Data on macro(micro)plastics and hydrophobic organic contaminants in the Gulf of Guinea coastal psammitic beaches

The ubiquity of microplastics in coastal environments and marine ecosystems is a significant concern because they have a strong affinity for organic contaminants. This paper presents the first reported data on hydrophobic organic contaminants (HOCs) and microplastics particles (MPs, 1–5 mm) in lagoon and beach sediments along the Gulf of Guinea coastline (SE Atlantic). Sampling was carried out between August and November 2019. Ten sites were designated for each location, and sediment samples were taken along three transects: high waterline, drift waterline, and current waterline. Sediment samples were extracted through density floatation procedure and sieving. Primary data on polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and organochlorine pesticides (OCPs) associated with MPs are provided, as well as detailed information on sampling coordinates, plastic types, and their relative abundance. Refer to the research publication ``Microplastics and associated organic pollutants in beach sediments from the Gulf of Guinea (SE Atlantic) coastal ecosystems'' (Fred-Ahmadu et al., 2022) for detailed discussion and interpretation of the reported data.


a b s t r a c t
The ubiquity of microplastics in coastal environments and marine ecosystems is a significant concern because they have a strong affinity for organic contaminants. This paper presents the first reported data on hydrophobic organic contaminants (HOCs) and microplastics particles (MPs, 1-5 mm) in lagoon and beach sediments along the Gulf of Guinea coastline (SE Atlantic). Sampling was carried out between August and November 2019. Ten sites were designated for each location, and sediment samples were taken along three transects: high waterline, drift waterline, and current waterline. Sediment samples were extracted through density floatation procedure and sieving. Primary data on polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and organochlorine pesticides (OCPs) associated with MPs are provided, as well as detailed information on sampling coordinates, plastic types, and their relative abundance. Refer to the research publication "Microplastics and associated organic pollutants in beach sediments from the Gulf of Guinea (SE Atlantic) coastal ecosystems" (Fred-Ahmadu et al., 2022) for detailed discussion and interpretation of the reported data.

Value of the Data
• First report on the occurrence and distribution of microplastics-sorbed PAHs, OCPs and PCBs in beach sediments along the Gulf of Guinea coast (SE Atlantic) is documented. • Microplastics-HOCs contamination in lagoon and psammitic beach sediments is reported.
• A baseline data for future investigations on microplastic contamination, origin and impacts of organic contaminants in the studied coastlines is established. • Data could be employed to conduct a comparative assessment of microplastic pollution in marine shoreline sediments from other regions of the world. • The data will contribute towards addressing UN SDGs 14 and 15, and stakeholders' campaign against plastic pollution.

Data Description
The dataset comprises a survey of microplastics (MPs, 1-5 mm) and concentrations of hydrophobic organic contaminants (PAHs, OCPs, PCBs) in psammitic sediment samples collected from designated sampling locations along the Lagos lagoon, Atican, Elegushi, Eleko, and Oniru beaches' coastlines in the Gulf of Guinea (SE Atlantic). Tables 1 and 2 provide the sampling codes and location descriptions of the study areas. Fig. 1 shows photographs of microplastics extracted   from sediment samples, while Fig. 2 presents the physical characterisation of microplastics. The Attenuated Total Reflectance -Fourier Transform Infra-Red (ATR-FTIR) Spectrometry was used to determine the polymer types as presented in Table 3 . The concentrations of hydrophobic organic contaminants detected in sedimentary microplastic samples collected along the beach and lagoon drift and high waterlines have been reported [1] ( Figs. 3 and 4 ).

Sediment Sampling and Preservation
Sediment samples were collected between August and November, 2019 at 40 sites from five lagoon and beach locations namely Lagos lagoon, Atican, Elegushi, Eleko and Oniru along the coastlines of the Gulf of Guinea (SE Atlantic). The lagoon and beach locations were divided into three transects (High (HW), drift (DW), and current (CW) waterlines) and beach sediment samples were taken from 10 sites (100 m inter-site apart) per transect using a 0.5 × 0.5 × 0.2 m quadrat. A stainless-steel scoop was used to collect the upper 2 -3 cm of beach sediment [ 2 , 3 ]. The sampled sediment samples were obtained from the high and drift waterlines at designated sites on the lagoon and beach locations [3] . Each piece of identified organic matter found in the quadrat was hand-selected and discarded. After sampling and separation, all the sediment samples collected were sealed in sterile Ziploc bags and placed in aluminium foil.

