Annually, coal-fired electric power plants produce large volumes of potentially hazardous coal combustion products (CCPs) including fly ash. Since majority of the coal fly ash and other CCPs deposited in dry land fill...Annually, coal-fired electric power plants produce large volumes of potentially hazardous coal combustion products (CCPs) including fly ash. Since majority of the coal fly ash and other CCPs deposited in dry land fills or wet lagoons, they pose risk of contamination to local environment. In this study, we present results of leaching kinetics for As, Mo, and Se from three acidic fly ash samples collected from coal-fired power plants in the southeastern United States. This study shows that the leachate concentrations of As, Mo, and Se increase over time. Three kinetics equations, pseudo-second order, Elovich, and power-function, are able to adequately describe the experimental leaching kinetics data. Experimental leaching data and modeling results indicate that the rate limiting leaching of As, Mo, and Se is controlled by the diffusional process responsible for transferring these elements from interior to the surface of the particles as well as the dissolution of the fly ash particles. Therefore, it is important to adopt effective containment/treatment schemes to avoid potential and persistent dispersion of trace elements from ash disposal facilities to surrounding environment for a long time.展开更多
Growing global needs for food call for substantial increases in protein production in coming years, and for diligent conservation efforts. Manures from farm animals have been viewed both as a resource and as a waste p...Growing global needs for food call for substantial increases in protein production in coming years, and for diligent conservation efforts. Manures from farm animals have been viewed both as a resource and as a waste product, but they are critically important sources of nutrients for organic and integrated farming and for traditional Asian aquaculture. Given constraints on livestock production and capture fisheries, careful development of the aquaculture industry is a necessity. The production volume and market share of tilapia are advancing extremely rapidly, and so too is the proliferation of misinformation and controversy. Culture and feeding practices differ widely, but feeding is usually recognized as the single largest cost to producers. Traditional Asian integrated farming practices involve the use of manures and other farm wastes to promote algae and zoo-plankton production, serving as a sole or supplemental nutrient source to the food chain that supports tilapia growout. Tilapia also ingest manures. The efficient use of nutrients from manures can have multiple benefits to integrated terrestrial agriculture and aquaculture, as long as product safety and quality are not compromised. With efficient use, handling of manures is simplified, fish production costs are reduced, fish nutrition can be improved, and potentially polluting materials are cycled constructively on integrated farms. Consumer and press reactions to the use of farm manures in food production can be highly polarized. Published responses cover a range of extremes, from enthusiastic endorsement to volatile reactions and outright rejection;in some areas this practice is considered to be more of a “PR (Public Relations) problem” than a health hazard. The perception in online public media that tilapia coming from ponds fertilized with manure are heavily contaminated with pathogens has not been supported by evidence. The perspectives of farmers in two major tilapia production areas (China and the Philippines) are included.展开更多
Greenhouse gas emissions due to biological degradation processes of animal wastes are significant sources of air pollution from agricultural areas. The major environmental controls on these microbe-induced gas fluxes ...Greenhouse gas emissions due to biological degradation processes of animal wastes are significant sources of air pollution from agricultural areas. The major environmental controls on these microbe-induced gas fluxes are temperature and moisture content. The objective of this study was to model the effects of temperature and moisture content on emissions of CO2 and CH4 during the ambient drying process of dairy manure under controlled conditions. Gas emissions were continuously recorded over 15 d with paired fully automated closed dynamic chambers coupled with a Fourier Transformed Infrared gas analyzer. Water content and temperature were measured and monitored with capacitance sensors. In addition, on days 0, 3, 6, 9, 12 and 15, p H, moisture content, dissolved organic carbon and total carbon(TC) were determined. An empirical model derived from the Arrhenius equation confirmed high dependency of carbon emissions on temperature and moisture content. Results indicate that for the investigated dairy manure, 6.83% of TC was lost in the form of CO2 and 0.047% of TC was emitted as CH4.Neglecting the effect of temperature, the moisture contents associated with maximum gas emissions were estimated as0.75 and 0.79 g$g–1 for CO2 and CH4, respectively.展开更多
Aquaponics is a fish-plant recirculating system where nutrients received from the fish culture are absorbed by the plants for growth.The technology is relatively new for fish culture in Kenya,and the principles and op...Aquaponics is a fish-plant recirculating system where nutrients received from the fish culture are absorbed by the plants for growth.The technology is relatively new for fish culture in Kenya,and the principles and operations remain largely untested for many fish species.This study determined how stocking density affects the growth performance and water quality in a Nile tilapia-lettuce(Lactuca sativa)aquaponics system.The experimental design included five replicates for each of the aquaponic systems stocked at densities of 150,300,and 450 fish/m^(3) for a rearing period of 56 days.Each treatment had a planting density of 16 lettuce/m2.The water quality parameters ranges during the rearing period were 3.83-5.35 mg/L for dissolved oxygen,7.44 to 7.6 for pH,0.014 mg/L to 0.032 mg/L for total ammonium nitrate(TAN),1.11-1.34 mg/L for nitrate,and 0.01-0.08 mg/L for nitrite,and all decreased with increasing stocking density.The final weight of fingerlings was 25.2±4.2 g,32.0±3.8 g and 42.6±3.1 g for 450,300,and 150 fish/m^(3) respectively.Specific growth rate(SGR)was reduced with increasing stocking density whereas food conversion ratio(FCR)increased with stocking density.Aquaponic systems with the lowest stocking densities performed better than 300 and 450 fish/m^(3) respectively.展开更多
文摘Annually, coal-fired electric power plants produce large volumes of potentially hazardous coal combustion products (CCPs) including fly ash. Since majority of the coal fly ash and other CCPs deposited in dry land fills or wet lagoons, they pose risk of contamination to local environment. In this study, we present results of leaching kinetics for As, Mo, and Se from three acidic fly ash samples collected from coal-fired power plants in the southeastern United States. This study shows that the leachate concentrations of As, Mo, and Se increase over time. Three kinetics equations, pseudo-second order, Elovich, and power-function, are able to adequately describe the experimental leaching kinetics data. Experimental leaching data and modeling results indicate that the rate limiting leaching of As, Mo, and Se is controlled by the diffusional process responsible for transferring these elements from interior to the surface of the particles as well as the dissolution of the fly ash particles. Therefore, it is important to adopt effective containment/treatment schemes to avoid potential and persistent dispersion of trace elements from ash disposal facilities to surrounding environment for a long time.
