Updating the conceptual model for fine particle mass emissions from combustion systems

Atmospheric transformations determine the contribution of emissions from combustion systems to fine particulate matter (PM) mass. For example, combustion systems emit vapors that condense onto existing particles or form new particles as the emissions are cooled and diluted. Upon entering the atmosphere, emissions are exposed to atmospheric oxidants and sunlight, which causes them to evolve chemically and physically, generating secondary PM. This review discusses these transformations, focusing on organic PM. Organic PM emissions are semi-volatile at atmospheric conditions and thus their partitioning varies continuously with changing temperature and concentration. Because organics contribute a large portion of the PM mass emitted by most combustion sources, these emissions cannot be represented using a traditional, static emission factor. Instead, knowledge of the volatility distribution of emissions is required to explicitly account for changes in gas-particle partitioning. This requires updating how PM emissions from combustion systems are measured and simulated from combustion systems. Secondary PM production often greatly exceeds the direct or primary PM emissions; therefore, secondary PM must be included in any assessment of the contribution of combustion systems to ambient PM concentrations. Low-volatility organic vapors emitted by combustion systems appear to be very important secondary PM precursors that are poorly accounted for in inventories and models. The review concludes by discussing the implications that the dynamic nature of these PM emissions have on source testing for emission inventory development and regulatory purposes. This discussion highlights important linkages between primary and secondary PM, which could lead to simplified certification test procedures while capturing the emission components that contribute most to atmospheric PM mass.     

An improved dual channel PERCA instrument for atmospheric measurements of peroxy radicals

This paper describes a new dual-channel PEroxy RadiCal Amplification (PERCA) instrument, which has been designed to improve the time resolution and signal to noise and to reduce the interference caused by variations in ambient ozone concentrations. The instrument was run at the Weybourne Atmospheric Observatory (WAO), North Norfolk, during WAOWEX (Weybourne Atmospheric Observatory Winter Experiment) in January/February 2002 and INSPECTRO (Influence of clouds on the spectral actinic flux in the lower troposphere) in September 2002. The performance of the instrument is assessed and compared to that of a single channel instrument. In particular, it is shown how the precision is greatly improved in fluctuating background ozone conditions. In addition the improved time response of the instrument allows changes in peroxy radical concentrations to be related to rapid changes in nitric oxide concentrations and the ozone photolysis frequency, j(O(1)D).     

Can a key boreal Calanus copepod species now complete its life-cycle in the Arctic? Evidence and implications for Arctic food-webs

The changing Arctic environment is affecting zooplankton that support its abundant wildlife. We examined how these changes are influencing a key zooplankton species, Calanus finmarchicus, principally found in the North Atlantic but expatriated to the Arctic. Close to the ice-edge in the Fram Strait, we identified areas that, since the 1980s, are increasingly favourable to C. finmarchicus. Field-sampling revealed part of the population there to be capable of amassing enough reserves to overwinter. Early developmental stages were also present in early summer, suggesting successful local recruitment. This extension to suitable C. finmarchicus habitat is most likely facilitated by the long-term retreat of the ice-edge, allowing phytoplankton to bloom earlier and for longer and through higher temperatures increasing copepod developmental rates. The increased capacity for this species to complete its life-cycle and prosper in the Fram Strait can change community structure, with large consequences to regional food-webs.Supplementary InformationThe online version contains supplementary material available at 10.1007/s13280-021-01667-y.     

Chronic toxicity of tributyltin to development and reproduction of the European freshwater snail Lymnaea stagnalis (L.)

