Uneven distribution of urban green spaces in a coastal city in northwest Mexico

ABSTRACT

Extent and distribution of urban green spaces (UGS) in Mazatlan (Mexico) are analysed using remote sensing and GIS techniques. Vegetated areas (2,270?ha), a third of the urban area in 2015, were reclassified into green spaces (GS), urban tree (UT) and open spaces (OS), based in the normalised difference vegetation index, relating them with demographic and socioeconomic data. UGS allocation per capita amount 55?m², mainly represented by the UT class, with the largest patches associated with low developed and very high marginalised areas, and also with very low marginalised sectors, while the lowest allocation correspond to medium and low marginalisation, highly populated sector, without significant correlations. Despite the USG allocation, it is required a better urban planning to maintain public UGS and to protect the local flora, threatened by the introduction of exotic, ornamental species (64% of UT), to guarantee the provision of ecosystem services to the population.     

Gathering “wild” food in the city: rethinking the role of foraging in urban ecosystem planning and management

Recent “green” planning initiatives envision food production, including urban agriculture and livestock production, as desirable elements of sustainable cities. We use an integrated urban political ecology and human–plant geographies framework to explore how foraging for “wild” foods in cities, a subversive practice that challenges prevailing views about the roles of humans in urban green spaces, has potential to also support sustainability goals. Drawing on research from Baltimore, New York City, Philadelphia, and Seattle, we show that foraging is a vibrant and ongoing practice among diverse urban residents in the USA. At the same time, as reflected in regulations, planning practices, and attitudes of conservation practitioners, it is conceptualised as out of place in urban landscapes and an activity to be discouraged. We discuss how paying attention to urban foraging spaces and practices can strengthen green space planning and summarise opportunities for and challenges associated with including foragers and their concerns.     

Assessing the socio-economic impacts of green/blue space,urban residential and road infrastructure projects in the Confluence (Lyon): a hedonic pricing simulation approach

Urban green/blue spaces are put under pressure as urban areas grow, develop and evolve. It is increasingly recognized, however, that green/blue spaces provide important ecosystem services, stimulate higher real estate prices and prevent flooding problems. This paper aims to assess and compare the socio-economic impacts of potential green/blue space, urban residential and road infrastructure development scenarios in the Lyon Confluence project area (France), using the Sustainable Urbanizing Landscape Development (SULD) hedonic pricing simulation model. Results show four major tendencies regarding the value-added of green/blue spaces in urban landscapes: (1) cities become more compact; (2) population densities increase; (3) real estate values rise; and (4) demographic distribution patterns change. The magnitude of these impacts depends, however, on the quality and size of the intervention, the social classes attracted to the intervention area and on the location of the intervention relative to existing residential areas, urban centres, road infrastructure and environmental amenities.     

Sustainable development of building of extensive roof greening in Taiwan

Taiwan government specifies that the average roof thermal transmittance must be less than 0.8 (w/(m²·k)) for the design of all residential buildings in order to implement the policy of saving energy. However, self-disciplined architects practice the design of aesthetic roof to blend in with green landscape so that they urgently expect the academia to provide roof greening technical information to support their idea of designing green roofs for residential buildings. In this research, a single-family housing unit is used for investigating the possibility of applying extensive roof greening to achieve building sustainable development. The experiment tasks focused on the soil denudation caused by rainwater washing and replenishing the soil carbon by irrigating the soil with gray water. Using tap water to irrigate the green roof for 12, 16, and 14 weeks causes nitrogen, phosphate, and potassium, respectively, to be reduced to less than the original levels, respectively. Applying gray water to irrigate the green roof soil will raise the soil fertility by improving nitrogen and phosphate but not obvious for potassium.     

