Atmospheric Deposition Of Phosphorus Research Articles

Attributing Atmospheric Phosphorus in the Himalayas: Biomass Burning vs Mineral Dust.

Atmospheric phosphorus is a vital nutrient for ecosystems whose sources and fate are still debated in the fragile Himalayan region, hindering our comprehension of its local ecological impact. This study provides novel insights into atmospheric phosphorus based on the study of total suspended particulate matter at the Qomolangma station. Contrary to the prevailing assumptions, we show that biomass burning (BB), not mineral dust, dominates total dissolved phosphorus (TDP, bioavailable) deposition in this arid region, especially during spring. While total phosphorus is mainly derived from dust (77% annually), TDP is largely affected by the transport of regional biomass-burning plumes from South Asia. During BB pollution episodes, TDP causing springtime TDP fluxes alone accounts for 43% of the annual budget. This suggests that BB outweighs dust in supplying bioavailable phosphorus, a critical nutrient, required to sustain Himalayas' ecological functions. Overall, this first-hand field evidence refines the regional and global phosphorus budget by demonstrating that BB emission, while still unrecognized, is a significant source of P, even in the remote mountains of the Himalayas. It also reveals the heterogeneity of atmospheric phosphorus deposition in that region, which will help predict changes in the impacted ecosystems as the deposition patterns vary.

Interacting effects of urbanization and climate on atmospheric deposition of phosphorus around the globe: A meta-analysis

Over half of the world's human population currently lives in cities, and population density in urban areas is projected to increase over the coming decades. Past studies have shown cities to be hotspots for atmospheric deposition of nitrogen and researchers have found individual cities to have elevated rates of atmospheric phosphorus deposition. However, it remains unknown whether atmospheric phosphorus inputs are elevated in urban areas around the world and how temperature and precipitation affects these inputs. We conducted a meta-analysis to compare atmospheric deposition of phosphorus in urban and rural sites across the globe. We hypothesized that atmospheric phosphorus deposition behaves similarly to atmospheric nitrogen deposition, with increased concentrations and rates of atmospheric phosphorus inputs in urban compared to nearby rural areas. We also hypothesized that the urban enhancement of atmospheric phosphorus inputs is positively influenced by mean annual temperature and precipitation. Data were compiled from 38 cities across 11 countries (i.e. Brazil, China, India, Japan, Pakistan, Spain, Taiwan, Tunisia, Turkey, Ukraine, and United States) and five continents (i.e. Africa, Asia, Europe, North America, and South America). Across the 16 cities that had paired urban and rural sites, there was not a statistically significant difference in atmospheric concentrations nor fluxes of phosphorus deposition between urban and nearby rural sites. However, we found that the difference between rates of atmospheric phosphorus deposition in urban vs. rural sites is positively related to mean annual temperature, though not total annual precipitation. Together these results demonstrate that climatic factors like temperature enhance the urbanization effect, such that sites with warmer temperatures experience a greater difference in urban vs. rural phosphorus deposition rates.

Atmospheric phosphorus deposition amplifies carbon sinks in simulations of a tropical forest in Central Africa.

Spatial redistribution of nutrients by atmospheric transport and deposition could theoretically act as a continental-scale mechanism which counteracts declines in soil fertility caused by nutrient lock-up in accumulating biomass in tropical forests in Central Africa. However, to what extent it affects carbon sinks in forests remains elusive. Here we use a terrestrial biosphere model to quantify the impact of changes in atmospheric nitrogen and phosphorus deposition on plant nutrition and biomass carbon sink at a typical lowland forest site in Central Africa. We find that the increase in nutrient deposition since the 1980s could have contributed to the carbon sink over the past four decades up to an extent which is similar to that from the combined effects of increasing atmospheric carbon dioxide and climate change. Furthermore, we find that the modelled carbon sink responds to changes in phosphorus deposition, but less so to nitrogen deposition. The pronounced response of ecosystem productivity to changes in nutrient deposition illustrates a potential mechanism that could control carbon sinks in Central Africa. Monitoring the quantity and quality of nutrient deposition is needed in this region, given the changes in nutrient deposition due to human land use.

