Effect of Flora Density on Thermal Comfort in Urban Parks in Tropical Region: A Review

Urban areas are heating up due to escalating population and unlimited and unplanned building construction. Moreover, this heating up is more predominant in tropical micro-climate in urban settings. According to sustainable development programmes, urban greening and flora landscaping at urban contexts become more imperative to mitigate Urban Heat Island effect (UHI) and to enhance thermal comfort. It is revealed that flora population can increase the thermal comfort in urban settings. Flora population, its density and landscape can mainly influence to thermal comfort in parks significantly. In urban parks, thermal comfort improves via flora density, through modifying micro climatic conditions. High density of large canopy trees provides huge shade and decrease of air temperature, increase cooling intensity effectively. Considerable density of grasses and bushes carry out responsible roll on improving air quality and moderate micro climatic on thermal comfort. When selection flora species to urban parks, parameters like leaf area index, number of leaves and plant height can be considered as major requirements since these factors controlling solar radiation penetration which influence the temperature and thermal comfort. In order to provide appropriate thermal comfort conditions to urban parks, it is inevitable to design suitable landscape sketches against the challenge of less ground space to the highest flora density. Thermal comfort conditions in urban parks depending on air temperature, wind speed, solar radiation and absolute humidity, but all these factors can be influenced by flora population. In order to succeed the sustainable development programmes in tropical region countries, green urban spaces have been considered as vital component in the microclimate. By formulating appropriate park designs with greater flora density at compacted city areas, especially in tropical region, can increase thermal comfort which can assist urban planning to make better use of green spaces for microclimate regulation. Under this review, the strengths, weaknesses, opportunities and potential challenges of flora density on urban microclimate were highlighted and knowledge gaps were identified. Research priorities and future challenges that will support in urban planning with multi-prong strategies were also discussed.Keywords: Flora density, Urban parks, Thermal comfort, Landscap

Application of Infrared Thermography for Efficient Irrigation: A Review

Precision agriculture technologies have become more prominent and useful in prevailing commercial agriculture. Using precise amount of irrigation water will reduce the yield losses and minimises the possible water losses due to over irrigation. Irrigation opportunity time can be easily and effectively detected by infrared thermography. In infrared thermography heat patterns emitted from an object are used to create an infrared image. This image indicates the amount of energy emitted from the relevant object. This technique is non-invasive and can be used even from a distance. Promotion of this technology in agriculture is a good remedy for water scarcity and also to reduce the cost of production. The energy emitted by plants indicates the leaf temperature. There is a relationship between the leaf temperature and status of water within the plant. When the plants are in water stress, stoma gets closed to reduce the transpiration losses and as a result temperature rises up. In thermography this leaf temperature is measured and different levels of canopy temperatures are indicated in different colours and different shades of colours. Temperature values obtained from thermogram can be converted into crop water stress index (CWSI) and the status of water stress in crops can be understood with its use. According to the level of water stress amount of water to be applied can be determined. According to different colours in the thermal image water distribution can be planned. By using this technique, accurately crops can be irrigated on time before they acquire permanent wilting point and the water content in the root zone can be maintained in plant available water range. Further, this technique needs to be diffused more into the Sri Lankan agriculture sector as there are many farmers who are struggling with water scarcity. This paper is a comprehensive review of the possible application of the infrared thermography for irrigation scheduling, deciding the water distribution pattern in a crop field and a way to manage irrigation water efficiently.Keywords: Infrared thermography, Irrigation, CWSI, Temperatur

Development and Evaluation of Experimental Green Roof Modular System for Tropical Climate

World population is increasing rapidly in urban areas of developing countries than that of developed countries. World urbanisation has also been extensively accelerated since past few decades. As a result, urban heat island phenomenon has taken place; Heat island effect in cities is mainly because of non-natural heat absorbing materials used in buildings and other manmade structures. Natural greenery in the cities has been replaced by concrete yards and most of the cities acceleration with urbanisation with more and more concrete structures. Addition of green infrastructure to cities is also an issue due to lack of sufficient space. Green roofs are now gaining increasing attention in many countries. Green roofing is one of the few technologies of passive cooling for buildings in present society. The modular green roofing system has become one of the best solutions to overcome problems related with thermal comfort in urban areas. The aim of this research was to develop a portable module for the green roof with low weight, less maintenance and with the best edible leafy vegetable variety by considering growth performances of selected varieties. The module was developed by using fiber glass with an area of 1000×500 cm2 and a unit weight of 700g-800g. The frame network was fabricated by using wooden strips. Growth medium was prepared by using coir fiber, coco husk and compost mixed media at 1:1:1 ratio. Coco husk chips used as boundary layer. Thickness of the substrate layer was not exceeded 25 mm. Centella asiatica and Horse puslane were used as the vegetation for green roof modules. No of leaves, plant height, plant density and chlorophyll content of leaves were used as the parameters to select the appropriate plant variety for the green roof. Horse puslane was selected as the best plant variety for the modules after the statistical analyses.Keywords: Centella asiatica, Chlorophyll content, Green roof modules, Green roofs, Growing mediu