设立国家高新区能否驱动城市绿色发展——基于双重差分法的经验数据

国家高新区是新时代中国落实创新驱动发展战略、实现经济高质量发展和绿色发展的重要制度安排。本研究以2008年之后设立了国家高新区的城市为实验组,以一直未设立国家高新区的城市为对照组,形成2003—2019年的231个城市的面板数据,采用多期双重差分法实证检验国家高新区的设立对城市绿色发展水平的驱动作用及其机制。研究发现,设立国家高新区能显著提升城市绿色发展水平,但提升效应有待进一步加强。其机制主要是国家高新区通过提高经济增长质量和资源节约利用水平,提升环境治理和生态保护水平,改善居民绿色行为和居住环境,进而提升城市的绿色生产指数、绿色生态指数和绿色生活指数。以上结论表明国家高新区可通过推动产业结构提档升级和节能减排来进一步增强绿色先行示范作用,引领城市绿色发展。     

PATTERNS OF PERIPHYTON CHLOROPHYLL α IN AN AGRICULTURAL NONPOINT SOURCE IMPACTED STREAM1

ABSTRACT: An agricultural nonpoint source polluted stream in northern Idaho was examined to determine seasonal and longitudinal patterns of periphyton chlorophyll α. Chlorophyll a was measured at eight sites along Lapwai Creek, a fifth order stream impacted by agricultural runoff containing nutrients and eroded soils. Seasonally, periphyton chlorophyll α was lowest in the spring (cumulative x?= 60.4 mg m^?2) and highest in the summer (cumulative x?= 222 mg m^?2). Winter concentrations were higher than expected (cumulative x?= 168.6 mg m^?2). The headwaters, flowing through an open grassy meadow, had the lowest concentrations of the study (two-year x?= 49.7 mg m^?2). Immediately below a small, eutrophic reservoir, periphyton chlorophyll α increased markedly (two-year x?= 155.8 mg m^?2) and remained high through a deep canyon (two year x?= 135.5 mg m^?2) and down to the mouth of the stream (two-year x?= 172.3 mg^?2). Periphyton chlorophyll α in Lapwai Creek was at least two times greater than values reported in the literature for comparable, undisturbed Idaho streams. We suggest that increased nutrient concentrations via agricultural nonpoint source pollution and increased light penetration from the removal of large, woody riparian vegetation have resulted in high periphyton chlorophyll α along the continuum of Lapwai Creek.     

FACTORS AFFECTING PESTICIDE OCCURRENCE AND TRANSPORT IN A LARGE MIDWESTERN RIVER BASIN1

ABSTRACT: Several factors affect the occurrence and transport of pesticides in surface waters of the 29,400 km² White River Basin in Indiana. A relationship was found between pesticide use and the average annual concentration of that pesticide in the White River, although this relationship varies for different classes of pesticides. About one percent of the mass applied of each of the commonly used agricultural herbicides was transported from the basin via the White River. Peak pesticide concentrations were typically highest in late spring or early summer and were associated with periods of runoff following application. Concentrations of diazinon were higher in an urban basin than in two agricultural basins, corresponding to the common use of this insecticide on lawns and gardens in urban areas. Concentrations of atrazine, a corn herbicide widely used in the White River Basin, were higher in an agricultural basin with permeable, well‐drained soils, than in an agricultural basin with less permeable, more poorly drained soils. Although use of butylate and cyanazine was comparable in the White River Basin between 1992 and 1994, concentrations in the White River of butylate, which is incorporated into soil, were substantially less than for cyanazine, which is typically applied to the soil surface.     

Release,Dispersion, and Resuspension of Escherichia coli From Direct Fecal Deposits Under Controlled Flows1

Abstract: Water‐quality standards have been placed on fecal indicator organisms such as Escherichia coli in an attempt to limit the concentrations in water bodies. Cattle can be a significant source of bacteria to water systems, particularly when they are allowed direct access to streams. A flume study was conducted to quantify the effect and understand the transport of E. coli from directly deposited cattle manure. Five steady‐state flows, ranging from 0.00683 to 0.0176 m³/s, were studied and loads from a single cowpie exceeded the U.S. Environmental Protection Agency’s recommended water‐quality standards (235 CFU/100 ml) at each flow over the hour study period. Average E. coli concentrations ranged from 10² to 10⁵ CFU/100 ml over the hour sampling period for all flows. High spatial variations in E. coli concentrations were often seen at each sampling time, with higher concentrations typically at the bottom of the flume. E. coli resuspension was initially greater at 0.5 min after deposition, for the lowest flow (10⁵ CFU/m²/s); however, resuspension rates became similar over time, on the order of 10³ CFU/m²/s. This study demonstrates that the concentrations of E. coli can vary over the water column, and therefore grab samples may inaccurately measure bacteria concentrations and loads in streams. In addition, resuspension rates were often high, so the incorporation of this process into water‐quality models is important for bacteria prediction.     

