Reflections about three influential Ambio articles impacting environmental biogeochemistry research and knowledge: This article belongs to Ambio’s 50th Anniversary Collection. Theme: Environmental contaminants

Reflections about three influential environmental contaminants papers published in Ambio are presented. The PCB Story by Jensen in (1972) had a very important influence on environmental chemistry. This is captured by way of comments and personal anecdotes. Wania’s and MacKay’s (1993) paper highlights the physical chemistry underlying transport of PCBs and organochlorine pesticides from temperate zone ecosystems to Polar Regions. Their paper exemplifies how principles of chemistry and environmental processes informed understanding the biogeochemical cycles of chemicals of environmental concern (CEC). Mergler et al.’s (2007) paper reviews knowledge of methyl mercury exposure and impacts in humans and served as an example of how to approach exposure and human health concerns for all CECs. All great progress. Then, the question: “How we missed for two decades the importance of plastics in the environment identified in a paper published the same year as The PCB Story? Are we missing yet another important environmental contaminant now?     

Empirical Relationships between Observed Ozone Concentrations and Geographical Areas with Concentrations Likely to Be above 120 ppb

The extent to which existing ozone monitoring data can be used to represent concentrations outside the area immediately surrounding a monitoring station is investigated. The results should be of Interest to those who wish to define areas within which standards are likely to have been exceeded. Relationships are established between the observed second-maximum hour-average ozone concentrations and the area within which It is possible to state with reasonable probability that National Ambient Air Quality Standards (NAAQS) have or have not been exceeded. All pairs of SAROAD stations (Storage and Retrieval of Aerometric Data) separated by 500 km or less which had nearly complete annual data sets were considered for the years 1974 through 1977 to determine the probability that the NAAQS would be exceeded at one station of the pair, given station separation and the observed second-maximum hourly ozone concentration at the other station. The resulting relationship was applied to SAROAD data for 1977, and circles were drawn around each SAROAD monitoring site to show the area within which it is 90% probable that the 120 ppb NAAQS was exceeded during 1977.     

Urban sustainability science: prospects for innovations through a system’s perspective,relational and transformations’ approaches: This article belongs to Ambio’s 50th Anniversary Collection. Theme: Urbanization

In this perspective, we present how three initial landmark papers on urban sustainability research contributed to the larger sustainability science scholarship and paved the way for the continued development of urban sustainability research. Based on this, we propose three conceptual innovation pathways to trace the progression of urban sustainability science: First, urban sustainability from a system’s perspective, meaning that urban sustainability requires integrative solutions to work in the tripled social-ecological-technological system setting. Second, urban sustainability from a (people and place) relational perspective, meaning urban sustainability is a contested and dynamic social-ecological contract of cities. As a governance mission, urban sustainability requires evidence from research that can inform coordinated action to bridge people, places, meanings, visions and ecosystems. Third, urban sustainability from a transformative science perspective, meaning that for urban sustainability to be achieved and progressed, deep transformations are required in systems, relations, policies and governance approaches. Our proposal for the future of urban sustainability science centres on emphasizing the relevance and policy applicability of systems’ thinking, value and place thinking and transitions/transformations thinking as fundamental to how knowledge is co-produced by research science, policy and society and becomes actionable.     

The far to equilibrium time evolution of the ozone layer: steady-state and critical behaviour

The ozone layer stability in the far equilibrium conditions was studied in the framework of the irreversible thermodynamics. Following the Prigogine's procedures concerning the Brusselator model, the phenomenological model of the ozone layer leads to a system of non-linear differential equations. The steady-state solution of the system outlines the fact that the ozone layer can reach a steady state in the far equilibrium conditions for any pollutant concentration values. Applying the Lyapounov's theorem of stability, it is demonstrated that all the steady-state solutions for the ozone layer are stable ones. The natural limit of the ozone concentration is calculated, as well as that of the pollutant concentrations (the upper limits). This procedure suggests a way of assessing the effect of the anthropogenetic activities. The transmission coefficients of the UV radiation are calculated establishing the lower limits of the “permitting” pollution. The error analysis shows that the prediction of the stability of the steady state of the ozone layer does not depend on the errors of the input data.     

