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In April 2020, the Covid-19 pandemic changed human behaviour worldwide, creating an increased demand for plastic, especially single-use plastic in the form of personal protective equipment. The pandemic also provided a unique situation for plastic pollution studies, especially microplastic studies. This study looks at the impact of the Covid-19 pandemic and three national lockdowns on microplastic abundance at five sites along the river Thames, UK, compared to pre-Covid-19 levels. This study took place from May 2019–May 2021, with 3-L water samples collected monthly from each site starting at Teddington and ending at Southend-on-Sea. A total of 4480 pieces, the majority of fibres (82.1 %), were counted using light microscopy. Lockdown 2 (November 2020) had the highest average microplastic total (27.1 L−1). A total of 691 pieces were identified via Fourier Transform Infrared Spectroscopy (FTIR). Polyvinyl chloride (36.19 %) made up the most microplastics identified. This study documents changes in microplastic abundance before, during and after the Covid-19 pandemic, an unprecedented event, as well as documenting microplastic abundance along the river Thames from 2019 to 2021. • 82.1 % (3679 pieces) of microplastics were fibres. • Covid-19 status significantly impacted microplastic abundance. • Average microplastic abundance was highest during Lockdown 2 (27.1 pieces L−1). • Microplastic abundance decreased from pre Covid-19 (2019) to post Covid-19 (2021). • The most commonly identified polymers were PVC, PS and PCP. [ABSTRACT FROM AUTHOR]

This research has investigated the structural changes and pozzolanic activity produced in acid activated smectite clay. The activation treatment used HCl at different concentrations, using different times and at a range of temperatures. X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy coupled with energy dispersive X-ray spectroscopy were used to determine the acid dissolution mechanism and characterise the activated clay mineral structure. Acid activation causes dehydroxylation of smectite clay, followed by leaching of octahedral cations. This results in the formation of a silica-rich amorphous phase that exhibits substantial pozzolanic activity compared to the same clay sample that had undergone calcining treatment at 850. The optimum sample was activated for 8 h using 5 M HCl at 90 °C. This was 93 % amorphous. Mortar prisms prepared with 25 % replacement of Portland cement by acid activated smectite produced 93 % compressive strength of plain Portland cement mortar. [ABSTRACT FROM AUTHOR]