Sample Treatment
The procedure described by [4] was modified to extract microplastics from sediment samples collected from the lagoon and beach waterlines. The sediment samples were air-dried and later sieved through 5 mm mesh stainless steel sieves. The plastic debris clinging to the 5 mm filter were carefully collected, and the sediment that passed through the sieve was rinsed with a saturated sodium chloride solution. The crude extracts from the density flotation procedure were strained through a 1 mm filter, and the residues were kept for further processing as described by [5][6][7] . Visual and stereomicroscopy identification of the MPs were performed, and the types of polymers were determined using an Agilent 630 Cary ATR-FTIR spectroscopy.

Fourier Transform Infrared (FTIR) Analysis
The composition of all items identified as MPs was characterized following the procedure outlined by [3] using an Agilent Cary 630 FTIR spectrophotometer. Before each reading, the ATR plate was wiped off with alcohol. Each time a new set of measurements was completed, the surfaces were thoroughly cleaned before using the FTIR. For the identification of polymers, the Agilent polymer ATR library was employed. The following details pertain to the FTIR analysis: The ATR-FTIR system has an 8 cm −1 resolution, 32 sample scans, and a range of 40 0 0-650 cm1. The absorption bands of each polymer were analysed and matched with the polymer ATR library with an acceptable match quality set at ≥80%. The results were confirmed using validated polymer spectral data [8] .

Sample Extraction for PAHs, OCPs, PCBs Analysis
MPs samples were placed in amber glass vials with 5 mL of cyclohexane/ethyl acetate mixture in 1:1 ratio. These were either hard or foam pieces, while composite samples were a mix of MP types. The vials were agitated for 2 min on a vortex machine and then placed in an ultrasonic bath for 20 min. The extracts were transferred to new vials, and the extraction procedures were repeated twice, with at least 15 mL aliquot recovered [4] . Prior to GC-Q-MS analysis, the extracts were concentrated to 1 mL, transferred to amber vials, and kept in the fridge at 4 °C. The temperature of the column oven was programmed as follows: 100 °C for 0 min, the increased at 20 °C per minute to 180 °C, then at 10 °C per minute to 280 °C, which was held for 2 min. The total run time was 16 min, followed by a 1 min post-run at 70 °C.

Quality Control
Procedural blanks were periodically measured using certified standards. Triplicate extractions were carried out in order to optimize the extraction efficiency. Extracts were homogenized and concentrated to 1 mL before GC-Q-MS analysis. The calibration curves' R 2 values ranged from 0.995 to 0.998, 0.995 to 0.999, and 0.991 to 0.999 for PAHs, PCBs, and OCPs, respectively. All organic contaminants had spike recoveries between 81.3 and 127.3% [9] . Before the analysis, all equipment employed in the extraction procedure were washed, rinsed and dried with deionized water. To limit contamination by airborne fibres during sample preparation, extraction, and analysis, cotton-made laboratory coats, glassware and garments made from non-synthetic materials were used at all times.

Ethics Statements
This study did not involve human or animal subjects, and no data from social media platforms were used.

Funding
This research was supported by the Covenant University Centre for Research, Innovation and Discovery (CUCRID), through the Covenant University Seed Grant. The authors are grateful to Covenant University for providing publication assistance.

Primary Data Availability
Microplastics and sorbed hydrophobic organic contaminants in lagoon and beach sediments (Raw Data) (Mendeley Data). The primary data as presented here represent the concentrations of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) in sedimentary microplastic samples collected from coastal beaches and lagoonal ecosystem of the south east Atlantic Ocean, Gulf of Guinea, Nigeria. The aggregated concentrations of each organic pollutant were plotted as shown on tab labelled as Sum plot.

Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Data Availability
Microplastics and sorbed hydrophobic organic contaminants in lagoon and beach sediments (Original data) (Mendeley Data).

CRediT Author Statement
Nsikak U. Benson