Feasibility study of using brine for carbon dioxide capture and storage from fixed sources

A laboratory-scale reactor was developed to evaluate the capture of carbon dioxide (CO2) from a gas into a liquid as an approach to control greenhouse gases emitted from fixed sources. CO2 at 5-50% concentrations was passed through a gas-exchange membrane and transferred into liquid media--tap water or simulated brine. When using water, capture efficiencies exceeded 50% and could be enhanced by adding base (e.g., sodium hydroxide) or the combination of base and carbonic anhydrase, a catalyst that speeds the conversion of CO2 to carbonic acid. The transferred CO2 formed ions, such as bicarbonate or carbonate, depending on the amount of base present. Adding precipitating cations, like Ca++, produced insoluble carbonate salts. Simulated brine proved nearly as efficient as water in absorbing CO2, with less than a 6% reduction in CO2 transferred. The CO2 either dissolved into the brine or formed a mixture of gas and ions. If the chemistry was favorable, carbonate precipitate spontaneously formed. Energy expenditure of pumping brine up and down from subterranean depths was modeled. We conclude that using brine in a gas-exchange membrane system for capturing CO2 from a gas stream to liquid is technically feasible and can be accomplished at a reasonable expenditure of energy.     

无机碳对浮游藻类生长和群落结构的影响

采用水族箱生态模拟方法,利用碳酸钠和碳酸氢钠作为碱度调节剂设置不同碱度水平,研究了氮磷营养相对充足的试验水体中藻类各相关指标对无机碳的响应,并对试验过程中所测得的理化指标和生物指标进行统计分析.研究表明:富营养水体无机碳含量与藻类叶绿素水平存在着正相关关系;适当增加水体中的无机碳浓度能够改变蓝、绿藻门种类比例;当碱度水平达到一定程度时,铜绿微囊藻可以逐渐成为优势种,并从体系中上升,演替成为水华.     

Toxic effects of anthraquinone and phenanthrenequinone upon Scenedesmus strains (green algae) at low and elevated concentration of CO2

Short-term (24h) experiments were performed to examine the effect of anthraquinone (ANTQ) and phenanthrenequinone (PHEQ) on two Scenedesmus armatus strains (B1-76 and 276-4d) grown in a batch culture system aerated with CO2 at a low (0.1%) or elevated (2%) concentration. ANTQ at concentrations within the range of 0.156-1.250 mg dm-3 inhibited the growth of B1-76 population in a concentration-dependent manner, and calculated EC50 for low-CO2 cells was 0.56 mg dm-3. The toxic effect of ANTQ on this strain was more pronounced in high-CO2 cells, where not only growth but also photosynthesis, respiration and SOD activity were significantly inhibited. In contrast, except for SOD activity, no ANTQ effects on strain 276-4d were found. PHEQ at concentrations within the range of 0.063-0.125 mg dm-3 inhibited the growth of B1-76 population in a concentration-dependent manner. The value of EC50 for low-CO2 B1-76 cells was 0.10 mg dm-3. PHEQ inhibited the growth of both strains regardless of CO2 concentration. In B1-76 cells affected by PHEQ, inhibition of photosynthesis was independent of the CO2 level, whereas the SOD activity was much higher in cultures aerated with 2% than with 0.1% CO2. Higher toxicity of PHEQ to strain 276-4d grown at 2% CO2 was accompanied by strong inhibition of photosynthesis, while in low-CO2 cells this process was slightly stimulated. The SOD activity in both low- and high-CO2 cells of strain 276-4d treated with PHEQ was 2-3 times higher compared with the controls. The pattern of SOD isoforms (PAGE analysis) obtained from cells exposed to ANTQ or PHEQ did not change compared with the controls, but the location of the SOD isoforms bands on gel was affected by the concentration of CO2. The results suggest that the strain-specific toxicity of ANTQ and PHEQ may result from oxidative stress. In addition, carbon dioxide appears to play an important role in the toxicity of quinones to algae.     

