Tracing Crustal and Anthropogenic Sources of Metal(loid)s in Hurricane Harvey Floodwater Remnants in Houston, Texas

Probable sources of metal-(loid) contamination in Hurricane Harvey floodwater remnants from diverse land use settings in Houston, Texas, were investigated. The primary novelties of this work are that we (i) analyzed a wide suite of 51 elements, including rare earths and (ii) implemented two independent multivariate statistical techniques to obtain clues to metal-(loid) sources. This approach differs from many previous studies that simply reported the concentrations of a limited number of metals in hurricane floodwaters. Hierarchical cluster analysis and principal component analysis both resolved three major and statistically distinct source categories: crustal materials, vehicular emissions, and the built environment. The crustal source was confirmed using light rare earth ternary diagrams, yttrium/holmium ratios, cerium and europium anomalies, and Oddo-Harkins patterns. The influence of motor vehicles and traffic was identified using enrichment factors and simultaneous barium-cadmium-antimony and gallium-cadmium-antimony three-component variations. Efflux from the built environment was validated via signature elemental ratios and zinc-tin-lead ternary variations. Overall, the deluge appears to have mobilized metal-(loid)-s with vehicular residues and building materials contributing substantially to floodwater contamination beyond natural crustal dissolution. The source attribution framework developed herein provides a generalized approach to identify metal-(loid) sources in any flood-prone urban environment.