Comparison of particulate mass, chemical species for urban, suburban and rural areas in central Taiwan, Taichung

Aerosol samples for PM2.5, PM(2.5-10) and TSP were collected from June to September 1998 and from February to March 1999 in central Taiwan. Ion chromatography was used to analyze the acidic anions: sulfate, nitrate and chloride in the Universal samples. The ratios of fine particle concentrations to coarse particle concentrations displayed that the fine particle concentrations are almost greater than that of coarse particle concentrations in Taichung area. The average concentrations of PM2.5, PM(2.5-10) and TSP in urban sites are higher than in suburban and rural sites at both daytime and night-time. Chloride dominated in the coarse mode in daytime and in fine mode in night-time. Nitrate can be found in both the coarse and fine modes. Sulfate dominated in fine mode in both daytime and night-time.     

Development of a risk assessment methodology for evaluating potential impacts associated with contaminated mud disposal in the marine environment

In order to assess impacts associated with disposal of contaminated mud arising from Hong Kong's dredging and reclamation projects, a methodology has been formulated to determine the level of risk posed by consumption of seafood/marine prey species to humans and to the Chinese White Dolphin (Sousa chinensis). This methodology improves on previously used techniques by incorporating risks for organic contaminants, accounting for doses from sources other than seafood, and incorporating additional local knowledge on Sousa chinensis behaviour. It thus represents an advance in risk assessment techniques and a new integration of risk assessment and monitoring in environmental management.     

Worshippers' exposure to particulate matter in two temples in Taiwan

Worshippers in temples may be exposed to high concentrations of pollutants emitted from incense burning. This work assessed the PM2.5 and PM10 exposures of temple worshippers in Taiwan and explored the important exposure determinants such as numbers of passing visitors and joss sticks in censers, worshipping dates, and temple characteristics. Sampling was conducted on the 1st, 2nd, 15th, and 16th of the lunar month in two temples in Taichung, Taiwan. Research staff took samples by wearing one PM2.5 and one PM10 sampler and imitating worshipping activity. Personal environmental monitors connected to personal pumps with 2-L/min flow rates were used for sampling. PM10 samples were also simultaneously taken outside the temples. The results suggested that burning joss sticks in temples is a significant PM exposure source. The geometric mean of personal exposure was 444 microg/m3 PM2.5 [geometric standard deviation (GSD) = 1.8] and 583 microg/m3 PM10 (GSD = 1.4). The latter was approximately 4-6 times that of roadside concentrations. Exposures on the 1st and 15th (with more visitors and more joss sticks) were about 130 microg/m3 PM2.5 and 249 microg/m3 PM10 higher than those on the 2nd and the 16th. Furthermore, each joss stick in the censer contributed about 0.40 microg/m3 of particles to the worshippers' exposure. In the worst case, PM exposure during one temple visit would account for 11% of the personal exposure in one day.     

The recovery of ammonia and hydrogen sulfide from ground-level area sources using dynamic isolation flux chambers: bench-scale studies

Controlled bench-scale laboratory experiments were conducted to evaluate the recovery of ammonia (NH3) and hydrogen sulfide (H2S) from dynamic isolation flux chambers. H2S (80-4000 ppb) and NH3 (5000-40,000 ppb) samples were diffused through the flux chamber to simulate ground level area source emissions while measuring the inlet and outlet flux chamber concentrations simultaneously. Results showed that the recovery of H2S during a 30-min sampling time was almost complete for concentrations >2000 ppb. At the lowest concentration of 80 ppb, 92.55% of the H2S could be recovered during the given sampling period. NH3 emissions exhibited similar behavior between concentrations of 5000-40,000 ppb. Within the 30-min sampling period, 92.62% of the 5000-ppb NH3 sample could be recovered. Complete recovery was achieved for concentrations >40,000 ppb. Predictive equations were developed for gas adsorption. From these equations, the maximum difference between chamber inlet and outlet concentrations of NH3 or H2S was predicted to be 7.5% at the lowest concentration used for either gas. In the calculation of emission factors for NH3 and H2S, no adsorption correction factor is recommended for concentrations >37,500 ppb and 2100 ppb for NH3 and H2S, respectively. The reported differences in outlet and inlet concentration above these ranges are outside the fullscale sensitivity of the gas sensing equipment. The use of 46-90 m of Teflon tubing with the flux chambers has apparently no effect on gas adsorption, because recovery was completed almost instantaneously at the beginning of the tests.     

