Global food loss and waste embodies unrecognized harms to air quality and biodiversity hotspots.

Global food loss and waste (FLW) undermines the resilience and sustainability of food systems and is closely tied to the United Nation's Sustainable Development Goals on climate, resource use and food security. Here we reveal strong yet under-discussed interconnections between FLW and two other Sustainable Development Goals of Human Health and Life on Land via the nitrogen cycle. We find that eliminating global FLW in 2015 would have reduced anthropogenic NH3 emissions associated with food production by 11.4 Tg (16%), decreased local PM2.5 concentrations by up to 5 µg m-3 and PM2.5-related years of life lost by 1.5 million years, and mitigated nitrogen critical load exceedances in global biodiversity hotspots by up to 19%. Halving FLW in 2030 will reduce years of life lost by 0.5-0.8 million years and nitrogen deposition by 4.7-6.0 Tg N per year (4%) (range for socioeconomic pathways). Complementary to near-term NH3 mitigation potential via technological measures, our study emphasizes incentivizing FLW reduction efforts from air quality and ecosystem health perspectives.

Nitrification, denitrification, and competition for soil N: Evaluation of two Earth System Models against observations.

Earth System Models (ESMs) have implemented nitrogen (N) cycles to account for N limitation on terrestrial carbon uptake. However, representing inputs, losses, and recycling of N in ESMs is challenging. Here, we use global rates and ratios of key soil N fluxes, including nitrification, denitrification, mineralization, leaching, immobilization, and plant uptake (both NH4 + and NO3 - ), from the literature to evaluate the N cycles in the land model components of two ESMs. The two land models evaluated here, E3SM Land Model version 1 (ELMv1)-ECA and CLM5.0, originated from a common model but have diverged in their representation of plant-microbe competition for soil N. The models predict similar global rates of gross primary productivity (GPP) but have approximately two-fold to three-fold differences in their underlying global mineralization, immobilization, plant N uptake, nitrification, and denitrification fluxes. Both models dramatically underestimate the immobilization of NO3 - by soil bacteria compared with literature values and predict dominance of plant uptake by a single form of mineral nitrogen (NO3 - for ELM, with regional exceptions, and NH4 + for CLM5.0). CLM5.0 strongly underestimates the global ratio of gross nitrification:gross mineralization and both models are likely to substantially underestimate the ratio of nitrification:denitrification. Few experimental data exist to evaluate this last ratio, in part because nitrification and denitrification are quantified using different techniques and because denitrification fluxes are difficult to measure at all. More observational constraints on soil nitrogen fluxes such as nitrification and denitrification, as well as greater scrutiny of the functional impact of introducing separate NH4 + and NO3 - pools into ESMs, could help to improve confidence in present and future simulations of N limitation on the carbon cycle.

Nitrification and denitrification in the Community Land Model compared with observations at Hubbard Brook Forest.

Models of terrestrial system dynamics often include nitrogen (N) cycles to better represent N limitations on terrestrial carbon (C) uptake, but simulating the fate of N in ecosystems has proven challenging. Here, key soil N fluxes and flux ratios from the Community Land Model version 5.0 (CLM5.0) are compared with an extensive set of observations from the Hubbard Brook Forest Long-Term Ecological Research site in New Hampshire. Simulated fluxes include microbial immobilization and plant uptake, which compete with nitrification and denitrification, respectively, for available soil ammonium (NH4 + ) and nitrate (NO3 - ). In its default configuration, CLM5.0 predicts that both plant uptake and immobilization are strongly dominated by NH4 + over NO3 - , and that the model ratio of nitrification:denitrification is ~1:1. In contrast, Hubbard Brook observations suggest that NO3 - plays a more significant role in plant uptake and that nitrification could exceed denitrification by an order of magnitude. Modifications to the standard CLM5.0 at Hubbard Brook indicate that a simultaneous increase in the competitiveness of nitrifying microbes for NH4 + and reduction in the competitiveness of denitrifying bacteria for NO3 - are needed to bring soil N flux ratios into better agreement with observations. Such adjustments, combined with evaluation against observations, may help to improve confidence in present and future simulations of N limitation on the C cycle, although C fluxes, such as gross primary productivity and net primary productivity, are less sensitive to the model modifications than soil N fluxes.

Cleaner fuels for ships provide public health benefits with climate tradeoffs.

