IntroductionThe worldwide demand for petroleum and their refined products has grown significantly during the last decades. Unfortunately, more oil spills into the aquatic ecosystem as a consequence of the increasing demand of marine transportation of the crude oils from the remote locations of the crude oil production sites (many in the Middle East countries). Because of toxic components (such as polycyclic aromatic hydrocarbons, PAHs) in the petroleum and their refined products, oil spills could be devastating to the aquatic environment, especially to the fragile shorelines. Fast and effective response measures to clean spilled oil should be taken once an oil spill accident occurs. Traditional cleanup methods (such as application of skimmers) are often confined to a large extent by weather conditions and are not able to clean the spilled oil effectively, thus they are more suitable just as the first recovery of oil spills. The usage of chemical dispersant itself may cause secondary pollution, and it may also accelerate the filtration of oil into the deeper beach aquifer, therefore there may be a risk of causing more persistent and toxic pollution. In facing these facts, the oil spill response community is seeking an economical and environmental friendly technology for spilled oil cleanup. Actually it was early in the 1970s that scientists had observed flocculation of clay and oil in saltwater, and stabilization of oil-in-water emulsion by solid particles.1–4The significance of this process in natural cleansing of oiled shorelines was ignored for decades until the Exxon Valdez oil spill in 1989. A large portion of the oiled shorelines cleaned themselves naturally even in the sheltered coast by the production of a fluffy colloidal emulsion composed of oil droplets surrounded by micron-sized clays. This kind of emulsion did not adhere strongly to the sediment, thus largely increased oil dispersion into the water body; oil biodegradation was highly accelerated due to the increase of the oil–water contact area. This natural process has been demonstrated in other oil spill accidents and laboratory studies to have the ability to enhance cleaning of oiled shorelines greatly. In addition to the natural attenuation of spilled oil, other shoreline cleanup techniques, such as sediment relocation and sediment mixing can greatly accelerate this process.5–17Various terminologies have been used to refer to this process, such as mineral-stabilized droplet, clay–oil flocculation,5,7,10oil and fine-particle interaction,9more frequently oil–mineral aggregation (OMA)12and oil-suspended particulate matter (SPM) aggregation (OSA).18,19However, as the aggregation between oil droplets and non-mineral particles are widely observed, the term of oil-suspended particulate matter aggregates (OSAs) was introduced and used in this study.The significance of OSA formation in shoreline cleanup has motivated many studies on characteristics of OSAs under different conditions, especially studies on quantitative effects of SPM size and concentration, the oil type, and the water salinity on the OSA formation. This article aims to provide a brief review on OSA formation and its role in oiled shoreline cleansing. The effects of different controlling factors, such as oil and sediment type and concentration, salinity, temperature and mixing energy on OSA formation are discussed. Methods used for the OSA characterization studies are summarised. Related topics which are under investigation and research needs in the future to further improve our quantitative understanding of this natural process are also outlined.