Solubilities and deposition fluxes of atmospheric Fe and Cu over the Northwest Pacific and its marginal seas

et al. 2021

Atmosphere

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Atmospheric deposition of nutrients to the surface seawater may significantly affect marine phytoplankton growth. Two in situ bioassay experiments were performed in the East China Sea (ECS) by adding nutrients (N, P, and Si) and atmospheric aerosols into the surface seawater. Chlorophyll a (Chl a) concentrations were largely enhanced by simultaneous input of N and P with the maximal increase of 0.68–0.78 μg Chl a per μmol N addition. This Chl a increment was significantly lower (0.19–0.47 μg) in aerosol treatments as a result of initial N-replete condition (N/P ratio ~50) and extremely high N/P ratio in aerosols (>300). Among the multiple influencing factors, atmospheric dry flux of NH4+ + NO3− (AN) was found to be an effective predictor for springtime Chl a in the ECS with a time lag of three days and were strongly correlated with Chl a concentrations on day 3 (r = 0.81, p < 0.001), which might be partly explained by the asynchronous supplies of N (atmospheric deposition) and P (subsurface water). Although dinoflagellates dominated the phytoplankton community in both initial seawaters, additions of P and N + P + Si profoundly enhanced the cell densities and dominance of diatom species Thalassiosira sp. and Nitzschia closterium in the 2012 and 2014 bioassay experiments, respectively. Moreover, the percentage of dinoflagellates were promoted by adding higher NH4+/NO3− ratio (6/4 vs. 1/9) when silicate was at a low concentration (~2 μmol L−1). Atmospheric deposition is likely to be an important N source supporting the high primary production in the ECS and its supply of excess N relative to P may influence dominant phytoplankton groups.

Section: Chl a Nutrients Measurements And Phytoplankton Cell Countingmentioning

confidence: 99%

Responses of Primary Productivity and Phytoplankton Community to the Atmospheric Nutrient Deposition in the East China Sea

Chen

et al. 2021

Atmosphere

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“…The deposition of atmospheric aerosols is a major external source of iron (Fe) in the ocean (Li et al, 2017;Pinedo-González et al, 2020;Yang et al, 2020). Fe is an essential micronutrient that can impact phytoplankton primary productivity, thereby modulating marine ecosystems, global carbon cycling, and climate (Jickells et al, 2005;Tagliabue et al, 2017;Matsui et al, 2018;Lei et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

“…When ambient relative humidity (RH) is above 60 %, aerosol particles can take up water and change the surface to a wet or liquid state (with liquid-liquid separation or a homogenous state, depending on the composition and RH; Sun et al, 2018;Liu et al, 2017). The wet or liquid surface can take up acid gases (such as SO 2 and NO 2 ) and form acidic salts to promote the conversion of Fe from an undissolved to a dissolved form, thereby increasing Fe solubility (Li et al, 2017;Yang et al, 2020;Wong et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

Sources and processes of iron aerosols in a megacity in Eastern China

Zhu

et al. 2022

Atmos. Chem. Phys.

Abstract. Iron (Fe) in aerosol particles is a major external source of micronutrients for marine ecosystems and poses a potential threat to human health. To understand the impacts of aerosol Fe, it is essential to quantify the sources of dissolved Fe and total Fe. In this study, we applied receptor modeling for the first time to apportion the sources of dissolved Fe and total Fe in fine particles collected under five different weather conditions in the Hangzhou megacity of Eastern China, which is upwind of the East Asian outflow. Results showed that Fe solubility (dissolved Fe to total Fe) was the largest on fog days (6.7 ± 3.0 %), followed by haze (4.8 ± 1.9 %), dust (2.1 ± 0.7 %), clear (1.9 ± 1.0 %), and rain (0.9 ± 0.5 %) days. Positive matrix factorization (PMF) analysis suggested that industrial emissions were the largest contributor to dissolved Fe (44.5 %–72.4 %) and total Fe (39.1 %–55.0 %, except for dust days) during haze, fog, dust, and clear days. Transmission electron microscopy analysis of individual particles showed that > 75 % of Fe-containing particles were internally mixed with acidic secondary aerosol species on haze, fog, dust, and clear days. Furthermore, Fe solubility showed significant positive correlations with aerosol acidity/total Fe and liquid water content. These results indicated that the wet surface of aerosol particles promotes heterogeneous reactions between acidic species and Fe aerosols, contributing to a high Fe solubility.

“…When ambient RH is above 50%, the surfaces of secondary aerosol particles start to change from solid to wet or liquid state (Sun et al, 2018), which can take up precursor acid gases and form acidic aqueous medium on the surface of aerosol particles (Li et al, 2016;Zhang et al, 2021). In a word, acid gases such as SO 2 and NO 2 from anthropogenic sources can convert into acidic aerosols on aerosol particles and further promote the conversion of Fe from undissolved to dissolved form, thereby increasing Fe solubility (Li et al, 2017;Zhang et al, 2019a;Yang et al, 2020;Wong et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

Sources and processes of iron aerosols in a megacity of Eastern China

Zhu

et al. 2021

Preprint

Abstract. Iron (Fe) in aerosol particles is a major external source of micronutrients for marine ecosystems, and poses a potential threat to human health. To understand these impacts of aerosol Fe, it is essential to quantify the sources of dissolved and total Fe. In this study, we applied a receptor modelling for the first time to apportion the sources of dissolved and total Fe in fine particles collected under five different weather conditions in Hangzhou megacity of Eastern China, which is upwind of East Asian outflow. Results showed that Fe solubility (dissolved to total Fe) was the largest in fog days (6.3 ± 2.6 %), followed by haze (4.6 ± 1.9 %), dust (2.1 ± 0.7 %), clear (1.7 ± 0.6 %), and rain (0.8 ± 0.3 %) days. Positive Matrix Factorisation (PMF) analysis suggested that industrial and traffic emissions were the two dominant primary sources of dissolved and total Fe during haze and fog days, but dust was the dominant source in dust days. About 15 % of dissolved Fe was associated with secondary sources during haze and fog days, although it was less than 5 % during dust and clear days. Transmission electron microscopy analysis of individual particles showed that approximately 76 % and 87 % of Fe-containing particles were internally mixed with acidic sulfates and nitrates in haze and fog days, respectively. Our results indicated that aqueous surface of aerosol particles promotes heterogeneous reactions between acidic species and Fe aerosol, contributing to higher Fe solubility during fog and haze days.