CHARACTERISTICS, MAGNITUDES AND IMPACTS OF PETROLEUM WELL INTEGRITY ISSUES IN ALBERTA
Plant impacts associated with pipeline leaks mimic GM issues. Impacts are rarely due to CH4 asphyxia, but more commonly, leaks are indirectly due to CO2 induced stress or asphyxia due to vadose zone microbial oxidation of migrating gas. The effects of anthropogenic and natural CH4 seepage on vegetation and crops are indistinguishable. Where microbial oxidation of CH4 produces CO2, vegetation can also be impacted by groundwater chemistry changes and inorganic chemical reactions among CO2, groundwater, minerals and vegetation. There have been several attempts to determine correlations between GM CH4 flux and plant health impacts. While variable plant health and growth effects occur, including improvements in some species at low gas migration rates, detrimental impacts and even plant mortality occur at higher leakage rates. However, no quantitative recommendations related to gas migration rate exist because impacts are complicated by independent factors including, but not limited to, soil composition and characteristics, meteorological conditions, the microbial flora, and the plant species. There are several “sinks” where CH4 is oxidized, in the atmosphere, oceans and in the vadose zone of soils. The effectiveness and efficiency of the microbial soil sink plays an important role in the rates of microbial CH4 oxidation. The microbial soil CH4 sink can be affected adversely by agricultural and land use practices including the efficiency and vitality of vadose zone microbial CH4 oxidation.