Impacts of solid waste management site on some toxic elements contamination of the surrounding soil in Akure, Nigeria.

The distribution of potentially toxic elements (PTEs) such as zinc (Zn), copper (Cu), lead (Pb), nickel (Ni), cadmium (Cd), and chromium (Cr), their potential bioavailability, extent of contamination and potential risk of dumpsite and surrounding soil samples were appraised. Three (3) soil samples were collected randomly from within the dumpsite and three (3) soil samples were also obtained 50 m away from the perimeter fence of the dumpsite. PTEs in the bulk and fractionated portions were determined using inductively coupled plasma - optical emission spectrometry (ICP-OES). The results showed that the concentrations of all the PTEs analysed were higher in the dumpsite soil samples than the surrounding samples, suggesting an impact of the dumpsite activities on the soil. The distribution of PTEs varied significantly within the different fractions of both the surrounding and dumpsite soils and their presence were more of anthropogenic than geogenic. The calculated contamination factor/pollution load index (CF/PLI) revealed that the surrounding soil samples fell within the range of moderate contamination, except for Cu and Cr which showed very high contamination. Cd showed the highest value (60.4) for potential ecological risk index (PERI) at the surrounding area. However, the value of Cd in the surrounding soil samples indicated a low ecological risk. The total concentrations of the PTEs were lower than their corresponding target values for both national and international standards, except for Cd (0.15 mg/kg) and Cu (37.3 mg/kg). The study concluded that the dumping of various wastes at the dumpsite was found to be a contributing factor to PTEs contamination of soil at the study area. Hence, an engineered landfill for Akure metropolis is recommended to replace the existing practice.

Assessment of Microplastics and Potentially Toxic Elements in Surface Sediments of the River Kelvin, Central Scotland, United Kingdom.

Contamination of the environment by microplastics (MPs), polymer particles of <5 mm in diameter, is an emerging concern globally due to their ubiquitous nature, interactions with pollutants, and adverse effects on aquatic organisms. The majority of studies have focused on marine environments, with freshwater systems only recently attracting attention. The current study investigated the presence, abundance, and distribution of MPs and potentially toxic elements (PTEs) in sediments of the River Kelvin, Scotland, UK. Sediment samples were collected from eight sampling points along the river and were extracted by density separation with NaCl solution. Extracted microplastics were characterised for shape and colour, and the polymer types were determined through attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy. Pollution status and ecological risks were assessed for both the microplastics and PTEs. Abundance of MPs generally increased from the most upstream location (Queenzieburn, 50.0 ± 17.3 particles/kg) to the most downstream sampling point (Kelvingrove Museum, 244 ± 19.2 particles/kg). Fibres were most abundant at all sampling locations, with red, blue, and black being the predominant colours found. Larger polymer fragments were identified as polypropylene and polyethylene. Concentrations of Cr, Cu, Ni, Pb and Zn exceeded Scottish background soil values at some locations. Principal component and Pearson's correlation analyses suggest that As, Cr, Pb and Zn emanated from the same anthropogenic sources. Potential ecological risk assessment indicates that Cd presents a moderate risk to organisms at one location. This study constitutes the first co-investigation of MPs and PTEs in a river system in Scotland.

Environmental impacts of covid-19 pandemic: Release of microplastics, organic contaminants and trace metals from face masks under ambient environmental conditions.

The covid-19 pandemic era was characterized by heavy usage and disposal of medical face masks, now estimated at over 1.24 trillion. Few studies had attempted to demonstrate the release of microplastics from face masks using simulated conditions and application of mechanical forces, far different from the effects experienced by face masks dumped in the open environment, in landfills and dumpsites. In the current study, we monitored the release of microplastics, organic contaminants and toxic metals from medical face masks degraded under normal outdoor environmental conditions, over a period of 60 weeks. We showed that face mask's decomposition proceeded via sunlight (UV) - initiated oxidative degradation, leading to the replacement of methylene (CH2-) and alkyl (CH3-) groups in face mask's polypropylene backbone with hydroxyl and ketonic functional groups. Organic compounds released from decaying face masks into the surrounding soil included alkanes, alkenes, carboxylic acids/diesters and phthalate esters. Mean maximum concentration of phthalates in the soil ranged from 3.14 mg/kg (diethyl phthalate) to 11.68 mg/kg di(2-ethylhexyl) phthalate. Heavy metals, including Cu, Pb, Cd, As, Sn and Fe, were released into the soil, leading to contamination factors of 3.11, 2.84, 2.42, 2.26, 1.80 and 0.99, respectively. Together, the metals gave a pollution load index (PLI) of 2.102, indicating that they constitute moderate pollution of the soil surrounding the heap of face masks. This study provides a realistic insight into the fate and impacts of the enormous amounts of face masks, disposed or abandoned in soil environments during the covid-19 pandemic.

Influence of electrolyte composition and pH on glyphosate sorption by cow-dung amended soil.

This study investigated the pH-dependent relationship between glyphosate and soils before (NS) and after amendment with cow-dung, CD (SACD). Sorption isotherms were generated using batch equilibration techniques from CaCl2, KCl, CaSO4 and Ca(H2PO4)2 background electrolytes. Linear partition coefficients decreased with increase in pH in the order: CaCl2>KCl > CaSO4>Ca(H2PO4)2, which reflect both the effect of the inorganic anion in terms of competition and the cation in terms of bridging interactions. However, soil amendment with CD minimized the inhibitory effect of pH increase on glyphosate sorption. Variations in glyphosate sorption from CaCl2 and Ca(H2PO4)2 were attributed to fraction of hydrophilic contribution while variations in sorption from CaCl2 and KCl were attributed to Ca-bridging and ranged from 22 to 70% across the two soils. Estimated hydrophobic partitioning ( KOCpH ) systematically decreased with increasing soil solution pH from 36 to 3% and 5 to <1% in NS and SACD, respectively. Greater sorption in NS over SACD was partly attributed to higher phosphate level in SACD which is preferentially sorbed over glyphosate. This study noted CD application as soil amendment for agriculture could impede glyphosate sorption and facilitate its off-site leaching and contamination of surface and groundwater.