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 đubreno različitim količinama fosfornog đubriva monoamonijum-fosfata (MAP). Količine primenjenog mineralnog đubriva bile su 26, 39 i 52 kg po hektaru. Kao kontrolni uzorak korišćeno je neđubreno zemljište. Radi boljeg razumevanja tokova fosfora kroz zemljište 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 tretirani različitim sekvencijalnim ekstrakcionim procedurama i to: modifikovanom Chang i Jackson metodom, modifikovanom Tesijerovom metodom i BCR metodom. Ehstrahovani su različiti oblici fosfora i metala. Takođe su, u cilju određivanja ukupnog sadržaja mikroelemenata, uzorci potpuno razarani mikrotalasnom digestijom. Istim metodama sekvencijalne ekstrakcije i totalne digestije tretirani su i sertifikovani referentni materijali CRM 684 (ekstratibilni fosfor rečnog sedimenta) i CRM 701 (ekstraktibilni elementi jezerskog sedimenta) u cilju potvrđivanja tačnosti instrumenta i primenjenih 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 na stabljiku i zrno i potpuno razarani mikrotalasnom digestijom. Koncentracije fosfora i metala u uzorcima zemlje i pšenice određivane su optičko emisionom spektrometrijom sa indukovano spregnutom plazmom (ICP-OES). Za bolje razumevanje i proučavanje prirode asocijacija tragova elemenata i fosfora korišćena je korelaciona analiza. Dalje, detaljno su ispitane promene u frakcijama organskog i neorganskog fosfora u zemljištu prouzrokovane višegodišnjom primenom različitih količina fosfornog đubriva. Poređeni su rezultati sekvencijalnih metoda fosfora sa sekvencijalnim ekstrakcijama metala kako bi se proniklo u asocijacije fosfornih vrsta sa substratima. Rezultati ukazuju da se kontinualnim đubrenjem povećavaju svi oblici fosfora u zemljištu osim fosfora vezanog za kalcijum i organski fosfor. Primena većih količina fosfornog đubriva rezultira u dominaciji Al-P frakcije proučavanog zemljišta što ukazuje 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, 39 and 52 kg P ha-1 amounts during a period of 40 years. Samples were subjected to sequential extraction according to a modified Chang and Jackson method, modified Tessier method, and the Community Bureau of Reference (BCR) sequential extraction procedure in order to extract different forms of phosphorus and metals, also Microwave Total digestion was applied to extract different forms of phosphorus and metals. The certified reference material CRM 684 (river sediment extractable phosphorus) and CRM 701 (Lake Sediment extractable Trace Elements) was used to confirm the accuracy of the instrument and of both employed methods. Also the distribution of metals (Al, Cd, Co, Cr, Cu, Fe, Mn, Ni and Pb) in wheat samples (Triticumaestivum) resulting from long-term fertilization (40 years) were investigated. All wheat samples were subjected to microwave digestion system, in order to extract metals and to determine them. In the experimental plots wheat was harvested, grains were separated from stalk and then the total content of elements was determined. The Concentrations of phosphorus and metals in soil and wheat samples were determined by ICP-OES. Correlation analysis was carried out in order to provide better understanding of the nature of associations of trace elements with phosphorus. The changes in inorganic and organic phosphorus (P) fractions of soil resulting from long-term fertilization (40 years) were investigated. In order to improve understanding of the sink and sources of phosphorus, P-fractions were extracted from soil samples from 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 comparison of the results of sequential methods of phosphorus species with the sequential extraction of metals (modified Tessier method). The results of continuous fertilization during 40 years indicated increases of all forms phosphorus in the soil except of phosphorus bound to calcium and organic phosphorus. Application of higher amounts of P-fertilizer resulted in the dominance of the Al–P fraction in the studied soil, which indicated that this fraction was the most responsible for the migration of phosphorus along the soil profile. Also the Bioaccumulation factor (BAF) of heavy metals in the Grain and Wheat were determined. Ten metals (Al, Cd, Co, Cr, Cu, Fe, Mn, Ni and Pb) were studied.