Oil spill vulnerability assessment integrating physical, biological and socio-economical aspects: Application to the Cantabrian coast (Bay of Biscay, Spain)

A methodology has been developed to carry out an integrated oil spill vulnerability index, V, for coastal environments. This index takes into account the main physical, biological and socio-economical characteristics by means of three intermediate indexes. Three different integration methods (worst-case, average and survey-based) along with ESI-based vulnerability scores, V_ESI, proposed for the Cantabrian coast during the Prestige oil spill, have been analyzed and compared in terms of agreement between the classifications obtained with each one for this coastal area. Results of this study indicate that the use of the worst-case index, V_R, leads to a conservative ranking, with a very poor discrimination which is not helpful in coastal oil spill risk management. Due to the homogeneity of this coastal stretch, the rest of the methods, V_I, V_M and V_ESI, provide similar classifications. However, V_M and V_I give more flexibility allowing three indexes for each coastal segment and including socio-economic aspects. Finally, the V_I procedure is proposed here as the more advisable as using this index promotes the public participation that is a key element in the implementation of Integrated Coastal Zone Management (IZCM).     

TEMPERATURE AND THE PRODUCTIVITY-LIGHT RELATIONSHIP1

ABSTRACT: Seventy-three in situ primary productivity experiments over a six-month period in hypereutrophic Onondaga Lake near Syracuse, New York, demonstrated variations in the light saturation parameter, I_p, which in part describes the interaction between productivity and light. Substantial variations in I_p were observed (coefficient of variation = 60 percent). Variations in I_p were significantly correlated (greater than 99 percent confidence level) with temperature (°C). An Arrhenius-type relationship (I_p= 1.312 × 1.088 (^T-20)) accounted for approximately 37 percent of the variation in I_p and may be appropriate for other systems dominated by green algae.     

Estimates of health benefits due to reductions in ambient NO2 levels

A method is presented here by which the actual numbers of individuals in the U.S. population who would be expected to suffer respiratory illness as a result of exposure to ambient nitrogen dioxide (NO₂) concentrations in excess of the Federally-designated ambient air quality standard can be estimated. At the same time we have attempted to quantify how these adverse health effects would be alleviated by various degrees of reductions in current ambient concentrations. In addition, the health benefit expected to be derived by various NO_x emission control strategies will be examined utilizing the health benefit estimation method presented.It is estimated that there were approximately 33.2×10⁶ excess cases of respiratory illnesses in the U.S. in 1973 associated with ambient NO₂ concentrations in excess of the national ambient standard. A reduction of approximately 50 to 60 percent below 1973 NO₂ levels is needed to essentially eliminate excess respiratory illness associated with ambient NO₂ concentration.     

Treatment of Dichloromethane Using Gliding Arc Plasma

Decomposition of dichloromethane (CH₂Cl₂) using a gliding plasma was examined and reported in this paper. The effects of initial concentrations of CH₂Cl₂, total gas flow rates, and input frequency have been studied to evaluate the performance of gliding arc on CH₂Cl₂ decomposition. Using atmospheric pressure air as the carrier gas, experimental results indicate that the maximum conversion of CH₂Cl₂ was 95.1% at a total gas flow rate of 180 L/hr containing 1% by volume of CH₂Cl₂. The reaction occurred at an exothermic condition and gaseous products are dominated by CO, CHCl₃, and Cl₂. CO₂ and CCl₄ are also detected in the product stream in small amounts. The conversion of CH₂Cl₂ increases with the increasing applied voltage and decreasing total gas flow rate.     

深圳大气污染特征模拟及环境容量估算

本文根据深圳市8 个监测站点2013 年的逐日PM₁₀ 和PM_2.5 浓度监测数据、气象数据,统计风向、风速、稳定度联合频率等,利用污染物在大气中输送扩散模式,由实测的浓度值反推出污染物的产生量或排放量的方法,重点分析龙华新区PM₁₀ 和PM_2.5 的污染特征,并依据环境目标值,估算该区域剩余环境容量。研究结果表明,龙华新区全年盛行东风、南风,其风频分别为16.7%、13.2%,风速约为1.6m/s,PM₁₀、PM_2.5 浓度均呈现出季节性变化,秋、冬季浓度值较高,尤其在10 月到次年1 月份,其排放强度主要受本地污染源的影响。除此以外,其西、北部的污染源对其污染物浓度有一定的影响。新区PM₁₀ 和PM_2.5 的剩余环境容量均呈现负值,尤其以PM_2.5 最为突出,须大力加强减排控制,以达到环境目标值     