文摘Growing global needs for food call for substantial increases in protein production in coming years, and for diligent conservation efforts. Manures from farm animals have been viewed both as a resource and as a waste product, but they are critically important sources of nutrients for organic and integrated farming and for traditional Asian aquaculture. Given constraints on livestock production and capture fisheries, careful development of the aquaculture industry is a necessity. The production volume and market share of tilapia are advancing extremely rapidly, and so too is the proliferation of misinformation and controversy. Culture and feeding practices differ widely, but feeding is usually recognized as the single largest cost to producers. Traditional Asian integrated farming practices involve the use of manures and other farm wastes to promote algae and zoo-plankton production, serving as a sole or supplemental nutrient source to the food chain that supports tilapia growout. Tilapia also ingest manures. The efficient use of nutrients from manures can have multiple benefits to integrated terrestrial agriculture and aquaculture, as long as product safety and quality are not compromised. With efficient use, handling of manures is simplified, fish production costs are reduced, fish nutrition can be improved, and potentially polluting materials are cycled constructively on integrated farms. Consumer and press reactions to the use of farm manures in food production can be highly polarized. Published responses cover a range of extremes, from enthusiastic endorsement to volatile reactions and outright rejection;in some areas this practice is considered to be more of a “PR (Public Relations) problem” than a health hazard. The perception in online public media that tilapia coming from ponds fertilized with manure are heavily contaminated with pathogens has not been supported by evidence. The perspectives of farmers in two major tilapia production areas (China and the Philippines) are included.
基金supported by funds from the USDA-NIFA AFRI Air Quality Program (2010-85112-50524)the Utah Agricultural Experiment Station, Utah State University, Logan, Utah, USA (approved as journal paper no. 8647)+2 种基金the National Natural Science Foundation of China (41401225)the Fundamental Research Funds for the Central Universities, China (N150204005)the Natural Science Foundation of Liaoning Province, China (201602250)
文摘Greenhouse gas emissions due to biological degradation processes of animal wastes are significant sources of air pollution from agricultural areas. The major environmental controls on these microbe-induced gas fluxes are temperature and moisture content. The objective of this study was to model the effects of temperature and moisture content on emissions of CO2 and CH4 during the ambient drying process of dairy manure under controlled conditions. Gas emissions were continuously recorded over 15 d with paired fully automated closed dynamic chambers coupled with a Fourier Transformed Infrared gas analyzer. Water content and temperature were measured and monitored with capacitance sensors. In addition, on days 0, 3, 6, 9, 12 and 15, p H, moisture content, dissolved organic carbon and total carbon(TC) were determined. An empirical model derived from the Arrhenius equation confirmed high dependency of carbon emissions on temperature and moisture content. Results indicate that for the investigated dairy manure, 6.83% of TC was lost in the form of CO2 and 0.047% of TC was emitted as CH4.Neglecting the effect of temperature, the moisture contents associated with maximum gas emissions were estimated as0.75 and 0.79 g$g–1 for CO2 and CH4, respectively.
基金Special thanks go to AquaFish Innovation Lab under the United States Agency for International Development(USAID)Cooperative Agreement Number EPP-A-00-06-00012-00 and the National Research funds(NRF)formerly known as the National Commission for Science Technology and Innovation(NACOSTI)for funding this project.
文摘Aquaponics is a fish-plant recirculating system where nutrients received from the fish culture are absorbed by the plants for growth.The technology is relatively new for fish culture in Kenya,and the principles and operations remain largely untested for many fish species.This study determined how stocking density affects the growth performance and water quality in a Nile tilapia-lettuce(Lactuca sativa)aquaponics system.The experimental design included five replicates for each of the aquaponic systems stocked at densities of 150,300,and 450 fish/m^(3) for a rearing period of 56 days.Each treatment had a planting density of 16 lettuce/m2.The water quality parameters ranges during the rearing period were 3.83-5.35 mg/L for dissolved oxygen,7.44 to 7.6 for pH,0.014 mg/L to 0.032 mg/L for total ammonium nitrate(TAN),1.11-1.34 mg/L for nitrate,and 0.01-0.08 mg/L for nitrite,and all decreased with increasing stocking density.The final weight of fingerlings was 25.2±4.2 g,32.0±3.8 g and 42.6±3.1 g for 450,300,and 150 fish/m^(3) respectively.Specific growth rate(SGR)was reduced with increasing stocking density whereas food conversion ratio(FCR)increased with stocking density.Aquaponic systems with the lowest stocking densities performed better than 300 and 450 fish/m^(3) respectively.