Freshwater ecosystems are being contaminated by heavy metal pollution. The primary source of contamination is wastewater discharged from urban, industrial, and agricultural facilities. The contaminated water contains hazardous amounts of heavy metals mixed in the freshwater ecosystem, causing deleterious impacts on marine life and humans. This review paper highlights the contamination of the freshwater ecosystem of Pakistan with heavy metals. Heavy metals' concentration in sediments, water, and fish were assessed in the food chain, and their relationship with sites and sources was explored. It was observed that heavy metals present in freshwater and sediments bio-accumulate into fish organs. It was also found that some parts of freshwaters such as the rivers Ravi, Chenab, Kabul, and Indus were highly contaminated, and they imposed negative impacts on fish and human health. The River Ravi, receiving a huge amount of industrial and sewage wastewater from urban centers and industries of Central Punjab, was highly contaminated compared to other rivers of Pakistan. The ecosystem health of River Indus was the best among all the rivers of Pakistan due to the enormous volume of water flow and less number of industrial units along with it. Freshwater fish of the rivers Indus, Chenab, and Jhelum are consumable for humans. The presence of heavy metals also causes social, environmental, and economic problems. Therefore, the wastewater should be treated before discharge into freshwater streams and rivers to lessen the harmful impacts of heavy metals on marine life and human beings.

This study presents the fabrication and characterization of mixed matrix membranes (MMMs) incorporating green-synthesized silver nanoparticles (AgNPs) using Hibiscus Rosa sinensis extract within a polyethersulfone (PES) matrix for nanofiltration (NF) application. The membranes were evaluated for their pure water permeability, salt rejection, dye removal, and antifouling performance. Results showed that the membrane with 0.75 wt% AgNPs exhibited the highest pure water permeability of 36 L/m² h⁻¹ bar⁻¹ attributed to increased porosity and enhanced hydrophilicity. Addition of 0.75wt% AgNPs resulted in significant improvements, with NaCl rejection increased from 32 to 57%, MgSO₄ from 26 to 67%, and CaCl₂ from 27 to 41%. Antifouling tests revealed that the 0.75 wt% AgNPs membrane had the lowest irreversible fouling and highest flux recovery due to the antimicrobial action and improved surface properties of AgNPs. Importantly, the performance of the fabricated membranes align with loose nanofiltation characteristcs, as evidence by high dye rejection rates coupled with moderate rejection of salts. This study highlights the potential of green-synthesized AgNPs as effective nanofillers for developing high-performance and environmentally sustainable membranes into wastewater treatment.

This study investigated the adsorption of Oxytetracycline (OTC) from pharmaceutical wastewater using a kappa carrageenan based hydrogel (KPB). The aim of the present study was to explore the potential of KPB for long-term pharmaceutical wastewater treatment. A sustainable adsorbent was developed to address oxytetracycline (OTC) contamination. The hydrogel’s structural and adsorption characteristics were examined using various techniques like Scanning Electron Microscope (SEM), Fourier Transform Infrared (FTIR), X-ray powder diffraction (XRD), and kinetic models. The results revealed considerable changes in the vibrational modes and adsorption bands of the hydrogel, suggesting the effective functionalization of Bentonite nano-clay. Kappa carrageenan based hydrogel achieved the maximum removal (98.5%) of OTC at concerntration of 40 mg/L, pH 8, cotact time of 140 min and adsorbent dose of 0.1 g (KPB-3). Adsorption of OTC increased up to 99% with increasing initial concentrations. The study achieved 95% adsorption capacity for OTC using a KPB film at a concentration of 20 mg/L and a 0.1 g adsorbent dose within 60 min. It also revealed that chemisorptions processes outperform physical adsorption. The Pseudo-Second-Order model, which emphasized the importance of chemical adsorption in the removal process, is better suited to represent the adsorption behavior. Excellent matches were found that R² = 0.99 for KPB-3, R² = 0.984 for KPB-2 and R² = 0.989 for KPB-1 indicated strong chemical bonding interactions. Statisctical analysis (ANOVA) was performed using SPSS (version 25) and it was found that pH and concentration had significant influence on OTC adsorption by the hydrogel, with p-values less than 0.05. The study identified that a Kappa carrageenan-based hydrogel with bentonite nano-clay and polyvinyl alcohol (PVA) can efficiently remove OTC from pharmaceutical effluent, with a p-value of 0.054, but weak positive linear associations with pH, temperature, and contact time. This research contributed to sustainable wastewater treatment and environmental engineering.

