Pollutant loads of surface runoff in Wuhan City Zoo, an urban tourist area

The pollutant loads of surface runoff in an urban tourist area have been investigated for two years in the Wuhan City Zoo, China. Eight sampling sites, including two woodlands, three animal yards, two roofs and one road, were selected for sampling and study. The results indicate that pollutants ranked in a predictable order of decreasing load （e.g. animal yard〉roof〉woodland〉road）, with animal yards acting as the key pollution source in the zoo. Pollutants were transported mainly by particulate form in runoff. Particulate nitrogen and particulate phosphorous accounted on average for 61%, 78% of total pollutant, respectively, over 13 monitored rainfall events. These results indicate the treatment practices should be implemented to improve particulate nutrient removal. Analysis of the M（V） curve indicate that no first flush effect existed in the surface runoff from pervious areas （e.g. woodland, animal ground yard）, whereas a first flush effect was evident in runoff from impervious surfaces （e.g. animal cement yard, roof, road）.

Examining the Relationship Between Spatial Configurations of Urban Impervious Surfaces and Land Surface Temperature

The urban heat island(UHI) effect has significant effects on the quality of life and public health. Numerous studies have addressed the relationship between UHI and the increase in urban impervious surface area(ISA), but few of them have considered the impact of the spatial configuration of ISA on UHI. Land surface temperature(LST) may be affected not only by urban land cover, but also by neighboring land cover. The aim of this research was to investigate the effects of the abundance and spatial association of ISAs on LST. Taking Harbin City, China as an example, the impact of ISA spatial association on LST measurements was examined. The abundance of ISAs and the LST measurements were derived from Landsat Thematic Mapper(TM) imagery of 2000 and 2010, and the spatial association patterns of ISAs were calculated using the local Moran’s I index. The impacts of ISA abundance and spatial association on LST were examined using correlation analysis. The results suggested that LST has significant positive associations with both ISA abundance and the Moran’s I index of ISAs, indicating that both the abundance and spatial clustering of ISAs contribute to elevated values of LST. It was also found that LST is positively associated with clustering of high-ISA-percentage areas(i.e.,>50%) and negatively associated with clustering of low-ISA-percentage areas(i.e.,<25%). The results suggest that, in addition to the abundance of ISAs,their spatial association has a significant effect on UHIs.

Using Impervious Surfaces to Detect Urban Expansion in Beijing of China in 2000s

The change of impervious surface area(ISA) can effectively reveal the gradual process of urbanization and act as a key index for monitoring urban expansion. Experiencing rapid growth of the built environment in the 2000 s, urban expansion of Beijing has not been fully characterized through ISA. In this study, Landsat TM images of Beijing in 2001 and 2009 were obtained, and the eight-year urban expansion process in Beijing was analyzed using the ISA extracted by means of the vegetation-imperious surface-soil(V-I-S) model. From the spatial variation in ISA, the ring structure of urban expansion in Beijing was significant during the study period, with decreasing urban density from the city center to the periphery. In the ring road analysis, the most dramatic changes of ISA were found between the fifth ring and the sixth ring. This area has experienced the most new residential development, and is currently the main source of urban expansion. The typical profile lines revealed the directional characteristics of urban expansion. The east-west profile was the most urbanized axes in Beijing, while ISA change in the east-north profile was more significant than in the other five profiles. Moreover, the transition matrix of ISA levels revealed an increase in urban density in the low density built areas; the Moran′s I index showed a clear expansion of the central urban area, which spread contiguously; and the standard deviational ellipse indicated the northeast was the dominant direction of urban expansion. These findings can provide important spatial control guidelines in the next round of national economic and social development planning, overall urban and rural planning, and land use planning.

