Storm impacts upon the composition of organic matrices in Nagara River—A study based on molecular weight and activated carbon adsorbability

The impacts of a heavy storm of rain on the composition of natural organic matter (NOM) in Nagara River water were studied in terms of molecular weights (MWs) and activated carbon (AC) adsorbabilities using six water samples collected during a critical Typhoon weather condition. The composition in MWs was analyzed using a HPSEC system and that in adsorbabilities was characterized using parameters devised to reflect NOMs average adsorptive strength (KM), adsorptive strength polydispersity ((sigma)), affinity to AC (1/n) and non-adsorbable fraction (Cnon/CT0), respectively. These parameters were determined by model description of observed isotherms with a distributed fictive component method. The heavy storm of rain brought higher content of larger organic components into the river source, thus causing changes of NOMs weight-averaged MWs in the range of 2962–3495 Dalton and MW polydispersity in the narrow range of 1.153–1.226. Comparison of KM and (sigma)values for all samples assessed with both indices of TOC and UV260 showed that large proportions of the storm-induced organic components had adsorptive strengths similar to those existent before the storm, with the presence levels for components revealing much strong and weak adsorbabilities being low. Among all organic components brought into the river by the storm of rain, the percentages of non-adsorbable ones was lower (smaller Cnon/CT0 values); and the adsorbable ones had generally more affinity to the adsorbents used (smaller 1/n values).