Determination of the long-term chemical impact of human-related activities on the Red Sea coastal marine environment utilizing complementary mass spectrometric techniques and novel chemometric tools

Comprehensive environmental monitoring of chemical pollution is the initiative towards providing information regarding the quality of marine ecosystems. Compounds such as pharmaceuticals, industrial chemicals, PFAS, PAHs PCBs, and plant protection products often end up in environmental substrates following a number of different pathways. Upon reaching the sea, biotic and abiotic processes may take place, producing metabolites and transformation products, which often pose an even greater threat to the marine environment than their parent compounds. This leads to further degradation of aquatic ecosystems and inevitably affects human health. 

The marine environment of the Red Sea is a cornerstone in the development of the Arabic Peninsula, contributing to its constant economic growth. Continuous urbanization and industrialization on its coasts lead to unavoidable chemical encumbrance. To address this matter, the Kingdom of Saudi Arabia has launched the Marine and Coastal Environment Protection Initiative to evaluate the current state of the coastal Red Sea area. Existing lagoons act as large banks of sedimentation, where precipitation takes place, potentially burdening sediments and benthic seawaters with lipophilic organic micropollutants, volatile organic compounds and heavy metals. This process occurs likely due to sorption mechanisms onto microplastics, as previously reported in the literature, followed by precipitation, which is enhanced by said contaminants’ non-affinity with the aqueous seawater compartment. Besides sea bottom degradation, polluted sediments become potential sources of seawater recontamination, increasing the number of emerging contaminants (ECs) to which marine organisms are exposed to. 

Aiming to determine a wide variety of existing emerging contaminants in surface sediments collected from 52 stations along the Red Sea coastal zone, generic sample preparation workflows and complementary analytical techniques were applied. ECs of various physicochemical properties were determined by utilizing GC-LRMS (volatile organic substances) and LC-HRMS (wide-scope target screening) techniques. An in-house developed dataset of more than 2,400 analytes was applied for said determinations. 

Preliminary results indicate that the Red Sea lagoons are chemically encumbered by different groups of pollutants, based on different point sources existing in the vicinity. Pharmaceutically active compounds as well as a wide variety of pollutants linked to industrial activity, such as PFAS, PAHs and PCBs were determined. Numerous compounds determined are linked to industrial and wastewater treatment facilities’ discharges, as well as maritime transportation and port activities. Utilization of analytical methods and instrumental techniques which cover different chemical groups provides the ability to determine a wide variety of pollutants, facilitating a holistic approach on the baseline of pollution, while also allowing more robust environmental monitoring.