Mitigating potential of polystyrene microplastics on bioavailability, uptake, and toxicity of copper in maize (Zea mays L.).

The coexistence of polystyrene microplastics (PSMPs) and copper (Cu) has become a pressing issue for croplands. However, limited literature is available regarding the interaction of PSMPs with essential micronutrients in Cu-contaminated soils. Therefore, the present study aimed to analyze the immobilization potential of PSMPs for micronutrient bioavailability in soil and Cu toxicity in maize (Zea mays L.). A pot experiment was conducted with maize variety "Islamabad gold" exposed to varying Cu concentrations (0, 50, 100, 200, and 400 mg/kg) and PSMPs (150-250 µm size, 0, 1, and 3% w/w) via soil spiking for 60 days. The concentrations of essential micronutrients (Zn, Cu, Mn, Fe) in soil and plant tissues were measured using an atomic absorption spectrophotometer. Moreover, malondialdehyde (MDA) and antioxidant activities (superoxide dismutase, ascorbate peroxidase, catalase, and peroxidase) were recorded. The concentration of Cu showed significant reduction in post-harvesting soil by 21, 24.8, 27.6, 29.2, and 30.2% from Cu0 to Cu400 mg/kg respectively from pre-sowing soil. On the other hand, the addition of 1%PSMPs and 3%PSMPs declined Cu by 16, 21.6, 24.4, 25.9, 27.8, and 12.6, 16.5, 19.9, 23.2, 25% from Cu0 to Cu400 mg/kg respectively. Maize showed significant improvement in growth under combined exposure of Cu and 3% PSMPs compared to individual exposure. The MDA level was decreased under the combined presence of Cu and PSMPs compared to individual Cu exposure. The percentage difference with 1%PSMPs was 98.1, 95.0, 92.0, 90.0, and 89.6%, while with 3%PSMPs was 93.2, 93.2, 87.7, 81.4, and 79.2% from Cu0 to Cu400 mg/kg respectively. Moreover, the impact of PSMPs was more prominent at a 3% dose compared to a 1% dose. The findings provided significant knowledge about the potential of PSMPs to mitigate Cu toxicity in maize. Future research should incorporate a variety of particle size distributions at natural conditions for variety-specific differences.

First insights into per-and polyfluoroalkyl substance contamination in edible fish species of the Indus water system of Pakistan.

Per- and polyfluoroalkyl substances (PFASs) are a group of emerging contaminants, that have a wide range of applications in industrial and commercial products. The direct discharge of untreated industrial and domestic wastewater into freshwater bodies is a common practice in developing countries, which are the main contributors to PFASs in the aquatic environment. The situation is further worsened due to poor wastewater treatment facilities and weak enforcement of environmental regulations in countries like Pakistan. The current study was designed to assess PFASs contamination in muscle tissues of edible fish species from major tributaries of the Indus System, including Head Panjnad (HP), Head Trimmu (HT), Chashma Barrage (CB), Head Blloki (HB) and Head Qadirabad (HQ). The analysis of target PFAS was performed using ultrahigh-performance liquid chromatography coupled with a quadrupole Orbitrap high-resolution mass spectrometry. The highest levels of ∑17PFASs were observed in S. seenghala, C. mirigala from HB, and C. mirigala from HQ with a mean value of 45.4 ng g-1, 43.7 ng g-1, and 40.8 ng g-1, respectively. Overall, the compositional profile of fish samples was predominated by long-chain PFASs such as PFOA, PFOS, PFHpS, and PFDS. The accumulation of PFASs in fish species is dependent on the physiochemical properties of PFASs, characteristics of the aquatic environment, and fish species. Significant associations of PFASs with isotopic composition (p < 0.05), feeding habits (p < 0.05), and zones (p < 0.05) indicate that dietary proxies could be an important predictor of PFASs distribution among species. The C7-C10 PFASs exhibited bio-accumulative tendency with an accumulation factor ranging from 0.5 to 3.4. However, none of the fish samples had sufficiently high levels of PFOS to cause human health risk (HR < 1). For future studies, it is s recommended to conduct seasonal monitoring and the bioaccumulation pattern along trophic levels of both legacy and emerging PFASs.

Spatial distribution, compositional profile, sources, ecological and human health risks of legacy and emerging per- and polyfluoroalkyl substances (PFASs) in freshwater reservoirs of Punjab, Pakistan.

Per- and polyfluoroalkyl substances (PFASs) are a large group of chemicals reported in global environment and are responsible for various adverse impacts on humans and environment. We report a comprehensive study on occurrence of PFASs, including legacy, substitute and emerging ones, from Pakistan. Surface water samples were collected from five ecologically important freshwater reservoirs in Pakistan, namely, Head Panjnad (HP), Head Trimmu (HT), Chashma Barrage (CB), Head Blloki (HB), and Head Qadirabad (HQ). The detection frequencies of PFASs ranged between 37 %-100 %. The highest concentration of ∑15PFASs was detected at HP (114.1 ng L-1), whereas the lowest at HQ (19.9 ng L-1). Among the analyzed PFASs, 6:2 fluorotelomer sulfonic acid (6:2 FTS) and perfluorooctanoic acid (PFOA) showed maximum mean concentrations of 9.1 ng L-1 and 7 ng L-1 at HP, followed by Perfluorooctane sulfonic acid (PFOS) with level of 0.99 ng L-1 at HT. The ecological risk assessment for selected species i.e., daphnid, mysid, fish and green algae showed that PFOS, perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA) exhibited moderate risk i.e., Hazard Quotients (HQs) < 1 to the modeled organisms, whereas perfluorobutane sulfonic acid (PFBS) showed the high risk to green algae (HQs = 8.6) and PFOA presented a high risk to all the organisms (HQs ranged between 1.04 and 7.38). The level of ∑PFASs at HP (114.1 ng L-1) exceed the EU guideline value of ∑PFASs in water (100 ng L-1), however the risk quotient (RQmix) values of all age groups were < 1 implying that the detected PFASs in water do not pose risk to human health. Source apportionment through Positive Matrix Factorization (PMF) showed that industrial effluent is the main source of PFASs in freshwater reservoirs. Comparable concentrations of legacy and substitute PFASs in this study indicate that legacy PFASs are still in use adjacent to ecologically important water reservoirs.