Dutch Town Lays Air-Purifying Concrete 295
eldavojohn writes "In an effort to combat air pollution, a Dutch town has paved some of its streets with air-purifying concrete. It contains a titanium dioxide-based additive that utilizes sunlight to turn car exhaust into harmless nitrates. It was shown to do this in a lab and now the scientists are interested in just how much this will affect the air quality around the road. They will sample the air quality by a normal road and by this newly paved one."
Exact location (Score:4, Informative)
The road is here [google.com] according to a Dutch source [nieuwsbank.nl].
Re:Nitrates? (Score:2, Informative)
harmless nitrates ? (Score:5, Informative)
not to mention all the side products that are produced, msot of which i am willing to bet havenot even been identified, much less studied
J Environ Qual. 2008 Feb 11;37(2):291-5. Print 2008 Mar-Apr.Click here to read Links
When does nitrate become a risk for humans?
Powlson DS, Addiscott TM, Benjamin N, Cassman KG, de Kok TM, van Grinsven H, L'Hirondel JL, Avery AA, van Kessel C.
Soil Science Dep, Rothamsted Research, Harpenden, Herts, UK.
Is nitrate harmful to humans? Are the current limits for nitrate concentration in drinking water justified by science? There is substantial disagreement among scientists over the interpretation of evidence on the issue. There are two main health issues: the linkage between nitrate and (i) infant methaemoglobinaemia, also known as blue baby syndrome, and (ii) cancers of the digestive tract. The evidence for nitrate as a cause of these serious diseases remains controversial. On one hand there is evidence that shows there is no clear association between nitrate in drinking water and the two main health issues with which it has been linked, and there is even evidence emerging of a possible benefit of nitrate in cardiovascular health. There is also evidence of nitrate intake giving protection against infections such as gastroenteritis. Some scientists suggest that there is sufficient evidence for increasing the permitted concentration of nitrate in drinking water without increasing risks to human health. However, subgroups within a population may be more susceptible than others to the adverse health effects of nitrate. Moreover, individuals with increased rates of endogenous formation of carcinogenic N-nitroso compounds are likely to be susceptible to the development of cancers in the digestive system. Given the lack of consensus, there is an urgent need for a comprehensive, independent study to determine whether the current nitrate limit for drinking water is scientifically justified or whether it could safely
This isn't that new (Score:3, Informative)
Re:Nitrates? (Score:5, Informative)
"One thing I am worried about, though, is the color of these sidewalks. If they're using titanium dioxide, shouldn't they be a nice brown color?"
Actually titanium dioxide is quite white. It is used as pigment for white base paint.
Re:Offset? (Score:4, Informative)
The Titanium is not consumed in this process (merely a catalyst) so it might very well be worth it in the long run..
Re:TFA interesting but light on details (Score:5, Informative)
http://en.wikipedia.org/wiki/Photocatalysis [wikipedia.org]
http://en.wikipedia.org/wiki/Titanium_dioxide [wikipedia.org]
TiO2 can catalyze a wide variety of chemical reactions in the presence of ultraviolet light (such as sunlight).
Don't worry, though. It's completely harmless. (Score:5, Informative)
Harmless... [wikipedia.org]
In freshwater or estuarine systems close to land, nitrate can reach high levels that can potentially cause the death of fish. While nitrate is much less toxic than ammonia or nitrite, levels over 30 ppm of nitrate can inhibit growth, impair the immune system and cause stress in some aquatic species.[citation needed] However, in light of inherent problems with past protocols on acute nitrate toxicity experiments, the extent of nitrate toxicity has been the subject of recent debate.
In most cases of excess nitrate concentrations in aquatic systems, the primary source is surface runoff from agricultural or landscaped areas which have received excess nitrate fertilizer. These levels of nitrate can also lead to algae blooms, and when nutrients become limiting (such as potassium, phosphate or nitrate) then eutrophication can occur. As well as leading to water anoxia, these blooms may cause other changes to ecosystem function, favouring some groups of organisms over others. Consequently, as nitrates form a component of total dissolved solids, they are widely used as an indicator of water quality.
What could possibly go wrong, though? It's not like roadways are "surfaces" that might "runoff" into storm sewers or waterways.
Re:Offset? (Score:3, Informative)
You should have. They're only paving one side of the street with it. This way they can test the air quality on either side of the street and see if there's any difference.
It's an experiment.
Couldn't see anyone doing 'testing' in a town in the US without two very big teams of lawyers being involved.
Yeah innovation!
Re:Offset? (Score:3, Informative)
Actually, there's a recurring cost for the concrete as well: it doesn't last forever, you know! It lasts longer than asphalt concrete, but it'll still need to be repaved after a few decades.
(At least, it doesn't last forever the way we use it -- if we built like the Romans did, it'd last forever but cost a heck of a lot more.)
Re:Offset may be ideal (Score:3, Informative)
I doubt this takes the asbestos from brakes out of the air though
They haven't used asbestos in brake linings [wikipedia.org] for a long time.
Re:Nitrates? (Score:2, Informative)
Re:Offset? (Score:5, Informative)
Because it's a flow restriction and the engine has to work to pump through it. In fact, particulate filters and catalytic converters and mufflers on new US diesel trucks harm the efficiency so much that it can do as much as 4 mpg damage.
