Low-density Residential Areas Research Articles

Even Geography of Upzoning: How Historic Urban Layouts, Land Use and Tenure Systems Influence Densification of Established Suburbs

ABSTRACT Historic urban layouts influence subsequent development, but this is rarely acknowledged by planning strategies. This paper analyses the urban transformation of three residential blocks in Brisbane, Australia from initial delineation to 2023. Findings outline three key messages for policymakers seeking to redevelop low density residential areas to higher density. First, upzoning results in little residential densification in small, inner-city lots. Second, owners maximise individual gains through home modifications that make existing houses larger, potentially decreasing affordability. Finally, only large, house lots experience conversion to apartment buildings. Findings highlight the place-based nuance of city-wide densification strategies, and the importance of urban morphology.

Understanding land take by low-density residential areas: An institutionalist perspective on local planning authorities, developers and households

Using a case study design, the study focuses on identifying the institutional configuration that determines land take by low-density residential areas. Methodologically, it combines geospatial approaches and new institutionalism to capture and understand residential development, taking into account the interests, constraints and agency of local planning authorities, developers and households. The geospatial analysis shows that land take in the case study regions is primarily the result of low-density residential areas. We find that the combination of rural housing ideals, municipal policy objectives, municipalities' disengagement from spatial development and private sector interests are the main drivers for this kind of residential development. As the interests and constraints apply to all case study regions, the identified institutional configuration has high power in explaining low-density residential development. Our study thus uncovers a close link between the interests and constraints of actors, which on the one hand explains the limited impact of existing and new planning instruments on reducing land take, and on the other hand fosters path dependency in the development of low-density residential areas. Although there is some potential for change, breaking path dependency requires significant behavioural change among local planning authorities, developers and households.

Investigating the Impact of Various Vegetation Scenarios on Outdoor Thermal Comfort in Low-Density Residential Areas of Hot Arid Regions

In hot, arid regions, outdoor spaces suffer from intense heat. This study explores how vegetation can improve outdoor thermal performance for pedestrians in low-density residential areas. Specifically, it seeks to identify the best combination of grass and trees for optimal comfort. Four scenarios were simulated using ENVI-met software, varying the proportions of grass and three tree types: 50% grass, 50% grass with 25% trees, 50% grass with 50% trees, and 50% grass with 75% trees. A reference scenario with no vegetation was also investigated. The simulated outputs encompassed air temperature (Ta), mean radiant temperature (Tmrt), relative humidity (RH), and physiologically equivalent temperature (PET). The findings show that scenarios with a higher percentage of trees exhibited the best reduction in air temperature, ranging from 0.2 k to 0.92 k. Additionally, the inclusion of trees and grass in the scenarios resulted in a substantial improvement in thermal performance, with an average reduction of 7.5 degrees in PET. Among the evaluated scenarios, the one comprising 75% trees and 50% grass exhibits the most noteworthy enhancement. This study underscores the significance of strategically positioning vegetation to coincide with prevailing wind patterns, thereby enhancing convective cooling mechanisms and improving overall thermal comfort levels. These insights offer valuable implications for urban planning and the development of sustainable design strategies.

Simulating the land use change effects on non-point source pollution in the Duliujian River Basin.

The uncertainty in the generation and formation of non-point source pollution makes it challenging to monitor and control this type of pollution. The SWAT model is frequently used to simulate non-point source pollution in watersheds and is mainly applied to natural watersheds that are less affected by human activities. This study focuses on the Duliujian River Basin (Xiqing section), which is characterized by a dense population and rapid urbanization. Based on the calibrated SWAT model, this study analyzed the effects of land use change on non-point source pollution both temporally and spatially. It was found that nitrogen and phosphorus non-point source pollution load losses were closely related to land use type, with agricultural land and high-density urban land (including rural settlements) being the main contributors to riverine nitrogen and phosphorus pollution. This indicates the necessity of analyzing the impact of land use changes on non-point source pollution loads by identifying critical source areas and altering the land use types that contribute heavily to pollution in these areas. The simulation results of land use type changes in these critical source areas showed that the reduction effect on non-point source pollution load is in the order of forest land > grassland > low-density residential area. To effectively curb surface source pollution in the study area, strategies such as modifying urban land use types, increasing vegetation cover and ground infiltration rate, and strictly controlling the discharge of domestic waste and sewage from urban areas can be implemented.

