Influence of soil organic matter removal on the sorption/desorption behavior of imidacloprid

Tlo je površinski sloj Zemljine kore koji ima brojne uloge. Jedna od najvažnijih je osiguravanje hrane za ljude i životinje. S obzirom na rastuću populaciju na Zemlji, raste i potreba za hranom. Samim time poljoprivrednici se trude u kraćem vremenu, proizvesti više hrane, te posežu za kemijskim supstancama zvanim pesticidi. Cilj ovog istraživanja bio je istražiti utjecaj organske tvari tla na sorpcijsko/desorpcijske procese imidakloprida. Analizirana su četiri tla s područja Hrvatske, ispitane su njihove fizikalnokemijske karakteristike te udio humusa i njegov sastav, potom je tlima uklonjena organska tvar te su na njima provedeni sorpcijsko/desorpcijski procesi imidakloprida. Ravnotežna koncentracija imidakloprida određena je HPLC analitičkom tehnikom. Za prikaz ravnotežnih procesa sorpcije/desorpcije korišteni su Freundlichov i Langmuirov model izotermi. Freundlichov model pokazao se bolji za opisivanje sorpcijsko/desorpcijskih procesa imidakloprida u odnosu na Langmuirov model, te su dobiveni parametri Freundlichovim modelom korišteni za utvrđivanje utjecaja karakteristika tla na sorpcijsko/desorpcijsko ponašanje imidakloprida u tlu. Dobivene su izoterme L oblika. Kod tala s uklonjenom organskom tvari vrijednosti kapaciteta sorpcije/desorpcije su niži u odnosu na netretirana tla. Srednja vrijednost faktora KOC za netretirano tlo iznosi 193,22 kg/L, a za tretirano 370,80 kg/L što imidakloprid svrstava u kategoriju srednje pokretnih mikrozagađivala. Utvrđena je pozitivna ovisnost između organskog ugljika, udjela gline, kapaciteta izmjene kationa na koeficijent sorpcije (KF) odnosno desorpcije (KFd) kod netretiranih tala, dok je ta ovisnost manja kod tretiranih tala. Višestrukom linearnom regresijom utvrđeno je da je parametar ,,organski ugljik“ dominantan u sorpcijsko/desorpcijskim procesima imidakloprida u tlu, što dovodi do zaključka da organska tvar znatno utječe na procese sorpcije i desorpcije mikrozagađivala.Soil represents the surface layer of the Earth's crust, and it has many roles. One of the most important roles is providing food for humans and animals. With the expansion of the world's population, the need for food also grows. As a results, farmers are trying to produce more food in a shorter time using chemicals called pesticides. The aim of this research was to investigate the influence of organic matter content on the sorption/desorption processes of imidacloprid. For that purpose four soils with different physicochemical properties from coastal regions of Croatia were used. Furthermore, the sorption/desorption processes of imidacloprid in soils with reduced organic matter content were also investigated. The equilibrium concentration of imidacloprid was determined by HPLC analytical technique. To describe the imidacloprid equilibrium sorption/desorption processes, the Freundlich and Langmuir isotherm models were used. The Freundlich model proved to be better for description of the imidacloprid sorption/desorption processes compared to the Langmuir model, so the parameters obtained with the Freundlich model were used to determine the influence of soil characteristics on the sorption/desorption behaviour of imidacloprid. In all analysed soils imidacloprid isotherms were of L-shape. In soils with reduced organic matter, the values of sorption/desorption capacity were lower compared to untreated soils. The mean values of the KOC factor for untreated and treated soils were 193.22 and 370.80 kg/L, classifying imidacloprid in the category of medium mobile micro pollutants. Results of the research indicate a positive dependence between organic carbon, clay content, cation exchange capacity and the sorption (KF) and desorption (KFd) coefficients found in untreated soils, while this dependence was lower in treated soils. Multiple linear regression showed that organic matter content was the predominant soil characteristic influencing the sorption/desorption processes of imidacloprid in the soil, leading to the conclusion that organic matter significantly affects the processes of sorption and desorption of imidacloprid in analyzed soils