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1.
C. B. Dissanayake A. M. Rohana Bandara S. V. R. Weerasooriya 《Environmental Geology》1987,10(2):81-88
The Kandy lake, situated in the heart of Sri Lanka's second largest city with a population of nearly 120,000, has been monitored
to probe the extent of heavy metal pollution. Although the lake is a source of drinking water to the city, a large number
of effluent canals drain into the lake carrying a continuous flow of industrial and domestic waste matter. A total of 66 surface
water samples were analyzed for their Fe2+, total Fe, total V, SO
4
2−
, Cd2+, and Pb2+ contents. Pb and Cd were found in high concentrations averaging 150 μg/l and 77 μg/l, respectively, and exhibit a marked
positive correlation with each other (r=+0.94). Vehicular emissions and industrial waste matter contribute largely to the Pb and Cd contents of the lake, the anthropogenic
influence outweighing the contributions made by geological materials. All field observations and laboratory experiments indicate
a tendency of the Kandy Lake towards eutrophicity. 相似文献
2.
A regional geochemical and mineralogical study aimed at investigating the mineralization in the western-part of the Walawe Ganga (river) Basin in Sri Lanka is represented in this paper. The river basin is the 3rd largest in the country and has within it a boundary zone between two geologically different crustal blocks, which are marked by granulitic grade rocks and amphibolite grade rocks. Size fractions of stream sediments (< 63 μm; 63–125 μm; 125–177 μm and 177–250 μm) developed on the granulite-grade metamorphic terrain have been analysed at their source for their mineralogical and selected element compositions. Thirty-eight (38) sediment samples and 15 representative probable parent rock samples were chemically analysed giving special emphasis to the High Field Strength trace Elements (HFSE) including the Rare Earth Elements (REE). The granulite grade rocks in the study area is geochemically similar to that of post Archean upper crust. However the stream sediments developed from the high-grade rocks during the intense weathering, are markedly enriched with HFSE and REE. The enrichment of HFSE and LREE is accounted for by the presence of HFSE- and REE- rich accessory mineral phases such as zircon, monazite, apatite, garnet and rutile in the sediments. In some samples, the content of heavy minerals contributes as much as 50 wt. %. These minerals act as a source of elements in the sediments. However, extreme hydraulic sorting of HFSE- and REE-bearing minerals during the sediment deposition cannot be expected within a short distance from near the sources except from a mineralized occurrence. Therefore, the higher enrichment of these elements presumably indicates occurrences of scattered mineral sources such as highly differentiated granites and associated pegmatites within the Walawe Ganga drainage basin. These granitic pegmatites are probably intruded during or soon after the main granulite-facies metamorphic event and similar events are seen in other terrains of East-Gondwana. 相似文献
3.
Water samples collected from dug wells and tube wells from the Kurunegala District of Sri Lanka have been studied for their
major hydrogeochemical parameters to understand the chemical quality of water in the terrain. The region is composed of Precambrian
metamorphic rocks where groundwater is only available in the regolith and along weak structural discontinuities. The study
of the major chemical constituents of groundwater revealed several relationships with the aquifer lithology. Groundwater from
mafic rocks have high dissolved solids, while quartzose metaclastic rocks yield water with low dissolved solids. The study
area displays very low SO4
2− contents of the groundwater. The chloride content is higher in the dry regions and in terrains underlain by pink granite
and marble/calc gneiss while areas with marble, as expected, show high concentrations of Ca and Mg ions. The waters in the
region can be classified into non-dominant cations to Na + K dominant and Cl− and HCO3
− dominant types. Water from charnockite-bearing areas tends to have non-dominant cations and more CO3
2− + HCO3
− types. Effects such as soluble salts in the regolith, fracture intensity and climatic variations play a significant role
in the behavior of the hydrogeochemistry in the area. 相似文献
4.
