Are tropical mangroves a sink for litter leaking from land-and sea-based sources? Evidence from selected Kenyan mangroves.

Marine litter surveys were carried out to determine the role of mangroves as a sink for litter. General litter density in the mangroves was 0.088 ± 0.076 items m-2, composed mainly of plastic (85.9 %). Higher litter densities occurred in the middle (0.162 ± 0.150 items m-2) compared to the landward (0.066 ± 0.049 items m-2) and the seaward zones (0.036 ± 0.028 items m-2), indicating the important role played by the middle zone in providing a sink for litter from both land and sea-based sources. Landward zones were a sink for heavier litter from land that could easily be trapped by mangrove roots (plastic and clothing). The middle zones retained mainly the litter that are not easily trapped by the mangroves' roots in seaward and landward zones, particularly soft plastics. The seaward zones acted as a sink for litter from sea-based sources mainly marine and fishing gears, and materials used for fishing and boat repairs.

Baseline radionuclide and heavy metal concentrations in sediments of Sabaki River estuary (Kenya, Indian Ocean).

Baseline study of natural (7Be, 210Pb, 226Ra, 234Th, 228Ra, 40K) and anthropogenic (137Cs) radionuclides was carried out in two cores collected from Sabaki River estuary (Kenya, Indian Ocean). There was no exponential decrease of excess 210Pb down the cores, which did not allow dating and determination of heavy metal pollution history. The use of 137Cs as a time marker was not possible due to its low fallout rates in East Africa. The short-lived radioisotope 7Be, a tracer of river floods, confirmed 2018 flood in Sabaki River estuary. Heavy metal concentration in the two cores showed nonsystematic trends with depth. Only Pb concentration in Sabaki River estuary was higher than the background levels. Application of the "Environmental Risk from Ionising Contaminants Assessment and management" (ERICA) tool confirmed that the potential dose rates to biota from the sediment radioactivity concentrations are unlikely to pose appreciable ecological risks.