Forests ecosystem plays a significant role in supplying multiple services given the unique properties of forest soils, in which the elements of C, N, and P are essential to support soil fertility and site productivity. However, soil properties at different soil depths between plantation forests (PF) and natural forests (NF) have not been well quantified. Therefore, the current study was carried out in the Qilian Mountains of northwest China to determine the difference between PF and NF in the soil properties, both physical (e.g., bulk density, BD) and chemical (e.g., pH value, the contents, stocks, and stoichiometry of soil organic carbon (SOC), total N (TN), and total P (TP)). Research analyzed soil samples at different depths (0–20, 20–40, 40–60, 60–80, and 80–100 cm). The results showed that the soils’ pH values and BD were significantly higher (p≤ 0.05) in PF than in NF and increased with soil depth. The contents of SOC, TN, and TP decreased considerably with soil depth and then stabilized at the soil depth of 80–100 cm. The NF showed significantly higher (p≤ 0.05) SOC, TN, and TP contents than PF, confirming that the soil quality of PF had not fully recovered yet. The stocks of SOC and TN quickly decreased with soil depth up to 40–60 cm and stabilized gradually. Additionally, the soil stoichiometry of C:P and N:P decreased significantly with rising soil depth, while the C:N ratio remained unchanged. The N:P and C:P ratios were lower in PF than in NF, while the C:N ratio was higher in PF than in NF. In conclusion, the results show that the soils of NF present significantly higher stocks of SOC and TN but lower (or nearly equal) TP stocks than PF (under the same age group and tree species composition). These results imply that maintaining NF and avoiding their replacement by PF can help keep higher soil quality and related ecosystem services.

Overuse of pesticides in agricultural soil and dye-polluted effluents severely contaminates the environment and is toxic to animals and humans making their removal from the environment essential. The present study aimed to assess the biodegradation of pesticides (cypermethrin (CYP) and imidacloprid (IMI)), and dyes (malachite green (MG) and Congo red (CR)) using biofilms of bacteria isolated from pesticide-contaminated soil and dye effluents. Biofilms of indigenous bacteria, i.e., Bacillus thuringiensis 2A (OP554568), Enterobacter hormaechei 4A (OP723332), Bacillus sp. 5A (OP586601), and Bacillus cereus 6B (OP586602) individually and in mixed culture were tested against CYP and IMI. Biofilms of indigenous bacteria i.e., Lysinibacillus sphaericus AF1 (OP589134), Bacillus sp. CF3 (OP589135) and Bacillus sp. DF4 (OP589136) individually and in mixed culture were tested for their ability to degrade dyes. The biofilm of a mixed culture of B. thuringiensis + Bacillus sp. (P7) showed 46.2% degradation of CYP compared to the biofilm of a mixed culture of B. thuringiensis + E. hormaechei + Bacillus sp. + B. cereus (P11), which showed significantly high degradation (70.0%) of IMI. Regarding dye biodegradation, a mixed culture biofilm of Bacillus sp. + Bacillus sp. (D6) showed 86.76% degradation of MG, which was significantly high compared to a mixed culture biofilm of L. sphaericus + Bacillus sp. (D4) that degraded only 30.78% of CR. UV–VIS spectroscopy revealed major peaks at 224 nm, 263 nm, 581 nm and 436 nm for CYP, IMI, MG and CR, respectively, which completely disappeared after treatment with bacterial biofilms. Fourier transform infrared (FTIR) analysis showed the appearance of new peaks in degraded metabolites and disappearance of a peak in the control spectrum after biofilm treatment. Thin layer chromatography (TLC) analysis also confirmed the degradation of CYP, IMI, MG and CR into several metabolites compared to the control. The present study demonstrates the biodegradation potential of biofilm-forming bacteria isolated from pesticide-polluted soil and dye effluents against pesticides and dyes. This is the first report demonstrating biofilm-mediated bio-degradation of CYP, IMI, MG and CR utilizing soil and effluent bacterial flora from Multan and Sheikhupura, Punjab, Pakistan.

This study is first to test Pakistani honey bees, Apis dorsata and A. cerana honey samples as anti biofilm, anti quorum sensing (QS) and biofilm dispersal agents honey against multispecies biofilm of bacteria (obtained from obese patients). Briefly, five previously identified isolates Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus, Morganella morganii and Klebsiella pneumoniae (MT448672-MT448676) were selected. Antibiogram study of all five isolates was tested against three antibiotics viz., erythromycin (20 µg/mL), lincomycin (100 µg/mL) and rifampicin (100 µg/mL). In order to form multispecies biofilm, identified bacteria were grown in batch culture by mixing equal volumes (OD590nm = 0.1) of 2, 3 and 5 bacterial isolates. In total 11 groups (g1-g11) were made. Crystal violet (CV) staining method was used to evaluate the antibiofilm potential and biofilm dispersal potential of both honey samples. QS inhibition in P. aeruginosa was measured following culture supernatant method. Antibiogram study showed significant (p < 0.05) resistance by P. aeruginosa against tested antibiotics. E. coli, M. morganii and K. pneumoniae were significantly susceptible to erythromycin and S. aureus to lincomycin. Both honey samples at 2% and 5% concentrations showed significant (p < 0.05) inhibition potential of multispecies biofilm by all test groups (g1-g11). Though A. dorsata honey significantly inhibited biofilm formation at 2 and 5% against all groups but 2% concentration was highly significant against g2-g4 groups. Regarding A. cerana honey, 2% concentration was significantly effective against g1, g4-g7 and g9-g11 groups. Both honey samples significantly inhibited QS at 2 and 5%. The 5% concentration of A. dorsata honey significantly dispersed biofilm by all groups compared to 2% which showed dispersal potential only by g2 and g3 groups. Accordingly, honey samples showed significant antibiofilm, anti-QS and biofilm dispersal potentials thus can be considered as good alternative to antibiotics.