100 years of high GEM concentration in the Central Italian Herbarium and Tropical Herbarium Studies Centre (Florence, Italy)

Mercury accumulation efficiency of different biomonitors in indoor environments: the case study of the Central Italian Herbarium (Florence, Italy)

Biomonitoring studies are often employed to track airborne pollutants both in outdoor and indoor environments. In this study, the mercury (Hg) sorption by three biomonitors, i.e., Pinus nigra bark, Pseudovernia furfuracea lichen, and Hypnum cupressiforme moss, was investigated in controlled (indoor) conditions. In comparison to outdoor environments, controlled conditions offer the opportunity to investigate more in detail the variables (humidity, temperature, pollutants speciation, etc.) that control Hg uptake. The biomonitors were exposed in two distinct periods of the year for 2 and 12 months respectively, in the halls of the Central Italian Herbarium (Natural History Museum of the University of Florence, Italy), which are polluted by Hg, due to past plant sample treatments. The Hg sorption trend was monitored every 3 weeks by recording: (i) the Hg content in the substrata, (ii) gaseous elemental mercury (GEM) concentrations in the exposition halls, (iii) temperature, (iv) humidity, and (v) particulate matter (PM) concentrations. At the end of the experiment, Hg concentrations in the biomonitors range from 1130 ± 201 to 293 ± 45 μg kg-1 (max-min) in barks, from 3470 ± 571 to 648 ± 40 μg kg-1 in lichens, and from 3052 ± 483 to 750 ± 127 μg kg-1 in mosses. All the biomonitors showed the highest Hg accumulation after the first 3 weeks of exposure. Mercury concentrations increased over time showing a continuous accumulation during the experiments. The biomonitors demonstrated different Hg accumulation trends in response to GEM concentrations and to the different climatic conditions (temperature and humidity) of the Herbarium halls. Barks strictly reflected the gaseous Hg pollution, while lichen and moss accumulation was also influenced by the climatic conditions of the indoor environment. Mercury bound to PM seemed to provide a negligible contribution to the biomonitors final uptake.

Continuous and near real-time measurements of gaseous elemental mercury (GEM) from an Unmanned Aerial Vehicle: A new approach to investigate the 3D distribution of GEM in the lower atmosphere

We present the first real attempt to directly and continuously measure GEM through a Lumex RA-915 M, designed for real-time detection of mercury vapor, mounted on an UAV (Unmanned Aerial Vehicle, namely a heavy-lift octocopter), inside and outside the former Hg-mining area of Abbadia San Salvatore (Mt. Amiata, Italy), known as a GEM source. We tested the effectiveness of the UAV-Lumex combination at different heights in selected sites pertaining to both mining facilities and surrounding urban zones, shedding light on the GEM spatial distribution and concentration variability. The Lumex great sensitivity and the octocopter optimal versatility and maneuverability, both horizontally and vertically, allowed to depict the GEM distribution in the atmosphere up to 60 m above the ground. The acquisition system was further optimized by: i) synchronizing Lumex and UAV GPS data by means of a stand-alone GPS that was previously synchronized with Lumex; ii) using a vertical sampling tube (1.20 m high) connected to the Lumex inlet to overcome the rotors strong airflows and turbulence that would have affected GEM measurements; iii) supplying the octocopter with batteries for power supply to avoid the release of exhaust gases; iv) taking the advantage of the UAV ability to land in small spaces and stop at selected altitudes. The resulting dot-map graphical representations, providing a realistic 3D picture of GEM vertical profiling during the flights in near real-time, were useful to verify whether the guideline concentrations indicated by competent authorities were exceeded. The results showed that the GEM concentrations in the urban area, located a few hundred meters from the mining structures, and close to already reclaimed areas remained at relatively low values. Contrarily, GEM contents showed significant variations and the highest concentrations above the facilities containing the old furnaces, where increasing GEM concentrations were recorded at decreasing heights or downwind.

Particle-Bound Mercury Characterization in the Central Italian Herbarium of the Natural History Museum of the University of Florence (Italy)

Museums air quality can be negatively affected by treatments with heavy metals compounds employed to prevent pest infestations. Among these, the past use of mercury dichloride (HgCl₂) on herbaria artifacts currently produces high levels of indoor atmospheric gaseous mercury (Hg⁰) and possibly of particulate bound Hg (PBM), i.e., the particulate matter containing Hg. This study evaluates the PBM pollution in the Central Italian Herbarium (Natural History Museum of the University of Florence, Italy), characterizing the size range and chemical speciation with SEM-EDS microanalysis. The analysis of the total Hg concentration in the samples allowed to calculate the workers exposure risk to this pollutant. PBM is almost totally classifiable as fine particulate with a significant dimensional increase in a period of scarce attendance of the Herbarium rooms. The microanalysis indicates that Hg is essentially bound to S, highlighting the change of Hg speciation from the original association with Cl. The average Hg concentration reveals a potential health risk for workers as result of multiple Hg exposure pathways, mainly by ingestion. The study provides information for characterizing PBM pollution that could affect a workplace atmosphere and a useful basis to evaluate and correctly design solution strategies to reduce the contamination levels and protect workers’ health.