Analyzing the cost effectiveness of Santiago, Chile's policy of using urban forests to improve air quality

Santiago, Chile has the distinction of having among the worst urban air pollution problems in Latin America. As part of an atmospheric pollution reduction plan, the Santiago Regional Metropolitan government defined an environmental policy goal of using urban forests to remove particulate matter less than 10 microm (PM(10)) in the Gran Santiago area. We used cost effectiveness, or the process of establishing costs and selecting least cost alternatives for obtaining a defined policy goal of PM(10) removal, to analyze this policy goal. For this study, we quantified PM(10) removal by Santiago's urban forests based on socioeconomic strata and using field and real-time pollution and climate data via a dry deposition urban forest effects model. Municipal urban forest management costs were estimated using management cost surveys and Chilean Ministry of Planning and Cooperation documents. Results indicate that managing municipal urban forests (trees, shrubs, and grass whose management is under the jurisdiction of Santiago's 36 municipalities) to remove PM(10) was a cost-effective policy for abating PM(10) based on criteria set by the World Bank. In addition, we compared the cost effectiveness of managing municipal urban forests and street trees to other control policies (e.g. alternative fuels) to abate PM(10) in Santiago and determined that municipal urban forest management efficiency was similar to these other air quality improvement measures.     

城市化及其对大气环境的影响

中国城市化的快速发展与能源消耗的迅速增加,给中国城市带来了众多大气环境问题。城市化不仅造成了如热岛效应等城市周边气候的变化,还带来了酸雨频发、空气颗粒物污染加重和汽车尾气污染严重等城市环境问题。对此,应当从科学编制城市发展规划,合理调整经济结构,加强环境管理与污染治理,增加城市绿化面积等方面入手,改善城市大气环境。     

2017～2018年荆州城区空气质量分布及重污染天气特征分析

利用2017年1月至2018年12月荆州城区3个国家环境空气质量监测点的污染物监测数据和荆州国家气象站地面气象要素观测数据,采用统计学方法,对荆州城区空气质量分布及重污染过程天气特征进行了初步分析,结果表明:空气污染综合指数冬季最高,春秋季次之,夏季最低;PM2.5、PM10、 CO和NO2的浓度在上午和傍晚至上半夜其...     

ESTIMATING RUNOFF VOLUMES FROM URBAN AREAS1

ABSTRACT: Estimations of runoff volumes from urban areas can be made by the equation Q = a A σ(P_e– b), where Q is the runoff volume, a is the part of the total area A Contributing to runoff, P_e is the rainfall amount for a single event, and b is the initial rainfall losses. For the evaluation of a and b, rainfall/runoff measurements were made in five areas of sizes between 0.035 km² and 1.450 km². By linear regression analysis of rainfall volumes versus runoff volumes, the initial rainfall losses were found to vary from 0.38 mm to 0.70 mm for the different areas. The parts of the areas contributing to runoff were found to be proportional to the impermeable parts of the mas. The equation is applicable in urban areas with well defined paved surfaces and roofs and with a negligible amount of runoff from permeable areas.     

Nonpoint Source Loading Rates From Selected Land Uses1

ABSTRACT: Loading rates derived from monitoring natural runoff from selected land uses are compared. Land uses selected for evaluation are construction sites, barnyards, and agriculture (dairying). Runoff volumes, sediment, and nutrient fractions were monitored and expressed as areal loadings for comparison purposes. Sediment yield and total phosphorus (total P) loss was directly proportional to runoff (m³/ha). In decreasing order, the loadings for sediment and total P were as follows: construction site > barnyard > general dairying. Runoff from the barnyard area was approximately 10 times higher in soluble phosphorus and ammonium nitrogen than the other land uses under investigation. Areal loss for nitrate nitrogen was highest from the construction site and was attributed to the higher volume of runoff per unit area. Results show that barnyards in a dairying watershed are potentially a major source of sediment and nutrients, especially those dissolved fractions which have the potential for immediate water quality impacts. Relative to general agricultural land, urban construction sites also appear to be a major source of sediment and nutrients. As with barnyard sites, however, the effect of such sites on water quality likely depends on proximity to surface water bodies and other watershed characteristics affecting delivery ratios of contaminants.     

