The footprint of urban heat island effect in China
TL;DR: Using MODIS data from 2003 to 2012, it is shown that the UHI effect decayed exponentially toward rural areas for majority of the 32 Chinese cities, and an obvious urban/rural temperature “cliff” is found.
Abstract: Urban heat island (UHI) is one major anthropogenic modification to the Earth system that transcends its physical boundary. Using MODIS data from 2003 to 2012, we showed that the UHI effect decayed exponentially toward rural areas for majority of the 32 Chinese cities. We found an obvious urban/rural temperature “cliff”, and estimated that the footprint of UHI effect (FP, including urban area) was 2.3 and 3.9 times of urban size for the day and night, respectively, with large spatiotemporal heterogeneities. We further revealed that ignoring the FP may underestimate the UHI intensity in most cases and even alter the direction of UHI estimates for few cities. Our results provide new insights to the characteristics of UHI effect and emphasize the necessity of considering city- and time-specific FP when assessing the urbanization effects on local climate.
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TL;DR: In this paper, the NiCo2S4 NW/NF arrays on a 3D Ni foam (NF) were used for solar-to-hydrogen (S2H) generation, achieving a hydrogen production current density of 10 mA cm-2 at an overpotential of 260 mV for the oxygen evolution reaction and at 210 mV (versus a reversible hydrogen electrode).
Abstract: A recent approach for solar-to-hydrogen generation has been water electrolysis using efficient, stable, and inexpensive bifunctional electrocatalysts within strong electrolytes. Herein, the direct growth of 1D NiCo2S4 nanowire (NW) arrays on a 3D Ni foam (NF) is described. This NiCo2S4 NW/NF array functions as an efficient bifunctional electrocatalyst for overall water splitting with excellent activity and stability. The 3D-Ni foam facilitates the directional growth, exposing more active sites of the catalyst for electrochemical reactions at the electrode–electrolyte interface. The binder-free, self-made NiCo2S4 NW/NF electrode delivers a hydrogen production current density of 10 mA cm–2 at an overpotential of 260 mV for the oxygen evolution reaction and at 210 mV (versus a reversible hydrogen electrode) for the hydrogen evolution reaction in 1 m KOH. This highly active and stable bifunctional electrocatalyst enables the preparation of an alkaline water electrolyzer that could deliver 10 mA cm–2 under a cell voltage of 1.63 V. Because the nonprecious-metal NiCo2S4 NW/NF foam-based electrodes afford the vigorous and continuous evolution of both H2 and O2 at 1.68 V, generated using a solar panel, they appear to be promising water splitting devices for large-scale solar-to-hydrogen generation.
1,152 citations
TL;DR: An exponentially increasing trend of SUHI research since 2005, with clear preferences for geographic areas, time of day, seasons, research foci, and platforms/sensors is found, and key potential directions and opportunities for future efforts are proposed.
Abstract: The surface urban heat island (SUHI), which represents the difference of land surface temperature (LST) in urban relativity to neighboring non-urban surfaces, is usually measured using satellite LST data. Over the last few decades, advancements of remote sensing along with spatial science have considerably increased the number and quality of SUHI studies that form the major body of the urban heat island (UHI) literature. This paper provides a systematic review of satellite-based SUHI studies, from their origin in 1972 to the present. We find an exponentially increasing trend of SUHI research since 2005, with clear preferences for geographic areas, time of day, seasons, research foci, and platforms/sensors. The most frequently studied region and time period of research are China and summer daytime, respectively. Nearly two-thirds of the studies focus on the SUHI/LST variability at a local scale. The Landsat Thematic Mapper (TM)/Enhanced Thematic Mapper (ETM+)/Thermal Infrared Sensor (TIRS) and Terra/Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) are the two most commonly-used satellite sensors and account for about 78% of the total publications. We systematically reviewed the main satellite/sensors, methods, key findings, and challenges of the SUHI research. Previous studies confirm that the large spatial (local to global scales) and temporal (diurnal, seasonal, and inter-annual) variations of SUHI are contributed by a variety of factors such as impervious surface area, vegetation cover, landscape structure, albedo, and climate. However, applications of SUHI research are largely impeded by a series of data and methodological limitations. Lastly, we propose key potential directions and opportunities for future efforts. Besides improving the quality and quantity of LST data, more attention should be focused on understudied regions/cities, methods to examine SUHI intensity, inter-annual variability and long-term trends of SUHI, scaling issues of SUHI, the relationship between surface and subsurface UHIs, and the integration of remote sensing with field observations and numeric modeling.