Phosphorus cycling in the upper waters of the Mediterranean Sea (PEACETIME cruise): relative contribution of external and internal sources

Abstract. The study of phosphorus cycling in phosphate-depleted oceanic regions, such as the Mediterranean Sea, has long suffered from methodological limitations, leading to a simplistic view of a homogeneous surface phosphate pool with concentrations below the detection limit of measurement above the phosphacline. During the PEACETIME (Process studies at the air-sea interface after dust deposition in the Mediterranean Sea) cruise, carried out from 10 May to 11 June 2017, we conducted co-located measurements of phosphate pools at the nanomolar level, alkaline phosphatase activities and atmospheric deposition of phosphorus, across a longitudinal gradient from the west to the central Mediterranean Sea. In the phosphate-depleted layer (PDL), between the surface and the phosphacline, nanomolar phosphate was low and showed little variability across the transect spanning from 6 ± 1 nmol L−1 in the Ionian basin to 15 ± 4 nmol L−1 in the westernmost station. The low variability in phosphate concentration contrasted with that of alkaline phosphatase activity, which varied over 1 order of magnitude across the transect. Nanomolar phosphate data revealed gradients of phosphate concentration over density inside the PDL ranging between 10.6 ± 2.2 µmol kg−1 in the westernmost station to values close to zero towards the east. Using the density gradients, we estimated diapycnal fluxes of phosphate to the PDL and compared them to atmospheric deposition, another external source of phosphate to the PDL. Phosphate supply to the PDL from dry deposition and diapycnal fluxes was comparable in the western part of the transect. This result contrasts with the longtime idea that, under stratification conditions, the upper waters of the Mediterranean Sea receive new P almost exclusively from the atmosphere. The contribution of atmospheric deposition to external P supply increased under the occurrence of rain and Saharan dust. Although this finding must be taken cautiously given the uncertainties in the estimation of diapycnal fluxes, it opens exciting questions on the biogeochemical response of the Mediterranean Sea, and more generally of marine oligotrophic regions, to expected changes in atmospheric inputs and stratification regimes. Taken together, external sources of phosphate to the PDL contributed little to total phosphate requirements which were mainly sustained by in situ hydrolysis of dissolved organic phosphorus. The results obtained in this study show a highly dynamic phosphorus pool in the upper layer of the euphotic zone, above the phosphacline, and highlight the convenience of combining highly sensitive measurements and high-resolution sampling to precisely depict the shape of phosphate profiles in the euphotic zone with still unexplored consequences on P fluxes supplying this crucial layer for biogeochemical cycles.

Deforestation strengthens atmospheric transport of mineral dust and phosphorus from North Africa to the Amazon

AbstractPhosphorus contained in atmospheric mineral dust aerosol originating from Africa fertilizes tropical forests in Amazonia. However, the mechanisms influencing this nutrient transport pathway remain poorly understood. Here we use the Community Earth System Model to investigate how large-scale deforestation affects mineral dust aerosol transport and deposition in the tropics. We find that the surface biophysical changes that accompany deforestation produce a warmer, drier and windier surface environment that perturbs atmospheric circulation and enhances long-range dust transport from North Africa to the Amazon. Tropics-wide deforestation weakens the Hadley circulation, which in turn, leads to a northward expansion of the Hadley cell and increases surface air pressure over the Sahara Desert. The high pressure anomaly over the Sahara, in turn, increases northeasterly winds across North Africa and the tropical North Atlantic Ocean, which subsequently increases dust transport to the South America continent. We estimate that the annual atmospheric phosphorus deposition from dust significantly increases by 27% (P < 0.01) in the Amazon under a scenario of complete deforestation. These interactions exemplify how land surface changes can modify tropical nutrient cycling, which in turn, may have consequences for long-term changes in tropical ecosystem productivity and biodiversity.

Enhanced atmospheric phosphorus deposition in Asia and Europe in the past two decades