A Rapid In Situ Respiration Test for Measuring Aerobic Biodegradation Rates of Hydrocarbons in Soil

An in situ test method to measure the aerobic biodegradation rates of hydrocarbons in contaminated soil is presented. The test method provides an initial assessment of bioventing as a remediation technology for hydrocarbon-contaminated soil. The in situ respiration test consists of ventilating the contaminated soil of the unsatiirated zone with air and periodically monitoring the depletion of oxygen (O2) and production of carbon dioxide (CO2) over time after the air is turned off. The test is simple to implement and generally takes about four to five days to complete. The test was applied at eight hydrocarbon-contaminated sites of different geological and climatic conditions. These sites were contaminated with petroleum products or petroleum fuels, except for two sites where the contaminants were primarily polycyclic aromatic hydrocarbons. Oxygen utilization rates for the eight sites ranged from 0.02 to 0.99 percent O2/hour. Estimated biodegradation rates ranged from 0.4 to 19 mg/kg of soil/day. These rates were similar to the biodegradation rates obtained from field and pilot studies using mass balance methods. Estimated biodegradation rates based on O2 utilization were generally more reliable (especially for alkaline soils) than rates based on CO2 production. CO2 produced from microbial respiration was probably converted to carbonate under alkaline conditions.     

Effects of increased sea water concentrations of CO2 on growth of the bivalve Mytilus edulis L

It has been proposed that emission of anthropogenic carbon dioxide to the atmosphere will lead to increased concentrations of CO(2) in sea water corresponding to a decrease of pH of several tenths of pH units. An experiment was performed to test the effects of increased sea water concentrations of CO(2) on shell growth of the blue mussel Mytilus edulis. The experiment was performed in aquaria continuously flushed with sea water spiked with CO(2) to provide five different levels of pH between 6.7 and control sea water with a pH of 8.1. The shell length of the mussels was measured at the start and end of the 44 days experimental period. No mortality was observed during the first 23 days of the experiment. The growth increment in mm was much larger for small mussels than for large mussels, but relative growth profile as function of pH was more similar in the two size groups; observed differences may be random variation between samples. The experiments showed that CO(2) induced reduction of pH affects the growth of M. edulis negatively. There was a strong and statistically significant decrease in growth at the lowest pH values, with virtually no growth at pH = 6.7 and reduced growth at pH = 7.1. The effect seems to set in between pH 7.4 and 7.1; at mean pH levels 7.4 and 7.6 the growth increments were not significantly different from growth at normal pH 8.1.     

Assessment of the impact of rising carbon dioxide and other potential climate changes on vegetation

The projected doubling of current levels of atmospheric carbon dioxide concentration ([CO(2)]) during the next century along with increases in other radiatively active gases have led to predictions of increases in global air temperature and shifts in precipitation patterns. Additionally, stratospheric ozone depletion may result in increased ultraviolet-B (UV-B) radiation incident at the Earth's surface in some areas. Since these changes in the Earth's atmosphere may have profound effects on vegetation, the objectives of this paper are to summarize some of the recent research on plant responses to [CO(2)], temperature and UV-B radiation. Elevated [CO(2)] increases photosynthesis and usually results in increased biomass, and seed yield. The magnitude of these increases and the specific photosynthetic response depends on the plant species, and are strongly influenced by other environmental factors including temperature, light level, and the availability of water and nutrients. While elevated [CO(2)] reduces transpiration and increases photosynthetic water-use efficiency, increasing air temperature can result in greater water use, accelerated plant developmental rate, and shortened growth duration. Experiments on UV-B radiation exposure have demonstrated a wide range of photobiological responses among plants with decreases in photosynthesis and plant growth among more sensitive species. Although a few studies have addressed the interactive effects of [CO(2)] and temperature on plants, information on the effects of UV-B radiation at elevated [CO(2)] is scarce. Since [CO(2)], temperature and UV-B radiation may increase concurrently, more research is needed to determine plant responses to the interactive effects of these environmental variables.     

