A comparison of CH4, N2O and CO2 emissions from three different cover types in a municipal solid waste landfill

High-density polyethylene (HDPE) membranes are commonly used as a cover component in sanitary landfills, although only limited evaluations of its effect on greenhouse gas (GHG) emissions have been completed. In this study, field GHG emission were investigated at the Dongbu landfill, using three different cover systems: HDPE covering; no covering, on the working face; and a novel material-Oreezyme Waste Cover (OWC) material as a trial material. Results showed that the HDPE membrane achieved a high CH₄ retention, 99.8% (CH₄ mean flux of 12 mg C m^-2 h^-1) compared with the air-permeable OWC surface (CH4 mean flux of 5933 mg C m^-2 h^-1) of the same landfill age. Fresh waste at the working face emitted a large fraction of N₂O, with average fluxes of 10 mg N m^-2 h^-2, while N₂O emissions were small at both the HDPE and the OWC sections. At the OWC section, CH₄ emissions were elevated under high air temperatures but decreased as landfill age increased. N₂O emissions from the working face had a significant negative correlation with air temperature, with peak values in winter. A massive presence of CO₂ was observed at both the working face and the OWC sections. Most importantly, the annual GHG emissions were 4.9 Gg yr^-1 in CO₂ equivalents for the landfill site, of which the OWC-covered section contributed the most CH₄ (41.9%), while the working face contributed the most N₂O (97.2%). HDPE membrane is therefore, a recommended cover material for GHG control.

Implications: Monitoring of GHG emissions at three different cover types in a municipal solid waste landfill during a 1-year period showed that the working face was a hotspot of N₂O, which should draw attention. High CH₄ fluxes occurred on the permeable surface covering a 1- to 2-year-old landfill. In contrast, the high-density polyethylene (HDPE) membrane achieved high CH₄ retention, and therefore is a recommended cover material for GHG control.     

Formation and Removal Reactions of Hazardous Air Pollutants

Current regulatory policies for hazardous air pollutants (HAPs) target the sources of direct emissions. In addition to direct emissions, some of the aromatic, nitrogenated, and oxygenated HAPs can be formed in the atmosphere. Formaldehyde and acetaldehyde, in particular, are produced by almost every hydrocarbon photooxidation reaction. Estimates have been made that, in some urban areas, in situ formation contributes as much as 85 percent of the ambient levels of formaldehyde and 95 percent for acetaldehyde. Over 40 percent of the HAPs being regulated under Title III of the 1990 Clean Air Act Amendments have atmospheric lifetimes of less than one day. The transformation products of these HAPs with low atmospheric persistence are important for assessing risks to human health, especially for cases where the transformation products are more toxic than the HAP itself.     

An environmental sustainability based budget allocation system for regional water quality management

A budget allocation system for regional water quality management to achieve environmental sustainability was developed in this study to assist a local authority with making appropriate budget allocations for improving Regional Water Environmental Sustainability (RWES) in an efficient manner. The system consists of visions and goals, RWES indicators, and an analysis of budget allocation versus RWES. Visions and goals define task priorities for improving water environmental sustainability. Indicators are used to measure the progress of related tasks toward RWES goals. These indicators are classified by the Driving Force-State-Response (DSR) framework to facilitate the analysis of relationships among indicators. Linkages between budget allocation and indicators are also analyzed, and the result is used to assess whether the available budget is allocated properly to raise the RWES. The applicability of the system is demonstrated by a case study involving a local environmental protection authority.     

Evaluation of biological stability and corrosion potential in drinking water distribution systems: a case study

The appearance of assimilable organic carbon (AOC), microbial regrowth, disinfection by-products (DBPs), and pipe corrosion in drinking water distribution systems are among those major safe drinking water issues in many countries. The water distribution system of Cheng-Ching Lake Water Treatment Plant (CCLWTP) was selected in this study to evaluate the: (1) fate and transport of AOC, DBPs [e.g., trihalomethanes (THMs), haloacetic acids (HAAs)], and other organic carbon indicators in the selected distribution system, (2) correlations between AOC (or DBPs) and major water quality parameters [e.g. dissolved oxygen (DO), free residual chlorine, and bacteria, and (3) causes and significance of corrosion problems of the water pipes in this system. In this study, seasonal water samples were collected from 13 representative locations in the distribution system for analyses of AOC, DBPs, and other water quality indicators. Results indicate that residual free chlorine concentrations in the distribution system met the drinking water standards (0.2 to 1 mg l(-1)) established by Taiwan Environmental Protection Administration (TEPA). Results show that AOC measurements correlated positively with total organic carbon (TOC) and UV-254 (an organic indicator) values in this system. Moreover, AOC concentrations at some locations were higher than the 50 microg acetate-C l(-1) standard established by Taiwan Water Company. This indicates that the microbial regrowth might be a potential water quality problem in this system. Higher DO measurements (>5.7 mg l(-1)) might cause the aerobic biodegradation of THMs and HAAs in the system, and thus, low THMs (<0.035 mg l(-1)) and HAAs (<0.019 mg l(-1)) concentrations were observed at all sampling locations. Results from the observed negative Langelier Saturation Index (LSI) values, higher Ryznar Stability Index (RSI) values, and high Fe3+ concentrations at some pipe-end locations indicate that highly oxidative and corrosive conditions occurred. This reveals that pipe replacement should be considered at these locations. These findings would be helpful in managing the water distribution system for maintaining a safe drinking water quality.     

