ARS - 2011
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Item Net photosynthetic production and potential carbon assimilation capacity of mangroves of Kadolkele in Negombo estuary, Sri Lanka(University of Kelaniya, 2011) Perera, K.A.R.S.; Saparamadu, M.D.J.S.; Amarasinghe, M.D.Mangroves are considered as highly productive ecosystems that have considerable potential to serve as efficient sinks of carbon, both on short and long time scales. Magnitude of mangrove primary productivity is highly variable in space and time and it depends on factors such as tidal flushing, latitude, temperature, salinity and nutrient regimes as well as substrate characteristics. Net primary production is represented by above and below ground biomass, litter production and the rate of grazing by herbivores. Since results of very few studies on primary productivity of Sri Lankan mangroves are available, the present study was conducted with the objective of understanding the net primary productivity and magnitude of net carbon assimilation capacity of mangrove ecosystem at Kadolkele. The study was conducted at Kadolkele (7011‟42.18”- 7011‟50.48” N; 790 50‟32.08”– 790 50‟47.50” E), a relatively undisturbed natural mangrove stand extending over 13.5ha, at the northern end of Negombo estuary. Data on biomass increment and litterfall during study period were gathered from twenty 10 m x10 m permanent study plots of three belt transect of 10 m wide laid perpendicular to the shoreline. Annual increment of above and below ground biomass was calculated by girth (gbh) increment, using allometric relationships developed between gbh and biomass of mangrove trees. Biomass loss through herbivory was assumed to be negligible due to high tannin content in mangrove plant parts and thus their low palatability. Organic carbon content of each component of mangrove trees was determined by Walkey and Black wet oxidation without external heating procedure followed by colorimetric method to determine absorbance at 600 nm, using a UV- visible spectrophotometer. Annual organic carbon accumulation was calculated from NPP and organic carbon content. Relatively high values of NPP were recorded from the water-front areas of the mangrove stand and it decreased towards inland. Annual total organic carbon increment was recorded to be 1232.17 + 9.23 g m-2y-1 of which 682.80 + 7.51 g m-2y-1 was found deposited in the above ground woody parts while 396.46 + 4.65 g m-2y-1 was in the plant litter and 152.91 + 1.94 g m-2y-1 in the roots. Potential capacity of Kadolkele mangroves in assimilating and accumulating carbon is 166.66 t y-1 and this amount is equivalent to the amount of carbon emitted as CO2 by combustion of 272,694 (nearly quarter of a million) liters of diesel in motor vehicles. Assuming a motor car consumes 1200 liters of diesel per year, this mangrove stand at Kadolkele with an extent of 13.5 ha can remove atmospheric carbon produced by 227 cars during one year.Item Development of allometric equations to determine above and below ground biomass and organic carbon content in Bruguiera gymnorrhiza and Lumnitzera racemosa(University of Kelaniya, 2011) Perera, K.A.R.S.; Saparamadu, M.D.J.S.; Amarasinghe, M.D.Bruguiera gymnorrhiza and Lumnitzera racemosa are two species of true mangroves commonly found in Sri Lankan mangrove areas. Determination of amount of carbon assimilated by these two species therefore, is of considerable importance to estimate the carbon fixing capacity of Sri Lankan mangrove areas. Objective of the present study therefore, is to develop allometric relationships between biomass of stems, leaves, below and above ground roots with easily measured variables such as girth/ diameter at breast height (gbh/dbh) that can be used in estimating the carbon assimilation capacity of Sri Lankan mangrove ecosystems. The below ground biomass of trees of the two mangrove species accounted for 20 – 44 % of the total biomass of the plants. The ratio (A/B) between above (A) to below (B) ground biomass of Lumnitzera racemosa ranged 1.4 – 3.9 and that for Bruguiera gymnorhiza was 1.2 – 4.4, indicating relatively greater amount of biomass in the below ground root systems.Data on dry weight of plant components were analyzed with SPSS ver.16 and a strong positive correlation (p<0.01) and non-leaner relationship (r2 >0.80) were revealed for stems, roots, above ground and total biomass of plants with dbh of individuals of the two species. Four allometric equations were derived between biomass of different components with dbh of Bruguiera gymnorrhiza ; biomass of stem= 0.115 (dbh)2.386, biomass of root = 0.100 (dbh)2.364, above ground biomass =0.289 (dbh)2.327 and total biomass (above +below)= 0.405 (dbh)2.320 . Four other allometric equations were derived between biomass of different components with dbh of Lumnitzera racemosa; biomass of trunk= 0.098 (dbh)2.244, biomass of root = 0.118 (dbh)2.063, above ground biomass =0.114 (dbh)2.523 and total biomass (above +below)= 0.220 (dbh)2.376 . Using the organic carbon content embodied in biomass of the components of the plants of the two species, equations were altered to represent the relationship between organic carbon present and the dbh. Organic carbon content in Bruguiera gymnorhiza stem=0.0631 (dbh)2.386 and root = 0.0529 (dbh)2.364 and organic carbon content Lumnitzera racemosa trunk = 0.0546 (dbh)2.244 and root= 0.0624 (dbh)2.063 . These allometric relationships are required to estimate the amount of carbon accumulated in the plants of these mangrove species and thus the carbon assimilation capacity of the mangrove stands that comprise these mangrove species.Item Chronic arsenic toxicity among patients of Chronic Kidney Disease of unknown etiology (CKDu) in North Central Province, Sri Lanka(University of Kelaniya, 2011) Jayasumana, M.A.C.S.; Paranagama, P.A.; Fonseka, S.I.; Amarasinghe, M.D.; Rajakaruna, L.; Wijewardena, C.In