Back to nature: new urban policy and environmental governance in Canada's capital

Drawing on a growing literature on the integration of environmental discourses into urban development schemes, this paper charts the urban development of LeBreton Flats, in Ottawa, Ontario, Canada. An industrial neighbourhood expropriated as part of a post-war urban renewal project, LeBreton Flats is being redeveloped in line with green, mixed-use urban planning principles. The paper investigates how national narratives are intertwined within urban development practices and argues that historically and geographically embedded expressions of national nature first used to justify post-war expropriation are being adapted as part of urban neo-liberal naturalised practices of central-city redevelopment.     

Hydrologic Controls on Nitrogen and Phosphorous Dynamics in Relict Oxbow Wetlands Adjacent to an Urban Restored Stream

Although wetlands are known to be sinks for nitrogen (N) and phosphorus (P), their function in urban watersheds remains unclear. We analyzed water and nitrate (NO₃^?) and phosphate (PO₄^3?) dynamics during precipitation events in two oxbow wetlands that were created during geomorphic stream restoration in Baltimore County, Maryland that varied in the nature and extent of connectivity to the adjacent stream. Oxbow 1 (Ox1) received 1.6‐4.2% and Oxbow 2 (Ox2) received 4.2‐7.4% of cumulative streamflow during storm events from subsurface seepage (Ox1) and surface flow (Ox2). The retention time of incoming stormwater ranged from 0.2 to 6.7 days in Ox1 and 1.8 to 4.3 days in Ox2. Retention rates in the wetlands ranged from 0.25 to 2.74 g N/m²/day in Ox1 and 0.29 to 1.94 g N/m²/day in Ox2. Percent retention of the NO₃^?‐N load that entered the wetlands during the storm events ranged from 64 to 87% and 23 to 26%, in Ox1 and Ox2, respectively. During all four storm events, Ox1 and Ox2 were a small net source of dissolved PO₄^3? to the adjacent stream (i.e., more P exited than entered the wetland), releasing P at a rate of 0.23‐20.83 mg P/m²/day and 3.43‐24.84 mg P/m²/day, respectively. N and P removal efficiency of the oxbows were regulated by hydrologic connectivity, hydraulic loading, and retention time. Incidental oxbow wetlands have potential to receive urban stream and storm flow and to be significant N sinks, but they may be sources of P in urban watersheds.     

From socioeconomic disparity to environmental injustice: the relationship between housing unit density and community green space in a medium city in Pakistan

Rapid urbanisation, lack of proactive planning and improper allocation of resources may result in socio-economic disparity among and within cities, causing social unrest and environmental injustice in the neighbourhoods. This study aims to examine whether the planning standards for housing schemes in Pakistan are able to maintain equitable access to green spaces within the cities. Ten residential sites in Sheikhupura city with different housing unit sizes and densities were selected for the study. The supply of urban green infrastructure in housing scheme has been assessed: (i) by comparing the percentage of green spaces, including community parks and open spaces and street landscape; and (ii) by calculating per dwelling unit and per capita share of green spaces. These indicators have been studied against the housing density and population density of the schemes by applying correlation and linear regression models. The results show that all the housing schemes plans provide for similar amounts of green space as a percentage of total area. The per capita share of green spaces is very low in high-density areas, but interestingly, the street landscape has a higher potential to contribute to the overall landscape in high-density neighbourhoods, compensating for low per capita green space. Housing unit density and population density must be incorporated in planning standards so planners can effectively devise a mix of community parks, street landscape and private green spaces to help maintain per capita green spaces, and hence environmental resource equality in different parts of the city.     

