Polychlorinated biphenyls (PCBs) remain persistent contaminants in tropical coastal ecosystems and pose potential risks to aquatic food webs and human health. PCB inputs at Araromi Beach likely originate from informal e-waste handling and artisanal fishing activities common to Nigeria's coastal communities. This study investigated the bioaccumulation dynamics and trophic transfer of PCBs in mud crabs, Scylla paramamosain, from Araromi Beach through a multi-matrix assessment of water, sediment and crab tissues. Nineteen PCB congeners were quantified using gas chromatography-mass spectrometry, and congener-specific bioaccumulation factors were calculated to evaluate matrix-to-organism transfer. Human health risks associated with crab consumption were assessed using toxic equivalency, lifetime average daily dose, lifetime cancer risk and hazard quotient metrics for adult and child exposure scenarios. Total PCB concentrations followed the hierarchy crab (2.09 +/- 0.02 ppm) greater than sediment (0.89 +/- 0.01 ppm) greater than water (0.10 +/- 0.00 ppm), with significant differences observed among matrices. PCB180 exhibited the highest concentration in crab tissues (1.40 +/- 0.00 ppm) and showed the greatest bioaccumulation potential relative to environmental media. Bioaccumulation patterns indicated preferential accumulation of highly chlorinated congeners, suggesting strong hydrophobic partitioning and trophic transfer potential. Human health risk assessment indicated elevated lifetime cancer risk values for crab consumers, with children exhibiting higher susceptibility than adults. These findings highlight the need for continuous monitoring of PCB contamination and the implementation of seafood safety management strategies in coastal environments.
Tobacco, with its substantial biomass and strong cadmium (Cd) enrichment capacity, is a potential candidate for phytoremediation of Cd-contaminated soil. However, its Cd accumulation characteristics under field conditions remain unclear. In this study, a field experiment (soil Cd concentration: 0.9 mg & centerdot;kg(-)& sup1;) demonstrated that the Cd accumulation per tobacco plant reached 1148.1 mu g, with a dry biomass of 432.2 g in the mowing treatment. Cd was detected in all parts of the tobacco plant, with the highest concentration found in the leaf mesophyll (7.0 mg & centerdot;kg(-)& sup1;), and the predominant Cd chemical form was the less toxic NaCl-extractable fraction, which may be associated with the plant's Cd detoxification mechanism. Additionally, the Cd concentration was higher in the lateral roots than in the main roots, higher in the stem phloem than in the xylem, and a certain amount of Cd was also present in the flowers. Compared to 60 d after transplanting, the Cd concentrations in leaves, stems and roots, as well as the total and available Cd concentrations in rhizosphere soil, were significantly reduced at 180 d after transplanting. This decline may be attributed to Cd depletion in the rhizosphere soil and dilution effects caused by rapid plant growth. Nevertheless, the total Cd accumulation per plant at 180 d was significantly higher than that at 60 d. Mowing measures increased leaf dry biomass by 1.6 times, consequently enhancing total Cd accumulation by 1.6 times. These results provide a theoretical foundation for the practical application of tobacco in remediating Cd-contaminated soil.
The Angouran Pb-Zn mine in northwest Iran, the largest in the Middle East, has been active for nearly a century, raising concerns about long-term contamination of surrounding aquatic and terrestrial environments. This study investigates the geochemical behavior and spatial distribution of potentially toxic elements (PTEs) in river water and sediments of the Allahlu River and evaluates their implications for the downstream Marash Dam. A total of 180 water and sediment samples were analyzed using ICP-MS and ICP-OES techniques. Dissolved concentrations of Pb and As in water locally exceeded World Health Organization guideline values, while sediment samples showed elevated concentrations of Zn, Pb, and Cd, reaching up to several thousand mg/kg near the mining area. Enrichment factor (EF) and geoaccumulation index (Igeo) results indicate very high enrichment and moderate to severe contamination levels for Cd, Pb, and Zn in sediments proximal to the mine, whereas Ni and Co mostly fall within low enrichment and uncontaminated to moderately contaminated classes. Metal concentrations and contamination indices decrease with increasing distance downstream, identifying the Angouran mine and nearby villages, including Qaleh Jiq and Khanik, as high-risk pollution hotspots. Overall, the results provide a comprehensive geochemical assessment that supports environmental monitoring and management strategies in mining-impacted river basins.
