Trends In Atmospheric Deposition Research Articles

Assessment of Atmospheric Deposition of Potentially Toxic Elements in Macedonia Using a Moss Biomonitoring Technique

This study aims to investigate the changes in atmospheric deposition trends in Macedonia, using a moss biomonitoring technique. This technique has been used to assess the content of potentially toxic elements in Macedonia in 2002, 2005, 2010, and 2015, within the framework of the International Cooperative Program on Effects of Air Pollution on Natural Vegetation and Crops. The content of 42 elements was analyzed using instrumental neutron activation analysis (INAA), inductively coupled plasma–atomic emission spectrometry (ICP–AES), and atomic absorption spectrometry (AAS), on 72 moss samples collected in the summer of 2015. The median values of the elements studied were compared with data from previous years and with median values obtained from comparable studies in Norway and the neighboring countries. Through factor and cluster analysis, three geogenic factors were identified: Factor 1, which includes the elements Al, Ce, Fe, Hf, La, Li, Na, Sc, Sm, Tb, Ti, Th, V, and U; Factor 4, which includes As, Cl, and I; and Factor 5, which includes the elements Ba and Sr. In addition, one geogenic-anthropogenic factor containing Co, Cr, and Ni (Factor 2), was identified, and one anthropogenic factor containing Cd, Pb, Sb, and Zn (Factor 3). The lead and zinc mines near the towns of Kriva Palanka, Probištip, and Makedonska Kamenica in the eastern region of the country, the former lead and zinc smelter in the town of Veles, and the ferronickel smelter near Kavadarci, have continuously had the greatest anthropogenic impact on the atmospheric deposition of potentially toxic elements during the time period of the study. In addition to the human influences, the lithology and the composition of the soil continue to play a significant role in the distribution of the elements.

Mapping spatial and temporal trends of atmospheric deposition of nitrogen at the landscape level in Germany 2005, 2015 and 2020 and their comparison with emission data

Mosses are particularly suitable for recording the accumulation of atmospheric substance inputs in large areas at relatively many locations. In Europe, this has been done every five years since 1990 as part of the European Moss Survey. In this framework, mosses were collected at up to 7312 sites in up to 34 countries and chemically analyzed for metals (since 1990), nitrogen (since 2005), persistent organic pollutants (since 2010) and microplastic (since 2015). The present investigation aimed at determining the nitrogen accumulated in three-year-old shoots from mosses collected in Germany in 2020 by quality-controlled sampling and chemical analysis according to the European Moss Survey Protocol (ICP Vegetation 2020). The spatial structure of the measurement values was analyzed by means of Variogram Analysis, and the respective function was used for Kriging-Interpolation. In addition to mapping the nitrogen values according to the international classification, maps based on 10 percentile classes were calculated. Maps for the Moss Survey 2020 data were compared with respective maps produced from the 2005 and 2015 Moss Survey data. Trends in Germany-wide nitrogen medians over the past three campaigns (2005, 2015 and 2020) show that nitrogen medians decreased by −2 % between 2005 and 2015 and increased by +8 % between 2015 and 2020. These differences are not significant and do not match the emission trends. Therefore, emission register data needs to be controlled by monitoring nitrogen deposition with technical and biological samplers and deposition modelling.

River thorium concentrations can record bedrock fracture processes including some triggered by distant seismic events

Fractures are integral to the hydrology and geochemistry of watersheds, but our understanding of fracture dynamics is very limited because of the challenge of monitoring the subsurface. Here we provide evidence that long-term, high-frequency measurements of the river concentration of the ultra-trace element thorium (Th) can provide a signature of bedrock fracture processes spanning neighboring watersheds in Colorado. River Th concentrations show abrupt (subdaily) excursions and biexponential decay with approximately 1-day and 1-week time constants, concentration patterns that are distinct from all other solutes except beryllium and arsenic. The patterns are uncorrelated with daily precipitation records or seasonal trends in atmospheric deposition. Groundwater Th analyses are consistent with bedrock release and dilution upon mixing with river water. Most Th excursions have no seismic signatures that are detectable 50 km from the site, suggesting the Th concentrations can reveal aseismic fracture or fault events. We find, however, a weak statistical correlation between Th and seismic motion caused by distant earthquakes, possibly the first chemical signature of dynamic earthquake triggering, a phenomenon previously identified only through geophysical methods.

