Pub Date : 2023-06-30DOI: 10.4038/jnsfsr.v51i2.11123
T.M. Munasinghe, U. Premarathne, D. Weerasinghe
The Mannar Basin extends over 45,000 km2 off the western coast of Sri Lanka. It has evolved due to the multiphase rifting between Indo-Lanka landmasses during the Barremian-Paleocene time. The sediment thickness of the basin ranges from about 4 to 10 km. The northern part of the basin is a targeted area for hydrocarbon exploration in Sri Lanka. Though two natural gas discoveries were made in 2011, the basin remains a frontier due to lack of well penetration and 3D seismic coverage. As a result, the depositional features of sediment in the basin are little known. This study focuses on identifying paleo depositional features in the Albian and Aptian strata using 650 km2 3D seismic data from the Mannar Basin. Root Mean Square (RMS) amplitude was used to characterize the depositional features in three-time windows on IHS Kingdom software (v.8.3). The results show the existence of a multi-level paleo submarine fan system in the Albian and Aptian strata. They are located relatively close to the western coastline compared to the fan system in the Eocene strata. The deposition of this paleo submarine fan system has taken place in a shelf marine environment and has been influenced by relatively high sea levels during the Albian and Aptian compared to the relatively low sea levels in the Paleocene and Eocene.
{"title":"Identification of depositional features in the Albian and Aptian sections over the hydrocarbon exploration block M2 on the Mannar Basin, Sri Lanka","authors":"T.M. Munasinghe, U. Premarathne, D. Weerasinghe","doi":"10.4038/jnsfsr.v51i2.11123","DOIUrl":"https://doi.org/10.4038/jnsfsr.v51i2.11123","url":null,"abstract":"The Mannar Basin extends over 45,000 km2 off the western coast of Sri Lanka. It has evolved due to the multiphase rifting between Indo-Lanka landmasses during the Barremian-Paleocene time. The sediment thickness of the basin ranges from about 4 to 10 km. The northern part of the basin is a targeted area for hydrocarbon exploration in Sri Lanka. Though two natural gas discoveries were made in 2011, the basin remains a frontier due to lack of well penetration and 3D seismic coverage. As a result, the depositional features of sediment in the basin are little known. This study focuses on identifying paleo depositional features in the Albian and Aptian strata using 650 km2 3D seismic data from the Mannar Basin. Root Mean Square (RMS) amplitude was used to characterize the depositional features in three-time windows on IHS Kingdom software (v.8.3). The results show the existence of a multi-level paleo submarine fan system in the Albian and Aptian strata. They are located relatively close to the western coastline compared to the fan system in the Eocene strata. The deposition of this paleo submarine fan system has taken place in a shelf marine environment and has been influenced by relatively high sea levels during the Albian and Aptian compared to the relatively low sea levels in the Paleocene and Eocene.","PeriodicalId":17429,"journal":{"name":"Journal of the National Science Foundation of Sri Lanka","volume":" ","pages":""},"PeriodicalIF":0.5,"publicationDate":"2023-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48633286","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"综合性期刊","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-06-30DOI: 10.4038/jnsfsr.v51i2.11101
W. Wijesundara, Dayani Gunathilaka, S. K. Madarasinghe, J. Andrieu, G. Muthusankar, N. R. Kankanamge, K. Kodikara
The southern coastal zone of Sri Lanka has been subjected to a variety of natural and anthropogenic influences over the past three decades. Understanding impacts of such influences on Land Use Land Cover (LULC) is vital for proper management of the coastal zone. This study, therefore, focused on mapping the change/s in the distribution of selected LULC in the selected sites, Bundala, Galle, Kalametiya, and Hambantota of the southern coastal zone, over last 24 years using satellite imagery. LULC maps of nine classes (mangrove, inland vegetation, marsh and grass, sand, bare land, built-up, cultivation, water, and unclassified) were created by employing an on-screen digitization technique achieving an accuracy of >70%. Trend analysis and two-sample proportion tests were used for statistical analyses, whereas geometric calculations were used for descriptive analyses. The results showed the highest overall change in LULC in Kalametiya, followed by Hambantota, Galle, and Bundala. The changes in the LULC classes are mainly attributed to the conversion of water to mangroves, marsh and grass areas in Kalametiya, water to built-up areas in Hambantota, cultivations to built-up areas in Galle, and marsh and grass areas to bare lands in Bundala. The causes of LULC changes were site specific. Trend analyses indicate the least LULC changes in Bundala possibly by 2025. The study highlights the significance of taking into account geographical dislocations when considering and anticipating the potential impacts of development projects over broader extents.
