Laboratory study of impacts of concrete fragment sizes on wetland water chemistry

Abstract

This study investigated the effects of urban concrete materials, of different particle sizes, immersed in water through a laboratory-based experiment. Water was sourced from a high conservation-value wetland (Blue Mountains upland swamp). Prior to the experiment, wetland water was dilute (32.5 μS/cm), acidic (pH 5.3) and had detectable major ion concentrations of only sodium and chloride. Water was exposed to three treatments of different concrete fragment sizes (whole, crushed and fine). All treatments increased conductivity and pH and also resulted in modified ionic composition where calcium, potassium, hydroxide, carbonate and sulphate were recorded at much high levels. The extent and speed of water chemistry changes was linked to the particle size of the concrete. The results of this study support the hypothesis that concrete can be an environmentally hazardous material influencing water quality in urban catchments.

Keywords:

• Urban stream syndrome
• alkalization
• storm water
• geochemistry
• dissolution

Acknowledgements

The authors aknowledge and pay their respects to the traditional custodians of the land in which this study was conducted, the Darug, Gundungarra and Wiradjurri people and their elders past and present. The authors thank Western Sydney University for funding the major ionic tests and Envirolab Services for conducting the testing. The authors also thank NSW National Parks and Wildlife for permission to collect water samples in Blue Mountains National Park.