The Chinese icebreaker vessel Xuelong completed China's 35th research mission to Antarctica and returned to Shanghai safely on March 12.

Among the 349 members aboard, more than 10 were from research institutions based in Qingdao, Shandong province.

Qingdao is at the forefront of marine science and technology. It is home to more than 30 percent of China's universities and research institutes, 50 percent of its researchers and 70 percent of top experts and academicians in the fields of marine science and technology.

Three researchers recalled their experience during their 131-day expedition.

Zheng Li: walk 40,000 heavy steps per day

Zheng Li, a researcher from the No 1 Marine Institute of the Ministry of Natural Resources, does sampling work while penguins stagger around him during China's 35th research mission to Antarctica. [Photo provided by chinadaily.com.cn]

Zheng Li is a deputy director of the Marine Ecology Research Center at the No 1 Marine Institute of Ministry of Natural Resources. He was responsible for collecting heavy metals and organic pollutants and taking samples 42 days in a row.

Every morning he set out from Changcheng Station on the Fildes Peninsula with his colleagues and returned with samples weighing more than 10 kilograms at around 7 pm.

"My pedometer showed I walked 40,000 steps a day and my legs felt numb," Zheng recalled.

Though the work is arduous, he enjoyed spending time with penguins on Adelie Island.

"When I put the samples into containers, it was funny to see a group of penguins staggering around me and staring at my containers curiously," he said.