Elsevier

Atmospheric Environment

Volume 35, Issue 32, November 2001, Pages 5629-5643
Atmospheric Environment

Chemistry of fog waters in California's Central Valley—Part 3: concentrations and speciation of organic and inorganic nitrogen

https://doi.org/10.1016/S1352-2310(01)00337-5Get rights and content

Abstract

Although organic nitrogen (ON) has been found to be a ubiquitous and significant component in wet and dry deposition, almost nothing is known about its concentration or composition in fog waters. To address this gap, we have investigated the concentration and composition of ON in fog waters collected in Davis, in California's Central Valley. Significant quantities of dissolved organic nitrogen (DON) were found in these samples, with a median concentration of 303 μM N (range=120–1630 μM N). DON typically represented approximately 16% of the total dissolved nitrogen (inorganic+organic) in Davis fog waters. The median concentration of nitrogen in free amino acids and alkyl amines was 16 μM N (range=3.8–120 μM N), which accounted for 3.4% of the DON in Davis fogs. Thus, although the absolute concentrations of free amino compounds were significant, they were only a minor component of the DON pool. Combined amino nitrogen (e.g., proteins and peptides) was present at higher concentrations and accounted for 6.1–29% (median=16%) of DON. Overall, free and combined amino compounds typically accounted for a median value of 22% of DON in the fog waters.

The high concentrations of DON found, and the fact that amino and other N-containing organic compounds can serve as nitrogen sources for microorganisms and plants, indicate that atmospheric ON compounds likely play an important role in nitrogen cycling in the Central Valley. In addition, due to the basicity of some N functional groups, ON compounds likely contribute to the previously observed acid buffering capacity of Central Valley fog waters. Finally, a comparison of fog waters with fine particles (PM2.5) collected from the same site during the same period of time indicated that the median concentrations (mol N m−3-air) of total water-soluble ON, free amino nitrogen and total amino nitrogen were very similar in the fog water and PM2.5. Given the high water solubility of many organic N compounds, this result suggests that ON might contribute to the hygroscopic properties of atmospheric particles.

Introduction

Intense radiation fog events are common in the Central Valley (CV) of California during winter. These fogs usually form late at night and dissipate 3 or 4 h after sunrise, although they can persist for several days without fully breaking up (Sagebiel and Seiber, 1993). In foggy regions such as the CV, fog events may strongly influence atmospheric chemistry and air quality. For example, fog formation can significantly increase the removal rates of atmospheric particles, accelerate gas to particle partitioning, and lead to reactions in the aqueous phase and at the gas–liquid interface (Blando and Turpin, 2000; Collett et al., 1999a; Fuzzi et al., 1997; Gustafsson and Gschwend, 1999; Hoag et al., 1999; Laj et al., 1997; Lillis et al., 1999; Seinfeld and Pandis, 1998). In addition, since the deposition of fog water can be an important source of water, nutrients, and pollutants, fogs can also play crucial roles in the maintenance and decline of ecosystems, especially in coastal and mountain regions (Finlayson-Pitts and Pitts, 2000; Weathers, 1999).

Understanding the effects of fogs on atmospheric chemistry and ecological health requires detailed information on their chemical composition. While inorganic compounds have been studied extensively in fog waters, relatively little is known about the organic constituents. As shown by previous studies, the concentrations of organic carbon in fog waters can be quite high (Collett et al., 1999b; Facchini et al., 1999; McGregor, 2000). For example, reported levels in samples from the CV range from 420 to 9250 μM C (Collett et al., 1999b; McGregor, 2000). The presence of high concentrations of organic compounds may significantly affect the chemistry and toxicity of fog waters (Blando and Turpin, 2000; Collett et al (1999a), Collett et al (1999b); Facchini et al., 1999; Glotfelty et al (1987), Glotfelty et al (1990); Lo and Lee, 1997; Sagebiel and Seiber, 1993; Schomburg et al., 1991; Suzuki et al., 1998). For example, organic compounds likely contribute considerably to the buffering capacity recently identified in CV fog waters (Collett et al., 1999a). Also, organic species are undoubtedly involved in the chemical reactions that occur in foggy or cloudy atmospheres (Anastasio et al., 1997; Anastasio and McGregor (2000), Anastasio and McGregor (2001); Blando and Turpin, 2000; McGregor and Anastasio, 2001). In addition, the occurrence of surface-active organic materials can cause substantial enrichment of hydrophobic toxic substances, such as pesticides, in fog waters (Glotfelty et al (1987), Glotfelty et al (1990); Sagebiel and Seiber, 1993; Schomburg et al., 1991).

