Solar cooking innovations,their appropriateness,and viability

Environmental Science and Pollution Research - The successful use of solar energy for cooking requires the systems adopted not only to have technical attributes that conveniently address specific...     

Chemical characterization of synthetic soil from composting coal combustion and pharmaceutical by-products

Land application of coal combustion by-products (CCBs) mixed with solid organic wastes (SOWs), such as municipal sewage sludge, has become increasingly popular as a means of productively using what were once considered waste products. Although bulk chemical and physical properties of several of these CCB-SOW materials have been reported, detailed information about their synthesis and mineralogy of the CCB-SOW materials has not been reported. In this paper, chemical and mineralogical properties of a soil-like material obtained from composting a mixture of CCBs with a pharmaceutical fermentation by-product (FB) were investigated at the laboratory and field scale. All starting materials and products were characterized by X-ray diffraction (XRD), fourier transform infrared (FFIR) spectroscopy, and elemental analyses. The results showed that the FB was strongly bound to the CCBs and could not be removed by washing. Within 2 wk of the start of a composting study, there was a rapid drop in pH from 12 to 8, an increase in temperature to 70 degrees C, and a reduction in the dissolved oxygen content, attributed to the rapid establishment of a highly active microbial population. Composting produced a soil-like material with high levels of plant nutrients, a high nutrient retention capacity, and metal contents similar to median levels of those metals reported for soils. The levels of boron and soluble salts are such that sensitive plants may initially show toxicity symptoms. However, with adequate rainfall, leaching should rapidly remove most of the B and soluble salts. With care, the material produced is safe for use as a synthetic topsoil.     

Altered Soil-soil Water Interactions Inferred from Stream Water Chemistry at an Artificially Acidified Watershed at Bear Brook Watershed, Maine USA

The Bear Brook Watershed in Maine, USA is the site of a paired watershed study. West Bear (WB) catchment is being artificially acidified with 1,800 eq ha-1 y-1 of (NH4)2SO4. East Bear (EB) serves as the control. After six years of artificial acidification, volume-weighted concentrations in WB, normalized to EB, increased approximately as follows, in eq L-1 : H+, 15; Al (umoles), 50; Al (eq L-1), 100; Ca. 50; Mg. 20; Na, 10; K, 2; SO4, 120; NH4, 2; NO3, 80; HCO3 has decreased 10 eq L-1. Based on changing chemistry, several inferences can be made about soil-soil water interactions.1. Various combinations of cation pairs in stream waters from both catchments are significantly correlated on an annual basis. The strongest linear correlations (r2 typically greater than 0.5), with positive slopes, occur for Mg versus Ca. These relationships suggest soil-soil water equilibria of the type:Ca+2 + Mg-X = Mg+2 + Ca-X; KCa-Mg = ([Mg+2]/[Ca+2])/([Mg-X]/[Ca-X]) or, with assumptions:K'Ca-Mg = [Mg+2]/[Ca+2]The value of K'Ca-Mg remains relatively constant through time in both watersheds, except in WB in and after the fourth year of the manipulation of WB. Thereafter there is preferential depletion (Mg>Ca>na>K), primarily along shallow flow paths - thus altering the solid activity ratios of the exchange surfaces. In EB, base cation concentrations decline with increasing discharge (increasing H+), due to dilution and interaction with soils with lower base saturation. In WB the acidification reverses this relationship, perhaps partly because of displacement of cations by NH4 from the amendments. With progressive depletion of Ca and Mg in the quick-flow paths, concentrations start to decline at higher discharge, in spite of lower pH.2. Sulfate concentrations increased in WB to as high as 230 eq L-1 at high flow. The percentage of added SO4 leached to the stream increased to approximately 65% by the end of 1995. Thus, soils along base-flow paths adsorbed about 35% of the added SO4 in 1995.3. Aluminum concentrations in WB have increased from a pre-manipulation maximum of 10 mole/L at high flow to 60 mole/L. The relationship between Al and H+ is:Al = 0.13(H+)2 + 4.35which could result from either desorption or dissolution of Al to a 2+ specie. This relationship has been relatively constant through the manipulation. The Al/Ca molar ratio increased from pre-manipulation values of 0.1 to 0.3 to 0.8, at higher flow.4. The minimum pH in WB, achieved at highest flow, has decreased from about 5.3 to <4.7, an increase of about 15 eq H+ L-1. The increase in H+ has been approximately 2 eq L-1 yr-1. Neutralization of acidity has been initially accommodated by mobilization of Ca>Mg>Al>Na>K>H; by 1995 the neutralization involves the release of Al>Ca>Mg>NaH>K. Thus, the soils are inferred to (1) have reduced base saturation, (2) preferential proportional loss of mg over Ca, (3) increased SO4 saturation, and (4) higher exchangeable acidity.     