recent years, a significant increase in patients of Chronic Kidney Disease of unknown etiology (CKDu) has been observed in some parts of Sri Lanka, especially in North Central Province. Uniqueness of this disease is that its victims do not share the same history as other kidney patients who have had it either due to diabetes, high blood pressure or glomerulonephritis. A reconnaissance survey was conducted in the 12 CKDu endemic villages, followed by a door-to-door visit for clinical assessment and biological sample collection of CKDu patients among the villagers (n=125). Control group (n=180) were selected from those individuals from the study area who had not been diagnosed to have CKDu and some of them were selected randomly from family members of CKDu patients. Hair and urine samples were collected from both CKDu patients and controls. The clinical assessment of patients and some individuals from control group had shown dermal manifestations of chronic arsenic (As) poisoning (CAP). 44.8% and 39.2%of the CKDu patients and 18.8% and 14.4% of the control group had hyper pigmentation of palms and soles respectively. 23.2% of the CKDu patients and 10.5% of the controls have shown keratosis of palms. In soles it was 17.6% and 8.3% respectively. Hair and urine samples from CKDu patients have shown presence of high amounts of As which exceed the toxic level. Generalized body weakness, headache, burning of eyes, nausea, mild to moderate hepatomegaly, epigastric pain and parasthesia, the other clinical symptoms of CAP were also observed among a significant proportion of CKDu patients in the sample but to a lesser extent among the individuals of the control group. Findings of the present study reveal that 52% of the CKDu patients and 14.4% of the subjects in the control group have shown symptoms required to be diagnosed CAP. Percentage CKDu patients who fulfill the requirements for CAP were greater than that among the control group. Observable CAP symptoms among individuals of the control group indicate that being inhabitants of the same area, consuming the same As-contaminated water, majority of the population has already bio-accumulated arsenic, nevertheless to a lesser extent than those who have been diagnosed as CKDu patients. This also implies that these individuals are of high risk in acquiring CKDu in the near future.Item Preliminary investigations on presence of arsenic in Sri Lankan soils & plants(University of Kelaniya, 2011) Fonseka, S.I.; Amarasinghe, M.D.; Paranagama, P.A.Arsenic is well recognized as an element of public concern due to its high toxicity and carcinogenic properties. Occurrence of chronic arsenic poisoning symptoms in patients of chronic kidney disease of unknown etiology (CKDu) from Padaviya area led to the hypothesis that chronic accumulation of arsenic may be the potential cause of CKDu. The most likely means of ingestion of arsenic may be groundwater as all CKDu patients have been consuming groundwater, and not surface water for the last few decades. Presence of inorganic and organic arsenic is evidently the result of presence of it in groundwater and interstitial (soil) water from which it can enter plants. The present study therefore, was carried out with the objective of determining arsenic content in soil profiles as well as selected aquatic and terrestrial plants in Padaviya area with a view to understanding the vertical and horizontal (spatial) distribution of arsenic in the environment. Soil samples were taken at 1 foot depths down to 12 feet from paddy fields, homesteads and areas of Padaviya reservoir using a spiral auger. Soil was also collected from Deniyaya (Pasgama), a non-CKDu endemic area, as control samples. Three samples were taken from every one-foot depth in the soil profile and collected into polythene bags. The auger was cleaned thoroughly to remove all soil and washed with de-ionized water prior to taking samples. Samples of roots, leaves, flowers and bark of common trees, shrubs and herbaceous plants in the study area were collected in plastic bags and brought to the laboratory to test for the presence of arsenic. Control plant samples were collected from non-CKDu areas. Soil particle sizes and cation exchange capacity were determined using standard methods; organic matter was measured using weight loss on ignition. Soil and plant samples were acid digested using nitric (4): suphuric (1): perchloric acid (1) mixture until a clear solution was obtained and the digested samples were used to detect arsenic in them using the hydride generator and atomic absorption spectrometer. Distribution of Fe and Al in soil that affects bioavailability of arsenic in soil and groundwater was determined using oxalate-extraction method. All surface soil samples contained total arsenic contents greater than those in the bottom horizons of the soil profiles. Surface layers of soil in paddy fields of Padaviya area were detected to have relatively high levels when compared to that of the deep layers. On the contrary the As level in the deep layers of soil in the control area in the wet zone recorded higher values than that of the surface which could be attributed to the greater incidence of leaching that is possible in wet zone soils. No As arsenic was detected below 7 feet depth in Padaviya reservoir. Relationship between distribution of oxalate-extractable Fe with presence of As in soil will be discussed. Bark of Azadirachta indica (Kohomba) was found to accumulate the greatest amount of total As while it was observed that roots and leaves of Terminalia arjuna too accumulate As more than the other tree species. Eichhornia crassipes, the aquatic floating plant and flowers of Nelumbo sp. (rooted aquatic plant) were found to contain excessive amounts of As, indicating their capacity to hyper-accumulate As and thus their potential to be used as candidate species in arsenic phytoremediation.