Impact of human activities on organic carbon transport in the Yellow River

[摘要] Using data from four field investigations between 2003 and 2009 along theYellow River mainstream, we examined the transport features and seasonalvariations of organic carbon, with a focus on contrasting the impacts ofhuman activities with those of natural processes. Particulate organic carbon(POC) in the Yellow River originated mainly from the Loess Plateau, and thusthe POC content in suspended sediments was much lower than in theworld's other large rivers. Owing to both natural and human influences,dissolved organic carbon (DOC) has only a weak correlation with discharge.DOC varied as a result of human activities such as agricultural irrigationand pollution in the whole basin except for the upstream Qinghai–TibetanPlateau. Our study also suggested that while reservoirs are a POC sink overshort periods, a long-term POC storage flux cannot be easily estimated asdischarge and sediment regulations have completely changed the relationshipbetween the fluxes of water, sediments, and rainfall. However, this carbonsink can be obtained reliably through high-frequency sampling over long timeperiods. In addition, the annual water and sediment regulation (WSR) schemehas imposed an extremely severe human disturbance on the transport patternof river organic carbon. Our study demonstrated for the first time that in aWSR event of less than 20 days, large proportions of the annual DOC (35%)and POC (56%) fluxes of the Yellow River were transported to theestuarine and coastal zone, potentially influencing estuarine and coastalgeochemistry and ecosystems profoundly.

[学科分类] 地球化学与岩石