POLYCYCLIC AROMATIC HYDROCARBON SEQUESTRATION BY SOIL ORGANIC MATTER FRACTIONS AND ITS EFFECT ON PLANT GROWTH

WAQAR-UN-NISA, . (2015) POLYCYCLIC AROMATIC HYDROCARBON SEQUESTRATION BY SOIL ORGANIC MATTER FRACTIONS AND ITS EFFECT ON PLANT GROWTH. Doctoral thesis, Agriculture University Rawalpindi Pakistan.

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Abstract

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental hazards in Pakistan. There are many ways in which the PAH can enter the soil environment and interfere with the soil system and the plants grown in soil. This study demonstrates the efficacy of organic amendments to improve phytoremediation efficiency in PAH contaminated soil. The main objectives of the study were to compare PAH concentration in soil before and after the pot experiments in different treatments and demonstrate the interaction of soil PAHs and compost amendments on PAH bioavailability in soil. To assess plant growth in PAH contaminated soil and their subsequent uptake of PAH by vetiver grass and rye grass and to evaluate the effect of season on the PAH sequestration in SOM fractions. Experiments were conducted with two different soils (S1: Gujar Khan with silty clay loam texture and S2: PMAS-Arid agriculture university Rawalpindi main campus with sandy loam texture) and grass (P1: vetiver; P2: rye grass) types. Each type of soil and grass was studied in six different levels of diesel contamination and compost amendment (T1: Control; T2: 1% compost; T3: 0.5% diesel (PAHs); T4: 1% diesel (PAHs); T5: 0.5% diesel (PAHs) + 1% compost and T6: 1% diesel (PAHs) + 1% compost) and performed with three replications. Pot trials were conducted in two seasons: during June - September (2012), and October - January (2013). Soil physic-chemical analysis and soil organic matter fractionation was performed at the start of experiments and also at the end of pot experiments. Soil PAHs analysis was done after the 15 days of spiking and at the end of experiments. PAHs were analyzed by GC-MS. Physico chemical analysis of the soil pH and EC values were lower than the initial values. 21 Similarly organic matter, TOC and TN concentrations varied significantly in each treatment. Plant growth revealed that PAH contamination negatively influenced both grass species. However adding compost improved the plant growth in PAH contaminated soils with 1% compost. In treatments with diesel and compost amendments the plant biomass was higher in summer compared to winter. A 56% decrease in root length was observed in vetiver grass when soil was spiked with 1% diesel. Uptake of low molecular weight PAHs was higher compared to high molecular weight PAHs. Accumulation of PAHs in root and shoot corresponded to the removal of PAHs from soil by grasses. The accumulation of PAHs in plant biomass was greater in summer than winter. The effect of various treatments applied showed that the more PAHs accumulated in the absence of compost. Whereas the sequestration by SOM in T5 and T6 reduced the concentration of PAHs in soil. In vetiver most of PAHs are accumulated in roots compared to shoots. GC-MS analysis for soil PAHs indicated that PAH concentration declined from the initial concentration. Microbial community analysis by TRFLP showed that Streptomyces and Mycobacterium were the dominating species in diesel contaminated soil. Soil fractionation showed that the humin fraction had higher percentage in both types of soils, while Fulvic acid concentration was lowest in all treatments. However, fulvic acid content was positively correlated to the PAHs in soil. In the case of high molecular weight PAHs, humic acid was positively correlated with the sequestration matrix. This study clearly showed that the phytoremediation of contaminated soil using organic amendments and plants with a dense root system could be a useful approach for removal of PAHs from contaminated soil. Compost amendment has increased the degradation of PAHs 22 through facilitated by microbial activity. Soil organic matter fractions were the prime sites where PAHs was mostly sequestered.

Item Type: Thesis (Doctoral)
Uncontrolled Keywords: POLYCYCLIC,AROMATIC ,HYDROCARBON SEQUESTRATION,ORGANIC
Subjects: S Agriculture > S Agriculture (General)
Depositing User: Mr Sami Uddin
Date Deposited: 17 Oct 2017 05:26
Last Modified: 17 Oct 2017 05:26
URI: http://eprints.hec.gov.pk/id/eprint/6584

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