Comparison of several packings for CO2 chemical absorption in a packed column

CO₂ capture and storage has gained widespread attention as an option for reducing greenhouse gas emissions. Chemical absorption and stripping of CO₂ with hot potassium carbonate (K₂CO₃) solutions has been used in the past, however potassium carbonate solutions have a low CO₂ absorption efficiency. Various techniques can be used to improve the absorption efficiency of this system with one option being the addition of promoters to the solvent and another option being an improvement in the mass transfer efficiency of the equipment. This study has focused on improving the efficiency of the packed column by replacing traditional packings with newer types of packing which have been shown to have enhanced mass transfer performance. Three different packings (Super Mini Rings (SMRs), Pall Rings and Mellapak) have been studied under atmospheric conditions in a laboratory scale column for CO₂ absorption using a 30 wt% K₂CO₃ solution. It was found that SMR packing resulted in a mass transfer coefficient approximately 20% and 30% higher than that of Mellapak and Pall Rings, respectively. Therefore, the height of packed column with SMR packing would be substantially lower than with Pall Rings or Mellapak. Meanwhile, the pressure drop using SMR was comparable to other packings while the gas flooding velocity was higher when the liquid load was above 25 kg m⁻² s⁻¹. Correlations for predicting flooding gas velocities and pressure drop were fitted to the experimental data, allowing the relevant parameters to be estimated for use in later design.     

Monitoring of the microbial community composition in saline aquifers during CO2 storage by fluorescence in situ hybridisation

This study reveals the first analyses of the composition and activity of the microbial community of a saline CO₂ storage aquifer. Microbial monitoring during CO₂ injection has been reported. By using fluorescence in situ hybridisation (FISH), we have shown that the microbial community was strongly influenced by the CO₂ injection. Before CO₂ arrival, up to 6 × 10⁶ cells ml⁻¹ were detected by DAPI staining at a depth of 647 m below the surface. The microbial community was dominated by the domain Bacteria that represented approximately 60% to 90% of the total cell number, with Proteobacteria and Firmicutes as the most abundant phyla comprising up to 47% and 45% of the entire population, respectively. Both the total cell counts as well as the counts of the specific physiological groups revealed quantitative and qualitative changes after CO₂ arrival. Our study revealed temporal outcompetition of sulphate-reducing bacteria by methanogenic archaea. In addition, an enhanced activity of the microbial population after five months CO₂ storage indicated that the bacterial community was able to adapt to the extreme conditions of the deep biosphere and to the extreme changes of these atypical conditions.     

Study on the failure mechanism of potassium-based sorbent for CO2 capture and the improving measure

With thermogravimetric apparatus (TGA), X-ray diffraction (XRD) and barium sulfate gravimetric methods, the carbonation reactivities of K₂CO₃ and K₂CO₃/Al₂O₃ in the simulated flue gases with SO₂ are investigated and the reaction equations are inferred. Results show that there are KHCO₃ and K₂SO₃ generated. The generation K₂SO₃ reduces the utilization ratio of the sorbent. H₂O may accelerates the sulfation reaction of AR K₂CO₃ as K₄H₂(CO₃)₃·1.5H₂O is generated in the reaction among K₂CO₃, SO₂ and H₂O. K₂SO₃ is directly generated from sulfation reaction of K₂CO₃/Al₂O₃, because there are K₂CO₃·1.5H₂O and K₂SO₃ generated in the reaction among K₂CO₃/Al₂O₃, SO₂ and H₂O. K₂CO₃·1.5H₂O does not react with SO₂, and K₂CO₃·1.5H₂O/Al₂O₃ reacts with SO₂ slowly. Compare with the reaction process without H₂O pretreatment, the reaction rates of KAl30 increased after H₂O pretreatment and the failure ratio is about a half of that without H₂O pretreatment. So, K₂CO₃/Al₂O₃ shows good carbonation and anti-sulfation characteristic after H₂O pretreatment.     

Support vector machine based prediction of photovoltaic module and power station parameters