Measuring sediment loads and particle size distribution in road runoff: Implications for sediment removal by stormwater control measures

Road runoff contributes an array of pollutants which degrade the quality of receiving waters. Sediment conveyed in runoff results in loss of habitat and loss of reservoir capacity, among other undesirable impacts. To select and design stormwater control measures (SCMs), the sediment particle size distribution (PSD) is needed to quantify the required hydraulic retention time for particle settling and to understand what other treatment processes (e.g., filtration) are needed to meet sediment removal targets. A two-year field monitoring study was undertaken across the state of Ohio, USA, to evaluate the PSD of sediment in runoff at twelve roads. The highest TSS concentrations were observed on interstate highways (highest annual average daily traffic [AADT]) and minor arterials (low AADT), suggesting factors beyond AADT, such as antecedent dry period, rainfall intensity, and windborne dust and particulates, contribute to the varied sediment characteristics in runoff. The median TSS load across all samples collected was 2.7 kg/ha per storm event, while annual TSS loads for the monitoring sites varied from 98 kg/(ha·yr) to 519 kg/(ha·yr), with a mean value of 271 kg/(ha·yr). Particle size distributions varied across the monitoring sites, with mean and median d50 of 48.6 μm and 52.5 μm, respectively. Interstate highways (highest AADT) had significantly finer PSDs than other functional classes, while roads in low density residential areas had coarser PSDs than other land uses. Observed differences in PSD across road characteristics may guide SCM selection; dry detention basins and wet ponds/wetlands were predicted to provide effective removal across a variety of PSDs, while TSS reductions provided by hydrodynamic separators and high-flow media filters (which effectively remove larger particles) may be maximized in areas with coarser PSDs (e.g., roads surrounded by low density residential areas studied herein).

Modelling of land use and land cover changes and prediction using CA-Markov and Random Forest

We used the Cellular Automata Markov (CA-Markov) integrated technique to study land use and land cover (LULC) changes in the Cholistan and Thal deserts in Punjab, Pakistan. We plotted the distribution of the LULC throughout the desert terrain for the years 1990, 2006 and 2022. The Random Forest methodology was utilized to classify the data obtained from Landsat 5 (TM), Landsat 7 (ETM+) and Landsat 8 (OLI/TIRS), as well as ancillary data. The LULC maps generated using this method have an overall accuracy of more than 87%. CA-Markov was utilized to forecast changes in land usage in 2022, and changes were projected for 2038 by extending the patterns seen in 2022. A CA-Markov-Chain was developed for simulating long-term landscape changes at 16-year time steps from 2022 to 2038. Analysis of urban sprawl was carried out by using the Random Forest (RF). Through the CA-Markov Chain analysis, we can expect that high density and low-density residential areas will grow from 8.12 to 12.26 km2 and from 18.10 to 28.45 km2 in 2022 and 2038, as inferred from the changes occurred from 1990 to 2022. The LULC projected for 2038 showed that there would be increased urbanization of the terrain, with probable development in the croplands westward and northward, as well as growth in residential centers. The findings can potentially assist management operations geared towards the conservation of wildlife and the eco-system in the region. This study can also be a reference for other studies that try to project changes in arid are as undergoing land-use changes comparable to those in this study.

Correlation between caffeine and coprostanol in contrasting Amazonian water bodies