There is increasing interest in understanding atmospheric phosphorus (P) deposition and its impacts on plant productivity and carbon sinks in ecosystems. However, the global pattern of P deposition remains poorly understood, primarily due to the sparseness of data in Asia. In this study, the authors compiled 396 published observations of atmospheric P deposition from 1959 to 2020 on the global scale. The results gave a geometric mean bulk P deposition value of 0.32 kg ha−1 yr−1, or a global P budget of 4.4 Tg yr−1. Compared with the period 1959–2000, the authors found an elevated P deposition in Europe and Asia during 2001–2020, likely due to the increasing agricultural emissions and fossil fuel combustion–related sources in addition to dust emissions. The findings highlight the need to quantify the impacts of elevated P deposition from anthropogenic emissions on long-term ecosystem development in the context of carbon neutrality and clean-air actions.摘要磷是植物生长必需的元素, 磷缺乏将限制植被生产力及碳汇功能. 为厘清全球大气磷沉降的时空格局, 本文收集了1959–2020年发表的396条观测资料. 结果发现, 全球大气磷沉降的几何均值为0.32 kg ha−1 yr−1, 全球大气磷库约4.4 Tg yr−1. 与1959–2000年相比, 近20年亚洲和欧洲大气磷沉降呈现上升趋势, 主要来源是农业活动,沙尘传输和燃烧源排放. 碳中和背景下, 清洁空气行动是否会改变磷沉降的途径和形态, 进而影响到生态系统的结构和功能, 是需要回答的科学问题.

The use of soil nutrient balances in deriving forest biomass harvesting guidelines specific to region, tree species and soil type in the Netherlands

The substitution of biomass for fossil fuels in energy consumption is a measure to decrease the emissions of greenhouse gases and thereby mitigate global warming. During recent years, this has led to an increasing interest to use tree harvest residues as feedstock for bioenergy. An important concern related to the removal of harvesting residues is, however, the potential adverse effects on soil fertility caused by increased nutrient removal, relative to conventional stem-only harvesting. In the Netherlands this is a major concern, since most forests are located on poor sandy soils.To develop forest harvesting guidelines, we applied a mass balance approach comparing nutrient inputs by deposition and weathering with nutrient outputs by harvesting and leaching for various timber harvesting scenarios, including both stem-only harvesting and additional removal of tree tops and branches. A distinction was made in seven major tree species, six soil types (three sandy soils, loam, clay and peat soils) and nine regions, with clear variations in atmospheric deposition of phosphorus (P), calcium (Ca), magnesium (Mg) and potassium (K). For each region-tree-soil combination we calculated the maximum amounts that can be harvested such that the output of the nutrients Ca, Mg, K and P is balanced with the inputs. Results showed that at current harvesting rates, a negative balance of Ca, Mg, K or P is hardly calculated for the richer loamy to clayey soil types, while depletion can occur for the poorer sandy soils, particularly of P and K. Results are used to derive forest biomass harvesting guidelines, taking the uncertainties in the mass balance approach into account. The role of mitigating management approaches is also discussed.

Atmospheric deposition of elements and its relevance for nutrient budgets of tropical forests

Atmospheric deposition is an important component of the nutrient cycles of terrestrial ecosystems, but field measurements are especially scarce in tropical regions. In this study we analysed 15 months of precipitation chemistry collected in an old growth tropical forest located in French Guiana. We measured nutrient inputs via bulk precipitation and throughfall and used the canopy budget model to estimate nutrient fluxes via canopy exchange and dry deposition. Based on this method we quantified net fluxes of macronutrients and compared their contribution to internal cycling rates via litterfall. Our results suggest that while atmospheric deposition of nitrogen was relatively high (13 kg ha−1 year−1), and mainly in organic forms, the N inputs via litterfall were an order of magnitude higher. In contrast to nitrogen, we found that atmospheric deposition of phosphorus (0.5 kg ha−1 year−1) supplied up to one third of the annual litterfall input to the forest floor. Most strikingly, combined annual inputs of potassium via atmospheric deposition (14 kg ha−1 year−1) and canopy leaching (22 kg ha−1 year−1) were three times larger than internal nutrient recycling via litterfall (11 kg ha−1 year−1). We conclude that atmospheric deposition of phosphorus and especially potassium may play an important role in sustaining the productivity of this old-growth tropical rainforest.

Atmospheric deposition of phosphorus to the Northern Indian Ocean

Air-sea deposition of phosphorus is an important external source of this macronutrient for ocean primary productivity. Although global budgets have shown that atmospheric input of phosphorus is comparable to its riverine supply, studies on regional scale are rather limited. The present article summarizes sources and atmospheric pathway of phosphorus to the ocean surface as a case study of the Northern Indian Ocean. Water-soluble aerosol phosphorus (P Inorg ) concentrations are significantly high over the Bay of Bengal (BoB) compared to those over the Arabian Sea (ARS). Relative increase in the supply of aerosol-P over BoB is attributed to acid-processing of mineral dust during long-range atmospheric transport in addition to its supply from anthropogenic sources. Our estimate of P-deposition to the Northern Indian Ocean (~1.2 Gmol-P year -1 ) is comparable to its atmospheric deposition in other oceanic regions such as the North Atlantic and is also consistent with the model-based projections for the Northern Indian Ocean. These results highlight the importance of atmospheric source in influencing the biogeochemical cycle of phosphorus in the Northern Indian Ocean.

