Paul Lam
City University of Hong Kong, Department of Biology and Chemistry, Faculty Member
Wastewater treatment plants (WWTPs) are a significant source for poly-/perfluoroalkyl substances (PFASs) entering the environment. The presence of PFASs in twenty-eight municipal WWTPs from eleven cites in economically developed areas of... more
Wastewater treatment plants (WWTPs) are a significant source for poly-/perfluoroalkyl substances (PFASs) entering the environment. The presence of PFASs in twenty-eight municipal WWTPs from eleven cites in economically developed areas of China were screened. Overall, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) were dominant in wastewater and sludge, and were not effectively removed during wastewater treatment. Elevated influent concentration ratios of perfluorobutanoic acid (PFBA) to PFOA and perfluorobutane sulfonate (PFBS) to PFOS in some WWTPs suggested that short chains substitution were adopted in these cities. Cluster analysis showed treatment processes had important impacts on PFASs profiles in effluent and sludge. Average concentration of total PFCAs in influent from each city and its gross domestic product (GDP) had significant positive correlation. This study provides a snapshot of both domestic and industrial discharges of PFAS to WWTPs as well ...
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The widespread distribution of perfluorinated chemicals (PFCs) in different environmental matrices has prompted concern about the sources, fate, and transport of these classes of chemicals. PFCs are present in the atmosphere, but only a... more
The widespread distribution of perfluorinated chemicals (PFCs) in different environmental matrices has prompted concern about the sources, fate, and transport of these classes of chemicals. PFCs are present in the atmosphere, but only a few studies have investigated their occurrence in precipitation. In this study, concentrations of 20 PFCs, including C3-C5 short-chain PFCs, were quantified using HPLC-MS/MS in precipitation samples from Japan (n = 31), the United States (n = 12), China (n = 5), India (n = 2), and France (n = 2). Among the PFCs measured, perfluoropropanoic acid (PFPrA) was detected in all of the precipitation samples. Average total PFC concentrations ranged from 1.40 to 18.1 ng/L for the seven cities studied. The greatest total PFC concentrations were detected in Tsukuba, Japan, whereas the lowest concentrations were detected in Patna, India. PFPrA, perfluorooctanoic acid (PFOA), and perfluorononanoic acid (PFNA) were found to be the dominant PFCs in Japanese and U.S. precipitation samples. No observable seasonal trend was found in precipitation samples from two locations in Japan. Annual fluxes of PFCs were estimated for Japan and the U.S. and the evidence for precipitation as an effective scavenger of PFCs in the atmosphere is reported.
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The native silver perch Bidyanus bidyanus has good potential as an aquaculture species in Australia. Juvenile of this species (1.14-2.13 g) were reared in glass aquaria at room temperatures (18-20 C). Fish were kept individually in... more
The native silver perch Bidyanus bidyanus has good potential as an aquaculture species in Australia. Juvenile of this species (1.14-2.13 g) were reared in glass aquaria at room temperatures (18-20 C). Fish were kept individually in separate aquaria for the study of growth and solid waste production. In the first experiment, three commercial diets referred to as diet 1, diet 2 and diet 3 were offered to fish for four weeks in order to study the gain in weight and food conversion ratio. The gain in weight decreased in the order of fish fed diet 2> diet 1> diet 3 (P>0.005). In the second experiment, diets 2 and 1 were fed to fish for four weeks in order to study relationship between growth of fish and production of solid wastes (suspended and dissolved) in the culture system. Diet 2 resulted in slightly better gain in weight (P>0.05) and less solids production in comparison to diet 1.
During aquaculture operations waste are generated in the form of solids and soluble waste that may cause water pollution to the receiving waters. These wastes are uneaten food, faces, scales, and mucus (sold waste) and dissolved nutrients... more
During aquaculture operations waste are generated in the form of solids and soluble waste that may cause water pollution to the receiving waters. These wastes are uneaten food, faces, scales, and mucus (sold waste) and dissolved nutrients (soluble waste). The two most important nutrients incorporated in fish food are the nitrogen and phosphorus essential for biological growth of fish but an abundance of these nutrients could cause algal blooms or eutrophication in natural waters. It is imperative that the digestive and metabolic wastes are reduced to a minimum so that aquaculture can be an environmentally sustainable development programme. Our research shows that growing of fish at optimum temperature may reduce the solid and nutrient load to the environment.