The pika and the watershed: The impact of small mammal poisoning on the ecohydrology of the Qinghai-Tibetan Plateau

With approximately 20 % of the world’s population living in its downstream watersheds, the Qinghai-Tibetan Plateau (QTP) is considered “Asia’s Water Tower.” However, grasslands of the QTP, where most of Asia’s great rivers originate, are becoming increasingly degraded, which leads to elevated population densities of a native small mammal, the plateau pika (Ochotona curzoniae). As a result pikas have been characterized as a pest leading to wide-spread poisoning campaigns in an attempt to restore grassland quality. A contrary view is that pikas are a keystone species for biodiversity and that their burrowing activity provides a critical ecosystem service by increasing the infiltration rate of water, hence reducing overland flow. We demonstrate that poisoning plateau pikas significantly reduces infiltration rate of water across the QTP creating the potential for watershed-level impacts. Our results demonstrate the importance of burrowing mammals as ecosystem engineers, particularly with regard to their influence on hydrological functioning.     

Production of boundary layer ozone from tropical American Savannah biomass burning emissions

Boundary layer ozone and carbon monoxide were measured at a savannah site in the Orinoco river basin, during the dry and wet seasons. CO and O₃ concentrations recorded around noontime show a good linear correlation, suggesting that the higher ozone levels observed during the dry season are photochemically produced during the oxidation of reactive hydrocarbons in the presence of NO_x both emitted by biomass burning. The rate of photochemical ozone production in the boundary layer ozone by biomass burning calculated from the production ratio ΔO₃/ΔCO (0.17±0.01 v : v) and the amount of CO produced by fires (0.26–1.3 mole m⁻² dry season⁻¹), ranges from 0.6 to 2.6 ppbv h⁻¹ for 8 h of daylight. This O₃ production rate is in fairly good agreement with the value derived from RO₂ radical measurements made in the Venezuelan savannah during the dry season. The net boundary layer production of O₃ from all tropical America savannah fires is estimated to range between 0.28 and 0.36 Tmol O₃ per year, which is about 3 times higher than the O₃ produced from pollution sources in the eastern United States during the summer. An extrapolation to all of the world's savannah would indicate a net boundary layer ozone production of about 1.2 Tmol yr⁻¹. This is discussed in the context of the overall global budget of tropospheric ozone.     

Usage,definition, and measurement of coexistence,tolerance and acceptance in wildlife conservation research in Africa

The terms ‘coexistence’, ‘tolerance,’ and ‘acceptance’ appear frequently in conservation literature, but lack consistent characterization, making them difficult to apply across intervention frameworks. This review aims to describe the common characterizations of these three terms using Africa-based research as a case study. Through systematic lexical searches, we identified 392 papers containing one or more of the three terms. We assessed their usage, definition, and measurement (or lack thereof) in wildlife conservation. Coexistence was used in 46% of papers, but was defined in only 2% and measured in 4%. Tolerance and acceptance were used in 63% and 61% of the papers in which they appeared, respectively, defined in 4% and 2%, and measured in 19% and 5%. These results confirm the lack of clear understanding of these concepts and evidence the need for a precise lexicon. This would allow conservationists to cohesively describe their work and increase replicability of research across contexts.Electronic supplementary materialThe online version of this article (10.1007/s13280-020-01352-6) contains supplementary material, which is available to authorized users.     

