Duwamish Valley communities collaborate on urban air quality biomonitoring projects

Project Description

A University of Washington collaborator advises a Duwamish Valley Youth Corps member on weighing a moss sample. USDA Forest Service photo by Monika Derrien.

Community organizations, nonprofits, universities, and government collaborators partnered to adapt a Forest Service bio-indicator method for youth and community training and use. This method identifies areas with potentially high air pollution levels, suggested by heavy metal concentrations in particulate matter measured in moss tissue. During two collection years (2019 and 2021), youth participants have collected and prepared hundreds of moss samples from trees throughout Georgetown and South Park in Seattle's Duwamish Valley. The moss samples are analyzed at a lab for concentrations of 25 elements, including 6 heavy metals (arsenic, cadmium, chromium, cobalt, nickel, and lead), using inductively coupled plasma optical emission spectrophotometry. Analysis has considered the experiences of youth participants in the sample collection, data quality, the spatial distribution of metals concentrations, and the environmental spatial predictors of metals concentrations. Results are guiding policy and programming decisions.

Purpose and Scope

A common tool in natural areas, our work is the first application in industrial-adjacent residential neighborhoods facing environmental and social justice challenges. We seek to...

1) Co-develop a community tool for assessing areas with potentially high metal concentrations in particulate matter in the Duwamish Valley.

2) Implement and test tool for its efficacy in youth learning and programming, and in identifying localized air pollution.

3) Inform and contribute to air pollution mitigation efforts, including tree planting and revegetation efforts.

4) Raise awareness of air pollution issues and health inequities in the Duwamish Valley and the use of trees and vegetation as both an indicator and as a mitigation tool.

Implementation

Moss sampling protocols were adapted from prior studies using Orthotrichum lyellii. The sampling grid in Georgetown and South Park was co-developed with community members, and sampling was conducted by local youth corps participants. Analysis was completed at the Forest Service Northern Research Station laboratory in Grand Rapids, Minnesota, using inductively coupled plasma optical emission spectrophotometry. Youth experience was assessed using pre- and post-surveys, and youth-collected data quality was evaluated with analysis of moss sample replicates. Principal components analysis was used to characterize major air quality gradients, and geographically weighted regression was used to describe area-level spatial predictors of metals concentrations.

A Duwamish Valley Youth Corps member considers a tree for moss sampling with Pacific Northwest Research Station emeritus scientist Dale Blahna. USDA Forest Service photo by Monika Derrien.

Key Findings

• Youth scientists demonstrated their comprehension of project content and appraised their engagement favorably.
• Youth scientists collected usable samples with acceptable precision among repeated samples.
• Concentrations of priority metals in Duwamish Valley moss were significantly much greater than Seattle City Parks and Portland, Oregon residential datasets.
• Individual metals varied spatially although priority metals tended to peak in the central industrial core where many possible emissions sources, including legacy contamination, converge.
• Priority metals in moss varied greatly over short distances and correlated with elements indicative of fugitive dust and soil, suggesting larger particles may be important carriers of heavy metals in the study area.
• The percentage of people of color in the study areas was significantly positively associated with lead and chromium concentrations.
• Greater tree cover within 200 m of sample sites was associated with lower metal concentrations, in particular cadmium, in moss. 
• Our findings underscore the potential influence of heavy industry and mobile sources on heavy metal concentrations, the buffering potential of trees in local environments, and persistent opportunity to improve environmental justice.
• Our approach helps identify potential neighborhood-level pockets of air pollution that are missed by larger scale, regional air quality monitoring systems.