Methodological complexities of product carbon footprinting: a sensitivity analysis of key variables in a developing country context

Product carbon footprinting schemes adopt different analytical methodologies. The calculations can also be affected by limited data availability and uncertainty surrounding the value of key variables. The combination of these factors reduces the validity of comparing carbon footprints between products and countries.We used data from sugar production in Zambia and Mauritius to test how variations in methodology affected the product carbon footprint (PCF). We calculated a PCF according to PAS 2050 and explored the sensitivity of the results to the variation of key variables.Results showed that land use change emissions can dominate PCFs. The largest potential impact came from assuming global worst case data for land use change emissions where a product's origin is unknown (+1900%). The issue of land use change can lead to high carbon footprints for products from developing countries where more natural vegetation is still being converted and data are most lacking. When land use change is not important, variables such as electricity emission factors, capital inputs and loss of soil carbon had significant impacts on the PCF.This analysis highlights the large effect of methodology on PCFs. These results are of particular concern for developing countries where data are scarce and the use of global worst case data may be prescribed. We recommend the development of more precise emission factors for tropical countries and bio-regions, and encourage the transparent use of PCF methodologies, where data sources, uncertainties and variability are explicitly noted.     

Contribution of macroporosity to infiltration into a continuous corn no-tilled watershed: Implications for contaminant movement

Rainfall and runoff were measured for many years on small watersheds on 10–15% slopes in east-central Ohio. Surface runoff from watersheds used for corn (Zea mays L.) production was high with conventional tillage and very low with no-tillage. A 50-year storm produced 15 times more runoff from a plowed watershed than from a mulch-covered no-till watershed. Reduced runoff from the no-till surface resulted in increased percolation and enhanced the potential for transport of agricultural chemicals to the groundwater. The mulched surface of the no-till watershed also created a favorable environment for the deep burrowing earthworm, Lumbricus terrestris L., whose burrows can transmit water rapidly downward through the soil profile, thus contributing to the high infiltration rates.Open biopores and smaller structural pores were counted and measured to characterize the major flow paths of water movement in the no-till soil. Photos of horizontal surfaces at 2.5-, 7.5-, 15-, and 30 - cm depths and vertical faces of impregnated samples from the 1- and 5-cm depths were evaluated by image analysis. Number of pores was inversely proportional to pore diameter, however pores in the 0.05–1.0-mm diameter range accounted for less porosity than did those in the 1.0–5.0-mm range. The large pores were nearly vertical earthworm burrows and were continuously open from near the surface to the bedrock. Surface applications of lime increased subsoil pH in the no-till watershed but had little effect below the plow sole in the tilled watershed, suggesting that rapid movement of water in large pores can enhance chemical migration into the subsoil.     