The evaluation of contamination by domestic sewage is relevant in the Amazon region; however, it has neither been well-developed nor accompanied by research or monitoring programs. In this study, caffeine and coprostanol as indicators of sewage were investigated in water samples from Amazonian water bodies that crisscross the city of Manaus (Amazonas state, Brazil) and cover regions with distinct main land uses such as high-density residential, low-density residential, commercial, industrial, and environmental protection areas. Thirty-one water samples were studied based on their dissolved and particulate organic matter (DOM and POM) fractions. Quantitative determination of both caffeine and coprostanol was carried out using LC-MS/MS with APCI in the positive ionization mode. The streams of the urban area of Manaus had the highest concentrations of caffeine (1.47–69.65 μg L−1) and coprostanol (2.88–46.92 μg L−1). Samples from the peri-urban Tarumã-Açu stream and from the streams in the Adolpho Ducke Forest Reserve showed much lower concentrations of caffeine (20.20–165.78 ng L−1) and coprostanol (31.49–120.44 ng L−1). Samples from the Negro River showed a wider range of concentrations of caffeine (20.59–873.59 ng L−1) and coprostanol (31.72–706.46 ng L−1), with the highest values found in the outfalls of the urban streams. Levels of caffeine and coprostanol were significantly positively correlated in the different organic matter fractions. The coprostanol/(coprostanol + cholestanol) ratio proved to be a more suitable parameter than the coprostanol/cholesterol one in low-density residential areas. Proximity to densely populated areas and the flow of water bodies appear to influence the caffeine and coprostanol concentrations, which was observed in their clustering in the multivariate analysis. The results indicate that caffeine and coprostanol can be detected even in water bodies that receive very low domestic sewage input. Therefore, this study revealed that both caffeine in DOM and coprostanol in POM represent viable alternatives for use in studies and monitoring programs even in remote areas of the Amazon, where microbiological analyses are often unfeasible.

Spatial Patterns of Anthropogenic Heat and Urban Density of an Indian Metropolitan City

Anthropogenic heat intensity arises from levels of population, buildings and vehicle densities. Population and built-up densities are very high in the cities of developing countries, which may have an impact on heat generated from metabolism and buildings differently compared to developed countries. Hence, this study investigated the magnitude of anthropogenic heat in different land uses and areas with different built-up densities pertaining to Indian metropolises; Bengaluru metropolitan area was selected for this study. The maximum metabolic heat (22.8 W/m2), vehicular heat (87.2 W/m2) and building heat (443.0 W/m2) were found in the high-density residential grids and the mixed-use grids in the city centre area during 2017. The lowest value (0.1 W/m2) was found in the low-density residential areas, public and semi-public areas, restricted areas and agricultural areas. A high positive correlation value (0.8 in 2011 and 0.72 in 2017) was found between non-residential building surface fractions and anthropogenic heat.

U.S. Farmland under Threat of Urbanization: Future Development Scenarios to 2040

Urbanization imperils agriculture by converting farmland into uncultivable impervious surfaces and other uses that limit land productivity. Despite the considerable loss of productive croplands due to historic urbanization in the United States, little is known about the locations and magnitudes of extant agricultural land still under threat of future urban expansion. In this study, we developed a spatially explicit machine learning-based method to predict urban development through 2040 under a business-as-usual scenario and explored its occurrence on existing farmland. We found that if urban development continues at the same pace as that between 2001 and 2016, by 2040, highly developed areas and low-density residential areas will increase by 9.5 and 21 million acres, respectively. This increase would result in 18 million acres of agricultural land lost, fragmented, or compromised (~2% of total agricultural lands in 2016), with the remainder of projected development occurring on other types of natural and semi-natural lands. Of the affected agricultural lands, 6.2 million acres (34%) would be converted to uncultivable urban uses and 12 million acres (66%) to low-density residential uses. Agricultural land losses are projected to be greatest in fast-growing regions such as Texas, California, and the Southeast, and on the outskirts of metropolitan areas across the country, especially in the Midwest, where agricultural lands are more concentrated. The losses as a percentage of existing agricultural lands are projected to be highest along the East Coast, where many urban areas are forecasted to expand onto a limited remaining pool of cultivable lands. These findings can help guide the efforts of local, state, and federal policymakers to reduce land use competition between urban and agricultural systems and mitigate the impacts of projected urban expansion.

