Impact Of Human Activities Oil Carbon Transport In The Yellow River

Rivers play an important role in the global carbon cycle by linking land andocean systems, which are the two largest carbon reservoirs on the earth’s surface.Nowadays, under server human influences such as reservoir construction andagriculture irrigation, natural ways of riverine material transport are totally changed,so are the carbon input/output balance and sink/source patterns. The Yellow Riverrepresents typically rivers which are located in arid and semiarid regions and holdhigh turbidity. Studies on carbon cycles and influence factors in the Yellow Riverestuary can provide some meaningful advice to other rivers with the samecharacteristics.Using data from field investigations between2003and2012along the YellowRiver mainstream and some continuous observations at the Huayuankou and Lijinstation, we examined the transport features and seasonal variations of organic andinorganic carbon, with a focus on contrasting the impacts of human activities withthose of natural processes. Conclusions are as follows:(1) Different from other large rivers, organic carbon is mainly transported in theparticulate form, and85%of the POC is concentrated in particles with grain sizesmaller than32μm. Due to natural and human influences, DOC correlates weaklywith discharge and it varied as a result of human activities such as agriculturalirrigation and pollution in the whole basin except for the upstream Qinghai-TibetPlateau, where DOC may be influenced by global warming. Organic carbon in theYellow River originates mainly from loess and possesses refractory feature. Labilepart of the organic carbon in reservoirs is much higher compared with that in themainstream, due to more autochthonous contributions.(2) CO2consumption by chemical weathering in the Yellow River basinachieves101.8×109mol/a, to which80%and20%are contributed by carbonate andsilicate, respectively. In addition, although the Qinghai-Tibet Plateau only accountsfor30%of the whole basin area, its CO2consumption by chemical weatheringoccupies more than60%of the total. The Qinghai-Tibet Plateau is probably the originof high HCO3-in the Yellow River and contributes about66%of the riverine DIC flux.The contribution from the Loess Plateau was overestimated in the previous studies. Inaddition, we also speculate that, due to global warming, contributions from the Qinghai-Tibet Plateau to the chemical weathering and DIC flux of the Yellow Riverwill probably increase in the future.(3) In the Yellow River, inorganic carbon is mainly transported in the dissolvedform. High DIC in the Qinghai-Tibet Plateau is due to the high chemical weatheringrate, and abundant carbonate in the loess is probably the reason that DIC stays at thehigh level in the middle reach. In addition, influcences of high evaporation in theLoess Plateau can not be neglected. The Yellow River acts as a CO2source comparedwith atmosphere, carbonate system is the main control mechanism.(4) Monthly fluxes of all kinds of carbon in the Yellow River show the samepattern: high in the wet season and low in the dry season. Total carbon flux of theYellow River amonts to133.8×104tC/a, mainly in inorganic and particulate forms.The water and sediment regulation scheme transports about one-third of the annualDOC flux and one half of the POC flux in about20days. In the whole Yellow Riverbasin, inorganci carbon input is much higher that its output, probably due to carbondepositon in the resevoirs and the downstream river channel. As a result, the naturalriverine transport patterns have been altered and ecosystems in the estuarine andcoastal areas have been influenced.