Sulfamate in environmental waters

https://doi.org/10.1016/j.scitotenv.2019.133734Get rights and content

Highlights

  • Information about the occurrence and fate of sulfamate (sulfamic acid) in the environment is lacking.

  • We addressed this science gap by analyzing sulfamate in samples of precipitation, surface water, groundwater and wastewater.

  • Sulfamate was detected in most environmental water samples at concentrations ranging up to 128,000 ng/L.

  • Contextual information obtained in this study suggests that sulfamate detected in environmental waters is derived from various sources.

Abstract

Although sulfamate (the anion of sulfamic acid) has been in use for decades in various industrial and other applications, there is no previously published information about its occurrence and fate in environmental waters. In this study sulfamate was widely detected in environmental waters in Ontario, Canada, ranging up to 128,000 ng/L. It was always detected (>100 ng/L) in bulk precipitation samples and streams, it was usually detected in samples of lake water, and often detected in groundwater. Spatial and temporal variations suggest that both widespread atmospheric deposition and localized land-based anthropogenic sources of sulfamate may be important. Lower concentrations or non-detections of sulfamate in waters that had relatively low dissolved oxygen (e.g. some groundwaters) suggest that sulfamate may be degraded in the environment under suboxic or anoxic conditions. Given our findings of a wide distribution of sulfamate in environmental waters, including precipitation, it is not likely to be very useful as a wastewater tracer.

Introduction

Recently, Castronovo et al. (2017) observed sulfamate (reported as “sulfamic acid”, see Fig. 1 and text below) in municipal wastewater effluent, and suggested that it was a promising candidate as a “wastewater tracer”. They proposed that it might be a more appropriate wastewater tracer than the artificial sweetener acesulfame, of which it is a degradation product (Fig. 1). However, there are other potential sources of sulfamate in wastewater and in various environmental media. For example, since its introduction as an industrial chemical (Cupery, 1938), sulfamic acid and its derivative salts have been widely used for many purposes including as an industrial cleaning agent (Metzger, 2012), a herbicide (ammonium sulfamate: Kamrin and Montgomery, 1999), and as a fireproofing agent (ammonium sulfamate: Lewin et al., 2002).

Furthermore, some laboratory studies have suggested that sulfamate and/or sulfamic acid may form in the atmosphere by reaction of ammonia (NH3) and sulfur trioxide (SO3), particularly in polluted air masses (Shen et al., 1990; Lovejoy and Hanson, 1996; Larson and Tao, 2001; Pawlowski et al., 2003; Pszona et al., 2015) including flue gases (Hirota et al., 1996). There are only a few known biosynthesized organic compounds that contain nitrogen‑sulfur bonds, and the majority of these are classified as sulfamates (i.e. sulfamate is the functional group containing these N–S bonds) (Petkowski et al., 2018). However, whether the degradation of these compounds in nature releases sulfamate to the environment is a knowledge gap.

Sulfamic acid (H3NSO3), which is sometimes referred to as amidosulfonic acid, can be described as a zwitterion (NH3+·SO3) that is readily soluble in water (Metzger, 2012), where it dissociates to form the anion sulfamate (NH2SO3) (Fig. 1). Similarly, sulfamate salts, including ammonium sulfamate, generally have very high solubilities in water. Hence, most references in this paper are to sulfamate rather than sulfamic acid.

Given its extensive production and broad use (including sulfamic acid) for more than seventy years, the fact that it probably forms “naturally” in the atmosphere, and its high solubility in water, sulfamate potentially occurs widely in the environment. Castronovo et al. (2017) found similar concentrations of sulfamate in influent and effluent wastewater indicating that it is relatively stable during municipal wastewater treatment and thus expected to be present in receiving environmental waters. However, there is virtually no published information about concentrations of sulfamate in environmental media. The objective of this paper is to address this knowledge gap by reporting what are, to our knowledge, the first published concentrations of sulfamate in environmental waters. The field sites that were included in this study (Fig. 2) are located in the Province of Ontario in Canada at sites where the authors are currently conducting ongoing aquatic chemistry research and thus could obtain samples readily. We also include analyses of sulfamate in samples of municipal and septic wastewater as contextual information.

