Groundwater and soil contamination by LNAPL: State of the art and future challenges.

Contamination by Light Non-Aqueous Phase Liquids (LNAPL) represents a challenge due to the difficulties encountered in its underground assessment and recovery. The major risks arising from subsoil LNAPL accumulation face human health and environment, gaining a social relevance also in the frame of a continuously changing climate. This paper reports on a literature review about the underground contamination by LNAPL, with the aims of providing a categorization of the aspects involved in this topic, analyzing the current state of the art, underlying potential lacks and future perspectives. The review was focused on papers published in the 2012-2022 time-interval, in journals indexed in Scopus and WoS databases, by querying "LNAPL" within article title, abstract and/or key words. 245 papers were collected and classified according to three "key approaches" -namely laboratory activity, field based-data studies and mathematical simulations- and subordinate "key themes", so to allow summarizing and commenting the main aspects based on the application setting, content and scope. Results show that there is a wide experience on plume dynamics and evolution, detection and monitoring through direct and indirect surveys, oil recovery and natural attenuation processes. Few cues of innovations were found regarding both the use of new materials and/or specific field configuration for remediation, and the application of new techniques for plume detection. Some limitations were found in the common oversimplification of the polluted media in laboratory or mathematical models, where the contamination is set within homogeneous porous environments, and in the low number of studies focused on rock masses, where the discontinuous hydraulic behavior complicates the address and modeling of the issue. This paper represents a reference for a quick update on the addressed topic, along with a starting point to develop new ideas and cues for the advance in one of the greatest environmental banes of the current century.