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 15,125 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Lettuce plants were grown utilizing water, inorganic elements, and CO2 inputs recovered from waste streams. The impact of these waste-derived inputs on the growth of lettuce was quantified and compared with results obtained when reagent grade inputs were used. Phytotoxicity was evident in both the untreated wastewater stream and the recovered CO2 stream. The toxicity of surfactants in wastewater was removed using several treatment systems. Harmful effects of gaseous products resulting from incineration of inedible biomass on crop growth were observed. No phytotoxicity was observed when inorganic elements recovered from incinerated biomass ash were used to prepare the hydroponic solution, but the balance of nutrients had to be modified to achieve near optimal growth. The results were used to evaluate closure potential of water and inorganic elemental loops for integrated plant growth and human requirements.
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PMID:Integration of crop production with CELSS waste management. 1154 58

Tomato (Lycopersicon esculentum Mill.) cvs. Red Robin (RR) and Reimann Philipp (RP) were grown hydroponically for 105 d with a 12 h photoperiod, 26 degrees C/22 degrees C thermoperiod, and 500 micromol m-2 s-1 PPF at either 400, 1200, 5000, or 10,000 micromol mol-1 (0.04, 0.12, 0.50, 1.00 kPa) CO2. Harvested fruits were analyzed for proximate composition, total dietary fiber, nitrate, and elemental composition. No trends were apparent with regard to CO2 effects on proximate composition, with fruit from all treatments and both cultivars averaging 18.9% protein, 3.6% fat, 10.2% ash, and 67.2% carbohydrate. In comparison, average values for field-grown fruit are 16.6% protein, 3.8% fat, 8.1% ash, and 71.5% carbohydrate (Duke and Atchely, 1986). Total dietary fiber was highest at 10,000 micromol mol-1 (28.4% and 22.6% for RR and RP) and lowest at 1000 micromol mol-1 (18.2% and 15.9% for RR and RP), but showed no overall trend in response to CO2. Nitrate values ranged from 0.19% to 0.35% and showed no trend with regard to CO2. K, Mg, and P concentrations showed no trend in response to CO2, but Ca levels increased from 198 and 956 ppm in RR and RP at 400 micromol mol-1, to 2537 and 2825 ppm at 10,000 micromol mol-1. This increase in Ca caused an increase in fruit Ca/P ratios from 0.07 and 0.37 for RR and RP at 400 micromol mol-1 to 0.99 and 1.23 for RR and RP at 10,000 micromol mol-1, suggesting that more dietary Ca should be available from high CO2-grown fruit.
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PMID:Effect of elevated carbon dioxide on nutritional quality of tomato. 1154 78

Information about compositional changes in plants grown in controlled environments is essential for developing a safe, nutritious diet for a Controlled Ecomological Life-Support System (CELSS). Information now is available for some CELSS candidate crops, but detailed information has been lacking for soybeans. To determine the effect of environment on macronutrient and mineral composition of soybeans, plants were grown both in the field and in a controlled environment where the hydroponic nutrient solution, photosynthetic flux (PPF), and CO2 level were manipulated to achieve rapid growth rates. Plants were harvested at seed maturity, separated into discrete parts, and oven dried prior to chemical analysis. Plant material was analyzed for proximate composition (moisture, protein, lipid, ash, and carbohydrate), total nitrogen (N), nonprotein N (NPN), nitrate, minerals, amino acid composition, and total dietary fiber. The effect of environment on composition varied by cultivar and plant part. Chamber-grown plants generally exhibited the following characteristics compared with field-grown plants: 1) increased total N and protein N for all plant parts, 2) increased nitrate in leaves and stems but not in seeds, 3) increased lipids in seeds, and 4) decreased Ca:P ratio for stems, pods, and leaves. These trends are consistent with data for other CELSS crops. Total N, protein N, and amino acid contents for 350 ppm CO2 and 1000 ppm CO2 were similar for seeds, but protein N and amino acid contents for leaves were higher at 350 ppm CO2 than at 1000 ppm CO2. Total dietary fiber content of soybean leaves was higher with 350 ppm CO2 than with 1000 ppm CO2. Such data will help in selecting of crop species, cultivars, and growing conditions to ensure safe, nutritious diets for CELSS.
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PMID:Controlled environments alter nutrient content of soybeans. 1154 79