{"title":"Spatial and temporal changes of land use land cover distribution in selected sites of the southern coastal zone of Sri Lanka","authors":"W. Wijesundara, Dayani Gunathilaka, S. K. Madarasinghe, J. Andrieu, G. Muthusankar, N. R. Kankanamge, K. Kodikara","doi":"10.4038/jnsfsr.v51i2.11101","DOIUrl":"https://doi.org/10.4038/jnsfsr.v51i2.11101","url":null,"abstract":"\u0000The southern coastal zone of Sri Lanka has been subjected to a variety of natural and anthropogenic influences over the past three decades. Understanding impacts of such influences on Land Use Land Cover (LULC) is vital for proper management of the coastal zone. This study, therefore, focused on mapping the change/s in the distribution of selected LULC in the selected sites, Bundala, Galle, Kalametiya, and Hambantota of the southern coastal zone, over last 24 years using satellite imagery. LULC maps of nine classes (mangrove, inland vegetation, marsh and grass, sand, bare land, built-up, cultivation, water, and unclassified) were created by employing an on-screen digitization technique achieving an accuracy of >70%. Trend analysis and two-sample proportion tests were used for statistical analyses, whereas geometric calculations were used for descriptive analyses. The results showed the highest overall change in LULC in Kalametiya, followed by Hambantota, Galle, and Bundala. The changes in the LULC classes are mainly attributed to the conversion of water to mangroves, marsh and grass areas in Kalametiya, water to built-up areas in Hambantota, cultivations to built-up areas in Galle, and marsh and grass areas to bare lands in Bundala. The causes of LULC changes were site specific. Trend analyses indicate the least LULC changes in Bundala possibly by 2025. The study highlights the significance of taking into account geographical dislocations when considering and anticipating the potential impacts of development projects over broader extents.\u0000 ","PeriodicalId":17429,"journal":{"name":"Journal of the National Science Foundation of Sri Lanka","volume":" ","pages":""},"PeriodicalIF":0.5,"publicationDate":"2023-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45886262","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"综合性期刊","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-06-30DOI: 10.4038/jnsfsr.v51i2.10713
H. Prasanna, M. D. K. L. Gunathilaka, H. Iz
Accurate long-term measurements of sea level are fundamental to evaluating coastal risks, such as the impact of sea-level rise on near-shore ecosystems, groundwater dynamics, and coastal flooding. This study examines sea-level variability at Colombo, Sri Lanka using satellite altimetry, tide gauge measurements separately and their conflated solution under a single model. Modelling of conflated satellite altimetry and tide gauge measurements shows a geocentric (absolute) local sea-level rise of 3.56 ± 0.32 mm/y without any signature of a uniform acceleration since 1981 at this locality. The measurements disclosed statistically significant periodic changes in sea level of luni-solar origin. The conflated model solution enabled the estimation of a statistically significant in-situ vertical land motion (0.58 ± 0.19 mm/yr) without the aid of global positioning measurements. The conflation model explains 98% of the sea-level variability, which makes it suitable for accurate seal level predictions for coastal risk assessments in Colombo, Sri Lanka.