Effects of pre-exposure to ultraviolet-B radiation on responses of tomato (Lycopersicon esculentum cv. New Yorker) to ozone in ambient and elevated carbon dioxide

Patterns of environmental change in the biosphere include concurrent and sequential combinations of increasing ultraviolet (UV-B) and ozone (O(3)) at increasing carbon dioxide (CO(2)) levels; long-term changes are resulting mainly from stratospheric O(3) depletion, greater tropospheric O(3) photochemical synthesis, and increasing CO(2) emissions. Effects of selected combinations were evaluated in tomato (Lycopersicon esculentum cv. New Yorker) seedlings using sequential exposures to enhanced UV-B radiation and O(3) in differential CO(2) concentrations. Ambient (7.2 kJ m(-2 )day(-1)) or enhanced (13.1 kJ m(-2) day(-1)) UV-B fluences and ambient (380 microl l(-1)) or elevated (600 microl l(-1)) CO(2) were imposed for 19 days before exposure to 3-day simulated O(3) episodes with peak concentrations of 0.00, 0.08, 0.16 or 0.24 microl l(-1) O(3) in ambient or elevated CO(2). CO(2) enrichment increased dry mass, leaf area, specific leaf weight, chlorophyll concentration and UV-absorbing compounds per unit leaf area. Exposure to enhanced UV-B increased leaf chlorophyll and UV-absorbing compounds but decreased leaf area and root/shoot ratio. O(3) exposure generally inhibited growth and leaf photosynthesis and did not affect UV-absorbing compounds. The highest dose of O(3) eliminated the stimulating effect of CO(2) enrichment after ambient UV-B pre-exposure on leaf photosynthesis. Pre-exposure to enhanced UV-B mitigated O(3) damage to leaf photosynthesis at elevated CO(2).     

Influence of organic matter on municipal solid waste incinerator bottom ash carbonation

The biodegradation of organic matter in municipal solid waste incinerator (MSWI) bottom ash was studied in order to investigate the interaction between the CO(2) produced by microbial respiration and bottom ash. Respiration tests were performed on bottom ash at different moisture contents in an incubator at 30 degrees C. O(2) consumption and CO(2) production were monitored and quantified. Leaching tests were carried out at the end of the experiments. Total organic carbon (TOC) leaching had decreased. Over a period of three weeks, pH decreased from 10.7 to 8.2 and bottom ash was considered to be fully carbonated. This showed that the organic matter found in bottom ash can provide a substrate for microbial activity. The CO(2) produced by microbial respiration was directly dissolved in bottom ash pore water in order to be mineralized in carbonate form. The origin of the carbon dioxide which induces maturation of bottom ash on weathering areas has never been really discussed and is often presumed to be atmospheric CO(2). However, biodegradation of organic matter could contribute for a large part to this phenomenon, depending on field-scale physico-chemical weathering conditions.     

填料塔中Na2CO3吸收高浓度H2S的传质特性

在填料吸收塔中考察了Na2CO3溶液吸收高浓度H2S气体的气液传质特性。通过测量填料塔进出口气体中H2S浓度计算了Na2CO3溶液吸收高浓度H2S气体的总体积传质系数（KGa），并研究了进气流速、吸收液流量、吸收温度和吸收液浓度对KGa的影响。结果表明，KGa随Na2CO3浓度、吸收液流量的增加而增加，随吸收温度、进气流速的升高而降低；在高浓度H2S吸收过程中液相传质阻力不能忽略。     

Physiological and biochemical responses of two cultivars of wheat to elevated levels of CO2 and SO2, singly and in combination

In view of the present increasing trends of anthropogenic emissions of carbon dioxide (CO2) and sulphur dioxide (SO2) throughout the world, the present study was aimed at investigating the long-term influence of elevated concentrations of CO2 and SO2, singly and in combination on the physiological and biochemical characteristics of two cultivars of wheat (Triticum aestivum L. cv. Malviya 234 and HP1209). For this purpose, the plants were grown in open top chambers under field conditions and were fumigated with 600 ppm CO2, 0.06 ppm SO2 and 600 ppm CO2 + 0.06 ppm SO2 separately for 8 h daily (0800-1600 h) from germination to grain maturity. The individual treatment of SO2 advers#ely affected both the cultivars of wheat by reducing protein and starch contents. The respiration rate, total soluble sugars and total phenolics, however, increased in response to SO2. Stimulation of photosynthesis rate and reduction in stomatal conductance and transpiration rate were observed under CO2 treatment. Concentrations of total soluble sugars, starch and total phenolics increased in response to CO2 and CO2 + SO2 treatments. In combined treatment, CO2 modified the plant response to SO2 in both the cultivars. Elevated CO2 increased the photosynthesis rate under combined treatment. Higher levels of starch and soluble sugars under combined treatment provided extra carbon for SO2 detoxification. The pattern of intraspecific response of wheat to different treatments was more or less similar, but the magnitude of response differed significantly.     