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Photodegradation in the absence of externally added chemicals could be an attractive solution for the removal of perfluorooctane sulfonate (PFOS) in aqueous environment, but the low decomposition rate presents a severe challenge and the... more
Photodegradation in the absence of externally added chemicals could be an attractive solution for the removal of perfluorooctane sulfonate (PFOS) in aqueous environment, but the low decomposition rate presents a severe challenge and the underlying mechanisms are unclear. In this study, we demonstrated that PFOS could be effectively degraded in a catalyst-free aqueous solution via a reduction route. Under appropriate pH and temperature conditions, a rapid PFOS photodegradation, with a pseudo-first-order decomposition rate constant of 0.91 h(-1), was achieved. In addition, hydrated electrons were considered to be the major photo-generated reductive species responsible for PFOS photodegradation in this system. Its production and reduction ability could be significantly affected by the environmental conditions such as pH, temperature and presence of oxidative species. This study gives insights into the PFOS photodegradation process and may provide useful information for developing catal...
Organophosphate flame retardants are emerging environmental contaminants, although knowledge of their health risks is limited. Here, thyroid hormone homeostasis and neuronal development was studied in the progeny of adult zebrafish... more
Organophosphate flame retardants are emerging environmental contaminants, although knowledge of their health risks is limited. Here, thyroid hormone homeostasis and neuronal development was studied in the progeny of adult zebrafish exposed to tris (1, 3-dichloro-2-propyl) phosphate (TDCPP). Adult zebrafish were exposed to TDCPP (0, 4, 20, and 100 μg/L) for 3 months. Increased generation of reactive oxygen species and reduced survival rates was observed in exposed F1 larvae. We also observed a significant decrease in plasma thyroxine and 3,5,3´-triiodothyronine levels in F0 females and F1 eggs/larvae. The mRNA and protein expression of factors associated with neuronal development (e.g. α1-tubulin, myelin basic protein, and synapsin IIa) were significantly downregulated in exposed F1 larvae, as was the level of the neurotransmitters dopamine, serotonin, gamma amino butyric acid and histamine. Larval locomotion was significantly decreased in exposed fish, but there was no effect on ace...
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Research Interests: Engineering, Geography, Water, Nonparametric Statistics, Developing Countries, and 22 moreEcology, Environmental Monitoring, Risk assessment, Japan, Ethiopia, Hong Kong, Multidisciplinary, Biological Sciences, DDT, Lakes, Heavy metals, Environmental Sciences, Humans, Animals, Hazardous Materials, Tandem Mass Spectrometry, Seawater, High Pressure Liquid Chromatography, CHEMICAL SCIENCES, Fresh water, Risk Assessment, and Geologic Sediments
There is increasing concern that certain chemicals in the aquatic environment can disrupt endocrine systems, leading to reproductive impairment and threatening survival of wild populations of invertebrates, fish, bird, reptiles, and... more
There is increasing concern that certain chemicals in the aquatic environment can disrupt endocrine systems, leading to reproductive impairment and threatening survival of wild populations of invertebrates, fish, bird, reptiles, and wildlife. For the first time, we report that hypoxia is also an endocrine disruptor and poses a significant threat to the reproduction and hence sustainability of fish populations. Serum levels of testosterone, estradiol, and triiodothyronine significantly decreased in carp (Cyprinus carpio) upon chronic exposure to hypoxia. These hormonal changes were associated with retarded gonadal development in both male and female carp, reduced spawning success, sperm motility, fertilization success, hatching rate, and larval survival, indicating that adverse effects of hypoxia on reproductive performance resulted from endocrine disruption. Since aquatic hypoxia commonly occurs over thousands of square kilometers in aquatic systems worldwide, our results imply that...
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The effects of two oil dispersants (Vecom B-1425 GL and Norchem OSD-570) mixed with diesel oil on the survival and behaviour of the stage II nauplii of the barnacle Balanus amphitrite were investigated. The24 and 48-hour LC50 values for... more
The effects of two oil dispersants (Vecom B-1425 GL and Norchem OSD-570) mixed with diesel oil on the survival and behaviour of the stage II nauplii of the barnacle Balanus amphitrite were investigated. The24 and 48-hour LC50 values for Vecom B-1425 GL:diesel mixture were 514 and 48 mg l−1 respectively, while respective values for Norchem OSD-570:diesel mixture were 505 and
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Research Interests: Ecotoxicology, Reproduction, Trace Metals, Risk assessment, Hong Kong, and 17 moreBiological Sciences, Heavy metals, Environmental Sciences, Copper, Probabilistic Risk Assessment, Birds, Female, Animals, Male, Chromium, Zinc, Iron, Probabilistic Analysis, CHEMICAL SCIENCES, Feathers, Risk Assessment, and Breeding Success
The thermal decomposition behavior of coal gangue, peanut shell, wheat straw and their blends during combustion were determined via thermogravimetric analysis. The coal gangue/agricultural biomass blends were prepared in four weight... more
The thermal decomposition behavior of coal gangue, peanut shell, wheat straw and their blends during combustion were determined via thermogravimetric analysis. The coal gangue/agricultural biomass blends were prepared in four weight ratios and oxidized under dynamic conditions from room temperature to 1000 °C by various heating rates. Kinetic models were carried out to evaluate the thermal reactivity. The overall mass balance was performed to assess the partition behavior of coal gangue, peanut shell and their blends during combustion in a fixed bed reactor. The decomposition processes of agricultural biomass included evaporation, release of volatile matter and combustion as well as char oxidation. The thermal reactivity of coal gangue could be improved through the addition of agricultural biomass in suitable proportion and subsequent appropriate heating rate during combustion. In combination with the heating value and base/acid ratio limitations, a blending ratio of 30% agricultural biomass is conservatively selected as optimum blending.