Correlation between Socio-Economic Characteristics and Housing Quality of Residential Neighbourhoods in Akure, Southwest Nigeria

There is a general paucity of explanations for the emerging social and spatial changes in the pattern and socio-economic traits of urban residential housing units in Nigeria. Hence, this study examined the spatial pattern of residential neighbourhoods; assessed the quality of residential housing units; and evaluated the correlation between the socio-economic position of respondents and housing quality in Akure, Nigeria. Data were derived from the household questionnaire, remotely sensed data (Landsat 8 OLI/TIR, 2021), a Google Earth map, a Street Map of Akure Township, and personal observations. The study adopted a step-wise sampling technique to select 383 samples from 139,069 heads of households in Akure in 2021. Data were analysed using percentage distribution, Pearson Correlation Coefficient, and t-test. Results indicated varying housing qualities across three residential zones in Akure, Nigeria; houses in the low-density residential areas were of better quality than the other residential zones. The quality of houses occupied was influenced by the type of occupation, level of education and average annual income of residents. The study concluded that inadequate housing facilities are fundamental to the observed deteriorating housing qualities in the study area. Therefore, the study suggested improvement of the existing infrastructures and the provision of new ones in the study area. The main contribution of this study is to proffer solutions for a sustainable housing delivery system to facilitate a better quality of life in Nigerian urban centres.

EVALUATION OF PARTICULATE MATTER (PM2.5 AND PM10) CONCENTRATIONS IN THE DRY AND WET SEASONS AS INDICES OF AIR QUALITY IN ENUGU URBAN, ENUGU STATE, NIGERIA

The particulate matter (PM) is one of the major air pollutants emitted from various sources, having adverse effect on human health and environment. The study evaluates the concentrations of PM2.5 and PM10 pollution in Enugu Urban. The PM2.5 and PM10 concentrations were collected from April 2018 to March 2019 using CASELLA CEL - 712 (Dust Detective). The study area was categorized under, industrial, commercial, high density residential, low density residential areas and control location in a rural area. The annual average concentration were in the ranges 23.06 ± 1.53 to 153.23 ± 28.73 µg/m3 for PM2.5 while the average concentration for PM10 ranged from 37.49 ± 3.75 to 336.49 ± 47.05 µg/m3. The average annual PM2.5 and PM10 concentrations in almost all the areas studied are above the WHO limits of PM2.5-25 µg/m3 and PM10 - 50µ/m3. Therefore, the residents of study areas are exposed to inhalable particulate which may have adverse health risk and environmental deterioration. This enrichment may be attributed mostly to human activities. Adequate attention should be given; periodic monitoring and pollution abatement measures must be strictly adhered to.

Rock Refuges Are Strongly Associated with Increased Urban Occupancy in the Western Fence Lizard, Sceloporus occidentalis

Urbanization has dramatically altered habitats for local species worldwide. While some species are unable to meet the challenges that these alterations bring, others are able to persist as long as a threshold for suitable habitat is met. For reptiles, a key feature for persistence in urban areas can be access to suitable refuges from predation, high temperatures, and/or other environmental challenges. We tested for effects of local and landscape variables affecting urban occupancy in the Western Fence Lizard, Sceloporus occidentalis, in transects across an urban–rural gradient, with a specific focus on the presence of rock, tree, and shrub refuges. We found that fence lizards were much more likely to be present in areas with more rock cover, and in parks or low-density residential areas. Occupancy was also positively related to canopy cover in the general vicinity, though negatively related to number of trees along the transects. Our results highlight the importance of assessing local habitat features to successfully predict the occupancy of reptile species in urban habitats, and present directions for future research with concrete conservation and management applications.

Bystander interventions in out-of-hospital cardiac arrest according to geographical area type

