Evaluation of lead concentration in runoff from painted structures

Urban stormwater runoff is considered to be a major input source of heavy metals to surface waterways. In this study, lead runoff from painted structures in an urban setting was assessed. In many cases, high lead concentrations were found. Lead concentrations (100 ml over 1600 cm2) from 169 different structures followed the order (geometric mean, median, Q10–Q90): wood (40, 49, 2.6–380 μg/l)>brick (22, 16, 3.3–240 μg/l)>block (9.7, 8.0, <2–110 μg/l). Lead concentration depended strongly on paint age and condition. Lead levels from washes of older paints were much higher than from freshly painted surfaces, which were demonstrated quantitatively as: paint age [>10 y] (77, 88, 6.9–590 μg/l) [5–10 y] (22, 16, <2–240 μg/l)>[0–5 y] (8.4, 8.1, <2–64 μg/l). Lead from surface washes was found to be 70% or greater in particulate lead form, suggesting the release of lead pigments from weathered paints. High intensity washes were found to liberate more particulate lead than lower intensities. Old surface paints can contribute high masses of lead into a watershed, targeting these structures for source preventive actions to curtail future lead input into the environment.