Maths to improve orchard safety

Wednesday, April 22, 2009

Maths model of droplet drift to improve orchard safety

Mathematics doctoral graduate Sharleen Harper had no idea when she enrolled as an undergraduate that the intricate equations she loved to devise could be used to solve environmental problems.

Her award-winning thesis featuring a mathematical model of chemical spray dispersal in orchards could help horticultural growers reduce the drift of harmful droplets.

Ms Harper, who graduated in Auckland on Tuesday, developed the model using an advection-dispersion equation to predict the transport of spray droplets – containing chemicals such as hydrogen cyanamide used by kiwifruit growers – that are carried by the wind and dispersed by turbulence downwind of orchard shelterbelts.

“The orcharding industry is placing a lot of effort into addressing spray drift concerns, and shelterbelts can be very effective tools,” says the student at Massey’s Institute of Information and Mathematical Sciences at Albany. “Sprays containing chemicals may be hazardous to human or animal health in the surrounding environment.”

However, there is little information available on how to predict drift deposits downwind of the targeted area, particularly in the case of a fully sheltered orchard block, which is the focus of her research.

Her study was prompted after Massey hosted the 2005 meeting of the Mathematics-in-Industry Study Group, which representatives from Plant Protection Chemistry New Zealand and Lincoln Ventures Ltd attended for help in seeking a solution to the problem of orchard spray drift. Lincoln Ventures Ltd provided additional financial support for Ms Harper’s study, which allowed her to present her work at several conferences.

Titled Mathematical Models for Dispersal of Aerosol Droplets in an Agricultural Setting, her thesis won the Cherry Prize for the best graduate student paper at the annual Australia and New Zealand Industrial and Applied Mathematics Conference in 2007, making her the second New Zealander to win the prize in its 40-year history. It is also the first thesis to be listed on the Massey University Dean’s List of Exceptional Doctoral Theses established this year.

She was selected, by the Royal Society of New Zealand to join a team attending the Joint International Symposium in China later this month for a workshop on mathematical models and climate change and will do so with funding from the Ministry of Research, Science and Technology.

The 28-year-old former Orewa College pupil hopes her research will become available to horticulturists to better manage spraying.

Following her doctoral studies, Ms Harper has been working for the National Institute of Water and Atmospheric Research since last May. Among other environmental research projects, she develops mathematical models to predict contaminant removal from city storm water, and says both her thesis and current work at the institute combine her strengths in maths and physics.

“When I say I’m a mathematician, people ask me ‘what do you do?’; I explain to them about the modelling aspect and how it can be applied to so many problems, especially environmental issues.”

She is one of 20 PhDs, and among 1092 students to graduate from Massey University Albany at this week’s ceremonies at the Bruce Mason Centre, Takapuna.

ENDS

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