Polycyclic Aromatic Hydrocarbons (PAHs) and their Derivatives (O-PAHs, N-PAHs, OH-PAHs): Determination in Suspended Particulate Matter (SPM) – a Review

The aim of this paper is the presentation of the current state-of-the-art about the determination of polycyclic aromatic hydrocarbons (PAHs) and their oxidized forms originating from Suspended Particulate Matter (SPM) samples. The influence of SPM on health is twofold. SPM, as composed of small particles, is dangerous for the respiratory system. Additionally, SPM is a carrier of many hazardous compounds, particularly PAHs. Recently, several researches focus on the derivatives of PAHs, particularly nitro-, oxy- and hydroxy-PAHs, which are more dangerous than the parent PAHs. Both gas and high-performance liquid chromatography with various detection techniques are used to analyze both PAHs and their oxidized forms. Due to the appearance of these compounds in the environment, at a very low level, an analyte concentration step has to be applied prior to analysis. If GC and HPLC techniques are chiefly used as analytical tools for these analyses, the spectrum of analyte concentration procedures is very broad. Many analyte concentration techniques are proposed: from classic liquid-solid extractions, including Soxhlet technique, pressurized liquid extraction (ASE) or microwave oven (MWE) and sonic supported extraction to SPE techniques applications. However, one should remember that PAH determination methods are tools for solving the main problem, i.e., the evaluation the health hazard connected to the presence of SPM in air. Thus, the main drawback of several papers found in this review, i.e., the lack of information concerning limit of detection (LOD) of these methods makes their applicability very limited.

Nutrient Dynamics at the Sediment-Water Interface: Influence of Wastewater Effluents

Uptake and regeneration fluxes and concentrations of nutrients, i.e., nitrate (NO3−), ammonium (NH4+), phosphate (PO43−) and dissolved organic carbon (DOC), were evaluated upstream and downstream of a wastewater treatment plant (WWTP) in the River Wandle, UK, from July to October 2019. Using chamber techniques, water-specific nutrient concentrations were measured at two exposures (3 and 10 min) to calculate fluxes. The WWTP effluent contributed to elevated concentrations and modified flux rates, resulting in significant differences at the study sites. Compared with summer, the concentrations of NO3− and DOC increased while NH4+ and PO43− decreased in autumn. Nutrient fluxes varied both temporally and spatially in uptake (i.e., storage in sediments) or regeneration (i.e., release into river water). Under the actions of physical and biological processes, the fluxes of NO3− and NH4+ showed opposite flux directions. Dissolved oxygen (DO) and bioabsorption mainly affected PO43− and DOC fluxes, respectively. Specifically, across all sites, NO3− was −0.01 to +0.02 mg/(m2 s), NH4+ was −29 to +2 μg/(m2 s), PO43− was −2.0 to +0.5 μg/(m2 s), and DOC was −0.01 to +0.05 mg/(m2 s). Further, we did find that these variations were related to nutrient concentrations in the overlying water. Our results provide further evidence to show that reductions in river nutrients are paramount for improving river ecological conditions. Additionally, we suggest that more research is needed to evaluate chamber-based experimental approaches to make them more comparable to in-situ flux methods. Highlights • Sewage effluent resulted in elevated nutrient concentrations and modified fluxes. • Flux was affected by initial nutrient concentrations, DO and microbial activity. • Inexpensive approaches to study nutrient dynamics are needed for river restoration.