Long-term dynamics of soil solution in Bavarian forests: Is there a recovering from acidification?

Acid deposition has damaged soils in Central Europe and has been a major source of disturbance for forest ecosystems in the last century. Although acid deposition decreased continuously since the 1990s, it is not clear how fast the damaged soils will recover. We have analysed time series of up to 20 years of precipitation, throughfall and soil solution of the top- and subsoil from 15 Level II forest monitoring sites in Bavaria (Germany). These sites represent a broad range of tree species and soil conditions. As indicators of soil acidification, we calculated the Bc/Al ratio (the ratio of the nutrient cations K, Mg and Ca to Al) and the alkalinity. Additionally, we analysed the trends in Al and SO4 concentrations. To evaluate the temporal dynamics, we extracted the trend of the time series using the model-free method Empirical Mode Decomposition. Our first results suggest that recovery from acidification, i.e. decrease of Al and increase of Bc/Al and alkalinity, is neither uniform nor continuous. We attribute the distinct responses to differences in soil properties among the studied sites

Bayesian calibration of a soil organic carbon model using Δ¹⁴C measurements of soil organic carbon and heterotrophic respiration as joint constraints

Soils of temperate forests store significant amounts of organic matter and are considered to be net sinks of atmospheric CO₂. Soil organic carbon (SOC) turnover has been studied using the Δ¹⁴C values of bulk SOC or different SOC fractions as observational constraints in SOC models. Further, the Δ¹⁴C values of CO₂ that evolved during the incubation of soil and roots have been widely used together with Δ¹⁴C of total soil respiration to partition soil respiration into heterotrophic respiration (HR) and rhizosphere respiration. However, these data have not been used as joint observational constraints to determine SOC turnover times. Thus, we focus on (1) how different combinations of observational constraints help to narrow estimates of turnover times and other parameters of a simple two-pool model, the Introductory Carbon Balance Model (ICBM); (2) whether relaxing the steady-state assumption in a multiple constraints approach allows the source/sink strength of the soil to be determined while estimating turnover times at the same time. To this end ICBM was adapted to model SOC and SO¹⁴C in parallel with litterfall and the Δ¹⁴C of litterfall as driving variables. The Δ¹⁴C of the atmosphere with its prominent bomb peak was used as a proxy for the Δ¹⁴C of litterfall. Data from three spruce-dominated temperate forests in Germany and the USA (Coulissenhieb II, Solling D0 and Howland Tower site) were used to estimate the parameters of ICBM via Bayesian calibration. Key findings are as follows: (1) the joint use of all four observational constraints (SOC stock and its Δ¹⁴C, HR flux and its Δ¹⁴C) helped to considerably narrow turnover times of the young pool (primarily by Δ¹⁴C of HR) and the old pool (primarily by Δ¹⁴C of SOC). Furthermore, the joint use of all observational constraints made it possible to constrain the humification factor in ICBM, which describes the fraction of the annual outflux from the young pool that enters the old pool. The Bayesian parameter estimation yielded the following turnover times (mean ± standard deviation) for SOC in the young pool: Coulissenhieb II 1.1 ± 0.5 years, Solling D0 5.7 ± 0.8 years and Howland Tower 0.8 ± 0.4 years. Turnover times for the old pool were 377 ± 61 years (Coulissenhieb II), 313 ± 66 years (Solling D0) and 184 ± 42 years (Howland Tower), respectively. (2) At all three sites the multiple constraints approach was not able to determine if the soil has been losing or storing carbon. Nevertheless, the relaxed steady-state assumption hardly introduced any additional uncertainty for the other parameter estimates. Overall the results suggest that using Δ¹⁴C data from more than one carbon pool or flux helps to better constrain SOC models

The impact of China's vehicle emissions on regional air quality in 2000 and 2020: a scenario analysis