Based on laboratory experiments, Scheurer et al. (2012) reported that sulfamate (“amidosulfonic acid”) was one of the main products that formed during oxidation of the artificial sweetener cyclamate by ozone, and sulfamate was also detected as an oxidation product during similar “ozonation” experiments with acesulfame. In subsequent experiments in which the artificial sweetener acesulfame was added to activated sludge from a wastewater treatment plant, Castronovo et al. (2017) reported that sulfamate was the “predominant transformation product” of the degradation of acesulfame. Similarly, in experiments with enrichment cultures of microorganisms derived from wastewater, Kahl et al. (2018) also observed formation of sulfamate associated with degradation of acesulfame. Taking into consideration chemical structures, there is at least one more artificial sweetener that is a potential source of sulfamate via degradation: saccharin (Fig. 1).

Despite some evidence that sulfamate appears to be persistent during treatment of municipal wastewater (Castronovo et al., 2017), laboratory studies have indicated that some microorganisms are capable of degrading sulfamate (Rein and Cook, 1999; Fulton and Cooper, 2005; Linder, 2012).

Bodek and Smith (1980) reported an ion chromatography method for analyzing ammonium sulfamate in air, but to our knowledge no published data for actual air samples have been reported. Pinto et al. (2016) recently reviewed methods to analyze sulfamate as an impurity in pharmaceutical products, and some have measured it as a product of the degradation of the drug topiramate (Li and Rossi, 1995; Pinto et al., 2019). Castronovo et al. (2017) reported an IC-MS/MS method to analyze sulfamate, which they applied to an investigation of wastewater as described above (along with LC/MS/MS for quantitative analysis of acesulfame and IC/QTOF for the identification of the transformation products).

Section snippets

Field sites

The field sites for this study are located in three areas in Ontario, Canada (Fig. 2):

Precipitation data

Over the period August 2017 to January 2019, sulfamate concentrations in bulk precipitation (wet plus dry) in the two rural Upper Thames catchments ranged from 185 to 2583 ng/L (Fig. 3; Table 2). These results indicate that atmospheric deposition plays an important role in transporting sulfamate to surface environments, which may then impact surface water and groundwater. The consistent presence of sulfamate in all precipitation samples suggests that this compound may have formed in the

Conclusions

Sulfamate was detected in almost all of the environmental water samples that were analyzed, ranging in concentration from non-detectable to 128,140 ng/L. Mean concentrations for the various groups of surface water samples discussed in this study ranged from 140 to 24,000 ng/L. Sulfamate was detected in all of the precipitation samples, and was found in >99% of the surface water samples at urban and rural sites, and sites relatively remote from development areas.

Lowest concentrations and

Declaration of competing interest

The authors have no competing interests to declare.

Acknowledgements

The following people from Environment and Climate Change Canada (ECCC) assisted with collection of environmental water samples: Ross MacKay (all sites), Pam Collins (Upper Thames), Tim Pascoe and Tana McDaniel (Lake of the Woods). Steve Teslic, Korey Broad and Alexandra Auyeung of ECCC collected the municipal wastewater samples. Michael Saunders (Nottawasaga Valley Conservation Authority) assisted with collection of the groundwater samples at the Minesing Wetlands. Pam Collins (ECCC) conducted

References (46)

  • A.L. Bradford

    A Hydrobiological Study of Minesing Swamp, Ontario

    (1999)
  • I.J. Buerge et al.

    Ubiquitous occurrence of the artificial sweetener acesulfame in the aquatic environment: an ideal chemical marker of domestic wastewater in groundwater

    Environmental Science & Technology

    (2009)
  • Buerge, I.J., Keller, M., Buser, H.-R., Müller, M.D., Poiger, T. 2011. Saccharin and other artificial sweeteners in...
  • M. Cupery

    Sulfamic acid: a new industrial chemical

    Industrial & Engineering Chemistry

    (1938)
  • A.M. De Sellas et al.

