Targeted and nontargeted approaches to uncover complex halogenated pollutants in the historically endangered California brown pelican

Abstract

Historically, California brown pelicans experienced reproductive failure and population decline induced by the pesticide dichlorodiphenyltrichloroethane (DDT). Although the population recovered after the 1972 DDT ban, nontargeted analytical methods have identified over 45 DDT-related compounds (DDT+) and other typically unmonitored halogenated organic compounds (HOCs) in regional upper trophic level wildlife species, presumably originating from the persistent and chemically-complex DDT manufacturing waste deposited in the Southern California Bight (SCB). However, there is limited data on DDT+ in previously endangered bird populations, including the brown pelican. We identified 183 HOCs in seven brown pelican liver samples (131 ± 48, mean ± SD) via nontargeted analysis. Seventeen DDT+ compounds were identified, including four tris(4-chlorophenyl)methane (TCPM)-related compounds, and 17 polychlorinated terphenyls (PCTs), all of which were not assessed in prior pelican research. Quantitative targeted analysis was conducted for three classes: DDT+, polychlorinated biphenyls (PCB), and polybrominated diphenyl ethers (PBDE). Among these three classes, DDT+ was the dominant chemical class (∑₁₃DDT+, 0.56-197 μg/g lw), followed by (∑₁₄PCB, 0.24-96 μg/g lw), and (∑₆PBDE, 0.01-5.61 μg/g lw). ∑₁₃ DDT+ primarily consisted of p,p'-DDE (77 % ± 15 %), 4,4',4″-TCPM (12 % ± 10 %), p,p'-DDMU (6 % ± 3 %), and 4,4',4″-TCPMOH (5 % ± 6 %). These results demonstrate the continuous exposure of known historical HOCs and a chemically diverse set of under-monitored HOCs, including DDT+. Additionally, levels of detection are consistent with recent wildlife studies in the region, suggesting pervasive contamination of a unique profile of HOCs throughout the SCB food web.

Keywords: DDT+; Dichlorodiphenyltrichloroethane (DDT); GC×GC/TOF-MS; Halogenated organic compounds; Southern California Bight; tris(4-chlorophenyl)methane (TCPM); tris(4-chlorophenyl)methanol (TCPMOH).