Past studies have found that measured individual organic compounds can only account for a small fraction of the total organic carbon (TOC) in fog waters. For example, in samples from the CV identified low molecular weight carboxylic acids and carbonyl compounds typically accounted for less than 20% of TOC (Collett et al (1999a), Collett et al (1999b)). A complementary approach to studies of individual organic compounds is classification of organic carbon based on functional groups, polarity, or molecular weight (e.g. Anastasio et al., 1997; Decesari et al., 2000; Facchini et al., 1999; Grosjean and Wright, 1983). While this latter approach is more general than compound-specific studies, it typically accounts for a larger fraction of organic carbon and can have important implications for the bulk properties of organic compounds in atmospheric waters. For instance, Facchini et al. (1999) found that ∼40%, on average, of water-soluble organic carbon in Po Valley fog waters was in macromolecular compounds (>500 Da), but analysis for 120 individual organic compounds could only account for less than 5%, on average, of the total dissolved organic carbon.

One broad class of organic compounds that has not been examined yet in fog waters is nitrogen-containing organic compounds. Based on measurements of dry and wet deposition, organic nitrogen (ON) is widespread in atmospheric condensed phases and usually represents a significant portion of the total nitrogen (Anastasio and McGregor, 2000; Cornell et al (1995), Cornell et al (1998), Cornell et al (2001); Jassby et al., 1994; Russell et al., 1998; Scudlark et al., 1998; Timperley et al., 1985). In addition, a number of other studies have shown that amino compounds are also common in atmospheric deposition (McGregor and Anastasio, 2001, and references therein), although the contribution of amino compounds to ON in atmospheric particles or drops has not been previously determined. Based on the chemical and physical properties of amino compounds and other ON functional groups, these compounds could significantly affect the formation and chemistry of fog drops if present in sufficient concentrations.

The overall goal of this study was to quantify and speciate the organic and inorganic nitrogen in fog waters collected from Davis, California. We report here the major results from this study, including: (1) the concentrations and relative amounts of dissolved inorganic and organic nitrogen in fog waters and (2) the contribution of free and combined amino compounds to the pool of ON in the fog waters. Finally, we compare nitrogen data in fog waters with those in co-located PM2.5 samples to explore the potential importance of ON compounds in fog and aerosol processing.

Section snippets

Sample collection and processing

Fog water samples (see Table 1) were collected in Davis, CA, during winters from 1997 to 2001 using a Caltech Active Strand Cloudwater Collector (CASCC2; Demoz et al., 1996). Fog waters were collected directly into high density polyethylene (HDPE) bottles and were filtered (0.45 μm Teflon; MSI Tefsep) right after collection. Filtered samples were stored frozen (−20°C) until analysis. Two cloud waters from Tenerife (Canary Islands) were also studied. To minimize contamination, the collection

Controls

As a check for possible contamination introduced during sample collection and processing, collector rinse waters were collected and analyzed (see Section 2.1). For cations and anions, concentrations in the rinse waters were all less than 10% of the median values in the bulk fog waters (Table 1). Concentrations of DOC in rinse waters ranged from 100 to 400 μM C, except for one rinse water where the aliquot for analysis was apparently contaminated (Anastasio and McGregor, 2001). Excluding this one

Conclusions

We measured considerable amounts of TDN in wintertime fog waters collected in Davis, California. While inorganic nitrogen species, primarily NH4+ and NO3, accounted for the bulk (72–96%) of this fog water nitrogen, DON, measured here for the first time in fog waters, was also a significant component. Concentrations of DON ranged from 120 to 1630 μM N and accounted for 3.9–28% (median=16%) of TDN. Ratios of C : N in the fog water dissolved organic compounds ranged from 1.6 to 12, with a median

Acknowledgements

The authors thank Keith McGregor (UC Davis) for TOC analysis and assistance with fog sampling, Mike Jimenez-Cruz (UC Davis) for assistance with fog sampling, Zengshou Yu (UC Davis) for assistance with sample hydrolysis, Eli Sherman and Jeff Collett Jr. (Colorado State University) for the Tenerife cloud samples, and Tony Andreoni and Dean Bloudoff (California Air Resources Board) for loan of the CASCC2. This work was supported by the U.S. EPA (R819658 and R825433) Center for Ecological Health

References (75)

  • K.J Hoag et al.