Bisphenol A occurred in Kao-Pin River and its tributaries in Taiwan

Bisphenol A (BPA), one of the endocrine-disrupting chemicals, was detected in water collected from Kao-Pin River and its tributaries. Results indicated that 59% of the water samples contained BPA. Concentrations ranged from less than the limit of detection (LOD, 0.037) to 4.23 μg/L. The mean concentrations were 0.16, 0.20, 1.02, 1.30, and 0.30 μg/L for sampling sites S1, S2, S3, S4, and S5, respectively. Concentrations were not significantly different between high and low-flow periods in sites S2, S3, and S4. In site S1, concentrations in the high-flow period were significantly greater than during the lower flow period, and in site S5, BPA concentration in the low-flow period was significantly greater than in the high-flow period. The BPA mass flow rate in site S5 was greater in the high-flow period than in the low-flow period.     

Detrital flows through the feeding pathway of the oyster (Crassostrea gigas) in a tropical shallow lagoon: δ13C signals

The spatial relationships and linkage of the detrital flows among the water column, the sediment and the oyster Crassostrea gigas cultured in the water column were examined by using stable carbon isotopes (δ¹³C) in a tropical shallow lagoon from October 1996 to June 1997. The lagoon is located in southwestern Taiwan and is isolated from the sea by sand barriers except at two tidal inlets. It receives freshwater mainly from two rivers. A total of 12 stations were set up along three transect lines, each running across the lagoon from riverine to tidal inlet localities. The δ¹³C values of the water-column POM exhibited a marked sea–river gradient, with values depleted from a high of −21.7‰ at seaward stations to a low of −28.2‰ at riverine stations; those in the sedimentary POM (<62 μm grain size) also revealed this trend, but to a lesser extent. Oysters of two known ages, 6 months old (“old oysters”) and newly settled individuals (“young oysters”), were transplanted from one station to each of the remaining stations, while some were left at the original station. Values of δ¹³C in the muscle of transplanted oysters changed in parallel with the sea–river gradient of δ¹³C in POM (decreasing from −16.0 to −18.5‰ in old oysters and from −16.8 to −21.9‰ in young ones). The spatial sea–river gradient of the oyster's δ¹³C is related not only to the distance between the site that the oyster inhabits and sea or riverine environment, but also to the tidal flow pattern that surrounds its feeding place. Although the δ¹³C value of the sedimentary POM was correlated with that of the water-column POM, the δ¹³C value of the oyster tissue was significantly correlated with that of the water-column POM, but not with that of the sedimentary POM. This suggests that the oyster feeds primarily on water-column rather than sedimentary POM. Received: 30 April 1999 / Accepted: 15 December 1999     

Effects of burnings of wax apple stubble and rice straw on polychlorinated dibenzo-p-dioxin and dibenzofuran concentrations in air and soil

Measurements of the concentrations of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were made in ambient air, ash, and soil impacted by the open burning of wax apple and rice straw residues. Measurements showed that the mean PCDD/F concentration (0.458 pg I-TEQ/Nm3; international toxicity equivalence) in air at two wax apple orchards during open burning increased markedly, -8.1 times higher than that (0.057 pg I-TEQ/Nm3); before open burning. In addition, the mean PCDD/F concentration (0.409 pg I-TEQ/Nm3) in ambient air at a rice straw field was 4.6 times higher than that (0.089 pg I-TEQ/Nm3) before open burning. After burning the residues of wax apple stubble and rice straw, the contents of PCDD/F in ashes were 1.393 and 1.568 ng I-TEQ/kg-ash, respectively, and the contents of PCDD/F in soil were 2.258 and 2.890 ng I-TEQ/kg-soil, respectively. Therefore, the turnover of soil with the ash after open burning over years will result in the accumulation of PCDD/Fs in farm soils.     

Distribution and accumulation of heavy metals in the sediments of Kaohsiung Harbor, Taiwan

The distribution, enrichment, and accumulation of heavy metals in the sediments, especially those at the vicinity of tributary estuaries of Kaohsiung Harbor, Taiwan were investigated. Sediment samples from six locations in the Kaohsiung Harbor were collected quarterly in the period from 2002 to 2005 and characterized for metal content (e.g., Hg, Pb, Cd, Cr, Cu, Zn and Al), water content, organic matter, total nitrogen, total phosphorous, total grease, and grain size. Results showed that metal concentrations varied from 0.58 mg kg(-1) for Cd to 596 mg kg(-1) for Zn. Metal concentrations at the vicinity of river mouths were higher than those at other locations. All heavy metals studied, except Cr, had relatively high enrichment factors and geo-accumulation indices in the estuaries. Moreover, metal concentrations correlated closely to the physical-chemical properties of the sediments, which strongly suggested the influence of industrial and municipal wastewaters discharged from the neighboring industrial parks and river basins. Results would help develop strategies for pollution control and sediment remediation of Kaohsiung Harbor.