DOI: 10.5285/449e746d-6291-4653-a3e0-b18f897abc3e
title: Meteorological data and ammonia concentration and deposition rates from an ammonia enhancement experiment site, Queensberry, Sri Lanka, 2023-2024

description: This dataset contains information about meteorological conditions, ammonia concentration and deposition rates resulting from an experimental ammonia (NH3) enhancement setup in a tropical forest in central Sri Lanka. The experiment is designed for controlled enhancement of ambient NH3 concentration within the study plot under natural field conditions so that effects of NH3 on tropical vegetation can be studied. This will help identify tolerance thresholds of vegetation to NH3 as an air pollutant and determine critical levels that can be incorporated into regional environmental policy.  Meteorological measurements were recorded at multiple heights on a meteorological tower. Under suitable wind conditions, NH3 was released towards two vegetation monitoring transects replicating pollution from a point source, and NH3 concentrations in the air were measured using monthly passive samplers. Continuous meteorological data, NH3 release, and NH3 concentration data are provided in 15-minute intervals and this dataset relates to measurements taken in 2023 – 2024. Deposition rates were modelled using a bi-directional resistance model on a monthly timescale based on measured NH3 concentrations in the air, micrometeorology and plant physiology. This dataset provides an extension of the 2022 dataset to enable longer term analysis of NH3 deposition and its effects in a tropical forest.

The work was supported by UKRI GCRF South Asian Nitrogen Hub (Grant NE/S009019/1).
description: Meteorological parameters such as temperature, relative humidity, total solar radiation, photosynthetically active radiation, wind speed and wind direction were measured at four heights starting from the ground level to above-canopy. The measurements were made on a 12 m tall mast. Additionally, soil moisture, temperature and electric conductivity was measured at three depths. All instruments measured data every 20 seconds and the average was calculated over 15-minute intervals by a data logger. NH3 enhancement was conducted by releasing the gas from a pure anhydrous NH3 cylinder. A mass flow controller (MFC) released pre-programmed volume of NH3 under suitable wind conditions and the release volume and time is recorded on the datalogger at 1-minute intervals. The meteorological and NH3 enhancement data was checked visually, and any obvious errors introduced by instrument malfunctioning, datalogger programming issues and power cuts were removed. NH3 concentrations were measured downwind of the source using UKCEH Adapted Low-cost Passive High Absorption (ALPHA®) samplers and analysed monthly. NH3 concentrations not following the regular exponentially declining curve with distance from the source were removed. Monthly dry deposition of NH3 to different layers of the canopy was modelled using a bi-directional resistance model written in R. The experiment was initiated in 2022 and a dataset for that year is published. As NH3 impacts occur over a longer timescale, measurements are continuing in order to temporally expand the dataset, and this dataset relates to data collected in 2023 – 2024.