Study on the quality and stability of compost through a Demo Compost Plant

This study is concerned with the performance of a Demo Compost Plant for the development of acceptable composting technology in Bangladesh. The Demo Compost Plant was setup at the adjacent area of an existing compost plant located at Khulna city in Bangladesh. Four different composting technologies were considered, where Municipal Solid Waste (MSW) were used as a raw material for composting, collected from the adjacent areas of the plant. Initially the whole composting system was conducted through two experimental setups. In the 1st setup three different types of aerators (horizontal and vertical passively aerator and forced aerator) were selected. For a necessary observation four piles, using only MSW as the input materials in the first three compost pile, the fourth one was the existing Samadhan’s compost pile. Based on the analysis of the experimental findings, the horizontal passively aerated composting technique is suitable for Bangladesh as it had better performance for reducing composting period than that of the others. It was being observed from the quality parameters of compost in the both 1st and 2nd setup that as the waste directly come from kitchen, degradation rate of waste shows a positive result for reducing this waste and there is no possibility of toxic contamination, when it would be used as a soil conditioner. Though there is no significant improvement in the quality of the final product in the 2nd setup as comparing with the 1st setup but it fulfills one of the main objectives of this study is to reduce the whole composting period as well as immediate management of the increasing amount of waste and reducing load on landfill. Selfheating tests reveal that degree of stability of compost with respect to maturation period was remained in the acceptable level, which was further accelerated due to the use of organic additives.     

Observation and simulation of net primary productivity in Qilian Mountain, western China

We modeled net primary productivity (NPP) at high spatial resolution using an advanced spaceborne thermal emission and reflection radiometer (ASTER) image of a Qilian Mountain study area using the boreal ecosystem productivity simulator (BEPS). Two key driving variables of the model, leaf area index (LAI) and land cover type, were derived from ASTER and moderate resolution imaging spectroradiometer (MODIS) data. Other spatially explicit inputs included daily meteorological data (radiation, precipitation, temperature, humidity), available soil water holding capacity (AWC), and forest biomass. NPP was estimated for coniferous forests and other land cover types in the study area. The result showed that NPP of coniferous forests in the study area was about 4.4 tCha(-1)y(-1). The correlation coefficient between the modeled NPP and ground measurements was 0.84, with a mean relative error of about 13.9%.     

Energy maximization by selective feeding on tissues of the venerid clam <Emphasis Type="Italic">Marcia hiantina</Emphasis> in the marine scavenger <Emphasis Type="Italic">Nassarius festivus</Emphasis> (Gastropoda: Nassariidae)

Feeding selectivity of the intertidal scavenging gastropod Nassarius festivus on four types of tissue (soft tissue, adductor muscle, foot, mantle margin) of the venerid clam Marcia hiantina was studied by field observations and laboratory experiments. Both approaches showed similar results with the soft tissue and adductor muscle being much preferred. As the energy content of the four types of tissue was similar and individuals of N. festivus rearing in different types of tissue obtained similar growth rates both in shell length and in body wet weight, differential consumption was most likely determined by the palatability of the tissues. Energy intake in a meal for N. festivus was estimated at 10.92, 9.17, 3.86 and 2.02 cal meal⁻¹ ind⁻¹ for soft tissue, adductor muscle, mantle margin, and foot, respectively. In view of the small size and sporadic distribution of the carrion, and intense competition among the conspecifics, selective feeding on more palatable tissues maximizes energy intake for scavengers like N. festivus.     

Evaluation of heavy metal contamination in Phaeozem of northeast China

Surface and profile Phaeozem soil samples from 31 locations affected by various anthropogenic activities such as mining, chemical manufacturing, traffic emission and pesticide application were collected in Heilongjiang Province and Jilin Province, northeast China. The range of total concentrations of four heavy metals Cd, Pb, Cu and Zn in the soil was 0.011–3.137, 10.31–62.34, 9.74–51.21 and 39.54–247.59 mg kg⁻¹, respectively, determined using the acidic digestion procedure. Four methods including single contamination evaluation, background concentration comparison, surface/subsurface concentration comparison and exchangeable fraction evaluation were used to evaluate the extent of metal contamination in Phaeozem. The results indicated that different activities increased the concentrations of the heavy metals in surface soils, where high concentrations of cadmium and lead were found close to chemical plants and in the suburbs of the investigated cities. The four methods showed a general trend of increased soil contamination with heavy metals. Cadmium was of the most concern compared with the other contaminated elements in the study area, due to the long-term phosphatic fertilizer utilization and industrial activities. The proper evaluation method for cadmium contamination was the background concentration comparison, while for zinc and copper was the single contaminative index evaluation. Cadmium and lead could be the potential environmental risk in the Phaeozem area based on the different evaluations.     