Using nighttime light data to estimate water evaporation inside buildings in China's urban areas

Urbanization has a great impact on urban evapotranspiration. Water evaporation inside buildings is an important part of urban water vapor resources and a crucial core of urban hydrological processes. The systematic studies on building water evaporation (BWE) are mostly the method of experimental monitoring. This study proposed a new method to simulate and estimate water evaporation flux inside buildings in urban areas. Based on the nighttime light data and urban per capita gross domestic product (GDP), a new modeling system was built to simulate the total BWE. Building area was calculated using the nighttime light data. And the BWE coefficient D_f was estimated according to the important indicator of economic development per capita GDP value. Then the water evaporation inside urban buildings and the spatial distribution of water evaporation inside buildings in typical cities could be obtained. The results showed that the total amount of water evaporation inside buildings in China's urban areas was 24.5 billion m³. Among the 31 provincial capitals in China, Shanghai had the largest BWE of 1.08 billion m³. The minimum water evaporation of buildings in Lhasa was 20.0 million m³. Studies of BWE can assess urban water budgets, support on-demand allocation of water resources, and provide a fundamental understanding of the relationship between water resources and energy heat island effects in urban areas.     

Public parks as an element of urban planning: a missing piece in Accra's growth and development

Public parks are important to urban environments, residents, and visitors. Among other functions, they provide environmental services, such as air and water purification, and they increase both recreational opportunities and the attractiveness of the urban environment. Because of their importance, urban parks serve as public spaces that provide visitors and urban residents with rights to the city. This paper identifies the dearth of urban public parks in Accra-Tema city-region as worrying. The Accra Plan 1958 underscored the significance of green spaces and designated the coastal strip for parks development but the areas have been lost to various urban uses. We argue that the continual neglect of public parks within urban planning and community development schemes in the Accra-Tema city-region is a major concern because it is depriving the citizens a right to the city and its public spaces. A number of factors have worked adversely against the provision of public parks and green spaces in the city-region. These include development pressures, undue political interference, a complex land delivery system, and ad hoc planning. The paper concludes by offering policy suggestions as to how to resolve the dearth of parks and green spaces in the city-region.     

城市蔓延、私人交通与雾霾污染

本文选取中国280个地级市2009—2018年的面板数据为研究样本,探究城市蔓延与雾霾污染之间的作用机制。以私人交通为门槛变量,考察城市蔓延对雾霾污染的门槛效应。研究结果表明：(1)城市蔓延对雾霾污染的影响呈现出先降后升的U形曲线特点;(2)私人交通对雾霾污染的影响表现为倒U形的曲线特征,即随着私人交通发展水平的提高,雾霾污染呈现先增后减的趋势;(3)城市蔓延对雾霾污染的影响存在双重门槛效应,当私人交通的门槛值小于第一个门槛值(e^11.6130=110 525辆)时,城市蔓延会加剧雾霾污染;当私人交通的门槛值介于第一个门槛值和第二个门槛值(e^12.2473=208 417辆)之间时,城市蔓延对雾霾污染的影响系数为正,但未通过显著性检验;当私人交通跨过第二个门槛值时,城市蔓延水平的提高有助于抑制雾霾污染。研究城市蔓延、私人交通与雾霾污染这三者之间的关系对于促进城市的健康可持续发展具有重要的意义。     

Assessing spatial equality of urban green spaces provision: a case study of Greater Doha in Qatar

Greater Doha is experiencing lack of sufficient urban green spaces (UGS) as a result of rapid urbanisation to cater for the fast population growth in the country. The availability of green spaces and the improvement of the green/built-up area ratio have been recognised by planners as a key factor in improving the life quality of city dwellers. This study aims at addressing the adequacy and spatial distribution of public parks in Greater Doha. The current status of public parks is assessed in relation to the population distribution using GIS and remote sensing techniques. The results show that the majority of administrative zones fell well below the adopted public parks standards. The park provision ratio ranged from 0 and 0.03 through 0.43 and 0.48 to 0.92 and 0.99 hectare (ha) per 1000 population, with an average of 0.37. After quantifying this deficiency in UGS, the study suggest remedy by identifying vacant parcels in each zone to match the adopted standards, taking into consideration their spatial distribution and minimum area criteria.