A comprehensive review of urban microplastic pollution sources, environment and human health impacts, and regulatory efforts.

Microplastic (MP) pollution in urban environments is a pervasive and complex problem with significant environmental and human health implications. Although studies have been conducted on MP pollution in urban environments, there are still research gaps in understanding the exact sources, regulation, and impact of urban MP on the environment and public health. Therefore, the goal of this study is to provide a comprehensive overview of the complex pathways, harmful effects, and regulatory efforts of urban MP pollution. It discusses the research challenges and suggests future directions for addressing MPs related to environmental issues in urban settings. In this study, original research papers published from 2010 to 2024 across ten database categories, including PubMed, Google Scholar, Scopus, and Web of Science, were selected and reviewed to improve our understanding of urban MP pollution. The analysis revealed multifaceted sources of MPs, including surface runoff, wastewater discharge, atmospheric deposition, and biological interactions, which contribute to the contamination of aquatic and terrestrial ecosystems. MPs pose a threat to marine and terrestrial life, freshwater organisms, soil health, plant communities, and human health through ingestion, inhalation, and dermal exposure. Current regulatory measures for MP pollution include improved waste management, upgraded wastewater treatment, stormwater management, product innovation, public awareness campaigns, and community engagement. Despite these regulatory measures, several challenges such as; the absence of standardized MPs testing methods, MPs enter into the environment through a multitude of sources and pathways, countries struggle in balancing trade interests with environmental concerns have hindered effective policy implementation and enforcement. Addressing MP pollution in urban environments is essential for preserving ecosystems, safeguarding public health, and advancing sustainable development. Interdisciplinary collaboration, innovative research, stringent regulations, and public participation are vital for mitigating this critical issue and ensuring a cleaner and healthier future for urban environments and the planet.

PAHs and hopanes in the surface sediments of Qatar coast and their ecological risks: Comparison with regional and global coastal regions.

The distribution, characteristics, sources and ecological risks of polycyclic aromatic hydrocarbons (PAHs) and hopanes in the surface sediments collected along the Qatar coast were investigated. Concentration of ∑14PAHs and hopanes ranged between 0.076 and 7.04 ng g-1 (mean: 2.60 ng g-1), 100 and 700 ng g-1 (mean: 205 ng g-1), respectively. Sediment samples were dominated by high molecular weight PAHs composition (4-6 rings). Diagnostic ratios of PAH concentrations showed both petrogenic and pyrogenic origins of PAHs, with a higher percentage of pyrogenic sources. The ecological risk levels of PAHs were estimated using sediment quality guidelines (SQG), mean probable effect level quotient values (PEL-Q), carcinogenic toxic equivalent quantity (TEQ), and risk quotient (RQ) evaluation methods. The calculated TEQ values (0.00012-0.85 ng g-1) were lesser than those in other locations around the globe, and were also within the safe level (600 ng g-1) suggested by the Canadian soil quality guidelines.

Detection and assessment of marine litter in an uninhabited island, Arabian Gulf: A case study with conventional and machine learning approaches.

In 2018, the Ministry of Municipality and Environment, Qatar removed 90 t of marine litter (ML) from the Ras Rakan Island (RRI), a remote uninhabited island in the Arabian Gulf (hereinafter referred to as Gulf). To identify the sources of ML and understand the post-cleaning ML accumulation rate, a ML survey was conducted around RRI in 2019. A total of 1341 ML items were found around RRI with an average abundance of 3.4 items/m2. In addition, a machine learning approach was applied to extract the quantity and types of ML from 10,400 images from the sampling sites (beaches) to make the ML clean-up process and monitoring effort more efficient. The image coordinates of ML objects were used to train an object detection algorithm 'You Only Look Once (YOLO-v5)' to automatically detect ML from video data. An image enhancement technique was performed to improve the quality of unclear images. The best performing YOLO-v5 model had 90% of mean Average Precision (mAP) while maintaining near real-time processing speeds at 2 ms/image. The abundance of ML around RRI was higher than that found on the coast of mainland Qatar. 61.5% of the sampling locations are considered as 'extremely dirty' based on Clean Coast Index. Windward beaches had higher ML concentrations (derived from neighbouring countries) than the leeward beaches. Like RRI, most of the uninhabited islands in the Arabian Gulf are home to many seabirds and sea turtles, and could act as major sinks for ML deposition. Therefore, implementation of this machine learning technique to all islands allows estimating and mitigating the load of ML for achieving a sustaining and a cleaner ocean.

