Soil erosion is one of the major threats which affects farm productivity and water quality in river catchments. Quantification of human-induced soil loss is an imperative measure in catchment management. Among the catchments in Sri Lanka, the highest sediment yield has been reported from the Upper Uma Oya catchment (UOC) which is a sub-catchment of the Upper Mahaweli catchment. The Mahaweli watershed is the most important watershed in Sri Lanka since the size and the economic importance of it. Hence, this study was conducted considering the ten selected sub-watersheds of Uma Oya Watershed (UOW) in Sri Lanka to quantify soil erosion. Soil erosion of UOW was calculated using Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) Sediment Delivery Ratio (SDR) model. It was found that the current soil erosion rates in the watershed is varied between 14.0-648.6 t/ha/yr. Results of the study disclose that the soil erosion rates of UOW are 3 to 130 times faster than the soil loss tolerance in Sri Lanka. Findings of the study suggest that the implementation of sustainable watershed management options are crucial in order to reduce soil erosion and to enhance the quality of the watershed.

This study validated two underivatized methods (M1 and M2) according to the Eurachem guidelines to analyze the herbicide Glyphosate and its major metabolite aminomethylphosphonic acid simultaneously by liquid chromatographytandem mass spectrometry in both fresh and hard waters. Samples were analyzed directly after filtration through 0.22 μm syringe filters in M1, while samples were acidified with acetic acid before filtration in M2. Spike recoveries were greater than 80% for Glyphosate and aminomethylphosphonic acid in both methods. The limit of quantitation was 0.5 μg/L for M1, and 0.1 μg/L for M2 by using matrix-matched calibrations. The linear regression coefficient of both methods was greater than 0.995. The expanded uncertainty was found to be less than 25% for both. Moreover, M1 has an additional mass spectral confirmation ability, and the column and the mobile phase used in M2 can be used to analyze the inert surfactant used in Glyphosate formulations, Polyethoxylated tallow amine. The accuracy of the developed methods was assured by participating in a proficiency testing program against M2 and conducting the t-test for results generated by both M1 and M2. Both methods, therefore, can be used to determine Glyphosate and aminomethylphosphonic acid content concurrently in fresh and hard waters.

p < 0.05), adoption of chemical pesticide reduction methods (χ2 = 12.452, p < 0.05) and received training on effective use of pesticides (χ2 = 9.427, p < 0.05). Several reasons of misuse of pesticides by farmers were identified. Among them, lack of technical knowledge on pesticide application and integrated pest management (IPM) practices were the main courses. Most of the farmers tend to use pesticides as a precautionary safety measure before any pest or disease symptoms emerge. Further, pesticide retailers had a strong influence on the selection of pesticides by farmers suggesting that agro-marketing has a significant influence over pesticide usage among farmers. The canonical correspondence analysis indicates that farmers' knowledge of the correct handling of pesticides were positively influenced by the farmers' level of education and training received on pesticide usage (p < 0.05). The study suggests the importance of training, extension services and farmer education to improve the levels of knowledge and awareness of farmers on the risks of pesticides to human health and environmental pollution.

This article is published under the Creative Commons CC-BY-ND License (http://creativecommons.org/licenses/by-nd/4.0/). This license permits use, distribution and reproduction, commercial and non-commercial, provided that the original work is properly cited and is not changed anyway.Abstract: Safe and ample supply of freshwater is fundamental to humans and for the sustainability of ecosystem function. Therefore, impacts of catchment disturbances on surface water quality have been given special attention currently. The Badulu Oya sub-catchment of the Upper Mahaweli catchment area in Sri Lanka is one of the landscapes affected by intensive agricultural activities and urban development. This study was aimed at evaluating the spatial and temporal variation of water quality, stream physical habitat quality and macroinvertebrate bioindicators in the Badulu Oya catchment area in relation to disturbances due to agricultural and urban practices. Physicochemical water quality parameters and macroinvertebrate indices were evaluated at ten sampling sites in the Badulu Oya catchment area within a one year period. The results revealed that water quality variables such as electrical conductivity (EC), total solids (TS), total dissolved solids (TDS), dissolved oxygen (DO), alkalinity, nitrate-N(NO 3 -N) and physical variables such as stream channel quality index (CQI) and riparian quality index (RQI) catchment disturbances. Among the macroinvertebrate indices present study revealed that the land use practices of Badulu Oya health. Similarly the study also revealed the prospect of using attributes such as water quality, physical habitat quality and macroinvertebrate bioindices for river health monitoring programmes.

Phosphorus is one of the major nutrients that have been identified as a limited resource that would end up earlier than predicted at the rate of current consumption. Therefore, attempts to recover phosphorus from waste and its subsequent use are a concern of current researchers. Nevertheless, recovery of nutrients from wastewater is cumbersome because nutrients such as phosphates (3 4 PO −) and nitrates (3 NO −) prefer to remain in aqueous phase rather than being adsorbed on solid matrixes. Investigation of adsorption of available 3 4 PO −-P from simulated brackish water, on granulated solid waste material, prepared by crushed autoclaved aerated concrete (CAAC), and subsequent use of the material as phosphate fertilizer would be the focus of this research. Treatment of nutrient-rich brackish water is important because such water is discharged in huge volume at the time of harvesting of shrimp aquaculture ponds. Experiments conducted in simulated brackish water confirmed non-linear adsorption association with changing distribution coefficient (K D) which attributed the maximum removal of about 98% 3 4 PO −-P from 100 mg•dm −3 solution at its value of 40. The non-linear adsorption supported by both the Langumuir and the Freundlich isotherm models simultaneously satisfied monolayer adsorption and multilayer adsorption depicted by the regression coefficients of greater than .99 by the linearized forms of the isotherm models. Moreover, promising phosphate uptakes characteristics are exhibited by the adsorbent at the process of repetitive adsorption which resulted in 12 g/kg uptake of phosphate at 81% efficiency. The adsorbent seems to be used as a slow-released phosphorus fertilizer at the end of its life as an adsorbent.