An axenic plant culture system for optimal growth in long-term studies

The symbiotic co-evolution of plants and microbes leads to difficulties in understanding which of the two components is responsible for a given environmental response. Plant-microbe studies greatly benefit from the ability to grow plants in axenic (sterile) culture. Several studies have used axenic plant culture systems, but experimental procedures are often poorly documented, the plant growth environment is not optimal, and axenic conditions are not rigorously verified. We developed a unique axenic system using inert components that promotes plant health and can be kept sterile for at least 70 d. Crested wheatgrass (Agropyron cristatum cv. CDII) plants were grown in sand within flow-through glass columns that were positively pressured with filtered air. Plant health was optimized by regulating temperature, light level, CO2 concentration, humidity, and nutrients. The design incorporates several novel aspects, such as pretreatment of the sand with Fe, graduated sand layers to optimize the air-water balance of the root zone, and modification of a laminar flow hood to serve as a plant growth chamber. Adaptations of several sterile techniques were necessary for maintenance of axenic conditions. Axenic conditions were verified by plating and staining leachates as well as a rhizoplane stain. This system was designed to study nutrient and water stress effects on root exudates, but is useful for assessing a broad range of plant-microbe-environment interactions. Based on total organic C analysis, 74% of exudates was recovered in the leachate, 6% was recovered in the bulk sand, and 17% was recovered in the rhizosphere sand. Carbon in the leachate after 70 d reached 255 microg d(-1). Fumaric, malic, malonic, oxalic, and succinic acids were measured as components of the root exudates.     

Comparing decadal responses of whole-watershed manipulations at the Bear Brook and Fernow experiments

The Bear Brook Watershed in Maine (BBWM), USA, and the Fernow Experimental Forest in West Virginia, USA, represent unique, long-term, paired, whole watershed, experimental manipulations focusing on the effects of nitrogen (N) and sulfur (S) deposition on temperate forests. Both watersheds began whole-ecosystem additions of N and S as (NH₄)₂SO₄ in the fall of 1989, and both are entering their third decade of chronic enrichment of the treated watersheds, while the reference watersheds offer unique opportunities to evaluate forest watershed responses to recovery. Differences between BBWM and Fernow in the history of atmospheric deposition, soil properties, and forest composition all contribute to different response trajectories in stream chemical exports over time. The four watersheds represent a spectrum of N enrichment and retention, ranging from ≈98% N retention in the reference watershed in Maine, to ≈20% N retention in the treated watershed in West Virginia. Despite these differences, there is evidence that mechanisms of response in base cation leaching and other processes are similar among all four watersheds. In both cases, the history to date of two decades of research and monitoring has provided new insights into ecosystem response not evident in more traditional short-term research.     

Streamflow variability and hydroclimatic change at the Bear Brook Watershed in Maine (BBWM), USA

Seasonal variations in streamflow and the associated hydrologic extremes impart significant temporal structure to watershed-scale chemical fluxes. Consequently, a careful characterization of the episodic-to-seasonal and longer-term streamflow variations is a first step toward developing a comprehensive view of the temporal dynamics of watershed processes in a changing climate. Here we analyze a nearly two-decade-long streamflow record for the East Bear subwatershed within the Bear Brook Watershed in Maine (BBWM) (USA) to understand the envelope of streamflow variability by season, with a particular focus on the high flow events that have a disproportionately large impact on the biogeochemical processes and fluxes. Interannual and longer-term variations in a number of derived statistical metrics of hydrologic variability are examined. Our analysis shows substantial interannual and longer-term variability in seasonal flow volumes and peak flows. Furthermore, a long, unimpaired streamflow record for the Narraguagus River (a proximate watershed to the BBWM) is examined with a view to understand the relative coherence in hydrologic variability, as well as quantifying the decadal and longer-term hydrologic variations in this region. We find that the streamflow variability in the two watersheds shows similarity in all seasons. A moving window analysis to assess the changing flood potential over time indicates upward trends in the recent decades. Spring season (March–May) flood estimates show a near-monotonic trend over the 1949–2008 record. Finally, empirical relationships between streamflow and large-scale atmospheric circulation patterns highlight the regional and global climatic drivers of hydrologic extremes in this region, including impacts from remnants of Atlantic hurricanes.