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Abstract The optimized green-grey infrastructures are promising solutions to combat the urban flood and water quality problems which have been severe owe to the increasing urbanization and climate change. However, the focusses in existing researches have been either on finding the best strategy by scenario analysis method or optimal design of LID practices under the hypothesis of unchanged grey infrastructures. Little is known regarding the synergistic effect of synchronous optimization design of both green and grey infrastructures. In the study, we conduct green-grey infrastructures synchronous optimization by modifying the decision variables of traditional simulation-optimization frameworks and investigate how external uncertainties will affect their performance. The methodology was applied to a case study in Suzhou, China. The results showed that although the cost of green-grey synchronous optimized scenarios is lower than that of green optimized only scenarios by 1.69–4.19 thousand USD per km2, the runoff/pollutants reductions of green-grey synchronous optimized scenarios are 0.11%–5.24% higher than that of green optimized only scenarios. In the green-grey synchronous optimized scenarios, green infrastructures can contribute to runoff/pollutants control by 50%–63%/62%–70%, while grey infrastructures can contribute to the remaining part by 37%–50%/30%–38%.

Abstract Typical continental, cold climate conditions were applied to four large, laboratory columns to simulate temperatures ranging from −20 to +20 °C over summer, winter, and spring runoff. The goal of this research was to assess the seasonal effectiveness of bioretention application in cold climate regions that are currently experiencing the impacts of climate change. 1.6 years’ worth of equivalent Edmonton precipitation volume was applied over a 10-month period to evaluate the water quality improvement through two soil types (i.e., loam and sandy loam) with and without amendments intended to enhance nutrient removal. During summer, excellent removal of total suspended solids (TSS), phosphate, and ammonium (i.e., ≥90% average concentration reduction) was observed in both the loam and sandy loam columns without the nutrient removal amendments. The columns containing the amendments also reduced TSS, ammonium, and phosphate, but not as effective as the non-amended columns for TSS and ammonium. During winter and spring runoff, if infiltration occurs, physical removal of TSS, phosphate, and ammonium was still achieved, only days after the complete freezing (and subsequent thawing) of bioretention media at −20 °C. After an initial maturation and leaching period, nitrate was well removed (≥65.2% average concentration reduction) via denitrification in the columns with the nutrient removal amendments and submerged zone.

Our future is urban. With more than two-thirds of the global population expected to live in cities by 2050, urban sustainability is an essential part of sustainable development but remains poorly understood for urban agglomerations, which continue to develop and grow. Here, we construct a multiregional input-output table at the city level and investigate the impacts of water and carbon flows on the intercity supply chain of the Beijing-Tianjin-Hebei agglomeration in 2012. Our analysis reveals an economic-environmental imbalance whereby Beijing and Tianjin prosper at the expense of Hebei cities. Hebei cities work as producers for Beijing and Tianjin, such that services and goods exported from the Hebei region account for more than 60% of the region's carbon emissions and water use. Economic benefits are also exported. In the case of five key Hebei cities, only 38% of the region's gross domestic product is retained within the cities. This disparity has important implications for equality, prosperity, and sustainability and demonstrates the importance of considering supply chains from the city networks perspective.

Abstract. Accurate assessment of anthropogenic carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere – the “global carbon budget” – is important to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe data sets and methodology to quantify the five major components of the global carbon budget and their uncertainties. Fossil CO2 emissions (EFF) are based on energy statistics and cement production data, while emissions from land use and land-use change (ELUC), mainly deforestation, are based on land use and land-use change data and bookkeeping models. Atmospheric CO2 concentration is measured directly and its growth rate (GATM) is computed from the annual changes in concentration. The ocean CO2 sink (SOCEAN) and terrestrial CO2 sink (SLAND) are estimated with global process models constrained by observations. The resulting carbon budget imbalance (BIM), the difference between the estimated total emissions and the estimated changes in the atmosphere, ocean, and terrestrial biosphere, is a measure of imperfect data and understanding of the contemporary carbon cycle. All uncertainties are reported as ±1σ. For the last decade available (2008–2017), EFF was 9.4±0.5 GtC yr−1, ELUC 1.5±0.7 GtC yr−1, GATM 4.7±0.02 GtC yr−1, SOCEAN 2.4±0.5 GtC yr−1, and SLAND 3.2±0.8 GtC yr−1, with a budget imbalance BIM of 0.5 GtC yr−1 indicating overestimated emissions and/or underestimated sinks. For the year 2017 alone, the growth in EFF was about 1.6 % and emissions increased to 9.9±0.5 GtC yr−1. Also for 2017, ELUC was 1.4±0.7 GtC yr−1, GATM was 4.6±0.2 GtC yr−1, SOCEAN was 2.5±0.5 GtC yr−1, and SLAND was 3.8±0.8 GtC yr−1, with a BIM of 0.3 GtC. The global atmospheric CO2 concentration reached 405.0±0.1 ppm averaged over 2017. For 2018, preliminary data for the first 6–9 months indicate a renewed growth in EFF of +2.7 % (range of 1.8 % to 3.7 %) based on national emission projections for China, the US, the EU, and India and projections of gross domestic product corrected for recent changes in the carbon intensity of the economy for the rest of the world. The analysis presented here shows that the mean and trend in the five components of the global carbon budget are consistently estimated over the period of 1959–2017, but discrepancies of up to 1 GtC yr−1 persist for the representation of semi-decadal variability in CO2 fluxes. A detailed comparison among individual estimates and the introduction of a broad range of observations show (1) no consensus in the mean and trend in land-use change emissions, (2) a persistent low agreement among the different methods on the magnitude of the land CO2 flux in the northern extra-tropics, and (3) an apparent underestimation of the CO2 variability by ocean models, originating outside the tropics. This living data update documents changes in the methods and data sets used in this new global carbon budget and the progress in understanding the global carbon cycle compared with previous publications of this data set (Le Quéré et al., 2018, 2016, 2015a, b, 2014, 2013). All results presented here can be downloaded from https://doi.org/10.18160/GCP-2018.

AbstractEngineered biochars are promising candidates in a wide range of environmental applications, including soil fertility improvement, contaminant immobilization, wastewater treatment and in situ carbon sequestration. This review provides a systematic classification of these novel biochar composites and identifies the promising future trends in composite research and application. It is proposed that metals, minerals, layered double hydroxides, carbonaceous nanomaterials and microorganisms enhance the performances of biochars via distinct mechanisms. In this review, four novel trends are identified and assessed critically. Firstly, facile synthesis methods, in particular ball milling and co‐pyrolysis, have emerged as popular composite fabrication strategies that are suitable for large‐scale applications. Secondly, biochar modification with green materials, such as natural clay minerals and microorganisms, align well with the on‐going green and sustainable remediation (GSR) movement. Furthermore, new applications in soil health improvement and climate change mitigation support the realization of United Nation's Sustainable Development Goals (SDGs). Finally, the importance of field studies is getting more attention, since evidence of field success is critically needed before large‐scale applications.