Efficient performance of InP and InP/ZnS quantum dots for photocatalytic degradation of toxic aquatic pollutants.

In recent years, the growing concern over the presence of toxic aquatic pollutants has prompted intensive research into effective and environmentally friendly remediation methods. Photocatalysis using semiconductor quantum dots (QDs) has developed as a promising technology for pollutant degradation. Among various QD materials, indium phosphide (InP) and its hybrid with zinc sulfide (ZnS) have gained considerable attention due to their unique optical and photocatalytic properties. Herein, InP and InP/ZnS QDs were employed for the removal of dyes (crystal violet, and congo red), polyaromatic hydrocarbons (pyrene, naphthalene, and phenanthrene), and pesticides (deltamethrin) in the presence of visible light. The degradation efficiencies of crystal violet (CV) and congo red (CR) were 74.54% and 88.12% with InP, and 84.53% and 91.78% with InP/ZnS, respectively, within 50 min of reaction. The InP/ZnS showed efficient performance for the removal of polyaromatic hydrocarbons (PAHs). For example, the removal percentage for naphthalene, phenanthrene, and pyrene was 99.8%, 99.6%, and 88.97% after the photocatalytic reaction. However, the removal percentage of InP/ZnS for pesticide deltamethrin was 90.2% after 90 min light irradiation. Additionally, advanced characterization techniques including UV-visible spectrophotometer (UV-Vis), photoluminescence (PL), X-ray diffractometer (XRD), energy-dispersive spectrometer (EDS) elemental mapping, transmission electron microscopy (TEM), and thermogravimetric analysis (TGA) were used to analyze the crystal structure, morphology, and purity of the fabricated materials in detail. The particle size results obtained from TEM are in the range of 2.28-4.60 nm. Both materials (InP and InP/ZnS) exhibited a spherical morphology, displaying distinct lattice fringes. XRD results of InP depicted lattice planes (111), (220), and (311) in good agreement with cubic geometry. Furthermore, the addition of dopants was discovered to enhance the thermal stability of the fabricated material. In addition, QDs exhibited efficacy in the breakdown of PAHs. The analysis of their fragmentation suggests that the primary mechanism for PAHs degradation is the phthalic acid pathway.

Production of Glucoamylase from Novel Strain of Alternaria Alternata under Solid State Fermentation.

Glucoamylase has an essential role as biocatalyst in various important industries of Pakistan. It is synthesized by using various fungal and bacterial strains, and different ecocultural conditions are applied under solid substrate fermentation method (SSF) to get the highest yield of glucoamylase. Alternaria alternata is an important fungus that can grow on industrial raw material like wheat bran, dried potato powder, tea leaves, rice husk, and sugar cane peel which are used as substrate. Among all, dried potato powder (10g) proved the best fermentation media for growth of fungal strain as well as maximum glucoamylase producer. Moreover, several chemical and physical states were also explored through solid substrate fermentation technique on glucoamylase yield. The highest glucoamylase production was recorded after 72 hours incubation in incubation chamber with 10g raw substrate, 1ml inoculum spore solution, 30°C temperature, and 5 pH. Further, phosphate buffer (5 pH) as moistening agent, 5% starch concentration and media additive as nitrogen (yeast extract), and carbon source (maltose) were screened for maximum glucoamylase titer (17.3 ± 0.05a°U/ml/min) and the highest specific activity (39.2U/mg). These cultural conditions were most appropriate for growth of A. alternata on solid media and production of highest glucoamylase under solid state fermentation procedure that could be utilized for commercial synthesis of glucoamylase.

Exogenous melatonin mitigates chromium toxicity in maize seedlings by modulating antioxidant system and suppresses chromium uptake and oxidative stress.

Melatonin, being an endogenous signaling molecule plays important role in plant growth and stress alleviation. The present study was conducted to evaluate the ameliorative role of melatonin against Cr toxicity in maize seedlings. The Cr toxicity (50, 100 and 200 µM) severely affected hydroponically grown seedlings growth in a dose-dependent manner; however, the melatonin (0.5 and 1.0 µM) application markedly restored toxicity-induced growth retardation. Higher dose of melatonin (1.0 µM) was more effective in case of lower Cr toxicity (50 and 100 µM). Exposure of 200 µM Cr caused 45% and 43% reduction in shoot and root lengths and more than 80% reduction in biomass. In case of 200 µM Cr toxicity, application of 1.0 µM MT effectively restored shoot and root lengths reduction (from 45 to 30%) and biomass decline (from 80 to around 60%). Biomass restoration by 1.0 µM melatonin under 50 and 100 µM Cr was even more pronounced bringing it near to control plants having no Cr exposure. Further, both melatonin levels also improved root tips, root diameter, root volume and root surface area that had been damaged by Cr exposure. The melatonin also alleviated Cr-induced chlorophyll and carotenoids inhibition, improved relative water content, and markedly lowered proline and MDA content in shoots. Lower accumulation of MDA and proline, and greater membrane stability indices indicate that the melatonin conferred better plant growth by playing the role of antioxidant and detoxifying oxidative stress creating substances. Although antioxidant enzymes viz. SOD, POD, CAT and APX activities were also elevated by MT, this increase was not significantly different in the most of cases. No significant difference in NPK contents of shoot was observed by Cr and melatonin application indicating the growth retardation being caused directly by Cr intrinsic toxicity and not by nutrients deficiency. The melatonin-based amelioration of Cr toxicity in maize seedlings seems as the result of its nature as antioxidant, and not by activation/elevation of antioxidative enzymatic system.