Wild Grass Types as Green Roofing Materials for Urban Landscapes in a Tropical Climate

Urban cities, especially in tropical context emphasis on alternative green covers namely green roofs in order to mitigate Urban Heat Island Effect. Grass is a widespread green roofing material, predominantly for extensive green roofs. This study was aimed (a) to explore the growth performance of selected wild grass types under different irrigation conditions and (b) to select the most suitable wild grass type for green roofs under minimum irrigation in tropics. Five wild grass types (belongs to Genus Digitaria, Genus Chrysopogon, Genus Cynodon, Genus Panicum and Genus Isachene) were selected and they were tested with Bouteolea dactyloides (Buffalo grass) as the control on reinforced concrete slab models. Performances of the grasses were evaluated under two irrigation schedules; irrigation once in five days (I1) and irrigation once in 10 days (I2).Tested parameters were vertical growth, horizontal growth, plant survival percentage, Leaf Area Index (LAI), root density, leaf density, grass density and ranking procedure for visual appearance. Results of this study indicated that under both irrigation schedules, Digitaria spp. showed the highest performances (After six weeks of treatments, for I1 and I2; vertical growth: 6.2 cm and 6.0 cm , horizontal growth: 17.6 cm and 16.1 cm , plant survival percentage: 99.1% and 97.8% , LAI: 0.64 and 0.58 , root density: 0.0017 g/cm3 and 0.0014 g/cm3, leaf density: 0.0013 g/cm3 and 0.0012 g/cm3 , grass density: 0.0043 g/cm3 and 0.0042 g/cm3, respectively) and Panicum spp. showed the lowest performances (After six weeks of treatments, for I1 and I2; vertical growth: 15.11 cm and 14.8 cm , horizontal growth: 7.2 cm and 6.5 cm , plant survival percentage: 96% and 92.5% , LAI: 0.47 and 0.43 , root density: 0.0013 g/cm3 and 0.0012 g/cm3, leaf density: 0.0011 g/cm3 and 0.0009 g/cm3 , grass density: 0.003 g/cm3 and 0.0025 g/cm3, respectively) compared to Bouteolea dactyloides while Chrysopogon spp. showed better growth performances next to Digitaria spp. Though Isachene spp. showed better ground coverage compared with Digitaria spp., it showed less plant survival percentage. Therefore, Isachene spp. is not suitable as a green roofing material in tropical context. Digitaria spp. is the best wild grass spp. from the selected wild grasses which gave high tolerance for water scarcity in tropical context under tested irrigation schedules. Further researches should be carried out beyond three months for further evaluation of growth performances of the selected grass spp.Keywords: Green roofing materials, Tropical context, Wild grasse

Evaluation of Ambient Air Particulate Matter (PM) Concentration in Urban Context and its Public Perception

