A lagrangian approach to analyse the tropospheric ozone climatology in the tropics: Climatology of stratosphere–troposphere exchange at Reunion Island

Sixteen years of ozone measurements (1992–2006) at Reunion Island (21°S, 55.5°E) have been processed to detect stratospheric signatures on each single ozone profile.The characterisation method consists in the advection of the potential vorticity (PV) over two to ten days of backtrajectory with the lagrangian trajectory code LACYTRAJ. LACYTRAJ is a Trajectory-Reverse Domain Filling code using the ERA40 ECMWF database and allowing the reconstruction of high resolution advected PV profiles. Correlation between high values of ozone mixing ratio and high PV is interpreted as a stratospheric signature.A climatology of STE events at Reunion has been derived and reveals that STE events occur more frequently during spring (SON) and summer (DJF). The method is tested for a set of PV threshold values (i.e. 1 PVU, 1.5 PVU and 2 PVU) and for a set of duration of backtrajectories (i.e. 2 days, 5 days and 10 days). The number of detected STE is sensitive to PV threshold values and duration criterions. For instance, the number of stratospheric intrusions detected in October with a 1.5 PVU criterion ranges between 25% (2 days of backtrajectories) and 56% (10 days of backtrajectories). The vertical distributions of STE show intrusions covering the whole free troposphere (between 7 and 15 km) and mainly located in the upper troposphere.Finally, results show that an important number of stratospheric intrusions are detected during spring and in the upper troposphere what points at the contribution of the stratospheric source to the tropospheric ozone spring maximum which is strongly influenced by the biomass burning emissions from South Africa and Madagascar.     

The impact of photovoltaic (PV) installations on downwind particulate matter concentrations: Results from field observations at a 550-MWAC utility-scale PV plant

With utility-scale photovoltaic (PV) projects increasingly developed in dry and dust-prone geographies with high solar insolation, there is a critical need to analyze the impacts of PV installations on the resulting particulate matter (PM) concentrations, which have environmental and health impacts. This study is the first to quantify the impact of a utility-scale PV plant on PM concentrations downwind of the project site. Background, construction, and post-construction PM_2.5 and PM₁₀ (PM with aerodynamic diameters <2.5 and <10 μm, respectively) concentration data were collected from four beta attenuation monitor (BAM) stations over 3 yr. Based on these data, the authors evaluate the hypothesis that PM emissions from land occupied by a utility-scale PV installation are reduced after project construction through a wind-shielding effect. The results show that the (1) confidence intervals of the mean PM concentrations during construction overlap with or are lower than background concentrations for three of the four BAM stations; and (2) post-construction PM_2.5 and PM₁₀ concentrations downwind of the PV installation are significantly lower than the background concentrations at three of the four BAM stations. At the fourth BAM station, downwind post-construction PM_2.5 and PM₁₀ concentrations increased marginally by 5.7% and 2.6% of the 24-hr ambient air quality standards defined by the U.S. Environmental Protection Agency, respectively, when compared with background concentrations, with the PM_2.5 increase being statistically insignificant. This increase may be due to vehicular emissions from an access road near the southwest corner of the site or a drainage berm near the south station. The findings demonstrate the overall environmental benefit of downwind PM emission abatement from a utility-scale PV installation in desert conditions due to wind shielding. With PM emission reductions observed within 10 months of completion of construction, post-construction monitoring of downwind PM levels may be reduced to a 1-yr period for other projects with similar soil and weather conditions.

Implications: This study is the first to analyze impact of a utility photovoltaic (PV) project on downwind particulate matter (PM) concentration in desert conditions. The PM data were collected at four beta attenuation monitor stations over a 3-yr period. The post-construction PM concentrations are lower than background concentrations at three of four stations, therefore supporting the hypothesis of post-construction wind shielding from PV installations. With PM emission reductions observed within 10 months of completion of construction, postconstruction monitoring of downwind PM levels may be reduced to a 1-yr period for other PV projects with similar soil and weather conditions.     

