Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Urbanization”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 541 records · Page 30Linked to original sources
PubMed1986

Urban concentration and rural growth: a two-sector analysis.

"This paper examines the mechanism and extent of urban concentration using a two-sector growth model. The cause of urbanization is sought in the existence of urban scale economies. Assuming that temporary production decisions are concerned with optimal labor inputs and that profit incomes are reinvested according to relative profitability, the model shows persistent tendency for urban concentration and the transition of the economy from unlimited to limited labor supply. A simple example suggests that urban concentration is more likely than rural expansion with urban contraction."

Demography↗
PubMed1989

A study of standards for the differentiation of the urban population in China.

In China, the recent reclassification of the country into urban areas has led to an increase of urban population that is to a large extent purely administrative. To set a standard for differentiating the population into urban and rural, it is necessary to formulate a scientific standard. The author considers the problems and contradictions created by the differentiation of population according to cities and towns which are administratively established. Newly established cities and towns are comparatively large in number and their sizes are much expanded because a certain amount of agricultural population is included in the urban population. A survey of 347 cities revealed that on the average, the agricultural population accounted for 47% of the total. It is important to set the principles for standards of differentiation of the urban population with a view to the origin of the city. All the economic, social, and administrative principles have limitations, and no one set of principles can be used by itself to decide whether or not an area is urban. The standards should be based on actual conditions within China itself.

Asia↗
PubMedDate not supplied

The pattern of urbanization in Western Europe.

This report "presents major trends and changes in the urban system in Europe over the last thirty years (1960-1990). It examines the present state of urbanization and considers the cycles and dynamics of urban development, urban growth and urban decline and describes current and future issues of urban development in the twelve countries of the European Community, including the united Germany, and in Austria and Switzerland."

Demography↗
PubMed1988

Urbanization and spatial development in the Asian and Pacific region: trends and issues.

"This article reviews the trends and patterns of urbanization and spatial development since 1960 in selected Asian and Pacific developing countries and discusses the main forces underlying the trends. It examines issues such as the speed of urbanization, spatial concentration and appropriate measures to deal with them; the effects of income and differences in sectoral productivity and of population growth; the relative effectiveness of spatial policies; and urban problems and measures to cope with them. It then attempts to preview the likely urbanization trends to the year 2000, highlighting problems associated with rapid urban growth and excessive spatial concentration. Finally, it discusses the various policy approaches to spatial and urban issues."

Asia↗
PubMed2003

Soil phosphorus concentrations in Dane County, Wisconsin, USA: an evaluation of the urban-rural gradient paradigm.

Understanding the magnitude and location of soil phosphorus (P) accumulation in watersheds is a critical step toward managing runoff of this pollutant to aquatic ecosystems. Here, I examine the usefulness of urban-rural gradients, an emerging experimental design in urban ecology, for predicting extractable soil P concentrations across a rapidly urbanizing agricultural watershed in southern Wisconsin. I compare several measures of an urban-rural gradient to predictors of soil P such as soil type, slope, topography, land use, land cover, and fertilizer and manure use. Most of the factors that were expected to drive differences in soil P concentrations were found to be poor predictors of Bray-1 (extractable) soil P, which ranged from 4 to 660 ppm; while there were several significant relationships, most explained only a small proportion of the variation. A multiple linear regression model captured approximately 37% of the variation in the data using the urban-rural gradient, topography, land use, land cover, manure use, and soil type as predictors. There was a significant relationship between Bray-1 P concentration and each of the urban-rural gradients, but these relationships explained only between 2.6% and 3.3% of the variation in P concentrations. Extractable P concentration in soils, unlike some other ecosystem properties, is not well predicted by urban-rural gradients.

Agriculture↗
PubMed2006

Heavy metal contamination and distribution in the urban environment of Guangzhou, SE China.

