LIGHT-ABSORPTION BY YELLOW SUBSTANCE IN STORM RUNOFF FROM LOG HANDLING AREAS AT A TIMBER EXPORT PORT, TAURANGA, NEW-ZEALAND

Spectral values of light absorption by yellow substance at near ultrav iolet 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 monit oring yellow substance in storm runoff. As in previous research on nat ural marine and inland waters, the spectral shapes of yellow substance absorption in storm runoff from the wharf log handling areas fitted a n exponential model. The spectral slope varied only slightly, though t he suspended solid concentration of the samples varies from 9.2 to 1,1 00 mg/l. The overall mean g(440) was 17.9 m(-1), 85 and 160-1,280 time s that of natural marine waters in the Tauranga Harbour and around the South Island of New Zealand. The method appears feasible for rapid mo nitoring of yellow substance in storm runoff from log handling areas a nd provides a basis for tracing dispersion of the storm effluent in th e receiving tidal waters.