Recovering valuable metals from recycled photovoltaic modules

Recovering valuable metals such as Si, Ag, Cu, and Al has become a pressing issue as end-of-life photovoltaic modules need to be recycled in the near future to meet legislative requirements in most countries. Of major interest is the recovery and recycling of high-purity silicon (>99.9%) for the production of wafers and semiconductors. The value of Si in crystalline-type photovoltaic modules is estimated to be ?$95/kW at the 2012 metal price. At the current installed capacity of 30 GW/yr, the metal value in the PV modules represents valuable resources that should be recovered in the future. The recycling of end-of-life photovoltaic modules would supply >88,000 and 207,000 tpa Si by 2040 and 2050, respectively. This represents more than 50% of the required Si for module fabrication. Experimental testwork on crystalline Si modules could recover a >99.98%-grade Si product by HNO₃/NaOH leaching to remove Al, Ag, and Ti and other metal ions from the doped Si. A further pyrometallurgical smelting at 1520ºC using CaO–CaF₂–SiO₂ slag mixture to scavenge the residual metals after acid leaching could finally produce >99.998%-grade Si. A process based on HNO₃/NaOH leaching and subsequent smelting is proposed for recycling Si from rejected or recycled photovoltaic modules.

Implications:The photovoltaic industry is considering options of recycling PV modules to recover metals such as Si, Ag, Cu, Al, and others used in the manufacturing of the PV cells. This is to retain its “green” image and to comply with current legislations in several countries. An evaluation of potential resources made available from PV wastes and the technologies used for processing these materials is therefore of significant importance to the industry. Of interest are the costs of processing and the potential revenues gained from recycling, which should determine the viability of economic recycling of PV modules in the future.     

Industrial Internet of things-based solar photo voltaic cell waste management in next generation industries

Environmental Science and Pollution Research - Nowadays, modern industries generate their energy by using renewable solar. The rapid increase in photovoltaic (PV) module installations provides a...     

Experimental in situ chemical peroxidation of atrazine in contaminated soil

Lab-scale experiments of in situ chemical oxidation (ISCO), were performed on soil contaminated with 100 mg kg(-1) of atrazine (CIET). The oxidant used was hydrogen peroxide catalysed by naturally occurring minerals or by soluble Fe(II) sulphate, added in aqueous solution. The oxidation conditions were: CIET:H2O2=1:1100, 2 PV or 3 PV reaction volume, Fe(II):H2O2=0, 1:22, 1:11. Stabilized (with KH2PO4 at a concentration of 16 g l(-1)) or non-stabilized hydrogen peroxide was used. The pH of the reagents was adjusted to pH=1 with sulphuric acid, or was not altered. Results showed that the addition of soluble Fe(II) increased the temperature of the soil slurry and the use of stabilized hydrogen peroxide resulted in a lower heat generation. The treatment reduced the COD of the soil of about 40%, pH was lowered and natural organic matter became less hydrophobic. The highest atrazine conversion (89%) was obtained in the conditions: 3 PV, Fe(II):H2O2=1:11 with stabilized hydrogen peroxide added in two steps. The stabilizer only increased H2O2 life-time significantly when soluble Fe(II) was added. Results indicate as preferential degradation pathway of atrazine in soil dechlorination instead of dealkylation.     

利用太阳能驱动的一体化氧化沟的运行方式

污水处理的高能耗和新能源利用已引起人们的关注,本文根据太阳光照强度的周期变化和农村污水昼夜排放量悬殊的特征,提出了一种新型的利用无蓄电池太阳能光伏系统驱动的污水生物处理系统,可有效降低太阳能光伏系统的成本。生物反应器是一个双沟式一体化氧化沟。按照启动的用电设备的数量,一体化氧化沟具有5种运行方式。在不同的运行方式下,一体化氧化沟的内沟和外沟具有不同的功能,其中运行方式3到运行方式5对污染物去除效率最高。采用阶梯型电量输出模式,可以充分利用太阳能,并保障一体化氧化沟的高效运行时间。在160 d的连续运行实验中,COD、氨氮、总氮和总磷的平均去除率分别为87.8%、98.4%、68.7%和80.3%。证明无蓄电池太阳能光伏系统驱动污水生物反应器处理农村分散污水是可行的。     

