Role of plant growth promoting rhizobacteria in the remediation of metal contaminated soils

Pollution of the biosphere by the toxic metals is a global threat that has accelerated dramatically since the beginning of industrial revolution. The primary source of this pollution includes the industrial operations such as mining, smelting, metal forging, combustion of fossil fuels and sewage sludge application in agronomic practices. The metals released from these sources accumulate in soil and in turn, adversely affect the microbial population density and physico-chemical properties of soils, leading to the loss of soil fertility and yield of crops. The heavy metals in general cannot be biologically degraded to more or less toxic products and hence, persist in the environment. Conventional methods used for metal detoxification produce large quantities of toxic products and are cost-effective. The advent of bioremediation technology has provided an alternative to conventional methods for remediating the metal-poisoned soils. In metal-contaminated soils, the natural role of metal-tolerant plant growth promoting rhizobacteria in maintaining soil fertility is more important than in conventional agriculture, where greater use of agrochemicals minimize their significance. Besides their role in metal detoxification/removal, rhizobacteria also promote the growth of plants by other mechanisms such as production of growth promoting substances and siderophores. Phytoremediation is another emerging low-cost in situ technology employed to remove pollutants from the contaminated soils. The efficiency of phytoremediation can be enhanced by the judicious and careful application of appropriate heavy-metal tolerant, plant growth promoting rhizobacteria including symbiotic nitrogen-fixing organisms. This review presents the results of studies on the recent developments in the utilization of plant growth promoting rhizobacteria for direct application in soils contaminated with heavy metals under a wide range of agro-ecological conditions with a view to restore contaminated soils and consequently, promote crop productivity in metal-polluted soils across the globe and their significance in phytoremediation.     

Ozonation catalyzed by homogeneous and heterogeneous catalysts for degradation of DEHP in aqueous phase

Di-(2-ethyl hexyl) phthalate (DEHP), a recalcitrant and an endocrine disrupting chemical, was studied for its removal from wastewater by advanced oxidation process. The effects of pH, transition metal ions, and granular activated carbon (GAC) were investigated. Removal of DEHP increased with increase in pH and among metal ions Cr(III) was found to be the most active catalyst to remove DEHP. In the case of GAC, original carbon (G0) and GAC pre-ozonated in gas phase for 10 min (G10) were tested as catalysts in catalytic ozonation and found G0 to be more active than G10. This is because, during pre-ozonation, basic groups like chromene, pyrones and also graphene layers were oxidized to acidic surface oxygen groups. These basic surface groups are reported to be active catalytic centres for ozone decomposition into .OH which is a strong oxidant. According to kinetic manipulations, DEHP degradation rate constant due to .OH was affected by the catalyst while that due to direct ozonation is same in all cases with or without catalyst. G0 was doped with chromia gels (G0/CrA) to combine the benefits of homogeneous and heterogeneous catalysis. G0/CrA showed lower catalytic efficiency than that of only G0. This might be because of changes in surface structure of GAC caused by doping of chromia gel and changes in chemical nature of Cr(III) during formation of gel. A good correlation was found between the rate constants of ozone decay and DEHP degradation (R2=0.96). This correlation confirms that ozone decomposition into .OH is a critical factor for the activity of a catalyst during ozonation.     

Violence breeds violence: burnout as a mediator between patient violence and nurse violence

The present study examines whether patient-perpetrated violence triggers anger, hatred and other negative emotions that, under certain circumstances, might motivate nurses to behave violently with patients. In doing so, this study considers burnout as a mediator in the patient violence–nurse violence relationship. To test the causal paths, data were collected from 182 nurses working in two government-sector teaching hospitals of Pakistan's Punjab province. Results confirm that patient violence toward nurses leads to nurse violence toward patients through the mediating effect of burnout. The study advises hospitals to provide wellness and stress management programs to nurses who regularly experience events involving patient violence. Hospitals may consider allowing nurses to take short breaks after an encounter with violently behaving patients. In addition, hospitals should conduct empathy-promoting training, emotional intelligence training and ‘lens of the patient’ training programs to sensitize their nursing staff.     

Association between meteorological indicators and COVID-19 pandemic in Pakistan

Environmental Science and Pollution Research - This study was designed to investigate the impact of meteorological indicators (temperature, rainfall, and humidity) on total COVID-19 cases in...     

Monitoring of bacterial morphology for controlling filamentous overgrowth in an ultracompact biofilm reactor.

This research was part of a study of filamentous growth and control in an ultracompact biofilm reactor (UCBR). Morphologies of biofilm and filamentous bacteria in the UCBR were investigated. Ethanol was used as a substrate and sodium hypochlorite was applied as a toxicant to control filamentous growth. The results indicated that factors such as chemical oxygen demand, surface loading rate, pH, and dissolved oxygen could initiate filamentous overgrowth in the UCBR. Different biofilm and filamentous morphologies in the UCBR were observed under different operational conditions. Chlorination was an effective approach to control filamentous growth during and after biofilm formation. Proper chlorine dosing had no effect on biofilm, but killed filaments. Overdose of chlorine damaged biofilm and caused adverse effects such as low treatment efficiency, media clogging and washout, and biofilm color change in the reactor. Frequent monitoring of the morphologies of filaments and biofilm was needed during chlorination to prevent chlorine overdose.     