Abstract Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): TrygFonden Introduction Bystander interventions and survival after out-of-hospital cardiac arrest (OHCA) have increased remarkably in Denmark over the last years. Even though 75% of all OHCA occur in residential areas, most interventions to increase bystander interventions have focused on public places. This study assessed bystander interventions (cardiopulmonary resuscitation [CPR] and defibrillation) according to area type. Methods We included bystander witnessed OHCAs from the Danish Cardiac Arrest Registry (2016-2019) with a known geographical location. Urban Atlas is an international data base covering 40% of Denmark, which uses satellite images to divide areas into different area types. In this study, Urban Atlas was used to identify and geocode OHCAs within the following subgroups: high density residential areas (defined as average degree of soil sealing >50%), low density residential areas (average degree of soil sealing <50%), public and industrial sites, nature, sport and leisure facilities, transportation (e.g. airport and railway stations), and fast transit roads. Results A total of 5,180 bystander witnessed OHCA were covered by Urban Atlas and included. The proportion of bystander interventions was lowest in residential areas where most OHCAs occurred (Figure 1). The proportion of bystander interventions was highest in sport and leisure areas and transportation sites. The proportion of bystander defibrillation increased 5-fold in transportation sites and 3-fold in sports and leisure sites compared with residential areas. Conclusion Patients with OHCA in transportation areas and sports and leisure areas were substantially more likely to receive bystander CPR and defibrillation, highlighting the success of initiatives to increase bystander interventions in public areas. Bystander defibrillation was lowest in residential areas supporting further efforts, such as smartphone activated volunteer responder activation, to improve bystander defibrillation in residential areas.

Study of the manifestations of visual pollution in some neighborhoods of Jeddah city: Comparative study: دراسة مظاهر التلوث البصري في بعض أحياء مدينة جدة: دراسة مقارنة

This research aims to identify visual pollution, its most important manifestations and types, the reasons that led to its emergence, and its impact on the psychological and physical health of humans. The descriptive and analytical approach is applied in the study of manifestations of visual pollution in some neighborhoods of Jeddah, comparing them and identifying the most polluted among them. The neighborhoods were selected according to the local schematic of Jeddah city- regulations and controls 1440H in the zoning of residential areas-. The study was in line with 2030's vision of improving the urban landscape in Saudi cities, one of its objectives to address visual distortions in Saudi cities. This research has found that the neighborhoods have different manifestations of visual pollution. Al-Hendaweyyah neighborhood is a slum area, were all manifestations of the urban style visual pollution appeared. In addition, graffiti on the walls clearly appeared. On the other hand, AL-Mohammadya is low-density residential area. It is a planned neighborhood, where the manifestations of visual pollution did not appear in compare with other one, with limited exception of graffiti. Finally, the study recommends developing a strategy to improve the visual landscape in slums by renovation of old buildings, Also, by developing terms and conditions for building exterior colors and packaging materials that suit the urban style of the area.

Settlement land directions based on the tsunami disaster in the coastal of Purworejo District, Central Java

The purpose of this study was to determine the direction of land use for settlements. The research location is on the coast of Purworejo Regency which includes Purwodadi District, Ngombol District, and Grabag District. This study uses a quantitative descriptive method. Data collection techniques include observation, interviews, and secondary data processing from related agencies. The analytical technique used in the Geographic Information System (GIS) analysis is to overlay tsunami hazard data, evaluate the suitability of residential land and area functions. The results of the overlay will show the zoning for the direction of the settlement. The results showed that the coast of Purworejo Regency has three directions of land use for settlements. The optimal direction of land use for settlements has an area of 427.6 Ha with the development of settlements with high density and can be developed as a Central Business District (CBD) area. The conditional direction of land use for settlements has an area of 3794.05 Ha. The law on the development of low-density residential areas and residential areas with structural and non-structural mitigation because this zone has a moderate level of tsunami vulnerability. The directive not to make settlements with an area of 1242.78 hectares is directed to the green belt area with limited community activities.

Source identification and health risk assessments of heavy metals in indoor dusts of Ilorin, North central Nigeria.

