Nitrogen content of suspended matter in the Kam Tin River, Hong Kong

Abstract

There is little information about the physical and chemical properties of suspended matter in the streams and rivers of Hong Kong. Observations have been made in the Kam Tin drainage basin of the nitrogen content of suspended matter near the settlement of Kam Tin in the developed lowland area of the basin. The median %N of the suspended matter was 4.27 (n = 53) and 1.7 (n = 58) for stable flow and storm flow samples, respectively. Two small upland streams have been sampled and they afford an interesting contrast to the lowland site. At the KARC stream, where secondary woodland dominates, stable flow and storm flow sediment samples have median %N values of 1.01 (n = 49) and 0.97 (n = 154), respectively. A second small undisturbed upland stream (RDH) has a storm period median %N value of 0.61 for suspended matter where n = 38. The data show evidence of spatial variation in the nitrogen content of suspended matter in the Kam Tin basin and enrichment compared to soil and regolith materials. Comparison of N in suspended matter to fresh leaves reveals depletion of N in suspended sediment with the exception of samples collected under stable flow conditions at Kam Tin.