The scale of microplastic pollution in river sediments is gradually being elucidated through an increasing number of large-scale studies. Nevertheless, microplastic distribution within a riverbed – a crucial aspect for quantification – remains poorly understood. Here we evaluate in the meandering River Lys, Belgium, how microplastic concentration varies between different sedimentary environments within the riverbed. We find that microplastic abundance is about an order of magnitude higher towards the riverbanks compared to the thalweg, corresponding with river hydrodynamics. Moreover, organic-matter and mud content are robust predictors of microplastic concentrations, apart from the outer bends, where erosion into organic-rich, muddy floodplain sediments inhibits microplastic deposition. These results increase our understanding of microplastic distribution at the small riverbed scale. They are a crucial element to guide for future sampling efforts across diverse river systems, paving the way for normalization and better quantification of microplastics trapped by river sediments and in other aquatic environments.

In order to disentangle natural climate variability from anthropogenically caused variations, environmental reconstructions of the past 2000 years have gained renewed scientific interest during the last ~20 years. Whereas climatic and environmental changes during this period, such as the Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA) are fairly well expressed in western Europe and the North Atlantic area, knowledge about equivalent changes in African climate and environment (e.g. changes in temperature and precipitation, monsoonal activity and resulting vegetation feedbacks) can be much improved. Here we present new results from Lake Chala, a crater lake in equatorial East Africa, based on sedimentary grain-size distributions. Notwithstanding the relatively minor clastic mineral component, we are able to discriminate between different aeolian and fluviatile sources of terrigenous material and to reconstruct temporal trends in their contribution to the sediment. This can be linked to both local environmental dynamics and changes in the large-scale monsoonal systems over the East African landmass. Our findings point to arid conditions during the MCA and humid conditions during the LIA, in support of regional hydroclimate history as reconstructed from other moisture-balance proxies. The results of this study form an important piece of the puzzle to better understand past changes in African environments, which is a key aspect in the debate about future climate change in one of the most climate-sensitive regions on the planet.

The scale of microplastic pollution in river sediments is gradually being elucidated through an increasing number of large-scale studies. Despite these advancements, our knowledge about the microplastic distribution within a riverbed – a crucial aspect for quantification – remains poor. Here, we study the meandering River Lys, Belgium, to evaluate how microplastic concentration varies between different sedimentary environments within the riverbed. We find that microplastic abundance is an order of magnitude higher towards the riverbanks compared to the thalweg, corresponding with hydrodynamics. Moreover, apart from the erosional area near the outer banks, organic matter content and median grain size are robust predictors of microplastic concentrations. These results significantly increase our understanding of MP distribution at the small scale of the riverbed. They are a crucial element to guide for future sampling efforts across diverse river systems, paving the way for normalization and better quantification of amounts of microplastics trapped by river sediments.

Samples of present-day aeolian dust collected with the help of various kinds of dust sampling devices are currently a widely used resource to measure distinct characteristics of aeolian transported material, such as variations in the amount of dust flux over space and/or time, chemical and mineralogical composition and isotopic signatures of the material to ultimately infer the origin of the aeolian transported sediment, to understand transport pathways and to identify the sensitivity of aeolian dust to changes in local or global climate variability. However, so far the majority of samples captured by dust traps originate from classical desert environments, such as the Saharan desert or the Australian or Asian deserts. Due to smaller sample amounts, longer depositional periods, difficulties in installing the traps, and labor-intensive trap maintenance, continuous dust-trap records from semi-arid regions are rare.In this study we present a record of aeolian dust deposits from the semi-arid region at Lake Chala, in SE Kenya/ NE Tanzania, comprising a nearly continuous sampling period of 5 years from three different locations. The first dust traps were installed in 2016 during the ICDP DeepCHALLA drilling and deliver a monthly record of dust characteristics in the area. A combination of microscopic investigations, detailed grain-size measurements, as well as mineralogical analysis allows us to infer changes in the amount and characteristics of the monthly deposited aeolian sediments and provide a first insight into seasonal changes and fluctuations of atmospheric forcing factors responsible for dust transport and the deposition in our study area.