Anthropogenic atmospheric deposition caused the nutrient and toxic metal enrichment of the enclosed lakes in North China

Anthropogenic emissions have resulted in increases in the atmospheric fluxes of both nutrient and toxic elements. However, the long-term geochemical impacts on lake sediments of deposition activities have not been clearly clarified. We selected two small enclosed lakes in northern China—Gonghai, strongly influenced by anthropogenic activities, and Yueliang lake, relatively weakly influenced by anthropogenic activities—to reconstruct historical trends of atmospheric deposition on the geochemistry of the recent sediments. The results showed an abrupt rise in the nutrient levels in Gonghai and the enrichment of toxic metal elements from 1950 (the Anthropocene) onwards. While, at Yueliang lake, the rise on TN was from 1990 onwards. These consequences are attributable to the aggravation of anthropogenic atmospheric deposition in N, P and toxic metals, from fertilizer consumption, mining and coal combustion. The intensity of anthropogenic deposition is considerable, which leave a significant stratigraphic signal of the Anthropocene in lake sediments.

Long-term regional trends of nitrogen and sulfur deposition in the United States from 2002 to 2017

Abstract. Atmospheric deposition of nitrogen (N) and sulfur (S) compounds from human activity has greatly declined in the United States (US) over the past several decades in response to emission controls set by the Clean Air Act. While many observational studies have investigated spatial and temporal trends of atmospheric deposition, modeling assessments can provide useful information over areas with sparse measurements, although they usually have larger horizontal resolutions and are limited by input data availability. In this analysis, we evaluate wet, dry, and total N and S deposition from multiyear simulations within the contiguous US (CONUS). Community Multiscale Air Quality (CMAQ) model estimates from the EPA's (Environmental Protection Agency) Air QUAlity TimE Series (EQUATES) project contain important model updates to atmospheric deposition algorithms compared to previous model data, including the new Surface Tiled Aerosol and Gaseous Exchange (STAGE) bidirectional deposition model which contains land-use-specific resistance parameterization and land-use-specific deposition estimates needed to estimate the differential impacts of N deposition to different land use types. First, we evaluate model estimates of wet deposition and ambient concentrations, finding underestimates of SO4, NO3, and NH4 wet deposition compared to National Atmospheric Deposition Program observations and underestimates of NH4 and SO4 and overestimates of SO2 and TNO3 (HNO3+NO3) compared to the Clean Air Status and Trends Network (CASTNET) ambient concentrations. Second, a measurement–model fusion approach employing a precipitation and bias correction to wet-deposition estimates is found to reduce model bias and improve correlations compared to the unadjusted model values. Model agreement of wet deposition is poor over parts of the West and Northern Rockies, due to errors in precipitation estimates caused by complex terrain and uncertainty in emissions at the relatively coarse 12 km grid resolution used in this study. Next, we assess modeled N and S deposition trends across climatologically consistent regions in the CONUS. Total deposition of N and S in the eastern US is larger than the western US with a steeper decreasing trend from 2002–2017; i.e., total N declined at a rate of approximately −0.30 kg N ha−1 yr−1 in the Northeast and Southeast and by −0.02 kg N ha−1 yr−1 in the Northwest and Southwest. Widespread increases in reduced N deposition across the Upper Midwest, Northern Rockies, and West indicate evolving atmospheric composition due to increased precipitation amounts over some areas, growing agricultural emissions, and regional NOx/SOx emission reductions shifting gas–aerosol partitioning; these increases in reduced N deposition are generally masked by the larger decreasing oxidized N trend. We find larger average declining trends of total N and S deposition between 2002–2009 than 2010–2017, suggesting a slowdown of the rate of decline likely in response to smaller emission reductions. Finally, we document changes in the modeled total N and S deposition budgets. The average annual total N deposition budget over the CONUS decreases from 7.8 in 2002 to 6.3 kg N ha−1 yr−1 in 2017 due to declines in oxidized N deposition from NOx emission controls. Across the CONUS during the 2002–2017 time period, the average contribution of dry deposition to the total N deposition budget drops from 60 % to 52 %, whereas wet deposition dominates the S budget rising from 45 % to 68 %. Our analysis extends upon the literature documenting the growing contribution of reduced N to the total deposition budget, particularly in the Upper Midwest and Northern Rockies, and documents a slowdown of the declining oxidized N deposition trend, which may have consequences on vegetation diversity and productivity.