中国城市植被物候变化及其对地表温度的响应

量化植被物候与城市化进程之间的关系对探索人类活动对城市生态系统的影响至关重要。以中国35个城市及周边区域为研究对象,基于中分辨率成像光谱仪(Moderate-resolution Imaging Spectroradiometer,MODIS)提供的归一化植被指数(Normalized Difference Vegetation Index,NDVI),采用Savitzky-Golay滤波和动态阈值法提取2000—2020年研究区植被返青期(Start of Growing Season,SOS)和枯黄期(End of Growing Season,EOS)。并分析不同城市规模、不同距离城市的植被物候变化对陆地地表温度(Land Surface Temperature,LST)与不透水面(Impervious Surface Area,ISA)的响应差异。研究发现:(1)2000—2020年,中国城市城区植被SOS和EOS分别以0.17d/a和0.15d/a的速率推迟。根据城市规模的不同,大城市和中等城市物候期呈推迟趋势,而超大城市、特大城市和小城市呈提前趋势。51%的城市植被SOS提前,主要分布在中国华北、西北及南部地区,其他地区城市植被SOS推迟(49%),80%的城市植被EOS推迟。空间上看,东部和南部平原地区城市植被SOS比西北部地区早(早于第91天),而EOS则比较晚(晚于第314天),而西部和北部城市植被SOS(晚于第91天)和EOS(早于第314天)呈相反态势;(2)距离城区越近,63%的城市表现为植被SOS提前(0.6—4.3 d/km),60%的城市表现为植被EOS推迟(0.2—1.9 d/km);(3)所有城市春季LST均呈现增长趋势,春季ΔLST每增长1℃,SOS提前6.8 d。秋季ΔLST每增长1℃,EOS推迟1.5 d。城市植被SOS与ISA占比显著负相关,ISA占比增长1%,植被SOS提前0.253 d,植被EOS与ISA占比显著正相关,ISA占比每增长1%,植被EOS推迟0.106 d。此外,不同人口规模的城市植被物候对LST和ISA响应存在差异,大城市和超大城市植被物候对LST和ISA占比的响应比其他城市更为敏感,表明特大城市和大城市在城郊梯度上植被物候期对LST与ISA占比响应更为明显。

多源数据加权融合的城市建成区改进指数评估

针对多源数据提取建成区的研究大多集中在等权融合方向,缺乏考虑不同数据源包含的信息量差异的问题,通过多源数据加权融合方法对前人的城市建成区提取指数进行改进,以改善不同质量级数据直接融合导致建成区提取不准确的问题。首先,构建融合夜间灯光数据、NDVI数据、路网数据和POI数据的改进PREANI指数;其次,融入不透水面数据和温度数据构建无权指数UCI和有权指数WCI;最后,选择迭代法和动态阈值法提取建成区,并对3种指数分别进行评估。结果表明:改进PREANI的Kappa系数为0.80,UCI融入温度和不透水面数据将Kappa系数提高至0.83;WCI提取的建成区轮廓更准确,在增强城乡建成区细部对比、提升边缘地物区分能力方面表现良好,其Kappa系数、查全率、查准率和F1分数均在0.85以上。

Mapping global impervious surface area and green space within urban environments

The mapping of impervious surface area(ISA) and urban green space(UGS) is essential for improving the urban environmental quality toward ecological, livable, and sustainable goals. Currently, accurate ISA and UGS products are lacking in urban areas at the global scale. This study established regression models that estimated the fraction of ISA/UGS in global 30 cities for validation using MODIS NDVI and DMSP/OLS nighttime light imageries. A global dataset of ISA and UGS fraction with a spatial resolution of 250 m×250 m was developed using the regression model, with a mean relative error of 0.19 for its ISA. The results showed the global urban area of 76.29×10~4 km^2, which was primarily distributed in central Europe, eastern Asia,and central and eastern North America. The urban land area in North America, Europe, and Asia was 66.3×10~4 km^2, accounting for 86.91% of the world’s urban area;the urban land area of the top 50 countries accounted for 59.32% of the total urban land area in the world. The global ISA of 45.26×10~4 km^2 was mainly distributed in central and southern North America, eastern Asia, and Europe, as well as coastal regions around the world. The proportion of ISA situated in built-up areas on the continental scale followed the order of Africa(>70%)>South America>Oceania>Asia(>60%)>North America>Europe(>50%), and these areas were mostly in southeastern North America, southwestern Europe, and eastern and western Asia. North America, Europe, and Asia accounted for 89.44% of the world’s total UGS. The cities of developed countries in Europe and North America exposed a dramatic mosaic of ISA and UGS composites in urban construction. Therefore, the proportion of UGS is relatively high in those cities. However, in developing and underdeveloped countries, the proportion of UGS in built-up areas is relatively low, and urban environments need to be improved for livability.