Bacteria additives to the changes in gaseous mass transfer from stored swine manure

Abstract

A bacteria additives treatment experiment in assessing the changes in gaseous mass transfer from stored swine manure is presented. The experiment is tested for ammonia, methane, hydrogen sulfide, and carbon dioxide emission data sampled from pilot swine manure columns and analyzed by GC/MS. The result shows that bacteria additives slightly reduce the methane and carbon dioxide releases, while the same additives do not show any effect on the reduction of ammonia. The hydrogen sulfide contents of stored swine manure continued to be low. Gas concentrations emitted from treated and untreated stored swine manure were: 3.76 and 2.2 ppm for methane, 0.35 and 0.11 ppm for ammonia, and 1000 and 470 ppm for carbon dioxide, respectively. A simple model to estimate gas emission rates is also developed from the viewpoint of two‐film resistance theory. The average emission rates calculated from the model for methane, ammonia, and carbon dioxide are respectively: 0.01, 0.0005, and 13.98 g/min from untreated stored manure; while 0.07, 0.096, and 0.55 g/min from treated manure. The emission model also indicates that for most gaseous pollutants of environmental concern, liquid phase transfer coefficient controls the rate of volatile compounds emitted from stored swine manure and gas phase transfer coefficient has insignificant effect in the calculation of overall mass transfer coefficient.     

城市节假日前后碳通量特征及其与车流量关系

全球变化背景下,城市作为主要的碳源,对其碳循环的研究成为陆地生态系统碳循环的重点内容之一。以上海市奉贤区为研究对象,基于涡度相关技术,结合定点连续观测的车流量数据,分析节假日（元旦）前后CO2浓度和碳通量的变化特征,及其与车流量的关系。结果表明,CO2浓度和通量日变化呈现明显的双峰型曲线,节假日CO2浓度（385.6mg/L）平均值低于工作日（401.1 mg/L）。在本研究时段内该系统表现为碳源,尽管在白天的某些时段是碳汇,表明城市系统碳通量受自然和人为2个因素共同作用,自然因素比如该系统中的香樟、雪松等常绿植物的光合作用,人为因素由人类活动造成。基于车流量与交通流量的线性回归分析表明,机动车量碳排放对于碳通量变化产生18%的贡献。     

高比表面积活性炭的制备及对Cr(Ⅵ)吸附的研究

以椰树壳为原料,运用水蒸汽和二氧化碳复合物理活化法在4 h内制备了2 162.84 m2/g的高比表面积活性炭,其孔径分布范围为1.1~2.5 nm。应用此吸附剂考察了溶液pH、吸附剂用量、接触时间和初始浓度对Cr(VI)离子吸附效果的影响,并讨论了固定吸附床中不同溶液流量对Cr(VI)去除效果的影响。结果表明:在温度为298 K、溶液pH为1.96、吸附剂用量为0.10 g、铬离子初始浓度为100 mg/L与接触时间为70 min的条件下,活性炭对铬离子具有较高的吸附容量,去除率高达99.32%;铬离子在吸附床中的穿透曲线具有陡峭的传质锋面,但随着铬离子溶液流量的增大脱除果率降低。     

Enhancement of the CO(2) retention capacity of X zeolites by Na- and Cs-treatments

