Quantifying the waste reduction potential of using prefabrication in building construction in Hong Kong

As Hong Kong is a compact city with limited available land and high land prices, the construction of high-rise buildings is prevalent. The construction industry produces a significant amount of building waste. In 2005, about 21.5 million tonnes of construction waste were generated, of which 11% was disposed of in landfills and 89% in public filling areas. At the present rate, Hong Kong will run out of both public filling areas and landfill space within the next decade. The government is taking action to tackle the problem, such as by introducing a construction waste landfill charge, and promoting prefabrication to reduce on-site waste generation. This paper reports an ongoing study on the use of prefabrication in buildings and its impact on waste reduction in Hong Kong. A questionnaire survey was administered to experienced professionals, and case studies of recently completed building projects were conducted. The results revealed that construction waste reduction is one of the major benefits when using prefabrication compared with conventional construction. The average wastage reduction level was about 52%. This implies that a wider use of prefabrication could considerably reduce construction waste generation in Hong Kong and alleviate the burdens associated with its management.     

Delimitation of arsenic-contaminated groundwater using risk-based indicator approaches around blackfoot disease hyperendemic areas of southern Taiwan

This work determined scopes of arsenic(As)-contaminated groundwater using risk-based indicator classification approaches in blackfoot disease hyperendemic areas of southern Taiwan. Indicator kriging was first used to establish a conditional cumulative distribution function at each cell. Three approaches--the p-quantile estimate, the E-type estimate and the minimization of the expected loss--were then adopted to delimit contaminated regions for a regulated standard of As concentrations in groundwater. According to a risk assessment model established in our previous research, the standard was set to 250 microg/l for aquacultural use, corresponding to the 77.1th percentile of observed concentrations. Misclassification risks and uncertainty were examined for the classification approaches. The analyzed results reveal that contaminated areas are the largest using the 0.771-quantile estimate, whereas they are the smallest using the minimization of the expected loss. Proportions of credible polluted areas with low risks to false positives maintain a constant, 12.9-13.2%, for the classification approaches. To reduce a great impact on human health, As-polluted groundwater should be strictly prohibited to cultivate fish in credible polluted zones and monitored persistently in polluted zones with high risks to false positives.     

Bioaccumulation of arsenic compounds in aquacultural clams (Meretrix lusoria) and assessment of potential carcinogenic risks to human health by ingestion

This study surveyed the total arsenic (As) and As species contents in clams (Meretrix lusoria) farmed in areas of hyperendemic blackfoot disease (BFD) in southwestern Taiwan. Total As and As species in sediment and pond water were also analyzed to examine the bioaccumulation of As in clams in their exposure environment. Moreover, potential carcinogenic risks associated with the ingestion of As in aquacultural clams were evaluated probabilistically. The average total As contents in medium-sized and small clams were 7.62 and 10.71 microg/g (dry wt), respectively. The content of the As species in this study was approximately 61% of the total As content. The other unquantified As species are possibly arsenocholine, arsenosugar and arsenolipid. The average ratios of inorganic As contents to total As contents in clams ranged from 12.3% to 14.0% which are much higher than that found in the farmed oyster (Crassostrea gigas), indicating that humans may expose to larger quantities of inorganic As by ingesting the same amount of clam as oyster. Using different ingestion rates derived by the average consumption method and the questionnaire method, the estimated risks to human health associated with consuming clams from the BFD area ranging from slightly to largely exceed the standard target risk. Based on the estimation of the TR model, a 0.18g/day-person of the safe ingestion rate of clams in the BFD region is recommended.     

A new alternative fuel for reduction of polycyclic aromatic hydrocarbon and particulate matter emissions from diesel engines

This study investigated the emissions of polycyclic aromatic hydrocarbons (PAHs), carcinogenic potential of PAH and particulate matter (PM), brake-specific fuel consumption (BSFC), and power from diesel engines under transient cycle testing of six test fuels: premium diesel fuel (PDF), B100 (100% palm biodiesel), B20 (20% palm biodiesel + 80% PDF), BP9505 (95% paraffinic fuel + 5% palm biodiesel), BP8020 (80% paraffinic fuel + 20% palm biodiesel), and BP100 (100% paraffinic fuel; Table 1). Experimental results indicated that B100, BP9505, BP8020, and BP100 were much safer when stored than PDF. However, we must use additives so that B100 and BP100 will not gel as quickly in a cold zone. Using B100, BP9505, and BP8020 instead of PDF reduced PM, THC, and CO emissions dramatically but increased CO2 slightly because of more complete combustion. The CO2-increased fraction of BP9505 was the lowest among test blends. Furthermore, using B100, B20, BP9505, and BP8020 as alternative fuels reduced total PAHs and total benzo[a]pyrene equivalent concentration (total BaPeq) emissions significantly. BP9505 had the lowest decreased fractions of power and torque and increased fraction of BSFC. These experimental results implied that BP9505 is feasible for traveling diesel vehicles. Moreover, paraffinic fuel will likely be a new alternative fuel in the future. Using BP9505 instead of PDF decreased PM (22.8%), THC (13.4%), CO (25.3%), total PAHs (88.9%), and total BaPeq (88.1%) emissions significantly.     

