes to fine aerosol formation, which adversely affects air quality and human health, particularly through respiratory and cardiovascular diseases. Accurate and precise measurement of atmospheric NH₃ is therefore essential to quantify its concentrations, elucidate sources and sinks, and understand deposition processes. This review systematically introduces and evaluates the current methodologies and instrumentation for NH₃ measurement, including chemical, electrochemical, optical, and remote-sensing approaches. The advantages, limitations, and comparative performance of these techniques are analyzed to provide guidance for selecting appropriate measurement strategies. Special emphasis is placed on open-path laser-based instruments, which enable high-sensitivity, high-temporal-resolution measurements in field campaigns, facilitating improved characterization of spatial and temporal NH₃ distributions, particularly in undermonitored regions. Finally, the review synthesizes current mitigation and control strategies for NH₃ emissions, highlighting approaches applicable to agricultural and industrial sectors. Policy implications and practical recommendations are discussed to support evidence-based decision-making for emission reduction. By integrating advances in measurement techniques with emission control strategies, this work aims to provide a comprehensive framework for understanding and managing atmospheric NH₃, ultimately contributing to improved air quality, ecosystem protection, and human health.