Kıyı Akiferlerinde Petrol Hidrokarbon Kirliliğinin Doğal Gideriminin Araştırılması ve Modellenmesi Yöntemleri

Abstract

In this study research methods are assessed to determine the spatial distribution of petroleum hydrocarbon contamination in the coastal aquifers and to develop a groundwater flow and transport model that can be used to evaluate the level of natural attenuation that has occurred. The stages of this study include: 1) preliminary assessment and conceptual model including hydrogeologic characteristics of the site, the history of the site, and any past or current remedial activities, 2) field and laboratory investigations including soil and groundwater sampling techniques such as soil borings, multi-level monitoring well installation, aquifer tests and water quality sampling. Parameters to be measured, their measurement methods and use of these data should be explained in detail, 3) physical and geochemical characterization of the study area with the results of the field and laboratory investigations, 4) development of the groundwater model with selected software, 5) evaluation of monitored natural attenuation according to primary and secondary lines of evidence established during the investigation. The primary lines of evidence, which is a stable or shrinking plume rather than an expanding plume, will be the benzene, toluene, ethylbenzene and xylene (BTEX) contour maps prepared as a result of the groundwater sampling. Secondary lines of evidence, which include geochemical data that serve as indicators of naturally occurring biodegradation and estimates of natural attenuation rates, will be based on electron acceptor/reduction product concentrations measured within the BTEX plume. The results of the groundwater modeling are used to help decide whether the monitored natural attenuation process results in BTEX contaminant levels declining to acceptable levels within a specified time. If projections of contaminated levels indicate that natural attenuation is not enough for remediation, then additional remedial alternatives can be recommended for further investigation.

Biostimulation strategies : For in situ biodegradation of complex aromatic contaminant mixtures in groundwater

“…However, biodegradation in aquifers is often limited by either low concentrations of dissolved oxygen or a complete absence of oxygen leading to various types of anaerobic conditions. When oxygen is not available, the best electron acceptor for degradation process is nitrate (NO3 -), followed by manganese (Mn 4+ ), ferric iron (Fe 3+ ), sulfate (SO4 2-) and carbon dioxide (CO2) (Hatipoğlu-Bağci & Motz, 2019). Even though these alternatives to oxygen are often present in naturally anaerobic systems, aerobic biodegradation is often much faster than anaerobic contaminant transformation (Chakraborty & Coates, 2004;Varjani, 2017) and lead to complete removal of all the contaminants.…”

“…Biodegradation of BTEX compounds strongly depends on the terminal electron acceptor processes (Schreiber et al, 2004). The best electron acceptor for degradation process is oxygen (O2), followed by nitrate (NO3 -), manganese (Mn4 + ), ferric iron (Fe 3+ ), sulfate (SO4 2-) and carbon dioxide (CO2) (Hatipoğlu-Bağci & Motz, 2019). Even though BTEX compounds can be degraded under both aerobic and anaerobic conditions, anerobic biodegradation is much slower (Varjani, 2017).…”

“…The flow provided, can cause a concentration gradient in the liquid phase along the column length, leading to the formation of layers with differing concentrations unlike the well-mixed system observed in batch experiments. While this might appear disadvantageous, column experiments are more representative of the in situ environment, as the groundwater flow naturally introduces heterogeneity and intricate patterns in the subsurface, rendering predictions about chemical transport and fate challenging (Hatipoğlu-Bağci & Motz, 2019). Hence, in this thesis, column experiments allowed to simulate conditions closer to those present in Griftpark's subsurface.…”

“…For instance, compounds such as BTEX known to be less dense than water, can be dissolved from LNAPLs. NAPLs denser than water (including coal tar residues with HMW aromatics) are referred as DNAPL and tend to migrate downward and act as long-term sources of dissolved phase contaminants (Hatipoğlu-Bağci & Motz, 2019;Murphy et al, 2005) (Figure 1.2). PAHs are relatively lightweight and behave as LNAPLs, however some HMW PAHs that are denser can act like DNAPLs and sink below the water table to form a separate phase.…”

“…Microorganisms have the capability to biodegrade almost all organic contaminants in order to use them for their own growth and reproduction. Contaminants serve as a source of carbon, essential for the formation of new cell constituents, and also provide electrons, which are necessary for obtaining energy (Hatipoğlu-Bağci & Motz, 2019). Briefly, microbes gain energy from contaminants by breaking chemical bonds and transferring the electrons from the contaminants to an electron acceptor.…”