https://doi.org/10.5061/dryad.1rn8pk12g

We conducted a high-resolution study of lead in an urban moss, Orthotrichum lyellii, to better understand lead distributions and sources in Portland, Oregon, United States. The goal of this study was to identify modern and persistent legacy urban lead sources. This included an investigation of the impact of relic lead-sheathed telecommunication cables on environmental lead levels. Here we present lead levels and isotopic compositions of (1) moss samples collected from Portland in 2013, (2) moss samples collected 10 years later in 2023 for proximity to lead-sheathed telecommunication cables, (3) archival moss and lichen samples, and (4) rural moss samples. The findings of this study and methods can be found in the linked primary article.

Description of the data and file structure

The data is provided in an Excel spreadsheet. The table includes the following information for samples: latitude and longitude, collection year, species, lead (Pb) concentrations in parts per million or ppm (mg/kg), log lead concentrations, and lead isotope ratios (i.e., 206Pb/204Pb, 207Pb/204Pb, 208Pb/204Pb, 206Pb/207Pb, 208Pb/206Pb, and 208Pb/207Pb). For samples not measured for lead isotopic ratios, null is used to indicate the value is missing. In column A: rep indicates a repeat lead isotope measurement used to monitor repeatability and calculate precision on measured lead isotope ratios for real samples; dup refers to a full procedural duplicate, inclusive of sample digestion, isolation of sample lead, and lead isotopic analysis; and resample refers to the collection of a new sample in 2023 at a location sampled in 2013.

For Portland moss samples, the annexation decade for the sampling location is also provided. These annexation dates were obtained from the City of Portland (https://www.portland.gov/bps/documents/historical-annexations-city-portland).

For sampling locations near identified lead-sheathed telecommunication cables, information on the proximity of the sampling location to the cable and the year the cable was removed, if appropriate, are also given. N/A is used to indicate that the data is not applicable. Sampling locations with lead-sheathed telecommunication cables are identified by Y and those without by N. *S indicates that a site is suspected to have had lead cables. For locations with cables, C and H are used to indicate their current or historical presence, respectively. S is used to indicate that the cable was identified on the same side of the street, within 1 m. O indicates that the cable was identified at a distance of 6–100 m, generally on the opposite side of the street. A number in parentheses indicates the approximate distance from the sampled tree to the lead cable in meters. GPS coordinates for sampling locations near lead-sheathed telecommunication cables are rounded to 3 decimal places to protect the privacy of adjacent property owners.

Lead concentrations of samples from the Portland 2023 moss study, the rural background moss location MCD, and the archival moss and lichen study were measured at Oregon State University. The uncertainty on these measurements is estimated as 2SE, 25‰, based on repeat analysis of reference materials IAEA-336 (n=9) and BCR-482 (n=8). For lead concentrations of moss from the Portland 2013 moss study and the rural background moss locations BSNWR and MWCA, the uncertainty is estimated as 2SE, 46‰ based on repeat analysis of reference material IAEA-336 (n=9). For lead isotope ratios the uncertainty is estimated from replicate sample measurements as ±2x the mean absolute difference (MAD) precision on the average 2013 Portland moss Pb isotopic composition: 0.0022 for 206Pb/204Pb, 0.0018 for 207Pb/204Pb, 0.0059 for 208Pb/204Pb, 0.00010 for 206Pb/207Pb, 0.00020 for 208Pb/206Pb, and 0.00009 for 208Pb/207Pb.

Sharing/Access information

Lead concentration data for the 2013 Portland moss samples was obtained from:

• Gatziolis, D., Jovan, S., Donovan, G., Amacher, M. & Monleon, V. Elemental Atmospheric Pollution Assessment via Moss-Based Measurements in Portland, Oregon. PNW-GTR-938 https://www.fs.usda.gov/treesearch/pubs/51076 (2016) doi:10.2737/PNW-GTR-938.

Lead concentration data for the rural background moss group locations BSNWR and MWCA was obtained from:

• Oregon Department of Environmental Quality. Evaluation of Moss Sampling as a Methodology for Evaluating Air Toxics, Using Portland as a Study Area. 32 (2018).