Urban air pollution has become a global issue and vehicle emissions, rapid industrialization, and urbanization are known to be the main contributing factors for air pollution. Therefore, air quality monitoring is essential for detecting air pollution levels mainly in urban areas. Among the main air pollutants, particulate matters (PM) play major roles as an urban air pollutant. The objectives of this research study were (a) to evaluate and compare the PM2.5 concentration on ambient air in selected locations in Colombo urban area (b) to calculate air quality index (AQI) to identify the pollutant levels of ambient air in selected study sites and (c) to identify the public perception and awareness regarding the PM-related air pollution. In this research, ambient PM2.5 concentrations were measured by ambient fine dust air sampling techniques in selected locations in Colombo urban area representing commercial, construction, and residential sites. Evaluation and comparison of PM2.5 concentration and questionnaire survey were analysed by using suitable statistical approaches and softwares. The comparisons were made with appropriate WHO standards and its related Sri Lankan standards for air quality guidelines. One sample t-test was used to compare the monitored PM2.5 concentration with the standard PM2.5 concentration. One way ANOVA test and Tukey pair wise comparison test were used to evaluate the significant difference between each category. All the statistical analysis was done by using Minitab 18.0 version. SPSS 16.3 version was used to analyse the survey results. Results of the study indicated that residential areas having significantly low concentrations of PM2.5 concentration while both commercial and construction areas having high concentrations of PM2.5 concentration. The highest PM2.5 concentration were 101.08 μɡ/m3 and it was recorded in Maradana area which came under the commercial category. The lowest PM2.5 concentration was recorded in Kotte representing the residential area. There was no any significant difference of PM2.5 concentration between commercial and construction sites mainly including Borella, Maradana, Peliyagoda and Kelaniya areas. In addition, there was a significant difference between PM2.5 concentrations of selected commercial and residential areas and construction and residential areas. PM2.5 concentrations were varied into the range of 17.23 - 101.08 ɥɡ/m3 in commercial and construction areas and 5.68-26.08 ɥɡ/m3 in residential areas. Calculated AQI by using mean PM 2.5 concentration values in air sampling locations indicated that commercial and construction areas consist with moderate air quality level under the AQI category of 51-100 and residential areas consist with good air quality level under the AQI category of 0-51. Public awareness about the PM-related air pollution is considerably low and majority of the people were mentioned that the air quality is not good in Colombo urban area. Approximately half of the interviewed people were affected to the poor air quality and its related health effects. According to public perception, vehicular emission is the main particulate matter emission source in Colombo area.Keywords: Air quality index, Particulate matter, Urban air pollutio

Sustainable City Development and its Importance in the Sri Lankan Context: A Review

Approximately 70 out 100 people in the world will live in cities by 2050, as a result of rapid urbanization and population increment. The UN agenda of 2030 was identified cities as the key players of the arts and culture, thriving businesses, and innovative ideas. Urbanization leads to different environmental, economic and social issues. One billion urban poor still live in slums and informal settlements, mostly in Asia, Africa, and Latin America, and are often excluded from access to affordable housing, good-quality basic services, and better jobs. Over 90% of urban areas are located in disaster vulnerable areas (coastal or flood prone) which means that most cities are affected by the climate crisis and natural disasters as sea levels rise, floods, and powerful storms sweep across these regions. Sustainable city concept assures the economically viable, environmentally sound and socially acceptable cities in the world. In 2017, 18.48% of Sri Lanka's population has been living in urban areas and cities. Colombo is considered as the Sri Lanka's largest city with more than 5.6 million metro area residents and Sri Jayawardanapura, Kandy, Galle, Trincomalee and Gampaha are referred as other large cities. Ministry of Megapolis and Western Development has estimated that 43.8% of the Sri Lankan population in 2030 to be living in urban areas and specialized technical support in solid waste management and other urban issues to be prioritized under the urban governance support program. Sustainable development goal No.11 deals with the attributes of sustainable cities, highlighting a range of issues, from the liveability of cities to their resilience to climate change. The sustainable city concept is very much important to national sustainable development program in Sri Lanka with stand of Vision 2025 and the Public Investment Program 2017-2020. The provincial capital of Anuradhapura is a good example of an ancient sustainable city with an abundance of green spaces and practices. Sustainable city development focuses on city planning and management to maintain better infrastructure facilities, high quality drainage systems, better land use practices and reduced disaster risk of the city. Furthermore, it increases public services and utilities, such as sewerage, waste disposal, and public transport to facilitate high living standards for urban communities. Government should be incorporated in sustainable city development in Sri Lanka by developing policies, projects, awareness programs, educational programs and providing funds. This study comprehensively reviews the existing literature on (i) sustainable city concept, (ii) its importance, (iii) sustainable city development in Sri Lanka, (iv) barriers and (v) future perspectives.Keywords: Disaster risk reduction, Heat island effect, Urbanization, Waste managemen

