Old Concrete Can Have Second Life Protecting Nature

Usually we think of demolished concrete walls and floors as environmental contaminants, but in fact this material may turn out to be a valuable resource in nature protection work. This is the conclusion from researchers from University of Southern Denmark after studying the ability of crushed concrete to bind phosphorus.

"We have shown that crushed concrete can bind up to 90 per cent of phosphorus, "says PhD student and environmental engineer, Melanie Sønderup, Department of Biology at the University of Southern Denmark. Since March 2013 researchers have tested the technique in a full-scale experiment, which will run until March 2014. But already now they find that the technique is very effective.

Large amounts of phosphorus can be washed out into lakes and streams when it rains. Rainwater that runs off from catchments, especially those fertilized with phosphorus, carries the phosphor with it. This phosphorus rich rainwater is then often collected in rainwater ponds, which discharges into lakes and streams. "The water in these rainwater ponds can be very rich in phosphorus, and if it is discharged into a lake, it can lead to an increase in algae growth. This can lead to oxygen depletion and a reduction in the number of species that can live in the water," explains Melanie Sønderup and continues:

"By letting the pond water pass through a filter of crushed concrete, we can remove up to 90 per cent of the phosphorus". Phosphorus binds so well to the concrete because it contains cement. Cement is rich in calcium and also contains aluminum and iron. All three can bind phosphorus. Preliminary results show that the size of concrete grains is of importance. The smaller the grains the better they bind phosphorous. Fine concrete powder is thus more effective than millimeter sized concrete bits.

"It is also important that we do not use concrete that has been exposed to wind and rain for a long time, as this washes out the cement, which holds the essential calcium," explains Melanie Sønderup. As the experiments have only run for six months, the scientists do not yet know the durability of crushed concrete, but they believe that a filter of crushed concrete can last for a long time, probably several years. "Only when the concrete cannot bind more phosphorous, it will be time to switch to a new layer of crushed concrete - and then the disposed layer can be recycled as road fill", says Melanie Sønderup.

http://www.enn.com/wildlife/article/46346

Plants Do Math to Survive the Night

Plants use a chemical calculator to divide their amount of stored energy by the length of the night and thereby solve the problem of how to portion out their energy reserves overnight.

Biologists from the John Innes Centre in England discovered that plants have a biological process which divides their amount of stored energy by the length of the night. This solves the problem of how to portion out energy reserves during the night so that the plant can keep growing, yet not risk burning off all its stored energy. While the sun shines, plants perform photosynthesis. In this process, the plants convert sunlight, water and carbon dioxide into stored energy in the form of long chains of sugar, called starch. At night, the plants burn this stored starch to fuel continued growth.

“The calculations are precise so that plants prevent starvation but also make the most efficient use of their food,” study co- author Alison Smith said in press release. “If the starch store is used too fast, plants will starve and stop growing during the night. If the store is used too slowly, some of it will be wasted.”

To give the foliage a math quiz, the biologists shut off the lights early on plants that had been grown with 12-hour days and nights. Plunging the plants into darkness after only an 8-hour day forced them to adjust their normal nightly rhythm. Since the plants didn’t have time to store as much starch as usual, they had to recalculate their metabolism.

Even after this day length trickery, the plants aced their exams and ended up with just a small amount of starch left over in the morning. They had neither starved, nor stored starch that could have been used to fuel more growth.

The plants weren’t doing anything consciously. Instead, chemical reactions did the number crunching automatically. The results of the study will be published in eLife, and can currently be read via the Cornell University Library.

The authors suggested that similar biological calculators may explain how a migratory bird, the little stints (Calidris minuta) can make a 5000-kilometer journey to their summer habitat in the Arctic and arrive with enough fat reserves to survive only approximately half a day more, on average.

http://news.discovery.com/earth/plants/plants-do-math-to-survive-the-night-130624.htm

The Performative Ground: Rediscovering The Deep Section

Deep Urbanism is a reading of the city that acknowledges the complex ecological and biogeochemical processes taking place above, below and within the urban ground. In the city, nothing can simply be placed on the surface; the composition of the urban ground requires that structures inevitably extend deep into a complex mix of disturbed soil horizons, construction rubble, pipes, subways, utilities. The most innocent-looking walkway may sit on 30-foot piles driven deep into silty soil; small hillocks might be braced with highly engineered geotextiles. A simple meadow may require the complete reconstruction of a “natural” soil profile; a sunken garden may require drainage infrastructure and thousands of pounds of concrete to keep the water table at bay. Much of the action of landscape is deep underground, buried in space or time.

Read more: http://landscapeurbanism.com/article/the-performative-ground/">