Microbial transformation products of benzoxazolinone and benzoxazinone allelochemicals--a review

Cyclic hydroxamic acids and lactams are allelochemicals present in the common agricultural crops wheat, rye, and maize. The hydroxamic acids are mainly present in the plants as glucosides. Upon injury or insect attack or when exuded to the soil environment, the hydroxamic acids occur in their unstable agluconic form. In the first step in the transformation of hydroxamic acids, benzoxazolinones are formed spontaneously. It is necessary to elucidate the further microbial transformation of these compounds in the soil environment for a purposeful exploitation of the allelopathic properties of wheat, rye, and maize. In the present paper, the existing knowledge on microbial transformation products of benzoxazolin-2-one (BOA), 6-methoxy-benzoxazolin-2-one (MBOA), and 2-hydroxy-1,4-benzoxazin-3-one (HBOA) was reviewed. Three main groups of transformation products were identified: aminophenoxazinones, malonamic acids, and acetamides. Future research needs concerning the transformation of these chemicals in soil are discussed, when their properties for suppressing weeds and soil-borne diseases are going to be exploited.     

Comparing aquatic risk assessment methods for the photosynthesis-inhibiting herbicides metribuzin and metamitron

Three different risk assessment procedures are described that aim to protect freshwater habitats from risks of the photosynthesis-inhibiting herbicides metribuzin and metamitron. These procedures are (1) the first-tier approach, based on standard toxicity tests and the application of an assessment factor, (2) the Species Sensitivity Distribution (SSD) approach, based on laboratory tests with a wider array of species and the application of a statistical model to calculate the HCx (the Hazardous Concentration for x% of the species), and (3) the model ecosystem approach, based on the evaluation of treatment-related effects in field enclosures. A comparison of the risk assessment procedures reveals that the first-tier approach is the most conservative for metamitron and metribuzin, and that HC5 values (and even HC10 values) based on acute EC50 values of algae and aquatic vascular plants may be used to derive maximum permissible concentrations for single applications. For both compounds these HC5 values were very similar to the ecological threshold concentrations in the enclosure studies. In contrast to model ecosystem experiments, however, HCx values based on lab toxicity tests do not provide information on the recovery potential of sensitive endpoints and on indirect effects, which may be important for regulatory decision-making. In the enclosure study, indirect effects of metribuzin on invertebrate populations were observed at an exposure concentration that was approximately 20 times lower than the corresponding HC5 value based on lab toxicity data for aquatic invertebrates.     

Investigation of organic xenobiotic transfers,partitioning and processing in air-soil-plant systems using a microcosm apparatus. Part II: comparing the fate of chlorobenzenes in grass planted soil

A microcosm system was used to investigate and compare transfers of 14C labeled-1,2-dichlorobenzene (DCB), 1,2,4-trichlorobenzene (TCB) and hexachlorobenzene (HCB) in an air-soil-plant system using single grass tillers planted into spiked soil. This study was the second phase of a development investigation for eventual study of a range of xenobiotic pollutants. Recoveries from the system were excellent at >90%. The predominant loss pathway for 14C labeled-1,2-DCB and 1,2,4-TCB was volatilisation with 85% and 76% volatilisation of parent compound and volatile metabolites over 5 weeks respectively. Most of the added label in the hexachlorobenzene spiked system remained in soil. Mineralisation was <1% for all compounds. 14C plant burdens expressed as microg parent compound/g plant fresh weight were significant and suggest that plant uptake of chlorobenzenes from soil may be an important exposure pathway for grazing herbivores. Both shoot and root uptake of 14C was detected, with foliar uptake of volatilised compounds dominating shoot uptake, and being greatest in TCB spiked systems. The microcosm is shown as potentially an ideal system with which to investigate organic xenobiotic partitioning in air-soil-plant systems to improve understanding of the equilibria and kinetics of exchanges. However, limitations imposed by the lab based conditions must be recognized and data should be compared with field based data sets as a consequence.     