Exposure to heavy metals (HMs) in indoor dusts is a serious public concern that is linked to a myriad of deleterious health outcomes. The objectives of this study are to estimate the contamination levels of HMs in indoor dusts of different residential areas in Ilorin, Nigeria; identify HMs sources in different residential areas; and evaluate human health risks of HMs in selected residential areas. Indoor dust sampling was conducted in ten randomly selected from low, medium and high population density residential areas of Ilorin, Nigeria. Ten HMs concentration levels, their health risk implication and the associated potential ecological risks were evaluated. The mean concentration levels measured for Fe, Pb, Zn, As, Co, Cr, Cu, Cd, Mn and Ni were 38.99, 5.74, 3.99, 0.08, 2.82, 2.13, 0.47, 0.60, 6.45 and 1.09mg/kg, respectively. Positive Matrix Factorization (PMF) model was applied to ascertain sources of HMs in sampled indoor dust. Percentage contribution from oil-based cooking (29.82%) and transportation (29.77%) represented the highest source to HM concentrations among the six factors identified. The results of the various pollution indices employed showed that Pb, Zn, As, Co, Cr, Cu, Mn and Ni contributed moderately to HMs concentration levels in the sampled dusts. Cd had highest potential ecological risk factor of between 160 and 320. The average values of Enrichment Factors (EFs) obtained aside from Fe used as the reference metal, ranged between 8.46 (As) and 2521.61(Cd). Health risk assessment results revealed that children are the most susceptible to the risks associated with HMs bound indoor dust than the adults. The percentage risk contributions of Hazard Quotient via ingestion route (HQing) in Hazard Index (HI) for non-cancer risk of indoor HMs were 93.17% and 69.87% in children and adults, respectively. Likewise, the percentage cancer risks contribution through ingestion pathway (CRing) were higher than cancer risks through inhalation and dermal pathways (CRinh and CRdermal), accounting for 99.84% and 97.04% of lifetime cancer risk in children and adults, respectively. The contamination level of Cd recorded is of great concern and signifies very strong contribution from anthropogenic sources. This study has further revealed the levels of HMs in typical African residential settings that could be used by relevant stakeholders and policy makers in developing lasting control measures. The online version contains supplementary material available at 10.1007/s40201-021-00778-8.

Abstract 12132: Diurnal Variation in Citizen Responder and Automated External Defibrillation Coverage of Out-of-Hospital Cardiac Arrest in Denmark According to Area Types

Introduction: Following the implementation of the Danish AED network and a nationwide citizen responder (CR) program for out-of-hospital cardiac arrest (OHCA), CR and AED coverage for OHCAs according to area types has not been investigated. We aimed to assess AED and CR coverage of historical OHCAs according to area types in daytime (12pm) and nighttime (12am). Methods: We included non-EMS witnessed OHCAs from the Danish Cardiac Arrest Registry (2016-2019) and AEDs registered with the Danish AED network (November 2020) available at 12am (n=22,418) and 12pm (n=14,734). Exact locations of CRs who were registered with the national CR program by December 2020 were identified on a normal working day (Wednesday, December 2, 2020) at 12am and 12pm (representing day- and nighttime location). OHCAs, AEDs, and CRs were identified and geocoded using a geographical information system. Urban Atlas was used to categorize areas into subgroups using satellite images; high density residential areas, low density residential areas, public and industrial sites, nature, sport and leisure facilities, transportation (e.g. airport and railway stations), and fast transit roads. Results: A total of 10,126 OHCAs (63.0% male, median age 73 years). We mapped 14,119 AEDs (12 pm) and 24,372 CR (12 pm) in Urban Atlas. Most OHCAs in all area types were covered by >= 1 AED. A greater variation was observed in CR coverage when compared to AED coverage, according to area type. Little difference in coverage of both AED and CR according to time of day was observed. (Figure 1) Conclusion: The highest CR and AED coverage were observed in high density residential areas, transportation sites, public and industrial areas, and sport and leisure facilities, which is where most OHCAs occurred. These findings indicate a high coverage of citizen responders and AEDs in Denmark.

Spatial Extent and Distribution of Ambient Airborne Particulate Matter (PM2.5) in Selected Land Use Sites in Nairobi, Kenya.

