Simulating Multiwalled Carbon Nanotube Transport in Surface Water Systems Using the Water Quality Analysis Simulation Program (WASP)

Abstract

Under the Toxic Substances Control Act (TSCA), the Environmental Protection Agency (EPA) is required to perform new chemical reviews of nanomaterials identified in premanufacture notices. However, environmental fate models developed for traditional contaminants are limited in their ability to simulate nanomaterials' environmental behavior by incomplete understanding and representation of the processes governing nanomaterial distribution in the environment and by scarce empirical data quantifying the interaction of nanomaterials with environmental surfaces. In this study, the well-known Water Quality Analysis Simulation Program (WASP) was updated to incorporate particle collision rate and particle attachment efficiency to simulate multiwalled carbon nanotube (MWCNT) fate and transport in surface waters. Heteroaggregation attachment efficiencies (α) values derived from sediment attachment studies are used to parametrize WASP for simulation of MWCNTs transport in Brier Creek, a coastal plain river located in central eastern Georgia, and a tributary to the Savannah River. Simulations using a constant MWCNT load of 0.1 kg d in the uppermost Brier Creek water segment showed that MWCNTs were present predominantly in the Brier Creek water column, while downstream MWCNT surface and deep sediment concentrations exhibited a general increase with time and distance from the source, suggesting that MWCNT releases could have increasing ecological impacts in the benthic region over long time frames.

Simulating graphene oxide nanomaterial phototransformation and transport in surface water

“…Brier Creek, GA, located in the eastern US coastal plain, consisting of a mix of urban, agricultural cropland, grassland, forest, and wetland, was selected to investigate GO fate and transport. The river model was established from Bouchard et al 38 using WASP8 and adjusted to this study. Geometry parameters for Brier Creek were parameterized into WASP8 using the BASINS GIS Tool (BASINS 4.1, US EPA), which was used for river segmentation.…”

“…Before running nanomaterial simulations, the Brier Creek WASP8 model was run for the sediment concentration to reach steady state. Dissolved organic carbon (DOC) and other water chemistry parameters were measured as in Bouchard et al 38 River stream segmentation information, river channel geometry data, calibration of sediment transport and flow rate, water quality and chemistry data, and hydraulic residence time of Brier Creek in each segment are available in ESI 1.1-1.3. † Model output interval is set at 1 day.…”

“…Particularly, the mass flow data from GO production to application are scarce. Bouchard et al 38 simulated the fate and transport of multi-walled carbon nanotubes (MWCNTs) in surface waters, using a mass loading of 0.1 kg d −1 estimated based on the mass flow method. Because MWCNTs and GO have similar applications, we assume a similar release of 0.1 kg d −1 for GO.…”

“…The recently updated WASP (WASP8) has a redesigned architecture and incorporates algorithms to simulate the fate of nanoscale and microscale emerging contaminants in surface waters (e.g., nanomaterial's reactions, heteroaggregation). 38 WASP8 can also be linked to spatial analysis and modeling tools (e.g., BASINS, ArcGIS), which can greatly facilitate spatiotemporally explicit modeling and conducting large-scale watershed modeling studies. Previous laboratory studies demonstrated that GO undergoes phototransformation in surface waters, resulting in the production of rGO, carbon dioxide, and other less concentrated low-molecular weight products.…”

Assessment of Water Quality Profile Using Numerical Modeling Approach in Major Climate Classes of Asia

“…QUAL2kw can model the compound interaction between and across organic and inorganic pathways in aquatic conditions. It can capture reactions and the decay process of phytoplankton, nitrate, ammonia, phosphate, DO, BOD, organic phosphorous, and nitrogen concentrations [ 34 , 40 , 41 , 42 ]. The dynamic interactions between nutrient loads from various sources and the consequent longitudinal and lateral water quality pattern in the recipient water body are best described by the WQMs [ 27 , 31 ].…”