The emergence of land systems as the nexus for sustainability transformations: This article belongs to Ambio's 50th Anniversary Collection. Theme: Agriculture land use

This perspective recognizes the seminal Ambio articles of Sombroek et al. (1993), Turner et al. (1994) and Brussaard et al. (1997), identifying their individual and collective role in laying the ground work for a global change research agenda on land and its human use through increased understanding of terrestrial ecosystem dynamics and global change, and furthering nascent interdisciplinary efforts within the global change science community to better understand the ‘human driving forces’ of change. From these efforts, land system science, as a systemic science focused on complex socio-ecological interactions around land use and associated trade-offs and synergies, emerges as an ‘interdiscipline’ challenged to better understand land systems as the ‘meeting ground’ for multiple claims on land for biodiversity, carbon, livelihoods, food production among others, and support pathways to sustainability for people and nature.     

Atmospheric oxidation capacity in the summer of Houston 2006: Comparison with summer measurements in other metropolitan studies

Both similarities and differences in summertime atmospheric photochemical oxidation appear in the comparison of four field studies: TEXAQS2000 (Houston, 2000), NYC2001 (New York City, 2001), MCMA2003 (Mexico City, 2003), and TRAMP2006 (Houston, 2006). The compared photochemical indicators are OH and HO₂ abundances, OH reactivity (the inverse of the OH lifetime), HO_x budget, OH chain length (ratio of OH cycling to OH loss), calculated ozone production, and ozone sensitivity. In terms of photochemical activity, Houston is much more like Mexico City than New York City. These relationships result from the ratio of volatile organic compounds (VOCs) to nitrogen oxides (NO_x), which are comparable in Houston and Mexico City, but much lower in New York City. Compared to New York City, Houston and Mexico City also have higher levels of OH and HO₂, longer OH chain lengths, a smaller contribution of reactions with NO_x to the OH reactivity, and NO_x-sensitivity for ozone production during the day. In all four studies, the photolysis of nitrous acid (HONO) and formaldehyde (HCHO) are significant, if not dominant, HO_x sources. A problematic result in all four studies is the greater OH production than OH loss during morning rush hour, even though OH production and loss are expected to always be in balance because of the short OH lifetime. The cause of this discrepancy is not understood, but may be related to the under-predicted HO₂ in high NO_x conditions, which could have implications for ozone production. Three photochemical indicators show particularly high photochemical activity in Houston during the TRAMP2006 study: the long portion of the day for which ozone production was NO_x-sensitive, the calculated ozone production rate that was second only to Mexico City's, and the OH chain length that was twice that of any other location. These results on photochemical activity provide additional support for regulatory actions to reduce reactive VOCs in Houston in order to reduce ozone and other pollutants.     

Stratospheric Ozone Protection: An EPA Engineering Perspective

Chlorine released into the atmosphere is a major factor in the depletion of the protective stratospheric ozone layer. The Montreal Protocol, as amended in 1990, and the Clean Air Act Amendments of 1990, address the limits and reduction schedules to be placed on chlorine- and bromine-containing chemicals. The status of technical solutions to the problem of chlorofluorocarbons, halons, methyl chloroform, and carbon tetrachloride in the major use areas of refrigeration, foam, aerosols, fire protection, and solvents is discussed here. The discussion includes the cooperative efforts involving academia, industry, U.S. governmental organizations, and other nations who are contributing solutions to these problems.     

Ground-based remote sensing measurements of aerosol and ozone in an urban area: A case study of mixing height evolution and its effect on ground-level ozone concentrations

We have estimated the mixing height (MH) and investigated the relationship between vertical mixing and ground-level ozone concentrations in Seoul, Korea, by using three ground-based active remote sensing instruments operating side by side: micro-pulse lidar (MPL), differential absorption lidar (DIAL), and differential optical absorption spectroscopy (DOAS). The MH is estimated from MPL measurements of aerosol extinction profiles by the gradient method under convective conditions. Comparisons of the MHs estimated from MPL and radiosonde measurements show a good agreement (r²=0.99). Continuous MPL measurements with high temporal and vertical resolution reveal the diurnal variations of the MH under convective conditions and the presence of a residual layer during the nighttime. Comprehensive measurements of ozone and aerosol by MPL, DIAL and DOAS during an high ozone episode (24–26 May 2000) in Seoul, Korea, reveal that (1) photochemical ozone production and advection from upwind regions (the western part of Seoul) contribute two peaks of ozone concentrations at the ground around 14:00 and 18:00 local time on 25 May 2000, respectively, and (2) the entrainment and the fumigation processes of ozone aloft in the nighttime residual layer into the ground is a major contributor of high concentrations of ground-level ozone observed on the following day (26 May 2000).     