Air pollution is one of the most important environmental and public health concerns worldwide. Urban air pollution has been increasing since the industrial revolution due to rapid industrialization, mushrooming of cities, and greater dependence on fossil fuels in urban centers. Particulate matter (PM) is considered to be one of the main aerosol pollutants that causes a significant adverse impact on human health. Low-cost air quality sensors have attracted attention recently to curb the lack of air quality data which is essential in assessing the health impacts of air pollutants and evaluating land use policies. This is mainly due to their lower cost in comparison to the conventional methods. The aim of this study was to assess the spatial extent and distribution of ambient airborne particulate matter with an aerodynamic diameter less than 2.5 μm (PM2.5) in Nairobi City County. Seven sites were selected for monitoring based on the land use type: high- and low-density residential, industrial, agricultural, commercial, road transport, and forest reserve areas. Calibrated low-cost sensors and cyclone samplers were used to monitor PM2.5 concentration levels and gravimetric measurements for elemental composition of PM2.5, respectively. The sensor percentage accuracy for calibration ranged from 81.47% to 98.60%. The highest 24-hour average concentration of PM2.5 was observed in Viwandani, an industrial area (111.87 μg/m³), and the lowest concentration at Karura (21.25 μg/m³), a forested area. The results showed a daily variation in PM2.5 concentration levels with the peaks occurring in the morning and the evening due to variation in anthropogenic activities and the depth of the atmospheric boundary layer. Therefore, the study suggests that residents in different selected land use sites are exposed to varying levels of PM2.5 pollution on a regular basis, hence increasing the potential of causing long-term health effects.

Source identification and health risk assessments of polycyclic aromatic hydrocarbons in settled dusts from different population density areas of Ilorin, Nigeria.

Polycyclic aromatic hydrocarbons (PAHs) have attracted significant attention in recent times on account of their reasonably high environmental burden and extreme toxicity. Samples of indoor dusts were obtained daily over a period of 2weeks from 10 residences located within low, medium, and high density residential areas of Ilorin City. The concentration levels, potential sources, and cancer health risks of sixteen polycyclic aromatic hydrocarbons (PAHs) were investigated using gas chromatography/mass spectrometry. PAHs total concentrations varied from 3.95 ± 0.19 to 8.70 ± 0.43μg/g with arithmetic mean of 6.09 ± 0.46μg/g. Fluoranthene was the most dominant PAHs congener. High molecular weight (HMW) PAHs (4-6 rings) were the most prevalent PAHs and were responsible for 79.29% of total PAHs in sampled residences. Chrysene (Chry) was the most abundant compound among the 7 carcinogenic PAHs (CPAHs). Moreover, diagnostic ratios and positive matrix factorization (PMF) employed to apportion PAHs suggested that indoor dusts originated from indoor activities and infiltrating outdoor air pollutants. Diagnostic ratios revealed that PAHs are from mixed sources which include coal/wood combustion, non-traffic and traffic emissions, petroleum, petrogenic (gasoline), and petroleum combustion. Similarly, positive matrix factorization (PMF) model suggested five sources (factors) were responsible for PAHs in indoor dusts comprised of petroleum combustion and traffic emissions (60.05%), wood and biomass combustion emissions (20.84%), smoke from cooking, incense burning and tobacco (4.17%), gasoline combustion from non-traffic sources (13.89%), and emissions from coal burning and electronic devices (1.05%). The incremental lifetime carcinogenic risks (ILCR) of PAHs in adults and children estimated by applying benzo(a)pyrene (BaP) equivalent were within the satisfactory risk limits in Ilorin. Indoor PAHs emissions in Ilorin residences could be monitored and controlled by using data provided in this study.

Local variations in the response of birds to human presence in urban areas

Studies that seek to understand the local variations in the response of birds to human disturbance in urban areas are important for conservation. This article investigated the contribution of human population density in the different urban land use zones of Harare (high, medium and low-density residential areas, as well as industrial areas), among other variables, to the models explaining the flight initiation distance (FID) of twenty-five urban bird species. The specific objectives of the study were: to test whether the variables significantly predict FID; to investigate their relative contribution to the ‘best-performing’ models; and to determine the relationship between FID and the individual predictor variables. Generalised linear models were used to predict FID as a function of: flock size, intruder starting distance, urban land use zone, perch height, average bird mass and species. We predicted that FID would increase in tandem with flock size and average bird mass, and decrease inversely proportional to population density, intruder starting distance and perch height. We also expected FID to differ by species. Results illustrated that twelve models best explained the FID of birds in the study area. Urban land use zone, intruder starting distance and species were the only predictors that appeared in all the twelve models. However, flock size and average bird mass appeared in only six of the twelve models making them the least important predictor variables. These findings add to current knowledge on local variation in the FID of certain bird species within the different land use zones. The results could be used to create buffers aimed to minimise human-induced disturbance on bird species.