{"title":"Sea level variability at Colombo, Sri Lanka, inferred from the conflation of satellite altimetry and tide gauge measurements","authors":"H. Prasanna, M. D. K. L. Gunathilaka, H. Iz","doi":"10.4038/jnsfsr.v51i2.10713","DOIUrl":"https://doi.org/10.4038/jnsfsr.v51i2.10713","url":null,"abstract":"Accurate long-term measurements of sea level are fundamental to evaluating coastal risks, such as the impact of sea-level rise on near-shore ecosystems, groundwater dynamics, and coastal flooding. This study examines sea-level variability at Colombo, Sri Lanka using satellite altimetry, tide gauge measurements separately and their conflated solution under a single model. Modelling of conflated satellite altimetry and tide gauge measurements shows a geocentric (absolute) local sea-level rise of 3.56 ± 0.32 mm/y without any signature of a uniform acceleration since 1981 at this locality. The measurements disclosed statistically significant periodic changes in sea level of luni-solar origin. The conflated model solution enabled the estimation of a statistically significant in-situ vertical land motion (0.58 ± 0.19 mm/yr) without the aid of global positioning measurements. The conflation model explains 98% of the sea-level variability, which makes it suitable for accurate seal level predictions for coastal risk assessments in Colombo, Sri Lanka.","PeriodicalId":17429,"journal":{"name":"Journal of the National Science Foundation of Sri Lanka","volume":" ","pages":""},"PeriodicalIF":0.5,"publicationDate":"2023-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45349445","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"综合性期刊","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-06-30DOI: 10.4038/jnsfsr.v51i2.10868
A. Fernando, S. Liyanage, A. Cooray
Fluoride is beneficial for human health only in a narrow concentration range. Over the years, many analytical techniques have been developed to quantify fluoride in a variety of sample matrices. In this research, fluoride concentrations of twenty (20) natural water samples determined by SPADNS (SPA) and Eriochrome Cyanine R (ECR) colorimetric methods were evaluated to ascertain whether these methods can produce comparable fluoride concentrations. According to the paired t test for comparing individual differences, the two datasets are different at 95% confidence level suggesting that the two analytical methods produce statistically different fluoride concentrations for the analysed water samples. The potential interferences of Al3+, Ca2+, and Mg2+ on the fluoride analysis was evaluated using 0.85 mg L-1 fluoride standard solutions spiked with various amount of the above-mentioned metal ions. The highest interference was observed with Al3+ ions, which underestimated the fluoride concentration by 26% and 23% for ECR and SPA methods respectively at 20.0 mg L-1 Al3+ concentrations. The minimum interference was observed for Ca2+ ions which underestimated the fluoride concentration by 8% and 7% for ECR and SPA methods respectively at 100.0 mg L-1 Ca2+ concentrations. Acid distillation resulted in the samples spiked with Ca2+ and Mg2+ ions in the range of 0.50 to 100.0 mg L-1 reaching the theoretical concentration of 0.85 mg L-1. Acid distillation also worked well for the Al3+- fortified samples, except for Al3+ concentration at 20 mgL-1. The efficiency of the acid distillation method was also tested with three (03) natural water samples. The fluoride concentration increased significantly after the acid distillation; however, even after the acid distillation, statistically comparable fluoride concentrations were not observed.
{"title":"Fluoride analysis in aqueous solutions - a comparison of two colorimetric methods","authors":"A. Fernando, S. Liyanage, A. Cooray","doi":"10.4038/jnsfsr.v51i2.10868","DOIUrl":"https://doi.org/10.4038/jnsfsr.v51i2.10868","url":null,"abstract":"\u0000Fluoride is beneficial for human health only in a narrow concentration range. Over the years, many analytical techniques have been developed to quantify fluoride in a variety of sample matrices. In this research, fluoride concentrations of twenty (20) natural water samples determined by SPADNS (SPA) and Eriochrome Cyanine R (ECR) colorimetric methods were evaluated to ascertain whether these methods can produce comparable fluoride concentrations. According to the paired t test for comparing individual differences, the two datasets are different at 95% confidence level suggesting that the two analytical methods produce statistically different fluoride concentrations for the analysed water samples. The potential interferences of Al3+, Ca2+, and Mg2+ on the fluoride analysis was evaluated using 0.85 mg L-1 fluoride standard solutions spiked with various amount of the above-mentioned metal ions. The highest interference was observed with Al3+ ions, which underestimated the fluoride concentration by 26% and 23% for ECR and SPA methods respectively at 20.0 mg L-1 Al3+ concentrations. The minimum interference was observed for Ca2+ ions which underestimated the fluoride concentration by 8% and 7% for ECR and SPA methods respectively at 100.0 mg L-1 Ca2+ concentrations. Acid distillation resulted in the samples spiked with Ca2+ and Mg2+ ions in the range of 0.50 to 100.0 mg L-1 reaching the theoretical concentration of 0.85 mg L-1. Acid distillation also worked well for the Al3+- fortified samples, except for Al3+ concentration at 20 mgL-1. The efficiency of the acid distillation method was also tested with three (03) natural water samples. The fluoride concentration increased significantly after the acid distillation; however, even after the acid distillation, statistically comparable fluoride concentrations were not observed.","PeriodicalId":17429,"journal":{"name":"Journal of the National Science Foundation of Sri Lanka","volume":" ","pages":""},"PeriodicalIF":0.5,"publicationDate":"2023-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49351680","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"综合性期刊","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-06-30DOI: 10.4038/jnsfsr.v51i2.10777
L. Somathilake
By discretising in space, a non-linear time fractional reaction-diffusion equations (TFRDEs) can be converted into a system of time-fractional differential equations (TFDEs). The full memory method (FMM) and short memory method (SMM) are well-established memory selection methods used in the time integration of TFDEs. The main drawbacks of FMM and SMM are higher computational cost and uncontrollable error respectively. The only way to increase the accuracy of SMM is by increasing short memory length which causes an increase in computational cost. Especially when we apply these two methods to integrate TFRDEs, we have to solve a large system of TFDEs. Therefore, the drawbacks of these two methods affect seriously, when these are applied to solve TFRDEs. This paper aims to investigate the accuracy and efficiency of the memory selection method, Exponentially Decreasing Random Memory Method (EDRMM), and compare it with FMM and SMM when these methods apply to integrate TFRDEs. Based on these three memory selection methods, three semi-implicit numerical schemes namely semiimplicit scheme with full memory method (SI-FMM), semi-implicit scheme with short memory method (SI-SMM), and semi-implicit scheme with exponentially decreasing random memory method (SI-EDRMM)) are proposed and the accuracy and CPU time (computational time (CT)) of these three numerical schemes are compared. To do this comparison, these three numerical schemes are applied to four TFRDEs whose exact solutions are known. Numerical experiments confirm that the accuracy and efficiency of the SI-EDRMM are better than that of SI-SMM and the efficiency of SI-EDRMM is higher than that of SI-FMM. Therefore, EDRMM is better than SMM and FMM for the integration of TFRDEs.
