Assessment of Atmospheric Deposition and Spatial Variability of Trace Metals in Kandy City and Suburbs using Bio-monitoring Technique in Mosses

Deposition of atmospheric Trace metals (TMs) was investigated in this study through the analysis of mosses that have been grown at nine locations within the Kandy Municipal Council area and its suburbs. Hyophila sp. moss was selected for TM analysis with referring their common availability. After cleaning, dried mosses samples were digested with conc. HNO3 in microwave digesting system. Digested samples were analysed for Al, Cr, Mn, Fe, Ni, Cu, Zn, Cd and Pb using Inductive Coupled Plasma-Mass Spectrometry (ICP-MS). Average TM concentrations in mosses, were resulted with the order of Fe>Al>Zn>Mn>Cu> Pb> Cr>Ni>Cd. The highest and lowest metal concentrations were recorded for Al and Cd as 12,150 and 0.2 mg/kg respectively. Principle factor analysis suggested two major factors; vehicular emission and geographical location, responsible for the TM concentrations in mosses. Factor analysis indicated that approximately about 73% of the TMs in the atmosphere are by the two factors whereas majority from that to be from the vehicular emission. Apart from that, trans-boundary pollution could identify as one of the major factors for TMs in Kandy. Spatial distributions are not significant for the metals that have identified as geogenic origin and others were reported with clear spatial distribution with having highest accumulations in the areas those experiencing higher traffic activities. The ecosystem risk values are still in the acceptable levels in the means of trace metals in mosses. Key words: mosses, bio-monitoring, trace metals, atmospheric depositio

Selective removal of arsenic in water: A critical review

Selective removal of arsenic (As) is the key challenge for any of As removal mechanisms as this not only increases the efficiency of removal of the main As species (neutral As(III) and As(V) hydroxyl-anions) but also allows for a significant reduction of waste as it does not co-remove other solutes. Selective removal has a number of benefits: it increases the capacity and lifetime of units while lowering the cost of the process. Therefore, a sustainable selective mitigation method should be considered concerning the economic resources available, the ability of infrastructure to sustain water treatment, and the options for reuse and/or safe disposal of treatment residuals. Several methods of selective As removal have been developed, such as precipitation, adsorption and modified iron and ligand exchange. The biggest challenge in selective removal of As is the presence of phosphate in water which is chemically comparable with As(V). There are two types of mechanisms involved with As removal: Coulombic or ion exchange; and Lewis acid-base interaction. Solution pH is one of the major controlling factors limiting removal efficiency since most of the above-mentioned methods depend on complexation through electrostatic effects. The different features of two different As species make the selective removal process more difficult, especially under natural conditions. Most of the selective As removal methods involve hydrated Fe(III) oxides through Lewis acid-base interaction. Microbiological methods have been studied recently for selective removal of As, and although there have been only a small number of studies, the method shows remarkable results and indicates positive prospects for the future

Hydrogels: Novel materials for contaminant removal in water—A review

This review focuses on contaminant removal from water using hydrogel-based materials. It highlights the recent results achieved, unresolved problems, and possible developments. Polymer and graphene hydrogels are promising new materials for removing inorganic (e.g., metals and metalloids) and organic (e.g., dyes) trace contaminants from water. They can be prepared as composites with practically any desired conventional or innovative adsorbent, to enhance the removal efficiency. Obtaining a three-dimensional highly effective network is one of the significant features of hydrogels, which confer specific characteristics on them. There are number of benefits of using hydrogels: easy separation and handling, the facility for large-scale application, and the ability to regenerate and reuse the hydrogels. At present, the experiments based on hydrogels for water purification are mostly limited to the laboratory scale and further research needed to move toward large-scale industrial applications. Moreover, the present studies are currently limited to a few types of contaminants, so that further experiments needed for removal of more contaminant types and mixtures of contaminants, considering that in practical situations. All these features are described and discussed in this review, which, to the best of our knowledge, is the first comprehensive review on hydrogel applications for contaminant removal from water

Health risk assessment of heavy metals in atmospheric deposition in a congested city environment in a developing country: Kandy City, Sri Lanka

This research study which was undertaken in a congested city environment in a developing country provides a robust approach for the assessment and management of human health risk associated with atmospheric heavy metals. The case study area was Kandy City, which is the second largest city in Sri Lanka and bears the characteristics of a typical city in the developing world such as the urban footprint, high population density and traffic congestion. Atmospheric deposition samples were collected on a weekly basis and analyzed for nine heavy metals common to urban environments, namely, Al, Cr, Mn, Fe, Ni, Cu, Zn, Cd and Pb. Health risk was assessed using hazard quotient (HQ) and hazard index (HI),while the cancer risk was evaluated based on life time daily cancer risk. Al and Fe were found to be in relatively high concentrations due to the influence of both, natural and anthropogenic sources. High Zn loads were attributed to vehicular emissions and the wide use of Zn coated building materials. Contamination factor and geo-accumulation index showed that currently, Al and Fe are at uncontaminated levels and other metals are in the range of uncontaminated to contaminated levels, but with the potential to exacerbate in the long-term. The health risk assessment showed that the influence of the three exposure pathways were in the order of ingestion>dermal contact>inhalation. The HQ and HI values for children for the nine heavy metals were higher than that for adults, indicating that children may be subjected to potentially higher health risk than adults. The study methodology and outcomes provide fundamental knowledge to regulatory authorities to determine appropriate mitigation measures in relation to HM pollution in city environments in the developing world, where to-date only very limited research has been undertaken

Microorganisms and heavy metals associated with atmospheric deposition in a congested urban environment of a developing country: Sri Lanka

Highlights - Nine bacterial species were identified, six Gram-negative and three Gram-positive. - Al and Fe, geogenic in origin and may be re-deposited by vehicular traffic. - High Cr, Mn, Ni, Cu, Cd and Pb are traffic influenced, galvanized roofs release Zn. - Bacteria and heavy metals in deposition create human and ecosystem health risks. Abstract The presence of bacteria and heavy metals in atmospheric deposition were investigated in Kandy, Sri Lanka, which is a typical city in the developing world with significant traffic congestion. Atmospheric deposition samples were analyzed for Al, Cr, Mn, Fe, Ni, Cu, Zn, Cd and Pb which are heavy metals common to urban environments. Al and Fe were found in high concentrations due to the presence of natural sources, but may also be re-suspended by vehicular traffic. Relatively high concentrations of toxic metals such as Cr, and Pb in dissolved form were also found. High Zn loads can be attributed to vehicular emissions and the wide use of Zn coated roofing materials. The metal loads in wet deposition showed higher concentrations compared to dry deposition. The metal concentrations among the different sampling sites significantly differ from each other depending on the traffic conditions. Industrial activities are not significant in Kandy City. Consequently, the traffic exerts high influence on heavy metal loadings. As part of the bacterial investigations, nine species of culturable bacteria, namely; Sphingomonas sp., Pseudomonas aeruginosa, Pseudomonas monteilii, Klebsiella pneumonia, Ochrobactrum intermedium, Leclercia adecarboxylata, Exiguobacterium sp., Bacillus pumilus and Kocuria kristinae, which are opportunistic pathogens, were identified. This is the first time Pseudomonas monteilii and Ochrobactrum intermedium has been reported from a country in Asia. The culturable fraction constituted ~0.01 to 10%. Pigmented bacteria and endospore forming bacteria were copious in the atmospheric depositions due to their capability to withstand harsh environmental conditions. The presence of pathogenic bacteria and heavy metals creates potential human and ecosystem health risk