Uptake of tributyltin into willow trees

Area of Science:

• Environmental Chemistry
• Plant Science
• Bioremediation

Background:

• Organotins, like tributyltin (TBT), were widely used as antifoulants in ship paints, causing severe aquatic ecosystem damage.
• Regulations have restricted organotin use and disposal, prompting exploration of alternative remediation strategies like land-based disposal of contaminated sludge.

Purpose of the Study:

• To investigate the potential of phytoremediation for tributyltin (TBT) contamination using willow trees.
• To evaluate the influence of pH on the sorption, uptake, and translocation of TBT in willow trees.

Main Methods:

• Investigated the sorption and uptake of tributyltin chloride (TBTCl) and tributyltin hydride (TBTH) in willow trees across a pH range of 4-7.
• Analyzed TBT concentrations in plant tissues and solutions using atomic absorption spectroscopy (AAS) with a graphite oven.
• Measured sorption to living and dead roots, stems, and leaves in shaking experiments.

Main Results:

• TBT concentrations in solutions with trees decreased rapidly, with highest TBT content found in roots and lower stems.
• Sorption to roots and leaves was less affected by pH, while sorption to stems increased with pH and with dead tissue.
• Limited translocation of TBT to higher stems or leaves was observed, with pH having minimal effect on plant uptake.

Conclusions:

• Phytoextraction of TBT by willow trees is not feasible due to strong sorption of the TBT+ cation to plant tissues and lack of effective translocation.
• An ion trap mechanism for TBT accumulation in xylem was not detected.
• While direct phytoextraction is limited, planting trees may offer indirect remediation benefits through soil aeration.