Major point and nonpoint sources of nutrient pollution to surface water have declined throughout the Chesapeake Bay watershed

Understanding drivers of water quality in local watersheds is the first step for implementing targeted restoration practices. Nutrient inventories can inform water quality management decisions by identifying shifts in nitrogen (N) and phosphorus (P) balances over space and time while also keeping track of the likely urban and agricultural point and nonpoint sources of pollution. The Chesapeake Bay Program’s Chesapeake Assessment Scenario Tool (CAST) provides N and P balance data for counties throughout the Chesapeake Bay watershed, and these data were leveraged to create a detailed nutrient inventory for all the counties in the watershed from 1985–2019. This study focuses on three primary watershed nutrient balance components—agricultural surplus, atmospheric deposition, and point source loads—which are thought to be the leading anthropogenic drivers of nutrient loading trends across the watershed. All inputs, outputs, and derived metrics (n=53) like agricultural surplus and nutrient use efficiency, were subjected to short- and long-term trend analyses to discern how sources of pollution to surface water have changed over time. Across the watershed from 1985–2019, downward trends in atmospheric deposition were ubiquitous. Though there are varying effects, long-term declines in agricultural surplus were observed, likely because nutrients are being managed more efficiently. Multiple counties’ point source loads declined, primarily associated with upgrades at major cities that discharge treated wastewater directly to tidal waters. Despite all of these positive developments, recent increases in agricultural surpluses from 2009–2019 highlight that water quality gains may soon be reversed in many agricultural areas of the basin. Besides tracking progress and jurisdictional influence on pollution sources, the nutrient inventory can be used for retrospective water quality analysis to highlight drivers of past improvement/degradation of water quality trends and for decision makers to develop and track their near- and long-term watershed restoration strategies.

Freshwater salinization syndrome: from emerging global problem to managing risks

Freshwater salinization is an emerging global problem impacting safe drinking water, ecosystem health and biodiversity, infrastructure corrosion, and food production. Freshwater salinization originates from diverse anthropogenic and geologic sources including road salts, human-accelerated weathering, sewage, urban construction, fertilizer, mine drainage, resource extraction, water softeners, saltwater intrusion, and evaporative concentration of ions due to hydrologic alterations and climate change. The complex interrelationships between salt ions and chemical, biological, and geologic parameters and consequences on the natural, social, and built environment are called Freshwater Salinization Syndrome (FSS). Here, we provide a comprehensive overview of salinization issues (past, present, and future), and we investigate drivers and solutions. We analyze the expanding global magnitude and scope of FSS including its discovery in humid regions, connections to human-accelerated weathering and mobilization of ‘chemical cocktails.’ We also present data illustrating: (1) increasing trends in salt ion concentrations in some of the world’s major freshwaters, including critical drinking water supplies; (2) decreasing trends in nutrient concentrations in rivers due to regulations but increasing trends in salinization, which have been due to lack of adequate management and regulations; (3) regional trends in atmospheric deposition of salt ions and storage of salt ions in soils and groundwater, and (4) applications of specific conductance as a proxy for tracking sources and concentrations of groups of elements in freshwaters. We prioritize FSS research needs related to better understanding: (1) effects of saltwater intrusion on ecosystem processes, (2) potential health risks from groundwater contamination of home wells, (3) potential risks to clean and safe drinking water sources, (4) economic and safety impacts of infrastructure corrosion, (5) alteration of biodiversity and ecosystem functions, and (6) application of high-frequency sensors in state-of-the art monitoring and management. We evaluate management solutions using a watershed approach spanning air, land, and water to explore variations in sources, fate and transport of different salt ions (e.g. monitoring of atmospheric deposition of ions, stormwater management, groundwater remediation, and managing road runoff). We also identify tradeoffs in management approaches such as unanticipated retention and release of chemical cocktails from urban stormwater management best management practices (BMPs) and unintended consequences of alternative deicers on water quality. Overall, we show that FSS has direct and indirect effects on mobilization of diverse chemical cocktails of ions, metals, nutrients, organics, and radionuclides in freshwaters with mounting impacts. Our comprehensive review suggests what could happen if FSS were not managed into the future and evaluates strategies for reducing increasing risks to clean and safe drinking water, human health, costly infrastructure, biodiversity, and critical ecosystem services.