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Organic ultraviolet (UV) filters are applied widely in personal care products (PCPs), but the distribution and risks of these compounds in the marine environment are not well known. In this study, the occurrence and removal efficiencies... more
Organic ultraviolet (UV) filters are applied widely in personal care products (PCPs), but the distribution and risks of these compounds in the marine environment are not well known. In this study, the occurrence and removal efficiencies of 12 organic UV filters in five wastewater treatment plants (WWTPs) equipped with different treatment levels in Hong Kong, South China, were investigated during one year and a preliminary environmental risk assessment was carried out. Using a newly developed simultaneous multiclass quantification liquid chromatography-tandem mass spectrometry (LC-MS/MS) method, butyl methoxydibenzoylmethane (BMDM), 2,4-dihydroxybenzophenone (BP-1), benzophenone-3 (BP-3), benzophenone-4 (BP-4) and 2-ethyl-hexyl-4-trimethoxycinnamate (EHMC) were frequently (≥80%) detected in both influent and effluent with mean concentrations ranging from 23 to 1290 ng/L and 18-1018 ng/L, respectively; less than 2% of samples contained levels greater than 1000 ng/L. Higher concentrati...
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Tris(1,3-dichloro-2-propyl) phosphate (TDCPP) is an organophosphate flame retardant that is detectable in the environment and biota, prompting concern over its risk to wildlife and human health. Our objective was to investigate whether... more
Tris(1,3-dichloro-2-propyl) phosphate (TDCPP) is an organophosphate flame retardant that is detectable in the environment and biota, prompting concern over its risk to wildlife and human health. Our objective was to investigate whether long-term exposure to low concentrations of TDCPP can affect fish reproduction. Zebrafish embryos were exposed to low concentrations (0, 4, 20 and 100μg/L) of TDCPP from 2h post-fertilization until sexual maturation. Exposure to TDCPP significantly increased plasma estradiol and testosterone levels in females, but had no effect in males. TDCPP exposure also caused a significant reduction in fecundity as indicated by decreased egg production. Real-time PCR was performed to examine selected genes in the hypothalamic-pituitary-gonadal (HPG) axis and liver. Principle component analysis (PCA) showed that sex hormone levels and fecundity were related to the mRNA level of several genes in the HPG axis. Furthermore, hepatic vitellogenin (vtg1 and vtg3) expres...
Research Interests: Aquatic Toxicology, Fertility, Biological Sciences, Environmental Sciences, Liver, and 14 moreEndocrine disruptors, Hypothalamus, Female, Animals, Male, CHEMICAL SCIENCES, Pituitary Gland, The Endocrine System Function, Zebrafish, Endocrine Disruptors, Organophosphates, Gonads, Gene Expression Regulation, and Flame Retardants
Organofluorous compounds have been developed for myriad purposes in a variety of fields, including manufacturing, industry, agriculture, and medicine. The widespread use and application of these compounds has led to increasing concern... more
Organofluorous compounds have been developed for myriad purposes in a variety of fields, including manufacturing, industry, agriculture, and medicine. The widespread use and application of these compounds has led to increasing concern about their potential ecological toxicity, particularly because of the stability of the C-F bond, which can result in chemical persistence in the environment. This chapter reviews the chemical properties and ecotoxicology of four groups of organofluorous compounds: fluorinated refrigerants and propellants, per- and polyfluorinated compounds (PFCs), fluorinated pesticides, and fluoroquinolone antibiotics. These groups vary in their environmental fate and partitioning, but each raises concern in terms of ecological risk on both the regional and global scale, particularly those compounds with long environmental half-lives. Further research on the occurrence and toxicities of many of these compounds is needed for a more comprehensive understanding of their ecological effects.