Effects of initial saturation on properties modification and displacement of tetrachloroethene with aqueous isobutanol

Packed column experiments were conducted to study effects of initial saturation of tetrachloroethene (PCE) in the range of 1.0-14% pore volume (PV) on mobilization and downward migration of the non-aqueous phase liquid (NAPL) product upon contact with aqueous isobutanol ( approximately 10 vol.%). This study focused on the consequences of swelling beyond residual saturation. Columns were packed with mixtures of neat PCE, water and glass beads and waterflooded to establish a desired homogeneous residual saturation, and then flooded with aqueous isobutanol under controlled hydraulic conditions. Results showed a critical saturation of approximately 8% PV for these packed column experimental conditions. At low initial PCE saturations (<8% PV), experimental results showed reduced risk of NAPL-product migration upon contact with aqueous isobutanol. At higher initial PCE saturations (>8% PV), results showed NAPL-product mobilization and downward migration which was attributed to interfacial tension (IFT) reduction, swelling of the NAPL-product, and reduced density modification. Packed column results were compared with good agreement to theoretical predictions of NAPL-product mobilization using the total trapping number, N(T). In addition to the packed column study, preliminary batch experiments were conducted to study the effects of PCE volumetric fraction in the range of 0.5-20% on density, viscosity, and IFT modification as a function of time following contact with aqueous isobutanol ( approximately 10 vol.%). Modified NAPL-product fluid properties approached equilibrium within approximately 2 h of contact for density and viscosity. IFT reduction occurred immediately as expected. Measured fluid properties were compared with good agreement to theoretical equilibrium predictions based on UNIQUAC. Overall, this study demonstrates the importance of initial DNAPL saturation, and the associated risk of downward NAPL-product migration, in applying alcohol flooding for remediation of DNAPL contaminated ground water sites.     

Operating temperature prediction and comparison for rooftop PV arrays in coastal climates of India

Environmental Science and Pollution Research - This article predicts the operational temperature of a 1-MWp rooftop photovoltaic (PV) system installed on buildings of GITAM University, Andhra...     

Review of cooling techniques used to enhance the efficiency of photovoltaic power systems

Environmental Science and Pollution Research - Photovoltaic (PV) panels are one of the most important solar energy sources used to convert the sun’s radiation falling on them into electrical...     

Review on the progress of building-applied/integrated photovoltaic system

Environmental Science and Pollution Research - Integration of photovoltaic (PV) technologies with building envelopes started in the early 1990 to meet the building energy demand and shave the peak...     

An analysis of the dust deposition on solar photovoltaic modules

Environmental Science and Pollution Research - Solid particles impair the performance of the photovoltaic (PV) modules. This results in power losses which lower the efficiency of the system as well...     

A comparison of dust impacts on polycrystalline and monocrystalline solar photovoltaic performance: an outdoor experimental study

Environmental Science and Pollution Research - Solar cells are considered one of the most important and widespread solar applications in the world. However, the performance of the PV modules is...     

Design of optimized PI controller for 7-level inverter: a new control strategy

Photovoltaic (PV) system produces electricity that differs from variations in environmental parameters such as temperature and solar radiation. The PV network will operate at maximum power point (MPP) and deal with an ever-increasing energy demand, that changes from both load and weather conditions.” Moreover, energy storage devices could be a potential solution for improving the efficiency and performance of renewable energy sources (RES). This paper intends to establish a control design by an optimization-assisted PI controller for a 7-level inverter. Accordingly, the gains of PI controller are adjusted dynamically by FireFly Integrated-Sea Lion Optimization algorithm (FFI-SLnO) that integrates the concepts of both Sea Lion Optimization (SLnO) and FireFly algorithm (FF). The gains should be tuned such that the error among the reference signal and fault signal should be low and hence better dynamic performance can be obtained by the presented optimized PI controller. Finally, the performance of the proposed method is compared over other traditional models with respect to certain measures and its superiority is proved.