Ten-year determination of atmospheric phosphorus deposition at three forested sites in Japan

Atmospheric phosphorus (P) deposition is an important component for understanding the dynamics of natural and semi-natural ecosystems. However, information about atmospheric P deposition is limited. Here, we show the long-term atmospheric P deposition at three forested sites, a suburban forest (S), rural forest (R1), and northern rural forest (R2) in Japan for 10 years from 2009 to 2018. Approximately 200 samples of bulk precipitation at each site were collected during the study period and total P (TP) was analyzed in addition to major ions. Annual TP deposition at sites S, R1, and R2 was 0.28 ± 0.06, 0.21 ± 0.05, and 0.12 ± 0.04 kg P ha−1 yr−1, respectively, and were large enough to affect P budgets in a forested watershed. Principal component analyses indicated that biogenic sources are the primary contributor to atmospheric P at rural forest sites, whereas anthropogenic sources may have a larger effect on atmospheric P at suburban forest site. Annual TP deposition at site S significantly decreased over the past decade. The significant relationship between annual TP deposition and annual nitrogen deposition at site S indicates that the decrease in TP deposition could be caused by a decrease in anthropogenic emissions.

Magnitude and influence of atmospheric phosphorus deposition on the southern Baltic Sea coast over 23\xa0years: implications for coastal waters

BackgroundThere are various ways for nutrients to enter aquatic ecosystems causing eutrophication. Phosphorus deposition through precipitation can be one pathway, besides point sources, like rivers, and diffuse runoff from land. It is also important to evaluate recent trends and seasonal distribution patterns of phosphorus deposition, as important diffuse source. Therefore, a long-term dataset was analysed including 23 years of daily phosphate bulk depositional rates and 4.5 years of total phosphorus (TP) bulk depositional rates. The study area was at the coastline of the southern Baltic Sea, an area which shows severe eutrophication problems.ResultsThe median daily deposition of phosphate was 56 µg m−2 day−1 (1.8 µmol m−2 day−1) at 4222 rain events. The median annual sum of phosphate deposition was 16.7 kg km−2 a−1, which is comparable to other European areas. The annual TP deposition depended strongly on methodological aspects, especially the sample volume. The median TP-depositional rates ranged between 19 and 70 kg km−2 a−1 depending on the calculated compensation for missing values, as not every rain event could be measured for TP. The highest TP-depositional rates were measured during summer (e.g. up to 9 kg TP km−2 in August 2016). There was no trend detectable for phosphate- and TP-depositional rates over the sampled period.ConclusionsDeposition of P is a considerable nutrient flux for coastal waterbodies. Median total annual deposition contributed 3 t (phosphate) to 10 t (TP) per year into the adjacent lagoon system, being therefore close to annual riverine inflows of 10 t phosphate and 20 t TP per year. However, the impact of precipitation is predicted to be higher in lagoon parts with fewer point sources for phosphorus, if equally distributed over the area of interest.

Optimizing best management practices to control anthropogenic sources of atmospheric phosphorus deposition to inland lakes