Effects of pH, organic acids, and inorganic ions on lead desorption from soils

The desorption characteristics of lead in two variable charge soils (one developed from Arenaceous rock (RAR) and the other derived from Quaternary red earths (REQ)) were studied, and the effects of pH value, organic acid, and competitive ions were examined. Desorption of Pb(2+) decreased from nearly 100.0 to 20.0% within pH 1.0-4.0 in both soils, and then the decrease diminished at pH > 4.0. Organic ligands at relatively low concentrations (< or =10(-3) mol L(-1)) slightly inhibited Pb(2+) desorption, but enhanced Pb(2+) desorption at higher concentrations. In this study, citric acid or acetic acid at higher concentrations (>10(-3) mol L(-1)) had the greatest improvement of Pb(2+) desorption, followed by malic acid; and the smallest was oxalic acid. Desorption of the adsorbed Pb(2+) increased greatly with increasing concentrations of added Cu(2+) or Zn(2+). Applied Cu(2+) increased Pb(2+) desorption more than Zn(2+) at the same loading.     

Arsenic speciation, and arsenic and phosphate distribution in arsenic hyperaccumulator Pteris vittata L. and non-hyperaccumulator Pteris ensiformis L

This study examined the roles of arsenic translocation and reduction, and P distribution in arsenic detoxification of Pteris vittata L. (Chinese Brake fern), an arsenic hyperaccumulator and Pteris ensiformis L. (Slender Brake fern), a non-arsenic hyperaccumulator. After growing in 20% Hoagland solution containing 0, 133 or 267 microM of sodium arsenate for 1, 5 or 10 d, the plants were separated into fronds, rhizomes, and roots. They were analyzed for biomass, and concentrations of arsenate (AsV), arsenite (AsIII) and phosphorus. Arsenic in the fronds of P. vittata was up to 20 times greater than that of P. ensiformis, yet showing no toxicity symptoms as did in P. ensiformis. While arsenic was concentrated primarily in the fronds of P. vittata as arsenite it was mainly concentrated in the roots of P. ensiformis as arsenate. Arsenic reduction in the plants took longer than 1-d. P. vittata maintained greater P in the roots while P. ensiformis in the fronds. The high arsenic tolerance of the hyperaccumulator P. vittata may be attributed to its ability to effectively reduce arsenate to arsenite in the fronds, translocate arsenic from the roots to fronds, and maintain a greater ratio of P/As in the roots.     

Characterization of major chemical components of fine particulate matter in North Carolina

This paper presents measurements of daily sampling of fine particulate matter (PM2.5) and its major chemical components at three urban and one rural locations in North Carolina during 2002. At both urban and rural sites, the major insoluble component of PM2.5 is organic matter, and the major soluble components are sulfate (SO4(2-)), ammonium (NH4(+)), and nitrate (NO3(-)). NH4(+) is neutralized mainly by SO4(2-) rather than by NO3(-), except in winter when SO4(2-) concentration is relatively low, whereas NO3(-) concentration is high. The equivalent ratio of NH4(+) to the sum of SO4(2-) and NO3(-) is < 1, suggesting that SO4(2-) and NO3(-) are not completely neutralized by NH4(+). At both rural and urban sites, SO4(2-) concentration displays a maximum in summer and a minimum in winter, whereas NO3(-) displays an opposite seasonal trend. Mass ratio of NO3(-) to SO4(2-) is consistently < 1 at all sites, suggesting that stationary source emissions may play an important role in PM2.5 formation in those areas. Organic carbon and elemental carbon are well correlated at three urban sites although they are poorly correlated at the agriculture site. Other than the daily samples, hourly samples were measured at one urban site. PM2.5 mass concentrations display a peak in early morning, and a second peak in late afternoon. Back trajectory analysis shows that air masses with lower PM2.5 mass content mainly originate from the marine environment or from a continental environment but with a strong subsidence from the upper troposphere. Air masses with high PM2.5 mass concentrations are largely from continental sources. Our study of fine particulate matter and its chemical composition in North Carolina provides crucial information that may be used to determine the efficacy of the new National Ambient Air Quality Standard (NAAQS) for PM fine. Moreover, the gas-to-particle conversion processes provide improved prediction of long-range transport of pollutants and air quality.     