     

Co-surfactant of ethoxylated sorbitan ester and sorbitan monooleate for enhanced flushing of tetrachloroethylene

This work evaluated the flushing efficiency of tetrachloroethylene (PCE) using the co-surfactant of non-ionic ethoxylated sorbitan ester (Tween) and oilphilic sorbitan monooleate (Span 80), which formed more hydrophobic micelles than Tween alone. The flushing efficiency was evaluated with laboratory columns filled with silica and aquifer sand. Results from column flushing were also compared to those of batch solubility experiments to study the removal mechanism by the co-surfactant solution. Compared to Tween 80 alone, the molar solubilization ratio and the affinity between the micelles and PCE increased 84% and 90%, respectively, by the co-surfactant solution of Tween 80 and Span 80 mixed at a 4:1 ratio. Flushing with 1% Tween 80 solution yielded a steady PCE recovery of 7% for both silica and aquifer sand in each pore volume (PV). Flushing with co-surfactant of 1% Tween 80 + Span 80 (4:1) further increased PCE recovery to 10% for silica sand and 13% for aquifer sand per PV. A comparison of results from column flushing and batch solubility tests indicated that the primary flushing mechanism of PCE using the co-surfactant solution of Tween 80 + Span 80 (4:1) was micellar solubilization.     

Potential assessment of establishing a renewable energy plant in a rural agricultural area

An evaluation of the green energy potential generated from biogas and solar power, using agricultural manure waste and a photovoltaic (PV) system, was conducted in a large geographical area of a rural county with low population density and low pollution. The studied area, Shoufeng Township in Hualien County, is located in eastern Taiwan, where a large amount of manure waste is generated from pig farms that are scattered throughout the county. The objective of the study is to assess the possibility of establishing an integrated manure waste treatment plant by using the generated biogas incorporated with the PV system to produce renewable energy and then feed it back to the incorporated farms. A filed investigation, geographic information system (GIS) application, empirical equations development, and RETScreen modeling were conducted in the study. The results indicate that Shoufeng Township has the highest priority in setting up an integrated treatment and renewable energy plant by using GIS mapping within a 10-km radius of the transportation range. Two scenarios were plotted in assessing the renewable energy plant and the estimated electricity generation, plus the greenhouse gas (GHG) reduction was evaluated. Under the current governmental green energy scheme and from a long-term perspective, the assessment shows great potential in establishing the plant, especially in reducing environmental pollution problems, waste treatment, and developing suitable renewable energy.     

Atrazine removal in agricultural infiltrate by bioaugmented polyvinyl alcohol immobilized and free Agrobacterium radiobacter J14a: a sand column study

Bench-scale sand column breakthrough experiments were conducted to examine atrazine removal in agricultural infiltrate by Agrobacterium radiobacter J14a (J14a) immobilized in phosphorylated-polyvinyl alcohol compared to free J14a cells. The effects of cell loading and infiltration rate on atrazine degradation and the loss of J14a were investigated. Four sets of experiments, (i) tracers, (ii) immobilized dead cells, (iii) immobilized cells, and (iv) free cells, were performed. The atrazine biodegradation at the cell loadings of 300, 600, and 900 mg dry cells L(-1) and the infiltration rates of 1, 3, and 6 cm d(-1) were tested for 5 column pore volumes (PV). The atrazine breakthrough results indicated that the immobilized dead cells significantly retarded atrazine transport. The atrazine removal efficiencies at the infiltration rates of 1, 3, and 6 cm d(-1) were 100%, 80-97%, and 50-70%, respectively. Atrazine degradation capacity for the immobilized cells was not significantly different from the free cells. Both infiltration rate and cell loading significantly affected atrazine removal for both cell systems. The bacterial loss from the immobilized cell system was 10-100 times less than that from the free cell system. For long-term tests at 50 PV, the immobilized cell system provided consistent atrazine removal efficiency while the atrazine removal by the free cells declined gradually because of the cell loss.     

