Effects of black carbon on pyrethroid availability in sediment

Area of Science:

• Environmental Chemistry
• Ecotoxicology
• Environmental Science

Background:

• Pyrethroids are hydrophobic, broad-spectrum insecticides with high aquatic toxicity.
• Black carbon (BC) influences the bioavailability of hydrophobic compounds in soils and sediments.
• The impact of BC on pyrethroid bioavailability in sediments remains less understood.

Purpose of the Study:

• To investigate the effect of black carbon on pyrethroid bioavailability in sediments.
• To quantify pyrethroid uptake and bioaccumulation in the presence of varying charcoal concentrations.

Main Methods:

• Simultaneous measurement of pyrethroid uptake using polydimethylsiloxane (PDMS) fibers.
• Assessment of 24-hour bioaccumulation in Chironomus tentans larvae.
• Sediment amendment with charcoal at different rates.

Main Results:

• Pyrethroid accumulation in PDMS fibers showed significant negative correlation with charcoal levels.
• Increased charcoal content (0-1.0%) decreased pyrethroid accumulation in PDMS fibers by 5.7-9.1%.
• A 1.5% charcoal amendment reduced the biota-sediment accumulation factor (BSAF) for permethrin in C. tentans from 2.8 to 1.7.

Conclusions:

• Black carbon exerts a modest effect on pyrethroid bioavailability in sediments.
• Pyrethroid sorption to charcoal was comparable to sediment organic carbon, suggesting limited pore diffusion.
• The large molecular size of pyrethroids may hinder their diffusion into charcoal nanopores, limiting sorption effectiveness.