ABSTRACTExcessive phosphorus loading to inland freshwater lakes around the globe has resulted in nuisance plant growth along the waterfronts, degraded habitat for cold-water fisheries, and impaired beaches, marinas, and waterfront property. The direct atmospheric deposition of phosphorus can be a significant contributing source to inland lakes. The atmospheric deposition monitoring program for Lake Simcoe, Ontario, indicates roughly 20% of the annual total phosphorus load (2010–2014 period) is due to direct atmospheric deposition (both wet and dry deposition) on the lake. This novel study presents a first-time application of the genetic algorithm (GA) methodology to optimize the application of best management practices (BMPs) related to agriculture and mobile sources to achieve atmospheric phosphorus reduction targets and restore the ecological health of the lake. The novel methodology takes into account the spatial distribution of the emission sources in the airshed, the complex atmospheric long-range transport and deposition processes, cost and efficiency of the popular management practices, and social constraints related to the adoption of BMPs. The optimization scenarios suggest that the optimal overall capital investment of approximately $2M, $4M, and $10M annually can achieve roughly 3, 4, and 5 tonnes reduction in atmospheric P load to the lake, respectively. The exponential trend indicates diminishing returns for the investment beyond roughly $3M per year and that focusing much of this investment in the upwind, nearshore area will significantly impact deposition to the lake. The optimization is based on a combination of the lowest cost, most beneficial and socially acceptable management practices that develops a science-informed promotion of implementation/BMP adoption strategy. The geospatial aspect to the optimization (i.e., proximity and location with respect to the lake) will help land managers to encourage the use of these targeted best practices in areas that will most benefit from the phosphorus reduction approach.Implications: Excessive phosphorus loading to inland freshwater lakes around the globe has resulted in nuisance plant growth along the waterfronts, degraded habitat for cold water fisheries, and impaired beaches, marinas and waterfront property. This novel study presents a first-time application of the Genetic Algorithm methodology to optimize the application of best management practices related to agriculture and mobile sources to achieve atmospheric phosphorus reduction targets and restore the ecological health of the lake. The novel methodology takes into account the spatial distribution of the emission sources in the airshed, the complex atmospheric long-range transport and deposition processes, cost and efficiency of the popular management practices and social constraints related to the adoption of BMPs.

Isotopic signature of atmospheric phosphate emitted from coal combustion

Atmospheric deposition of phosphorus (P) serves as an important nutrient input for many terrestrial, marine and freshwater ecosystems, influencing their biogeochemistry and primary production. Fossil fuel combustion, principally coal, is estimated to be a major source of atmospheric-P in industrialized regions. In this research, we aim to find a distinct isotopic signature for fly coal ash, the by-product of coal combustion that is emitted to the atmosphere. This signature could be used to identify coal's contribution to atmospheric-P. For this aim, ten fly coal ash samples from different coal sources, collected by power station filters, were analyzed for P concentrations and stable oxygen isotopic composition (δ18OP). Two inorganic phosphate fractions were analyzed: HCl-extractable and resin-extractable (bioavailable P). High HCl-P concentrations of up to 3500 μg P/g ash were found with a distinct δ18OP range of 17.1–20.5‰. The resin-P concentrations were substantially lower (<8 μg/g) with a wider and significantly lower δ18OP range of 10.6–16.5‰. The ash samples were found to have HCl-P δ18OP higher in ∼0–∼9‰ relative to the source coal. Similar isotopic values were found for ash with the same coal source country, regardless of the power station. Despite the low bioavailable P concentrations, fly ash could still be an important atmospheric P source to the biosphere since these combustion products likely acidify in the atmosphere to become bioavailable. This is also supported by our finding that smaller particles, which are more indicative of the particles actually emitted to the atmosphere, are significantly P-richer. Natural dust sources' δ18OP overlap fly ash's range, complicating the assessment of coal's contribution. Nonetheless, our results provide a new tool for identification of fossil fuel combustion sources in local and global atmospheric P deposition.

Tracing the Sources of Atmospheric Phosphorus Deposition to a Tropical Rain Forest in Panama Using Stable Oxygen Isotopes.

Atmospheric dust deposition can be a significant source of phosphorus (P) in some tropical forests, so information on the origins and solubility of atmospheric P is needed to understand and predict patterns of forest productivity under future climate scenarios. We characterized atmospheric dust P across a seasonal cycle in a tropical lowland rain forest on Barro Colorado Nature Monument (BCNM), Republic of Panama. We traced P sources by combining remote sensing imagery with the first measurements of stable oxygen isotopes in soluble inorganic phosphate (δ(18)OP) in dust. In addition, we measured soluble inorganic and organic P concentrations in fine (<1 μm) and coarse (>1 μm) aerosol fractions and used this data to estimate the contribution of P inputs from dust deposition to the forest P budget. Aerosol dry mass was greater in the dry season (December to April, 5.6-15.7 μg m(-3)) than the wet season (May to November, 3.1-7.1 μg m(-3)). In contrast, soluble P concentrations in the aerosols were lower in the dry season (980-1880 μg P g(-1)) than the wet season (1170-3380 μg P g(-1)). The δ(18)OP of dry-season aerosols resembled that of nearby forest soils (∼19.5‰), suggesting a local origin. In the wet season, when the Trans-Atlantic Saharan dust belt moves north close to Panama, the δ(18)OP of aerosols was considerably lower (∼15.5‰), suggesting a significant contribution of long-distance dust P transport. Using satellite retrieved aerosol optical depth (AOD) and the P concentrations in aerosols we sampled in periods when Saharan dust was evident we estimate that the monthly P input from long distance dust transport during the period with highest Saharan dust deposition is 88 ± 31 g P ha(-1) month(-1), equivalent to between 10 and 29% of the P in monthly litter fall in nearby forests. These findings have important implications for our understanding of modern nutrient budgets and the productivity of tropical forests in the region under future climate scenarios.

