Basic processes in phytoremediation and some applications to air pollution control

In this short review, basic processes for phytoremediation and plant enzymes that are potentially useful in phytoremediation are briefly summarized. The remaining part describes the applications of the basic processes to decontaminate pollutants in the environments that have been done in our laboratory. Our work includes (1) analysis of the capability of various naturally occurring plants to decontaminate atmospheric nitrogen dioxide and selection of nitrogen-dioxide-philic plants that grow with nitrogen dioxide as the sole nitrogen source, (2) production of transgenic plants to improve plants' capability to decontaminate atmospheric nitrogen dioxide, and (3) analysis of the denitrification process in plants to innovate a gas--gas-converting plants that convert nitrogen dioxide to nitrogen gas.     

Soil-to-plant transfer factors for natural radionuclides and stable elements in a Mediterranean area

The transfer factors (TF) for natural uranium isotopes (238U and 234U), thorium isotopes (232Th, 230Th and 228Th), and 226Ra were obtained in plant samples (grass-pasture) growing in granitic and alluvial soils around a disused uranium mine located in the Extremadura region in the south-west of Spain. Affected and non-affected areas of the mine presented large differences in the activity concentrations of radionuclides of the uranium series. We also determined transfer factors for several stable elements (essential and non-essential). A set of statistical tests were applied to validate the data. The results showed that the transfer factors for both the natural radionuclides and the stable elements are independent of the two substrate types involved and also of the two areas considered in the study.     

Investigation of appropriate initial composition and aeration method for co-composting of yard waste and market wastes

The purpose of this research was to shorten the composting period by speeding up the composting process and to obtain good quality compost that can be used in agriculture. In order to accomplish the acceleration of the process, different mixtures of feedstock were loaded to the composting containers to observe the effect of initial composition on the quality of the compost and the rate of composting. The first feedstock prepared was composed of grass, leaves and market waste whereas the second feedstock composed only of leaves and market wastes. Composting process was accomplished by applying different composting methods such as composting without manual stirring, with manual stirring, with aeration by air, with aeration by oxygen, with manual stirring and aeration by air and finally by with manual stirring and aeration by oxygen to achieve the purpose of the research. Aeration was found as a primary requirement for the acceleration of composting because it was observed that when the aeration was not applied the conversion of nutrients was very low. The high conversion efficiency of the nutrients in the feedstock with market and yard wastes-without grass-resulted in higher quality end product. The organic content of the composted yard and market wastes were monitored and the best operational parameters and methods were identified. Parameters such as temperature, moisture, pH and end-product metal contents were also monitored in the study. and the experiments were run in duplicates. Corrected C/N, (C/N)t/(C/N)initial, were used in the calculations which provided objectivity in comparison of the compost quality with respect to nutritional components. The C/N change was found to be higher in the container that was manually stirred and aerated with oxygen but with regard to the economic feasibility of the system aeration with air was preferred. Compost quality that was achieved in the study was compared to the standards of different countries with respect to the amount of metal contents in the end-product. The applicability of the end-product in agriculture depends on the level of contaminants in the compost, especially metals that have to be present only in trace amounts.     

Organochlorine pollutants in remote mountain lake waters

Hexachlorocyclohexanes (HCHs; alpha- and gamma-isomers), endosulfans (alpha- and beta-isomers and the sulfate residue), hexachlorobenzene (HCB), dichlorodiphenyltrichloroethane (DDTs), and polychlorobiphenyls (PCBs) were measured in waters from three European remote mountain lakes situated in the Alps, Pyrenees, and Caledonian mountains. Sampling encompassed both ice-free and ice-covered periods at different water column depths. High HCH concentrations were found in all lakes, those in the Alps and Pyrenees (990-2,900 pg/L) being among the highest recorded in continental waters. Endosulfans and endosulfan sulfate (120-1,150 pg/L) were the second major group of organochlorine contaminants, showing a remarkable stability upon atmospheric long-range transport. The concentrations of HCB, DDTs, and PCB (4-8, 0.6-16, and 26-110 pg/L, respectively) were low in comparison with other continental waters. Hexachlorocyclohexanes, endosulfans, and HCB were essentially found in the dissolved phase. Phase partitioning of the more hydrophobic compounds exhibited a dependence on temperature and water-suspended particles. Comparison between different sampling seasons and water depths indicated a remarkable concentration uniformity within lake, but major interlake differences. Normalization to turnover rates showed higher interlake similarity. Preferential accumulation of the less volatile compounds in the Alp lake and significant increase of baseline contributions of organochlorine compounds and residues in the Caledonian lake are also evidenced from these turnover rates.     