A review of the scenarios for the Cretaceous/ Tertiary (K/T) boundary event is presented and a coherent hypothesis for the origin of the event is formulated. Many scientists now accept that the event was caused by a meteorite impact at Chicxulub in the Yucatan Peninsula, Mexico. Our investigations show that the oceans were already stressed by the end of the Late Cretaceous as a result of the long-term drop in atmospheric CO2, the long-term drop in sea level and the frequent development of oceanic anoxia. Extinction of some marine species was already occurring several million years prior to the K/T boundary. The biota were therefore susceptible to change. The eruption of the Deccan Traps, which began at 66.2 Ma, coincides with the K/T boundary events. It erupted huge quantities of H2SO4, HCl, CO2, dust and soot into the atmosphere and led to a significant drop in sea level and marked changes in ocean temperature. The result was a major reduction in oceanic productivity and the creation of an almost dead ocean. The volcanism lasted almost 0.7 m.y. Extinction of biological species was graded and appeared to correlate with the main eruptive events. Elements such as Ir were incorporated into the volcanic ash, possibly on soot particles. This horizon accumulated under anoxic conditions in local depressions and became the marker horizon for the K/T boundary. An oxidation front penetrated this horizon leading to the redistribution of elements. The eruption of the Deccan Traps is the largest volcanic event since the Permian-Triassic event at 245 Ma. It followed a period of 36 m.y. in which the earth's magnetic field failed to reverse. Instabilities in the mantle are thought to be responsible for this eruption and therefore for the K/T event. We therefore believe that the K/T event can be explained in terms of the effects of the Deccan volcanism on an already stressed biosphere. The meteorite impact at Chicxulub took place after the onset of Deccan volcanism. It probably played a regional, rather than global, role in the K/T extinction.
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PMID:Multiple factors in the origin of the Cretaceous/Tertiary boundary: the role of environmental stress and Deccan Trap volcanism. 1154 26

Considerable evidence exists to support the hypothesis that human-generated wastes can be utilized as resources in crop production. In the waste mix from a Closed Ecological Life Support System (CELSS), the elemental resources are found mainly in the solid fraction. In order to make these resources available for crop growth, it is necessary to convert the solid wastes to either an aqueous or a gaseous phase. Incineration is one method for processing solid wastes to produce a gaseous fraction and a small solid fraction of ash. Evidence from literature provides a compelling case for a working hypothesis that plants can utilize the gases of incineration. Although uptake and utilization of inorganic elements in the aqueous phase is well established, the uptake and utilization of inorganic elements in the gaseous phase, with the exception of CO2 and O2, is not fully understood. This paper attempts to (a) summarize existing literature on uptake/metabolism of inorganic elements in the gaseous fraction, with the exception of CO2 and O2 and (b) develop a working hypothesis to predict the use of incineration flue gases by plants. Preliminary experimental findings on effects of carbon monoxide, a component of the flue gas, are also presented.
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PMID:Can incineration technology convert CELSS wastes to resources for crop production? A working hypothesis and some preliminary findings. 1154 71

The application of carbonation treatment to cement-based wasteforms as a means to reduce the leachability of entrained undesirable substances, both radioactive and nonradioactive, has been the subject of much study over the past decade. Upon carbonation, hydrated cement phases release their water of hydration and are converted into carbonate minerals. The carbonation process has been shown to reduce the pore size distribution and permeability of the cementitious materials since portions of the original pore network become sites for precipitation of secondary carbonate minerals. As a result, the leachability of entrained contaminants can be markedly reduced. Current methods to carbonate cement-based wasteforms after they have cured rely on exposure to high pressure or supercritical CO2 pressures. In this study, a new low-pressure technique is presented. The method provides more complete carbonation than high-pressure techniques. The principle is to remove the water of reaction as it is produced, thereby maintaining an open pore network to facilitate the transfer of CO2 into the specimen. This is accomplished by conducting the reaction at near-vaccum pressures in the presence of a desiccant. The near-vacuum conditions lower the impedance of water transport from the carbonating specimen to the desiccant due to the large mean free path of the water vapor molecules. The technique was applied to a series of wasteform samples with entrained cationic and anionic waste components. Carbonation penetration depths of up to 11 mm were attained within 45 h of reaction for cylindrical wasteform samples prepared with OPC at a water/cement ratio of 0.60. A carbonation penetration depth of 15 mm was attained in a 6 d reaction of blended cement (OPC and 30% Class 'F' fly ash). In standardized leach tests, cationic waste constituents showed lower leachabilities from carbonated samples than from uncarbonated samples. Anionic waste constituents, however, showed greater leachabilities, and anion leachability increased with the degree of carbonation.
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PMID:Vacuum method for carbonation of cementitious wasteforms. 1168 75

The long-term leachability of heavy metals from municipal solid waste incinerator (MSWI) bottom ash is of concern because of its potential use as a secondary construction material. Calcite is the most important long-term buffer in MSWI bottom ash as it buffers solutions during percolation and is an important factor in the control of heavy-metal mobility. It has been argued that biodegradation of residual organic material in the MSWI is a significant source of acidity. Model calculations have therefore been carried out to determine the influence of biodegradation on the longevity of the calcite buffer. Using the program STEADYQL, which couples thermodynamic equilibrium with kinetically controlled reactions, solution composition was estimated at steady state. The concentration of Ca dissolved from calcite was estimated in the presence and absence of gypsum as a function of the reaction rate of a number of slow reactions: aerobic, ferrogenic, sulfogenic, and methanogenic biodegradation; diffusion of O2 into the system; degassing of CO2 out of the system; and dissolution of Ca silicate. It was found that, independent of the rate, the biodegradation of organic matter had little influence on the longevity of the calcite buffer (between 2,000 and 3,000 yr for a deposit of 1 m in depth), that anaerobic biodegradation may have a slight retarding effect, and that calcite dissolution due to acid input via precipitation was negligible (around 3% of the total at reference conditions for rainwater with a pH value of 4.3).
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PMID:Influence of biodegradation processes on the duration of CaCO3 as a pH buffer in municipal solid waste incinerator bottom ash. 1182 54