Seasonal variation, polymer hazard risk and controlling factors of microplastics in beach sediments along the southeast coast of India.

Microplastics (MPs) and its associated organic and inorganic contaminants are one among the significant health hazards to almost all biota, including human. We investigated the polymer hazard risk and its adsorbed contaminants in MPs at six prominent beaches of Chennai on the southeast coast of India. The spatial variation of MPs during the northeast (NE) monsoon (range: 76-720 items/kg, mean: 247.4 items/kg) was higher than that during southwest (SW) monsoon (range: 84-498 items/kg, mean: 302.7 items/kg). In both the seasons, polyethylene (PE) and polypropylene (PP) were the dominant polymers and fibre was the predominant shape of MPs, likely to be derived from fishing, textile and urban activities in this region. Scanning electron microscope (SEM) images exhibited various surface weathering features including grooves, cracks, fractures, adhering particles, pits, vermiculate textures and fibre reinforcements. Energy dispersive X-ray spectrometer (EDS) results showed that MPs have adsorbed major (Si, Al, Na, Mg, Ca, Fe and Ti) and trace (Cu, Cr, Ni, Pb and Zn) metals. Though pollution load index (PLI) presented low degree of MP contamination in the beach sediments, hazardous polymers such as polyvinyl chloride (PVC), polyamide (PA) and polystyrene (PS) contributed to high polymer hazard index (PHI) and potential ecological risk index (PERI), posing very high risk to the biota. The trajectories obtained from particle-tracking coupled with hydrodynamic simulation clearly showed that 20% of MPs settled along the coast and the remaining moved towards north, alongshore and offshore (∼50 km) within 30 days, and in NE monsoon due to current reversal, the floating debris and MPs have drifted towards south, ∼40 km in 30 days, indicating the role of circulation in the fate and transport pathways of plastic debris.

Hitchhiking of encrusting organisms on floating marine debris along the west coast of Qatar, Arabian/Persian Gulf.

The floating marine debris (FMD) and the associated rafting communities are one of the major stressors to ecosystem services, global biodiversity and economy and human health. In this study, assemblages of encrusting organisms on different types of stranded FMD along the west coast of Qatar, Arabian/Persian Gulf (hereafter referred to as 'Gulf') were examined. The analysis showed 18 fouling species belonging to 5 phyla (Annelida, Anthropoda, Bryozoa, Mollusca and Porifera) on the FMD. The most abundant fouling species were the encrusting Amphibalanus amphitrite, polychaete Spirobranchus kraussii, Bryozoan species and Megabalanus coccopoma. More number of taxa were found on larger size FMD than on smaller FMD. Some of the barnacle rafting types were found to be non-indigenous species. The central and northwest parts of the Qatar had more FMD and fouled species than in other locations. Winds and the prevailing hydrodynamic conditions (waves and currents) played an important role in the transportation and distribution of FMD and associated organisms along the west coast of Qatar. The present study confirmed that huge amount of bio-fouled FMD items, causing great damage to biodiversity, drift in the surface layer of ocean and eventually strand onto the beaches. We propose a simple, but an effective management plan for FMD and associated organisms at regional scale to restore the biodiversity, sustainability and health of the marine ecosystem in the Gulf.

WorldView-3 mapping of Tarmat deposits of the Ras Rakan Island, Northern Coast of Qatar: Environmental perspective.

This study characterizes the spectral behavior of tarmats and maps the tarmat deposits found along the coast of Ras Rakan Island off Qatar using WorldView-3 (WV-3) sensor data. The laboratory spectra of tar materials showed diagnostic absorptions features at 0.6 and 1.1 µm in the visible and near-infrared (VNIR) and 1.52, 1.73, 2.04, and 2.31 µm in the short wave infrared (SWIR) region. The panchromatic grayscale image and FCC showed the tarmat deposit as a linear warp feature between beach and water. The mapping of deposits using WV-3 data by decorrelation stretch and Linear Spectral Unmixing (LSU) methods discriminated the tarmats from the sandy soil, vegetation and sabkha features in a different tone. The capability of WV-3 sensor and the potential of image processing methods were verified by mapping the tar distribution of the Ras Ushayriq and NE of Al Ruwais.

