Organic diagenesis in sediment and its impact on the adsorption of bisphenol A and nonylphenol onto marine sediment

Hydrophobic organic contaminants in marine water are mostly adsorbed onto (partitioned into) sediment organic matter (SOM). To study the impact of SOM diagenesis on sediment adsorption properties, artificial sediment with rich SOM content was incubated for more than 120. days. The sediment was sampled every week, and batch sediment adsorption tests were conducted with bisphenol A (BPA) and nonylphenol (NP) as the model pollutants. The results show that the amount of organic matter loaded in the sediment decreased by nearly 80% during incubation. For the incubated sediment, the BPA partition coefficient, Kd, decreased whereas the organic normalized partition coefficient, Koc, more than doubled. The experiments with NP show an even greater increase in Koc. Organic matter diagenesis shows a profound effect on the adsorption behavior of sediment, as the SOM residue has an increasing affinity and partition capacity for organic contaminants. © 2010 Elsevier Ltd.postprin

Regional and local contributions to ambient non-methane volatile organic compounds at a polluted rural/coastal site in Pearl River Delta, China

Identification of major sources of airborne pollutants and their contribution to pollutant loadings are critical in developing effective pollution control and mitigation strategies. In this study, a comprehensive dataset of non-methane volatile organic compounds (NMVOCs) collected from August 2001 to December 2002 at a polluted rural/coastal site in the Pearl River Delta (PRD) is analyzed to assess the relative contributions of major pollution sources to ambient NMVOC mixing ratios. A unique approach based on emission ratios of individual chemical species was used to classify the bulk air samples in order to apportion regional and local source contributions to the measured mixing ratios. The collected air samples fell into four major groups, including air masses from the inner PRD region and Hong Kong (HK) urban area. To estimate the source apportionment of NMVOCs, a principal component analysis/absolute principal component scores receptor model was applied to the classified data points. The results indicate that the regional and local source contributions to ambient NMVOC levels at the site were significantly different due to the differences in local versus regional energy use and industrial activities. For air masses originating from HK, vehicular emissions accounted for approximately 39% of the total NMVOC levels, followed by industrial emissions (35%), gasoline evaporation (14%) and commercial/domestic liquefied petroleum gas/natural gas use (12%). By contrast, for air masses originating from the PRD the industrial emissions accounted for 43% of the total NMVOC burden, followed by vehicular emissions (32%) and biomass burning (25%). In particular, the higher regional contribution of biomass burning found in this study as compared to existing emission inventories suggests that further efforts are necessary to refine the emission inventories of NMVOCs in the PRD region. © 2006 Elsevier Ltd. All rights reserved

Measurements of trace gases in the inflow of South China Sea background air and outflow of regional pollution at Tai O, Southern China

We present a 16-month record of ozone (O3), carbon monoxide (CO), total reactive nitrogen (NOy), sulphur dioxide (SO2), methane (CH4), C2 - C8 non-methane hydrocarbons (NMHCs), C1 - C2 halocarbons, and dimethyl sulfide (DMS) measured at a southern China coastal site. The study aimed to establish/update seasonal profiles of chemically active trace gases and pollution tracers in subtropical Asia and to characterize the composition of the 'background' atmosphere over the South China Sea (SCS) and of pollution outflow from the industrialized Pearl River Delta (PRD) region and southern China. Most of the measured trace gases of anthropogenic origin exhibited a winter maximum and a summer minimum, while O3 showed a maximum in autumn which is in contrast to the seasonal behavior of O3 in rural eastern China and in many mid-latitude remote locations in the western Pacific. The data were segregated into two groups representing the SCS background air and the outflow of regional continental pollution (PRD plus southern China), based on CO mixing ratios and meteorological conditions. NMHCs and halocarbon data were further analyzed to examine the relationships between their variability and atmospheric lifetime and to elucidate the extent of atmospheric processing in the sampled air parcels. The trace gas variability (S) versus lifetime (τ) relationship, defined by the power law, Slnx = Aτ-b, (where X is the trace gas mixing ratio) gives a fit parameter A of 1.39 and exponent b of 0.42 for SCS air, and A of 2.86 and b of 0.31 for the regional continental air masses. An examination of ln[n-butane]/ln[ethane] versus ln[propane]/ln[ethane] indicates that their relative abundance was dominated by mixing as opposed to photochemistry in both SCS and regional outflow air masses. The very low ratios of ethyne/CO, propane/ethane and toluene/benzene suggest that the SCS air mass has undergone intense atmospheric processing since these gases were released into the atmosphere. Compared to the results from other polluted rural sites and from urban areas, the large values of these species in the outflow of PRD/southern China suggest source(s) emitting higher levels of ethyne, benzene, and toluene, relative to light alkanes. These chemical characteristics could be unique indicators of anthropogenic emissions from southern China. © Springer Science + Business Media, Inc. 2005

