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11.
Analysis of pollutant levels in central Hong Kong applying neural network method with particle swarm optimization 总被引:6,自引:0,他引:6
Air pollution has emerged as an imminent issue in modernsociety. Prediction of pollutant levels is an importantresearch topic in atmospheric environment today. For fulfillingsuch prediction, the use of neural network (NN), and inparticular the multi-layer perceptrons, has presented to be acost-effective technique superior to traditional statisticalmethods. But their training, usually with back-propagation (BP)algorithm or other gradient algorithms, is often with certaindrawbacks, such as: 1) very slow convergence, and 2) easilygetting stuck in a local minimum. In this paper, a newlydeveloped method, particle swarm optimization (PSO) model, isadopted to train perceptrons, to predict pollutant levels, andas a result, a PSO-based neural network approach is presented. The approach is demonstrated to be feasible and effective bypredicting some real air-quality problems. 相似文献
12.
Current status and research on E-waste issues in Asia 总被引:2,自引:1,他引:2
Atsushi Terazono Shinsuke Murakami Naoya Abe Bulent Inanc Yuichi Moriguchi Shin-ichi Sakai Michikazu Kojima Aya Yoshida Jinhui Li Jianxin Yang Ming H. Wong Amit Jain In-Suk Kim Genandrialine L. Peralta Chun-Chao Lin Thumrongrut Mungcharoen Eric Williams 《Journal of Material Cycles and Waste Management》2006,8(1):1-12
Rapid economic growth in Asia and the increasing transboundary movement of secondary resources will increasingly require both
3R endeavors (reduce, reuse, recycle) in each country and appropriate control of international material cycles. Recently,
managing electrical and electronic waste (E-waste) has become an important target for domestic and international material
cycles from the viewpoints of environmental preservation and resource utilization efficiency. To understand the current status
of E-waste issues in the context of international material cycles and to discuss the future tasks related to achieving 3R
in the region, we organized the National Institute for Environmental Studies (NIES) E-waste Workshop in December 2004. This
article reviews past studies on E-waste and briefly describes the topics presented and discussions held at the workshop. The
topics at the workshop included E-waste generation, recycling systems, international trade, and environmental impacts. In
addition, we discussed various issues such as terminology, current environmental concerns, and possible solutions. Transboundary
shipments of E-waste should be conducted taking into consideration the concept of sustainable development. The direction of
future research and possible collaborations are also discussed. 相似文献
13.
The purpose of this review is to describe the various aspects of pressure-sensitive adhesives prepared from natural rubber.
Pressure-sensitive adhesives (PSAs) adhere instantaneously to a variety of surfaces upon application of slight pressure and
can be obtained using different technologies. PSAs are materials that develop tack for low pressures and short contact times.
There are number of factors affecting the adhesion property of natural rubber based pressure-sensitive adhesives. In this
review, factors affecting adhesion property such as tack, peel and shear are examined in light of their relevance to adhesion
in addition to measurement methods of each of the three major adhesion properties. This review paper covers the work being
carried out from the last 20 years in the field of natural rubber based pressure sensitive adhesives. 相似文献
14.
An ecological survey was carried out to determine the sediment concentrations of nutrients and heavy metals and bioaccumulation of heavy metals in fish and shrimp including tilapia (Oreochromis mossambicus×O. nilotica), grey mullet (Mugil cephalus), gei wai shrimp (Metapenaeus ensis) and caridean shrimp (Macrobrachium nipponensis) in the traditional tidal shrimp ponds (gei wais) of Mai Po Nature Reserve, Hong Kong. The sediments collected from the landward sites contained higher nutrient contents, as well as zinc (Zn), chromium (Cr), copper (Cu), nickel (Ni) and cadmium (Cd) than those collected from the seaward sites, but vice versa for lead (Pb) and mercury (Hg). However, the concentrations of all metals were exceptionally high in the two sites located outside the reserve, suggesting that waters from Deep Bay might be the possible source of metal contamination affecting the reserve. All metals studied seemed to accumulate in the viscera of fish. Body size was the determining factor for the accumulation of heavy metals in caridean shrimp and gei wai shrimp but not fish. Concentrations of the metals studied in tissues of grey mullet and gei wai shrimp were found to be safe for human consumption. Concentrations of Cr in tilapia whole body (0.68–1.10 mg kg−1 wet weight) were close to or over the guideline value of 1 mg kg−1 set by the Food Adulteration (Metallic Contamination) Regulations of Hong Kong. Tilapia flesh and small caridean shrimp collected from gei wais were contaminated by Cr and Pb but still fit for human consumption. Caution is required if large caridean shrimp is to be consumed in large amounts continuously because the concentration of Pb exceeded the maximum permitted concentration (6 mg kg−1). The rather high Cr concentrations in tilapia whole body should not be overlooked as the fish will serve as a food source for migratory birds visiting the site. 相似文献
15.
