Freely dissolved pore water concentrations are difficult to assess in complex matrixes such as soils or sediments. In this study, a negligible-depletion partitioning-based sampling technique was applied to measure freely dissolved pore water concentrations. A poly(dimethylsiloxane) (PDMS)-coated glass fiber was exposed to a slurry of a soil spiked with several PAHs at concentrations ranging from 2 to 2000 mg/kg. PAH-concentrations in the PDMS coating increased linearly with the total soil concentration until a certain maximum was reached. Freely dissolved pore water concentrations were calculated using PDMS-water partition coefficients, and the calculated maximum pore water concentrations corresponded with the aqueous solubility of the tested compounds. Furthermore, the sampling technique is very sensitive because it can detect freely dissolved pore water concentrations in the ng/L range for the tested PAHs. Freely dissolved pore water concentrations are an important parameter for the exposure of organisms in soil. Saturation of the pore water with increasing soil concentrations should therefore be considered in soil toxicity testing. Sorption coefficients that were calculated from freely dissolved concentrations were slightly higher than estimates based on octanol-water partition coefficients. These differences are discussed in relation to the effects of dissolved organic matter in soil pore water on the determination of sorption coefficients.

The novel coronavirus disease 2019 (COVID-19) has become a global pandemic with more than 4 million confirmed cases and over 280,000 confirmed deaths worldwide. Evidence exists on the influence of temperature and humidity on the transmission of related infectious respiratory diseases, such as influenza and severe acute respiratory syndrome (SARS). This study therefore explored the effects of daily temperature and humidity on COVID-19 transmission and mortality in Lagos state, the epicenter of COVID-19 in Nigeria. Correlation analysis was performed using incidence data on COVID-19 and meteorological data for the corresponding periods from 9th March to 12th May, 2020. Our results showed that atmospheric temperature has a significant weak negative correlation with COVID-19 transmission in Lagos. Also, a significant weak negative correlation was found to exist between temperature and cumulative mortality. The strength of the relationship between temperature and the disease incidence increased when 1 week and 2 weeks’ predetection delays were put into consideration. However, no significant association was found between atmospheric humidity and COVID-19 transmission or mortality in Lagos. This study contributes more knowledge on COVID-19 and will benefit efforts and decision-making geared towards its control.

Clustered regularly interspaced short palindromic repeats (CRISPR) technology has enabled genetic engineering feats previously considered impracticable, offering great hopes for solutions to problems facing society. We consider it timely to highlight how CRISPR can benefit public health, medicine, and agriculture in sub-Saharan Africa (SSA) and offer recommendations for successful implementation.

The relative health of benthic invertebrate populations is threatened by both dissolved and strongly-bound contaminants. Sediment-bound contaminants can be mobilized and metabolized in the guts of deposit-feeders and may lead to even more potent derivatives. For this reason, measures of parent substance concentrations in organisms are not a suitable exposure indicator when substantial biotransformation can occur. In this study, we assessed the concentration of waterborne 14C-benzo[a]pyrene (BaP) in Chironomus riparius larvae and in the oligochaete Lumbriculus variegatus at different levels of dissolved organic carbon (DOC). These two species have different biotransformation capabilities. Polydimethylsiloxane (PDMS) fiber was used to assess the freely-dissolved concentrations for the prediction of uptake and elimination kinetics. Exposure concentrations decreased due to the presence of DOC. Radioactivity that corresponded to the metabolites exceeded 90% of total extractable fractions in C. riparius, and suggested that BaP metabolism was faster than uptake from solution. However, only 10% of the extracted activity was attributed to metabolites in L. variegatus. Measured tissue concentrations and model-predicted uptake and elimination rates showed that L. variegatus mainly accumulated parent compound, whereas C. riparius accumulated mainly metabolites. No effect of DOC was observed on the biotransformation of BaP in either species.

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