Measuring solids concentrations in urban runoff : methods of analysis

Various types of solids conveyed with rainfall and snowmelt runoff into receiving waters cause numerous environmental impacts, including reduced sunlight penetration, blanketing of fish spawning substrates, and transport of pollutants contributing to aquatic pollution. For the assessment of such impacts, it is important to measure solids concentrations in both runoff and snowmelt. In this study, accuracies of three analytical methods used to measure solids were assessed: (a) A TSS (total suspended solids) method, (b) Suspended sediment method (SSC-B), and (c) a multiple filter method (MFM). For rainfall runoff samples containing 90% of particles smaller than 5 μm, the MFM measurements produced concentrations significantly higher than those obtained with SSC-B and TSS methods, at a 95% confidence level. In the case of snowmelt runoff, the SSC-B and MFM methods yielded similar concentrations, which were 10-20% higher than those measured by the TSS method, and the coefficient of variation of repeated TSS readings was up to three times higher than that of the former methods. The results indicate the importance of choosing the “best” analytical method for assessing the operational and environmental impacts of solids conveyed by urban runoff and snowmelt.Godkänd; 2011; 20120510 (ysko