Stormwater runoff quality from copper roofing, auckland, New Zealand

摘要

Copper (Cu) roofing materials have traditionally been used in New Zealand for institutional roofing, but are now increasingly used on domestic dwellings. The potential contribution to Cu contamination in urban catchment systems was assessed by measuring dissolved and acid-soluble Cu concentrations in the runoff from three full Cu roofs, and one concrete tile roof with Cu guttering, as a function of time during multiple rain events. Full Cu roofs generated runoff with concentrations of up to 7690 mu g/litre Cu, predominantly present as dissolved, free Cu2+ owing to the low pH of the rainwater runoff. Runoff from the concrete tile roof with Cu guttering generated up to 590 mu g/litre Cu, and the portion of dissolved and free Cu2+ was less owing to the pH buffering effect of the cement-based roofing material. A "first flush" effect was demonstrated in many rain events, where initial runoff had elevated concentrations of both dissolved Cu and particulate Cu, in the form of inorganic Cu minerals and organic Cu-rich aggregate particles.