Original Articles
Devaanshi Jagwani and Jeetendr
Abstract
In the past few decades there has been increasing concern about the exposure and impacts of chemicals on humans and environmental organisms in the society. Water-based drilling fluids (WBMs) are the most common in exploratory and development drilling; they contain additives that can be extremely toxic, even in low concentrations. The discharge of drilling wastes poses the greatest risk of bioaccumulation and toxicity to the marine organisms such as fish of ecological and commercial value (which are subsequently consumed by the humans). Hence, the purpose of the present investigation was to evaluate the toxicological impacts in environment due to offshore drilling activities. The present study deals with determination of PAH concentrations in composite samples of WBM, and drill cuttings, which were obtained from three different wells in the Kaveri-Godavari (KG) Basin, East coast of India and the ecological toxicity prediction of these chemicals to the aquatic community. In both WBMs and drill cuttings, concentration of naphthalene was in highest concentration, while benzo (a) pyrene was lowest. The WBMs contained significantly (P<0.05) higher PAH concentration than drill cuttings. The individual PAH concentration significantly (P<0.01) increased with increasing depth in each well. ECOSAR “estimation methods” can be used to fill data gaps where little or no experimental measured data exists. The toxicity of the PAHs (EC50/LC50) to fish, green algae, daphnid and mysid estimated can be used to predict toxicity to a general aquatic community. Monitoring of any chemical inputs from offshore exploration and oil & gas development in the offshore regions is important to be able to distinguish the ²Environmental Baseline² from potential future impacts.