Atmospheric Phosphorus and Nitrogen Originating in China: Forest Deposition and Infiltration of Stream Water in Japan

We analysed nutrients and basic ions (Na, Cl, K, Mg, Si, Ca, and SO4) for a period of 1 year, including every precipitation event, and sampled stream water every 2 weeks from a forest catchment in Shimane Prefecture, Japan. Backward-trajectory analysis revealed that some air masses originated within Japan, but did not affect the precipitation chemistry. Air masses originating from northern China were positively correlated with nutrients and all basic ions. Concentrations of ammonium and dissolved organic nitrogen were much lower in stream water than in precipitation, while those of nitrate and particulate nitrogen were similar in stream water and precipitation. Unlike nitrogen, the dissolved phosphorus concentration was much higher in stream water than in precipitation. Both phosphate and dissolved organic phosphorus (DOP) levels were higher in stream water than in precipitation. Particulate phosphorus (PP) concentrations were very similar in precipitation and stream water. PP showed stronger correlations than potassium with suspended solids (SS) and flow rate, while phosphate and DOP were more strongly correlated with potassium than with SS or flow rate. Stream silica concentrations were not correlated with phosphate but did exhibit a significant negative correlation with DOP. Neither phosphate nor DOP was correlated with calcium. These results suggest that phosphorus is not leaching with silica or calcium as a paired cation, but rather with potassium in this area. Lower nitrogen concentrations in stream water than in precipitation can be attributed to an enhanced uptake of nitrogen by forest soils owing to the increased atmospheric deposition of phosphorus.

Is atmospheric phosphorus pollution altering global alpine Lake stoichiometry?

AbstractAnthropogenic activities have significantly altered atmospheric chemistry and changed the global mobility of key macronutrients. Here we show that contemporary global patterns in nitrogen (N) and phosphorus (P) emissions drive large hemispheric variation in precipitation chemistry. These global patterns of nutrient emission and deposition (N:P) are in turn closely reflected in the water chemistry of naturally oligotrophic lakes (r2 = 0.81, p &lt; 0.0001). Observed increases in anthropogenic N deposition play a role in nutrient concentrations (r2 = 0.20, p &lt; 0.05); however, atmospheric deposition of P appears to be major contributor to this pattern (r2 = 0.65, p &lt; 0.0001). Atmospheric simulations indicate a global increase in P deposition by 1.4 times the preindustrial rate largely due to increased dust and biomass burning emissions. Although changes in the mass flux of global P deposition are smaller than for N, the impacts on primary productivity may be greater because, on average, one unit of increased P deposition has 16 times the influence of one unit of N deposition. These stoichiometric considerations, combined with the evidence presented here, suggest that increases in P deposition may be a major driver of alpine Lake trophic status, particularly in the Southern Hemisphere. These results underscore the need for the broader scientific community to consider the impact of atmospheric phosphorus deposition on the water quality of naturally oligotrophic lakes.