Assessment of potential ecological risk of microplastics in the coastal sediments of India: A meta-analysis.

Abundance, chemical composition and ecological risk of microplastics (MPs) in terrestrial and marine environments have merited substantial attention from the research communities. This is the first attempt to comprehend the ecological risk of MPs in sediments along the Indian coast using meta-data. Polymer hazard index (PHI), pollution load index (PLI) and potential ecological risk index (PERI) were used to evaluate the quality of sediments. Areas have high PHI values (>1000) due to the presence of polymers with high hazard scores such as polyamide (PA) and polystyrene (PS). According to PLI values, sediments along the west coast of India (WCI) are moderately contaminated with MPs (PLI: 3.03 to 15.5), whereas sediments along the east coast of India (ECI) are less contaminated (PLI: 1 to 6.14). The PERI values of sediments along the Indian coast showed higher ecological risk for the metropolitan cities, river mouths, potential fishing zones and the remote islands.

Sources, spatial distribution and characteristics of marine litter along the west coast of Qatar.

The spatial distribution, sources and characteristics of marine litter (ML) from 36 locations spread over 12 beaches along the west coast of Qatar have been assessed. A total of 2376 ML items with varying sizes were found with an average abundance of 1.98 items/m2. The order of abundance of ML along the coast was as follows: plastics (71.4%) > metal (9.3%) > glass (5.1%) > paper (4.4%) > fabric (4.0%) > rubber (3.9%) > processed wood (2.0%). Locations in the south and northwest coasts of Qatar had significantly higher concentrations of ML. Surprisingly, nearly 47% of the beached polyethylene terephthalate (PET) bottles were derived from the countries bordering the Arabian/Persian Gulf (Gulf), and most of them were produced in the last 2 years. The plastic materials were drifted by winds and currents to the Qatar coast. Gulf circulation provides evidence to the pathways of ML beached on the Qatar coast.

Spatial distribution, structural characterization and weathering of tarmats along the west coast of Qatar.

Oil pollution resulting from natural and anthropogenic activities in the Arabian Gulf as well as oil residue in the form of tarmat (TM) deposited on the coast is a major environmental concern. The spatial distribution, chemical composition and weathering pattern of tarmat along the west coast of Qatar has been assessed based on the TM samples collected from 12 coastal regions. The range of TM distribution is 0-104 g m-1 with an average value of 9.25 g m-1. Though the current TM level is thirty-fold lesser than that was found during 1993-1997 (average 290 g m-1), the distribution pattern is similar. The results of ATR-FTIR spectroscopy indicate that aromatic compounds are higher in the north (N) coast TMs than those found in the northwest (NW) and southwest (SW) coasts, and Carbonyl Index values indicate that TM of NW coast is highly weathered compared to those found in the N and SW coasts.

Assessing the source of oil deposited in the surface sediment of Mormugao Port, Goa - A case study of MV Qing incident.

In June 2016, a cruise vessel was grounded in the Mormugao Port, resulting in unnoticed oil spill. The surface water and sediment samples were collected from the vicinity of the ship, and also an oil sample from the ship (OIL). These samples were subject to petroleum biomarker such as pentacyclic triterpenes (hopanes) and compound specific carbon isotopic (δ13C) analyses to assess the source of hydrocarbon pollution in the Mormugao Port. While no clear trend was observed in water samples, the bottom surface sediments did show an identical pattern of hopanes with the oil. The chemometric analyses of hopane Diagnostic Ratios (DRs) and δ13C ratios confirmed the ship oil as the source of oil pollution in sediments. Whereas the water is comparatively more dynamic than the sediment, the physical processes arising out of winds, waves, tides and currents might have dispersed the oil away from the grounded ship.

Influence of 2015 flood on the distribution and occurrence of microplastic pellets along the Chennai coast, India.