{"title":"Comparative analysis of three memory selection methods for time integration of Fractional Reaction-Diffusion Equations","authors":"L. Somathilake","doi":"10.4038/jnsfsr.v51i2.10777","DOIUrl":"https://doi.org/10.4038/jnsfsr.v51i2.10777","url":null,"abstract":"By discretising in space, a non-linear time fractional reaction-diffusion equations (TFRDEs) can be converted into a system of time-fractional differential equations (TFDEs). The full memory method (FMM) and short memory method (SMM) are well-established memory selection methods used in the time integration of TFDEs. The main drawbacks of FMM and SMM are higher computational cost and uncontrollable error respectively. The only way to increase the accuracy of SMM is by increasing short memory length which causes an increase in computational cost. Especially when we apply these two methods to integrate TFRDEs, we have to solve a large system of TFDEs. Therefore, the drawbacks of these two methods affect seriously, when these are applied to solve TFRDEs. This paper aims to investigate the accuracy and efficiency of the memory selection method, Exponentially Decreasing Random Memory Method (EDRMM), and compare it with FMM and SMM when these methods apply to integrate TFRDEs. Based on these three memory selection methods, three semi-implicit numerical schemes namely semiimplicit scheme with full memory method (SI-FMM), semi-implicit scheme with short memory method (SI-SMM), and semi-implicit scheme with exponentially decreasing random memory method (SI-EDRMM)) are proposed and the accuracy and CPU time (computational time (CT)) of these three numerical schemes are compared. To do this comparison, these three numerical schemes are applied to four TFRDEs whose exact solutions are known. Numerical experiments confirm that the accuracy and efficiency of the SI-EDRMM are better than that of SI-SMM and the efficiency of SI-EDRMM is higher than that of SI-FMM. Therefore, EDRMM is better than SMM and FMM for the integration of TFRDEs.","PeriodicalId":17429,"journal":{"name":"Journal of the National Science Foundation of Sri Lanka","volume":" ","pages":""},"PeriodicalIF":0.5,"publicationDate":"2023-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46301677","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"综合性期刊","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-06-30DOI: 10.4038/jnsfsr.v51i2.11127
M. Jayasinghe, M. Gunasekara, M. Perera, K. Karunarathna, G. U. Chandrasiri, I. Hewajulige
King coconut (Cocos nucifera var. aurantiaca) is a tropical nut with notable nutritional and medicinal values. King coconut water (KCW) and king coconut kernel (KCK) are sweet and refreshing. They undergo several changes during maturation. The objective of this study was to assess the physico-chemical changes of KCW and KCK with maturity. Three different maturity stages (6, 7, and 8 months) of the variety aurantica, known locally as ‘Nawasi Thembili’ were studied for several physico-chemical parameters. Whole nut weight (g), nut-circumference (cm), colour (water/kernel) (*L), nut-water volume (mL), kernel weight (g), and kernel thickness (mm) were assessed as physical parameters, while pH, total soluble solids (oBrix), titratable acidity (as % ascorbic acid), total sugars (g/100g; g/100mL), and minerals (mg/L; mg/kg) were analysed as chemical attributes. Sugars were estimated using Agilent 1260 HPLC and ICP-MS was used to measure the mineral profile. Results revealed that all the tested physical parameters of KCW and KCK increased significantly (p < 0.05) with maturity. The pH, TSS, total sugars, and acidity of KCW increased significantly (p < 0.05), while mineral content decreased significantly (p < 0.05) with maturity. However, the TSS and minerals of KCK decreased significantly (p < 0.05) with maturity and a higher sucrose content was reported in KCK compared to KCW at later maturity. The Ca+2 and Mg+2 were prominent in both KCW and KCK. The study concluded that the physico-chemical characteristics varied widely with the maturity of king coconuts. The selection of optimum harvest maturity to match the preferred attributes of intended applications is suggested.