Current Status, Requirements and Opportunities for Green Building in Sri Lanka

The construction sector is responsible for a large percentage of the world’s total energy consumption and greenhouse gas emissions. Therefore, the concept of green building has become one of the effective forefronts for the sustainable development. With the global trend, Sri Lanka also has put the interest on adopting the green concept. This paper examines the current status, opportunities, benefits and challenges in associated with green buildings and a comparison between GREENSL rating system for built environment which is developed by Green Building Council of Sri Lanka (GBCSL) and LEED Leadership in Energy and Environmental Design which is developed by United States Green Building Council(USGBC). Through the concept of green building it provides significant benefits over traditional construction practices. Reducing consumption by incorporating energy and water efficient mechanisms, combining renewable energy, improving indoor air quality and upgrading the health and comfortability of occupants, reduction of waste, reduced life cycle cost (LCC) and increased life span of the building are some of the major drives. However there are some challenges for the implementation of green construction projects. 5-10% of higher initial costs, fear of unknown, technical difficulties during the construction process, lengthy approval process are some of the main barriers for the widespread of this concept. The quality of green buildings can be assessed by green certifications used in Sri Lanka. When aiming for green building certification, property developers have two crucial options namely LEED and GREENSL. There are 7 criteria under LEED and GREENSL, respectively. Sustainable site, water efficiency, energy and atmosphere, indoor air quality and innovation design are the criteria common to both rating systems. Management and social and cultural awareness are the two criteria additionally used by GREENSL and regional priority is the criterion specific to LEED. By observing these criteria it is evident that both rating systems have common objectives. Comparatively GREENSL has been developed by considering our own requirements. Therefore, it is much more appropriate to Sri Lankan context. Similarly it was observed that the same rating system is used for each and every building type within the construction sector. Considering the facts it can be suggested that different rating systems with different criteria can be developed and use as the structure of the building is different to each other. Meantime it is essential for the government to implement policies to obtain green certification for every structure build in the construction sector.Keywords: GREENSL, Green Building, Indoor air quality, LEED, Water efficienc

Assessment of Irrigation Scheduling in Pelwatte Seed Cane Plantation

Sugarcane (Saccharum officinarum L) is mainly grown in the dry zone of Sri Lanka wherethe major soil group is well drained Reddish Brown Earth. Pelwatte Sugar Industries Limitedcultivates more than 4,000 hectare of sugarcane. Uneven and unpredictable rainfall in the dryzone makes it necessary of the irrigation. This research project was conducted to develop analternative system to overcome weaknesses of the existing irrigation system. Irrigationinterval, irrigation time and net irrigation depth was measured via a number of equations,which used in irrigation scheduling. Distribution uniformity was found by three can tests forexisting and suggested spacing and those tests were helpful to find irrigation rate. Othermiscellaneous practices are equal for both suggested and existing systems. Irrigation intervalof the existing system is around 10 to 14 days. Irrigation time is 3 hours. Irrigation rate of thesystem is 6.30 mm hr-1. Net irrigation depth is 18.7 mm; hence water requirement per hectareis 186.75 m3. Spacing used in existing sprinkler system is 18 m × 18 m and averagedistribution uniformity is 55.71%. Area covered in a day is 1.7 hectare. Fuel cost per hectareis Rs. 3,395.00. Suggested irrigation interval of the study was 14 days. Net irrigation depthwas 33.2 mm. Two spacing systems were suggested, 18 m × 12 m spacing system and 12 m ×12m system. Distribution uniformity and discharge rate increment of the two systems wasstatistically significant over existing system. Their values and corresponding p values are70.8%, 0.026 and 10.427 mm hr-1, 0.002 for 18 m × 12 m system and 83.5%, 0.007 and 16.6mm hr-1, 0.014 for 12 m × 12m system respectively. Irrigation time, area covered within aday, water requirement per hectare and fuel cost per hectare for 18 m × 12 m system areconsecutively 3 hours and 11 minutes, 1.2 hectare, 332.49 m3 and Rs. 6,034.00 and for 12 m× 12 m system are 2 hours, 1.1 hectare, 332.49 m3 and Rs. 5,060.00. It can be concluded thatboth suggested systems were improved distribution uniformity and irrigation ratesignificantly. Moreover, net irrigation depth of the new system was almost twice compared toexisting system, which explains the inadequate wetting of the existing system. 12 m × 12 msystem is superior over both 18 m × 12 m spacing and existing system

Application of Crop Simulation Models as a Strategy for Climate Change Risk Assessment and Adaptation in Agricultural Systems.

