Pollutant Associations with Particulates in Stormwater

Abstract

Many studies have identified metals in urban runoff as a major contributor to the degradation of urban streams and rivers. Metals of most concern are copper, cadmium, chromium, lead, mercury, and zinc. Metals in urban runoff can occur as dissolved, colloidal and particulate-bound species. Therefore, it is important to measure all forms of heavy metals, especially the particulate and filterable fractions, when determining their fate and effects.The objectives of these tests were to determine the associations of heavy metals (along with some major constituents and nutrients) with different-sized particulates using cascade sieves and filters. Sequential extraction experiments were also conducted to examine the treatability and other characteristics of the filterable (<0.45 µm) portion of the heavy metals using Chelex-100 resin, UV-light exposure, and Anodic Stripping Voltammetry (ASV).Preliminary results show that total phosphorus and chemical oxygen demand are associated with the particulates and in general decrease with a decrease in particle size. Obviously, concentrations should all decrease with filtration. However, there were periodic jumps in concentrations for some conditions, reflecting variability in the analytical method and the sample handling. Results using ASV show the metals of concern (Zn, Cd, Pb and Cu) all present in the dissolved (<0.45µm) fraction of the stormwater samples with Zn normally present in the highest concentration. Exposure of the samples to UV light increases the concentration of most of the metals, indicating a dissociation of metals from organic complexes or colloids.

Effects of Urban Non-Point Source Pollution from Baoding City on Baiyangdian Lake, China

“…(1) Runoff Simulation SWMM uses the St. Venant equations for flow simulation [32,33]. The St. Venant equations represent the principles of conservation of momentum (Equation (1)) and conservation of mass (Equation (2)) ∂y ∂x…”

Don't Throw the Baby Out with the Bathwater—Sample Collection and Processing Issues Associated with Particulate Solids in Stormwater

“…The intermediate fraction (0.45 µm to 106 µm) was therefore used in the Coulter Counter analyses, with no possible interference from large particles. The relatively small fraction of particles >106 µm are therefore quantified and added to the size distribution (the <0.45 µm dissolved fraction is reported as TDS, but filtered pollutants are not all ionic as the filtrate contains colloids and chemical complexes; see Morquecho 2005). Figure 8 is a photograph of filtering a sample portion through a 106 µm sieve (as the general upper limit of the Coulter Counter, and the upper limit of TSS, and to protect the 140 µm aperture in the Coulter Counter from clogging).…”

“…PSD data from other stormwater research projects were also included in this summary (Morquecho 2005;Pitt and Cai 2013;Pitt et al 2014;Eppakayala 2015;Selbig et al 2016). …”

Southeastern United States Observations of Stormwater Pollutant Strengths by Particle Size

“…The probability plots show a wide range of specific gravities (about 1.3 g/cc to 6 g/cc for the 5th percentile to the 95th percentiles). Figure 3 shows the results of total phosphorus for fourteen urban residential and commercial area sheetflow samples analyzed by Morquecho (2005). The general trend is a decrease in overall concentration as finer and finer particles are removed.…”