ABSTRACT

The uncertainty in the output power of the photovoltaic (PV) power generation station due to variation in meteorological parameters is of serious concern. An accurate output power prediction of a PV system helps in better design and planning. The present study is carried out for the prediction of output power of PV generating station by using Support Vector Machines. Two cases are considered in the present study for prediction. Case-I deals with the prediction of PV module parameters such as V_oc, I_sh, R_s, R_sh, I_max, V_max, P_max, and case-II deals with the prediction of power generation parameters such as P_DC, P_AC, and system efficiency. Historical data of PV power station with an installed capacity of 10 MW and weather information are used as input to develop four different seasons-based SVM models for all parameters. The performance results of the models are presented in terms of Mean Relative Error (MRE) and Root Mean Square Error (RMSE). Additionally, the performance results obtained with polynomial and Radial Based Function kernel are also compared to show that which kernel has better prediction accuracy, and practicability. The result shows that the minimum average RMSE and MRE for case-I with Radial Based Function kernel are 0.034%, 0.055%, 0.002%, 1.726%, 0.044%, 0.047%, 2.342%, and 0.005%, 0.014%, 0.079%, 0.885%, 0.005%, 0.007%, 0.013%, and for case-II with poly kernel are 0.014%, 0.016%, 0.149% and 0.011%, 0.0175, 1.03%, respectively. The present study will be helpful to provide technical guidance to the prediction of the PV power System.     

Power generation with CO2 capture: Technology for CO2 purification

The goal of this paper is to find methodologies for removing a selection of impurities (H₂O, O₂, Ar, N₂, SO_x and NO_x) from CO₂ present in the flue gas of two oxy-combustion power plants fired with either natural gas (467 MW) or pulverized fuel (596 MW). The resulting purified stream, containing mainly CO₂, is assumed to be stored in an aquifer or utilized for enhanced oil recovery (EOR) purposes. Focus has been given to power cycle efficiency i.e.: work and heat requirements for the purification process, CO₂ purity and recovery factor (kg of CO₂ that is sent to storage per kg of CO₂ in the flue gas). Two different methodologies (here called Case I and Case II) for flue gas purification have been developed, both based on phase separation using simple flash units (Case I) or a distillation column (Case II). In both cases purified flue gas is liquefied and its pressure brought to 110 atm prior to storage.Case I: A simple flue gas separation takes place by means of two flash units integrated in the CO₂ compression process. Heat in the process is removed by evaporating the purified liquid CO₂ streams coming out from both flashes. Case I shows a good performance when dealing with flue gases with low concentration of impurities. CO₂ fraction after purification is over 96% with a CO₂ recovery factor of 96.2% for the NG-fired flue gas and 88.1% for the PF-fired flue gas. Impurities removal together with flue gas compression and liquefaction reduces power plant output of 4.8% for the NG-fired flue gas and 11.6% for the PF-fired flue gas. The total amount of work requirement per kg stored CO₂ is 453 kJ for the NG-fired flue gas and 586 kJ for the PF-fired flue gas.Case II: Impurities are removed from the flue gas in a distillation column. Two refrigeration loops (ethane and propane) have been used in order to partially liquefy the flue gas and for heat removal from a partial condenser. Case II can remove higher amounts of impurities than Case I. CO₂ purity prior to storage is over 99%; CO₂ recovery factor is somewhat lower than in Case I: 95.4% for the NG-fired flue gas and 86.9% for the PF-fired flue gas, reduction in the power plant output is similar to Case I.Due to the lower CO₂ recovery factor the total amount of work per kg stored CO₂ is somewhat higher for Case II: 457 kJ for the NG-fired flue gas and 603 kJ for the PF-fired flue gas.     

Energy conversion from electrolyte concentration gradient using charged nano-pores

Power generation based on the reversed electro-dialysis (RED) cell is studied both numerically and experimentally in this work. The membrane that separates the concentrated and dilute electrolytes is treated as a charged nano-pore array. Both numerical and experimental results show that the RED cell performance is similar to the typical electrochemical cell having a linearly varied current–voltage relation. The open circuit voltage and short-circuit current depend on the ion selectivity of the nano-pore membrane, which is related to the concentration ratio, pore surface charge density, and pore size. The highest energy conversion efficiencies are approximately 48% and 24% from numerical predictions and experimental measurements, respectively. The reason for this discrepancy is attributed to the inhomogenous pore size and surface charge density distributions of the Al₂O₃ membrane used in these experiments.     

Techno-Economic Study of CO2 Capture from an Existing Cement Plant Using MEA Scrubbing

Carbon dioxide is the major greenhouse gas responsible for global warming. Man-made CO₂ emissions contribute approximately 63% of greenhouse gases and the cement industry is responsible for approximately 5% of CO₂ emissions emitting nearly 900 kg of CO₂ per 1000 kg of cement. CO₂ from a cement plant was captured and purified to 98% using the monoethanolamine (MEA) based absorption process. The capture cost was $51 per tonne of CO₂ captured, representing approximately 90% of total cost. Steam was the main operating cost representing 39% of the total capture cost. Switching from coal to natural gas reduces CO₂ emissions by about 18%. At normal load, about 36 MW of waste heat is available for recovery to satisfy the parasitic heat requirements of MEA process; however, it is very difficult to recover.     