Continuing global population growth which is projected to be reaching 9.8 billion by 2050, will remain a substantial risk on global food security remaining an unprecedented demand for food which will exceeding by 70%-100%. Agricultural systems are focusing on fulfilling the increasing demands intensively where agricultural systems are greatly influenced by climate change which is hardly adaptable; leading reduction of crop yields due to its high dependency on variations in weather. Elevated temperature and carbon dioxide affects the biological processes like respiration, photosynthesis, plant growth, reproduction and water use. Thus, the variability of climate and associated weather extremes has become a major concern of modern science where crop models are accepted as adequate tools for decision making in relevant aspects. Crop simulation models are computer programs that use quantitative descriptions of physiological processes to mimic plant growth and development as influenced by environmental conditions and crop management. The applications of crop models have been extended across regions at multiple scales to assess the impacts of climate change and identify adaptation strategies. Proper understanding of the effects of climate change will help optimising crop management decisions initiating from selection of crop cultivars, sowing dates, fertilising and irrigation scheduling, to minimize the risks. Crop models are functional in assisting the breeding programs, developing new crop rotations and maximising the value of seasonal climate forecasts. They have facilitated extrapolation and establishment of new hypothesis for climate change studies, stimulated investigations into climate change adaptation, and assisted in communicating to the public and policy makers. Much of the current focus on climate change risk assessment is concentrated on stringent 1.5–2o C limit on global warming as agreed at international climate negotiations in Paris, 2015 (COP21). Decision Support System for Agro-Technology Transfer (DSSAT), Agricultural Production Systems Simulator (APSIM), CERES (Crop Environment Resource Synthesis) and Aqua crop models are among widely using crop models in worldwide. Combining climate change and crop models to predict impacts of climate change on crop productivity can ultimately guide planning of climate change adaptation strategies to ensure future food security. However, the consistency of these models and experimental data has been debated where the ability to simulate impacts of high CO2 and climate variability are doubted. Integrated limiting factors including soil nutrients, pests and weeds are neither fully understood nor well implemented in prominent models. Targeted model developments are important to be focused on the interactions of abiotic; biotic factors and plant genetic variability with elevated CO2 and temperatures together with their effects on harvest. Future crop modeling will incorporate risk assessment approach with greenhouse gas emission scenarios and regional climate models. This paper reviews applications of crop models in climate change simulation with their advantages, disadvantages and future perspectives.Keywords: Climate change, Crop models, Agriculture, Risk assessment, Adaptatio

Comparative Assessment of Trace Element Accumulation in Traditional and Improved Rice (Oryza sativa L.) Varieties Grown with Organic, Chemical and Non-Fertilizers

Oryza sativa L., is the most widely grown rice in Sri Lanka. At present, farmers are using both organic and chemical fertilisers for the paddy cultivation. There is growing concern about heavy metal (mainly As, Cd and Pb) build up in the soils because they enter the soil and the plants via application of fertilisers (anthropogenic). Heavy metals are also found in the soil (geogenic). Cd and As are both nephrotoxic and neurotoxic, and there is a concern that they may be involved in the chronic kidney disease of uncertain etiology (CKDu) prevalent in the North Central Province and neighboring areas. According to the Food and Agriculture Organization (FAO), the maximum allowable limit (MAL) of Cd and As is 0.2 μg g-1. This study was conducted to compare the heavy metal accumulation in traditional and improved rice varieties grown with organic fertilisers, chemical fertilisers and without fertilisers. Total of 126 paddy samples (including seven traditional and seven improved rice varieties) grown with organic, chemical and non-fertiliser, were collected directly from the paddy fields in Rice Research and Development Institute (RRDI) at Batalagoda. Soil samples from paddy plots with different fertiliser treatments were collected. Heavy metal analysis was done at the Geology Department of the University of Peradeniya by using ThermoICapQ Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Rice cultivated with chemical fertilisers had the highest mean heavy metal concentrations. Cd concentration (0.32 μg Cd g-1) in traditional varieties grown with chemical fertilisers was significantly higher than in the other treatments. That value is 1.6 fold higher than the MAL. Organic fertiliser treated improved varieties had the lowest level of Cd and it was less than the MAL. All the other treatments had Cd levels more than the MAL. All treatments had lower content of As than the MAL. Taken as a whole, macro-nutrients (K, Ca, Mg) were higher in the chemical fertiliser treated rice than that of organic treated rice. Heavy metals and macro-nutrient concentrations varied from variety to variety.Keywords: Chemical fertiliser, Heavy metals, Improved rice, Organic fertilizer, Traditional ric