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301.
Feng Y Shi G Wu J Wang Y Zhu T Dai S Pei Y 《Journal of the Air & Waste Management Association (1995)》2007,57(2):164-171
Particle-associated polycyclic aromatic hydrocarbon (PAH) concentrations were investigated at six sampling sites in the heating (February to March 2001) and nonheating (August to September 2001) periods in an industrial city in Northern China. Thirteen PAHs were measured. The total average concentrations (nanograms per meter cubed) of PAHs ranged between 78.93 and 214.63 during the heating period and from 31.48 to 102.26 in the nonheating period. Benzo(a)pyrene occurred at the highest level at a site near an industrial area but occurred at low concentrations far from the city center and industrial areas. In addition, ambient PAH profiles were studied. The five and six-ring species occurred in high fractions at the sampling site. By diagnostic ratio analysis, the major source at each sampling site in the city was coal combustion in the heating period; in the nonheating period, the major sources were relatively complex. Finally, the similarities among the six regions were assessed by principal component analysis, cluster analysis, and coefficient of divergence. These multivariate statistical analyses produced similar results, which agreed with the results from the diagnostic ratio analysis. 相似文献
302.
Zhu J Wu X Miller C Yu F Chen P Ruan R 《Journal of environmental science and health. Part. B》2007,42(4):393-401
In this paper, continuous production of hydrogen through fermentation with liquid swine manure as substrate was researched using a semi-continuously fed fermenter (8 L in total volume and 4 L in working volume). The pH and temperature for the fermenter were controlled at 5.3 +/- 0.1 and 35 +/- 1 degrees C, respectively, throughout the experiment. Three hydraulic retention times (16, 20, and 24 h) were investigated for their impact on the efficiency and performance of the fermenter in terms of hydrogen yields. The results indicate that hydraulic retention time (HRT) has a strong influence on the fermenter performance. An increasing HRT would increase the variation in hydrogen concentration in the offgas. To produce hydrogen with a fairly consistent concentration, the HRT of the fermenter should not exceed 16 h, which, however, did not appear to be short enough to control methanogenesis because the offgas still contained about 5% methane. When methane content in the offgas exceeded 2%, an inverse linear relationship between hydrogen and methane was observed with a correlation coefficient of 0.9699. To increase hydrogen content in the offgas, methane production has to be limited to below 2%. Also, keeping oxygen content in the fermenter below 1.5% would increase the hydrogen concentration to over 15%. The product to substrate ratio was found to be around 50% for the fermenter system studied, evidenced by the observation that for every 6 liters of manure fermented, 3 liters of pure hydrogen were produced, which was significant and encouraging. 相似文献
303.
Survey of heavy metal pollution and assessment of agricultural soil in Yangzhong district, Jiangsu Province, China 总被引:37,自引:0,他引:37
We investigated concentrations of Hg, Cd, Pb, Zn, Cu, As, Ni, and Cr in samples of soil, cereal, and vegetables from Yangzhong district, China. Compared to subsoils, the sampled topsoils are enriched in Hg, Cd, Cu, Pb, Zn, and As. High levels of Cd and Hg are observed in most agricultural soils. Concentrations of Cr and Ni show little spatial variation, and high Cu, Pb, and Zn contents correspond well to areas of urban development. High As contents are primarily recorded at the two ends of the sampled alluvion. The contents of Cd, Hg, and total organic carbon (TOC) increase gradually to maximum values in the upper parts of soil profiles, while Cr and Ni occur in low concentrations within sampled profiles. As, Pb, Cu, and Zn show patterns of slight enrichment within the surface layer. Compared to data obtained in 1990, Cd and Hg show increased concentrations in 2005; this is attributed to the long-term use of agrochemicals. Cr and Ni contents remained steady over this interval because they are derived from the weathering of parent material and subsequent pedogenesis. The measured As, Cu, Pb, and Zn contents show slight increases over time due to atmospheric deposition of material sourced from urban anthropogenic activity. Low concentrations of heavy metals are recorded in vegetables and cereals because the subalkaline environment of the soil limits their mobility. Although the heavy metal concentrations measured in this study do not pose a serious health risk, they do affect the quality of agricultural products. 相似文献
304.