The number of vehicles in China has been increasing rapidly. We evaluate the impact of current and possible future vehicle emissions from China on Asian air quality. We modify the Regional Emission Inventory in Asia (REAS) for China's road transport sector in 2000 using updated Chinese data for the number of vehicles, annual mileage, and emission factors. We develop two scenarios for 2020: a scenario where emission factors remain the same as they were in 2000 (No-Policy, NoPol), and a scenario where Euro 3 vehicle emission standards are applied to all vehicles (except motorcycles and rural vehicles). The Euro 3 scenario is an approximation of what may be the case in 2020 as, starting in 2008, all new vehicles in China (except motorcycles) were required to meet the Euro 3 emission standards. Using the Weather Research and Forecasting model coupled with Chemistry (WRF/Chem), we examine the regional air quality response to China's vehicle emissions in 2000 and in 2020 for the NoPol and Euro 3 scenarios. We evaluate the 2000 model results with observations in Japan, China, Korea, and Russia. Under NoPol in 2020, emissions of carbon monoxide (CO), nitrogen oxides (NO<sub>x</sub>), non-methane volatile organic compounds (NMVOCs), black carbon (BC), and organic carbon (OC) from China's vehicles more than double compared to the 2000 baseline. If all vehicles meet the Euro 3 regulations in 2020, however, these emissions are reduced by more than 50% relative to NoPol. The implementation of stringent vehicle emission standards leads to a large, simultaneous reduction of the surface ozone (O<sub>3</sub>) mixing ratios and particulate matter (PM<sub>2.5</sub>) concentrations. In the Euro 3 scenario, surface O<sub>3</sub> is reduced by more than 10 ppbv and surface PM<sub>2.5</sub> is reduced by more than 10 μg m<sup>−3</sup> relative to NoPol in Northeast China in all seasons. In spring, surface O<sub>3</sub> mixing ratios and PM<sub>2.5</sub> concentrations in neighboring countries are also reduced by more than 3 ppbv and 1 μg m<sup>−3</sup>, respectively. We find that effective regulation of China's road transport sector will be of significant benefit for air quality both within China and across East Asia as well

Emissions of air pollutants for the World Energy Outlook 2011 Energy Scenarios

This report examines global emissions of major air pollutants (SO2, NOx, PM2.5) resulting from energy scenarios developed for the World Energy Outlook 2012 (OECD/IEA, 2012). Estimates include emissions for 25 regions according to the aggregation used in the IEA World Energy Model (WEM). Emissions have been estimated using the IIASA GAINS model. The 2012 Outlook discusses four energy pathways for the next 25 years. The central scenario, the New Policies (NP) scenario, takes into account recently announced policy commitments and assumes that they are implemented in a cautious manner. The Current Policies (CP) scenario assumes no new policies beyond those adopted by mid-2012. The High Energy Efficiency (HE) scenario simulates the effects of policies aimed at promoting energy efficiency in all countries in the world. The 450 scenario assumes radical policy action consistent with limiting the global temperature increase to two degrees Celsius. All four pathways were implemented into the GAINS model. Next, emissions of air pollutants were calculated. Calculations take into account the current air pollution control legislation and policies in each country or region as adopted or in the pipeline by mid-2012. Presented in this report estimates do not include emissions from international shipping as well as cruising emissions from aviation. They also do not include emissions from biomass burning (deforestation, savannah burning, and vegetation fires). In 2010, world emissions of SO2 from sources covered in this report were about 86 million tons. OECD countries contributed 21 percent of this total. Implementation of pollution controls for the Current Policies Scenario causes an eight percent decrease in world emissions of SO2 in 2020 compared with 2010. This is a combined result of reducing emissions from OECD countries (by about 24 percent), increase in India, and a decrease in China, Russia, South Africa, and Middle East. After 2020, emissions from many non-OECD countries continue rising, which causes an increase of world emissions by about five million tons until 2035. Particularly remarkable is the increase in SO2 emissions in India. The corresponding numbers for NOx are: 85 million tons in 2010 (of which 35 percent originated from the OECD countries), five percent decrease until 2020 and next increase until 2035 by 12 million tons. Emissions of PM2.5 (43 million tons in 2010) are dominated by sources from non-OECD countries - 90 percent of total. Changes in the emissions until 2035 are rather small, with a seven percent decrease in the OECD countries and a stabilization in the developing world. The 450 Scenario causes an important reduction in emissions of air pollutants. In 2035, the emissions of SO2 are 36 percent lower than in the Current Policies case. Emissions of NOx decrease by 32 percent and those of PM2.5 by 11 percent. Emissions for the New Policies and the High Energy Efficiency scenarios lie between those for the Current Policies and the 450 scenarios. Costs of controlling emissions of sulphur and nitrogen oxides and PM (dust) in 2010 are estimated at about 217 billion Euros/a. Until 2035, these costs increase in the Current Policies Scenario by more than a factor of two, which is due to higher activity levels and increasing stringency of controls. In 2035, 61 percent of the total costs are the expenditures on reducing emissions from road transport. The 450 Scenario brings 32 percent cost savings in 2035 compared to the Current Policies case. This study also estimates health impacts of air pollution in Europe, China and India in terms of life years lost (YOLL) attributable to the exposure from anthropogenic emissions of PM2.5. PM concentrations as in 2010 cause a loss of about 2.2 billion life-years. This estimate is dominated by impacts in China and India. The Current Policies Scenario implies an increase of the YOLL indicator in 2035 by 46 percent to 3.3 billion. Decrease of PM2.5 concentrations as in the 450 Scenario in 2035 saves about 870 million life-years. Lower impact indicators and lower control costs in the scenarios that simulate effects of policies towards reducing energy demand and the use of fossil fuels clearly demonstrate important co-benefits of such policies for air pollution

