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.