The sources, distribution, surface features, polymer composition and age of microplastic pellets (MPPs) in surface sediments along the Chennai coast during March 2015 (pre-Chennai flood) and November 2015 (post-Chennai flood) were characterised using a Stereoscopic microscope and FTIR-ATR spectroscopy. White MPPs were the most abundant, and specifically polyethylene (PE) and polypropylene (PP) were the dominant polymer types of MPPs found on the coast during both the times. The abundance of MPPs in November 2015 was three-fold higher than those found in March 2015, confirming that huge quantity of fresh MPPs washed through Cooum and Adyar rivers from land during the flood. The winds and surface currents during November were the driving forces for the transportation and deposition of MPPs from the sea to beaches. The results of this study will be useful to formulate beach MPPs litter management policies to effectively create long-term solutions.

Characteristics, seasonal distribution and surface degradation features of microplastic pellets along the Goa coast, India.

Microplastic pellets (MPPs) are ubiquitous contaminants, recognised as a serious threat to the biota in coastal, estuarine and marine environment. The distribution, abundance, weathering and chemical characteristics of MPPs on the beaches of Goa, and their transport to the coast during the southwest (SW) monsoon are discussed in this paper. MPP samples collected from six sandy beaches were categorised based on colour and polymer types using Stereoscope microscope and FTIR-ATR spectroscopy, respectively. White colour MPPs were the most abundant, and Polyethylene (PE) and Polypropylene (PP) were the dominant polymer types of MPPs deposited on all the beaches. Carbonyl index values showed that MPPs collected in June 2015 (representing SW monsoon) were 'new', whereas the MPPs collected in January 2015 were 'aged', showing that MPPs are arriving at Goa coast only during SW monsoon due to conducive hydrodynamic conditions. Characteristics of MPPs suggest that they could be originated primarily from ocean-based sources. The winds and surface currents during SW monsoon are the driving forces for the transportation and deposition of MPPs on the Goa beaches. The results of this study will be useful to the National 'Clean India' program for effective plastic debris removal management.

Depositional record of trace metals and degree of contamination in core sediments from the Mandovi estuarine mangrove ecosystem, west coast of India.

The concentrations of seven trace metals (Fe, Mn, Cu, Cr, Co, Pb and Zn) in three sediment cores were analysed to assess the depositional trends of metals and their contamination level in the Mandovi estuary, west coast of India. All sediment cores showed enrichment of trace metals in the upper part of core sediments and decrease in concentration with depth, suggesting excess of anthropogenic loading (including mining activities) occurred during the recent past. Scanning electron microscope (SEM) images distinguished the shape, size and structure of particles derived from lithogenic and anthropogenic sources in core sediments. The geo-accumulation index (I(geo)) values indicate that Mandovi estuary is 'moderately polluted' with Pb, whereas 'unpolluted to moderately polluted' with Fe, Mn, Cu, Cr, Co and Zn. The comparative analysis of trace metals revealed that Fe and Mn were highly enriched in the Mandovi estuary compared to all other Indian estuaries.

Petroleum hydrocarbon concentrations in eight mollusc species along Tamilnadu coast, Bay of Bengal, India.

Eight mollusc species and sediment samples collected from three different stations along Tamilnadu coast, Bay of Bengal, India were analysed for the levels of petroleum hydrocarbons to elucidate the status of the petroleum residues in mollusc meant for human consumption. The concentrations of petroleum hydrocarbons in sediments along Tamilnadu coast varied from 5.04-25.5 microg/g dw (dry weight). High concentration of petroleum hydrocarbons in the sediment of Uppanar estuary (25.5 +/- 1.45 microg/g dw) was perhaps land and marine based anthropogenic sources of this region. The petroleum hydrocarbon residues in eight mollusc species collected from Uppanar, Vellar and Coleroon estuaries varied between 2.44-6.04 microg/g ww (wet weight). Although the concentration of petroleum hydrocarbons in sediment of the Uppanar region was markedly higher than the background, the petroleum hydrocarbon residues in mollusc collected from Uppanar estuary did not suggest bioaccumulation. The results signified that industrial growth has affected the aquatic environments and regular monitoring will help to adopt stringent pollution control measures for better management of the aquatic region.