{"title":"Study on compositional changes of king coconut (Cocos nucifera var. aurantiaca) water and kernel during maturation and evaluation of optimum quality characteristics targeting commercial applications","authors":"M. Jayasinghe, M. Gunasekara, M. Perera, K. Karunarathna, G. U. Chandrasiri, I. Hewajulige","doi":"10.4038/jnsfsr.v51i2.11127","DOIUrl":"https://doi.org/10.4038/jnsfsr.v51i2.11127","url":null,"abstract":"\u0000King coconut (Cocos nucifera var. aurantiaca) is a tropical nut with notable nutritional and medicinal values. King coconut water (KCW) and king coconut kernel (KCK) are sweet and refreshing. They undergo several changes during maturation. The objective of this study was to assess the physico-chemical changes of KCW and KCK with maturity. Three different maturity stages (6, 7, and 8 months) of the variety aurantica, known locally as ‘Nawasi Thembili’ were studied for several physico-chemical parameters. Whole nut weight (g), nut-circumference (cm), colour (water/kernel) (*L), nut-water volume (mL), kernel weight (g), and kernel thickness (mm) were assessed as physical parameters, while pH, total soluble solids (oBrix), titratable acidity (as % ascorbic acid), total sugars (g/100g; g/100mL), and minerals (mg/L; mg/kg) were analysed as chemical attributes. Sugars were estimated using Agilent 1260 HPLC and ICP-MS was used to measure the mineral profile. Results revealed that all the tested physical parameters of KCW and KCK increased significantly (p < 0.05) with maturity. The pH, TSS, total sugars, and acidity of KCW increased significantly (p < 0.05), while mineral content decreased significantly (p < 0.05) with maturity. However, the TSS and minerals of KCK decreased significantly (p < 0.05) with maturity and a higher sucrose content was reported in KCK compared to KCW at later maturity. The Ca+2 and Mg+2 were prominent in both KCW and KCK. The study concluded that the physico-chemical characteristics varied widely with the maturity of king coconuts. The selection of optimum harvest maturity to match the preferred attributes of intended applications is suggested.","PeriodicalId":17429,"journal":{"name":"Journal of the National Science Foundation of Sri Lanka","volume":" ","pages":""},"PeriodicalIF":0.5,"publicationDate":"2023-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42170733","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"综合性期刊","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-06-30DOI: 10.4038/jnsfsr.v51i2.11396
U. Samarajeewa
Polycyclic aromatic hydrocarbons (PAHs) are of petrogenic or pyrogenic origin. Of the known few hundred PAHs, 16 are identified to be toxic, of which 8 are teratogenic. Of the 8, 4 are carcinogens. Among them, Benzo[a]pyrene (BaP) possesses the highest carcinogenicity and is used as a marker in toxicity studies. PAHs of petrogenic origin contaminate soil, water and air. They may occur in air associated with dust particles. PAHs of pyrogenic origin are generated during burning of wood and other organic matter. They are also produced from lipids and carbohydrates during heating of foods. PAHs are mostly identified with grilling, smoking, frying, roasting and toasting of foods. Among the foods, formation of PAHs is studied mostly in association with grilling of fish and meat, where contacts occur between the dripping lipids and naked flames. The generated PAHs get deposited back on fish and meat muscles. PAHs in smoke are deposited on food surfaces on exposure to contaminated air from the vehicle fumes and smoke curing of foods. PAHs are formed during mechanical expulsion of edible oils. Presence of markers, carcinogenic PAHs and total PAHs in different foods and their extent of formation and deposition is discussed in relation to food safety hazards and health implications. Among the local foods and food preparation habits, the role of coconut oil, smoke curing of foods and formation of PAHs even under mild conditions of heat such as manufacture of black tea are reviewed. Recommendations for future actions, research and implementing food regulations to minimize PAHs in foods are presented.