Circulating fluidized bed combustion (CFBC) ashes in contact with water, whether in liquid or vapour form, exhibit considerable chemical activity, which can continue for more than a year. From the point of view of the setting of CFBC ash-water mixtures and their behaviour, the formation of gypsum and of ettringite are important. The crystallisation of ettringite is associated with expansion of the set mass and absorption of water into the solids, but the ash-water system as a whole shrinks. The extent of ettringite formation is reduced if carbonation of free lime can take place. There is little carbonation if the set solids are covered by water but if contact with air is not restricted, the ettringite formed earlier slowly decomposes, its place being taken by calcite and gypsum. The fate of the aluminium from decomposed ettringite is uncertain; no new crystalline Al compounds are found. It appears that ultimately most analytical lime present can become carbonated. This is environmentally beneficial since it reduces chemical activity in the landfill, and reduces the amount of CO2 released due to limestone use. The main features of the behaviour of CFBC ash-water mixtures can be reproduced in model systems (CaO-Al2O3-CaSO4-H2O) but that of real ashes is complicated by the presence of silicates and possible interactions between silica and the strongly alkaline aqueous medium. Also, aluminates present in the ash are probably more active with respect to ettringite formation than pure aluminum hydroxide.
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PMID:The long term behaviour of CFBC ash-water systems. 1194 10

Airborne particulate matter (PM) is an important environmental issue because of its association with acute respiratory distress in humans, although the specific particle characteristics that cause lung damage have yet to be identified. Particle size, acid aerosols, water-soluble transition metals (e.g. Cu, Fe, V, Ni and Zn), polyaromatic hydrocarbons, and particle composition are the focus of several popular hypotheses addressing respiratory distress. All of the above mentioned characteristics are contained in PM generated from the combustion of both pulverized coal, and biomass, including dried municipal sewage sludge (MSS). In this investigation, we report results from collaborative interdisciplinary research on the inhalation health risks caused by particles emitted from the co-combustion of municipal sewage sludge (MSS) and coal. A solid particle resuspension system was implemented to resuspend ash particles. Mice were exposed to resuspended coal and MSS/coal ash particles. Mice exposed to MSS/coal ash particulate demonstrated significant increases in lung permeability, a marker of the early stages of pathological lung injury, while the mice exposed to coal-only ash did not. These results show that the composition of particles actually inhaled is important in determining lung damage. Zinc was significantly more concentrated in the MSS/coal ash than coal ash particles and the pH of these particles did not differ significantly. Specifically, an MSS/coal mixture, when burned, emits particles that may cause significantly more lung damage than coal alone, and that consequently, the use of MSS as a 'green', CO2-neutral replacement fuel should be carefully considered.
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PMID:Resuspension of coal and coal/municipal sewage sludge combustion generated fine particles for inhalation health effects studies. 1199 68

A study on the chemical stability of municipal solid waste (MSW) bottom ash submitted to weathering was carried out in order to identify and quantify the physico-chemical maturation mechanisms in a large heap (375 tonnes) over a period of about 18 months. The mineralogy and chemical composition of MSW bottom ash were analysed on fresh and maturated material. Calcite is the predominant newly formed mineral during bottom ash maturation, combined with aluminium hydroxides and various sulphates. Lead and zinc are trapped primarily by newly formed carbonates. Monitoring of the pore water and the outlet leachates revealed a marked contrast in the physico-chemical conditions within the heap and at the outlet. The salinity of the fluids peaked at around 16 g/l within the first few weeks and then progressively decreased to fluctuate between 5 and 8 g/l. Due to the high pH of the pore water, the average concentrations of heavy metals in the heap are high: 42.7, 9.6 and 0.8 mg/l for Cu, Pb and Zn. At the heap outlet, however, the leachates are buffered by carbonate precipitation due to equilibration with atmospheric CO2. Copper complexed as a chloride at the outlet remains at a relatively high concentration (10.2 mg/l), whereas Pb and Zn concentrations are below the limit of detection (<25 microg/l). A mass balance carried out over the 18 months of monitoring indicated that 86% of remobilized material within the heap is evacuated from the system. Within the heap, carbonation trapped 43 and 54% of the calcium and bicarbonate flux. The copper, lead and zinc flux at the heap outlet represent only 34, 18 and 19% of the actual remobilized mass of heavy metals.
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PMID:Chemical changes and leachate mass balance of municipal solid waste bottom ash submitted to weathering. 1200 44


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