We evaluate public health and climate impacts of low-sulphur fuels in global shipping. Using high-resolution emissions inventories, integrated atmospheric models, and health risk functions, we assess ship-related PM2.5 pollution impacts in 2020 with and without the use of low-sulphur fuels. Cleaner marine fuels will reduce ship-related premature mortality and morbidity by 34 and 54%, respectively, representing a ~ 2.6% global reduction in PM2.5 cardiovascular and lung cancer deaths and a ~3.6% global reduction in childhood asthma. Despite these reductions, low-sulphur marine fuels will still account for ~250k deaths and ~6.4 M childhood asthma cases annually, and more stringent standards beyond 2020 may provide additional health benefits. Lower sulphur fuels also reduce radiative cooling from ship aerosols by ~80%, equating to a ~3% increase in current estimates of total anthropogenic forcing. Therefore, stronger international shipping policies may need to achieve climate and health targets by jointly reducing greenhouse gases and air pollution.

Mortality due to Vegetation Fire-Originated PM2.5 Exposure in Europe-Assessment for the Years 2005 and 2008.

BACKGROUND: Vegetation fires can release substantial quantities of fine particles (PM2.5), which are harmful to health. The fire smoke may be transported over long distances and can cause adverse health effects over wide areas. OBJECTIVE: We aimed to assess annual mortality attributable to short-term exposures to vegetation fire-originated PM2.5 in different regions of Europe. METHODS: PM2.5 emissions from vegetation fires in Europe in 2005 and 2008 were evaluated based on Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data on fire radiative power. Atmospheric transport of the emissions was modeled using the System for Integrated modeLling of Atmospheric coMposition (SILAM) chemical transport model. Mortality impacts were estimated for 27 European countries based on a) modeled daily PM2.5 concentrations and b) population data, both presented in a 50 × 50 km2 spatial grid; c) an exposure-response function for short-term PM2.5 exposure and daily nonaccidental mortality; and d) country-level data for background mortality risk. RESULTS: In the 27 countries overall, an estimated 1,483 and 1,080 premature deaths were attributable to the vegetation fire-originated PM2.5 in 2005 and 2008, respectively. Estimated impacts were highest in southern and eastern Europe. However, all countries were affected by fire-originated PM2.5, and even the lower concentrations in western and northern Europe contributed substantially (~ 30%) to the overall estimate of attributable mortality. CONCLUSIONS: Our assessment suggests that air pollution caused by PM2.5 released from vegetation fires is a notable risk factor for public health in Europe. Moreover, the risk can be expected to increase in the future as climate change proceeds. This factor should be taken into consideration when evaluating the overall health and socioeconomic impacts of these fires. Citation: Kollanus V, Prank M, Gens A, Soares J, Vira J, Kukkonen J, Sofiev M, Salonen RO, Lanki T. 2017. Mortality due to vegetation fire-originated PM2.5 exposure in Europe-assessment for the years 2005 and 2008. Environ Health Perspect 125:30-37; http://dx.doi.org/10.1289/EHP194.

Airborne fission products in the High Arctic after the Fukushima nuclear accident.

High-volume aerosol samples were collected at the Mt. Zeppelin Global Atmosphere Watch station, Ny-Ålesund, Svalbard (78°58'N, 11°53'E). The samples were analysed to find out if the radionuclide emissions from the Fukushima nuclear power plant accident in March 2011 could be detected also in the atmosphere of the High Arctic. Iodine-131 and (134)Cs and (137)Cs were observed from 25 March 2011 onwards. The maximum (131)I, (134)Cs and (137)Cs activity concentrations were 810 ± 20, 659 ± 13, and 675 ± 7 µBq/m(3), respectively. The comparison between the measured (131)I activity concentrations at Mt. Zeppelin and those calculated with the SILAM dispersion model revealed that the timing of plume movements could be rather well predicted with the model. The activity concentration levels between the measurements and the model calculations deviated. This can be due to the inaccuracies in the source term. The (134)Cs:(137)Cs activity ratio recorded in Svalbard was high compared to earlier incidents. The ratio was close to 1 which is in agreement with other studies of the Fukushima releases. This distinctive activity ratio in the Fukushima debris could be used as a tracer in Arctic radioecology studies if the activity concentrations are high enough to be detected.