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Water quality of wetland ecosystems is a critical concern due to its implications on human health and aquatic life. This study was conducted to assess the spatial and temporal variation of water quality in Kotagala wetland to understand its impact on water safety for domestic uses and ecosystem health. Water samples were collected (n = 70) from six inlets and the wetland outlet from November 2021 to August 2022, and analyzed for pH, electrical conductivity (EC), salinity, total dissolved solids (TDS), total suspended solids (TSS), nitrate, and phosphate. The pH, EC, and nitrate showed significant correlations. Spatial clustering divided the monitoring sites into two clusters, as areas of higher and lower pollution levels. Discriminant analysis highlighted the significance of EC, pH, and nitrate concentrations in differentiating these clusters. Principal According to principal component analysis (PCA) 88.8% of the total variance of spatial variation in water quality was explained by the first two components. Temporal clustering following seasonal variations revealed the influence of rainfall pattern on water quality. EC, TDS, TSS, and nitrate concentrations emerged as the most important factors in this temporal categorization. In PCA, 76.8% of the total variance of temporal variation in water quality was explained by the first two components. Findings highlight the urgent need for sustainable strategies and policies to mitigate the impacts of human activities on wetland water quality, since water quality variations in the wetland was significantly impacted by direct human activities, and variations in rainfall trends in the area. [ABSTRACT FROM AUTHOR]

Background: The initial stage of plants and sunlight as the energy source are very critical for plants. A boost of biochemical reactions given by concentrating solar energy at the initial stage of plants may continue accelerated growth and yield. Rice is a high-demand crop. Therefore, in this research study, the germination of rice seeds was studied under different radiation levels using a spherical solar concentrator (SSC). Methods: The germination percentage of rice seeds was observed under different radiation levels. Experimental setup 1 consisted of 60 cm below the SSC (SSC 60 cm) and open environment (OE) whereas Experimental setup 2 consisted of 45 cm below the SSC (SSC 45 cm) and OE. Result: SSC (60 cm) and SSC (45 cm) manifested 1.2 and 1.5 times higher solar energy than the OE, respectively. In experimental setup 1, it was observed germination percentages of 65.2 and 58.8 in SSC (60 cm) and OE, respectively whereas, in the experimental setup 2, 86.9 and 77.5 in SSC (45 cm) and OE, respectively. It can be assumed that plants grown under SSC during the nursery stage, reach the fullest potential at maturity as a result of increased flux density and lower soil temperature under the SSC. [ABSTRACT FROM AUTHOR]

Irrigated agriculture is the highest water user in Sri Lanka. Therefore, when there is an increasing demand of other sectors such as drinking, industries, environment etc., it is required to reallocate water from the irrigated agriculture sector to meet this increased demand. However, this needs to be done while ensuring the food security of the nation using the virtual water concept, which is defined as the embedded water in a product. Therefore, this study is conducted with the objective of assessing the, i) virtual water of agricultural production, ii) virtual water of food imports and exports, iii) virtual water trade and iv) water footprint of the nation. The data on crop water requirements, extent cultivated, imported, and exported agricultural products were collected from secondary sources and the analysis was made according to the globally accepted methodology. The annual virtual water value of domestic production is found to be 8.13 Gm³ of which paddy contributes 54.7%. The average virtual water value of paddy in Maha season is less than that in the Yala season whilst the virtual water value of paddy in minor schemes are higher than that in the major schemes in both seasons implying that more water is required to produce 1kg of paddy in minor schemes. The net import of Virtual water is 3.8 Gm³ per year. The water footprint of Sri Lanka is 12.0 Gm³ per year with a per capita water footprint of 535.22 m3 per year. The water required for domestic production is about 15.8% of the surface runoff of the country indicating the possibility of meeting the food demand with the available water resources. [ABSTRACT FROM AUTHOR]

Background: Sun drying is a popular post-harvest operation to maintain rice quality during the storage period. Farmers use different pads and thicknesses for sun drying of paddy in Ampara district, Sri Lanka. A study was conducted to evaluate the suitability and effectiveness of the drying pad and thickness as practiced by local paddy farmers during the sun drying process. Methods: The grain with an initial moisture content of 28% (dry basis) was sun dried with four types of drying pads and five levels of thickness of grain. This experiment was conducted between 8.30 am and 4.30 pm at the South Eastern University of Sri Lanka in August 2020. The moisture contents of the grain were measured at regular time intervals. Result: It was found that the duration of drying of paddy from 28% to 13% moisture content on a dry basis was 300 to 540 minutes depending upon the drying pad and thickness. The tarpaulin is reasonable at shallow thickness with less time to reach the necessary moisture level than other drying pads. Black polythene and fertilizer bag can be utilized for sun drying of paddy at 4 cm thickness with 130 minutes. It was found that with an increase in the thickness of paddy from 0.5 cm to 4 cm, the drying time increases. A statistically significant interaction was obtained between drying pads and thickness level on moisture removal of paddy. Therefore, the moisture removal rate differs with the drying pad and thickness of the paddy under open sun drying. [ABSTRACT FROM AUTHOR]

