Toxic microelements : bioavailability and mobilization in soil after 40 years of phosphorous fertilization

Abstract

U ovoj doktorskoj disertaciji proučavano je zemljište koje je 40 godina đubrenorazličitim količinama fosfornog đubriva monoamonijum-fosfata (MAP). Količineprimenjenog mineralnog đubriva bile su 26, 39 i 52 kg po hektaru. Kao kontrolni uzorakkorišćeno je neđubreno zemljište. Radi boljeg razumevanja tokova fosfora krozzemljište i potencijalnih izvora fosfora uzorkovano je zemljište sa dve dubine:površinski sloj debljine do 30 cm i sloj od 30 do 60 cm. Uzorci zemljišta su tretiranirazličitim sekvencijalnim ekstrakcionim procedurama i to: modifikovanom Chang iJackson metodom, modifikovanom Tesijerovom metodom i BCR metodom.Ehstrahovani su različiti oblici fosfora i metala. Takođe su, u cilju određivanja ukupnogsadržaja mikroelemenata, uzorci potpuno razarani mikrotalasnom digestijom. Istimmetodama sekvencijalne ekstrakcije i totalne digestije tretirani su i sertifikovanireferentni materijali CRM 684 (ekstratibilni fosfor rečnog sedimenta) i CRM 701(ekstraktibilni elementi jezerskog sedimenta) u cilju potvrđivanja tačnosti instrumenta iprimenjenih metoda.Takođe je u ovom radu određivan sadržaj sledećih elemenata: Al, Cd, Co, Cr, Cu, Fe,Mn, Ni i Pb u uzorcima pšenice gajene na tom zemljištu. Uzorci pšenice su odvajani nastabljiku i zrno i potpuno razarani mikrotalasnom digestijom.Koncentracije fosfora i metala u uzorcima zemlje i pšenice određivane su optičkoemisionom spektrometrijom sa indukovano spregnutom plazmom (ICP-OES). Za boljerazumevanje i proučavanje prirode asocijacija tragova elemenata i fosfora korišćena jekorelaciona analiza. Dalje, detaljno su ispitane promene u frakcijama organskog ineorganskog fosfora u zemljištu prouzrokovane višegodišnjom primenom različitihkoličina fosfornog đubriva. Poređeni su rezultati sekvencijalnih metoda fosfora sasekvencijalnim ekstrakcijama metala kako bi se proniklo u asocijacije fosfornih vrsta sasubstratima.Rezultati ukazuju da se kontinualnim đubrenjem povećavaju svi oblici fosfora uzemljištu osim fosfora vezanog za kalcijum i organski fosfor. Primena većih količinafosfornog đubriva rezultira u dominaciji Al-P frakcije proučavanog zemljišta štoukazuje na to da je ta frakcija najodgovornija za migraciju fosfora kroz zemljišni profil.Izračunati su i bioakumulacioni faktori za sledeće elemente Al, Cd, Co, Cr, Cu, Fe, Mn,Ni i Pb za zrno i stabljiku pšenice.

The studied soil was of the Stagnosol type. Phosphate fertilizer was applied in 26, 39and 52 kg P ha-1 amounts during a period of 40 years. Samples were subjected tosequential extraction according to a modified Chang and Jackson method, modifiedTessier method, and the Community Bureau of Reference (BCR) sequential extractionprocedure in order to extract different forms of phosphorus and metals, also MicrowaveTotal digestion was applied to extract different forms of phosphorus and metals. Thecertified reference material CRM 684 (river sediment extractable phosphorus) and CRM701 (Lake Sediment extractable Trace Elements) was used to confirm the accuracy ofthe instrument and of both employed methods.Also the distribution of metals (Al, Cd, Co, Cr, Cu, Fe, Mn, Ni and Pb) in wheatsamples (Triticumaestivum) resulting from long-term fertilization (40 years) wereinvestigated. All wheat samples were subjected to microwave digestion system, in orderto extract metals and to determine them.In the experimental plots wheat was harvested, grains were separated from stalk andthen the total content of elements was determined.The Concentrations of phosphorus and metals in soil and wheat samples weredetermined by ICP-OES. Correlation analysis was carried out in order to provide betterunderstanding of the nature of associations of trace elements with phosphorus.The changes in inorganic and organic phosphorus (P) fractions of soil resulting fromlong-term fertilization (40 years) were investigated. In order to improve understandingof the sink and sources of phosphorus, P-fractions were extracted from soil samplesfrom depths of 0–30 and 30–60 cm with different amounts of monoammoniumphosphate(MAP) and then determined.Furthermore, the association of phosphorus with substrates was provided by comparisonof the results of sequential methods of phosphorus species with the sequential extractionof metals (modified Tessier method). The results of continuous fertilization during 40years indicated increases of all forms phosphorus in the soil except of phosphorusbound to calcium and organic phosphorus. Application of higher amounts of P-fertilizerresulted in the dominance of the Al–P fraction in the studied soil, which indicated thatthis fraction was the most responsible for the migration of phosphorus along the soilprofile.Also the Bioaccumulation factor (BAF) of heavy metals in the Grain and Wheat weredetermined. Ten metals (Al, Cd, Co, Cr, Cu, Fe, Mn, Ni and Pb) were studied.