Chronic toxicity, growth and reproduction were measured in the freshwater gastropod Lymnaea stagnalis exposed to waterborne bis(tri-n-butyltin) oxide (TBTO) over a range of four nominal concentrations (0-10microg TBTl(-1)). Egg development was completely inhibited at 10microg TBTl(-1), whilst abnormal embryonic development was observed at 1microg TBTl(-1). For the solvent control and the 0.01microg TBTl(-1)treatment group, normal development of L. stagnalis was observed. Survivorship of hatchlings was significantly reduced by TBT at 1microgl(-1) while inhibition of shell growth of L. stagnalis was also observed at this concentration. The data were used to determine intrinsic growth rates (r) using two theoretical approaches (the Euler-Lotka equation and a Leslie Matrix). Both approaches showed that survival, fecundity and population growth rate were reduced at 1microg TBTl(-1). Interestingly, at 0.01microg TBTl(-1) snails showed a higher fecundity and growth rate than in the solvent control. The TBT concentration at which the r would equal zero (ECr(0)) and the population NOEC (No Observed Effect Concentration) were estimated. The population NOEC was defined as either the lower 95% confidence or lower 95% pointwise percentile limit of the ECr(0). Values obtained using the two different approaches were similar and thus a geometric mean was calculated to obtain a final representative population NOEC value for L. stagnalis of 2745ng TBTl(-1). The present data together with chronic toxicity TBT data for freshwater organisms, obtained from peer-reviewed literature, were used to construct a species sensitivity distribution (SSD). A predicted no effect concentration was then derived from the SSD (hazardous concentration at 5%, i.e., HC5 or 95% protection level). This SSD was compared with the SSD derived from saltwater species datasets. The HC5 value for saltwater species (3.55ng TBTl(-1); lower confidence limit: 1.93ng TBTl(-1)) was significantly lower than that for freshwater species (30.13ng TBTl(-1); lower confidence limit: 9.23ng TBTl(-1)), indicating that saltwater species are probably more susceptible to TBT than their freshwater counterparts.     

Highway runoff quality in Ireland

Highway runoff has been identified as a significant source of contaminants that impact on the receiving aquatic environment. Several studies have been completed documenting the characteristics of highway runoff and its implication to the receiving water in the UK and elsewhere. However, very little information is available for Ireland. The objective of this study was to determine the quality of highway runoff from major Irish roads under the current road drainage design and maintenance practice. Four sites were selected from the M4 and the M7 motorways outside Dublin. Automatic samplers and continuous monitoring devices were deployed to sample and monitor the runoff quality and quantity. More than 42 storm events were sampled and analysed for the heavy metals Cd, Cu, Pb, and Zn, 16 US EPA specified PAHs, volatile organic compounds including MTBE, and a number of conventional pollutants. All samples were analysed based on the Standard Methods. Significant quantities of solids and heavy metals were detected at all sites. PAHs were not detected very often, but when detected the values were different from quantities observed in UK highways. The heavy metal concentrations were strongly related to the total suspended solids concentrations, which has a useful implication for runoff management strategies. No strong relationship was discovered between pollutant concentrations and event characteristics such as rainfall intensity, antecedent dry days (ADD), or rainfall depth (volume). This study has demonstrated that runoff from Irish motorways was not any cleaner than in the UK although the traffic volume at the monitored sites was relatively smaller. This calls for a site specific investigation of highway runoff quality before adopting a given management strategy.     

A protocol for eliciting nonmaterial values through a cultural ecosystem services frame

Stakeholders’ nonmaterial desires, needs, and values often critically influence the success of conservation projects. These considerations are challenging to articulate and characterize, resulting in their limited uptake in management and policy. We devised an interview protocol designed to enhance understanding of cultural ecosystem services (CES). The protocol begins with discussion of ecosystem‐related activities (e.g., recreation, hunting) and management and then addresses CES, prompting for values encompassing concepts identified in the Millennium Ecosystem Assessment (2005) and explored in other CES research. We piloted the protocol in Hawaii and British Columbia. In each location, we interviewed 30 individuals from diverse backgrounds. We analyzed results from the 2 locations to determine the effectiveness of the interview protocol in elucidating nonmaterial values. The qualitative and spatial components of the protocol helped characterize cultural, social, and ethical values associated with ecosystems in multiple ways. Maps and situational, or vignette‐like, questions helped respondents articulate difficult‐to‐discuss values. Open‐ended prompts allowed respondents to express a diversity of ecosystem‐related values and proved sufficiently flexible for interviewees to communicate values for which the protocol did not explicitly probe. Finally, the results suggest that certain values, those mentioned frequently throughout the interview, are particularly salient for particular populations. The protocol can provide efficient, contextual, and place‐based data on the importance of particular ecosystem attributes for human well‐being. Qualitative data are complementary to quantitative and spatial assessments in the comprehensive representation of people's values pertaining to ecosystems, and this protocol may assist in incorporating values frequently overlooked in decision making processes.     

