Biochar as an Effective Material on Sediment Remediation for Polycyclic Aromatic Hydrocarbons Contamination

Abstract

The high-speed urbanization and associated human activities have led to dramatic alternations on urban river ecosystems [1, 2], which consequently degrades surface water quality [3]. As a pollutant sink in the river ecosystem, sediment can accumulate various polycyclic aromatic hydrocarbons (PAHs), which derive from ship traffic petrol leaking and urban wastewater runoff [4]. PAHs are difficult to degrade under anaerobic conditions in the environments [5] and remain risks to ecosystems as well as human health [6]. Therefore, the removal of PAHs in sediment is a key technique in urban river remediation. Several approaches were developed to remediate the PAHs contaminated sediments, including dredge, bioaugmentation, biostimulation and capping with clean material [7]. Among these methods, capping with viable substances were widely used as low cost approaches for the natural recovery of sediments [8]. For the capping treatments, selection of cap-material is the critical part of this technology. These materials, such as clean sand, zeolite, and activated carbon [9], are all expected to have high adsorption capacities and be able to block the diffusion of organic pollutants from sediments. However, the utilization of these materials would consume natural resources (such as sand and zeolite) and require excessive energy in put (activated carbon). Development of a more environmental friendly materials is of great concern on capping treatment for PAHs degradation. Biochar is unknown as an environmental friendly material, since it involve in carbon sequestration pathway and it always be produced from various agriculture wastes such as straws, branches, and nut shells [10]. The characteristics of biochar depend on its raw matrix and pyrolysis conditions. Biochar that derived from natural plants are usually porous and hydrophobic, which have high adsorption capacity for organic components [11]. Therefore, biochar has the potential capability to be used as a capping material for PAHs treatments. This study aims to investigate the mechanism of biochar as capping materials for PAHs removal in urban river sediments.