    State of the Lake Report for Lake of the Woods and Rainy River Basin

    (2009)
  • C.K. Fulton et al.

    Catabolism of sulfamate by Mycobacterium sp. CF1

    Environ. Microbiol.

    (2005)
  • K. Hirota et al.

    Reactions of sulfur dioxide with ammonia: dependence on oxygen and nitric oxide

    Industrial Engineering & Chemistry Research

    (1996)
  • S. Kahl et al.

    Emerging biodegradation of the previously persistent artificial sweetener acesulfame in biological wastewater treatment

    Environmental Science & Technology

    (2018)
  • M.A. Kamrin et al.

    Agrochemical and Pesticide Desk Reference on CD-ROM

    (1999)
  • L.J. Larson et al.

    Interactions and reactions of sulfur trioxide, water, and ammonia: an ab initio and density functional theory study

    J. Phys. Chem. A

    (2001)
  • M. Lewin et al.

    The system polyamide/sulfamate/dipentaerythritol: flame retardancy and chemical reactions

    Polym. Adv. Technol.

    (2002)
  • W. Li et al.

    Determination of sulfamate and sulfate as degradation products in an antiepileptic drug using ion chromatography and indirect UV detection

    J. Liq. Chromatogr.

    (1995)
  • T. Linder

    Genomics of alternative sulfur utilization in ascomycetous yeasts

    Microbiology

    (2012)
  • Cited by (7)

    • Groundwater contributions to surface water in the Assiniboine Delta Aquifer (ADA): A water quantity and quality perspective

      2021, Journal of Great Lakes Research
      Citation Excerpt :

      Artificial sweeteners and pesticides were analysed using a Dionex (Sunnyvale, CA, USA) 5000 ion chromatography (IC) system coupled to a QTRAP 5500 (AB Sciex, Concord, ON, CAN) triple-quadrupole mass-spectrometer. Van Stempvoort et al. (2019) give the general instrument details used for all analytes and the MS compound specific parameters for acesulfame, saccharin and cyclamate. MS compound specific details for sucralose and glyphosate are presented in Van Stempvoort et al. (2014) and Van Stempvoort et al. (2020), respectively.

    • Organic contaminants of emerging concern in leachate of historic municipal landfills

      2021, Environmental Pollution
      Citation Excerpt :

      Finally, sulfamic acid is a high-production volume chemical with a large list of uses in multiple industries (Freeling et al., 2020). Though there are few studies on the presence of this highly water-soluble compound (sulfamate in its anionic form) in the environment, it has been found at concentrations of typically 0.1s–10s μg/L in precipitation, groundwater, surface waters, and drinking waters, and 10s–1000s μg/L in WWTP effluent (Castronovo et al., 2017; Van Stempvoort et al., 2019; Freeling et al., 2020). Here, the maximum concentration reached 42 μg/L in one of the younger historic landfills (MR), while 18 samples surpassed 1 μg/L, indicating that historic landfills can be a source of elevated sulfamic acid to environmental waters.

    • Under the radar – Exceptionally high environmental concentrations of the high production volume chemical sulfamic acid in the urban water cycle

      2020, Water Research
      Citation Excerpt :

      Since municipal WWTP effluent concentrations of sulfamate in Germany are typically in the high μg/L-range (see 3.1), it is reasonable to assume that for most wastewater-impacted surface waters in Germany the introduction of sulfamate by diffuse sources (atmospheric deposition) is greatly exceeded by WWTP effluents. These findings are in contrast to the results obtained by van Stempvoort et al. (2019). In their study, the authors assumed that sulfamate detected in environmental water samples from Ontario, Canada, was mostly originating from non-wastewater sources.

    View all citing articles on Scopus
    View full text