TSAP-2012 Baseline: Health and environmental impacts

This report examines the health and environmental impacts of the TSAP-2012 baseline emission scenarios that have been presented in the TSAP Report #1 to the Stakeholder Expert Group in June 2012. The baseline suggests for the next decades a steady decline of energy-related emissions from industry, households and transport while no significant changes are foreseen for NH3 from agricultural activities. These emission trajectories will lead to significant improvements in air quality. For instance, loss of statistical life expectancy from exposure to fine particulate matter (PM2.5) is expected to decline from 9.6 months in 2000 and 6.9 months in 2010 to 5.5 months in 2020 and 5.0 months in 2030. It is estimated that the number of premature deaths attributable to short-term exposure of ground-level ozone will drop by about 30% by 2020. Ecosystems area where biodiversity is threatened by excess nitrogen deposition will shrink from 1.2 million km2 in 2000 to 900,000 km2 in 2030, and acidification will remain an issue at only four percent of the European forest area. However, by 2020 the baseline improvements for fine particular matter health impacts and eutrophication will fall short of the targets established in the 2005 Thematic Strategy on Air Pollution, while for acidification and ozone these targets will be met. Furthermore, it is unlikely that the baseline development will achieve full compliance with the air quality limit values for PM10 and NO2 throughout Europe. Equally, the baseline scenario will not provide protection against excess nitrogen deposition at almost 50% of the legally protected Natura2000 areas and other protected zones. In addition, the magnitude of air pollution impacts and resulting damage remains substantial. It is estimated that for the baseline in 2030, the European population would still suffer a loss of 210 million life-years and experience 18,000 premature deaths because of ozone exposure. Biodiversity will remain threatened by excess nitrogen input at 900,000 km2 of ecosystems, including 250,000 km2 which are legally protected, inter alia as Natura2000 areas. The analysis also highlights the scope for additional measures that could alleviate the remaining damage and move closer to the objectives of the Sixth Environment Action Program. Full application of readily available technical emission reduction measures in the EU could reduce health impacts from PM by 2020 by another 30% and thereby gain more than 55 million life-years in the EU. It could save another 3,000 premature deaths per year because of lower ozone concentrations. Further controls of agricultural emissions could protect biodiversity at another 200,000 km2 of ecosystems against excess nitrogen deposition, including 50,000 km2 of Natura2000 areas and other protected zones. It could eliminate almost all likely exceedances of PM10 air quality limit values in the old Member States, while in the urban areas of new Member States additional action to substitute solid fuels in the household sector with cleaner forms of energy would be required. Such Europe-wide emission controls would also eliminate in 2030 all likely cases of noncompliance with EU air quality standards for NO2 with the exception of a few stations for which additional local measures (e.g., traffic restrictions, low emission zones) would be necessary. While the general trend appears to be robust, quantification of the remaining effects requires more uncertainty analyses

