Environmental transformation of natural and engineered carbon nanoparticles and implications for the fate of organic contaminants

Abstract

Environmental transformations of natural and engineered carbon nanoparticles significantly affect their fate, transport, and interactions with organic contaminants.

NO2 and natural organic matter affect both soot aggregation behavior and sorption of S-metolachlor

“…This indicates that in addition to electrostatic repulsion, steric effects might also play a role in the aggregation of soot in the presence of NOM. 4 In good agreement with DLS measurements and particle mass remaining in suspension, scanning electron microscopy images conrmed the higher number and smaller size of suspended particles for NO 2 transformed soot compared to pristine soot. The stabilizing effect of NOM on soot aggregation could also be observed when comparing suspensions with and without NOM (Fig.…”

“…It should be noted that relatively high soot concentrations were used in this study, and in many scenarios hetero-aggregation with other suspended particles in the natural environment is expected to outweigh the importance of the homo-aggregation investigated here. 4,31,32 However, the investigation of hetero-aggregation was not in the scope of this study and may be an interesting subject of further investigations building on the results presented here.…”

“…3 Thus, soot emissions are expected to be at least 10 4 times more abundant compared to widely studied engineered CNPs including graphene oxides, fullerenes and carbon nanotubes. 4 Once released into the atmosphere, soot can undergo chemical transformation, resulting in changes in the surface chemistry. Key processes for atmospheric soot transformation are photochemical redox reactions with NO x , SO x , O 3 and other reactive oxygen species in the atmosphere.…”

“…The aggregation behavior of soot is expected to depend mainly on the soot surface charge, the presence of natural organic matter (NOM), and the ionic composition of the aqueous environment. 4 A recent study by Chen et al 9 found that soot aggregation followed classic Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, [10][11][12] describing the aggregation behavior of particles as a combination of van der Waals attraction and electrostatic repulsion. Depending on the aqueous chemistry, soot particles can remain stable against homo-aggregation in typical freshwater environments but are likely to aggregate under saline conditions (e.g.…”

“…But with an increasing negative surface charge and the presence of NOM soot particles are expected to form increasingly stable suspensions. 4 In the water phase, soot has a strong adsorption affinity for a range of organic contaminants, [13][14][15][16] and because of its higher abundance compared to other CNPs, soot may signicantly alter the fate of organic contaminants occurring in surface waters. From other CNPs it is known that the presence of NOM strongly affects particle aggregation and size and may also inuence the sorption of organic contaminants due to changes in accessibility of sorption sites.…”