Hexachlorocyclohexane toxicity in water bodies of Pakistan: challenges and possible reclamation technologies.

Pakistan is an agro-economy country where hexachlorocyclohexane (HCH) pesticides are being used to improve crop productivity, as a result the risk of contamination of soil and sediment has been increased. HCH exhibits all the characteristics of persistent organic pollutants (POP), and was therefore added to the list of 'new POPs' in 2009. This review report revealed that the major rivers of Pakistan such as the Indus Basin, River Ravi, River Chenab and their tributaries all are contaminated with HCH and the highest residual concentration (4,090 ng/g) was detected in a pesticide burial ground in Hyderabad city. Major sources of HCH contamination were identified as agricultural runoff, discharge of untreated industrial effluents and surface runoff. In order to manage HCH pollution, various ex-situ and in-situ remediation techniques along with their merits and demerits are thoroughly reviewed. Among these, microbial bioremediation is a low cost, environment friendly, effective in-situ remediation technique for remediation of HCH. Overall, the information provided in this manuscript will provide a future reference to the scientific community and bridge the knowledge gap between HCH release in the environment and their mitigation through proper treatment methods.

Health risk assessment of hexachlorocyclohexane in soil, water and plants in the agricultural area of Potohar region, Punjab, Pakistan.

In this study analysis of soil, water and plant residue samples is presented to evaluate the contamination levels and possible health risks. Hexachlorocyclohexane (HCH) is a persistent organic pollutant used as a pesticide in agricultural sector for pest control in order to obtain higher productivity. For analysis soil, water and crop residue samples were collected from different agricultural areas of the northern Punjab region of Pakistan. The investigation of the samples shows significant levels of HCH residues in all types of samples. Gas chromatography-mass spectrometry analysis was used to assess the higher residue levels of HCH in the samples. The concentration of HCH residues detected in samples ranged from 2.43 to 8.88 µg/g in soil, nd -5.87 µg/l in water and nd - 4.87 µg/g in plants. The presence of HCH residues in soil, water and plant samples was beyond the recommended quality guidelines. Human health risk was evaluated for cancer and non-cancer risks through dietary and non-dietary exposure routes. The hazard index was HI > 1 in children and HI < 1 in adults, while the non-dietary incremental lifetime cancer risks (ILCR) were beyond the internationally acceptable limit of 1 × 10-5. Hence, results of the present investigation concluded the presence of high levels of HCH residues in samples and pose high health risk to the inhabitants. These findings are alarming and apprise the concerned departments for the remediation of contamination and proper implementation of environmental laws in the area.

Ozone oxidation of wastewater containing trichlorobiphenyl and used transformer oil.

Trichlorobiphenyl (TCB) is a persistent toxic organic compound and exerts more hydrophilicity than other polychlorinated biphenyl (PCB) compounds. PCBs have been used on large scale in transformer oil. To observe the strong ozone oxidation effect on the degradation of TCB in aqueous medium, synthetic wastewater was prepared from transformer oil with TCB. Microbubbles ozonation of TCB was done in order to completely oxidize it. A batch treatment system was used for 60 min in glass column with a diffuser at the bottom to convert ozone gas into microbubbles. GCMS analyzed TCB and other toxic compounds before and after the treatment. TCB was reduced to below detection limit during the first 20 min of ozonation. Ethylbenzene and 1-chloroheptacosine were identified after 10 and 20 min, the concentrations of these compounds increased to 1.45 and 3.9 mg/L after 60 min. Alkane with chlorine containing compounds were identified more than any other compounds. The alkanes compounds with chlorine, such as tetradecane 1-chloro, hexadecane 1-chloro, heptadecane 1-chloro, octadecane 1-chloro and nonadecane 1-chloro were found during 60 min of ozonation. Chemical oxygen demand (COD) in the wastewater reduced from 700 to 390 mg/L. Small increase in pH was observed from 7.7 to 8.3. In this study it was concluded that TCB and other pollutants in transformer oil were degraded with ozone dose, 0.05 g/min L in the shortest period of 60 min.

Risk Assessment of Heavy Metals in Selected Marine Fish Species of Gadani Shipbreaking Area and Pakistan.