Evaluating impervious surface growth and its impacts on water environment in Beijing- Tianjin-Tangshan Metropolitan Area

The impervious surface area （ISA） at the regional scale is one of the important environmental factors for examining the interaction and mechanism of Land Use/Cover Change （LUCC）-ecosystem processes-climate change under the interactions of urbanization and global environmental change. Timely and accurate extraction of ISA from remotely sensed data at the regional scale is challenging. This study explored the ISA extraction based on MODIS and DMSP-OLS data and the incorporation of China＇s land use/cover data. ISA datasets in Beijing-Tianjin-Tangshan Metropolitan Area （BTTMA） in 2000 and 2008 at a spatial resolution of 250 m were developed, their spatiotemporal changes were analyzed, and their impacts on water quality were then evaluated. The results indicated that ISA in BTTMA increased rapidly along urban fringe, transportation corridors and coastal belt both in intensity and extents from 2000 to 2008. Three cities （Tangshan, Langfang and Qinhuangdao） in Hebei Province had higher ISA growth rates than Beijing due to the pressure of population-resour- ces-environments in the city resulting in increasingly transferring industries to the nearby areas. The dense ISA distribution in BTTMA has serious impacts on water quality in the Haihe River watershed. Meanwhile, the proportion of ISA in sub-watersheds has significantly linear relationships with the densities of river COD and NH3-N.

海口城市空间差异对外来入侵植物分布格局的影响

【目的】城市是外来入侵物种引入和二次传播的主要地区,城市环境中的入侵植物会对生物多样性和社会经济造成影响。阐明城市空间差异对入侵植物分布格局的影响,可为海口市生物入侵科学管理提供参考。【方法】以海口市主城区为研究区域,通过对461块随机样方的调查,记录外来入侵植物种类、盖度、平均株高和样方环境信息。从入侵植物的样方发生率、物种组成、丰富度和多度等方面,比较其在城市化梯度和土地利用类型上的发生差异和分布特征。【结果】(1)调查共记录外来入侵植物36种,隶属13科31属,其中菊科为优势科;以一年生和原产地为热带美洲的草本居多。(2)城市核心区和城市边缘区的入侵植物丰富度显著高于城市郊区,但城市郊区的多度显著高于城市核心区和城市边缘区。(3)在居住区、交通用地、空闲地、商业/单位/工矿用地中,入侵植物的发生概率与不透水面百分比呈负相关,而在林地、农业用地和城市公共绿地中,入侵植物更容易发生在不透水面百分比较高的区域。【结论】城市化梯度和土地利用类型均显著影响入侵植物的分布格局,不透水面的比例作为一个重要的解释因子,可以为入侵植物的发生提供预判参考。

Spatiotemporal dynamics of impervious surface areas across China during the early 21st century

China has experienced an unprecedented urbanization and industrialization in the past decades. In this research, we examined the dynamics of construction lands and impervious surface areas (ISA) based on land use/cover change and ISA datasets between 2000 and 2008, which were provided by the national resources and environmental remote sensing information platform. The results indicated that the construction areas and ISA increased by 3468.30 and 2212.24 km 2 /a in this period primarily due to the implementation of national macro-development strategies and fast-growing economy. In 2008, ISA accounted for 0.86% of the total land area in China. Urban land areas increased by 43.46% between 2000 and 2008. The annual growth rate of 1788.22 km 2 /a in this period was 2.18 times that in the 1990s. In particular, urban ISA increased by 53.30% between 2000 and 2008 with an annual growth rate of 1348.85 km 2 /a. During the 8 years, the ISA in China increased rapidly, especially in the Beijing-Tianjin-Tangshan Metropolitan Region, Pearl River Delta, Yangtze River Delta, and the western China region. The increasing ISA may influence potentially water environmental quality in the major basins. In particular, the number of subbasins having ISA of greater than 10% increased considerably, which were primarily distributed in the Haihe River, Yangtze River and Pearl River basins. In 2008, 14.42% of the basin areas were affected by the increased ISA.

