Light Absorption by Yellow Substance in Storm Runoff from Log Handling Areas at a Timber Export Port, Tauranga, New Zealand

Abstract

Spectral values of light absorption by yellow substance at near ultraviolet to visible wavelengths were measured in 22 storm runoff samples from the wharf log handling areas at the Port of Tauranga, New Zealand, to ascertain the feasibility of measuring light absorption for monitoring yellow substance in storm runoff. As in previous research on natural marine and inland waters, the spectral shapes of yellow substance absorption in storm runoff from the wharf log handling areas fitted an exponential model. The spectral slope varied only slightly, though the suspended solid concentration of the samples varies from 9.2 to 1,100 mg/l. The overall mean g₄₄₀ was 17.9 m^-1 85 and 160 - 1,280 times that of natural marine waters in the Tauranga Harbour and around the South Island of New Zealand. The method appears feasible for rapid monitoring of yellow substance in storm runoff from log handling areas and provides a basis for tracing dispersion of the storm effluent in the receiving tidal waters.