Gadani shipbreaking area, located on the coastline of Pakistan, is an important fish production area. In this study, levels of four metals (Ni, Pb, Cd, and Mn) in 148 muscle and gill samples of seven fish species (Small-scale terapon, Torpedo scade, Sicklefish, Saddle grunt, Gold silk seabream, Indian mackerel, Spotted sickle fish) and seawater samples, taken from 9 sampling sites in the shipbreaking area, were determined. In addition, multiple approaches were used to assess human health risks from fish consumption. Trace metal concentration in seawater ranged from 0.05 to 1.96 mg/L in shipbreaking vicinity and 0.03 to 0.97 mg/L in the reference site (Miani Hor). However, metal accumulations in fish species ranged from 1.33 to 5.26 µg/g. Among trace metals, the level of Pb in all fish species was highest, followed by Ni, Mn, and Cd. The bioaccumulation factors (BAFs) for both gills and muscles displayed the order: Mn > Cd > Ni > Pb. Estimated daily intake (EDI) values were below the tolerable daily intake (TDI). Based on target hazard quotient (THQ), the investigated fish species were safe regarding Pb and Mn (THQ < 1), while they may cause potential risk regarding Cd and Ni (THQ > 1). After comparison with maximum permissible limits, heavy metal concentration in the edible muscle tissues of all the analyzed fish species from the Gadani coast were found safe for human consumption.

Allium cepa assay based comparative study of selected vegetables and the chromosomal aberrations due to heavy metal accumulation.

Irrigation of industrial effluents may end in the bioaccumulation of various toxic metals and consequent genetic changes in contaminated food crops. To test this hypothesis and extent of genetic modifications, Allium cepa test was performed to food crops viz. tomato (Lycopersicum esculentum) and chili (Capsicum annum) as Allium cepa test is a useful tool to assess genetic variations in plants. Prior to A. cepa test, the plants were exposed to various metal concentrations 125-1000 mg/L in the synthetic wastewater. The extracts of harvested plants were used to grow the root of A. cepa following its standard method. The root tips were fixed, stained and examined under compound microscope (almost 300-400 dividing cells) to check the extent of chromosomal variations during various stages of mitosis. The results revealed various chromosomal abnormalities including laggards, stickiness, vagrant chromosomes, binucleated cells, nuclear lesions, giant cells and c-mitosis at different level of treatment. On the whole, aberrations were increasing with the increasing doses along the positive control. In comparison, chili crop had higher level of aberrations depicting the higher chromosomal changes. Lower mitotic index (MI) with increasing level of doses was also describing the hampered cell division due to increased metal stress. The study is showing that the cell division was ceased with increasing metal stress thus increasing the rate of cell aberrations.

Physiology and selected genes expression under cadmium stress in Arundo donax L.

The effects of cadmium stress (0, 25, 50, 75, and 100 mg/L) on morpho-physiological features and selected genes (carotenoid hydroxilase, amidase, GR, bHLH, NRAMP and YSL) expression were demonstrated in Arundo donax L. The plants were assessed for Cd uptake and its effects on chlorophyll and antioxidants after 30 days of exposure. The expression of genes conferring metal tolerance was evaluated after 10 days of Cd exposure. The results showed a maximum Cd uptake in roots (872 mg/kg) followed by stem (734 mg/kg) and leaves (298 mg/kg) at highest supplied Cd concentration. The Cd uptake reduced dry weight, Chla, Chlb, and total Chl contents of giant reed. The SOD, CAT, POD activities and MDA content increased at the maximum Cd concentration over control. The highest genes expression for carotenoid hydroxylase, glutathione reductase and amidase was observed in plants exposed to 100 mg/L. However, differential bHLH gene expression and slightly increased gene expression of NRAMP was noted for different Cd treatments. Amidase expressed under Cd stress which is pioneer report in A. donax. These results provided insights into the mechanisms of A. donax tolerance and survival under Cd Stress.

Physiological and antioxidant response of wheat (Triticum aestivum) seedlings to fluoroquinolone antibiotics.

Combinations of antibiotics occur in terrestrial environments due to excessive prescription, consumption, and disposal and have adverse effects, including crop toxicity. We examined short-term (20-d) toxicity of the fluoroquinolone antibiotics ciprofloxacin, enrofloxacin, levofloxacin, and their mixture in a germination and a greenhouse sand culture study with wheat. We tested the hypothesis that oxidative stress plays a role in toxicity by examining stress products and antioxidants involved in detoxifying reactive oxygen species (ROS) during stress. Germination was unaffected by any antibiotic concentration or mixture used. The highest antibiotic concentrations, 100 and 300 mg L-1, significantly decreased wheat growth. In 20 days exposure the maximum malondialdehyde production (2.45 µmol g-1 fresh weight), total phenols (16.40 mg g-1 of extract), and total antioxidant capacity (17.74 mg of Vitamin C g-1 of extract) and maximum activities of superoxide dismutase (7.99 units mg-1 protein min-1) and ascorbate peroxidase (0.69 µmol ascorbate mg-1 protein min-1) significantly increased compared to the control. In contrast, catalase (0.45 mmol H2O2 mg-1 protein min-1) and peroxidase (0.0005 units mg-1 protein min-1) activity significantly decreased compared to the control. We conclude that high antibiotic concentrations in the plant growth medium reduced wheat growth by causing oxidative stress. The capacity to respond to oxidative stress was compromised by increasingly higher antibiotic concentrations in some enzyme systems. This stress damaged the physiological structure of the young plants and could reduce crop productivity in the long term. Consequently, fluoroquinolone-contaminated water challenges developing countries with constraints on available water for irrigation.