Microplastics interact with benthic biostabilization processes

Marine microplastics accumulate in sediments but impacts on ecosystem functions are poorly understood. Microplastics interactions with stabilizing benthic flora/fauna or biostabilization processes, have not been fully investigated, yet this is critical for unravelling microplastics effects on ecosystem-scale processes and functions. This is also vital for understanding feedback processes that may moderate the stock and flow of microplastics as they are transported through estuaries. The relationships between sedimentary microplastics, biota, environmental properties and sediment stability from field sediments, were examined using variance partitioning (VP) and correlation analyses. VP was used to identify common and unique contributions of different groups of variables (environmental, fauna and microplastic variables) to sediment stability. The influence of microplastic presence (fragment/fiber abundances and microplastic diversity) on sediment stability (defined using erosion thresholds and erosion rates) was demonstrated. Furthermore, microplastics appeared to mediate the biostabilizing effects of environmental properties (including microorganisms) and fauna. Environmental properties and sediment stability could also explain the variation in microplastics across sites suggesting biostabilizing properties may mediate the abundance, type and diversity of microplastics that accumulate in the bed. The potential for microplastics to influence biota and biostabilization processes and mediate microplastic resuspension dynamics within estuaries is discussed.

ESTIMATION OF EFFICIENCY OF USING BRUCITE FOR DECONTAMINATION OF ARSENIC CONTAINING WATER

In the paper it is outlined that mining enterprises activity is accompanied with high emissions of arsenic into the hydrosphere. Sorption purification method with application of brucite as natural mineral is proposed. As the arsenic is toxic and demand for it is limited, one of the requirements for removing of the contaminant is its collection into low-toxic and low-soluble sediments to be available for dumping. The analysis of research results is presented. The interaction mechanism of toxic substance with the sorbent is studied. It is shown that sorption includes complex of physical and chemical processes such as electrostatic interaction, ion exchange, chemical interaction of arsenic ions with mineral surface with creation hardly soluble compounds. Tests of sediment stability have been carried out by statistic method. High efficiency of using brucite for decontamination of arsenic containing water is proved.

Quantifying biostabilisation effects of biofilm-secreted and extracted extracellular polymeric substances (EPSs) on sandy substrate

Microbial assemblages (“biofilms”) preferentially develop at water–sediment interfaces and are known to have a considerable influence on sediment stability and erodibility. There is potential for significant impacts on sediment transport and morphodynamics, and hence on the longer-term evolution of coastal and fluvial environments. However, the biostabilisation effects remain poorly understood and quantified due to the inherent complexity of biofilms and the large spatial and temporal (i.e. seasonality) variations involved. Here, we use controlled laboratory tests to systematically quantify the effects of natural biofilm colonisation as well as extracted extracellular polymeric substances (EPSs) on sediment stability. Extracted EPSs may be useful to simulate biofilm-mediated biostabilisation and potentially provide a method of speeding up timescales of physical modelling experiments investigating biostabilisation effects. We find a mean biostabilisation effect due to natural biofilm colonisation and development of almost 4 times that of the uncolonised sand. The presented cumulative probability distribution of measured critical threshold for erosion of colonised sand reflects the large spatial and temporal variations generally seen in natural biostabilised environments. For identical sand, engineered sediment stability from the addition of extracted EPSs compares well across the measured range of the critical threshold for erosion and behaves in a linear and predictable fashion. Yet, the effectiveness of extracted EPSs to stabilise sediment is sensitive to the preparation procedure, time after application and environmental conditions such as salinity, pH and temperature. These findings are expected to improve biophysical experimental models in fluvial and coastal environments and provide much-needed quantification of biostabilisation to improve predictions of sediment dynamics in aquatic ecosystems.