Ever-increasing heavy metal accumulation in the urban environment of Guangzhou, the largest light industrial production base and one of the most rapidly developing cities in China, poses a serious threat to environment as well as to human health in the region. As a sink or source, urban deposits are good indicators of the level and extent of heavy metal accumulation in the surface environment. The aim of this preliminary study was to examine the distribution of heavy metal contamination in the urban environment of Guangzhou. It was based on a systematic sampling of road dusts and corresponding gully sediments along major roads running mainly through commercial and residential to industrial districts of the city. In addition to road dusts and gully sediments, ceiling dusts from the Pearl River Tunnel were also collected to characterize anthropogenic emissions dominated by traffic-related activities. In general, the level of Cd, Cu, Pb and Zn contaminations were more severe on the industrialized side of Guangzhou than on the western side where heavy traffic and industrial activities were limited. The primary determinants of the level of heavy metal contamination and the distribution of this contamination in the urban environment of Guangzhou were the site-specific conditions of its urban setting, particularly the types of industries, the nature of the traffic flow, sample residence times and variations in grain size of the particulate contaminants. This study highlights the complexity of the urban system and indicates that in just such a system individual urban components should be interlinked to assess the long-term environmental and health effects of heavy metal contamination. Among the heavy metals tested--Cd, Cu, Pb and Zn--the level of Zn contamination was the most severe and widespread, and thus requires immediate attention.

China↗
PubMed2006

Metal contamination in urban soils of coastal Tuscany (Italy).

Urban soils are often contaminated by metals deriving from human activities. Urban polluted soils can affect human health through direct physical contact or through the food chain. The behaviour of metals is affected by chemical and physical soil properties. Heavy metal concentration was determined in some soils of three medium sized towns of coastal Tuscany, Central Italy. Soil samples were collected in roadsides, urban agricultural soils (allotments), playgrounds and public parks. The analysis included total metal content (Pb, Cu, Zn, Ni, Cd), and sequential extraction. Lead reached the highest levels in the soils and was higher near roads. In urban agricultural soils and in allotments Cu was present in noticeable quantities (300 mg kg(-1)). The presence of Cu in urban soils seems to be typical of soils used for a long period as agricultural land, especially vineyards in the area covered by this study. Sequential extraction was performed to evaluate the mobility of the metals and to better understand the impact of the anthropogenic activity on urban sites. In the present study principal components analysis (PCA) is employed to describe the characteristics of urban soils.

Agriculture↗
PubMed2004

Concentration characteristics of atmospheric PCBs for urban and rural area, Korea.

Mean concentrations of total PCBs (gas+particle) detected in urban and rural atmospheres were 130.41+/-62.57 pg/m(3) and 39.65+/-34.04 pg/m(3), respectively. The concentration distribution of PCB homologs in the urban and rural area decreased with increasing Cl substitutions and showed significant correlation coefficients (P>0.05) with the octanol-air partition coefficient (K(OA)) and vapor pressure, respectively. The fractions (%) of total PCBs were 28% for tri-CBs, 25% for tetra-CBs and 24% for penta-CBs in urban air and 45% for tri-CBs, 24% for tetra-CBs, and 21% for penta-CBs in rural air. The sum of those homologs was 77% for urban and 90% for rural air. Therefore, these homologs were identified as the main components of PCB homologs compared to other homologs (>penta-CBs). The Clausius-Clapeyron (CC) plot was applied to atmospheric PCB data, relating PCB partial vapor pressure (logarithm P) to inverse absolute temperature (1/T). The slopes obtained from Clausius-Clapeyron plots were -3888 (R(2)=0.75, P<0.0001) for urban and -1902 (R(2)=0.22, P<0.1) for rural air. The slope for urban air was approximately two times higher than that of rural air, possibly because the atmospheric concentration of lower molecular weight congeners in urban air may be predominantly influenced by local sources relative to rural air.

Journal Article↗
PubMed2005

Comparative field study on precipitation, throughfall, stemflow, fog water, and atmospheric aerosol and gases at urban and rural sites in Japan.

