Microplastics quantitative analysis of the landfill soil from Musaka sanitary dumpsite in Buea, Cameroon

Abstract

For half a decade, microplastics (MPs) contamination in soils has gained worldwide apprehension due to the complexity of its physio chemical behavior especially in Cameroon where sanitary dumpsite and illegal dumping are delocalized without any health considerations. Landfill which is used for the disposal of waste in the world, can store 21– 42% of the plastic waste produce globally. Eventhough marine pollution is still at basic level within our territory, information on soil pollution by microplastics, lacks systematic and research-based evidence. This study aims at establishing baseline awareness on the spatiotemporal distribution of microplastics in soil from the Musaka Dumpsite, Buea. 50g of unmixed soil sample was randomly collected from 20 points, with 2 collections done/point in two depths from topsoil (2cm) and at 20cm depth using a soil hand auger alongside 2 replicates soil sample taken on both side of the rectangular dumpsite width of surface area 800 m2, for each month over 2 months. Each sample/point was stored in a 3mm thick polythene bag, properly labeled and further carried to laboratory for analysis. The soil samples were thoroughly dried (at 105°c) and sieved (2mm sieve) and an established step by step organic matter digestion, density separation, particle extraction and identification using stereo-microscope aided by 40X magnifier were applied. Microplastics were found in all sampled soil and a total of 3,528 particles/1000g with mean concentration of 3.58 particles/g weighing 0.58g/g on average. Higher microplastics concentrations were observed on points around the centre of dumpsite northwest. Soil MPs accumulation significantly varied temporally and spatially at p = 0.05. ANOVA and Spearman’s rank correlation used shows linear relationships between the two soil depths studied. In terms of soil MPs analysis, 69.7% of the MPs were predominant on soil sampled at the 20cm depth. Equally, 53.1% (1874) of the microplastics found were made up of old weathered plastic (OWP) than recently weathered plastic (RWP), 18.1% (638). Per size class, 1 – 1.99 mm class were 50.1% (1766 particles) dominant with mean size of 1.5mm. Colour examination revealed white (20.1%) followed by black (14.7%) colours soil MPs were dominant. The shape class also showed that irregular (41.8%) and degraded (23.6%) shaped MPs had the highest abundance/particle. Lastly, fragment and sponge/foam shaped MPs predominant with particle concentration of 878 (24.9%) and 529 (15%) respectively. The soil MPs detection limit ranged from 0.9 – 5.07 mm. Hence, the results show that the abundance and accumulation of MPs in the landfills is an overlong process. The results of this study provide some baseline evidence and reaffirm that landfill can be a potential source of MPs bio-accumulation. This study also indicates that MPs are comparatively prolonged outcome of human induced activities which can significantly cause changes in terrestrial ecosystems.