Re:Nitrates? (Score:3, Informative)
Of [epa.gov]
course [epa.gov]
nitrates [wi.gov]
are [state.wi.us]
harmless! [state.ne.us]
Re:Offset? (Score:5, Informative)
The catalytic converter isn't as efficient as a straight pipe. While not legal, cutouts that push exhaust straight outside the engine and bypass the exhaust system do improve horsepower.
It's more like bumping up the speed of your front side bus on your CPU. If you have a slower FSB, you might not ever notice it if you aren't racing your ca... CPU. But when you need that speed, it sure would be nice to remove the FSB limitation.
That said, the amount of good that catalytic converters do means we should probably keep them, as they aren't a huge drain on the power of a vehicle.
Re:Nitrates? (Score:5, Informative)
a) Not all of Holland is below sea level, 75% of it is above sea level.
b) Nitrates can still pollute the ground water then diffuse into the ocean and rivers
Comment removed (Score:2, Informative)
Re:Offset? (Score:4, Informative)
How, exactly, is removing the catalytic converter (which acts on the engine's exhaust just before it is expelled to the atmosphere) supposed to help improve engine efficiency?
The same way removing your muffler does - both the muffler and the catalytic converter restrict the flow of exhaust in the car (thereby restricting the intake, and subsequently reducing the amount of power the car can generate). NASCAR teams remove the mufflers and catalytic converters from cars [howstuffworks.com] - adding about 50HP to the car in the process.
Re:Offset? (Score:2, Informative)
The original Crown Jewels contained Aluminum because it was a precious metal at the time. A chemical process was developed by Reynold around the 19th/20th century to convert a lot of Aluminum Dioxide into pure Aluminum using a small amount of pure Aluminum.
Re:Offset? (Score:4, Informative)
the pollution incurred from mining the titanium
This is not titanium, it's titanium dioxide which can be mined from the ground in some places. Wikipedia says that "The relatively high market value of titanium is mainly due to its processing" from oxide. Besides that, it's only needed in the surface, no need to fill the whole concret slab, just the layer that'll wear.
Re:Nitrates? (Score:5, Informative)
The recent conclusion of a 37 year experiment is it's phosphorus not nitrogen that's the problem:
http://www.canada.com/victoriatimescolonist/news/story.html?id=381d4ce5-89a2-4901-864e-34239419bf67 [canada.com]
Schindler's latest series of long-term experiments shows that nitrogen removal completely fails to control blue-green algae blooms. He proved this by manipulating nitrogen and phosphorus levels on Lake 227 for 37 years. Nitrogen control, he found, only encouraged algae blooms.
Comment removed (Score:3, Informative)
old news (Score:3, Informative)
In 1972 it was discovered that titanium dioxide is a strong oxidizer when exposed to light. The following years saw this applied to paints used in hospitals, coatings on windows and building concrete.
This is old technology which has been in use in Japan for many years. Yes, it does work.
Re:Offset? (Score:3, Informative)
Am I wrong in thinking I knew an old lady who swallowed a fly? Someone weigh in on this please.
No you're quite right, but not quite for the same reason. Concrete and asphalt already used in the roads are the result of intensive mining, drilling and refining processes already, and titanium can be recoverer/reused, so I'd venture to say that though there would be an added environmental impact to include this "air scrubber" additive that it isn't the biggest factor offseting the benefits to air quality.
I'd say a more immediate concern is that this doesn't reduce pollution--it only converts it into anouther type of pollution. Smog-causing Nitrous oxides are certainly bad for our health, but nitrates are far from "harmless". I'd like to know what is done with the nitrates. Can they be recovered and used in a more controlled way (to fertilise crops and what not) or are they just left to be absorbed by the environment (dissolved in runoff, etc)?
Though proper amounts of nitrates are natural and beneficial in ecosystems, excess nitrates in the environment can destroy wetlands and other bodies of water by causing excess algae growth. Nitrates are also bad for animal life, from fish and amphibians to livestock. Nitrates can infiltrate well-basede drinking water supplies as well, creating health problems in people ranging from thyroid problems and vitamin deficiencies to low birth weights.
If there is some way to contain the nitrates as well as enjoy less smog I'd say it is promising, but we still have to work on more efficiently using fuels and not driving personal vehicles as much when there isn't a need to.
Re:Offset? (Score:3, Informative)
Re:Interesting... (Score:2, Informative)
Re:Offset? (Score:3, Informative)
From Wiki [wikipedia.org]:
These three reactions occur most efficiently when the catalytic converter receives exhaust from an engine running slightly above the stoichiometric point. This is between 14.8 and 14.9 parts air to 1 part fuel, by weight, for gasoline (the ratio for LPG, natural gas and ethanol fuels is slightly different, requiring modified fuel system settings when using those fuels). When there is more oxygen than required, then the system is said to be running lean, and the system is in oxidizing condition. In that case, the converter's two oxidizing reactions (oxidation of CO and hydrocarbons) are favoured, at the expense of the reducing reaction. When there is excessive fuel, then the engine is running rich. The reduction of NOx is favoured, at the expense of CO and HC oxidation. If an engine could be operated with infinitesimally small oscillations[citation needed] about the stoichiometric point for the fuel used, it is theoretically possible to reach 100% conversion efficiencies.