Atmospheric Deposition and Element Accumulation in Moss Sampled across Germany 1990–2015: Trends and Relevance for Ecological Integrity and Human Health

Deposition of N and heavy metals can impact ecological and human health. This state-of-the-art review addresses spatial and temporal trends of atmospheric deposition as monitored by element accumulation in moss and compares heavy metals Critical Loads for protecting human health and ecosystem’s integrity with modelled deposition. The element accumulation due to deposition was measured at up to 1026 sites collected across Germany 1990–2015. The deposition data were derived from chemical transport modelling and evaluated with regard to Critical Loads published in relevant legal regulations. The moss data indicate declining nitrogen and HM deposition. Ecosystem and human health Critical Loads for As, Ni, Zn, and Cr were not exceeded in Germany 2009–2011. Respective Critical Loads were exceeded by Hg and Pb inputs, especially in the low rainfall regions with forest coverage. The Critical Load for Cu was exceeded by atmospheric deposition in 2010 in two regions. Human health Critical Loads for Cd were not exceeded by atmospheric deposition in 2010. However, the maximum deposition in 2010 exceeded the lowest human health Critical Load. This impact assessment was based only on deposition but not on inputs from other sources such as fertilizers. Therefore, the assessment should be expanded with regard to other HM sources and specified for different ecosystem types.

Contrasting long-term trends of chloride levels in remote and human-disturbed lakes in south-central Ontario, Canada

Yao H, Paterson AM, James AL, McConnell C, Field T, Ingram R, Zhang D, Arnott SE, Higgins SN. 2020. Contrasting long-term trends of chloride levels in remote and human-disturbed lakes in south-central Ontrario, Canada. Lake Reserv Manage. XX:XXX–XXX. We examined a 41 yr data record from 4 monitored lakes in south-central Ontario, Canada, to demonstrate and explain long-term changes in chloride (Cl) loading and in-lake concentrations in relation to the degree of watershed disturbance. A mass balance calculation for each lake was used to determine ungauged shoreline loads. Correlations of lake Cl concentrations with each of 3 major contributing sources (inputs from inflowing streams, atmospheric deposition, and ungauged shoreline areas) revealed the contribution of each source to Cl trends at each lake. Areal loads (Cl load per year per unit area) showed the relative intensity of the contributions. Two lakes (Red Chalk, Plastic) with relatively undisturbed watersheds showed declining trends in atmospheric deposition, stream loads, lake export, and lake Cl concentrations, whereas 2 lakes (Harp, Dickie) with disturbed watersheds showed increased stream loads, lake export, and lake concentrations, despite long-term declines in atmospheric deposition. This contrasting trend was related to increased Cl concentrations in inflowing streams, which were caused by increased residential development and road salt applications. The ungauged shoreline loads in the disturbed watersheds made a contribution as high as 80% to total Cl loads. As increasing Cl concentrations have implications for aquatic biota, even at the relatively low concentrations observed in the study lakes, these findings highlight the need for improved management of road salt applications. Our results confirm that even relatively remote lakes within the Canadian Shield are potentially at risk from watershed disturbances that are disrupting the natural loading of Cl to inland waters.

Multivariate assessment of atmospheric deposition studies in Bulgaria based on moss biomonitors: trends between the 2005/2006 and 2015/2016 surveys.

This study aims to investigate the changes in atmospheric deposition trends in Bulgaria, studied using the moss biomonitoring technique since 1995. For the first time, a paired (site-wise) comparison was performed after a critical review of the sampling networks and adjusting for location, the distance between the sampling points, and moss species. Data from the 2005/2006 and 2015/2016 moss surveys were chosen as instrumental neutron activation analysis was employed in both to determine the content of 34 elements (Al, As, Ba, Br, Са, Ce, Cl, Со, Cr, Cs, Fe, Hf, I, K, La, Mn, Na, Nd, Ni, Rb, Sb, Sc, Se, Sr, Ta, Tb, Th, Ti, Tm, U, V, W, Yb, Zn). In addition, Cd, Cu, and Pb were determined using complementary analytical methods: inductively coupled plasma atomic emission spectroscopy in 2015/2016 and atomic absorption spectroscopy in 2005/2006. For the subset of 57 routinely sampled locations in Bulgaria, hierarchical clustering on principal components and multiple factor analysis (MFA) were applied to assess the spatial trends inthe 10years elapsed between the surveys, as well as to characterise the origin of the determined elements. Elevation and distance between the sampling points were used as additional variables in the multiple factor analysis plane to ascertain their effect on the overall variance in the datasets. Distribution maps were constructed to illustrate the deposition patterns for the pollutant Pb. The results were consistent with decreased industrial output in the country, increased coal combustion and transport pollution, and construction of roads.