Emissions of air pollutants for the World Energy Outlook 2012 energy scenarios

This report examines global emissions of major air pollutants (SO2, NOx, PM2.5) resulting from energy scenarios developed for the World Energy Outlook 2012 (OECD/IEA, 2012). Estimates include emissions for 25 regions according to the aggregation used in the IEA World Energy Model (WEM). Emissions have been estimated using the IIASA GAINS model. The 2012 Outlook discusses four energy pathways for the next 25 years. The central scenario, the New Policies (NP) scenario, takes into account recently announced policy commitments and assumes that they are implemented in a cautious manner. The Current Policies (CP) scenario assumes no new policies beyond those adopted by mid-2012. The High Energy Efficiency (HE) scenario simulates the effects of policies aimed at promoting energy efficiency in all countries in the world. The 450 scenario assumes radical policy action consistent with limiting the global temperature increase to two degrees Celsius (2 oC). All the four pathways were implemented into the GAINS model. Next, emissions of air pollutants were calculated. Calculations take into account the current air pollution control legislation and policies in each country or region as adopted or in the pipeline by mid-2012. Presented in this report estimates do not include emissions from international shipping as well as cruising emissions from aviation. They also do not include emissions from biomass burning (deforestation, savannah burning, and vegetation fires). In 2010, world emissions of SO2 from sources covered in this report were about 86 million tons. OECD countries contributed 21 percent of this total. Implementation of pollution controls for the Current Policies Scenario causes an eight percent decrease in world emissions of SO2 in 2020 compared with 2010. This is a combined result of reducing emissions from OECD countries (by about 24 percent), increase in India, and a decrease in China, Russia, South Africa, and Middle East. After 2020, emissions from many non-OECD countries continue rising, which causes an increase of world emissions by about five million tons until 2035. Particularly remarkable is the increase in SO2 emissions in India. The corresponding numbers for NOx are: 85 million tons in 2010 (of which 35 percent originated from the OECD countries), five percent decrease until 2020 and next increase until 2035 by 12 million tons. Emissions of PM2.5 (43 million tons in 2010) are dominated by sources from non-OECD countries -- 90 percent of total. Changes in the emissions until 2035 are rather small, with a seven percent decrease in the OECD countries and a stabilization in the developing world. The 450 Scenario causes an important reduction in emissions of air pollutants. In 2035, the emissions of SO2 are 36 percent lower than in the Current Policies case. Emissions of NOx decrease by 32 percent and those of PM2.5 by 11 percent. Emissions for the New Policies and the High Energy Efficiency scenarios lie between those for the Current Policies and the 450 scenarios. Costs of controlling emissions of sulphur and nitrogen oxides and PM (dust) in 2010 are estimated at about 217 billion Euros/a. Until 2035, these costs increase in the Current Policies Scenario by more than a factor of two, which is due to higher activity levels and increasing stringency of controls. In 2035, 61 percent of the total costs are the expenditures on reducing emissions from road transport. The 450 Scenario brings 32 percent cost savings in 2035 compared to the Current Policies case. This study also estimates health impacts of air pollution in Europe, China and India in terms of life years lost (YOLL) attributable to the exposure from anthropogenic emissions of PM2.5. PM concentrations as in 2010 cause a loss of about 2.2 billion life-years. This estimate is dominated by impacts in China and India. The Current Policies Scenario implies an increase of the YOLL indicator in 2035 by 46 percent to 3.3 billion. Decrease of PM2.5 concentrations as in the 450 Scenario in 2035 saves about 870 million life-years. Lower impact indicators and lower control costs in the scenarios that simulate effects of policies towards reducing energy demand and the use of fossil fuels clearly demonstrate important co-benefits of such policies for air pollution

