Measurements of heavy metals in the moss Orthotrichum lyellii collected using community science in the Duwamish Valley, Seattle, Washington, U.S.A.

<p>Heavy metals concentrations often vary at small spatial scales not captured by air monitoring networks, with implications for environmental justice in industrial-adjacent communities. Pollutants measured in moss tissues are commonly used as a screening tool to guide use of more expensive resources, like air monitors. We piloted a community science approach, engaging over 55 people from nine institutions, to map heavy metals using moss in two industrial-adjacent neighborhoods. Local youth led sampling of the moss <em>Orthotrichum lyellii</em> from trees across a 250×250-m sampling grid (n = 79). We compared their data with expert-collected samples (n = 19) using Principal Components Analysis and Procrustes Analysis. We mapped 21 chemical elements measured in moss, focusing on 6 toxic 'priority' metals: arsenic, cadmium, chromium, cobalt, lead, and nickel. We compared local data, using t-tests and boxplots, with two 'reference datasets' of <em>O. lyellii</em> collected in Portland, Oregon, and in Seattle City Parks. We also use Principal Components Analysis to describe major gradients in metals in the study area. Our data submission includes two R scripts and four datasets of heavy metals in moss, including the two reference datasets, which will enable replication of our analyses as well as novel analyses.</p>