In situ Treatment with Activated Carbon Reduces Bioaccumulation in Aquatic Food Chains

Abstract

In situ activated carbon (AC) amendment is a new direction in contaminated sediment management, yet its effectiveness and safety have never been tested on the level of entire food chains including fish. Here we tested the effects of three different AC treatments on hydrophobic organic chemical (HOC) concentrations in pore water, benthic invertebrates, zooplankton, and fish (Leuciscus idus melanotus). AC treatments were mixing with powdered AC (PAC), mixing with granular AC (GAC), and addition-removal of GAC (sediment stripping). The AC treatments resulted in a significant decrease in HOC concentrations in pore water, benthic invertebrates, zooplankton, macrophytes, and fish. In 6 months, PAC treatment caused a reduction of accumulation of polychlorobiphenyls (PCB) in fish by a factor of 20, bringing pollutant levels below toxic thresholds. All AC treatments supported growth of fish, but growth was inhibited in the PAC treatment, which was likely explained by reduced nutrient concentrations, resulting in lower zooplankton (i.e., food) densities for the fish. PAC treatment may be advised for sites where immediate ecosystem protection is required. GAC treatment may be equally effective in the longer term and may be adequate for vulnerable ecosystems where longer-term protection suffices.

Equilibrium and kinetic modeling of contaminant immobilization by activated carbon amended to sediments in the field

“…Details of the activated carbon remediation field experiment have been published in our previous paper that addressed effects of AC treatments on bioaccumulation Kupryianchyk et al (2013aKupryianchyk et al ( , 2013b and are provided as Supporting Information. Here, a brief summary is given and model details are described.…”

“…Tsurumi Pump KTV2-80 (400 V, 50 Hz, 3-phase 80 mm hose coupling) were used for direct mixing. Industrial sieves (1.6 Â 1.0 m, mesh size 20 and 1 mm) were used for sediment pretreatment Kupryianchyk et al (2013aKupryianchyk et al ( , 2013b. Biesbosch sediment was diluted with groundwater to 20% d.w., sieved over a 20 mm sieve and homogenized for 4 h, after which one-fourth of the sediment slurry was pumped into ditch 1 ('sediment treatment control') and one-fourth of the sediment into ditch 2.…”

“…For a recent field scale remediation trial we demonstrated that 48 h mixing of sediment and granular AC (GAC) resulted in a reduction of PAH pore water concentration by 97% in the short term (Kupryianchyk et al, 2013a). The longer term efficiency of sediment stripping, i.e.…”

“…Several field trials showed the high effectiveness and functionality of AC deployments in reducing aqueous phase concentrations Cho et al (2009Cho et al ( , 2007, Cornelissen et al (2011), Hale et al (2012), sediment-to-water fluxes and thus mobility of HOCs Ghosh et al (2011), Beckingham and Ghosh (2013). Further benefits are reduced bioaccumulation of PCBs into benthic invertebrates and fish Ghosh et al (2011), Cho et al (2009), Beckingham and Ghosh (2011), Janssen et al (2011), Kupryianchyk et al (2013a), and reduced toxicity of contaminated sediments Burgess et al (2009), Ho et al (2004, Kupryianchyk et al (2011). Consequently, AC may serve as an effective tool in risk mitigation and remediation of contaminated sediments.…”

“…addition, mixing and subsequent removal of GAC, relies on the extraction efficiency of the removed GAC fraction, the ongoing HOC sequestration by the residual GAC fraction and the possible formation of smaller sediment and GAC fractions due to turbulence in the 48 h mixing stage Rakowska et al (2013), Rakowska et al (2014). As for powdered AC (PAC), addition to sediment has been shown to reduce bioaccumulation of PCBs by benthic invertebrates, zooplankton, fish, and macrophytes even by 95% Kupryianchyk et al (2013a).…”