Precipitation collected by a wet-only sampler (WP), precipitation collected by a filtering-type bulk sampler (BP), throughfall (TF), stemflow (SF), fog water (FW), and atmospheric aerosol and gases were collected at two sites with different site classifications: an urban site (Mt. Rokko) and a rural site (Mt. Awaga) to investigate canopy-atmosphere interactions and to study the chemistry of precipitation in forested areas located in different atmospheric conditions. Compared to those at the rural site, the monthly volume-weighted pH values at the urban site were not significantly (p>0.05) different for WP, higher (p<0.05) for BP, not significantly (p> 0.05) different for TF, lower (p<0.01) for SF, and lower (p<0.01) for FW. The order of mean pH values at the urban site was FW<SF<WP<TF<BP. In contrast, the order at the rural site was FW<SF<BP<WP<TF. Concentrations of chemical species at the urban site were higher than those at the rural site in all samples and all chemical species. In particular, higher NO(3)(-) concentrations at the urban site were observed in all samples. The amount of dry deposition on leaves at the urban site was approximately 1.17 times larger than that at the rural site. The monthly net TF (=TF-BP) in autumn seemed to be larger than that in summer; this trend was remarkable in K(+). The monthly NO(3)(-) deposition in the net TF was larger at the urban site than at other parameters and at the rural site. The concentrations of chemical species in aerosol and gases that were measured near the central part of Kobe City were ca. 3.4 times higher than those in the rural area. Mt. Rokko borders the central part of the city, which caused the concentrations at Mt. Rokko to be higher than those at Mt. Awaga. The deposition amounts at Mt. Rokko were larger than those at Mt. Awaga, which probably can be attributed to the higher concentrations of chemical species in atmospheric aerosol and gases.

Aerosols↗
PubMed2000

Temporal and spatial variation in C, N, S and trace element contents in the leaves of Quercus ilex within the urban area of Naples.

This paper presents a comparative analysis of the concentrations of C, N and S and several trace elements (Fe, Mn, Na, Zn, Cu, V, Pb, Ni, Cr, Cd) in leaves of Quercus ilex, an evergreen oak, collected in the urban area of Naples in 1989 and 1996. The samplings were carried out from 25 urban sites (roads with different traffic flows as well as urban and suburban parks) and from two remote areas as controls. Relative to 1989, the values measured in 1996 denote a strong decrement of S, Fe, Na, Pb, and Cr, with the exception of S in control sites. By contrast, C, N and Cd contents were higher in 1996 than in 1989. Cu and Ni showed a conspicuous increment in control sites as well as in urban sites facing the sea and in the parks, while in all the other urban sites these elements decreased remarkably. No significant difference was found in the leaf contents of Mn, Zn and V measured in 1989 relative to 1996. Both in 1989 and 1996 the contents of N, S, Fe, Na, Cu, Pb, V, Ni, Cr and Cd were significantly higher in leaves from urban sites than in the controls, reflecting the high degree of contamination of the urban area. Concentration factors expressed as the ratio of road/control values for most of the elements were still very high in leaves collected in 1996, though remarkably lower than in 1989.

Journal Article↗
PubMed2004

Genetic diversity and structure of urban populations of Pieris butterflies assessed using amplified fragment length polymorphism.

Conservation programs in urban ecosystems need to determine the genetic background in populations of urban dwellers. We examined the genetic diversity and structure of Pieris rapae and P. melete using AFLP markers, and compared them between species and between urban and rural environments. As a result: (i). in both species, there was no reduction in genetic diversity within urban populations by direct comparison of diversity measurements, although the analysis of molecular variance suggested significant reductions in the variance within seasonal subpopulations in urban populations; (ii). P. rapae retained greater genetic diversity within species and populations; (iii). populations of both species showed significant genetic differentiation, and P. melete was more strongly subdivided; (iv). in both species, geographically close populations did not cluster with one another in the upgma analysis; (v). there was no genetic isolation due to geographical distance in either species; (vi). the genetic composition of seasonal subpopulations differed in urban populations of both species, and the genetic distances among subpopulations were correlated with seasonal differences in P. rapae and with temporal differences in P. melete. These results indicate that the genetic diversity in urban populations of both species was reduced at times, but was maintained by dispersal from genetically differentiated populations. Differences in the ability and mode of dispersal in the two species may be reflected in the degree of population subdivision and patterns of seasonal change in the genetic composition.

