Surfactant toxicity to Artemia franciscana and the influence of humic acid and chemical composition

Abstract

Surfactants can be extremely toxic to aquatic species and are introduced to the environment in a variety of ways. It is thus important to understand how other environmental constituents, in this case humic acids (HAs), may alter the toxicity of anthropogenic surfactants. Hatching and mortality assays of Artemia Franciscana were performed for three different toxic surfactants: Triton X-100 (Tx-100, non-ionic), cetylpyridinium chloride (CPC, cationic), and sodium dodecyl sulfate (SDS, anionic). Humic acids of varying composition and concentrations were added to the assays to determine the toxicity mitigating ability of the HAs. Tx-100 had a significant toxic effect on Artemia mortality rates and HAs from terrestrial sources were able to mitigate the toxicity, but an aquatic HA did not. CPC and SDS limited hatching success of the Artemia and, as HAs were added, the hatching percentages increased for all HA sources, indicating toxicity mitigation. In order to determine which functional groups within HAs were responsible for the interaction with the surfactants, the HAs were chemically modified by: (i) bleaching to reduce aromatics, (ii) Soxhlet extraction to reduce lipids, and (iii) acid hydrolysis to reduce O- and N-alkyl groups. Although most of the modified HAs had some toxicity mitigating ability for each of the surfactants, there were two notable differences: 1) the lipid-extracted HA did not reduce the toxicity of Tx-100 and 2) the bleached HA had a lower toxicity mitigating ability for CPC than the other modified HAs.

Influence of surfactants and humic acids on Artemia Franciscana's embryonic phospho-metabolite profile as measured by 31P NMR

“…Surfactants used in household and industrial applications are typically nonionic, cationic, or anionic (Ivanković and Hrenović 2010). Due to their heavy use, surfactants inevitably end up in the environment via run-off, waste water treatment plants, remediation treatments, and pesticide formulations (Deese et al 2016). The potential toxicity of surfactants to aquatic organisms depends on the organism, the surfactant type, and surfactant structure.…”

“…Furthermore, humic acids (HAs), which are omnipresent in the environment, have been shown to mitigate the toxicity of a range of pollutants, including surfactants (Deese et al 2016, Koopal et al 2004). HAs are complex heterogeneous organic molecular assemblies formed by the degradation of organic matter.…”

“…These interactions are dependent on both the type of the HA and the pollutant. Previous Artemia Franciscana ( Artemia ) hatching assays have shown that surfactant toxicity can be mitigated by HAs and that mitigation is based on electrostatic interactions, π-π interactions, and the amphiphilic functionality of the HA (Deese et al 2016). …”

“…Pollutant toxicity to Artemia has been studied for a range of toxicants, including (but not limited to) surfactants (Deese et al 2016), oil dispersants (Rodd et al 2014), pharmaceuticals (Nunes et al 2005), pesticides (Venkateswara Rao et al 2007), metals (Kokkali et al 2011), and nanoparticles (Arulvasu et al 2014, Rajabi et al 2015). Adverse conditions, such as a polluted environment, can cause significant changes and inhibitions of an embryo's development as well as retard growth after hatching.…”

“…It was previously found that triton X-100 (Tx-100) causes mortality after hatching, cetylpyridinium chloride (CPC) and sodium dodecyl sulfate (SDS) inhibit hatching, and HAs can mitigate these toxic effects (Deese et al 2016); however, questions remained in regards to the toxicity mechanism of CPC and SDS and whether toxicity could be measured in real time. In this study, we utilized 31 P NMR to address the following questions: 1) can surfactants measurably change the phospho-metabolite profile of the Artemia embryos, 2) can these changes be measured in real time, 3) are the toxicity mechanisms based on membrane disruption or a growth inhibition, and 4) can the toxicity mitigation by HA be measured by 31 P NMR?…”