Composite indicators for famine early warning systems

Traditional famine early warning systems use a host of indicators to predict food crisis situations, from rainfall and increased rate of marketing of household durables to the behavior of birds and animals. Although many of these indicators are valid in general, limited understanding of the sensitivity and specificity of the distress signals makes food crisis prediction a highly subjective exercise. In order to make the system more effective and credible, we need to identify a limited number of 'composite' indicators, which naturally summarize most relevant food-related information contained in the specific predictors of food crisis. Considering the chronology of the food production and consumption chain, three composite indicators specific to three different stages of the chain have been identified. The satellite data based Normalized Deviation of Vegetative Index (NDVI), prices of major food grains, and malnutrition rates are found to be correlated not only with the quality and quantity of inputs of this process but also with the final outcome. Both NDVI and price data are widely used as important predictors of food crisis by famine warning systems. What we have demonstrated is that improved sensitivity of the indicators is likely to be due to their inherent capability of summarizing information from various specific measures. Child malnutrition rates also summarize inputs and outputs of the food consumption process very effectively, and therefore should be able to predict community level food crisis in an efficient manner. The empirical results confirm this conjecture by showing that malnutrition rates can predict food crisis probability three months into the future with a high degree of specificity. The use of 'composite' indicators not only simplifies the problem of aggregation, but is also likely to yield forecasts that are highly specific and sensitive.     

Identification of erosion-prone areas using morphometric parameters,land use land cover and multi-criteria decision-making method: geo-informatics approach

Environment, Development and Sustainability - Soil erosion is the main driving force of several devastating natural hazards in the complex mountainous terrain of the Himalayas where the Teesta...     

Depth as a factor in abundance and size of juvenile penaeid shrimps in the absence of estuaries and marshes

Triweekly trawling around low tide during daylight at 1, 2, 3, and 4 m depths along north Kuwait Bay's extensive intertidal mudflats from 1 April 1985 through 9 December 1986 showed the catchability ofMetapenaeus affinis (H. Milne-Edwards, 1837),M. stebbingi Nobili, 1904,Parapenaeopsis stylifera (H. Milne-Edwards, 1837), andPenaeus semisulcatus De Haan, 1844 differed significantly with depth and season. All species were significantly more catchable in 1 and 2 m depths than in 3 and 4 m depths.M. affinis showed the clearest and most consistent relationship with depth: catchability in 1 m depths was significantly greater than that in 2 m depths (24.9 vs 5.4 per 5-min tow), and catchability in 1 and 2 m depths was significantly greater than that in 3 and 4 m depths (15.2 vs 1.4 per 5-min tow).M. affinis also showed the clearest relationship of increasing size with depth. Shrimp captured in 1 m depths were significantly smaller (~ 14 mm carapace length, CL) than those captured in 2 m depths in the spring (~23 mm CL) and summer (~ 18 mm CL). In the absence of low-salinity waters and intertidal vegetation, it is believed that the edge of the advancing and receding tide over the mudflats, i.e. the shallowest waters, provides juvenile shrimp, particularlyM. affinis, protection from predation.     

Effects of phosphorothionate on the reproductive system of male rats

Acute and Sub-acute toxic effects of a new pesticide phosphorothionate coded as RPR-V on testis of albino rat were studied. For the acute study, rats received a single dose of 30 mg/kg of RPR-V and sacrificed after 24 hours. For the Subacute study, 1.42 mg/kg/day was administered orally to rats for 10 days and 21 days. Acute exposure of rats to RPR-V brought no change either in the Gonadosomatic Index (GSI) or in the structure of testis or in the serum levels of Testosterone. Similarly, no significant change was observed in the Glutathione S-transferase (GST) activity. But, in testis there was significant increased in the reduced Glutathione (GSH) and Acid Phosphatase (AcP), whereas Alkaline Phosphatase (AkP) levels decreased significantly at 24hr post treatment. On 7th day (withdrawal period) after the cessation of the treatment the GSH, AcP, and AkP levels reached to near control. The sub-acute study revealed a significant post treatment. Due to RPR-V treatment the testis AcP levels increased significantly at 21st day of medication but AkP levels decreased both at 10th and 21st day of post treatment. Histopathological studies showed that after 10th day testis showed considerable loss of spermatozoids and at 21st day complete derangement of cellular organization was observed. Testosterone levels decreased significantly after 10th day and remained significantly low at 21st day. However, withdrawal studies showed a recovery in testis of rat treated with RPR-V. GST, GSH, GSI, AcP and AkP values were recovered, testosterone levels were also recovered but recovery in testis structure remained at a low profile.     

An alternative to additional SO3 injection for fly ash conditioning

Small concentrations, approximately 2-10 parts per million (ppm), of injected sulfur trioxide (SO3) have improved particulate collection efficiencies of electrostatic precipitators burning lower-sulfur coal. However, the addition of extra SO3 not only incurs costs but also presents negative environmental effects. This work explored a method that could be applied to existing coal-fired power plants to convert the sulfur dioxide (SO2) already present in the flue gas to sufficient levels of SO3 for fly ash conditioning as an alternative to adding SO3 by burning elemental sulfur. During this research, a pre-mixed natural gas flame was used to promote the conversion of SO2 to SO3 in a drop-tube furnace with average non-flame, free stream gas temperatures of 450 and 1000 K. SO3 concentrations measured by wet chemistry and confirmed using elemental balances of other sulfur species measured by gas chromatography revealed that as much as 7% of SO2 was homogeneously transformed to SO3. The results also showed that at low temperatures, the rate at which SO3 is converted back to SO2 decreased, thus extending the time period during which SO3 concentrations would be sufficient for ash conditioning. An additional benefit of this technique is speculated to result from increased flue gas humidity.