Analysis of Variance↗
PubMedDate not supplied

Village distance from urban centre as the prime modernization variable in differences in blood pressure and body mass index of adults of the Purari delta of the Gulf Province, Papua New Guinea.

OBJECTIVE: The study examined the extent to which the geographical proximity of villages to an urban centre and other modernization variables are associated with variation in blood pressure and body mass index (BMI) of adults of the Purari delta of the Gulf Province, Papua New Guinea (PNG). METHODS: Mean BMI, systolic blood pressure (SBP) and diastolic blood pressure (DBP) of 292 adults surveyed in 1995-1997 in the Purari delta, PNG, are reported by village of residence, and related to modernization variables, including village of residence, urban life, urban connectedness, economic status and education. RESULTS: Mean BMI, SBP and DBP differ according to village of residence, there being a gradient in mean blood pressure from highest in the village closest to the urban centre, Baimuru, and lowest in the village most distant from it. The gradients in these variables across the three villages are not due to differences in age structures between the villages. Place of residence, which represents the distance from town, has the greatest impact on the BMI of males, while among the females, the number of relatives living in urban centres had a significant effect on BMI. For both males and females, place of residence has the strongest effect on SBP. While for the males, place of residence is the only significant factor associated with SBP, for the females, SBP is also associated with BMI, level of income and to a lesser extent with age. Very similar results were obtained for DBP. CONCLUSIONS: Distance to urban centre appears to have a strong effect, relative to other modernization variables, on BMI and blood pressure, this effect being far stronger for males than for females. In large part, this effect operates by way of differences in number of sources of income as well as number of close relatives of women who are resident in an urban centre. Reasons for the male-female differences observed may include gender differences in degree of mobility, and possibly greater physical sensitivity of males to the environment than females. Traditionally, there have been clear divisions of labour between males and females, the latter spending longer in subsistence activities than the former. It is speculated that males have more free time to travel to town should they wish, while women may travel to town to take produce to market, and be limited by how much time they spend in town when they are there, by the need to return to carry out household and subsistence tasks. It may also be that young adult males are more susceptible to modernization, in that they exhibit a greater degree of non-conformity than young women, and may be more favourably disposed to adopt aspects of western lifestyle.

Adult↗
PubMed1995

An observation-based model for analyzing ozone precursor relationships in the urban atmosphere.

An Observation-Based Model (OBM) is described, which uses in-situ atmospheric observations to determine the sensitivity of ozone concentrations in an urban atmosphere to changes in the emissions of ozone precursors (i.e., volatile organic compounds and nitrogen oxides). The model is formulated following the concept of Relative Incremental Reactivity (RIR) developed by Carter and Atkinson. In the OBM, however, observed concentrations rather than emission inventories are used to drive the photochemical simulations and thereby ensure that the calculations are carried out for the proper mix of nitrogen oxides and volatile organic compounds. From these calculations, a series of sensitivity factors, or RIRs, are inferred that can be used to (1) determine whether reducing emissions of nitrogen oxide or emissions of hydrocarbons would be most effective in abating ozone in a given urban area, and (2) identify the most critical subset of hydrocarbons present in an urban atmosphere causing ozone exceedances. Because the OBM is relatively easy and inexpensive to operate and makes use of data that are increasingly available, it can be used to analyze a wide array of ozone episodes and, thus, could prove to be a relatively cost-effective tool for the analysis of ozone precursor relationships in an urban atmosphere. On the other hand, because the OBM is diagnostic rather than prognostic, it cannot be used in a predictive mode to estimate exactly how much emission reduction is needed to reduce ozone concentrations. For this reason, the OBM should be viewed as a complement to, rather than a substitute for, more sophisticated gridded, emission-based models. To illustrate the characteristics of the OBM and to demonstrate its applicability, we first compare the results of the OBM to those obtained from a series of simulations of the Atlanta metropolitan area using the Urban Airshed Model (UAM), a three-dimensional Eulerian grid model. The OBM is then used to analyze a dataset obtained from the 1990 Atlanta Ozone Study, an EPA field sampling program conducted during the summer of 1990. Because of limitations and potential flaws in the 1990 Atlanta dataset, the results of this OBM analysis are largely illustrative rather than definitive. Nevertheless, a few important issues are elucidated by the analysis. These include (1) the importance of accounting for biogenic hydrocarbons produced from urban vegetation; (2) the potential flaw in using early-morning VOC-to-NOx ratios to infer whether ozone production is limited by VOC or NOx; (3) the critical need for high-sensitivity nitrogen oxide measurements to quantify the sub-ppbv concentrations of NO during the afternoon hours; and (4) the need to consider a number of individual ozone episodes in studying an urban atmosphere because of the possibility that the degree of VOC- and NOx-limitation may vary from one episode to another.