Evidence for accelerated weathering and sulfate export in high alpine environments

High elevation alpine ecosystems—the ‘water towers of the world’—provide water for human populations around the globe. Active geomorphic features such as glaciers and permafrost leave alpine ecosystems susceptible to changes in climate which could also lead to changing biogeochemistry and water quality. Here, we synthesize recent changes in high-elevation stream chemistry from multiple sites that demonstrate a consistent and widespread pattern of increasing sulfate and base cation concentrations or fluxes. This trend has occurred over the past 30 years and is consistent across multiple sites in the Rocky Mountains of the United States, western Canada, the European Alps, the Icelandic Shield, and the Himalayas in Asia. To better understand these recent changes and to examine the potential causes of increased sulfur and base cation concentrations in surface waters, we present a synthesis of global records as well as a high resolution 33 year record of atmospheric deposition and river export data from a long-term ecological research site in Colorado, USA. We evaluate which factors may be driving global shifts in stream chemistry including atmospheric deposition trends and broad climatic patterns. Our analysis suggests that recent changes in climate may be stimulating changes to hydrology and/or geomorphic processes, which in turn lead to accelerated weathering of bedrock. This cascade of effects has broad implications for the chemistry and quality of important surface water resources.

Use of an epiphytic lichen and a novel geostatistical approach to evaluate spatial and temporal changes in atmospheric deposition in the Athabasca Oil Sands Region, Alberta, Canada

Temporal and spatial atmospheric deposition trends of elements to the boreal forest surrounding bitumen production operations in the Athabasca Oil Sands Region (AOSR), Alberta, Canada were investigated as part of a long-term lichen bioindicator study. The study focused on eight elements (sulfur, nitrogen, aluminum, calcium, iron, nickel, strontium, vanadium) that were previously identified as tracers for the major oil sand production sources. Samples of the in situ epiphytic lichen Hypogymnia physodes were collected in 2002, 2004, 2008, 2011, 2014, and 2017 within a ~150 km radius from the center of surface oil sand production operations in the AOSR. Site-specific time series analysis conducted at eight jack pine upland sites that were repeatedly sampled generally showed significant trends of increasing lichen concentrations for fugitive dust linked elements, particularly at near-field (<25 km from a major oil sands production operation) sample locations. Multiple regional scale geostatistical models were developed and evaluated to characterize broad-scale changes in atmospheric deposition based on changes in H. physodes elemental concentrations between 2008 and 2014. Empirical Bayesian kriging and cokriging lichen element concentrations with oil sands mining, bitumen upgrading, coke materials handling, and limestone quarry/crushing influence variables produced spatial interpolation estimates with the lowest validation errors. Gridded zonal mean lichen element concentrations were calculated for the two comprehensive sampling years (2008, 2014) and evaluated for spatial and temporal change. Lichen sulfur concentrations significantly increased in every grid cell within the domain with the largest increases (44-88%) in the central valley in close proximity to the major surface oil sand production operations, while a minor nitrogen concentration decrease (-20%) in a single grid cell was observed. The areal extent of fugitive dust element deposition generally increased with significantly higher deposition to lichens restricted to the outer grids of the enhanced deposition field, reflecting new and expanding surface mining activity.

Interspecies comparison of three moss species (Hylocomium splendens, Pleurozium schreberi, and Isothecium stoloniferum) as biomonitors of trace element deposition.

