Hydrochemical characteristics and influencing factors of the river water in the Guijiang

Chemical characteristics of 15 river water samples from the Guijiang are analyzed in April 9-16, 2012. The results show that:(1) The pH values of the river water average in 7.58 and range from 6.36 to 8.46; EC average in 175 μs/cm and range from 18 to 316 μs/cm; the SIc average in -0.7 and change in accordance with the distribution of carbonate rocks in the basin; (2)The hydrochemistry type belongs to HCO3- Ca, and the average HCO3-and Ca2+ contents, accounting for 76% and 77% of all the anions and cations respectively on average, mainly originate from the weathering of rocks; (3) The values of NO3-and SO42-, possibly being affected by human activities such as agriculture and industry, are a little higher in the middle reaches of the Guijiang river; (4)Because of the influence of carbonate rock, the contents of Ca2+, Mg2+ and HCO3-are higher in the middle reaches and lowerin the upstream and downstream generally. The contents of SO42- and NO3- are higher only in the tributaries that affected by human activities in the middle reaches. The contents of Cl-, Na+ and K+ are higherin the middle and lower reaches, but relatively lower in the upper reaches.