ANALYSIS OF OXYGENATED POLYCYCLIC AROMATIC HYDROCARBONS AND THEIR PARENT MOLECULES IN BIOCHAR AND ITS LEACHATES

Due to the increasing use of biochar as a soil amendment , the amount and composition of contaminants in biochar should be analyzed. Two of those suites of compounds in biochar are polycyclic aromatic hydrocarbons (PAHs) and oxygenated PAHs (OPAHs). There are many hazards of PAHs and OPAHs including that they are toxic and carcinogenic. The higher polarity of OPAHs versus PAHs allows these compounds to be leached into aquatic environments. The aim of this research was to optimize methods for isolating and analyzing OPAHs in biochar solids and their aqueous leachates and to apply this method to solid biochar and its leachates. The optimal methodology for extracting PAHs and OPAHS from solid biochar involved using pressurized liquid extraction with a dichloromethane:acetone solvent cocktail in a 1:1 ratio , and a 5% deactivated silica column incorporating dicholoromethane:ethyl acetate (95:5; [nu]:[nu]) for purification. The average spiked recovery (n=3) and standard deviation for the optimal pressurized liquid extraction and column purification were 26.07 ± 3.99% and 115.03 ± 4.43 % respectively. For aqueous leachates , a liquid-liquid extraction utilizing dichloromethane yielded optimal results of 102.56 ± 13.13% recovery. All extracts were analyzed using gas chromatography coupled to mass spectrometry (GC-MS). The optimized method was used to analyze a variety of solid biochars and their leachates to identify and quantify PAHs and OPAHs. In the oak biochar series , total compound concentrations increase with increasing formation temperature until 400°C. After , 400°C the concentration of total compounds begins to decrease. In the grass biochar series concentrations of total compounds increases as formation temperature increases until 650°C , where the concentration reached a maximum. In addition to total compound concentrations in the biochar series , composition of PAHs and OPAHs in biochar is also affected by formation temperature. At low biochar formation temperatures , <400°C , there is a greater abundance of low molecular weight compounds in the solid samples. There was no significant increase in high molecular weight compounds in either temperature series. The concentration of total compounds in grass and oak biochars varied with respect to feedstock. The grass biochar series had a much lower concentration of total compounds when compared to the oak series. The leachates of the biochar samples also showed trends with respect to PAHs and OPAHs. A noticeable trend in all the leachates is that the concentration of PAHS and OPAH decreased with increasing biochar pyrolysis temperature for both temperature series. The quantification of PAHs and OPAH in solid biochar and its leachates helps to improve the understanding of the fate of these compounds in the environment