Light-scattering components and Secchi depth implications in Onondaga Lake, New York, USA
Effler, Steven W.; Peng, Feng
published: Jan 1, 2012
ArtNo. ESP141017904002, Price: 29.00 €
The dynamics of light scattering attributes of minerogenic particles in the upper waters of an urban lake, Onondaga Lake, NY, U.S.A., are characterized for the spring-summer interval of 2010 with scanning electron microscopy interfaced with automated image and X-ray analyses (SAX). SAX results are used to estimate the minerogenic scattering coefficient (bm) through Mie theory calculations. Good optical closure of the summation of bm and organic particle scattering (bo), the latter estimated by empirical bio-optical models based on the concentration of chlorophyll-a, with paired bulk measurements of particulate scattering (bp) is demonstrated. The average of the ratio of (bm + bo) to bp was 1.07; the average percent difference between this summation and bp was 21 %. The contribution of bm to bp ranged from ∼5 % during a dry weather interval to 70 % following a runoff event; the overall average, for the relatively low runoff study year, was nearly 25 %. Allochthonous clay mineral particles were the dominant minerogenic component, primarily responsible for the observed dynamics in bm. Calcium carbonate containing particles, with nuclei as clay minerals primarily and organic particles secondarily, were the second most important contributor to bm. Particles in the size range of 1-10 μm were responsible for bm during low tributary flow intervals, but particles > 10 μm became important following high runoff events. A strong inverse relationship between Secchi depth and bp prevailed, coupling this fundamental metric of water quality to the contributions of the various light scattering constituents. The light scattering and clarity conditions of the lake are considered in the context of prevailing and potential future driving conditions.