Lead (Pb) is one of the most toxic heavy metals and can disrupt morphological, physiological, and biochemical processes in plants. In this study, for the first time, we present a green-synthesis approach for zinc oxide nanoparticles (ZnO NPs) using Rumex dendatus leaf extract and demonstrate their efficiency in ameliorating Pb-induced toxicity in Brassica juncea (Brown mustard). The green ZnO NPs were spherical, with an average crystalline diameter of similar to 7.5 nm, showed a characteristic UV-Vis absorption peak at similar to 350 nm, and consisted of zinc (58.58%) and oxygen (41.42%) by energy-dispersive X-ray analysis. In the pot experiment, thirteen-day-old B. juncea seedlings were exposed to Pb (30, 300, and 3000 mg L-1) and ZnO NPs (2, 20, and 200 mg L-1), individually or in combination, under controlled conditions. Exposure to Pb at 3000 mg L-1 markedly inhibited plant growth and physiology, reducing root/shoot lengths and chlorophyll content by 22%, 18%, and 29%, respectively, compared with untreated controls. In contrast, ZnO NP treatment at 200 mg L-1 significantly enhanced plant growth and related traits. Notably, combined ZnO NP + Pb treatment mitigated Pb toxicity: co-treated plants showed improved root length (+18%), shoot length (+17%), fresh weight (+19%), and leaf chlorophyll content (+24%) compared with Pb-treated plants. Pb accumulation was also reduced, with root and shoot Pb uptake decreasing by 57% and 43%, respectively, relative to Pb-stressed plants. Antioxidant enzymes activities were elevated; SOD and CAT increased several-fold in ZnO NP + Pb-treated plants compared with Pb-stressed plants, indicating enhanced ROS scavenging. APX and POD levels were similarly boosted, contributing to reduced oxidative damage. Overall, green-synthesized ZnO NPs promoted B. juncea growth under Pb stress by enhancing chlorophyll content, reducing Pb uptake, and suppressing ROS-associated toxicity.
The efficacy of gaseous ozonation in eliminating indoor air pollutants has been investigated to improve indoor air quality. The ozone generator was operated until the air conditioning room attained ozone concentrations of 25, 50 and 75 ppm for 15 minutes. Rooms exposed to all ozone concentrations were efficacious in eradicating microorganisms and particulate matter (PM) within the air-conditioned room, with the level of elimination contingent upon the ozone concentration and duration of the test. Among these investigations, the 75 ppm ozone condition was the most efficacious in diminishing room microbe numbers. Ozone gas activity exerted a more pronounced effect on diminishing the number of PM. PMs within the 1.0-5.0 & micro;m range were 75%-90% eliminated following the attainment of ozone levels of 75 ppm. This inquiry suggests that pre-treatment of the air with ozone can improve the indoor air quality and make it safer for occupants. [GRAPHICS]
Lattice defect engineering is vital for semiconductor photocatalysts, where oxygen vacancies (OVs) narrow the band gap, boost visible-light utilization and create active sites. Efficient OVs introduction and structural optimization are key to enhancing catalytic performance. Previously, OVs were incorporated into Bi2O2CO3 (BOC) via UV-mediated Ni ion doping to endow visible-light responsiveness. Herein, a Z-scheme Bi2O3/Bi2O2CO3-OVs heterojunction was fabricated by calcination and UV treatment. It combines the merits of Z-scheme heterojunctions for efficient photocarrier separation and OVs for rich active sites. Under visible light, it degrades over 99% sulfadiazine within 60 min with TOC removal above 80%. Its OVs show light-induced self-healing, retaining 93% activity after 10 cycles. First-principles calculations validated the Z-scheme formation mechanism. This work offers a feasible route to self-healing OV-rich heterojunctions and guides efficient removal of sulfadiazine in water. [GRAPHICS]