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The fish food and faeces were fractioned into the differentcomponents of phosphorus and nitrogen. There was a rapid release ofphosphorus from the fish food and faeces and a decrease thereafterwhereas ammonium release was slow at first... more
The fish food and faeces were fractioned into the differentcomponents of phosphorus and nitrogen. There was a rapid release ofphosphorus from the fish food and faeces and a decrease thereafterwhereas ammonium release was slow at first with the rate increasingwith time. Both temperature and pH affected the release of nutrientsfrom fish food and faeces. The release of phosphorus and nitrogen
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ABSTRACT Silver perch, Bidyanus bidyanus (Mitchell 1838), were reared in glass aquaria and fed on three diets containing 53%, 45% and 36% protein, and 1.31%, 1.16% and 1.28% phosphorus, respectively, in order to investigate the phosphorus... more
ABSTRACT Silver perch, Bidyanus bidyanus (Mitchell 1838), were reared in glass aquaria and fed on three diets containing 53%, 45% and 36% protein, and 1.31%, 1.16% and 1.28% phosphorus, respectively, in order to investigate the phosphorus losses and phosphorus retention at 25 and 30 degrees C. The main path of phosphorus loss was found to be via faeces and was significantly higher at 30 degrees C (P < 0.05). There was a sharp increase in orthophosphate excretion soon after meals, which decreased linearly during the remaining 24 h. The daily orthophosphate output was observed to increase at the higher temperature and was significantly higher at 30 degrees C compared to 25 degrees C (P < 0.05). Phosphorus retention by silver perch was significantly better at 25 degrees C than at 30 degrees C (P < 0.05)
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Research Interests: Water, Reproduction, Risk assessment, Hong Kong, Multidisciplinary, and 14 moreInsecticides, Survival, Probability Distribution & Applications, Probabilistic Risk Assessment, Birds, Female, Animals, Male, Eggs, Dose Response Relationship, Probabilistic Risk Analysis, Risk Assessment, Breeding Success, and Environmental Exposure
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The toxicities and uptake mechanisms of two hepatotoxins, namely cylindrospermopsin and lophyrotomin, were investigated on primary rat hepatocytes by using microcystin-LR (a well-known hepatotoxin produced by cyanobacteria) as a... more
The toxicities and uptake mechanisms of two hepatotoxins, namely cylindrospermopsin and lophyrotomin, were investigated on primary rat hepatocytes by using microcystin-LR (a well-known hepatotoxin produced by cyanobacteria) as a comparison. Isolated rat hepatocytes were incubated with different concentrations of hepatotoxins for 0, 24, 48 and 72 h. The cell viability was assayed by the tetrazolium-based (MTT) assay. Microcystin-LR, cylindrospermopsin and lophyrotomin all exhibited toxic effects on the primary rat hepatocytes with 72-h LC(50) of 8, 40 and 560 ng/ml, respectively. The involvement of the bile acid transport system in the hepatotoxin-induced toxicities was tested in the presence of two bile acids, cholate and taurocholate. Results showed that the bile acid transport system was responsible for the uptake, and facilitated the subsequent toxicities of lophyrotomin on hepatocytes. This occurred to a much lesser extent with cylindrospermopsin. With its smaller molecular weight, passive diffusion might be one of the possible mechanisms for cylindrospermopsin uptake into hepatocytes. This was supported by incubating a permanent cell line, KB (devoid of bile acid transport system), with cylindrospermopsin which showed cytotoxic effects. No inhibition of protein phosphatase 2A by cylindrospermopsin or lophyrotomin was found. This indicated that other toxic mechanisms besides protein phosphatase inhibition were producing the toxicities of cylindrospermopsin and lophyrotomin, and that they were unlikely to be potential tumor promoters.
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Arsenic has been classified as a human carcinogen based on epidemiological data however the mechanism of its carcinogenicity is still unclear. Urinary biomarkers for chronic arsenic exposure would be valuable as an early warning indicator... more
Arsenic has been classified as a human carcinogen based on epidemiological data however the mechanism of its carcinogenicity is still unclear. Urinary biomarkers for chronic arsenic exposure would be valuable as an early warning indicator for timely interventions. In this study, young female C57Bl/6J mice were given drinking water containing 0, 100, 250 and 500 microg Asv/L as sodium arsenate ad libitum for 12 months. Urine was collected bimonthly for urinary arsenic methylation assay and porphyrin analysis. All detectable arsenic species showed strong linear correlation with administered dosage and the arsenic methylation patterns were similar in all three treatment groups. No significant changes of methylation patterns were observed over time for either the control or test groups. Urinary coproporphyrin III was significantly increased in the 8th month in 250 and 500 microg/L groups and remained significantly dose-related after 10 and 12 months. Coproporphyrin I also showed a significant dose-response relationship after 12 months. Our results confirm that urinary arsenic is a useful biomarker for internal dose. The alteration of porphyrin profile suggests that arsenic can affect the heme metabolism and this may occur prior to the onset of arsenic induced carcinogenesis.