A study on oxidative degradation of polyacrylamide in wastewater with UV/FENTON/C4H4O62−

The degradation of polyacrylamide (PAM) in simulate wastewater was studied in UV/Fenton/C₄H₄O₆^2? system. The factors such as molecular ratio of H₂O₂/Fe²⁺/C₄H₄O₆^2?, pH, and the dosage of Fenton reagent that could affect the PAM degradation in the UV/Fenton/C₄H₄O₆^2? system were investigated. The experimental results showed that adding C₄H₄O₆^2? to UV/Fenton system could form photosensitive ferrous complexes, which led to higher degradation efficiency of PAM. The degradation rate of PAM could be up to 95.2% under the following conditions: the concentration of H₂O₂, Fe²⁺, and C₄H₄O₆^2? were 22.5, 2.25, and 2.25 mmol/L, respectively (i.e., molecular ratio of H₂O₂/Fe²⁺/C₄H₄O₆^2? was 10:1:1), the pH value was 3.0.     

Water/acid gas interfacial tensions and their impact on acid gas geological storage

Acid gas geological disposal is a promising process to reduce CO₂ atmospheric emissions and an environment-friendly and economic alternative to the transformation of H₂S into sulphur by the Claus process. Acid gas confinement in geological formations is to a large extent controlled by the capillary properties of the water/acid–gas/caprock system, because a significant fraction of the injected gas rises buoyantly and accumulates beneath the caprock. These properties include the water/acid gas interfacial tension (IFT), to which the so-called capillary entry pressure of the gas in the water-saturated caprock is proportional. In this paper we present the first ever systematic water/acid gas IFT measurements carried out by the pendant drop technique under geological storage conditions. We performed IFT measurements for water/H₂S systems over a large range of pressure (up to P = 15 MPa) and temperature (up to T = 120 °C). Water/H₂S IFT decreases with increasing P and levels off at around 9–10 mN/m at high T (≥70 °C) and P (>12 MPa). The latter values are around 30–40% of water/CO₂ IFTs, and around 20% of water/CH₄ IFTs at similar T and P conditions. The IFT between water and a CO₂ + H₂S mixture at T = 77 °C and P > 7.5 MPa is observed to be approximately equal to the molar average IFT of the water/CO₂ and water/H₂S binary mixtures. Thus, when the H₂S content in the stored acid gas increases the capillary entry pressure decreases, together with the maximum height of acid gas column and potential storage capacity of a given geological formation. Hence, considerable attention should be exercised when refilling with a H₂S-rich acid gas a depleted gas reservoir, or a depleted oil reservoir with a gas cap: in the case of hydrocarbon reservoirs that were initially (i.e., at the time of their discovery) close to capillary leakage, acid gas leakage through the caprock will inevitably occur if the refilling pressure approaches the initial reservoir pressure.     

Producing biodiesel from waste animal oil by modified ZnO

Biodiesel produced by transesterification of waste animal oil is a promising green fuel in the future. ZnO-Al₂O₃ and ZnO/Zn₂Al composition oxides were prepared by co-precipitation method and impregnation method, respectively. The above catalysts were characterized by X-ray diffraction (XRD), Brunauer--Emmett--Teller (BET) and CO₂ adsorption and temperature-programmed desorption (CO₂-TPD) and show that the high activity for the catalyst is attributed to its high alkalinity. The reaction parameters were optimized and the results show that the transesterification ratio of waste animal oil can reach 98.7% with 10% ZnO/Zn₂Al catalyst after 2 h. Moreover, 10%ZnO/Zn₂Al compound oxides can be active for the successive cycles. The glycerol as a predominant by-product after transesterification is of high purity with high use value.     

国家《大气污染防治行动计划》健康效益评估

为了提高空气质量改善进程,2013 年国家发布了《大气污染防治行动计划》。本文基于空气污染与健康效益评估模型(BenMAP),对人口分布资料、大气污染与人体健康影响的暴露反应关系等进行了本土化修正,采用“支付意愿法”与“疾病成本法”相结合的方法,系统评估了《大气污染防治行动计划》实施后,PM_2.5 污染变化引起的环境健康效益。研究结果表明,《大气污染防治行动计划》的实施将在一定程度上降低PM_2.5 环境浓度,改善环境空气质量。如果《大气污染防治行动计划》空气质量目标全面实现,可以避免城镇8.9 万居民的过早死亡,减少12 万人次住院治疗以及941 万人次的门诊和急诊病例,实现的全国健康效益约为867 亿元/ 年,说明了《大气污染防治行动计划》实施的健康有益性。本文对政府部门开展污染损失评估及制定环境健康政策具有重要的参考价值。     