Methods to extract impervious surface areas from satellite images

Impervious surface area(ISA)is an important parameter for many environmental or socioeconomic relevant studies.The unique characteristics of remote sensing data made it the primary data source for ISA mapping at various scales.This paper summarizes general ISA mapping procedure and major techniques and discusses impacts of scale issues on selection of remote sensing data and corresponding algorithms.Previous studies have indicated that ISA mapping remains a challenge,especially in urban–rural frontiers and in covering a large area.Effectively employing rich spatial information in high spatial resolution imagery through texture and objectbased methods is valuable.Data fusion of multi-resolution images and spectral mixture analysis are common approaches to reduce the mixed pixel problem in medium spatial resolution images such as Landsat.Coarse spatial resolution images such as MODIS and DMSP-OLS are valuable for national and global ISA mapping but more research is needed to effectively integrate multisource/scale data for improving mapping performance.Development of an optimal procedure corresponding to specific study areas and purposes is required to generate accurate ISA mapping results.

上海市土地利用空间格局与地表温度关系研究

以上海市外环内区域为研究对象,利用2011年TM和航空影像数据,研究城市土地利用类型、格局特征与地表热环境分异之间的关系。研究结果表明,城市不同土地利用类型的地表温度差异较大,平均地表温度最低的是河流,为23.12℃;最高的为工业用地,为35.89℃。工业用地、道路广场用地和居住用地等的平均地表温度明显高于河流、公园和林地的平均地表温度。从各种土地利用类型在不同温度等级的分布情况来看,低温区主要由河流和公园构成,分别占低温区总面积的70.05%和10.23%;高温区主要由工业用地、仓储用地和道路广场组成,分别占高温区总面积的78.15%、6.42%和5.58%,其中河流、湖泊和别墅式住宅均没有分布在高温区域内,说明水体、公园和林地具有明显的降温效应。尽管草地也具有一定的降温效应,但其降温效果没有水体、公园等明显。城市建筑物高度与地表温度的Pearson相关性结果表明,二者之间呈现显著的负相关性(Sig.=0.012),说明地表温度随着城市建筑物的增高而降低。新式住宅、别墅式住宅地表平均温度显著低于旧式住宅。研究城市土地利用空间格局特征与地表温度的关系表明,地表温度与斑块数、斑块密度等表现出极显著的相关性,与多样性指数、均匀度指数表现出显著的相关性。多元线性回归分析结果表明:不透水率、斑块聚集度和斑块数等共同作用,影响着城市的地表温度。其中对地表温度影响最为严重的是城市不透水率,其次是斑块的聚集程度,斑块的形状特征对地表温度影响程度稍弱。上述分析表明增加景观中绿地和水体比例,提高景观多样性与复杂度,借助绿化用地对不透水地表进行分割可以明显降低地表温度。该结论可用于城市格局优化、缓解城市热岛效应。

城市不透水面及地表温度的遥感估算

基于植被-不透水面-土壤模型和全约束最小二乘法混合像元分解模型,从探索城市热岛效应和城市不透水面关系出发,利用TM数据对北京市海淀区的城市不透水面丰度和地表温度进行估算,并在此基础上对二者之间的相关性进行定性分析和定量评价。研究表明:城市不透水面的空间分布和变化趋势与地表温度之间存在明显的一致性,二者相关系数达到0.752 5,这说明城市不透水面信息可以很好地反映城市热环境的空间分布状况。

