Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

First-ever precise data on Yangtze water quality

05.11.2007
For the first time, a team including foreign scientists has been authorized by the Chinese government to study water quality on the lower reaches of the Yangtze River.

Hundreds of water and sediment samples collected at the end of 2006 have now been analysed by Eawag. The results are remarkable: although pollutant loads are in some cases very heavy, concentrations in the river known as China’s main artery are in the same range as worldwide known from other large rivers.

In the autumn of 2006, as part of the Yangtze Freshwater Dolphin Expedition, Eawag researchers collected water and sediment samples along a 1500-kilometre stretch of China’s longest river. These samples have now been analysed, and the results were presented by the scientistes Michael Berg, Eawag and Wang Ding, China today in Bern at an event organized by the Zurich-based baiji.org Foundation.

Baiji considered extinct

At the media conference, the leaders of the joint Chinese/Swiss expedition explained the background to, and the significance of, this unique mission. A documentary directed by Florian Guthknecht showed the research team at work during the survey, which confirmed what had already been feared: the team declared the Yangtze River baiji, or white-flag dolphin, “functionally extinct” – a conclusion that caused dismay worldwide and especially in China. However, based on the latest findings, the disappearance of the baiji is not attributable to toxic chemicals in the river – pollution is, at least, certainly not the main factor.

Concentrations comparable to other rivers

In general, concentrations of man-made pollutants in the Yangtze are comparable to those found in other large rivers around the world. Although high concentrations of certain elements and organic compounds were measured at some points, these substances were mostly diluted further downstream. Concentrations of several toxic elements such as arsenic, thallium and antimony increased along the course of the river. Heavy metal concentrations in the Yangtze are currently about two to eight times lower than in the Rhine 30 years ago, when pollution levels peaked. European Union guidelines for several heavy metals are all higher than the concentrations found in the Yangtze, suggesting that even today pollution levels are still significantly higher in many European rivers.

Levels increasing

While the trend has been widely reversed in Europe, with levels of pollutants declining, they are generally still increasing in China. For example, nitrogen concentrations have approximately doubled over the past 20 years. In Shanghai, concentrations of dissolved nitrogen were twice as high as at the Three Gorges Dam, reflecting the increasing use of mineral fertilizers in agriculture, while phosphate concentrations remained constant at a relatively low level along this section of the river. Of the 236 organic chemicals studied, only a few were found locally at high levels. Many of the persistent substances used in agriculture occur only seasonally and were detected in trace concentrations.

4.6 tonnes of arsenic per day

The fact that concentrations of most pollutants appear low by comparison with other major rivers is party due to the vast quantities of water discharged by the Yangtze (yearly average at the mouth = 39 000 m3/second; for comparison, yearly average discharge of the Rhine at Basel = 1050 m3/second). Accordingly, dilution of the anthropogenic chemical inputs means that there is no immediate risk of damage to the ecosystem. However, where the river enters the East China Sea, the huge pollutant loads are expected to have devastating effects: each day, 1500 tonnes of nitrogen is discharged, causing eutrophication and growth of blue-green algae in the coastal waters, while toxic metals such as arsenic (4.6 tonnes discharged per day, despite the low concentrations) and persistent organic compounds accumulate, entering the food chain of the productive shelf areas.

Growing pressure on the Yangtze

Although it is not possible to rule out synergistic effects between different chemicals, long term effects or impacts of endocrine disruptors, which could not be demonstrated by this study, the results provide no direct evidence of a link between chemical water quality and the disappearance of the Yangtze River baiji or the decline of the Chinese sturgeon or the endemic finless porpoise. These losses must rather be attributable to a variety of circumstances, among which the deterioration of chemical water quality may however be a contributory factor. Other factors include the destruction of habitats, heavy canalization, the cutting-off of tributaries (“hatchery” areas for many fish species) by dams, the drainage of lakes and wetlands for agriculture, overfishing and unselective fishing methods, and heavy shipping traffic. In general, pressure on the Yangtze is growing as a result of industrialization, rising living standards, artificial irrigation and increasing power generation. The planned large-scale diversion of water to the Yellow River valley in the North would also have serious consequences. Water shortages in the Yellow River have become so severe that it fails to reach the sea for several months each year.

In the Yangtze, concentrations of nitrogen, metals and organic compounds are increasing, as shown by comparisons with earlier measurements in the literature. This will further increase the pressure on the river ecosystem – and especially on the coastal waters of the East China Sea – and also affect the quality of groundwater and drinking water supplies. It is therefore essential to monitor these developments and take “at-source” measures as soon as possible so that current trends can be reversed.

Andri Bryner | alfa
Further information:
http://www.baiji.org
http://www.eawag.ch

More articles from Ecology, The Environment and Conservation:

nachricht Bioinvasion on the rise
15.02.2017 | Universität Konstanz

nachricht Litter Levels in the Depths of the Arctic are On the Rise
10.02.2017 | Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

From rocks in Colorado, evidence of a 'chaotic solar system'

23.02.2017 | Physics and Astronomy

'Quartz' crystals at the Earth's core power its magnetic field

23.02.2017 | Earth Sciences

Antimicrobial substances identified in Komodo dragon blood

23.02.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>