Waste management with recourse: An inexact dynamic programming model containing fuzzy boundary intervals in objectives and constraints

The existing inexact optimization methods based on interval-parameter linear programming can hardly address problems where coefficients in objective functions are subject to dual uncertainties. In this study, a superiority–inferiority-based inexact fuzzy two-stage mixed-integer linear programming (SI-IFTMILP) model was developed for supporting municipal solid waste management under uncertainty. The developed SI-IFTMILP approach is capable of tackling dual uncertainties presented as fuzzy boundary intervals (FuBIs) in not only constraints, but also objective functions. Uncertainties expressed as a combination of intervals and random variables could also be explicitly reflected. An algorithm with high computational efficiency was provided to solve SI-IFTMILP. SI-IFTMILP was then applied to a long-term waste management case to demonstrate its applicability. Useful interval solutions were obtained. SI-IFTMILP could help generate dynamic facility-expansion and waste-allocation plans, as well as provide corrective actions when anticipated waste management plans are violated. It could also greatly reduce system-violation risk and enhance system robustness through examining two sets of penalties resulting from variations in fuzziness and randomness. Moreover, four possible alternative models were formulated to solve the same problem; solutions from them were then compared with those from SI-IFTMILP. The results indicate that SI-IFTMILP could provide more reliable solutions than the alternatives.     

Physiological mechanism of plant roots exposed to cadmium

Physiological experiments on plant roots exposed to cadmium were conducted on carrot and radish using a liquid culture and a pot experiment with a series of cadmium applications. Activities of four enzymes (catalase, peroxidase, polyphenol oxidase, superoxide dismutase), and concentrations of free proline and malonaldehyde in the roots of both plants were investigated. Results showed that the germination rate and growth of roots of both plants were inhibited at the concentration of 20 mg Cd/l, and the inhibition was increased with the increasing concentrations of cadmium, both in the liquid culture and in the pot experiment; activities of the four enzymes declined similarly in both species. The concentration of proline in roots reached the maximum when the application of cadmium was at the level of 20 mg/l in the liquid culture (or 20 mg/kg in soil), and then it declined slowly with the increasing concentration of cadmium. However, the reverse trend was observed for the concentration of malonaldehyde. All of bio-indicators measured here was quite sensitive to the addition of cadmium.     

Revegetation of lagoon ash using the legume species Acacia auriculiformis and Leucaena leucocephala

A greenhouse study was conducted to evaluate the potential use of two legume species, Acacia auriculiformis and Leucaena leucocephala for growth on ameliorated lagoon ash with or without nitrogen (N(2))-fixing bacteria inoculation. Even though amendments of 30% (w/w) vermiculite or with sewage sludge compost were added to improve the chemical and physical limitations of lagoon ash, significant suppressions in biomass and plant nutrient content were found with ameliorated lagoon ash in comparison to an agricultural soil. The high proportion of clay-sized (<53 microm) ash particles limited root growth. In addition, heavy metal toxicity was a possible factor contributing to poor seedling growth. Higher plant productivity resulted from the sewage sludge compost-amended lagoon ash than with vermiculite due to a greater contribution of plant nutrients in the compost. Nodulation was inhibited in ameliorated lagoon ash but not in agricultural soil. High pH and electrical conductivity and elevated toxic metals may be important parameters that limit bacterial activity. Both species showed potential to establish on amended lagoon ash, with Acacia auriculiformis being the best adapted.