Rohana Ulluwishewa Dr. 《GeoJournal》1987,15(4):393-398
In Sri Lanka where the paddy farmers' income is low and tractor hire rates are considerably high, paddy farmers' tendency to use tractors for tillage operation can hardly be explained in rational terms. However, this paper attempts to assess the significance of some selected socio-economic and physical factors which are considered to be effective in generating compelling grounds to use tractors for the tillage operation of paddy fields.Three socio-economic variables relating to shortage of labour, shortage of buffaloes and limited time available for the tillage operation, which were considered to be crucial in determining the farmers propensity to use tractors, were regressed on the degree of tractor utilization; and then the residuals from the regression were mapped. Then, the map of residuals was compared with the map of agro-climatic regions in order to ascertain the impact of agro-climatic conditions on tractor utilization.It was found that the three socio-economic variables collectively explain 51% of the spatial variation of the degree of mechanization. The map of residuals was found to mostly coincide with the map of agro-climatic regions. While all positive residuals were found to be in the dry zone and in the arid zone where the soil is very dry and hard, only negative residuals were found in the wet zone where the soil is wet and soft. Therefore, it seems that the spatial variation of the degree of mechanization which cannot be explained by the selected socio-economic variables may be attributable to the spatially varying soil conditions.It can be concluded that the selected socio-economic factors and the agro-climatic factors pertaining to dryness and hardness of soils collectively encourage or compel Sri Lankan paddy farmers to use tractors for tillage operation. 相似文献
5.
The stable isotope composition (18O and 2H) in the tropical precipitation collected from 18 locations throughout the Deduru Oya river basin in Sri Lanka, has been studied during August and September 2001, in order to characterize the isotopic composition of precipitation in the dry and intermediate climatic zones of Sri Lanka. The isotope compositions are described with respect to the distance from the coast and the altitude. The analyses show that δ18O vary from ? 5·11 to 1·39‰ and δD vary from ? 35·71 to 12·55‰. The d‐excess values range from ? 0·65 to 13·17 with an average value of ～7. Regression for the δ18O ? δD is y = 6·8x + 4·9 (R2 = 0·9) which is compatible with the precipitation in other tropical regions. The lower slope in the regression line and the lower d‐excess value indicate high temperature events which were possibly aided by concentration through successive evaporation within the atmosphere. The spatial variation of isotope composition indicates two different cloud contributions for the rain events, of which one may be linked to the Indian Ocean contribution and the other to the high altitude condensation. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
6.
Fluoride,nitrate and water hardness in groundwater supplied to the rural communities of Ensenada County,Baja California,Mexico 总被引：1，自引：0，他引：1
L. W. Daesslé L. Ruiz-Montoya H. J. Tobschall R. Chandrajith V. F. Camacho-Ibar L. G. Mendoza-Espinosa A. L. Quintanilla-Montoya K. C. Lugo-Ibarra 《Environmental Geology》2009,58(2):419-429
The hydrogeochemistry of 26 wells belonging to ten different aquifers in the county of Ensenada, Baja California, is studied.
These wells are all used to supply the rural communities in the region, which comprise ~37,000 inhabitants, excluding the
city of Ensenada. High total dissolved solids (TDS) concentrations (maximum 7.35 g l−1) indicate that salt is a ubiquitous contaminant in the aquifers due to seawater intrusion. The aquifers that support extensive
agriculture activities (Maneadero, San Quintín, San Simón and El Rosario) are characterized by higher N–NO3 concentrations (maximum 20 mg l−1) derived from fertilizers. Fluoride concentrations exceed the 1.5 mg l−1 Mexican official limit in only four wells. The enrichments of F− in the southern aquifers are thought to be associated to water–rock interactions controlled mainly by Na–Ca equilibrium reactions
with fluorite, as suggested from high dissolved Na concentrations in these waters. In the northern aquifer of Maneadero, no
enrichment of Na is found and a geothermal source for F− is likely. Water is hard to moderately hard, with Ca/Mg ratios >1. Although drinking water directly from the tap is not a
common practice in these localities, most sources have concentrations of major ions and TDS that exceed the Mexican official
limits. 相似文献
7.