Biomonitoring with mosses is a common method widely used to assess the spatial and temporal trends of atmospheric deposition in Europe since its introduction in the 1970s. Based on previous investigations, certain moss species provide the most accurate reflection of atmospheric deposition. However, sampling of just one species across large areas can pose a challenge, therefore the ability to use multiple moss species interchangeably is integral to an effective moss biomonitoring survey. In this study, biomonitoring abilities of two common species (Hylocomium splendens [Hs] and Pleurozium schreberi [Ps]) were compared to a potential new biomonitoring species endemic to North America (Isothecium stoloniferum [Is]). Thirteen metal concentrations were analyzed (Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Cd, and Pb) in moss tissue from 20 sites with co-located species (Ps/Hs, Is/Hs) Five metals (Al, V, Fe, Ni, and Pb) showed significant and strong correlations (Spearman correlation, r ≥ 0.7 α = 0.05) for all three species, reflecting the established deposition gradient in the region. Furthermore, there was no significant difference in observations (and moderate correlation) for Cr, which suggests that all species exhibited similar uptake abilities for these six metals (Al, V, Cr, Fe, Ni, and Pb). Four metals (Co, As, Se, and Cd) exhibited concentrations below detection at a number of sites, which may have influenced the assessment of interspecies relationships. It is recommended that interspecies calibration be carried out under all surveys that employ multiple moss species.

Disturbance and resilience of a granitic critical zone submitted to acid atmospheric influence (the Ringelbach catchment, Vosges Mountains, France): Lessons from a hydrogeochemical survey in the nineties

The chemistry of precipitations and stream waters in the critical zone of a small granitic catchment mainly covered by grassland has been investigated backward (period 1990–1997). Major elements concentrations, fluxes and budgets at annual and seasonal scales allowed evaluating the catchment response to variation trends in atmospheric deposition and hydrological patterns. Acid precipitation was efficiently buffered by soil cations exchange and mineral weathering processes, as attested by the dominance of Ca and HCO3 in stream waters. A decrease of sulfate acidity in precipitation following clean air measures was accompanied by an increase of alkalinity and a decrease of sulfate in stream waters. Waters of short residence time from water-saturated areas in the valley bottom and rapid shallow circulations within slopes were a very effective diluted weathering end-member contributing to stream outlet in high flow conditions, whereas evapotranspiration from saturated areas and/or deep waters with long residence time influenced the stream water concentration pattern in low flow conditions.Water discharge controlled the variations of the annual and seasonal budgets of major elements, except for nitrate and sulfate, mainly stored during summer. Soil legacy sulfate was mainly released during the first autumn stormflows, with high peak concentrations decreasing rapidly from 1990 to 1992 and disappearing afterwards. The output water flux was the main driver of the weathering rate in the acidification recovery period 1993–97, contrary to the first period 1990–92 when acidification was still under way, as attested by the weathering plateau (constant Si/ΣBC ratio). At that time, the intense weathering testifies the disturbance caused by acidification process. However, this critical zone was resilient enough to allow rapid and significant recovery over a few years following sulfur atmospheric abatement. For the future, the atmospheric nitrogen deposition pressure remains still challenging in a global change context, which argues for the necessity of long-term observatories.

Decadal trends in atmospheric deposition in a high elevation station: Effects of climate and pollution on the long-range flux of metals and trace elements over SW Europe

Atmospheric deposition collected at remote, high elevation stations is representative of long-range transport of elements. Here we present time-series of Al, Fe, Ti, Mn, Zn, Ni, Cu, As, Cd and Pb deposition sampled in the Central Pyrenees at 2240 m a.s.l, representative of the fluxes of these elements over South West Europe. Trace element deposition did not show a simple trend. Rather, there was statistical evidence of several underlying factors governing the variability of the time-series recorded: seasonal cycles, trends, the effects of the amount of precipitation, climate-controlled export of dust, and changes in anthropogenic emissions. Overall, there were three main modes of variation in deposition. The first mode was related to North Atlantic Oscillation (NAO), and affected Al, Fe, Ti, Mn and Pb. We interpret this as changes in the dust export from Northern Africa under the different meteorological conditions that the NAO index indicates. The second mode was an upward trend related to a rise in the frequency of precipitation events (that also lead to an increase in the amount). More frequent events might cause a higher efficiency in the scavenging of aerosols. As, Cu and Ni responded to this. And finally, the third mode of variation was related to changes in anthropogenic emissions of Pb and Zn.

