Title of dataset: Catchment scale assessment of macroplastic pollution in the Odaw river, Ghana

Creators: Rose Boahemaa Pinto, Linda Bogerd, Martine van der Ploeg, Kwame Duah, Remko Uijlenhoet, Tim H.M. van Emmerik


Related Publication: Catchment scale assessment of macroplastic pollution in the Odaw river, Ghana

Description: 
We present a catchment scale assessment of macroplastic transport for the Odaw, Accra, Ghana by monitoring macroplastics at three different environmental compartments (land, riverbank, and river) at different spatial scales along the catchment.

To correlate the macroplastic distribution in the catchment to the land-use  type and physical transport processes in the river, the catchment was sub-divided into three zones: (1) non-urban riverine, (2) urban riverine, and (3) urban tidal (see Research_data.xlsx) .

We then develop a conceptual model for the macroplastic transport in the catchment between the different environmental compartments (land, riverbank, and river) and betwen the catchment zones. 

The monitoring and sampling of the macroplastics and non plastics at each of the environmental compartments in the Odaw catchment was done on three different days (11,16, and 23 ) in December, 2021 at ten different locations.

Floating macroplastics:

We monitored the floating plastic and other non-plastic litter in the river using the visual counting approach. This method involved the counting of floating macroplastics and non-plastics from bridges.
Ten bridge locations based on safety and accessibility along the Odaw river were selected for monitoring. 
Each bridge was sectioned into monitoring waypoints depending on the width of the bridge,the amount of litter (macroplastics and non plastics) floating at that bridge, and the field view of an observer.
Three waypoints were identified for six bridges, two waypoints for three bridges and one waypoint for only one bridge. 

At each bridge waypoint, floating macroplastics were monitored four times at a 2 minute timestep and categorised according to the aggregated seven macroplastic polymer types ( PET, PO Soft, PO hard, multilayer, PS, EPS, and Other plastics). 
Counted non-plastics were also segregated into rubber, textile, paper, wood, metal, glass, sanitary, and medical.
Overall time spent in monitoring at each bridge was 30 minutes.

Land and riverbank monitoring:

A  5 by 2 m2 area was indicated as the standard survey area for each land and riverbank location in the catchment. 
However, due to insanitary and unsafe conditions at some locations, limiting the accessibility for sampling, the surveyed area varied.
Sampled litter within a survey area at either land or riverbank was collected, counted, and categorised according to the River-OSPAR list (see Research_data.xlsx). 

This River-OSPAR list allows for the detailed categorisation of 110 litter items.
Some litter items were added (water sachet, glue small bottle, pieces of rubber carpet, electronics, ceramics, and  facemask) or removed (nurdles) to fit the mismanaged litter found in the catchment during field work.
For the purpose of analysis, the River-Ospar litter items were also aggregated into the seven macroplastic polymer types (PET, PO Soft, PO hard, multilayer, PS, EPS, and Other plastics).
This aggregated categorisation allowed for comparison among the different environmental compartments.

Finally, we defined macroplastic hotspot locations by first estimating the 75th percentile of the macroplastic transport or density at each environmental compartment over the study period as the threshold. 
Compared each macroplastic transport or density at each of the sampling locations per day to the defined threshold and checked its consistency above the specified threshold for at least two sampling days ( since sampling was done for three days) over the sampling period.


Note for this study, only macroplastic data was analysed though we monitored and sampled non plastics.


Keywords: Catchment, macroplastic pollution, river, land, riverbank, hotspot


This dataset contains 
1. an excel file named "Research_data.xlsx" which contains
        - coordinates for all sampling locations (Sheet 1: Sampling locations coordinates), 
        - data on the floating macroplastics and non plastics (Sheet 2: River monitoring),
        - data on the sampling of macroplastics and non plastics on land and riverbank (Sheet 3: Land and riverbank sampling),
        - Delineation of the catchment (Sheet 4:Catchment zone delineation)
        - River Ospar list and the macroplastic polymer type aggregation (Sheet 5: River Ospar list _aggregated)
2. Field pictures for each of the field sampling days


This dataset is published under the CC BY (Attribution) license. This license allows reusers to distribute, remix, adapt, and build upon the material in any medium or format, so long as attribution is given to the creator.