443 citations
TL;DR: The occurrence and distribution of microbes that are involved in the degradation of both natural and synthetic polymers are described and it seems that biological agents and their metabolic enzymes can be exploited as a potent tool for polymer degradation.
Abstract: Inertness and the indiscriminate use of synthetic polymers leading to increased land and water pollution are of great concern. Plastic is the most useful synthetic polymer, employed in wide range of applications viz. the packaging industries, agriculture, household practices, etc. Unpredicted use of synthetic polymers is leading towards the accumulation of increased solid waste in the natural environment. This affects the natural system and creates various environmental hazards. Plastics are seen as an environmental threat because they are difficult to degrade. This review describes the occurrence and distribution of microbes that are involved in the degradation of both natural and synthetic polymers. Much interest is generated by the degradation of existing plastics using microorganisms. It seems that biological agents and their metabolic enzymes can be exploited as a potent tool for polymer degradation. Bacterial and fungal species are the most abundant biological agents found in nature and have distinct degradation abilities for natural and synthetic polymers. Among the huge microbial population associated with polymer degradation, Pseudomonas aeruginosa, Pseudomonas stutzeri, Streptomyces badius, Streptomyces setonii, Rhodococcus ruber, Comamonas acidovorans, Clostridium thermocellum and Butyrivibrio fibrisolvens are the dominant bacterial species. Similarly, Aspergillus niger, Aspergillus flavus, Fusarium lini, Pycnoporus cinnabarinus and Mucor rouxii are prevalent fungal species.
435 citations
TL;DR: In this article, the effect factors including adsorbent dosage, contact time, pH, temperature on the adsorption properties of methylene blue (MB) from aqueous solution onto sludge-derived biochar were investigated in batch experiments.
Abstract: In this study, biochar was produced from municipal sludge and was characterized by Surface area and porosity analysis, Scanning Electron Microscope–Energy Dispersive Spectrometer (SEM-EDS) and Fourier Transform Infrared Spectroscopy (FTIR). The effect factors including adsorbent dosage, contact time, pH, temperature on the adsorption properties of methylene blue (MB) from aqueous solution onto sludge-derived biochar were investigated in batch experiments. The adsorption kinetics, isotherm, thermodynamic and mechanism were also studied. The results showed that the adsorption kinetics of MB on biochar was accurately described by a pseudo-second-order model, indicating that liquid film diffusion, intra-particle diffusion and surface adsorption coexisted during MB adsorption on the biochar. The equilibrium adsorption data were well represented by the Langmuir isotherm equation (R2 > 0.99). As the initial MB concentration and temperature increased, the adsorption amount also increased and the adsorption was favorable. The thermodynamic analysis showed that MB adsorption onto sludge-derived biochar was spontaneous and endothermic. The desorption and reusability experiment indicated that sludge-derived biochar had the potential to be a reusable adsorbent for MB removal.The adsorption mechanism appeared to be related to electrostatic interaction, ion exchange, hydrogen bond interaction, n-π interaction, etc. Thus, sludge-derived biochar can be used as an effective absorbent to remove dyes from wastewater. As a beneficial by-product of sludge, sludge-derived biochar also can mitigate the environmental burden of sewage sludge.
400 citations
TL;DR: Hybrid nanocomposites based on Cu-BTC MOF, graphene oxide (GO), carbon nanotubes (CNTs), and Fe3O4 magnetic nanoparticles (MNPs) were developed via a simple green solvothermal method as mentioned in this paper.
304 citations
References
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TL;DR: Urban ecology integrates natural and social sciences to study these radically altered local environments and their regional and global effects of an increasingly urbanized world.
Abstract: Urban areas are hot spots that drive environmental change at multiple scales. Material demands of production and human consumption alter land use and cover, biodiversity, and hydrosystems locally to regionally, and urban waste discharge affects local to global biogeochemical cycles and climate. For urbanites, however, global environmental changes are swamped by dramatic changes in the local environment. Urban ecology integrates natural and social sciences to study these radically altered local environments and their regional and global effects. Cities themselves present both the problems and solutions to sustainability challenges of an increasingly urbanized world.
