Ammonia concentrations from high-elevation Himalayan forests and a Sri Lankan tropical forest, 2022-2024

Starting May 2022, triplicate sets of UKCEH Adapted Low-cost Passive High Absorption (ALPHA®) samplers were deployed under the forest canopy at sites buffered by at least 500 m of continuous forest on all sides. The exposed samplers were replaced with fresh ones at the end of each month. The exposed samplers from India, Nepal, Bhutan and Sri Lanka were analysed at the National Centre for Sustainable Coastal Management, Chennai and samplers from Pakistan were analysed at UKCEH, Edinburgh using the salicylate method. Blank samplers for each period were also analysed. The analysis provides the concentration of ammonium ions absorbed by each sampler. This is further converted to atmospheric ammonia concentration using an uptake rate which determined annually in the UK by co-locating the ALPHA samplers with UKCEH DEnuder for Long-Term Atmospheric sampling (DELTA®) samplers at multiple UK sites. The monthly concentration at each site is calculated as the average of the concentration measured by each sampler in the triplicate set. Obvious outliers are removed before calculating the average. Further quality assurance is performed based on comments from site operators regarding physical damage to the sampler, wet sampler, etc.

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Meteorological data and ammonia concentration and deposition rates from an ammonia enhancement experiment site, Queensberry, Sri Lanka, 2022