Kasun Gayantha Joyanto Routh Krishnamurthy Anupama Jean Lazar Srinivasan Prasad Rohana Chandrajith Patrick Roberts Gerd Gleixner 《第四纪科学杂志》2020,35(4):514-525
The catastrophic impact and unpredictability of the Indian Ocean Monsoon (IOM) over South Asia are evident from devastating floods, mudslides and droughts in one of the most densely populated regions of the globe. However, our understanding as to how the IOM has varied in the past, as well as its impact on local environments, remains limited. This is particularly the case for Sri Lanka, where erosional landscapes have limited the availability of well-stratified, high-resolution terrestrial archives. Here, we present novel data from an undisturbed sediment core retrieved from the coastal Bolgoda Lake. This includes the presentation of a revised Late Holocene age model as well as an innovative combination of pollen, source-specific biomarkers, and compound-specific stable carbon isotopes of n-alkanes to reconstruct the shifts in precipitation, salinity and vegetation cover. Our record documents variable climate between 3000 years and the present, with arid conditions c. 2334 and 2067 cal a bp. This extreme dry period was preceded and followed by more wet conditions. The high-resolution palaeoenvironmental reconstruction fills a major gap in our knowledge on the ramifications of IOM shifts across South Asia and provides insights during a time of major redistribution of dense human settlements across Sri Lanka. 相似文献
8.
Rohana Chandrajith Dinusha Chaturangani Sumith Abeykoon Johannes A. C. Barth Robert van Geldern E. A. N. V. Edirisinghe C. B. Dissanayake 《Environmental Earth Sciences》2014,72(3):867-877
The Panama coastal aquifer system is an important water resource in the southeast coast of Sri Lanka that provides adequate supplies of water for agriculture and domestic uses. One of the biggest threats to these fragile aquifers is the sea water intrusion. In this study, recharging mechanism and geochemical evaluation of groundwater in the coastal sandy aquifer of Panama were evaluated using chemical and stable isotope techniques. Thirty groundwater samples were collected and analyzed for their major ion concentrations and stable isotope ratios of oxygen (18O/16O) and hydrogen (D/H). All studied samples showed a ranking of major anions in the order Cl? > HCO 3 ? > SO 4 2? > N-NO3 ? while cations showed a decreasing order of abundance with Na+ > Ca2+ > Mg2+ > K+. Dominant groundwater hydrogeochemical types were Na–Cl and mixed Ca–Mg–Cl. Results of saturation index calculations indicate that the investigated groundwater body was mostly saturated with respect to calcite, dolomite and gypsum. In addition, stable isotope and geochemical data suggest that fresh groundwater in the aquifer is recharged mainly by local precipitation with slight modification from evaporation and saline water intrusions. Isotope data suggest that mixing of salt water with freshwater occurs in aquifers which are located towards the lagoon. Since the communities in the study area depend entirely on groundwater, an understanding of the hydrogeochemical characteristics of the aquifer system is extremely important for the better water resource management in the region. 相似文献
9.
Rohana Chandrajith Shirani Seneviratna Kumudu Wickramaarachchi T. Attanayake T. N. C. Aturaliya C. B. Dissanayake 《Environmental Earth Sciences》2010,60(1):193-201
The rising number of chronic kidney disease patients with no identifiable cause (CKD of uncertain aetiology), prevalent in
some areas of the dry zone of Sri Lanka is suspected to be related to the environmental exposure to heavy metals. Agricultural
soils are well recognized as being contaminated with potentially toxic metals from various forms of fertilizers and agro-chemicals,
which could easily enter the human body through the food chain. The objective of this paper is to determine the content of
heavy metals and activity concentration of background radionuclides such as K-40, Ra-226 and Th-232, in rice field soils.
Rice farming is the most common agricultural practice in the affected region and possible heavy metal sources such as fertilizers
are applied in abundance in the rice fields. Soils collected from a rice field in a non-CKD region was used for the comparison.
In dry zone soils, Ca, K, Ba, Pb and Zr contents were higher and Fe, Mn, Cr, Ni and Zn contents were lower compared to that
of soils from the wet zone non-CKD region. However, the activity concentration of soils was mostly the same in all samples,
except for the K-40 contents of the soils, which were higher in the rice field soils compared to the undisturbed forest soils
and also to the world averages. The mean U content was 3.6 mg/kg in the studied soils, although extremely high uranium contents
were found in some fertilizer samples particularly in the triple superphosphates. Most uranium applied via fertilizer could
contaminate the drinking water sources and even low uranium concentrations in drinking water may cause nephrotoxic effects. 相似文献
10.