Atmosphere↗
PubMed2007

Relative effects of land use and near-stream chemistry on phosphorus in an urban stream.

Elevated levels of P in urban streams can pose significant water quality problems. Sources of P in urban streams, however, are difficult to identify. It is important to recognize both natural and anthropogenic sources of P. We investigated near-stream chemistry and land use factors on stream water P in the urbanizing Johnson Creek watershed in Portland, OR, USA. We sampled stream water and shallow groundwater soluble reactive P (SRP) and total P (TP) and estimated P flux at 13 sites along the main stem of Johnson Creek, with eight sites in urban land use areas and five sites in nonurban land use areas. At each site, we sampled the A and B horizons, measuring soil pH, water-soluble P, acid-soluble P, base-soluble P, total P, Fe, and Al. We found continuous input of P to the stream water via shallow groundwater throughout the Johnson Creek watershed. The shallow groundwater P concentrations were correlated with stream water P within the nonurban area; however, this correlation was not found in the urban area, suggesting that other factors in the urban area masked the relationship between groundwater P and stream water P. Aluminum and Fe concentrations were inversely correlated with shallow groundwater P, suggesting that greater P adsorption to Al and Fe oxides in the nonurban area reduced availability of shallow groundwater P. Using stepwise multiple regression analysis, however, we concluded that while riparian soil chemistry was related to stream water P, land use patterns had a more significant relationship with stream water P concentrations in this urbanizing system.

Fresh Water↗
PubMedDate not supplied

Risk behaviour in an urban and a rural male adolescent population.

BACKGROUND: There is an increasing trend of risk behaviour in adolescents worldwide but very little literature is available in India on this important subject. We surveyed an urban male adolescent population and a comparable rural population to determine the difference in their risk behaviour. METHODS: A comparative cross-sectional study was conducted among 199 and 152 male adolescents from an urban village of south Delhi and a rural village in Uttar Pradesh. A pretested semi-structured interview schedule with 36 items was applied on all subjects by trained interviewers. RESULTS: Consuming alcohol, smoking, pre-marital sexual intercourse and consuming bhang (cannabis) were present in 32.2%, 25.1%, 12.5% and 11.5% of the urban village adolescents and in 1.3%, 48.7%, 11.2%, and 16.5% of those residing in the rural village, respectively. About 66.8% of urban and 51.3% of rural adolescents had indulged in physical fights and 12.5% of urban and 6.6% of rural adolescents were in possession of assault weapons such as iron rods, chains or knives sometime in the 30 days prior to the interview. CONCLUSION: The results of our study indicate that there is a high prevalence of risk behaviour in both urban and rural adolescents. However, except for smoking which was more common amongst rural adolescents all the other risk behaviours were more in those residing in urban areas. The reasons for this need to be ascertained, taking the geographical and socio-cultural factors into account, prior to considering the introduction of behaviour modification programmes.