Petroleum hydrocarbon concentrations in ten commercial fish species along Tamilnadu coast, Bay of Bengal, India.

BACKGROUND, AIM, AND SCOPE: The aim of the present study was to evaluate the distribution of petroleum hydrocarbons in ten commercial fish species and water samples in three estuaries along Tamilnadu coast, Bay of Bengal, India. MATERIALS AND METHODS: Fish and water samples collected from Tamilnadu coast, India, were extracted and analyzed for petroleum hydrocarbons by ultraviolet fluorescence (UVF) spectroscopy. RESULTS: The petroleum hydrocarbon concentration (PHC) in coastal waters and fish species varied between 2.28 and 14.02 µg/l and 0.52 and 2.05 µg/g, respectively. The highest PHC concentration was obtained in Uppanar estuarine waters (14.02 ± 0.83) and the lowest was observed in Vellar estuarine waters (2.28 ± 0.25). DISCUSSION: Among the ten fish species, Sardinella longiceps have high PHC concentration from all the locations. This study suggests that S. longiceps can be used as a good biological indicator for petroleum hydrocarbon pollution in water. CONCLUSIONS: The concentration of petroleum hydrocarbons in coastal waters along Tamilnadu coast is markedly higher than that in the background, but there is no evidence for its increase in fish of this region. From a public health point, petroleum hydrocarbon residue levels in all fish samples analyzed in this study are considerably lower than the hazardous levels. RECOMMENDATIONS AND PERSPECTIVES: At present, as Tamilnadu coastal area is in a rapid development stage of new harbour, chemical industries, power plants, oil exploration and other large-scale industries, further assessment of petroleum hydrocarbons and the various hydrodynamic conditions acting in the region are to be studied in detail and continuous pollution monitoring studies should be conducted for improving the aquatic environment. The results will also be useful for pollution monitoring program along the coastal region and also to check the levels of petroleum hydrocarbons.

Environmental magnetic and petroleum hydrocarbons records in sediment cores from the north east coast of Tamilnadu, Bay of Bengal, India.

In this study, mineral magnetic properties and petroleum hydrocarbons were statistically analysed in four sediment cores (C1, A1, T1 and K1) from the north east coast of Tamilnadu, India to examine the feasibility of PHC concentrations assessment using magnetic susceptibility. The C1 and A1 cores reveal a clear horizon of increase in PHC above 35 and 50 cm respectively suggesting the excess anthropogenic loading occurred in the recent past. Magnetic properties which were enhanced in the upper part of the sediment cores were the result of ferrimagnetic minerals from anthropogenic sources. Factor analysis confirmed that the input of magnetic minerals and petroleum hydrocarbons in Chennai coastal sediments are derived from the same sources. The present study shows that instead of expensive and destructive PHC chemical methods, magnetic susceptibility is found to be a suitable, cheap and rapid method for detailed study of petroleum hydrocarbon contamination in marine sediments.

Petroleum hydrocarbon concentrations in marine sediments along Chennai Coast, Bay of Bengal, India.

The spatial and temporal distribution of petroleum hydrocarbons (PHC) in marine sediments along the Chennai coast, Bay of Bengal was quantified by Ultra-Violet Fluorescence (UVF) Spectroscopy. The concentration of PHC in surface sediments varied from 1.88 to 39.76 ppm. The highest values obtained in the northern part of the study area, where shipping activities and land-based waste waters disposed into sea through the rivers like Kuvam and Adayar. The Adayar (7.26-16.83 ppm) and Kuvam (5.5-39.72 ppm) cores reveal a clear horizon of increase in PHC above 50 and 35 cm respectively. PHC values showed a decreasing pattern with depth in all sediment cores suggesting the excess anthropogenic loading occurring in the recent past. The present study revealed that the PHC values of Chennai coastal sediments are lower than the values reported from selected costal areas including the sediment of the Mumbai coast (7.6-42.8 ppm), Arabian Sea. The results will be useful for pollution monitoring program along the coastal region and also to check the level of petroleum hydrocarbons in marine sediments.