Atrazine and simazine degradation in Pennisetum rhizosphere

The ability of rhizosphere of four plant species to promote the degradation of charcoal-fixed atrazine and simazine in cement blocks of a long-term contaminated soil when mixed with a normal soil at 1:1 ratio was tested. Of the four selected plants viz., rye grass (Lolium perenne), tall fescue (Festuca arundinacae), Pennisetum (Pennisetum clandestinum) and a spring onion (Allium sp.) used in this study, only P. clandestinum was able to survive in herbicide contaminated soil while other plants died within few days after germination/transplanting. Both atrazine and simazine were degraded at a faster rate in contaminated soil planted to P. clandestinum than in unplanted soil. Within 80 days, nearly 45% and 52% of atrazine and simazine, respectively, were degraded in soil planted to P. clandestinum while only 22% and 20% of the respective herbicide were degraded in the unplanted soil. During 80-day experimental period, both microbial biomass and soil dehydrogenase activity were significantly increased (7-fold) in soil planted to P. clandestinum over that in unplanted soil. The suspension of contaminated rhizosphere soil, planted to P. clandestinum exhibited an exceptional capability to degrade both atrazine (300 microg) and simazine (50 microg) in a mineral salts medium over that of non-rhizosphere soil suspension. Results indicate that P. clandestinum, a C4 plant, may be useful for remediation of soils contaminated with atrazine and simazine.     

Size-resolved effective density of submicron particles during summertime in the rural atmosphere of Beijing, China

Particle density is an important physical property of atmospheric particles.The information on high time-resolution size-resolved particle density is essential for understanding the atmospheric physical and chemical aging processes of aerosols particles.In the present study,a centrifugal particle mass analyzer(CPMA) combined with a differential mobility analyzer(DMA) was deployed to determine the size-resolved effective density of 50 to 350 nm particles at a rural site of Beijing during summer 2016.The measured particle effective densities decreased with increasing particle sizes and ranged from 1.43 to 1.55 g/cm~3,on average.The effective particle density distributions were dominated by a mode peaked at around 1.5 g/cm~3 for 50 to350 nm particles.Extra modes with peaks at 1.0,0.8,and 0.6 g/cm3 for 150,240,and 350 nm particles,which might be freshly emitted soot particles,were observed during intensive primary emissions episodes.The particle effective densities showed a diurnal variation pattern,with higher values during daytime.A case study showed that the effective density of Aitken mode particles during the new particle formation(NPF) event decreased considerably,indicating the significant contribution of organics to new particle growth.     

Scattering cross-section emission factors for visibility and radiative transfer applications: military vehicles traveling on unpaved roads

Emission factors for particulate matter (PM) are generally reported as mass emission factors (PM mass emitted per time or activity) as appropriate for air quality standards based on mass concentration. However, for visibility and radiative transfer applications, scattering, absorption, and extinction coefficients are the parameters of interest, with visibility standards based on extinction coefficients. These coefficients (dimension of inverse distance) equal cross-section concentrations, and, therefore, cross-section emission factors are appropriate. Scattering cross-section emission factors were determined for dust entrainment by nine vehicles, ranging from light passenger vehicles to heavy military vehicles, traveling on an unpaved road. Each vehicle made multiple passes at multiple speeds while scattering and absorption coefficients, wind velocity and dust plume profiles, and additional parameters were measured downwind of the road. Light absorption of the entrained PM was negligible, and the light extinction was primarily caused by scattering. The resulting scattering cross-section emission factors per vehicle kilometer traveled (vkt) range from 12.5 m2/vkt for a slow (16 km/ hr), light (1176 kg) vehicle to 3724 m2/vkt for a fast (64 km/hr), heavy (17,727 kg) vehicle and generally increase with vehicle speed and mass. The increase is approximately linear with speed, yielding emission factors per vkt and speed ranging from 4.2 m2/(vkt km/hr) to 53 m2/(vkt km/hr). These emission factors depend approximately linearly on vehicle mass within the groups of light (vehicle mass < or =3100 kg) and heavy (vehicle mass >8000 kg) vehicles yielding emission factors per vkt, speed, and mass of 0.0056 m2/(vkt km/hr kg) and 0.0024 m2/(vkt km/hr kg), respectively. Comparison of the scattering cross-section and PM mass emission factors yields average mass scattering efficiencies of 1.5 m2/g for the light vehicles and of 0.8 m2/g for the heavy vehicles indicating that the heavy vehicles entrain larger particles than the light vehicles.     

Spatial distribution of fossil fuel derived CO2 over India using radiocarbon measurements in crop plants

Examining the contribution of fossil fuel CO₂to the total CO₂changes in the atmosphere is of primary concern due to its alarming levels of fossil fuel emissions over the globe,specifi cally developing countries.Atmospheric radiocarbon represents an important observationa constraint and utilized to trace fossil fuel derived CO₂(CO_2ff) in the atmosphere.For the firs time,we have presented a detailed analysis on the spatial distribution of fossil fuel der...     