    The influence of drop size-dependent fog chemistry on aerosol processing by San Joaquin Valley fogs

    Atmospheric Environment

    (1999)
  • R.G Keil et al.

    Dissolved combined amino acids in marine waters as determined by a vapor-phase hydrolysis method

    Marine Chemistry

    (1991)
  • P Laj et al.

    Cloud processing of soluble gases

    Atmospheric Environment

    (1997)
  • K.G McGregor et al.

    Chemistry of fog waters in California's Central Valley2. Photochemical transformations of amino acids and alkyl amines

    Atmospheric Environment

    (2001)
  • T Nielsen et al.

    Observations on particulate organic nitrates and unidentified components of NOy

    Atmospheric Environment

    (1995)
  • T Novakov et al.

    Chemical composition of Pasadena aerosol by particle size and time of day—III. Chemical states of nitrogen and sulfur by photoelectron spectroscopy

    Journal of Colloid Interface Science

    (1972)
  • K.M Russell et al.

    Sources of nitrogen in wet deposition to the Chesapeake Bay region

    Atmospheric Environment

    (1998)
  • J.R Scudlark et al.

    Organic nitrogen in precipitation at the mid-Atlantic US coast—methods evaluation and preliminary measurements

    Atmospheric Environment

    (1998)
  • K.C Weathers

    The importance of cloud and fog in the maintenance of ecosystems

    Trends in Ecology and Evolution

    (1999)
  • Anastasio, C., 1994. Aqueous phase photochemical formation of hydrogen peroxide in authentic atmospheric waters and...
  • C Anastasio et al.

    Photodestruction of dissolved organic nitrogen species in fog waters

    Aerosol Science and Technology

    (2000)
  • C Anastasio et al.

    Aqueous phase photochemical formation of hydrogen peroxide in authentic cloud waters

    Journal of Geophysical Research-Atmospheres

    (1994)
  • C Anastasio et al.

    Aromatic carbonyl compounds as aqueous-phase photochemical sources of hydrogen peroxide in acidic sulfate aerosols, fogs, and clouds. 1. Non-phenolic methoxybenzaldehydes and methoxyacetophenones with reductants (phenols)

    Environmental Science and Technology

    (1997)
  • N.J Antia et al.

    The role of dissolved organic nitrogen in phytoplankton nutrition, cell biology and ecology

    Phycologia

    (1991)
  • L Ashbaugh et al.

    Loss of Particle Nitrate from Teflon Sampling FiltersEffects on Measured Gravimetric Mass

    (1998)
  • B Barletta et al.

    The NO3 radical-mediated liquid phase nitration of phenols with nitrogen dioxide

    Environmental Science and Technology

    (2000)
  • M.P Buhr et al.

    Contribution of organic nitrates to the total reactive nitrogen budget at a rural Eastern United-States site

    Journal of Geophysical Research-Atmospheres

    (1990)
  • W.E Burnett

    Air pollution from animal wastes, determination of malodors by gas chromatographic and organoleptic techniques

    Environmental Science and Technology

    (1969)
  • K.L Bushaw et al.

    Photochemical release of biologically available nitrogen from aquatic dissolved organic matter

    Nature

    (1996)
  • P Ciccioli et al.

    The ubiquitous occurrence of nitro-PAH of photochemical origin in airborne particles

    Annali Di Chimica

    (1995)
  • Coe, D.L., Chinkin, L.R., Loomis, C., Wilkinson, J., Zwicker, J., Fitz, D., Pankratz, D., Ringler, E., 1998. Technical...
  • J.L Collett et al.

    Spatial and temporal variations in San Joaquin Valley fog chemistry

    Atmospheric Environment

    (1999)
  • S Cornell et al.

    Atmospheric inputs of dissolved organic nitrogen to the oceans

    Nature

    (1995)
  • S Cornell et al.

    Organic nitrogen in Hawaiian rain and aerosol

    Journal of Geophysical Research-Atmospheres

    (2001)
  • S Decesari et al.

    Characterization of water-soluble organic compounds in atmospheric aerosola new approach

    Journal of Geophysical Research-Atmospheres

    (2000)
  • M.C Facchini et al.

    Partitioning of the organic aerosol component between fog droplets and interstitial air

    Journal of Geophysical Research-Atmospheres

    (1999)
  • B.C Faust et al.

    Aqueous-phase photochemical formation of peroxides in authentic cloud and fog waters

    Science

    (1993)
  • Cited by (0)

    View full text