Adsorption of carbon dioxide on alkaline modified X zeolites was investigated by temperature programmed desorption (TPD) analysis of these materials previously saturated with CO(2) at 50, 100 and 200 degrees C. Parent X zeolite (in its sodium form) was treated with different sodium and cesium aqueous solutions, using both carbonates and hydroxides as precursors. The resulting materials were characterised by nitrogen physisorption, XRD, and NH(3)-TPD, in order to determine their morphological, crystallographic and chemical properties. Slight desilication phenomena were observed using hydroxides as precursors, whereas the treatment with Cs salts lead to higher crystallinity losses. Several successive adsorption-desorption cycles were carried out in order to check the regenerability of the adsorbents. Cesium-treated zeolites present higher carbon dioxide retention capacities than the sodium treated and than the parent material. When working with these Cs-modified materials, the desorption takes place mainly at temperatures between 250 and 400 degrees C, results of great practical interest, since it allows the use these kinds of materials for adsorption-desorption cycles. The evolution of the retention capacity with temperature is also markedly more positive for Cs-treated zeolite, especially when carbonate is used as the precursor. These materials maintain high retention capacities at 100 degrees C (10mg g(-1)) and even at 200 degrees C (3mg g(-1)), temperatures at which the most of the adsorbents are inactive.     

Indoor and outdoor air quality investigation at schools in Hong Kong

Five classrooms in Hong Kong (HK), air-conditioned or ceiling fans ventilated, were chosen for investigation of indoor and outdoor air quality. Parameters such as temperature, relative humidity (RH), carbon dioxide (CO2), sulphur dioxide (SO2), nitric oxide (NO), nitrogen dioxide (NO2), respirable particulate matter (PM10), formaldehyde (HCHO), and total bacteria counts were monitored indoors and outdoors simultaneously. The average respirable particulate matter concentrations were higher than the HK Objective, and the maximum indoor PM10 level exceeded 1000 microg/m3. Indoor CO2 concentrations often exceeded 1000 microl/l in air-conditioning and ceiling fan classrooms, indicating inadequate ventilation. Maximum indoor CO2 level reached 5900 microl/l during class at the classroom with cooling tower ventilation. Increasing the rate of ventilation or implementation of breaks between classes is recommended to alleviate the high CO2 level. Other pollution parameters measured in this study complied with the standards. The two most important classroom air quality problems in Hong Kong were PM10 and CO2 levels.     

Productivity responses of Acer rubrum and Taxodium distichum seedlings to elevated CO2 and flooding

Elevated levels of atmospheric CO2 are expected to increase photosynthetic rates of C3 tree species, but it is uncertain whether this will result in an increase in wetland seedling productivity. Separate short-term experiments (12 and 17 weeks) were performed on two wetland tree species, Taxodium distichum and Acer rubrum, to determine if elevated CO2 would influence the biomass responses of seedlings to flooding. T. distichum were grown in replicate glasshouses (n = 2) at CO2 concentrations of 350 or 700 ppm. and A. rubrum were grown in growth chambers at CO2 concentrations of 422 or 722 ppm. Both species were grown from seed. The elevated CO2 treatment was crossed with two water table treatments, flooded and non-flooded. Elevated CO2 increased leaf-level photosynthesis, whole-plant photosynthesis, and trunk diameter of T. distichum in both flooding treatments, but did not increase biomass of T. distichum or A. rubrum. Flooding severely reduced biomass, height, and leaf area of both T. distichum and A. rubrum. Our results suggest that the absence of a CO2-induced increase in growth may have been due to an O2 limitation on root production even though there was a relatively deep (approximately 10 cm) aerobic soil surface in the non-flooded treatment.     

Effects of elevated CO2 concentration on the polyamine levels of field-grown soybean at three O3 regimes