Treatment of landfill leachates by nanofiltration

Landfill leachate contains high concentrations of organic matter, color, heavy metals and toxic substances. This study presents the feasibility of a commercial nanofiltration membrane (NF-300) in the removal of pollutants from a landfill leachate generated from the Treatment Stabilization and Disposal Facility in Gujarat state of India. Two different leachate samples (Leachates A and B) were collected from the downstream side of closed landfill cells A and B. The average quality of the leachate was 67 719 mg/L COD, 217 mg/L ammonical nitrogen, 22 418 mg/L BOD, 3847 mg/L chlorides and 909 mg/L sulphate. The operating variables studied were applied pressure (4–20 atm), feed flowrate (5–15 L/min) and pH (2, 4, 5.5 and 6.7). It was observed that the solute rejection (R_O) increased with increase in feed pressure and decreased with increase in feed concentration at constant feed flowrate. In the present study, the rejection of cations followed the sequence: R_O (Cr³⁺) > R_O (Ni²⁺) > R_O (Zn²⁺) > R_O (Cu²⁺) > R_O (Cd²⁺) for leachates A and B. The order of solute rejection sequence is inversely proportional to the diffusion coefficients. The rejection of sulphate ions by the NF-300 membrane was 83 and 85%, while the rejection of chlorides was 62 and 65% for leachates A and B, respectively. The NF-300 membrane was characterized by using the combined-film theory-Spiegler–Kedem (CFSK) model based on irreversible thermodynamics and the ion transport model based on the extended Nernst–Planck equation. The membrane transport parameters were estimated using the Levenberg–Marquadt method. The estimated parameters were used to predict the membrane performance and the predicted values are in good agreement with the experimental results.     

Evaluation of Fenton and ozone-based advanced oxidation processes as mature landfill leachate pre-treatments

Fenton treatment (Fe²⁺/H₂O₂) and different ozone-based Advanced Oxidation Processes (AOPs) (O₃, O₃/OH⁻ and O₃/H₂O₂) were evaluated as pre-treatment of a mature landfill leachate, in order to improve the biodegradability of its recalcitrant organic matter for subsequent biological treatment. With a two-fold diluted leachate, at optimised experimental conditions (initial pH 3, H₂O₂ to Fe²⁺ molar ratio of 3, Fe²⁺ dosage of 4 mmol L⁻¹, and reaction time of 40 min) Fenton treatment removed about 46% of chemical oxygen demand (COD) and increased the five-day biochemical oxygen demand (BOD₅) to COD ratio (BOD₅/COD) from 0.01 to 0.15. The highest removal efficiency and biodegradability was achieved by ozone at higher pH values, solely or combined with H₂O₂. These results confirm the enhanced production of hydroxyl radical under such conditions. After the application for 60 min of ozone at 5.6 g O₃ h⁻¹, initial pH 7, and 400 mg L⁻¹ of hydrogen peroxide, COD removal efficiency was 72% and BOD₅/COD increased from 0.01 to 0.24. An estimation of the operating costs of the AOPs processes investigated revealed that Fe²⁺/H₂O₂ was the most economical system (8.2 € m⁻³ g⁻¹ of COD removed) to treat the landfill leachate. This economic study, however, should be treated with caution since it does not consider the initial investment, prices at plant scale, maintenance and labour costs.     

An investigation of a heat pump system using CO2/propane mixture as a working fluid

In order to decrease the heat rejection pressure of heat pump using pure working fluid, CO₂ or R744, other natural component including hydrocarbons (R290, R600a, R600, R1270, R170, R601) and dimethyl ether (RE170) is added to CO₂, respectively, and then six binary mixtures are achieved. By environmental and thermodynamic comparisons, R290 is selected to be the most appropriate component candidate to mix with CO₂, and meanwhile to weaken the flammability and explosivity for pure R290. Then, the system performances of heat pump using mixture of CO₂ and R290 were experimentally studied when R290 is added to CO₂ with a small fraction, and compared with that of the pure CO₂. The experimental test rig is designed and set up for the transcritical heat pump system. When the refrigerant charge is variable, the heating coefficient performance, optimum heat rejection pressure, compressor power, mass flow rate of refrigerant, and total heat coefficient of gas cooler were researched. The variation ratios of heating coefficient performance and heating capacity with deviation from the optimum refrigerant charge were also investigated. The optimum refrigerant charge of CO₂/R290 is obtained and the research results show that the addition of R290 to CO₂ can efficiently reduce the heat rejection pressure and improve the system performance. The results in the present work could provide useful guidelines for the design and operation of heat pump system using CO₂-based mixture.