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Chiara Esposito: Bioavailability of phosphorus bound to different engineered materials

Seminar: Aquatic Biology

2019.09.18 | Anne Kirstine Mehlsen

Date Thu 26 Sep
Time 09:45 10:30
Location Department of Bioscience, Ole Worms Alle 1, building 1135-234

Speaker: Chiara Esposito, Università di Firenze, Italy / Aquatic Biology, AU

ABSTRACT: 

 

Phosphorus (P) is an essential element for the growth of plants and it makes up about 0.2 % dry weight of a plant, where it is essential in many macromolecules, such as nucleic acids, phospholipids and ATP.  Today, P is mostly obtained from mined rock phosphate and is often combined in mineral fertilizers, but P is a non-renewable resource, so there is a limited amount of P to be obtained this way. Although the total amount of P in the soil may be high, it is often present in unsuitable forms for plants or in forms that are only available outside of the rhizosphere. Up to now, sustained P-removal has proven elusive regardless of the wastewater treatment system, often resulting in outlet waters containing P-concentrations higher than permitted. Hence, water with P is often one of the by-products of wastewater treatment. For this reason, the aim of this project is to understand if we can reuse P that has been recovered from wastewater by material sorption, as a P source for plants, creating a more closed nutrient cycle.

In order to test the bioavailability, we saturated two different substrates with different particle size with a solution of P (KHPO), representing the filter media from wastewater treatments. Compared to their sorption capacity, which was calculated by previous experiments, we reached 7,6 mg P/g of material for the first substrate and 12,0 for the second one.  At this point we made 6 different treatments with different concentrations of P from 0 up to 100 g P/m² and an extra treatment with commercial fertilizer for plants containing P, N and K. The different amounts of our P medium was then mixed in 3 L pots with sphagnum and sand together with the other macronutrients (N and K), keeping the normal ratio between these elements. In this way, we just focused our attention on the lack or on the differences of P in the soil. We have 5 replicates per treatment, so now 60  Zea mays plants are growing in a growth chamber with controlled parameters of light, humidity and temperature.

Department of Bioscience, Public / media, Staff