Effects of increased ozone (O3) and carbon dioxide (CO2) on polyamine levels were determined in soybean (Glycine max L. Merr. cv. Clark) grown in open-top field chambers. The chamber treatments consisted of three O3 regimes equal to charcoal filtered (CF), non-filtered (NF), and non-filtered plus 40 nl litre(-1) O3 and CO2 treatments equal to 350, 400 and 500 microl litre(-1) for a total of nine treatments. Leaf samples were taken at three different times during the growing season. Examination of growth and physiological characteristics, such as photosynthesis, stomatal resistance, and shoot weight, revealed that increasing CO2 ameliorated the deleterious effects of increased O3. Results from the initial harvest, at the pre-flowering growth stage (23 days of treatment), showed that increasing O3 at ambient CO2 caused increases in putrescine (Put) and spermidine (Spd) of up to six-fold. These effects were lessened with increased CO2. Elevated CO2 increased polyamines in plants treated with CF air, but had no effect in the presence of ambient or enhanced O3 levels. Leaves harvested during peak flowering (37 days of treatment) showed O3-induced increases in Put and Spd at ambient CO2 concentrations. However, increased CO2 levels inhibited this response by blocking the O3-induced polyamine increase. Leaves harvested during the pod fill stage (57 days of treatment) showed no significant O3 or CO2 effects on polyamine levels. Our results demonstrate that current ambient O3 levels induce the accumulation of Put and Spd early in the growing season and that further increases in O3 could result in even greater polyamine increases. These results are consistent with a possible antiozonant function for polyamines. The ability of increased CO2 to protect soybeans from O3 damage, however, does not appear to involve polyamine accumulation.     

Utilization of agricultural waste corn cob for the preparation of carbon adsorbent

In the present study, a series of activated carbons were prepared from agricultural waste corn cob by chemical and physical activations with potassium hydroxide (KOH)/potassium carbonate (K2CO3) and carbon dioxide (CO2). The effect of process variables such as impregnation ratio, impregnation time, activation temperature and soaking time of CO2 was studied in order to relate these preparation parameters with the physical properties of final carbon products. The resulting activated carbons were characterized by nitrogen adsorption-desorption isotherms at 77 K. The surface areas and pore volumes of carbons were estimated by the BET equation, the Langmuir equation and the t-plot method. Under the experimental conditions investigated, the main parameters in the activation of corn cob were found to be the impregnation ratio and activation temperature. The soaking time of CO2 is another important variable, which had a strong effect on the pore volume development. The BET surface area and total pore volume were as large as about 2000 m2/g and about 1.0 cm3/g, respectively. This study showed that the activation of agricultural waste corn cob with KOH/K2CO3 and CO2 was suitable for the preparation of large-surface-area activated carbons.     

Investigation of solid-phase buffers for sulfur-oxidizing autotrophic denitrification.

This paper investigates biological denitrification using autotrophic microorganisms that use elemental sulfur as an electron donor. In this process, for each gram of nitrate-nitrogen removed, approximately 4.5 g of alkalinity (as calcium carbonate) are consumed. Because denitrification is severely inhibited below pH 5.5, and alkalinity present in the influent wastewaters is less than the alkalinity consumed, an external buffer was needed to arrest any drop in pH from alkalinity consumption. A packed-bed bioreactor configuration is ideally suited to handle variations in flow and nitrate loading from decentralized wastewater treatment systems, as it is a passive system and thus requires minimal maintenance; therefore, a solid-phase buffer packed with the elemental sulfur in the bioreactor is most suitable. In this research, marble chips, limestone, and crushed oyster shells were tested as solid-phase buffers. Bench- and field-scale studies indicated that crushed oyster shell was the most suitable buffer based on (1) the rate of dissolution of buffer and the buffering agent released (carbonate, bicarbonate, or hydroxide), (2) the ability of the buffer surface to act as host for microbial attachment, (3) turbidity of the solution upon release of the buffering agent, and (4) economics.     

Application of the EPR spin-trapping technique for the investigation of the reactions of carbonate, bicarbonate, and phosphate anions with hydroxyl radicals generated by the photolysis of H2O2

The spin trapping technique with electron paramagnetic resonance (EPR) detection of spin adducts was applied for the investigation of the reaction of hydroxyl radicals, generated by the photolysis of hydrogen peroxide, with bicarbonate and carbonate anions. The results have been compared with those obtained for aqueous solutions of hydrogen peroxide as well as solutions containing phosphate buffers at pH values identical with those of the carbonate, and bicarbonate solutions. Both the carbonate, and bicarbonate anions quenched the hydroxyl radicals more efficiently than phosphate buffers. The effect depended on the anion concentrations, and it was most pronounced in the presence of carbonate. Rate constants for the reaction of OH with the investigated anions have been calculated. They are very close to values reported in the literature, obtained using optical detection of the carbonate and phosphate radicals.