Chuaybamroong P Cayse K Wu CY Lundgren DA 《Environmental monitoring and assessment》2007,128(1-3):421-430
Ambient aerosols were collected during 2000–2001 in Gainesville, Florida, using a micro-orifice uniform deposit impactor (MOUDI)
to study mass size distribution and carbon composition. A bimodal mass distribution was found in every sample with major peaks
for aerosols ranging from 0.32 to 0.56 μm, and 3.2 to 5.6 μm in diameter. The two distributions represent the fine mode (<2.5 μm)
and the coarse mode (>2.5 μm) of particle size. Averaged over all sites and seasons, coarse particles consisted of 15% carbon
while fine particles consisted of 22% carbon. Considerable variation was noted between winter and summer seasons. Smoke from
fireplaces in winter appeared to be an important factor for the carbon, especially the elemental carbon contribution. In summer,
organic carbon was more abundant. The maximum secondary organic carbon was also found in this season (7.0 μg m−3), and the concentration is between those observed in urban areas (15–20 μg m−3) and in rural areas (4–5 μg m−3). However, unlike in large cities where photochemical activity of anthropogenic emissions are determinants of carbon composition,
biogenic sources were likely the key factor in Gainesville. Other critical factors that affect the distribution, shape and
concentration were precipitation, brushfire and wind. 相似文献
305.
Dissipation of pentachlorophenol (PCP) in soil was investigated and the chemical relationships with soil properties were addressed. The results indicate that the dissipation of extractable PCP residues can be described using first-order kinetics equations, with a half-dissipation time (T(1/2)) ranging from 6.5 to 173.3d. The sharply different patterns of PCP dissipation in different soils were closely related to soil properties. Correlations of stepwise regression equations obtained were significant at 0.01 probability level between soil parameters and extractable PCP residues (R(2)=0.974**) as well as T(1/2) values (R(2)=0.882**). Using pH together with organic carbon content (OC) and soil particle size distribution, the dissipation dynamics of PCP in soil could be accurately predicted. 相似文献
306.
Wen-Cheng Liu Jan-Tai Kuo Chih-Chieh Young Ming-Ching Wu 《Environmental Modeling and Assessment》2007,12(3):201-211
Numerical models are often used to evaluate the potential impact of human alternation of natural water bodies and to help
the design of the alternation to mitigate its impacts. In the past decade, three-dimensional hydrodynamic and reactive transport
modeling has matured from a research subject to a practical analysis technology. This paper presents a practical study in
which a three-dimensional hydrodynamic and water quality model [hydrodynamic eutrophication model (HEM-3D)] was applied to
determine the optimal location for treated wastewater discharged from marine outfall system in the Keelung harbor and the
adjacent coastal sea. First, model validation was conducted with respect to surface elevation, current, and water quality
variables measured in the Keelung harbor station and its coastal sea. The overall performance of the model was in qualitative
agreement with the available field data. The model was then used to evaluate several scenarios of the locations from marine
outfall system. Based on model simulation results, a location at the northeast of Ho-Ping Island was recommended for adoption
because the environmental impact is smaller than any other alternative.
相似文献
Wen-Cheng LiuEmail: |
307.
The purpose of the research is to study the seasonal succession of protozoa community and the effect of water quality on the protozoa community to characterize biochemical processes occurring at a eutrophic Lake Donghu, a large shallow lake in Wuhan City, China. Samples of protozoa communities were obtained monthly at three stations by PFU (polyurethane foam unit) method over a year. Synchronously, water samples also were taken from the stations for the water chemical quality analysis. Six major variables were examined in a principal component analysis (PCA), which indicate the fast changes of water quality in this station I and less within-year variation and a comparatively stable water quality in stations II and III. The community data were analyzed using multivariate techniques, and we show that clusters are rather mixed and poorly separated, suggesting that the community structure is changing gradually, giving a slight merging of clusters form the summer to the autumn and the autumn to the winter. Canonical correspondence analysis (CCA) was used to infer the relationship between water quality variables and phytoplankton community structure, which changed substantially over the survey period. From the analysis of cluster and CCA, coupled by community pollution value (CPV), it is concluded that the key factors driving the change in protozoa community composition in Lake Donghu was water qualities rather than seasons. 相似文献
308.
