Geochemistry of the dissolved load of the Changjiang Basin rivers: Anthropogenic impacts and chemical weathering

Diatoms modify the relationship between dissolved silicon and bicarbonate in the impounded rivers

“…However, the stoichiometry in rivers of other elements such as Ca:Na, K:Na and Cl:Na are widely used as markers of chemical weathering processes (Gaillardet et al, 1999;Han and Liu, 2004;Chetelat et al, 2008). Therefore, in this study we present the hypothesis that DSi and HCO 3 -are linked in river-reservoir system, this biogeochemical linkage reflecting not only their external geological resource but also the influence of algal activity within the river.…”

Chemical weathering under mid- to cool temperate and monsoon-controlled climate: A study on water geochemistry of the Songhuajiang River system, northeast China

“…8 and 9) compared with the world's large rivers. However, the calculated silicate weathering rate (TDS sil , 2.23 t km À2 a À1 ) is much lower even when compared with rivers draining carbonate dominated basins, such as Wujiang [6.0 t km À2 a À1 , (Han and Liu, 2004)] and Xijiang Gaillardet et al (1999b) for Huanghe, Chetelat et al (2008) for Changjiang, and Xu and Liu (2010) for Xijiang.…”

“…Calcium, Mg and HCO À 3 are conventionally considered to be insensitive to human pollution (Roy et al, 1999). Moreover, the content of TDS reflects the different lithologies in the basin and can be used as an index of land use and the effects of human activities on the water quality (Gaillardet et al, 1999a,b;Han and Liu, 2004;Chetelat et al, 2008). Variation of the NO À 3 concentration in the three main streams is shown in Fig.…”

“…Chemical weathering of silicates, therefore, is known as the dominant long-term sink for atmospheric CO 2 and thus the dominant regulator of the green-house effect over geological time-scales Godderis et al, 2003). Accordingly, estimation of the present-day rates of silicate weathering and characterization of its controlling factors are crucial in interpreting and predicting past and future changes in global climate (Chetelat et al, 2008;Moon et al, 2009). …”

“…However, strong tectonic and weak climatic control could be observed under temperate climate (Riebe et al, 2001) and temperature may have a negative action on silicate weathering for river basins in a cold climate . In China, chemical weathering has been studied for river basins under subtropical climate, warm temperate climate and also a plateau climate (Han and Liu, 2004;Wu et al, 2005;Liu, 2007, 2010;Chetelat et al, 2008), but information on chemical weathering under mid-or cool temperate climate is still insufficient. So, more work should be carried out to understand the controlling mechanisms under different climatic regimes.…”