Yangtze River
On an expedition destined to the search of the endemic White Yangtze River Dolphin (Baiji) in China in November 2006 we investigated the chemical water quality of the middle and lower reaches of the Yangtze, between the Three Gorges Dam and the mouth at Shanghai. In general, the concentrations of almost all parameters measured were in the order of magnitude found in other large world rivers. The reason for the low concentrations in spite of large loads of industrial waste discharge, increasing application of chemicals in agriculture, largely untreated municipal sewage etc. is the dilution by the enormous amount of water carried by the Yangtze.
Dissolved trace metal concentrations in the Yangtze River are still 2 – 8 times lower than those of the Rhine River during peak pollution in the late 1970’s and with few exceptions compare well with concentrations averaged from a large range of world rivers today. The standards recommended by the EC (2006) for selected trace metals are all met. Only few of the 236 organic chemicals tested were found locally at relatively low levels. The concentrations of dissolved and particulate nitrogen increased in the course of the river downstream, whereas concentrations of phosphate were constant at a low level. However, peak concentrations were observed locally originating from point sources and, thus, may be permanent. Actions should be taken investigating the sources and concentration levels of notorious trace metals such as As, Hg, and Tl, which we found to occur locally at increased levels.
Whereas the loads of pollutants are tremendous, the concentrations of most parameters were moderate due to the dilution by the immense water discharge of the river. In spite of low concentrations, 1500 t of nitrogen, 4.6 t of arsenic, 3 t of lead etc. are washed to the East China Sea daily. Due to the dilution, immediate deterioration of the river as an ecosystem and habitat may not be expected for water quality reasons. The enormous loads, however, may take disastrous effect in the Yangtze estuary in the East China Sea, where nitrogen may fuel algae blooms, and trace metals and persistent organic chemicals may accumulate in the food chain of the productive shelf region.
Comparison with earlier investigations from the literature and increase of economic growth, population and living standards suggest that concentrations are on the increase. This will aggravate the situation and affect groundwater and thus, drinking water quality. It is thus imperative that this development is closely monitored and countermeasures initiated as early as possible.
Funding
Collaborator
- Wuhan Institute of Hydrobiology (IHB)
- baiji.org Foundation
- Michael Berg, Eawag, Department W+T
Newspaper articles
- NZZ: Weisser Delfin vermisst [pdf, 531KB]
- Spiegel: Flussdelfin Baiji [pdf, 24KB]
- Süddeutsche Zeitung: Alarm am Jangtse [pdf, 106KB]
- NZZ: Dem Jangtse geht es besser als vermutet [pdf, 532KB]
- Frankfurter allg. Sonntagszeitung: Fluss ohne Wiederkehr [pdf, 721KB]