Monitorización y tendencias de la deposición de N en España, incluyendo polvo sahariano

Avila, A., Aguillaume, L. 2017. Monitoring and deposition trends in Spain, including Saharan dust. Ecosistemas 26(1): 16-24. Doi.: 10.7818/ECOS.2017.26-1.04 The chemical composition of the atmosphere has significantly changed in the last century, mostly due to increased emissions of gases and particles derived from human activities. Several studies have analyzed the trends in the chemical composition of rainwater and atmospheric deposition in recent decades in central and northern Europe. However, for Spain there is a lack of studies at national level. Up to now, analyses of decadal trends are only available from a few individual stations.In this paper we first present the different methods to measure atmospheric deposition. Then we compile a list of atmospheric deposition monitoring stations in Spain and review the available time series, for series longer than 10 years, with special attention to the trends of N, S and African dust. Finally, we indicate future research directions to fill the gaps in knowledge about patterns and trends of atmospheric deposition at a national level.

Changes in Sport Fish Mercury Concentrations from Food Web Shifts Suggest Partial Decoupling from Atmospheric Deposition in Two Colorado Reservoirs

Partial decoupling of mercury (Hg) loading and observed Hg concentrations ([Hg]) in biotic and abiotic samples has been documented in aquatic systems. We studied two Colorado reservoirs to test whether shifts in prey for sport fish would lead to changes in [Hg] independent of external atmospheric Hg deposition. We compared sport fish total mercury concentrations ([T-Hg]) and macroinvertebrate (chironomids and crayfish) methylmercury concentrations ([MeHg]) before and after food web shifts occurred in both reservoirs. We also monitored wet atmospheric Hg deposition and sediment [T-Hg] and [MeHg] at each reservoir. We found rapid shifts in Hg bioaccumulation in each reservoir's sport fish, and these changes could not be attributed to atmospheric Hg deposition. Our study shows that trends in atmospheric deposition, environmental samples (e.g., sediments), and samples of species at the low trophic levels (e.g., chironomids and crayfish) may not accurately reflect conditions that result in fish consumption advisories for high trophic level sport fish. We suggest that in the short-term, monitoring fish [Hg] is necessary to adequately protect human health because natural and anthropogenic perturbations to aquatic food-webs that affect [Hg] in sport fish will continue regardless of trends in atmospheric deposition.

Heavy Metals in Epiphytic Lichens and Mosses of Oil–Producing Communities of Eket and Ibeno, Akwa Ibom State – Nigeria

Epiphytic lichen (Parmelia carperata) and moss (Polytrichum juniperinum, Calymperes erosum and Racopilum africanum) samples were used as bioindicators and bioaccumulators of atmospheric heavy metals deposition in oil–producing host communities of Eket and Ibeno Local Government Areas of Akwa Ibom State – Nigeria. Sampling of lichen and moss species that are found to grow extensively and abundantly on the stems and branches of several plants was performed during September 2014 at 25 sampling location sevenly distributed over the two oil–producing host communities studied. Unwashed, oven dried and homogenized powdered lichen and moss samples were mineralized using wet digestion with 3:1 mixture of concentrated nitric acid and perchloric acid in Teflon beakers on a Gerhardt digestion hot plate. The concentrations of heavy metals and/or trace elements were determined by atomic absorption spectrometry (AAS) equipped with flame and/or graphite furnace systems. The concentration of heavy metals in lichen and moss samples ranged from 0.003 – 0.009 μg g−1 for Cadmium (Cd); 0.006 – 7.654 μg g−1 for Chromium (Cr); 1.120 – 1.999 μg g−1 for Cobalt (Co); 8.954 – 116.760 μg g−1 for Copper; 25.980 – 193.260 μg g−1 for Manganese (Mn); 2.268 – 23.783 μg g−1 for Nickel (Ni); 0.034 – 14.880 μg g−1 for Lead (Pb), and 26.230 – 98.780μg g−1 for Zinc (Zn).The mean concentration of heavy metals in the lichen and moss samples can be arranged in the decreasing order as follows: Mn > Zn > Cu > Ni > Cr > Pb > Co > Cd and the statistical analyses revealed that strong correlations exist between Cu–Pb, Cu–Zn, Pb–Ni and Mn–Zn concentrations. Some of the target heavy metals such as Cd, Cr, Mn, Ni and Zn were accumulated at higher concentrations in mosses compared to lichens from the same sampling location. There is some evidence that different site–specific characteristics affect the spatial distributions patterns and temporal trends of atmospheric deposition of heavy metals in the two oil–producing communities of Eket and Ibeno, Akwa Ibom State – Nigeria. However, a comparison with the previous study conducted in 2004by Ite et al. showed a slightly decreasing trend of atmospheric heavy metal deposition and these results confirmed that air quality has not further deteriorated in the two oil–producing communities studied over the last 10 years.

