The release of polycyclic aromatic hydrocarbons (PAHs) by human energy exploitation and excessive environmental use has caused substantial environmental contamination. These compounds bioaccumulate in aquatic environments and translocate through the food chain, posing risks to health and environmental safety. To better understand the risks of PAHs in surface water and food chains, this review summarizes their distribution, concentration levels, sources, and toxicity in various surface water environments. It also examines how PAH bioaccumulation affects aquatic organisms and human health. Globally, PAHs have been detected in both aquatic environments and organisms with an increasing trend. Human activity is the main cause of PAH contamination. The results revealed a distinct geographical distribution of PAH risk influenced by population density, industrial development, climate, and seasonal variations. PAHs are found in remote areas, indicating their medium- and long-range transport by atmospheric dispersion. PAHs bioaccumulate in aquatic organisms and cause direct and indirect toxic effects via biomagnification. PAH bioaccumulation is directly correlated with aquatic pollution. This study also emphasizes the carcinogenicity of compounds such as benzo[a]pyrene, identifying occupational and environmental exposure frequencies as key risk factors. This study enhances our understanding of the dynamics of multiple PAHs in aquatic ecosystems and their health effects, thereby contributing to environmental sustainability.

Microplastics (MPs) in subsurface environments are migratory and can carry heavy metals, increasing the extent of MP and heavy metal pollution. This study used quartz sand-filled column experiments to investigate the adsorption and cotransport behaviours of PS-MPs, O₃, UV-aged PS-MPs, and Cu²⁺ at different MP concentrations, ionic strengths, and ionic valences in a saturated porous medium. The results showed that when MPs migrate alone in the absence of an ionic background, higher concentrations have increased mobility. In contrast, an increase in the background ion concentration or ion valence inhibits the individual transport capacity of PS-MPs. An increase in the concentration of background ions or elevation in the valence state promotes Cu²⁺ transport because of the action of the double electric layer on the surface of the colloid and the electrostatic repulsive forces combined with the background ions. The adsorption capacity of aged PS-MPs was stronger than that of PS-MPs because of the binding of the aged PS-MPs to Cu²⁺ through complexation and electrostatic attraction. In the binary system of PS-MPs/Cu²⁺, PS-MPs promoted Cu²⁺ transport and the mobility of Cu²⁺ loaded by PS-MPs decreased with increasing background ion concentration. The cotransport results showed that MPs promote Cu²⁺ transport in the following order: O₃-aged Ps > UV-aged Ps > Ps, as the increasing cation concentration in the MPs and Cu²⁺ occupies the PS surface adsorption sites. Overall, PS is an effective carrier for Cu²⁺. These findings offer fresh exploration concepts for the joint migration of MPs and heavy metals in underground settings.

SiO₂ and polystyrene (PS) are carriers of microorganisms and metals in porous media, which can produce changes in groundwater quality and cause issues related to clogging of the porous medium. Although SiO₂ and PS particle transport in porous media has been previously studied, what influences transport at various particle sizes and flow rates remains unclear. Here, we looked at how pH and ionic strength affected the surface zeta potentials as well as how particle size and flow rate affected the transport of suspended SiO₂/PS particles in a porous media. The results indicate that increasing pH and decreasing ionic strength increased the negative surface charges on both the SiO₂ and PS particles, thereby yielding greater electrostatic repulsion between particles. At the same flow rate, the retention rate of 10 μm PS particles in the porous medium was 46.1% better than that of 2 μm particles, whereas the retention rate of 10 μm SiO₂ particles was 7.88% better than that of 2 μm particles. For the same particle size, increasing the flow rate decreased SiO₂ and PS retention in the porous medium. Thus, particle size and flow rate substantially impact the transport of SiO₂ and PS-suspended particles in a porous media.

Artificial groundwater recharge with reclaimed water (secondary effluent from wastewater treatment plants) has become an important approach to solving water scarcity worldwide. Microorganisms in activated sludge can secrete many extracellular polymeric substances (EPS). However, information on the impact of EPS on the movement of heavy metals in porous media and their environmental effects on underground networks is limited. To assess this risk, we extracted EPS from the aerobic section of a wastewater treatment plant using hot sodium hydroxide and conducted experiments using one-dimensional sand columns to investigate how ion composition and strength affect the movement and interaction of cadmium (Cd) and EPS in porous media. The results showed that EPS facilitated Cd migration in porous media. Sodium (Na) and calcium (Ca) ions promoted the migration of Cd in porous media and EPS–Cd complexation. The effect of Ca was more significant than that of Na. As the Na adsorption ratio increased, the migration ability of Cd in porous media and the complexation ability of EPS with Cd decreased. Therefore, when estimating the migration of EPS and Cd in subsurface environments, careful consideration should be given to prevent the risk of groundwater pollution.