Disruption of the global nitrogen cycle: A grand challenge for the twenty-first century: This article belongs to Ambio’s 50th Anniversary Collection. Theme: Eutrophication

Disruption of the global nitrogen cycle by humans results primarily from activities associated with food and energy production. Since the middle of the twentieth century, human activities have more than doubled inputs of nitrogen to the Earth’s ecosystems. This new nitrogen is in chemically and biologically active forms (reactive N) and moves through the environment causing an array of health and environmental problems. Research published in Ambio for the past three decades has been documenting this major global-scale problem and has catalyzed the formation of a science-led initiative, the International Nitrogen Initiative (INI), which has informed policies to manage the global nitrogen cycle. Currently, gaps and opportunities in nitrogen pollution policies still exist and require new interdisciplinary science to help to place the nitrogen management challenge in the context of the other environmental grand challenges of our time including climate change and biodiversity loss because their solutions will be interconnected.     

Assessing the contribution of mobility in the European Union to rubber expansion

Nearly three-quarters of global natural rubber production is used to produce tyres, supporting mobility around the globe. The projected increase in mobility could contribute to further expansion of rubber plantations and impact tropical ecosystems. We quantified the use of natural rubber in tyres in the European Union (EU), the corresponding land footprint, and explored drivers of tyre use using country-specific transport statistics and trade registers of rubber goods. Five percent of the world’s natural rubber is consumed in tyres used in the EU, using up to a quarter of the area under rubber plantations in some producing countries. Car use is responsible for 58% of this consumption, due to car-dependent lifestyles that are associated with economic prosperity and spatial planning paradigms. While the EU’s transport policy focuses on reducing dependence on fossil-fuels, cross-cutting policies are needed to address car-dependency and reduce the EU’s land footprint in tropical landscapes without compromising progress towards decarbonisation.Supplementary InformationThe online version contains supplementary material available at 10.1007/s13280-021-01579-x.     

Closing Remarks

Considerable attention has been paid in recent years to photochemical smog pollution close to the earth's surface and to stratospheric ozone depletion. There is reason to suspect that the next round of scientific concern will be devoted to the perturbations in the “free troposphere.” Tropospheric ozone has been building up in many regions of the northern hemisphere. Ozone changes in the upper troposphere will exert a considerable impact on global warming. This could affect moisture levels, cloud amount and distribution, precipitation, and atmospheric dynamics on different scales.

This paper analyzes: (1) the physical and chemical processes contributing to changes in tropospheric ozone concentration; (2) the observational evidence of previous ozone change; and (3) results drawn from computer modelling of past and future radiative forcing caused by rising ozone concentrations in the upper troposphere.

The solar and longwave radiative model developed by Wang et al. (1991) was used for calculating the change in radiative forcing to the troposphere-surface system that can be ascribed to changing concentrations in ozone and other greenhouse gases. Nitric oxide emission from aircraft are a prime suspect for the observed increases in upper tropospheric ozone. The inference can be drawn that a radiative forcing of 0.2 to 0.35 Wm^-2 will result from a doubling of aircraft emissions over the next two decades. This will amount to 10 to 25 percent of the radiative forcing attributable to CO₂ alone for the same period. The effect of doubling aircraft emissions will increase as stratospheric ozone concentrations recover from the recent buildup of harmful chlorofluorocarbons. A large fraction of the radiative forcing that occurred during the 1970 to 1990 period can be attributed to increases in tropospheric ozone as opposed to increases in other greenhouse gases.     

