The present study discusses elevated groundwater arsenic (As) and fluoride (F(-)) concentrations in Mailsi, Punjab, Pakistan, and links these elevated concentrations to health risks for the local residents. The results indicate that groundwater samples of two areas of Mailsi, Punjab were severely contaminated with As (5.9-507 ppb) and F(-) (5.5-29.6 ppm), as these values exceeded the permissible limits of World Health Organization (10 ppb for As and 1.5 ppm for F(-)). The groundwater samples were categorized by redox state. The major process controlling the As levels in groundwater was the adsorption of As onto PO4 (3-) at high pH. High alkalinity and low Ca(2+) and Mg(2+) concentrations promoted the higher F(-) and As concentrations in the groundwater. A positive correlation was observed between F(-) and As concentrations (r = 0.37; n = 52) and other major ions found in the groundwater of the studied area. The mineral saturation indices calculated by PHREEQC 2.1 suggested that a majority of samples were oversaturated with calcite and fluorite, leading to the dissolution of fluoride minerals at alkaline pH. Local inhabitants exhibited arsenicosis and fluorosis after exposure to environmental concentration doses of As and F(-). Estimated daily intake (EDI) and target hazard quotient (THQ) highlighted the risk factors borne by local residents. Multivariate statistical analysis further revealed that both geologic origins and anthropogenic activities contributed to As and F(-) contamination in the groundwater. We propose that pollutants originate, in part, from coal combusted at brick factories, and agricultural activities. Once generated, these pollutants were mobilized by the alkaline nature of the groundwater.

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BACKGROUND The bioremediation versatility of soil indigenous microbial community for the degradation of oil contaminated soils has been evidenced previously. In this study, three dominant bacterial strains, Pseudomonas putida (P. putida) and two Pseudomonas aeruginosa (P. aeruginosa) (accession numbers ATCC‐27853, BAA‐427, and ATCC‐49128), were isolated from three different oil‐contaminated sites to evaluate their bioremediation potential. Degradation potential was determined against two compounds, naphthalene and pyrene, from polycyclic aromatic hydrocarbons (PAHs) in batch experiment. RESULTS The bacterial strains were effective in degrading naphthalene and pyrene. Further, the degradation potential of these compounds was correlated with total organic carbon (TOC). Among the bacterial strains, P. putida (accession number ATCC‐27853) effectively degraded naphthalene and pyrene by 92% and 83%, respectively. The other bacterial strain, P. aeruginosa (ATCC‐27853), equally degraded the naphthalene (83.6%) but differed considerably for pyrene, with the lowest removal efficiency of 24.2% at 3 ppm. Growth profiles of the proposed bacterial strains, P. putida (accession number ATCC‐27853), P. aeruginosa (accession number BAA‐427), and P. aeruginosa, ATCC‐49128), revalidated through colony‐forming unit (CFU·mL−1). P. putida showed the highest cell count 5.06 × 108 (CFU·mL−1) for naphthalene. CONCLUSION This study highlights that isolated Pseudomonas strains showed the highest degrading activity for naphthalene and pyrene‐degrading without the addition of any chemical or co‐substrate within a short interval. Overall, findings indicate that inoculation of the bacterial strains belonging to Pseudomonas species can stimulate low and high weight PAH compounds degradation and maintain the bacterial biomass, thus accelerating the dissipation of soil PAHs. It further provides evidence for perspectives on the potential of bacterial community assembly of PAH‐contaminated soils. © 2021 Society of Chemical Industry (SCI).

Low-concentration ozonation was developed as a novel technique to control the excess biomass in volatile organic compound (VOC) biofilters. In order to understand the reaction mechanism between ozone and biomass, the changes in properties of ozone exposed extracellular polymeric substances (EPS) were investigated in this study. EPS was sequestered from the biofilm, obtained from a biofilter treating gaseous toluene, and then it was exposed to gaseous ozone at 272 ± 22 ppm continuously for 12 h. The total organic carbon (TOC) results indicated that low concentration ozone could not mineralize the EPS to carbon dioxide (CO2) completely. The excitation-emission matrix fluorescence spectroscopy (EEM) results demonstrated that ozone preferred to attack the benzene ring and specific amino acid residues (such as tryptophan) on the protein chain. High performance size-exclusion chromatography (HPSEC) results confirmed that the protein molecules were depolymerized after ozone attack, while the molecular weight of polysaccharides was not much affected by ozone. During ozonation, few volatile organic compounds (VOCs), such as carboxylic acids, aldehydes, ketones, benzaldehyde and by-products of toluene, were generated, which confirms a minor change in the TOC concentration of EPS. Results revealed that low concentration ozone can reduce the molecular weight of biofilter EPS which can be a key reason for controlling biomass accumulation. Additionally, this can be used to study the composition of biofilm EPS from biofilters.

Globally, kitchen waste (KW) and sewage sludge (SS) are two important forms of organic wastes that need immense attention during handling and management. As the characteristics and components of KW vary significantly with respect to location and season, it is often difficult to understand the behavior of KW during the (co-)digestion process. Therefore, this study aimed to investigate the synergistic influence of KW over SS and vice versa during anaerobic (co-)digestion. Anaerobic mono-digestion and co-digestion of SS and KW, considering three different mixing ratios SS:KW; (SK1-25:75, SK2-50:50, SK3-75:25), was conducted to investigate their specific methane yields (SMY) and biodegradability (BD). The modified Gompertz equation was used to estimate the theoretical methane potential and used as a reference for experimental data assessment. The results demonstrated that SMYs were 212 and 368 L kg −1 VS added for SS, and KW, respectively. Under the category of co-digestion, sample SK2 (SS:KW; 50:50) had the highest BD of 91% as compared to digestion of SS (61%) and KW (74.9%) separately. A synergistic effect on methane production was witnessed with all ratios and the maximum was noticed with SK2, ca. 40%, which can be ascribed to the enhanced hydrolysis because of the addition of KW, which is readily degradable by nature. Further, this study could be used as guidelines to the design and optimization of the co-digestion process.

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Gold nanoparticles (AuNPs) were synthesized using citrate reduction, also known as the Turkevich method. The AuNPs were compared with the commercially available product and later subjected to characterization. The AuNPs were 13 nm in diameter with a 2.7 × 108 M−1cm−1 extension coefficient. The calculated concentration was 5.1 nM through the Beer–Lambert law using UV–vis absorbance spectra. Further detailed characterization was applied, such as scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), elemental analysis using electro and DLS instruments, energy-dispersive X-ray spectroscopy (EDS), XRD, and Zeta potential. The synthesized AuNPs had a higher UV-absorbance peak of 0.93 in comparison to commercially available nanoparticles at 5.8 identical conditions. The characterization confirmed successful fabrication of colloidal-citrate-capped AuNPs and their dispersed and aggregated state with induced salt concentration. The shape and morphology were confirmed through XRD, showing a face-centered cubic lattice of {111}, confirmed at 38.1 round shape, and a crystalline lattice. AuNPs tend to be applied in sensing, detection, drug delivery, pharmaceuticals, and other applications in the environment and materials. Other applications include environmental contaminant detection, colorimetric sensors, antimicrobial applications, biosensing and drug delivery, tissue engineering, nanomedicines, optoelectronics, and catalysts.