Improving the dynamic response of frequency and power in a wind integrated power system by optimal design of compensated superconducting magnetic energy storage

The frequency deviation and power fluctuation need to be controlled in a wind-integrated power system (WIPS) for keeping the balance between system power generation and demand, which support the quality and stability of overall power system. The present paper addresses this problem while concerning the integration of intermittent wind power and load disturbance into the WIPS. With this intent, it proposes the compensated superconducting magnetic energy storage (CSMES) system with proportional integral derivative (PID) controller for improving the frequency and power deviation profile. A novel swarm intelligence-based artificial bee colony (ABC) algorithm is used for optimal design of PID-CSMES system. Robustness of the proposed ABC-based PID-CSMES control strategy is tested in WIPS under various disturbance patterns of load and wind power. To demonstrate the improved dynamic response, their simulation results are compared with particle swarm optimization-based PID-CSMES, PID with SMES, and only PID controller technique. The performance indices and transient response characteristics of frequency and power deviation are used to evaluate and compare the accuracy and efficiency of each controller. Stability of various system configurations is analyzed using eigenvalue location. Comparing the results of different controller in WIPS indicates a substantial improvement in the dynamic response of system frequency and power deviations by utilizing the proposed control strategy.     

Hidden values in bauxite residue (red mud): Recovery of metals

Bauxite residue (red mud) is a hazardous waste generated from alumina refining industries. Unless managed properly, red mud poses significant risks to the local environment due to its extreme alkalinity and its potential impacts on surface and ground water quality. The ever-increasing generation of red mud poses significant challenges to the aluminium industries from management perspectives given the low proportion that are currently being utilized beneficially. Red mud, in most cases, contains elevated concentrations of iron in addition to aluminium, titanium, sodium and valuable rare earth elements. Given the scarcity of iron supply globally, the iron content of red mud has attracted increasing research interest. This paper presents a critical overview of the current techniques employed for iron recovery from red mud. Information on the recovery of other valuable metals is also reviewed to provide an insight into the full potential usage of red mud as an economic resource rather than a waste. Traditional hydrometallurgy and pyrometallurgy are being investigated continuously. However, in this review several new techniques are introduced that consider the process of iron recovery from red mud. An integrated process which can achieve multiple additional values from red mud is much preferred over the single process methods. The information provided here should help to improve the future management and utilization of red mud.     

Investigating mechanical properties and durability of concrete containing recycled rubber ash and fibers

This article investigates the suitability of utilizing end of life rubber tyre particles in concrete as fine aggregate. Rubber ash and rubber fibers were used to develop two series of rubber ash concrete (series I) and hybrid concrete (series II) mixes. The natural fine aggregate was replaced by rubber ash (by volume of 5%, 10%, 15% and 20%) in series I; whereas in series II, the amount of rubber ash was kept constant at 10% and rubber fiber was introduced as replacement of fine aggregate (by volume of 5%, 10%, 15%, 20% and 25%). The concrete mixes were evaluated for compressive strength, flexural strength, resistance to impact loading, fatigue loading, water penetration and shrinkage strain was evaluated. It was observed that inclusion of rubber ash resulted in the improvement of impact resistance of concrete. The results also show that up to 10% rubber ash and rubber fibers can be utilized as fine aggregate to develop feasible and durable rubberized concrete pavements, crash barriers and paver blocks.

     

Effect of industrial waste products on phosphorus mobilisation and biomass production in abattoir wastewater irrigated soil

This study evaluated the effect of alkaline industrial by-products such as flyash (FA) and redmud (RM) on phosphorus (P) mobilisation in abattoir wastewater irrigated soils, using incubation, leaching and plant growth (Napier grass [Pennisetum purpureum]) experiments. The soil outside the wastewater irrigated area was also collected and treated with inorganic (KH₂PO₄ [PP]) and organic (poultry manure [PM]) P treatments, to study the effect of FA and RM on P mobilisation using plant growth experiment. Among the amendments, FA showed the highest increase in Olsen P, oxalic acid content and phosphatase activity. The highest increase in Olsen P for PM treated non-irrigated soils showed the ability of FA and RM in mobilising organic P better than inorganic P (PP). There was over 85 % increase in oxalic acid content in the plant growth soils compared to the incubated soil, showing the effect of Napier grass in the exudation of oxalic acid. Both amendments (FA and RM) showed an increase in phosphatase activity at over 90 % at the end of the 5-week incubation period. The leaching experiment indicated a decrease in water soluble P thereby ensuring the role of FA and RM in minimising P loss to water bodies. FA and RM showed an increase in plant biomass for all treatments, where FA amended soil showed the highest increase as evident from FA’s effect on Olsen P. Therefore, the use of FA and RM mobilised P in abattoir wastewater irrigated soils and increased biomass production of Napier grass plants through root exudation of oxalic acid.