5,096 citations
3,443 citations
TL;DR: In this article, the authors reviewed progress in urban climatology over the two decades since the first publication of the International Journal of Climatology (IJC) and highlighted the role of scale, heterogeneity, dynamic source areas for turbulent fluxes and the complexity introduced by the roughness sublayer over the tall, rigid roughness elements of cities.
Abstract: Progress in urban climatology over the two decades since the first publication of the International Journal of Climatology is reviewed. It is emphasized that urban climatology during this period has benefited from conceptual advances made in microclimatology and boundary-layer climatology in general. The role of scale, heterogeneity, dynamic source areas for turbulent fluxes and the complexity introduced by the roughness sublayer over the tall, rigid roughness elements of cities is described. The diversity of urban heat islands, depending on the medium sensed and the sensing technique, is explained. The review focuses on two areas within urban climatology. First, it assesses advances in the study of selected urban climatic processes relating to urban atmospheric turbulence (including surface roughness) and exchange processes for energy and water, at scales of consideration ranging from individual facets of the urban environment, through streets and city blocks to neighbourhoods. Second, it explores the literature on the urban temperature field. The state of knowledge about urban heat islands around 1980 is described and work since then is assessed in terms of similarities to and contrasts with that situation. Finally, the main advances are summarized and recommendations for urban climate work in the future are made. Copyright © 2003 Royal Meteorological Society.
2,723 citations
TL;DR: S spatially explicit probabilistic forecasts of global urban land-cover change are developed and the direct impacts on biodiversity hotspots and tropical carbon biomass are explored to minimize global biodiversity and vegetation carbon losses.
Abstract: Urban land-cover change threatens biodiversity and affects ecosystem productivity through loss of habitat, biomass, and carbon storage. However, despite projections that world urban populations will increase to nearly 5 billion by 2030, little is known about future locations, magnitudes, and rates of urban expansion. Here we develop spatially explicit probabilistic forecasts of global urban land-cover change and explore the direct impacts on biodiversity hotspots and tropical carbon biomass. If current trends in population density continue and all areas with high probabilities of urban expansion undergo change, then by 2030, urban land cover will increase by 1.2 million km2, nearly tripling the global urban land area circa 2000. This increase would result in considerable loss of habitats in key biodiversity hotspots, with the highest rates of forecasted urban growth to take place in regions that were relatively undisturbed by urban development in 2000: the Eastern Afromontane, the Guinean Forests of West Africa, and the Western Ghats and Sri Lanka hotspots. Within the pan-tropics, loss in vegetation biomass from areas with high probability of urban expansion is estimated to be 1.38 PgC (0.05 PgC yr−1), equal to ∼5% of emissions from tropical deforestation and land-use change. Although urbanization is often considered a local issue, the aggregate global impacts of projected urban expansion will require significant policy changes to affect future growth trajectories to minimize global biodiversity and vegetation carbon losses.
2,681 citations
TL;DR: The growing evidence that climate–health relationships pose increasing health risks under future projections of climate change is reviewed and that the warming trend over recent decades has already contributed to increased morbidity and mortality in many regions of the world.
Abstract: The World Health Organisation estimates that the warming and precipitation trends due to anthropogenic climate change of the past 30 years already claim over 150,000 lives annually. Many prevalent human diseases are linked to climate fluctuations, from cardiovascular mortality and respiratory illnesses due to heatwaves, to altered transmission of infectious diseases and malnutrition from crop failures. Uncertainty remains in attributing the expansion or resurgence of diseases to climate change, owing to lack of long-term, high-quality data sets as well as the large influence of socio-economic factors and changes in immunity and drug resistance. Here we review the growing evidence that climate-health relationships pose increasing health risks under future projections of climate change and that the warming trend over recent decades has already contributed to increased morbidity and mortality in many regions of the world. Potentially vulnerable regions include the temperate latitudes, which are projected to warm disproportionately, the regions around the Pacific and Indian oceans that are currently subjected to large rainfall variability due to the El Nino/Southern Oscillation sub-Saharan Africa and sprawling cities where the urban heat island effect could intensify extreme climatic events.
2,552 citations