Simulating the temporal changes of OCP pollution in Hangzhou, China

A dynamic fugacity model was applied to simulate the changes of contents and transfer fluxes of hexachlorocyclohexane (HCHs) and dichloro-diphenyl-trichloroethane (DDTs) from 1950s in the environment of Hangzhou, China. The receptors are composed of air, surface water, soils, sediment and biota compartments. The model provides a method to combine loadings of HCHs and DDTs from various sources with a series of physical-chemical processes to estimate concentrations and transport fluxes of HCHs and DDTs. Model results suggested that the calculated concentrations were in line with the observed ones. The highest contents of HCH and DDT in the environment of study area were 523 t and 471 t before 1983, among which about 80.7% HCHs and 93.2% DDTs remained in the soil compartment. From 1984 to now, contents of HCHs and DDTs had decreased to about 0.07% and 0.40% of their highest amount (before 1983), and only about 0.001% and 0.014% will expect to be left in 2020 in the study area according to the model prediction. Before 1983, the main transfer fluxes of HCHs were deposition from air to soil, runoff from soil to water and diffusion from soil to air, but for DDTs the main transfer fluxes were deposition from air to soil and water, and transfer from water to sediment. From 1984 to now, runoff from soil to water and transfer from water to sediment became the dominant processes. Although a large amount of HCHs and DDTs had been applied to the study area, their residue levels in the soils were much lower than those in North China (had lesser HCHs and DDTs application than in South China) at present time, and close to other locations of South China (had similar HCHs and DDTs application level). It can be attributed to the high precipitation and temperature that enhances the processes of wet deposition, evaporation and degradation of OCPs. Sensitivities of the input parameters to the calculated concentrations were evaluated using coefficient-of-variation normalized sensitivity coefficients. The model was also subjected to uncertainty analyses using a Monte Carlo simulation.     

Estimation of acceptable mercury intake from fish in Taiwan

The US Food and Drug Administration (USFDA) and Environmental Protection Agency (USEPA) are advising women and young children to avoid eating fish that contain high levels of mercury (Hg). However in Taiwan, the annual Black Fin Tuna Festival encourages the public to consume fish. The aim of this study was to assess fish intake in relation to the health risks of mercury exposure and calculate the acceptable and safe intake of fish in children and women of childbearing age. From the Monte Carlo simulation, based on USEPA's reference dose (0.1 microgkg(-1)d(-1)), we found that 21.6%-24.3% and 45.6%-57.4% of the daily mercury dose estimates exceeded the reference dose for typical and high-seafood consumers. The acceptable ingestion rates are <50 g d(-1) (children) and 90.8 +/- 15.7 g d(-1) (women of childbearing). Sensitivity analysis suggests that Hg concentration in fish may be a key parameter to aid governments as they offer guidance for risk management.     

Dermal Insecticide Residues from Birds Inhabiting an Orchard

The US Environmental Protection Agency conducts risk assessments of insecticide applications to wild birds using a model that is limited to the dietary route of exposure. However, free-flying birds are also exposed to insecticides via the inhalation and dermal routes. We measured azinphos-methyl residues on the skin plus feathers and the feet of brown-headed cowbirds (Molothrus ater) in order to quantify dermal exposure to songbirds that entered and inhabited an apple (Malus x domestica) orchard following an insecticide application. Exposure to azinphos-methyl was measured by sampling birds from an aviary that was built around an apple tree. Birds sampled at 36 h and 7-day post-application were placed in the aviary within 1 h after the application whereas birds exposed for 3 days were released into the aviary 4-day post-application. Residues on vegetation and soil were also measured. Azinphos-methyl residues were detected from the skin plus feathers and the feet from all exposure periods. Our results underscore the importance of incorporating dermal exposure into avian pesticide risk assessments.     

Characterization of Rain and Roof Drainage Water Quality in Xanthi, Greece

Thirteen field campaigns were undertaken in the period from December 2, 2002 until September 1, 2004 to collect water samples in order to characterize the quality of rainfall and roof drainage in the city of Xanthi, a typical provincial city in Greece. In each campaign, water samples were collected from 10 representative sites in the city (in total 130 samples), representing areas of distinct land use and human activities (i.e., traffic volume, residence density and industrial activity). The water samples were analyzed according to drinking water criteria for total coliform (not detected), temperature (range: 0.9–20°C), pH (range: 3.6–11.4), alkalinity (range: 0–21.5 mg CaCO₃/L), nitrate (range: 0–2456 μg/L), ammonium (range: 0–2628 μg/L), sulfate (range: 0–0.5 mg/L), calcium (range: 259.1–3064 μeq/L), magnesium (range: 0.8–488.8 μeq/L), potassium (range: 0.0–110.6 μeq/L) and dissolved heavy metals (Fe, range: 0.01–0.18 mg/L; Mn, range: 0.01–0.09 mg/L; Zn, range: 0.01–0.54 mg/L; Cu, Cr and Ni, not detected). Pollutant concentrations were generally higher in roof drainage than in rainwater, but both were lower than drinking water standards. Dissolved heavy metal concentrations were generally higher in the areas of intensive human activities, such as roads with high traffic volume and densely populated residential areas. The satisfactory quality of rainwater, which results from this analysis, makes its use as grey water possible.     

Bioaccumulation of trace elements in omnivorous amphibian larvae: implications for amphibian health and contaminant transport

Despite the influence that amphibians have on the flow of energy and nutrients in ecological systems, the role that amphibians play in transporting contaminants through food webs has received very little attention. This study was undertaken to investigate bioaccumulation of trace elements in amphibians relative to other small aquatic organisms in a contaminated wetland. We collected bullfrog larvae (Rana catesbeiana) along with three other species of small vertebrates and four species of invertebrates from a site contaminated with a wide array of trace elements and analyzed them for trace element concentrations and stable nitrogen and carbon isotope composition. We found that amphibian larvae accumulated the highest concentrations of most trace elements, possibly due to their feeding ecology. These results suggest that omnivorous amphibian larvae can serve as a critical link for trace element trophic transfer. Their propensity to accumulate trace elements may have important implications for amphibian health in contaminated environments and should be further investigated.