Evaluation of soil flushing potential for clean-up of desert soil contaminated by industrial wastewater

The flushing potential of a desert loess soil contaminated by the flame retardant Tetrabromobisphenol A (TBBPA), chloride (Cl(-)) and bromide (Br(-)) was studied in undisturbed laboratory column experiments (20 cm diameter, 45 cm long) and a small field plot (2 x 2 m). While the soluble inorganic ions (Cl(-) and Br(-)) were efficiently flushed from the soil profile after less than three pore volumes (PV) of water, about 50% of the initial amount of TBBPA in the soil was also flushed, despite its hydrophobic nature. TBBPA leaching was made possible due to a significant increase in the pH of the soil solution from 7.5 to 9, which increased TBBPA aqueous solubility. The remaining TBBPA mass in the soil was not mobilized from its initial location in the topsoil due to the decrease in pH at this horizon. In situ soil flushing demonstrated that this method is a feasible treatment for reducing soil contamination at this site.     

Simulations of stratospheric to tropospheric transport during the tropical cyclone Marlene event

Enhanced ozone values observed in the upper troposphere near intense tropical cyclones have raised the question of the role of stratospheric–tropospheric exchange. The dynamical mechanisms involved in the enhanced ozone values of 6 April 1995 observed at Reunion and associated with the tropical cyclone Marlene could not be explained by ECMWF meteorological analysis with 1.125° horizontal resolution. A previous study based on the ECHAM model has demonstrated the impact of biomass burning, but of limited amplitude (<60–80 ppbv max). In this paper, the upper tropospheric ozone enhancement on the periphery of Marlene has been studied with a mesoscale model (MESO-NH). This model is able to reproduce a stratospheric PV filament into the troposphere, crossing the isentropes to the 350 K level. The ageostrophic circulation associated with divergence zones that have induced vertical movements has been shown. Further, the influence of vertical wind shear, evident in both the mesoscale analysis and in the idealized HURRICANE tropical cyclone model, also contributes to our understanding of this downward transport process.     

The principle and effect of transfer agent for the removal of PCE during in situ chemical oxidation

Viscosity remedial technology, which uses a water-soluble polymer mixed with remedial fluids, has been introduced in recent years to improve the removal efficacy of perchloroethylene/tetrachloroethylene (PCE) by improving oxidant coverage (i.e. sweep efficiency). Xanthan gum and hydrolysed polyacrylamide (HPAM) are relatively stable with time and temperature and possess salt and oxidation resistance, indicating that they may be good flooding agents (the former is better than the latter in this work). In this work, we quantified the polymer directly improved oxidation of PCE during transport by using a two-dimensional flow tank. Using a low pore volume (≤3.0), the removal rate of the PCE increased with the polymer concentration before stabilizing at approximately 93.00 and 88.30% for xanthan and HPAM, respectively. In this work, over 80% of PCE was removed via less than 3.0 PV of the SDS solution, whereas complete removal (100%) was achieved with less than 3.0 PV of SDS foam. Furthermore, the new experimental discoveries demonstrate that xanthan is better than HPAM and SDS foam is a better remediation agent than the SDS solution for removing PCE.

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Graphical abstract (Reaction device, A - inlet device (pump 1#), B - 2D tank, C - outflow device (pump 2#), D - data recording and processing device, E - microscopic expression, E (a) - KMnO₄ flushing, E (b) - polymer solution flushing).

     

污泥基活性炭吸附Cu2+的应用研究

以城市污水处理厂剩余污泥为原料，以ZnCl₂为活化剂制取污泥基活性炭。以此污泥基活性炭为吸附剂，对含Cu²⁺的废水进行了吸附实验研究。考察了溶液pH值、Cu²⁺的起始浓度对Cu²⁺离子吸附量的影响；利用等温吸附实验作出吸附等温线，并考察了污泥基活性炭吸附剂吸附Cu²⁺的动力学方程。实验结果表明，污泥基活性炭对Cu²⁺具有良好的吸附性能。吸附的最佳pH值为5；吸附符合Langmuir和Freundlich吸附等温方程，吸附为优惠吸附，吸附量随着吸附质溶液浓度的增加而增大；吸附平衡时间为4 h，吸附动力学符合二级动力学方程。