Abstract: Natural organic matter (NOM) is of great significance in water treatment processes. Concentrations and molecular compositions of NOM may vary significantly with time. In particular, the seasonal variations of NOM compositions are site specific and unique to individual source water. In this study, molecular compositions and seasonal variations of NOM in source water from Queshan Reservoir in Shandong were investigated by using electrospray ionization coupled to Fourier transform ion cyclotron resonance mass spectrometry (ESI-FT-ICR-MS). The results demonstrated that various C, H, O-only molecules were the major components in the source water NOM. The van Krevelen diagram showed that compounds corresponding to biopolymers such as lignin were the most abundant components in the source water NOM. From winter to summer, the H/C ratio decreased with a concomitant increase in double bond equivalent (DBE), indicating that the molecules in corresponding seasonal samples became more unsaturated. Understanding NOM compositions and its seasonal variations in source water will help to develop effective strategies for drinking water treatment operation and ensure to meet the requirements of drinking water quality.

Key words: leaf area index, Penman-Monteith equation, scaling up, evapotranspiration