Assessing the suitability of the SLEUTH cellular automata model for capturing heterogeneous urban growth in developing cities: A case study in Northern Nigeria.

Cellular automata (CA) models like SLEUTH (an acronym for slope, land use, excluded area, urban extent, transport-network and hill shade) have predominantly been developed and applied in developed countries. Modeling can serve as a tool to guide policy measures in facing urbanization challenges. However, developing cities have peculiar differences (heterogeneity, poor planning, and low infrastructure) thus the existing modeling approaches may not be able to apprehend heterogeneous urban growth. This research will use selected cities with similar spatial extents as controls but disparate urban extents, and growth indices to analyze the performance of SLEUTH simulations. Presumably, a comparison of the model simulations of the cities would display some significant differences, due to these variations and the scale of observation that has to be used for the model simulations. The results for the successfully calibrated cities (Kano/Funtua couple: 0.48/0.02. Katsina/Kaduna: 0.48/0.83 respectively) showed that in each city couple, the more expansive city with the most compact urban settlement pattern had a higher prediction accuracy, also predicted images of the cities showed underestimation of the urban areas over the years with the exception of Katsina city. The study further showed the model's effectiveness in modeling cities in developing countries, such as Nigeria. It is recommended that the type of urban growth experienced by cities be taken into consideration when implementing SLEUTH. Limitations of the study are centered on the inherent limitations of the model, the possibility of the occurrence of errors in data preparation, the scale and urban settlement type, which play an important role in the success of the calibration. Future research could be focused on adding other relevant inputs to the model and creating a metric that ascertains the best satellite image resolutions for a particular study area's growth coefficient values.

Seasonal variation and source identification of heavy metal(loid) contamination in peri-urban farms of Hue city, Vietnam.

This study focused on the seasonal variation and source identification of heavy metals (HMs) while considering effects of municipal wastewater (MWW) in peri-urban farms of Hue city, central Vietnam. Moreover, associated non-carcinogenic and carcinogenic health risks from consuming vegetables containing HMs were also assessed considering the hazard quotient and cancer risk, respectively. Therefore, concentrations of Fe, Mn, Zn, Cu, Cr, Cd, Pb, and As were determined in irrigation water, soil, and lettuce samples collected during dry and wet seasons from one upstream site where irrigation water has no impact on MWW as well as from two downstream sites in farms on the outskirt of the city. Although irrigation water and soil in the same farms were not polluted as strongly, lettuce samples were polluted with Cd, Zn, and Pb. Furthermore, levels of soil Cu and As and HMs (except for Cu) in lettuce in the wet season were significantly higher (p < 0.05) than those in the dry season, indicating the impact of MWW with seasonal change. The health risk assessment via lettuce consumption demonstrated an unacceptable carcinogenic risk owing to Cd and a cumulative non-carcinogenic risk owing to selected HMs in the lettuce, while all other risks were negligible. Correlation and principal component analyses were performed to identify HM sources, indicating that Cu, Zn, Cd, Pb, Cr, and As in irrigation water and soil could have anthropogenic sources (e.g., untreated MWW, fertilizer use); meanwhile, irrigation-water and soil Fe, Mn, As, and Cr could originate from non-anthropogenic sources (e.g., parent materials weathering). This study revealed that rapid urbanization together with high precipitation leading to urban floods in Hue city was a significant factor spreading HMs in agricultural farms, suggesting the importance of wastewater treatment system, which can reduce the HM load in the city to protect the local food production.

Assessing the impacts of climate change in cities and their adaptive capacity: Towards transformative approaches to climate change adaptation and poverty reduction in urban areas in a set of developing countries.

Many cities across the world are facing many problems climate change poses to their populations, communities and infrastructure. These vary from increased exposures to floods, to discomfort due to urban heat, depending on their geographical locations and settings. However, even though some cities have a greater ability to cope with climate change challenges, many struggle to do so, particularly in cities in developing countries. In addition, there is a shortage of international studies which examine the links between climate change adaptation and cities, and which at the same time draw some successful examples of good practice, which may assist future efforts. This paper is an attempt to address this information need. The aim of this paper is to analyse the extent to which cities in a sample of developing countries are attempting to pursue climate change adaptation and the problems which hinder this process. Its goal is to showcase examples of initiatives and good practice in transformative adaptation, which may be replicable elsewhere. To this purpose, the paper describes some trends related to climate change in a set of cities in developing countries across different continents, including one of the smallest capital cities (Georgetown, Guyana) and Shanghai, one the world's most populous cities. In particular, it analyses their degree of vulnerability, how they manage to cope with climate change impacts, and the policies being implemented to aid adaptation. It also suggests the use of transformative approaches which may be adopted, in order to assist them in their efforts towards investments in low-carbon and climate-resilient infrastructure, thereby maximizing investments in urban areas and trying to address their related poverty issues. This paper addresses a gap in the international literature on the problems many cities in developing countries face, in trying to adapt to a changing climate.