Adolescent↗
PubMed2003

[Prevalence of allergic respiratory disorders and skin prick test in Beijing urban and suburban children: a comparative study].

OBJECTIVE: To investigate the prevalence of allergic respiratory disorders and allergens in Beijing urban and suburban children. METHODS: Using the International Study of Asthma and Allergies in Childhood Phase III Protocol, a questionnaire survey was conducted among 7,077 junior middle school students, 3,531 males and 3,546 females, aged 13-14, of 11 urban schools and 10 suburban schools in Beijing by random cluster sampling. Skin prick test with 13 common allergens was conducted among 2,126 from the 7,077 students by random cluster sampling. RESULTS: The prevalence rates of anamnestic asthma, asthma in recent 12 months, asthma after exercise in recent 12 months, and dry cough during night in recent 12 months were 12.4%, 7.2%, 25.6%, and 19.3% respectively in the urban students; all significantly higher than those in the suburban students (4.5%, 4.3%, 12.5%, and 8.3% respectively, all P < 0.01). The rates of anamnestic nasal symptoms without common cold, present nasal symptoms without common cold, and those nasal symptoms complicated with itching eyes and lacrimation were 41.6%, 35.6%, and 10.3% respectively in urban students, and 21.3% all significantly higher than those in the suburban students (21.3%, 12.3%, and 3.3% respectively, all P < 0.05). The positive rates of the 13 main allergens were significantly higher in the urban students than in the suburban students (all P < 0.01). The positive rate of Dermatophagoides farinae and D. pteronyssinus, cat hair, and Blatella germanica were 20.4%, 16.9%, 10.8%, and 11.0% respectively in the urban students, all significantly higher than those in the suburban students (3.7%, 2.7%, 3.7%, and 2.7% respectively, all P < 0.01). CONCLUSION: The prevalence rates of allergic disorders have been increased in comparison with those in the last decade in Beijing junior middle school students, especially those in the urban area and may be due to the changes of environments and living styles.

Adolescent↗
PubMed2004

[Comprehensive evaluation and selection of urban eco-engineering virescent trees in Shenyang City].

Urban virescence eco-engineering is the core of urban eco-environmental construction, which can promote urban sustainable development. In urban virescence eco-engineering, the comprehensive evaluation of ecological adapt-ability and ecological effect of urban plants is the scientific basis of rational application and selection of urban garden plants. The ecological effect and integrative functions of urban virescence eco-engineering depend upon the selection and layout of garden plants. Using the methods of garden expert consultation and evaluation, this paper established systematically integrative evaluation and application indices of virescence plants in Shenyang City, from the aspects of ecological adaptability, ecological effect, beautification effect, resistance to plant diseases and insect pests, anti-pollution and economic results. According to garden experts evaluation and location of Shenyang, 200 sorts of virescence trees were evaluated and classified on the basis of the comprehensive evaluation system of virescence trees, and using cold resistance, drought resistance, barren resistance, plant diseases and insect pests resistance, anti-pollution, ornamental quality and ecological effects as the indexes. The results showed that the number of first rank trees was 58, the second was 93, methods of third was 38, and the fourth was 11, ranked by integrative performance.

China↗
PubMed2005

Monitor-based evaluation of pollutant load from urban stormwater runoff in Beijing.

As a major pollutant source to urban receiving waters, the non-point source pollution from urban runoff needs to be well studied and effectively controlled. Based on monitoring data from urban runoff pollutant sources, this article describes a systematic estimation of total pollutant loads from the urban areas of Beijing. A numerical model was developed to quantify main pollutant loads of urban runoff in Beijing. A sub-procedure is involved in this method, in which the flush process influences both the quantity and quality of stormwater runoff. A statistics-based method was applied in computing the annual pollutant load as an output of the runoff. The proportions of pollutant from point-source and non-point sources were compared. This provides a scientific basis for proper environmental input assessment of urban stormwater pollution to receiving waters, improvement of infrastructure performance, implementation of urban stormwater management, and utilization of stormwater.

China↗