Water in agricultural catchments is prone to pollution from agricultural runoff containing nutrients and pesticides, and contamination from the human population working and residing therein. This study examined the quality of water in a drainage stream which runs through a congested network of 'line houses' (low-income housing, typically found arranged in straight 'lines' on estates) in the tea estate catchment area of Pussellawa in central Sri Lanka. The study evaluated the applicability of vertical subsurface flow (VSSF) and horizontal subsurface flow (HSSF) constructed wetlands for water polishing, as the residents use the stream water for various domestic purposes with no treatment other than possibly boiling. Water flow in the stream can vary significantly over time, and so investigations were conducted at various flow conditions to identify the hydraulic loading rate (HLR) bandwidth for wetland polishing applications. Two wetland models of 8 m x 1m x 0.6 m (length x width x depth) were constructed and arranged as VSSF and HSSF units. Stream water was diverted to these units at HLRs of 3.3,4,5,10,20, and 40 cm/day. Results showed that both VSSF and HSSF wetland units were capable of substantially reducing five-day biochemical oxygen demand (BOD5), total suspended solids (TSS), fecal coliform (FC), total coliform (TC), ammonia nitrogen (NH4+-N), and nitrate nitrogen (NO3--N) up to 20 cm/day HLR, with removal efficiencies of more than 64%, 60%, 90%, 93%, 70%, and 59% for BOD5, TSS, FC, TC, NH4+-N, and NO3--N, respectively, in the VSSF wetland unit; and more than 66%, 62%, 91%, 90%, 53%, and 77% for BOD5, TSS, FC, TC, NH4+-N, and NO3--N, respectively, in the HSSF wetland unit. [ABSTRACT FROM AUTHOR]

Open dumping of municipal solid waste is a common practice in many developing countries and contaminates surface and groundwater in the vicinity. In this study, long-term monitoring was conducted at an abandoned solid waste dumpsite to characterize temporal variations of perched water and groundwater qualities. The dumpsite was located at Udapalatha PS in Central Province of Sri Lanka and consisted of two sections (namely Old and New sections). The Old section was used for waste dumping for seven years from 2003 to 2010, and the New section was used for six months in 2011. Multiple wells were installed at each section and water qualities monitored for two years from May 2013 to March 2015. Water quality parameters such as pH, EC, BOD, COD, TN, TP, major cations, major anions, and heavy metals were measured monthly. Leachate pollution index (LPI) was used to quantify the leachate contamination potential of landfill site. Results showed that groundwater samples from both Old and New sections exhibited relatively low LPI during the monitoring period, whereas perched water samples from New section showed high LPI with fluctuations. At the monitoring site, perched water and groundwater seem to persist as two independent bodies for both Old and New sections. Especially, the dumped waste at lower layer at the Old section was fully washed out by rainfall and surface water after waste dumping and currently carries a low risk of groundwater contamination. [ABSTRACT FROM AUTHOR]

We examined the ability of Scirpus grossus planted in a constructed wetland to treat domestic wastewater. One unit was planted with S. grossus, and another unit was used as a control. Influent wastewater and effluent from each wetland were tested monthly for 10 physical, chemical, and biological parameters from May 2004 to July 2005. Better performance was obtained by the vegetated unit than by the control unit. Mean removal efficiencies observed with S. grossus were total suspended solids, 61%; NH4+-N, 71%; NO3- -N, 31%; total phosphorus 18%; fecal coliforms, 90%; and five-day biochemical oxygen demand, 69%. Plant growth was continuously monitored, and the above-ground biomass of S. grossus was harvested after eight months, 11 months, and 14 months, when plants reached their maximum shoot height and inflorescence formation started. S. grossus has great potential to remove pollutants in constructed wetlands in tropical regions, especially because above-ground harvesting would be a feasible plant management option by which nutrients could be subsequently removed. [ABSTRACT FROM AUTHOR]

This study aimed to identify appropriate filling materials for a permeable reactive barrier (PRB) system to treat groundwater contaminated with trace metals in the vicinity of solid waste landfills in Sri Lanka. Mixtures of alluvial loamy soil, coconut shell biochar, and laterite clay brick in different proportions were tested as easily-available PRB adsorbents. A series of adsorption and desorption experiments were carried out to investigate the effects of initial concentration, pH, ionic strength, and multiple competitive trace elements on Cd and Pb adsorption onto the tested adsorbents. In addition, hydraulic conductivities (Ks) of the tested adsorbents under different compaction levels were measured to examine a suitable packing condition for the PRB system. Results showed that the Langmuir model performed well for fitting Cd and Pb adsorption isotherms and maximum adsorption capacities (Qm) for Pb (2.1-15.3mg/g) became higher than those for Cd (0.8-6.8mg/g). All tested adsorbents showed low leaching of adsorbed metals with high hysteresis indices in desorption studies. In the multiple trace element solution, the existence of other trace metals (Cu, Zn, Ni) had a significant effect on Cd adsorption but less on Pb adsorption. The three mixed adsorbents had no dependency on the initial pH and ionic strength of the solution, while the single material showed a low dependency in both Cd and Pb adsorption. The inclusion of brick was effective to improve the hydraulic property and measured Ks values for the 75% brick mixed materials resulted of >10-4 cm/s at high compaction levels (Dr=90% and 100%). Three mixed materials can be strongly recommended as a PRB filling material to treat landfill leachate based on their reactivity and hydraulic properties. [ABSTRACT FROM AUTHOR]

A long-term monitoring of composition of landfill gases in the region with high rainfall was conducted using an argon assay in order to discuss air intrusion into the dump site. Gas samples were taken from vertical gas monitoring pipes installed along transects at two sections (called new and old) of an abandoned waste dump site in Sri Lanka. N 2 O concentrations varied especially widely, by more than three orders of magnitude (0.046-140 ppmv). The nitrogen/argon ratio of landfill gas was normally higher than that of fresh air, implying that denitrification occurred in the dump site. Argon assays indicate that both N 2 and N 2 O production occurred inside waste and more significantly in the old section. The Ar assay would help for evaluations of N 2 O emission in developing countries., Implications: A long-term monitoring of composition of landfill gases in the region with high rainfall was conducted using an argon assay in order to discuss air intrusion into the dump site. Argon assays indicate that both N 2 and N 2 O production occurred inside waste and more significantly in the old section.