Heavy metal anomalies in lagoon sediments related to intensive agriculture in Altata-Ensenada del Pabellón coastal system (SE Gulf of California)

Heavy metal concentrations were examined in surface sediments from 79 sites within the Altata-Ensenada del Pabellon lagoon system. Data were normalized to separate natural from anthropogenic factors using aluminum and lithium as conservative elements and following two different discriminating criteria. For the normalization process, the natural metal concentrations were assumed to vary consistently with aluminum and lithium, unless the metal contents were of human origin. Strong linear correlations (P < .001) were observed between the conservative elements and the metals measured. According to Szefer's normalizing criteria, about 90% of the polluted sites, for at least one metal, occurred near agricultural discharge drains. In accordance with the Muller [Umschau 79 (1979) 778.] scale, this lagoon system is subject to pollutant effects only with regard to Pb (moderately to strongly polluted). It was concluded that either Al and Li could be useful to normalize granulometric variability in heavy metal studies of these lagoon sediments, and that Summers' normalization criterion proved more rigorous than Szefer's for these types of sediments.     

Lightning Fires in a Brazilian Savanna National Park: Rethinking Management Strategies

Fire occurrences and their sources were monitored in Emas National Park, Brazil (17°49′–18°28′S; 52°39′–53°10′W) from June 1995 to May 1999. The extent of burned area and weather conditions were registered. Forty-five fires were recorded and mapped on a GIS during this study. Four fires occurred in the dry winter season (June–August; 7,942 ha burned), all caused by humans; 10 fires occurred in the seasonally transitional months (May and September) (33,386 ha burned); 31 fires occurred in the wet season, of which 30 were caused by lightning inside the park (29,326 ha burned), and one started outside the park (866 ha burned). Wet season lightning fires started in the open vegetation (wet field or grassy savanna) at a flat plateau, an area that showed significantly higher fire incidence. On average, winter fires burned larger areas and spread more quickly, compared to lightning fires, and fire suppression was necessary to extinguish them. Most lightning fires were patchy and extinguished primarily by rain. Lightning fires in the wet season, previously considered unimportant episodes, were shown to be very frequent and probably represent the natural fire pattern in the region. Lightning fires should be regarded as ecologically beneficial, as they create natural barriers to the spread of winter fires. The present fire management in the park is based on the burning of preventive firebreaks in the dry season and exclusion of any other fire. This policy does not take advantage of the beneficial effects of the natural fire regime and may in fact reduce biodiversity. The results presented here stress the need for reevaluating present policies and management procedures concerning fire in cerrado conservation areas.     

Land Evaluation in a Salt-Affected Irrigated District Using an Index of Productive Potential

2 semiarid irrigated area with salt-affected soils. The available soil map is at 1:100,000 scale and its mapping units are used for the land evaluation with the FAO framework. These data are then elaborated using the index value method. This procedure gives a map of land evaluation units and a table that rates the productive potential of these units for six crops: alfalfa, barley, maize, rice, sunflower, and wheat.     

Effect of Recycling on Material Properties of Glass-filled Polyethylene Terephthalate

Recycled plastics are considered low performance materials because their properties are expected to decrease drastically with recycling. The objective of this study was to characterize a 15 wt.% glass filled polyethylene terephthalate (rPET-15GF) using six recycle generations and four recycle ratios. Mechanical properties such as tensile strength, elastic modulus, and percent elongation to failure of the PET composite were determined for various recycle generations and recycle ratios. Results show that the mechanical properties of rPET-15GF decrease slightly per recycle generation. In contrast, thermal properties of rPET-15GF were not at all affected by the recycling process. This data demonstrates that recycled glass filled PET can be used effectively to fabricate components without significantly affecting their mechanical performance.     

Thermal and hydrometallurgical recovery methods of heavy metals from municipal solid waste fly ash

Heavy metals in fly ash from municipal solid waste incinerators are present in high concentrations. Therefore fly ash must be treated as a hazardous material. On the other hand, it may be a potential source of heavy metals. Zinc, lead, cadmium, and copper can be relatively easily removed during the thermal treatment of fly ash, e.g. in the form of chlorides. In return, wet extraction methods could provide promising results for these elements including chromium and nickel. The aim of this study was to investigate and compare thermal and hydrometallurgical treatment of municipal solid waste fly ash. Thermal treatment of fly ash was performed in a rotary reactor at temperatures between 950 and 1050 °C and in a muffle oven at temperatures from 500 to 1200 °C. The removal more than 90% was reached by easy volatile heavy metals such as cadmium and lead and also by copper, however at higher temperature in the muffle oven. The alkaline (sodium hydroxide) and acid (sulphuric acid) leaching of the fly ash was carried out while the influence of temperature, time, concentration, and liquid/solid ratio were investigated. The combination of alkaline-acidic leaching enhanced the removal of, namely, zinc, chromium and nickel.