{"title":"Polycyclic aromatic hydrocarbons and food safety: A review","authors":"U. Samarajeewa","doi":"10.4038/jnsfsr.v51i2.11396","DOIUrl":"https://doi.org/10.4038/jnsfsr.v51i2.11396","url":null,"abstract":"\u0000Polycyclic aromatic hydrocarbons (PAHs) are of petrogenic or pyrogenic origin. Of the known few hundred PAHs, 16 are identified to be toxic, of which 8 are teratogenic. Of the 8, 4 are carcinogens. Among them, Benzo[a]pyrene (BaP) possesses the highest carcinogenicity and is used as a marker in toxicity studies. PAHs of petrogenic origin contaminate soil, water and air. They may occur in air associated with dust particles. PAHs of pyrogenic origin are generated during burning of wood and other organic matter. They are also produced from lipids and carbohydrates during heating of foods. PAHs are mostly identified with grilling, smoking, frying, roasting and toasting of foods. Among the foods, formation of PAHs is studied mostly in association with grilling of fish and meat, where contacts occur between the dripping lipids and naked flames. The generated PAHs get deposited back on fish and meat muscles. PAHs in smoke are deposited on food surfaces on exposure to contaminated air from the vehicle fumes and smoke curing of foods. PAHs are formed during mechanical expulsion of edible oils. Presence of markers, carcinogenic PAHs and total PAHs in different foods and their extent of formation and deposition is discussed in relation to food safety hazards and health implications. Among the local foods and food preparation habits, the role of coconut oil, smoke curing of foods and formation of PAHs even under mild conditions of heat such as manufacture of black tea are reviewed. Recommendations for future actions, research and implementing food regulations to minimize PAHs in foods are presented. ","PeriodicalId":17429,"journal":{"name":"Journal of the National Science Foundation of Sri Lanka","volume":" ","pages":""},"PeriodicalIF":0.5,"publicationDate":"2023-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45958754","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"综合性期刊","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-06-30DOI: 10.4038/jnsfsr.v51i2.10819
P. Ginigaddarage, G. J. Ganegama Arachchi, K. Ariyawansa, C. Nanayakkara
This study aimed to identify histamine-forming bacteria (HFB) and the sources of introduction of such bacteria to recommend control measures to mitigate histamine formation in yellowfin tuna (YFT). Field samples were collected from multi-day boats that landed at Dikkowita, Negombo, Trincomalee and Dondra fishery harbours. Ice from the fish holds (n=63) and chill transport vehicles (n=63), and swabs from the fish holds (n=63), the boat decks (n=63) and the skin of YFT (n=63) were collected. Fish loin samples (n=15), ice samples (n=36) and swabs from the skin of YFT (n=18), floor (n=18) and chill transport vehicles (n=18) were collected from fish processing plants. Presumptive HFB isolated from Nivens medium and Violet Red Bile Glucose (VRBG) agar were screened for histamine forming ability in Tripticase soy broth (TSB) supplemented with 1.0% L-histidine. HFB isolates were characterized by sequencing approximately 1400 bp of the 16S rDNA. Seven isolates that produced histamine in the range of 3000–4000 ppm in TSB isolated from ice samples, and a swab sample collected from the boat deck, were confirmed as Klebsiella aerogens (n=6) and Morganella morganii (n=1) respectively. Hafnia alvei (n=1), Serratia sp. (n=2), Citrobacter freundii (n=1), Rahnella sp. (n=1) and Aeromonas salmonicida (n=8) were also among the isolated histamine forming bacteria. Pseudomonas sp. (n=24) and Shewanella baltica (n=7), which are known as spoilage bacteria were also isolated and showed weak histamine formation. Hence, it is evident that histamineforming bacteria could be introduced into the fish from ice and contacting surfaces. This necessitates the practice of rigorous cleaning procedures and adaptation of proper postharvest handling procedures to minimize contamination of the fish.