城市景观组分影响水质退化的阈值研究

运用景观格局与水质监测方法评价城市景观变化对河流水质的影响,是当前景观格局-效应研究的热点问题。为实现城市发展目标与水环境保护目标的统一,需要科学判断城市景观变化对水质的影响程度与范围,特别是以城市不透水表面为代表的景观组分变化,是目前水质退化研究中的核心对象,而对水质退化的景观阈值研究目前尚存争论。基于截面数据进行统计分析,构建阈值判定方法,选择深圳市为案例研究区,研究快速城市化地区的河流水质退化的景观阈值水平。结果表明,在深圳市,河流缓冲区宽度为100—200 m时,景观变化对水质显著性影响最高(P<0.001)。缓冲区内,景观变化与耗氧、营养盐等类指标呈指数关系,具有显著性,是这类指标变化的最主要影响因素;同时,景观变化与有毒物质及重金属等类指标呈指数关系,具有显著性,但并非这类指标变化的最主要因素。影响水质退化的不透水表面比例阈值水平介于38.2%—50%之间,最小阈值水平为38.2%,即当流域缓冲区内不透水表面百分比超过38.2%时,河流水质显著退化。

成都市地表温度对不透水面的响应研究

根据成都三环路内的Landsat 7/ETM+影像,利用单窗算法和不透水面与植被覆盖度在城市建成区呈负相关关系两种反演方法,通过空间建模建立反演模型,获取地表温度与不透水面信息。通过随机样点分析、相关性分析以及等温线与等透水面线叠加分析等方法,研究了城市地表温度对不透水面的响应效果。结果表明:地表温度随距市中心区距离增大而降低,同时不透水能力也降低;成都市地表温度与不透水面之间存在着正相关关系,相关度为0.7253;等透水面线的空间分布对等温线具有显著的响应规律。研究成果对于改善城市生态环境、提升土地利用水平和加强科学规划等都具有参考价值。

城市不透水面及其与城市热岛的关系研究——以泉州市区为例

利用Landsat TM卫星影像提取了泉州市1989到1996年的城市建成区不透水面,并研究了其与城市热岛之间的关系。根据Ridd(1995)提出的城市建成区不透水面与植被覆盖度有很强的负相关关系的思想,先利用归一化植被指数求出泉州市建成区的植被覆盖度,进而提取了泉州市建成区的不透水面。通过比较所提取的两个时相不透水面信息,可以看出泉州市区不透水面的面积在7年里有了明显的增加,并主要沿研究区东南部扩展。通过将所提取的不透水面信息与利用TM6波段反演的地表温度进行相关分析,可发现二者之间存在着明显的正相关关系。

流域非点源污染景观源汇格局遥感解析

流域非点源污染景观源汇格局解析是流域水质污染物产生、输运机理认知与有效防治措施制定的重要科学理论基础。该文以充分挖掘流域遥感数据多时空尺度的特征与优势为目标,制定了流域非点源污染景观源汇类型界定方案,提出了像元级、亚像元级以及时序更新的流域非点源污染景观源汇格局遥感解析方法。在此基础上,以福建省九龙江流域为例,对不透水面这一典型流域非点源污染"源"景观2010年空间格局进行了信息提取,并对2000、2005年对应信息进行了时序更新与空间特征分析,结果显示2000–2010年间九龙江流域内不透水面覆盖面积增长了33.38%。该研究可为中国流域非点源污染研究、生态管理与建设提供参考。

上海市快速城市化过程中地表温度与地表覆盖的关系研究

城市热岛是城市化过程带来的生态环境效应之一。城市温度升高不仅使得资源消耗增加,而且影响城市居民的生存环境和生活质量。为缓解城市热岛效应,对城市热岛的影响因素进行分析显得尤为重要。采用Landsat TM影像数据,以上海市外环内区域为研究对象,反演了5、11月的城市地表温度、归一化植被指数、改进的归一化差异水体指数和不透水面率,定量分析了它们之间的相互关系。结果表明:(1)城市地表温度与归一化植被指数、改进的归一化差异水体指数具有显著的负相关,与不透水面率具有显著的正相关。(2)城市地表温度的空间分布具有明显的季节特征,5月地表温度较高的区域主要分布在北部区域,而11月地表温度较高的区域在整个研究范围内均有分布。(3)季节因素对城市地表温度与地表覆盖参数的相关性影响较明显。多元回归结果表明,5月城市地表温度与归一化植被指数相关性最大,降温效果绿地大于水体大于城市不透水面;11月城市地表温度与改进的归一化差异水体指数相关性最大,降温效果水体大于城市不透水面大于绿地。(4)城市绿地和水体对于调节城市地表温度具有显著作用,该结果可用于优化城市格局,缓解城市热岛效应。