Importance of Moisture on Stomatal Behavior Of Plants Subjected to Ozone

The stomatal resistance, measured with a ventilated diffusion porometer at various times before, during, and after exposure to 20–25 pphm ozone, was followed in water-stressed or well-watered beans, beans exposed at either low (37%) or high (73%) atmospheric humidity, and two tobacco cultivars exposed at the same two humidities. The two tobacco cultivars that were compared were the 0₃-susceptible Bel W-3 and the 0₃-resistant Consolidated L. The stomata of the water-stressed but unwilted bean plants closed quickly from a resistance of 2.9 ± 0.3 sec/cm to 8.4 ± 1.0 sec/cm when exposed to O₃ whereas those in the unstressed plants closed slowly from a resistance of 2.5 ± 0.6 sec/cm to 5.2 ± 0.8 sec/cm after exposure to O3 for 10 min. Exposure to 0₃ for 30 min in the moist atmosphere caused no change in stomatal resistance of the bean plants whereas in the dry atmosphere the stomata closed from a resistance of 3.7 ± 0.4 sec/cm to 6.7 ± 0.6 sec/cm, but opened again when ozonation was terminated. With tobacco exposed to O₃ in a dry atmosphere the stomata of the 0₃-resistant cultivar closed more rapidly than the 0₃-susceptible variety, whereas in a moist atmosphere the stomata of both cultivars closed slowly and equally during the 60 min of ozonation.     

The contribution of dry deposited ammonia and sulphur dioxide to the composition of precipitation from continuously open gauges

A series of experiments using bulk precipitation collectors of the type used in the UK precipitation chemistry network measured the amounts of NH₄⁺, SO₄²⁻ and other ions that could be washed from funnels (diameter 15 cm) exposed to a wide range of NH₃ and SO₂ concentrations over periods from hours to days. In dry conditions, the average deposition flux of NH₃ was between 50 and 120 nmol NH₄⁺ funnel⁻¹ d⁻¹ (0.1–0.3 kg N ha⁻¹ yr⁻¹), and was independent of the concentration of NH₃. Dry deposition of NH₃ to wet funnels at small NH₃ concentrations was almost 5 times that to dry funnels under the same conditions (average 240 nmol funnel⁻¹ d⁻¹; 0.7 kg ha⁻¹ yr⁻¹), and increased with increasing NH₃ concentrations. The amount of NH₄⁺ ions remaining on the funnel surface was inversely proportional to the vapour pressure deficit during the experiment. This result was interpreted as a dependence on the duration of surface wetness, with greater deposition of NH₄⁺ when evaporation rates of surface water were small.The amount of SO₂ deposited on funnel surfaces was closely related to the amount of NH₃ deposited, in both wet and dry conditions, but was not strongly correlated with the SO₂ concentration. At low NH₃ and SO₂ concentrations the average deposition to dry funnels was 70 nmol SO₄²⁻ funnel⁻¹ d⁻¹ (0.5 kg ha⁻¹ yr⁻¹), and to wet funnels was approximately 2.5 times larger. The results are interpreted in terms of the balance between the rate of evaporation of surface water, and the rate of oxidation of SO₂, which leads to the ‘fixing’ of NH₄⁺ ions on the surface as involatile salts.It is predicted that dry deposition of NH₃ to funnel surfaces across the UK Secondary Network could account for as much as one-half of the measured bulk wet deposition at sites where wet deposition of NH₄–N is small. The amount of dry deposition depends on how long and how often funnel surfaces are wetted by rain or dew, and on the air concentrations of NH₃. These predictions are based on funnels being wetted only once per day. More frequent wetting would increase the contribution from dry deposition, and the consequent overestimate of wet deposition of NH₄–N across the UK by using data obtained from bulk collectors. To some extent this overestimate may be offset by microbial degradation and loss of NH₄–N in weekly bulk precipitation samples during collection and storage.