This dataset reports chemical speciation of airborne gas and aerosol particulate matter (PM) sampled in various locations on the Island of Hawai'i in 2018 and 2019. The 2018 samples were collected during a large eruption of Kilauea volcano. The 2019 samples were collected during a period of very low volcanic activity. Samples were collected in several locations on the Island of Hawai'i, Hawaii, USA. Time-series samples were collected at -Leilani Estates -Volcano village -Pahala, Ocean View -Kailua-Kona -Mauna Loa Observatory in 2018 and 2019. Point-source samples were collected at the following locations -The main erupting vent 'Fissure 8' on the Kilauea Volcano in 2018, and repeated in its vicinity post-eruption in 2019 - The lava ocean entry point in 2018 and repeated in its vicinity post-eruption in 2019. The samples were collected using filter packs (FP) and Sioutas cascade impactors (SKC). The instruments were used at ground-level in all cases except for samples FP_08_1, FP_ 09_1, FP_09_2, SKC_08 and SKC_09 which were attached to an Unoccupied Aircraft System (UAS) in order to safely access the erupting vent and the lava ocean entry. The samples were then analysed using inductively-coupled plasma mass spectroscopy (ICP-MS), inductively-coupled plasma optical emission spectroscopy (ICP-OES) and ion chromatography (IC). Sample analysis was done at the University of Leeds, United Kingdom (2018 samples) and the University of Leeds and Open University, United Kingdom (2019 samples). The results are reported as concentration per volume of air sampled (µg/m^3) to 2 significant figures. This was done to - assess the dispersion of major and trace elements in a volcanic plume, and quantify their depletion rates from the source into the far-field (up to ~240 km downwind) - assess the impact of volcanic emissions on the composition of the local atmosphere. The data were produced as a result of a collaborative project between the Universities of Leeds, Cambridge, Oxford (UK), Hawaiian Volcano Observatory of the United States Geological Survey, and the University of Hawai'i at Manoa (USA).

Data from observations made at the Cape Verde Atmospheric Observatory (CVAO) which exists to advance understanding of climatically significant interactions between the atmosphere and ocean and to provide a regional focal point and long-term data. The observatory is based on Calhau Island of São Vicente, Cape Verde at 16.848N, 24.871W, in the tropical Eastern North Atlantic Ocean, a region which is data poor but plays a key role in atmosphere-ocean interactions of climate-related and biogeochemical parameters including greenhouse gases. It is an open-ocean site that is representative of a region likely to be sensitive to future climate change, and is minimally influenced by local effects and intermittent continental pollution. The dataset contains Total Gaseous Mercury (TGM) measurements made from 7.5m using a Tekran CVAFS Mercury Analyser.