RESUMO
To reveal the Beijing-Hangzhou Grand Canal natural water chemistry characteristics and the influence of human activities, river samples from Xuzhou to Jiaxing were collected in 2019-2020. Simultaneously, the water chemistry data of the canal from 1959 to 1962 and 1975 to 1977 in the Suzhou, Wuxi, and Changzhou sections and the recent social and economic data of the major cities along the canal were collected and analyzed. The results showed that the type of hydrochemistry in the study area was mainly influenced by the weathering of carbonate rocks in the basin, but K++Na+ accounted for 40.39% of the cation equivalent concentration, which was higher than that in ordinary surface water, thereby indicating that the natural hydrochemistry of the canal had been significantly affected by human factors. Spatially, the major ion mass concentrations, total hardness, and total alkalinity of the Grand Canal from Xuzhou station to the downstream area tended to decrease overall, but the parameters at Wuxi and Suzhou stations increased significantly. It was found that Na+ and SO42- were increased by approximately 16 and 12 times and total dissolved solids was increased by nearly 3 times by analyzing the 60 years of water chemistry of the Suzhou, Wuxi, and Changzhou sections. The current (Ca2++Mg2+)/HCO3- ratio in the Suzhou, Wuxi, and Changzhou sections is generally greater than 1, which is significantly higher than that from 1959 to 1962, thereby reflecting the results of human activities. According to the analysis of the social and economic development of the Grand Canal, this change was the result of the accelerated weathering of carbonate rocks in the basin caused by the sulfur oxides discharged by human activities. Further statistical analysis showed that urban domestic sewage and industrial wastewater discharge were the main driving factors causing chemical salinization of natural water in the Grand Canal. This study can provide a scientific basis for coordinating urban development and protecting the water ecological environment of the Grand Canal Basin.