Distribution of organotin compounds in tissues of mussels Mytilus edulis and clams Mya arenaria

Concentrations and composition of butyltin (BT) and phenyltin (PT) compounds were compared in tissues of mussels Mytilus edulis and clams Mya arenaria collected from the Mersey Estuary. Tributyltin (TBT) concentrations were consistently highest in digestive gland and low in muscular tissues such as siphons (Mya) and adductor muscle (Mytilus). Lowest concentrations were found in the periostracum surrounding the siphons of Mya. Ratios of monobutyltin (MBT), dibutyltin (DBT) and TBT to total BT content of Mytilus tissues were in the ranges 25-34%, 21-28% and 44-51%, respectively. Much higher proportions of TBT:total BT were characteristic of Mya (>80% in the digestive gland, remaining tissue and gonad) implying that slow degradation rates account for the relatively high levels of TBT in this species. TPT was the only phenyltin compound detected (albeit at relatively low levels), and, like TBT, was present in highest concentrations in the digestive gland of clams--suggesting an important dietary component in the accumulation of OTs in these bivalves.     

Characterization of emissions of dioxins and furans from ethylene dichloride, vinyl chloride monomer and polyvinyl chloride facilities in the United States. Consolidated report

This is the consolidated report of emissions of PCDD/F from facilities in the organic chemical manufacturing chain leading to polyvinyl chloride. Data have been gathered from facilities in the US and Canada from a number of manufacturers and at various steps in the manufacturing process. Estimates of US emissions or transfers of PCDD/F were generated on an "Upper Bound" and "Most Likely" basis. The Most Likely estimate of US emissions of PCDD/F to the open environment, that is, air, water and land surface by facilities in this chain, based on evaluation of non-detects at one-half the detection limit is about 12 g I-TEQ per year. On this same basis, an estimated 19 g is disposed of in secure landfills.     

Mussel watch: a review of Cu and other metals in various marine organisms in Taiwan, 1991-98

This study presents the distribution of Cu, Zn, Pb, Cd, Hg and As in various marine organisms collected along the western coast of Taiwan from 1991 to 1998, and also evaluates the time variation of Cu in oysters before (1980-85) and after (1986-98) the "green oyster" incident. The results show that relatively high geometric mean (GM) concentrations of Cu, Zn, Pb, Cd, As and Hg were generally found in Crassostrea gigas (Cu=229 microg/g, Zn=783 microg/g), Gomphina aeguialtera (Pb=30.3 microg/g), Tegillarca granosa (Cd=2.85 microg/g), Thais clavigera (As=96.9 microg/g) and Parapenaeopsis cornuta (Hg=1.35 microg/g), respectively. Especially, maximum Cu and Zn concentrations (GM=229 and 783 microg/g, respectively) in oysters (C. gigas) from different culture areas were much higher than those of the other organisms by about 1.13-458 and 2.40-63.7 times, respectively. Similarly, rock-shells (Thais clavigera) had a high capacity for accumulating Cu (GM=202 microg/g) and Zn (GM=326 microg/g) under the same physico-chemical conditions. The highest GM Cu and Zn concentrations of 1108 (range from 113 to 2806) and 1567 (range from 303 to 3593) microg/g were obtained in oysters from the Hsiangshan coastal area, one of the most important oyster culture areas in Taiwan. However, the highest GM Cd and As concentrations of 6.82 and 19.3 microg/g were found in oysters from the Machu Islands. Mean Cu concentrations in the oysters from the Erhjin Chi estuary declined from 2194+/-212 microg/g in 1986-90 to 545 microg/g (GM) in 1991-96. In the Hsiganshan area, GM Cu concentrations of 909 microg/g (1991-96) and 1351 microg/g (1997-98) in oysters were significantly higher than those of 201 microg/g (1980-85) and 682 microg/g (1986-90). The gradually increasing levels of Cu and Zn in the oysters from the Hsiangshan area have been observed year by year.