{"title":"Prevalence, isolation and identification of histamine forming bacteria in selected stages of supply chain of Yellowfin tuna export industry in Sri Lanka","authors":"P. Ginigaddarage, G. J. Ganegama Arachchi, K. Ariyawansa, C. Nanayakkara","doi":"10.4038/jnsfsr.v51i2.10819","DOIUrl":"https://doi.org/10.4038/jnsfsr.v51i2.10819","url":null,"abstract":"\u0000This study aimed to identify histamine-forming bacteria (HFB) and the sources of introduction of such bacteria to recommend control measures to mitigate histamine formation in yellowfin tuna (YFT). Field samples were collected from multi-day boats that landed at Dikkowita, Negombo, Trincomalee and Dondra fishery harbours. Ice from the fish holds (n=63) and chill transport vehicles (n=63), and swabs from the fish holds (n=63), the boat decks (n=63) and the skin of YFT (n=63) were collected. Fish loin samples (n=15), ice samples (n=36) and swabs from the skin of YFT (n=18), floor (n=18) and chill transport vehicles (n=18) were collected from fish processing plants. Presumptive HFB isolated from Nivens medium and Violet Red Bile Glucose (VRBG) agar were screened for histamine forming ability in Tripticase soy broth (TSB) supplemented with 1.0% L-histidine. HFB isolates were characterized by sequencing approximately 1400 bp of the 16S rDNA. Seven isolates that produced histamine in the range of 3000–4000 ppm in TSB isolated from ice samples, and a swab sample collected from the boat deck, were confirmed as Klebsiella aerogens (n=6) and Morganella morganii (n=1) respectively. Hafnia alvei (n=1), Serratia sp. (n=2), Citrobacter freundii (n=1), Rahnella sp. (n=1) and Aeromonas salmonicida (n=8) were also among the isolated histamine forming bacteria. Pseudomonas sp. (n=24) and Shewanella baltica (n=7), which are known as spoilage bacteria were also isolated and showed weak histamine formation. Hence, it is evident that histamineforming bacteria could be introduced into the fish from ice and contacting surfaces. This necessitates the practice of rigorous cleaning procedures and adaptation of proper postharvest handling procedures to minimize contamination of the fish.","PeriodicalId":17429,"journal":{"name":"Journal of the National Science Foundation of Sri Lanka","volume":" ","pages":""},"PeriodicalIF":0.5,"publicationDate":"2023-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48604647","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"综合性期刊","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-06-30DOI: 10.4038/jnsfsr.v51i2.11185
K. Fernando, N. Priyankara
Soil nailing is a technique which is used to reinforce and strengthen the existing ground conditions. This is done by installing closely spaced, passive, structural inclusions known as nail into the soil and these nails helps to improve the overall shear strength of soil. The nail pullout resistance is the shear stress at the grout-soil interface. The soil-nail pullout resistance depends on many parameters. Among the factors influencing the soil-nail pullout resistance, degree of saturation of the soil is an important factor. As degree of saturation of soil mass change with the moisture content of the soil, the pullout resistance may decrease during the intense rainfall. However, verification of pullout tests on soil-nail are not conducted under the worst condition. Hence, measured pullout resistance may not be a safe parameter for design. As such, in this research study, the effect of degree of saturation on pullout resistance was studied by conducting a series of laboratory tests using a laboratory pullout box. Especially designed waterproof cap was used to apply back pressure to saturate the soil within the pullout box. Variation of earth pressures close to the grouted nail were observed during the tests. It was evident from the results that higher the degree of saturation, lower the pullout resistance. Maximum pullout resistance was observed when the degree of saturation is near the optimum moisture of the soil. When the soil is sufficiently dry, lower pullout resistance was observed due to low bond strength between grout surface and surrounding dry soil.
{"title":"Effect of Degree of Saturation on soil-nail Pullout Resistance","authors":"K. Fernando, N. Priyankara","doi":"10.4038/jnsfsr.v51i2.11185","DOIUrl":"https://doi.org/10.4038/jnsfsr.v51i2.11185","url":null,"abstract":"Soil nailing is a technique which is used to reinforce and strengthen the existing ground conditions. This is done by installing closely spaced, passive, structural inclusions known as nail into the soil and these nails helps to improve the overall shear strength of soil. The nail pullout resistance is the shear stress at the grout-soil interface. The soil-nail pullout resistance depends on many parameters. Among the factors influencing the soil-nail pullout resistance, degree of saturation of the soil is an important factor. As degree of saturation of soil mass change with the moisture content of the soil, the pullout resistance may decrease during the intense rainfall. However, verification of pullout tests on soil-nail are not conducted under the worst condition. Hence, measured pullout resistance may not be a safe parameter for design. As such, in this research study, the effect of degree of saturation on pullout resistance was studied by conducting a series of laboratory tests using a laboratory pullout box. Especially designed waterproof cap was used to