Identification of soil heavy metal sources from anthropogenic activities and pollution assessment of Fuyang County, China 总被引:4,自引:0,他引:4
Zhang XY Lin FF Wong MT Feng XL Wang K 《Environmental monitoring and assessment》2009,154(1-4):439-449
Understanding regional variations of soil heavy metals and their anthropogenic influence are very important for environmental planning. In this study, 286 surface soil samples were collected in Fuyang county, and the 'total' metals for copper (Cu), zinc (Zn), lead (Pb), cadmium (Cd) and nickel (Ni) were measured in 2005. Statistic analysis showed that Cu, Zn, Pb and Cd had been added by exterior factors, and Ni was mainly controlled by natural factors. The combination of multivariate statistical and geostatistical analysis successfully grouped three groups (Cu, Zn and Pb; Cd; and Ni) of heavy metals from different sources. Through pollution evaluation, it was found that 15.76% of the study area for Cu, Zn and Pb, and 46.14% for Cd suffered from moderate or severe pollution. Further spatial analysis identified the limestone mining activities, paper mills, cement factory and metallurgic activities were the main sources for the concentration of Cu, Zn, Pb and Cd in soils, and soil Ni was mainly determined by the parent materials. 相似文献
16.
Use of Microbial Community to Evaluate Performance of a Wetland System in Treating Pb/Zn Mine Drainage 总被引:2,自引:0,他引:2
The performance of a wetland system in treating lead (Pb)/zinc (Zn) mine drainage was evaluated by using the polyurethane
foam unit (PFU) microbial community (method), which has been adopted by China as a standardized procedure for monitoring water
quality. The wetland system consisted of four cells with three dominant plants: Typha latifolia, Phragmites australis and Paspalum distichum. Physicochemical characteristics [pH, EC, content of total suspended solid (TSS) and metals (Pb, Zn, Cd, and Cu)] and PFU
microbial community in water samples had been investigated from seven sampling sites. The results indicated that the concentrations
of Pb, Zn, Cd, Cu, and TSS in the mine drainage were gradually reduced from the inlet to the outlet of the wetland system
and 99%, 98%, 75%, 83%, and 68% of these metals and TSS respectively, had been reduced in concentration after the drainage
passed through the wetland system. A total of 105 protozoan species were identified, the number of protozoa species and the
diversity index (DI) gradually increased, while the heterotrophic index (HI) gradually decreased from the inlet to the outlet
of the wetland system. The results indicated that DI, HI, and total number species of protozoa could be used as biological
indicators indicating the improvement of water quality. 相似文献
17.
Variations between rice cultivars in root secretion of organic acids and the relationship with plant cadmium uptake 总被引:13,自引:0,他引:13
To attempt to understand certain mechanisms causing the variations between rice cultivars with regard to Cd uptake and accumulation,
pot soil experiments were conducted with two rice cultivars at different levels of Cd, i.e., 0 (the control), 10, 50 mg Cd
kg−1 soil. The two rice cultivars differ significantly with regard to Cd uptake and accumulation. Root secretions of low-molecular-weight
organic acids (LMWOA) for each treatment were measured with ion chromatography. The results showed that LMWOA concentrations
in the soil planted with Shan you 63 (a high soil Cd accumulator) were all higher than those in the soil planted with Wu yun jing 7 (low soil Cd accumulator) at different soil Cd levels, although the magnitudes of the differences varied for individual LMWOA
and depend on soil Cd concentrations. For all six LMWOA, there were significant differences at P < 0.05 or < 0.01 levels for soils treated with 10 and 50 mg kg−1 Cd. The magnitude of the differences was greater under soil Cd treatments, especially at relatively low levels (for example,
10 mg Cd kg−1 soil), than in the control. Acetic acid and formic acid constituted more than 96% of the total concentration of the six LMWOA,
while citric acid constituted only about 0.1%. The rice cultivar with higher concentrations of LMWOA in soil accumulated more
Cd in the plants. The results indicate that LMWOA secretion by rice root, especially in Cd-contaminated soils, is likely to
be one of the mechanisms determining the plant Cd uptake properties of rice cultivars. 相似文献
18.