Contrasted spatial and long-term trends in precipitation chemistry and deposition fluxes at rural stations in France

The long-distance effect of atmospheric pollution on ecosystems has led to the conclusion of international agreements to regulate atmospheric emissions and monitor their impact. This study investigated variations in atmospheric deposition chemistry in France using data gathered from three different monitoring networks (37 stations) over the period from 1995 to 2007. Despite some methodological differences (e.g. type of collector, frequency of sampling and analysis), converging results were found in spatial variations, seasonal patterns and temporal trends. With regard to spatial variations, the mean annual pH in particular ranged from 4.9 in the north-east to 5.8 in the south-east. This gradient was related to the concentration of NO3− and non-sea-salt SO42− (maximum volume-weighted mean of 38 and 31 μeq l−1 respectively) and of acid-neutralising compounds such as non-sea-salt Ca2+ and NH4+. In terms of seasonal variations, winter and autumn pH were linked to lower acidity neutralisation than during the warm season. The temporal trends in atmospheric deposition varied depending on the chemical species and site location. The most significant and widespread trend was the decrease in non-sea-salt SO42− concentrations (significant at 65% of the stations). At the same time, many stations showed an increasing trend in annual pH (+0.3 on average for 16 stations). These two trends are probably due to the reduction in SO2 emissions that has been imposed in Europe since the 1980s. Temporal trends in inorganic N concentrations were rather moderate and not consistent with the trends reported in emission estimates. Despite the reduction in NOx emissions, NO3− concentrations in atmospheric deposition remained mostly unchanged or even increased at three stations (+0.43 μeq l−1 yr−1 on average). In contrast NH4+ concentrations in atmospheric deposition decreased at several stations located in western and northern areas, while the estimates of NH3 emissions remained fairly stable. The decrease in non-sea-salt SO42− and NH4+ concentrations was mainly due to a decrease in summer values and can in part be related to a dilution process since the precipitation amount showed an increasing trend during the summer. Furthermore, increasing trends in NO3− concentrations in the spring and, to a lesser extent, in NH4+ concentrations suggested that other atmospheric physicochemical processes should also be taken into account.

Detection of temporal trends in atmospheric deposition of inorganic nitrogen and sulphate to forests in Europe

Atmospheric deposition to forests has been monitored within the International Cooperative Programme on Assessment and Monitoring of Air Pollution Effects on Forests (ICP Forests) with sampling and analyses of bulk precipitation and throughfall at several hundred forested plots for more than 15 years. The current deposition of inorganic nitrogen (nitrate and ammonium) and sulphate is highest in central Europe as well as in some southern regions. We compared linear regression and Mann–Kendall trend analysis techniques often used to detect temporal trends in atmospheric deposition. The choice of method influenced the number of significant trends. Detection of trends was more powerful using monthly data compared to annual data. The slope of a trend needed to exceed a certain minimum in order to be detected despite the short-term variability of deposition. This variability could to a large extent be explained by meteorological processes, and the minimum slope of detectable trends was thus similar across sites and many ions. The overall decreasing trends for inorganic nitrogen and sulphate in the decade to 2010 were about 2% and 6%, respectively. Time series of about 10 and 6 years were required to detect significant trends in inorganic nitrogen and sulphate on a single plot. The strongest decreasing trends were observed in western central Europe in regions with relatively high deposition fluxes, whereas stable or slightly increasing deposition during the last 5 years was found east of the Alpine region as well as in northern Europe. Past reductions in anthropogenic emissions of both acidifying and eutrophying compounds can be confirmed due to the availability of long-term data series but further reductions are required to reduce deposition to European forests to levels below which significant harmful effects do not occur according to present knowledge.