apply back pressure to saturate the soil within the pullout box. Variation of earth pressures close to the grouted nail were observed during the tests. It was evident from the results that higher the degree of saturation, lower the pullout resistance. Maximum pullout resistance was observed when the degree of saturation is near the optimum moisture of the soil. When the soil is sufficiently dry, lower pullout resistance was observed due to low bond strength between grout surface and surrounding dry soil.","PeriodicalId":17429,"journal":{"name":"Journal of the National Science Foundation of Sri Lanka","volume":" ","pages":""},"PeriodicalIF":0.5,"publicationDate":"2023-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49564735","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"综合性期刊","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-06-30DOI: 10.4038/jnsfsr.v51i2.10780
H. Jayasiri
This study evaluates the phytoplankton community structure in relation to physicochemical properties in the western and southwestern coastal waters of Sri Lanka. Phytoplankton and water samples were collected from March to April, 2017 at three transect lines towards offshore in Colombo, Beruwala, and Mirissa, each containing 10 sampling sites. The distance between sampling stations on each transect line was approximately 2 km. Phytoplankton samples were collected towing a net (10 µm mesh) by vertical hauls from known depth (2.5 m) and preserved in Lugol’s solution. The phytoplankton were identified to the lowest possible taxonomic level and counted under the Sedgwick rafter cell using a light microscope. Water samples were collected at 0.5 m depth using the Ruttner Sampler and analysed for chlorophyll-a, nutrients, and total suspended solids (TSS). This study identified 57 phytoplankton species comprised of diatoms (33 species), dinoflagellates (23 species), and cyanobacteria (1 species). In general, phytoplankton abundance and species diversity decreased towards offshore in the three transects. Total phytoplankton and diatom abundances varied significantly among the three transect lines, and significantly higher abundance was reported at Mirissa and Colombo than at Beruwala (One-way ANOVA; p < 0.05). Total phytoplankton abundance significantly correlated with dinoflagellates, toxic species of dinoflagellates, chlorophyll-a, and nitrate-N (p < 0.01). Ten toxic species of dinoflagellates were reported in the study. Diatoms dominated (60%) in the study area, followed by cyanobacteria (31%) and dinoflagellates (9%). Diatoms of Cerataulina sp. (31%) and Navicula sp. (50%) were dominant in Colombo and Mirissa respectively, while cyanobacteria of Trichodesmium sp. (85%) dominated in Beruwala, indicating the possibility of blooms of this species at study sites when environmental conditions are favourable.
{"title":"Preliminary study on surface phytoplankton assemblages and physicochemical parameters, off the west and south-west coasts of Sri Lanka","authors":"H. Jayasiri","doi":"10.4038/jnsfsr.v51i2.10780","DOIUrl":"https://doi.org/10.4038/jnsfsr.v51i2.10780","url":null,"abstract":"\u0000This study evaluates the phytoplankton community structure in relation to physicochemical properties in the western and southwestern coastal waters of Sri Lanka. Phytoplankton and water samples were collected from March to April, 2017 at three transect lines towards offshore in Colombo, Beruwala, and Mirissa, each containing 10 sampling sites. The distance between sampling stations on each transect line was approximately 2 km. Phytoplankton samples were collected towing a net (10 µm mesh) by vertical hauls from known depth (2.5 m) and preserved in Lugol’s solution. The phytoplankton were identified to the lowest possible taxonomic level and counted under the Sedgwick rafter cell using a light microscope. Water samples were collected at 0.5 m depth using the Ruttner Sampler and analysed for chlorophyll-a, nutrients, and total suspended solids (TSS). This study identified 57 phytoplankton species comprised of diatoms (33 species), dinoflagellates (23 species), and cyanobacteria (1 species). In general, phytoplankton abundance and species diversity decreased towards offshore in the three transects. Total phytoplankton and diatom abundances varied significantly among the three transect lines, and significantly higher abundance was reported at Mirissa and Colombo than at Beruwala (One-way ANOVA; p < 0.05). Total phytoplankton abundance significantly correlated with dinoflagellates, toxic species of dinoflagellates, chlorophyll-a, and nitrate-N (p < 0.01). Ten toxic species of dinoflagellates were reported in the study. Diatoms dominated (60%) in the study area, followed by cyanobacteria (31%) and dinoflagellates (9%). Diatoms of Cerataulina sp. (31%) and Navicula sp. (50%) were dominant in Colombo and Mirissa respectively, while cyanobacteria of Trichodesmium sp. (85%) dominated in Beruwala, indicating the possibility of blooms of this species at study sites when environmental conditions are favourable.","PeriodicalId":17429,"journal":{"name":"Journal of the National Science Foundation of Sri Lanka","volume":" ","pages":""},"PeriodicalIF":0.5,"publicationDate":"2023-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47197795","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"综合性期刊","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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