Studying how flocculation affects acoustic reflection

May 09, 2013

In inland estuaries and shallow coastal waters, small particles of organic matter, such as organic waste and debris or bacteria, clump together to form an aggregate known as floc. Flocculated particles can span a range of sizes, from a few micrometers to a few millimeters, and the properties and concentration of floc have a strong influence on water quality. To infer the properties of floc particles, researchers have proposed using acoustic backscatter measurements, a common technique for estimating sediment concentrations. To do so, however, requires an understanding of how the properties of floc particles affect acoustic wave reflection.

To find out, MacDonald et al. conducted a series of controlled laboratory experiments studying how high-frequency acoustic waves reflect off floc particles of differing composition, density, and size. They find that floc particles reflect differently from particles of the component organic material alone. The reflected signal depends on the base material, but also on the degree of flocculation and the size of the particle. Previous research found that as floc particles grow larger, they become less dense, so that very large floc has nearly the same density as the surrounding liquid. The authors suggest that the flocculation process itself alters the particle's reflection profile.

The authors' study explores how scatter off floc particles and details how sound can be used to study floc. They find that using conventional scattering assumptions were capable of only partially describing the observed scattering properties. They suggest that future models should better align with the observed scattering characteristics, therefore allowing acoustic observations to be used to routinely measure sediment properties in flocculating .

Explore further: Satellites catch the birth of two volcanic islands

More information: Acoustic scattering from a suspension of flocculated sediments Journal of Geophysical Research-Oceans, doi:10.1002/jgrc.20197, 2013 http://onlinelibrary.wiley.com/doi/10.1002/jgrc.20197/abstract

Related Stories

Antibiotic resistance flourishes in freshwater systems

Apr 25, 2012

The author Dr. Seuss may have been on to something when he imagined that microscopic communities could live and flourish on small specs of dust, barely visible to the naked eye. In fact, such vibrant communities exist – ...

Gases drawn into particles stay there

Apr 09, 2012

(Phys.org) -- Contrary to expectations, formation and growth of complex organic particles generated during oxidation of volatile organic molecules by ozone and nitrate follows a non-equilibrium path, according ...

Purifying sludge through oxygen-based digestion

Apr 29, 2013

An additive for oxygen-based processing of sludge may be useful in specific cases in lowering the environmental impact of waste water treatment for the meat and dairy industries.

Recommended for you

Satellites catch the birth of two volcanic islands

9 hours ago

The birth of a volcanic island is a potent and beautiful reminder of our dynamic planet's ability to make new land. Given the destruction we've seen following natural events like earthquakes and tsunamis in t ...

Uncovering diversity in an invisible ocean world

10 hours ago

Plankton are vital to life on Earth—they absorb carbon dioxide, generate nearly half of the oxygen we breathe, break down waste, and are a cornerstone of the marine food chain. Now, new research indicates ...

Evolution of the Antarctic ice sheet

12 hours ago

ULB study sheds a new light on the stability of the Antarctic ice sheet. It shows for the first time that ice rises (pinning points that keep the floating parts of ice sheets in place) are formed during the transition between ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.