Global anthropogenic emissions of particulate matter including black carbon

This paper presents a comprehensive assessment of historical (1990–2010) global anthropogenic particulate matter (PM) emissions including the consistent and harmonized calculation of mass-based size distribution (PM1, PM2. 5, PM10), as well as primary carbonaceous aerosols including black carbon (BC) and organic carbon (OC). The estimates were developed with the integrated assessment model GAINS, where source- and region-specific technology characteristics are explicitly included. This assessment includes a number of previously unaccounted or often misallocated emission sources, i.e. kerosene lamps, gas flaring, diesel generators, refuse burning; some of them were reported in the past for selected regions or in the context of a particular pollutant or sector but not included as part of a total estimate. Spatially, emissions were calculated for 172 source regions (as well as international shipping), presented for 25 global regions, and allocated to 0.5°  ×  0.5° longitude–latitude grids. No independent estimates of emissions from forest fires and savannah burning are provided and neither windblown dust nor unpaved roads emissions are included. We estimate that global emissions of PM have not changed significantly between 1990 and 2010, showing a strong decoupling from the global increase in energy consumption and, consequently, CO2 emissions, but there are significantly different regional trends, with a particularly strong increase in East Asia and Africa and a strong decline in Europe, North America, and the Pacific region. This in turn resulted in important changes in the spatial pattern of PM burden, e.g. European, North American, and Pacific contributions to global emissions dropped from nearly 30 % in 1990 to well below 15 % in 2010, while Asia's contribution grew from just over 50 % to nearly two-thirds of the global total in 2010. For all PM species considered, Asian sources represented over 60 % of the global anthropogenic total, and residential combustion was the most important sector, contributing about 60 % for BC and OC, 45 % for PM2. 5, and less than 40 % for PM10, where large combustion sources and industrial processes are equally important. Global anthropogenic emissions of BC were estimated at about 6.6 and 7.2 Tg in 2000 and 2010, respectively, and represent about 15 % of PM2. 5 but for some sources reach nearly 50 %, i.e. for the transport sector. Our global BC numbers are higher than previously published owing primarily to the inclusion of new sources. This PM estimate fills the gap in emission data and emission source characterization required in air quality and climate modelling studies and health impact assessments at a regional and global level, as it includes both carbonaceous and non-carbonaceous constituents of primary particulate matter emissions. The developed emission dataset has been used in several regional and global atmospheric transport and climate model simulations within the ECLIPSE (Evaluating the Climate and Air Quality Impacts of Short-Lived Pollutants) project and beyond, serves better parameterization of the global integrated assessment models with respect to representation of black carbon and organic carbon emissions, and built a basis for recently published global particulate number estimates

Long-term soil warming decreases microbial phosphorus utilization by increasing abiotic phosphorus sorption and phosphorus losses

Phosphorus (P) is an essential and often limiting element that could play a crucial role in terrestrial ecosystem responses to climate warming. However, it has yet remained unclear how different P cycling processes are affected by warming. Here we investigate the response of soil P pools and P cycling processes in a mountain forest after 14 years of soil warming (+4 °C). Long-term warming decreased soil total P pools, likely due to higher outputs of P from soils by increasing net plant P uptake and downward transportation of colloidal and particulate P. Warming increased the sorption strength to more recalcitrant soil P fractions (absorbed to iron oxyhydroxides and clays), thereby further reducing bioavailable P in soil solution. As a response, soil microbes enhanced the production of acid phosphatase, though this was not sufficient to avoid decreases of soil bioavailable P and microbial biomass P (and biotic phosphate immobilization). This study therefore highlights how long-term soil warming triggers changes in biotic and abiotic soil P pools and processes, which can potentially aggravate the P constraints of the trees and soil microbes and thereby negatively affect the C sequestration potential of these forests