城市热环境季相变异及与非渗透地表的定量关系分析——以广州市中心区为例

基于遥感卫星影像的热环境时空格局及与地表特征相关性分析是目前城市热环境研究的主要内容,但此类研究针对季相变异特征的分析较为缺乏。以广州市中心区2005年下半年3期不同季相的Landsat TM影像为数据源,提出一种面向对象分割的方法提取城市热岛/冷岛分布,并利用重心模型定量其季相变化移动轨迹;采用回归树模型构建地表温度(Land surface temperature,LST)与非渗透地表的关系方程,旨在揭示城市热环境季相变异性规律。结果表明:(1)随夏季到深秋,热岛呈现从中心区退出的态势,南部冷岛大面积消失,7月18日至10月22日热岛重心向东移动2.5 km,冷岛重心向西北移动3.4 km。10月22日至11月23日冷岛重心向西北移动9 km,热岛重心向东南移动8 km;(2)随季相变化,地表温度与非渗透地表的正相关关系趋于复杂,二者相关性从7月18日的0.994 1降至11月23日的0.869 1,对于11月23日数据,使用二次多项式方程更能表达二者的关系;(3)与传统的线性回归模型相比,回归树模型能更好地模拟地表温度的空间异质性,非渗透地表的增温作用存在非线性趋势,并且二者的关系模型存在明显的空间异质性。

多时相Landsat影像的平原河网区不透水面信息提取方法与应用

不透水面是衡量城市生态环境的重要指标,针对平原河网区不透水面与水体、裸土等地物较难区分的问题,以苏北里下河平原快速城镇化区为研究对象,利用多时相Landsat影像为数据源,基于像元光谱特征及其季节性变化分析,构建了基于时序NDWI、NDVI和NDBI的决策树模型,并利用GIS空间分析技术对不透水面的时空变化特征进行了分析。结果表明:多时相光谱信息可有效改善水体、裸土和稀疏植被等像元与不透水面的混分,2005年和2016年的不透水面分类总体精度和Kappa系数均在0.85以上,合理反映了不透水面以向东和向南扩张为主的趋势特征,年均扩张速度约为6.7 km2。研究成果为该区城镇化下的生态环境效应研究提供数据基础,同时可为其他平原河网区不透水面信息提供借鉴和参考。

基于类NPP-VIIRS夜间灯光数据的粤港澳大湾区城市建成区时空动态特征

随着人口增长与经济发展,快速准确地获取城市建成区扩张信息,并对其时空特征进行分析,对于今后城市可持续发展具有重要意义。基于2000~2018年类NPP-VIIRS夜间灯光数据的大尺度不透水面指数提取粤港澳大湾区城市不透水面,并基于统计数据比较法得到城市建成区,对粤港澳大湾区以及各城市的建成区扩张进行时空分析。结果表明:①类NPP-VIIRS夜间灯光数据实现了对城市建成区的高精度提取,可为城市长时间序列的时空变化监测提供新的数据基础;②粤港澳大湾区城市建成区由2000年的1279.00 km^(2)增加到2018年的4730.25 km^(2),广州、深圳、东莞的建成区扩张最为明显,分别增加了793.50、812.75、1027.50 km^(2);在空间上,粤港澳大湾区城市建成区扩张主要发生在各城市之间的交界地带,逐步形成了佛山—广州—东莞—深圳—香港大型城市群核心建成区,西部地区发展相对较慢;③粤港澳大湾区城市建成区重心2000~2018年由东莞转移到广州。总之,粤港澳大湾区城市建成区在2000~2018年扩张整体呈现由快变慢、东快西慢的特点。