The influence of south foehn on the ozone mixing ratios at the high alpine site Arosa

Within 2 years of trace gas measurements performed at Arosa (Switzerland, 2030 m above sea level), enhanced ozone mixing ratios were observed during south foehn events during summer and spring (5–10 ppb above the median value). The enhancements can be traced back to ozone produced in the strongly industrialized Po basin as confirmed by various analyses. Backward trajectories clearly show advection from this region during foehn. NO_y versus O₃ correlation and comparison of O₃ mixing ratios between Arosa and Mt. Cimone (Italy, 2165 m asl) suggest that ozone is the result of recent photochemical production (+5.6 ppb on average), either directly formed during the transport or via mixing of air processed in the Po basin boundary layer. The absence of a correlation between air parcel residence times over Europe and ozone mixing ratios at Arosa during foehn events is in contrast to a previous analysis, which suggested such correlation without reference to the origin of the air. In the case of south foehn, the continental scale influence of pollutants emission on ozone at Arosa appears to be far less important than the direct influence of the Po basin emissions. In contrast, winter time displays a different situation, with mean ozone reductions of about 4 ppb for air parcels passing the Po basin, probably caused by mixing with ozone-poor air from the Po basin boundary layer.     

Ground-level ozone and ozone vertical profile measurements close to the foothills of the Guadarrama mountain range (Spain)

Continuous measurements of ozone vertical profiles, OVP, in the low troposphere (around 500–2400 m) using an unattended commercial ozone profiler DIAL, were conducted during June–July 2004 in Segovia, SG, a small city in the upper plateau located close to the foothills of the Guadarrama mountain range, Guadarrama, in the Central Massif. The data obtained over almost 37 complete days have enabled us to characterise the ozone vertical exchange, describe the phenomenology of the main ozone peaks, OP, recorded in the city and their relationship with ozone transport/formation from the gas precursor emissions of the greater Madrid area across Guadarrama. To achieve the last objective concurrent measurements of ground-level ozone in SG and a representative monitoring station upwind from Guadarrama, Buitrago de Lozoya, BL, have been used. 72.2% of the concurrent maximum diurnal ozone peaks exceeding the 95 percentile hourly value in SG (OPSG) and BL (OPBL) were linked to ozone transport and formation from the greater Madrid area towards Guadarrama. An estimate of the contribution of the greater Madrid area on OPSG yielded 28 μg m⁻³.The most prominent ozone vertical stratification was linked to the mixing height, MH, and a frequent nocturnal stable layer formed, NSL. Three small ozone enriched-layers were identified at mean heights of 500, 700 and 1000 m, respectively. Ozone tended to decline versus altitude. The hourly patterns of the three layers showed two peak occurrences of similar amplitude in the early morning, 7–8 h, and mid-afternoon, 14–16 h. A minimum was also observed during daytime, 10–11 h, its origin being attributed to a dilution process induced by the “chimney effect” caused by the slopes heating during this period.The comparison between OPSG, and the maximum diurnal ozone peaks in the first layer, OL1P, showed a satisfactory relationship, correlation coefficient, r, of the linear fit 0.77, and comparable mean values, 127 and 130 μg m⁻³, respectively, revealing the presence of an uniform ozone vertical distribution in the 500 m atmospheric layer above ground level during mid-afternoon.     

