Farah Ayuni Shafie

Urban metabolism using economic input-output analysis for the city of Barcelona

Environmental impacts of cities are a growing concern because of the expanding population, growing demand of natural resources and production of pollutants to the environment. The urban metabolism concept stands on the basic ground that all the movement or flow of materials within an urban system can be accounted systematically. The Economic Input–Output analysis method is applied to the city of Barcelona, Spain as a system boundary to estimate the materials and energy resources required for and the environmental emissions resulting from activities in the economy. Economic input–output analysis is used as an approach to analyze a town metabolism with a demand-based approach. Many inputs and outputs ranging from residential, transportation, consumptions and services can be looked upon in the urban system. Some of the resulting impact of a city are not always immediate and direct, therefore only a complete examination of the urban system could observe those resulting impacts. Through urban metabolism approach, decision are hoped to be made in a more deliberate and systematic way. Limitation to the practice of urban metabolism via economic input–output analysis such as lacking of local and regional data is also addressed.

Heavy Metals Concentration in Water Convolvulus (Ipomoea aquatica and Ipomoea reptans) and Potential Health Risk

Water convolvulus (Ipomoea aquatica and Ipomoea reptans) or their Malay name “kangkung” is tropical, semiaquatic, and fast-growing vegetables belonging to the morning glory family. They are among the green leafy vegetables widely consumed by Malaysian population. However, excessive use of fertilizer and pesticides in “kangkung” cultivation and contaminated source of irrigation may cause harm to the human health. Samples of Ipomea were collected from local wet market and supermarket, and digested and analyzed by Atomic Absorption Spectrophotometer (AAS). There were significant differences of heavy metal concentration for zinc, copper, manganese, and nickel in both species. The average concentration of Fe, Mn, Zn, Cu, and Ni in I. aquatica was found to be 270.20, 91.14, 32.95, 3.99, and 1.79 mg/kg, respectively, while Fe, Mn, Zn, Cu, and Ni in I. reptans was 275.97, 212.63, 87.33, 18.56, and 3.14 mg/kg, respectively. The daily intake of aforementioned heavy metals was within the safe limit values under Malaysia Food Regulations 1985 and World Health Organization’s provisional tolerable daily intake. Subsequently, the Health Risk Index (HRI) for daily intake of Fe, Zn, Cu, and Ni was less than 1 except for Mn (HRI > 1) indicating possible health effect upon consumption. The use of fertilizers and pesticides should be monitored, and regular sampling of the vegetables is recommended to minimize the heavy metal uptake by water convolvulus, thus reducing human exposure.