Columbus, OH Ohio Sea Grant Researchers Linda Weavers and Richard Sayre of The Ohio State University have developed a process that utilizes an unlikely pair – algae and sound waves – to remove mercury from Lake Erie sediment.
For four years, Dr. Weavers has been using ultrasound, or sonication, to loosen contaminants like PCBs and mercury from sediment. “Sonication uses sound waves to trigger intense chemical, physical, and thermal reactions,” Weavers says. “We realized we could harness the power these reactions create to loosen up contaminants once locked in sediments.”
The process worked very well: within two minutes, 33 percent of the mercury was extracted from the model sediment. However, at 60 minutes, when most of the mercury had been loosened, it began to reattach to the sediment again. So, the search was on to find something that could pull the mercury from the water.
For nearly 15 years, Dr. Sayre has been using a unicellular alga called Chlamydomonas reinhardtii to do a variety of things, including separate heavy metals from Lake Erie sediment, vaccinate Lake Erie fish, and mass produce a bioterrorism antidote. It seemed like the perfect solution to Weavers’ problem.
“Algae are ideal for sequestering heavy metals because they have large surface areas, and they have an intrinsic high metal binding capacity,” explains Sayre. “We were able to increase that capacity by genetically modifying the algae.”
In lab experiments, Weavers and graduate student Ziqi He were able to combine the algae and sonication to extract 30 percent of the mercury in 30 minutes. Further experiments are planned to increase that removal rate.
To read more about this Ohio Sea Grant-funded research, visit http://ohioseagrant.osu.edu/_documents/twineline/v30i1.pdf.