5. Acksen et al.

100 days

107

500 days

Marine Pollution Bulletin 228 (2026) 119525

+ 1072

30°N

>0°N

20°N +

LO°N

x
_- A_
30°W

1000 days

20°W

—m.— 0
0.22

BB

30°W

Da
20°W

5000 davs

a
10°W

—+A Ü
- 0.17

30°N IN

A0°N +

—
#

A 10-2

50°N

A 10-2

40°N

30° +

30°N

20°N

LO°N =

°

20°N

LO°N

a:

5

10°S5

10°S5

20°5
dl, 0
- 0.12

z0°s A ,
50°W 40°W 30°W 20°W 10°W 0°
Fig. 6. Residence probability of particles (A) 100 days, (B) 500 days, (C) 1000 days, and (D) 5000 days before reaching the shores of Säo Vicente based on the
backward simulations with the Lagrangian ocean model PARCELS. Particles from the three release zones NW, NE and S are summarized in this figure. Arrows show
surface velocities, averaged in space and time (10 vear mean velocities 2007-2017). The black circles mark the location of Säo Vicente.
4.4. Land-based and ocean-based debris sources

D: Lu
90°W 80°W 70°W 60°W 50°W 40°W 30°W 20°W 10°W 0°

-0
> 0.17

a given site, which would require extensive knowledge about the prevailing
 environmental conditions.
The polymer composition we observed, i.e. PE (69%), PP (30%), PS
(1%) and PVC (0.03%), is very similar to those that other studies reported
 from sandy beaches worldwide: Microplastics <5 mm from
shores in the Northern Ionian Sea consisted mainly of PE (67%), followed
 by PP (18%), PS (4%) and PVC (1%) (Digka et al., 2017), while
Älvarez-Hernändez et al. (2019) reported PE (69%), PP (18%), and PS
(4%) for Tenerife. Tiwari et al. (2019) conducted surveys in the Arabian
Sea and in the Palk Strait between India and Sri Lanka and also found PE
to be the most abundant polymer (43%), followed by PET (17%), PS
(17%) and PP (12%). The fact that PE and PP are commonly the most
abundant polymers is not surprising, since they account for half of the
global plastic production (Geyer et al., 2017) and have been identified as
the most abundant floating polymers in the ocean (Erni-Cassola et al.,
2019).

To fully understand the pollution patterns on the oceanic island Säo
Vicente, it is important to examine the source of the macrodebris and
mesoplastic particles found here. Assumptions regarding the source of
the collected debris can be made in three ways: Assessing the varying
anvironmental conditions on the beaches, the connection between
macro- and mesoplastic and the composition of the beach debris.
However, our work does not allow us to quantify the amount of debris
>riginating from land- or ocean-based sources.
The orientation of a beach is an important factor determining the
abundance of debris arriving from the ocean. It influences the beached
debris abundance as it determines the level of exposure to winds, waves,
and ocean currents (Da Silva Ferreira et al., 2025). On Sao Vicente,
mesoplastic particle abundances and macrodebris densities were higher
at beaches that are oriented towards the north and east, such as Praia
Norte or Salamansa, than on those that face the south or west, ie., Sao