Yu FC Chen CY Lin SC Lin YC Wu SY Cheung KW 《Environmental monitoring and assessment》2007,132(1-3):419-428
As the embodiment of human activities, the change of regional industrial structure is an essential driving factor of global
environmental change. Consequently, the research on the change of regional industrial structure and associated effects on
the environment is one of the key issues of researches on sustainable development, human–environment relationship, and regional
response to global environment change. However, compared to the flourish of researches on environmental impact assessment
of industrial departments, few studies have been conducted to assess the environmental impact of regional industrial structure.
In this study, based on a synthetic analysis of environmental disturbances of different industrial departments, the environmental
impact coefficient of industrial department associated with the index of environmental impact of industrial structure was
constructed, so as to make a quantitative assessment of environmental impact of the change of regional industrial structure.
And the results of the case study in Lijiang City, a rural region of China, have showed that there are two obvious changes
of industrial structure in the study area from 1992 to 2003, associated with a continuous decreasing of the index of environmental
impact of industrial structure, which indicated a positive environmental effects of the change of regional industrial structure. 相似文献
309.
Response of microcystis to copper stress: do phenotypes of microcystis make a difference in stress tolerance? 总被引:2,自引:0,他引:2
To elucidate the role of phenotype in stress-tolerant bloom-forming cyanobacterium Microcystis, two phenotypes of M. aeruginosa - unicellular and colonial strains were selected to investigate how they responded to copper stress. Flow cytometry (FCM) examination indicated that the percents of viable cells in unicellular and colonial Microcystis were 1.92-2.83% and 72.3-97.51%, respectively, under 0.25 mgl(-1) copper sulfate treatment for 24h. Upon exposure to 0.25 mgl(-1) copper sulfate, the activities of antioxidative enzyme, such as superoxide dismutase (SOD) and catalase (CAT), were significantly increased in colonial Microcystis compared to unicellular Microcystis. Meanwhile, the values of the photosynthetic parameters (F(v)/F(m), ETR(max), and oxygen evolution rate) decreased more rapidly in unicellular Microcystis than in colonial Microcystis. The results indicate that colonial Microcystis has a higher endurance to copper than unicellular Microcystis. This suggests that the efficient treatment concentration of copper sulfate as algaecides will be dependent on the phenotypes of Microcystis. 相似文献
310.
An experimental study on recolonization and succession of marine macrobenthos in defaunated sediment 总被引:3,自引:0,他引:3
Hypoxia/anoxia in coastal waters is a world wide problem which often results in mass mortality and defaunation of benthos.
In this study, field experiments were carried out to examine recolonization and succession of macrobenthic infauna in defaunated
sediments, and the time required for recovery from complete defaunation to a stable community. Trays (33 cm length × 25.5 cm
width × 11 cm depth) of defaunated sediment were exposed at the subtidal of a pristine site in subtropical Hong Kong. Temporal
changes of macrobenthic communities in defaunated sediment were analyzed by univariate and multivariate statistics, and compared
with those in undisturbed natural sediment at the same site. Initial colonization of macrobenthos occurred rapidly. A total
of 42 species was found, with an average of 258 animals per tray and 24 species per tray recorded in the first month. Abundance
showed a small peak (496 animals per tray) after 3 months, reached a sharp peak (1154 animals per tray) after 6 months, and
declined thereafter. Species number increased gradually, reached a maximum (68 species per tray) after 9 months, and then
decreased. Recolonization was predominantly contributed by larval settlement rather than adult migration. Temporal changes
in abundance, species number and diversity of the macrobenthic community in defaunated sediment resemble the spatial changes
along a decreasing pollution gradient previously defined by other authors. Results of this experiment suggest that newly available
sediment may allow more species to colonize (or coexist) than sediment pre-occupied by an established community. This is probably
due to less interspecific competition in the former habitat. No significant difference in abundance or species richness was
observed between defaunated and natural sediments after 15 months, suggesting that a stable community had been achieved, although
minor variations in species composition were still discernible between defaunated and natural sediments.
Received: 24 May 1999 / Accepted: 20 October 1999 相似文献