Adsorption of tetracyclines on marine sediment during organic matter diagenesis

The effect of decomposition and diagenesis of sediment organic matter (SOM) on the adsorption of emerging pollutants by the sediment has been seldom addressed. In the present experimental study, artificial sediment was incubated to simulate the natural organic diagenesis process and hence investigate the influence of organic diagenesis on the adsorption of tetracyclines (TCs) by marine sediment. During a period of 4 months of incubation, SOM initially added into the sediment underwent biodegradation and diagenesis. The results showed an early decrease in TC adsorption by the sediment, which was likely caused by the competition between the microbial organic products and TC molecules for the adsorption sites. Afterward, TC adsorption by the sediment increased significantly, which was mainly due to the accumulation of condensed SOM. The experimental results indicate the interactions between TCs and the sediment during the dynamic process of SOM diagenesis. Moreover, the remaining SOM is shown to have an increasing affinity with the antibiotics.postprin

Intoeing gait in children

OBJECTIVE. To review the aetiology and management of intoeing. DATA SOURCES. Medline and non-Medline literature search, and personal experience. STUDY SELECTION. Studies that provided evidence-based information about the aetiology and management of paediatric intoeing gait were selected. DATA EXTRACTION. Data were extracted and reviewed independently by both authors. DATA SYNTHESIS. An intoeing gait affects many children and, as with flexible flatfoot, bowleg, and knock-knee, it falls into the category of physiological problems that occur in normal children. The usual causes are excessive femoral anteversion, internal tibial torsion, and metatarsus adductus. Management is based on understanding the causes and the natural course of the condition and the effectiveness of various treatment modalities. Unfortunately, due to poor understanding of the condition, intoeing is commonly overtreated with braces or special footwear. CONCLUSIONS. Intoeing is one of the most common conditions encountered in paediatric orthopaedic practice. It is important to make an early diagnosis of pathological causes of intoeing such as cerebral palsy and developmental dysplasia of the hips so that treatment can be commenced as soon as possible.published_or_final_versio

Source contributions to ambient VOCs and CO at a rural site in eastern China

Ambient data on volatile organic compounds (VOCs) and carbon monoxide (CO) obtained at a rural site in eastern China are analyzed to investigate the nature of emission sources and their relative contributions to ambient concentrations. A principal component analysis (PCA) showed that vehicle emissions and biofuel burning, biomass burning and industrial emissions were the major sources of VOCs and CO at the rural site. The source apportionments were then evaluated using an absolute principal component scores (APCS) technique combined with multiple linear regressions. The results indicated that 71%±5% (average±standard error) of the total VOC emissions were attributed to a combination of vehicle emissions and biofuel burning, and 7%±3% to gasoline evaporation and solvent emissions. Both biomass burning and industrial emissions contributed to 11%±1% and 11%±0.03% of the total VOC emissions, respectively. In addition, vehicle emissions and biomass and biofuel burning accounted for 96%±6% of the total CO emissions at the rural site, of which the biomass burning was responsible for 18%±3%. The results based on PCA/APCS are generally consistent with those from the emission inventory, although a larger relative contribution to CO from biomass burning is indicated from our analysis. © 2004 Elsevier Ltd. All rights reserved

Adsorption and desorption behaviors of selected endocrine disrupting chemicals in simulated gastrointestinal fluids

postprin

An error diffusion technique with reduced directional hysteresis

Author name used in this publication: K. T. LoAuthor name used in this publication: C. K. LiCentre of Digital Signal Processing for Multimedia Applications, Department of Electronic and Information EngineeringVersion of RecordPublishe

Human cardiac Kv4.3 channels are regulated by protein tyrosine kinases

Poster presentationpublished_or_final_versionThe 15th Annual Research Conference of the Department of Medicine, The University of Hong Kong, Hong Kong, 16 January 2010. In Hong Kong Medical Journal, 2010, v. 16, suppl. 1, p. 64, abstract no. 11

A multiscale error diffusion technique for digital halftoning with dot-overlap compensation

Author name used in this publication: C. K. LiVersion of RecordPublishe