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 Conservationists are sounding the alarm: parrots much more threatened than assumed
15.09.2017 | Justus-Liebig-Universität Gießen

nachricht A new indicator for marine ecosystem changes: the diatom/dinoflagellate index
21.08.2017 | Leibniz-Institut für Ostseeforschung Warnemünde

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: The pyrenoid is a carbon-fixing liquid droplet

Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.

A warming planet

Im Focus: Highly precise wiring in the Cerebral Cortex

Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.

The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...

Im Focus: Tiny lasers from a gallery of whispers

New technique promises tunable laser devices

Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...

Im Focus: Ultrafast snapshots of relaxing electrons in solids

Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!

When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...

Im Focus: Quantum Sensors Decipher Magnetic Ordering in a New Semiconducting Material

For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.

Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

“Lasers in Composites Symposium” in Aachen – from Science to Application

19.09.2017 | Event News

I-ESA 2018 – Call for Papers

12.09.2017 | Event News

EMBO at Basel Life, a new conference on current and emerging life science research

06.09.2017 | Event News

 
Latest News

Rainbow colors reveal cell history: Uncovering β-cell heterogeneity

22.09.2017 | Life Sciences

Penn first in world to treat patient with new radiation technology

22.09.2017 | Medical Engineering

Calculating quietness

22.09.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>