TY - JOUR
T1 - Light attenuation - A more effective basis for the management of fine suspended sediment than mass concentration?
AU - Davies-Colley, Robert J.
AU - Ballantine, Deborah J.
AU - Elliott, Sandy H.
AU - Swales, Andrew
AU - Hughes, Andrew O.
AU - Gall, Mark P.
PY - 2014
Y1 - 2014
N2 - Fine sediment continues to be a major diffuse pollution concern with its multiple effects on aquatic ecosystems. Mass concentrations (and loads) of fine sediment are usually measured and modelled, apparently with the assumption that environmental effects of sediment are predictable from mass concentrations. However, some severe impacts of fine sediment may not correlate well with mass concentration, notably those related to light attenuation by suspended particles. Light attenuation per unit mass concentration of suspended particulate matter in waters varies widely with particle size, shape and composition. Data for suspended sediment concentration, turbidity and visual clarity (which is inversely proportional to light beam attenuation) from 77 diverse New Zealand rivers provide valuable insights into the mutual relationships of these quantities. Our analysis of these relationships, both across multiple rivers and within individual rivers, supports the proposition that light attenuation by fine sediment is a more generally meaningful basis for environmental management than sediment mass. Furthermore, optical measurements are considerably more practical, being much cheaper (by about four-fold) to measure than mass concentrations, and amenable to continuous measurement. Mass concentration can be estimated with sufficient precision for many purposes from optical surrogates locally calibrated for particular rivers.
AB - Fine sediment continues to be a major diffuse pollution concern with its multiple effects on aquatic ecosystems. Mass concentrations (and loads) of fine sediment are usually measured and modelled, apparently with the assumption that environmental effects of sediment are predictable from mass concentrations. However, some severe impacts of fine sediment may not correlate well with mass concentration, notably those related to light attenuation by suspended particles. Light attenuation per unit mass concentration of suspended particulate matter in waters varies widely with particle size, shape and composition. Data for suspended sediment concentration, turbidity and visual clarity (which is inversely proportional to light beam attenuation) from 77 diverse New Zealand rivers provide valuable insights into the mutual relationships of these quantities. Our analysis of these relationships, both across multiple rivers and within individual rivers, supports the proposition that light attenuation by fine sediment is a more generally meaningful basis for environmental management than sediment mass. Furthermore, optical measurements are considerably more practical, being much cheaper (by about four-fold) to measure than mass concentrations, and amenable to continuous measurement. Mass concentration can be estimated with sufficient precision for many purposes from optical surrogates locally calibrated for particular rivers.
KW - Aquatic optics
KW - Diffuse pollution
KW - Light attenuation
KW - Light penetration
KW - Suspended sediment
UR - http://www.scopus.com/inward/record.url?scp=84901485356&partnerID=8YFLogxK
U2 - 10.2166/wst.2014.096
DO - 10.2166/wst.2014.096
M3 - Article
C2 - 24804661
AN - SCOPUS:84901485356
SN - 0273-1223
VL - 69
SP - 1867
EP - 1874
JO - Water Science and Technology
JF - Water Science and Technology
IS - 9
ER -