Atmospheric deposition of phosphorus to land and freshwater

We compiled published and newly-obtained data on the directly-measured atmospheric deposition of total phosphorus (TP), filtered total phosphorus (FTP), and inorganic phosphorus (PO4-P) to open land, lakes, and marine coasts. The resulting global data base includes data for c. 250 sites, covering the period 1954 to 2012. Most (82%) of the measurement locations are in Europe and North America, with 44 in Africa, Asia, Oceania, and South-Central America. The deposition rates are log-normally distributed, and for the whole data set the geometric mean deposition rates are 0.027, 0.019 and 0.14 g m(-2) a(-1) for TP, FTP and PO4-P respectively. At smaller scales there is little systematic spatial variation, except for high deposition rates at some sites in Germany, likely due to local agricultural sources. In cases for which PO4-P was determined as well as one of the other forms of P, strong parallels between logarithmic values were found. Based on the directly-measured deposition rates to land, and published estimates of P deposition to the oceans, we estimate a total annual transfer of P to and from the atmosphere of 3.7 Tg. However, much of the phosphorus in larger particles (principally primary biological aerosol particles) is probably redeposited near to its origin, so that long-range transport, important for tropical forests, large areas of peatland and the oceans, mainly involves fine dust from deserts and soils, as described by the simulations of Mahowald et al. (Global Biogeochemical Cycles 22, GB4026, 2008). We suggest that local release to the atmosphere and subsequent deposition bring about a pseudo-diffusive redistribution of P in the landscape, with P-poor ecosystems, for example ombrotrophic peatlands and oligotrophic lakes, gaining at the expense of P-rich ones. Simple calculations suggest that atmospheric transport could bring about significant local redistribution of P among terrestrial ecosystems. Although most atmospherically transported P is natural in origin, local transfers from fertilised farmland to P-poor ecosystems may be significant, and this requires further research.

Atmospheric Nutrient Input to the Baltic Sea from 1850 to 2006: A Reconstruction from Modeling Results and Historical Data

In this study, a consistent basin-wise monthly time series of the atmospheric nutrient load to the Baltic Sea during 1850-2006 was compiled. Due to the lack of a long time series (1850-1960) of nutrient deposition to the Baltic Sea, the data set was compiled by combining a time series of deposition data at the Baltic Nest Institute from 1970 to 2006, published historical monitoring data and deposition estimates, as well as recent modeled Representative Concentration Pathways (RCP) emission estimates. The procedure for nitrogen compounds included estimation of the deposition in a few intermediate reference years, linear interpolation between them, and the decomposition of annual deposition into a seasonal deposition pattern. As no reliable monitoring results were found for the atmospheric deposition of phosphorus during the early period of our study, we used published estimates for the temporal and spatial pattern of the phosphorus load.

Enhanced Solubility and Ecological Impact of Atmospheric Phosphorus Deposition upon Extended Seawater Exposure

Atmospheric P solubility affects the amount of P available for phytoplankton in the surface ocean, yet our understanding of the timing and extent of atmospheric P solubility is based on short-term leaching experiments where conditions may differ substantially from the surface ocean. We conducted longer- term dissolution experiments of atmospheric aerosols in filtered seawater, and found up to 9-fold greater dissolution of P after 72 h compared to instantaneous leaching. Samples rich in anthropogenic materials released dissolved inorganic P (DIP) faster than mineral dust. To gauge the effect of biota on the fate of atmospheric P, we conducted field incubations with aerosol samples collected in the Sargasso Sea and Red Sea. In the Sargasso Sea phytoplankton were not P limited, and biological activity enhanced DIP release from aerosols, and aerosols induced biological mineralization of dissolved organic P in seawater, leading to DIP accumulation. However, in the Red Sea where phytoplankton were colimited by P and N, soluble P was rapidly consumed by phytoplankton following aerosol enrichment. Our results suggest that atmospheric P dissolution could continue over multiple days once reaching the surface ocean, and that previous estimates of atmospheric P deposition may underestimate the contribution from this source.

Atmospheric phosphorus deposition may cause lakes to revert from phosphorus limitation back to nitrogen limitation

Recent findings indicate that increased atmospheric deposition of nitrogen of human origin has caused changes in the pattern of ecological nutrient limitation in lakes in the northern hemisphere. An increase in the nitrogen to phosphorus ratio, and hence a shift from pristine nitrogen limitation to human-induced phosphorus limitation of phytoplankton growth, seems to have been driven by deposition of atmospheric nitrogen. These findings challenge the classical paradigm of lake phytoplankton productivity being naturally limited by phosphorus availability. However, atmospheric phosphorus deposition may also be highly relevant. Here we show how dissolved inorganic nitrogen concentration has decreased in the Pyrenean lake district over recent decades, despite there being an increase in deposition of atmospheric nitrogen. This is related to an increased atmospheric phosphorus load in the lake water, as a result of higher atmospheric inputs. These changes are causing phytoplankton to revert from being phosphorus-limited to being nitrogen-limited.