Chemistry and aerosols in the marine boundary layer: 1-D modelling of the three ACE-2 Lagrangian experiments

Three Lagrangian experiments were conducted during IGAC's second aerosol characterization experiment (ACE-2) in the area between Portugal, Tenerife and Madeira in June/July 1997. During each Lagrangian experiment, a boundary layer air mass was followed for about 30 h, and the temporal evolution of its chemical and aerosol composition was documented by a series of vertical profiles and horizontal box pattern flown by the Meteorological Research Flight research aircraft Hercules C130. The wealth of observational data that has been collected during these three Lagrangian experiments is the basis for the development and testing of a one-dimensional Lagrangian boundary layer model with coupled gas, aqueous, and aerosol phase chemistry. The focus of this paper is on current model limitations and strengths. We show that the model is able to represent the dynamical and chemical evolution of the marine boundary layer, in some cases requiring adjustments of the subsidence velocity and of the surface heat fluxes. Entrainment of a layer rich in ozone and carbon monoxide from a residual continental boundary layer into the marine boundary layer as well as in-cloud oxidation of sulphur dioxide by hydrogen peroxide are simulated, and coherent results are obtained, concerning the evolution of the small, presumably sulphate–ammonia aerosol mode.     

The forest environmental frontier in Russia: Between sustainable forest management discourses and ‘wood mining’ practice

With 20% of the world’s forests, Russia has global potential in bioeconomy development, biodiversity conservation and climate change mitigation. However, unsustainable forest management based on ‘wood mining’ reduces this potential. Based on document analysis, participant observations and interviews, this article shows how non-state actors—environmental NGOs and forest companies—address forest resource depletion and primary forest loss in Russia. We analyse two key interrelated forest discourses driven by non-state actors in Russia: (1) intensive forest management in secondary forests as a pathway towards sustained yield and primary forest conservation; (2) intact forest landscapes as a priority in primary forest conservation. We illustrate how these discourses have been integrated into policy debates, institutions and practices and discuss their relation to relevant global discourses. The article concludes that despite successful cases in conserving intact forest landscapes, there is still a frontier between sustainable forest management discourses and forestry practice in Russia.Supplementary InformationThe online version contains supplementary material available at 10.1007/s13280-021-01643-6.     

Long term changes in nitrogen oxides and volatile organic compounds in Toronto and the challenges facing local ozone control

Ground level ozone represents a significant air quality concern in Toronto, Canada, where the national 65 ppb 8-h standard is repeatedly exceeded during the summer. Here we present an analysis of nitrogen dioxide (NO₂), ozone (O₃), and volatile organic compound (VOC) data from federal and provincial governmental monitoring sites from 2000 to 2007. We show that summertime VOC reactivity and ambient concentrations of NO₂ have decreased over this period of time by up to 40% across Toronto and the surrounding region. This has not resulted in significant summertime ozone reductions, and in some urban areas, it appears to be increasing. We discuss the competing effects of decreased ozone titration leading to an increase in O₃, and decreased local ozone production, both caused by significant decreases in NO_x concentrations. In addition, by using local meteorological data, we show that annual variability in summer ozone correlates strongly with maximum daily temperatures, and we explore the effect of atmospheric transport from the southwest which has a significant influence on early morning levels before local production begins. A mathematical model of instantaneous ozone production is presented which suggests that, given the observed decreases in NO_x and VOC reactivity, we would not expect a significant change in local ozone production under photochemically relevant conditions. These results are discussed in the context of Toronto's recent commitment to cutting local smog-causing pollutants by 20% by 2012.     

Cities and the SDGs: Realities and possibilities of local engagement in global frameworks

City action is critical to achieving global visions for sustainability such as the UN’s Sustainable Development Goals (SDGs). However, SDG ‘localisation’ is complex procedure, with divergent outcomes depending on context and diverse city processes. This paper considers the operational challenges faced by city actors in taking on the SDGs, and subsequent implications for initiating local (and global) sustainability transitions. We analyse emergent approaches to SDG localisation within the Asia–Pacific, using a policy analysis framework (transition management) to assess transformation potential. We find that SDG localisation can influence urban sustainability, but effective implementation requires sufficient data, resourcing, and guidance—which are not readily, nor equally available to all city governments. City-to-city peer learning can accelerate SDG uptake, but realising the transformative ambition set out by the SDGs will require an approach to localisation that clearly demonstrates why and how any city government can and should engage with global sustainability frameworks.