Accumulation of lead, zinc, copper and cadmium by 12 wetland plant species thriving in metal-contaminated sites in China 总被引:32,自引:0,他引:32
The concentrations of lead, zinc, copper and cadmium accumulated by 12 emergent-rooted wetland plant species including different populations of Leersia hexandra, Juncus effusus and Equisetum ramosisti were investigated in field conditions of China. The results showed that metal accumulation by wetland plants differed among species, populations and tissues. Populations grown in substrata with elevated metals contained significantly higher metals in plants. Metals accumulated by wetland plants were mostly distributed in root tissues, suggesting that an exclusion strategy for metal tolerance widely exists in them. That some species/populations could accumulate relatively high metal concentrations (far above the toxic concentration to plants) in their shoots indicates that internal detoxification metal tolerance mechanism(s) are also included. The factors affecting metal accumulation by wetland plants include metal concentrations, pH, and nutrient status in substrata. Mostly concentrations of Pb and Cu in both aboveground and underground tissues of the plants were significantly positively related to their total and/or DTPA-extractable fractions in substrata while negatively to soil N and P, respectively. The potential use of these wetland plants in phytoremediation is also discussed. 相似文献
19.
Shiping Zhou Changqun Duan Wong Hang Gi Michelle Fazhong Yang Xuehua Wang 《环境科学学报(英文版)》2011,23(4):676-680
Toxicities were assessed for a pyrethroid (cypermethrin) and an organophosphate insecticide (chlorpyrifos) individually and in
combination. A series of tests were conducted on di erent responses (acute, chronic, behavioral) of earthworms of species Eisenia
fetida andrei in the ecological risk assessment of these pesticides. The results showed that the toxicity of the mixture of cypermethrin
and chlorpyrifos was significantly higher than either of these pesticides individually, especially on the earthworm’s chronic responses.
At a concentration of 5 mg/kg, the mixture caused significant reductions on the growth and reproduction rates of earthworms, but did
not cause any significant e ect when the individual was tested. The increase in toxicity of the pesticide mixture means that the use of
toxicity data obtained exclusively from single-pesticide experiments may underestimate the ecological risk of pesticides that actually
present in the field. 相似文献
20.
Soil Lead and Other Metal Levels in Industrial, Residential and Nature Reserve Areas in Singapore 总被引:4,自引:0,他引:4
C. Y. Zhou M. K. Wong L. L. Koh Y. C. Wee 《Environmental monitoring and assessment》1997,44(1-3):605-615
The use of pressure feedback microwave digestion technique has permitted rapid and efficient digestion of soil and sediment samples. The evaluation of different acid mixtures to digest soil samples were studied by mixed-level orthogonal array design. The selected acid mixture of HCl-HNO3-HF was employed in the survey of Pb, Zn, Cu, Cr and Mn in soil samples. Surface soil samples were collected from industrial, residential and nature reserve areas in Singapore. The five metal concentrations were determined by flame atomic absorption spectrometry and graphite furnace atomic absorption spectrometry. The lead and other metal contents in NBS SRM 1645, NIES CRM No. 2 and NRCC BCSS-1 sediment standard references were determined concurrently with the survey samples. Five measured metal loading on the surface soils was in the order: industrial area > residential area > nature reserve area. The trace metal concentrations in surface soil from areas of heavy traffic are higher than those from residential areas. The main sources of trace metal pollution are vehicular exhaust and industrial activities. 相似文献