As a member of the EOS group, Jan has been assisting field work in maars near Pleiku City in the Central Highlands of Vietnam since 2016. He built a lightweight and inexpensive core recovery device named “autonomous sediment corer with pneumatically operated core catcher”for use in remote regions and in developing countries like Vietnam. Jan also assisted in measuring environmental radon geohazards in caves and earthen dwellings in Hà Giang province. Below are a few pictures highlighting Jan’s activities.
Jan and Arndt deployed our first gravity corer in Biển Hồ maar lake in March 2016, our first coring expedition. The assembly was made from a bamboo rod tied to a core liner. Bricks were attached to the top of the core liner for additional weight. A small steel rod acted as a hammer.Jan holds PVC pipes used to manually lower the corer to a depth within the sediment of Biển Hồ lake during our first coring expedition in March 2016. The translucent core liner with a traditional plastic core catcher was attached to the end of a sequence of threaded PVC pipes that were lowered from a boat.Jan and fellow EOS team members recovered an exploratory 0.5-m sediment core from a depth of ~14 m from Biển Hồ lake during our first coring expedition in March 2016. Most importantly, a bacterial mat covering the sediment/water interface was documented.After hours of hard work, we lost a sediment core due to clumsy handling in March 2016. Afterwards, Jan carried an ‘anchor stone’ from the shore onto the rickety ramp of a boat where he slipped and cut his chin on a piece of sharp metal. He was brought to a local Vietnamese Army Hospital and received six expert stitches.In December 2016/ January 2017, Jan and the EOS group cored in a rice field located in a dry maar in the south of Pleiku City. The maar resisted coring with a very hard, cement-like layer at a depth of less than a meter. We later learned that such a compacted layer is a typical result of centuries of rice farming.Jan checks his GoPro underwater video camera before lowering the coring assembly into Biển Hồ maar lake in December 2016. Built by Jan, the coring assembly was named “autonomous sediment corer with pneumatically operated core catcher”.
Jan and Arndt are holding a newly recovered sediment core from Biển Hồ maar lake in December 2016. The autonomous sediment corer with pneumatically operated core catcher proved to work well in more than 20 meters of water. Our field work yielded half a dozen 50 to 70-cm long sediment cores with the help of Jan’s coring device.Jan and Hướng wade slowly to the center of the Plei Ốp swampy maar near Pleiku City for exploratory coring in January 2017. Jan was selectively attacked by leeches and donated plenty of blood while he was partially submerged in the swamp.Jan and fellow EOS members test Hoàng’s newly designed piston corer in a shallow pond in a Hà Nội suburb in November 2017. Later, the device yielded wonderful cores from Biển Hồ maar lake from a depth of up to 21 m. The deepest core reached 3.5 meter into the sediment. Jan helps EOS member Nguyệt to attach the transducer of our Garmin STRIKE 4 fishfinder echo-sounding apparatus in preparation for a depth survey in Biển Hồ maar lake during our third coring expedition in November 2017. Jan had bought the fishfinder in the USA in 2016. The instrument provided reliable bathymetric data throughout our three coring expeditions. Bathymetric maps assisted in our selection of coring sites in Biển Hồ maar lake.Jan connects a plastic tube to the inflatable bladders that are part of the core catcher. The two bladders are joined by a Y-connector allowing a single 25-m long plastic hose to connect to a T-valve. Upon inflation of the bladders with water from a 500 mL plastic syringe, the rubber bladders bulge into the core catcher and block spillage of sediment.Jan’s sediment coring design was extremely helpful in recovering short lacustrine sediment cores that preserved an undisturbed sediment/water interface. The autonomous and gentle descent of Jan’s device through the water column made it unnecessary to firmly anchor the coring platform. His affordable methodology is attractive for developing countries and work in remote regions where limited resources and challenging logistics prevent the use of heavy coring equipment.Jan is working with the coring team to recover a piston core from Biển Hồ during November 2017. Piston coring of deeper sediment requires secure anchoring of the platform. Two days of field work yielded 17 wonderful piston and gravity cores from up to 21 m water depth and penetrating up to 3.5 m into the sediment. After a coring day, Jan rows back to assembly site in the late afternoon, the third expedition in Biển Hồ maar lake, November 2017.After cutting the core liner laterally with a circular saw on opposite sides in the EOS lab at VNU, the core is placed horizontally between two inclined aluminum bars. Jan, Arndt and Hướng are using cathodically charged stainless-steel blades to split the sediment in a core recovered from Biển Hồ maar lake in November 2017. The negatively charged stainless-steel blades deposit a film of hydrogen gas on the metal to lubricate the blade’s entry into the sticky sediment.Jan is aiming to take photographs of his “autonomous gravity corer with pneumatic core catcher” at VNU Hanoi, December 2017, for his future publication. Jan had also helped to measure environmental radon geohazards in the air of caves and homes in Hà Giang province and Hanoi. Above: Jan and other EOS members are relaxing in front of an ancient mud-built house that serves as a restaurant in Đồng Văn town, Hà Giang, in March 2016. Our group first discovered high thoron (220Rn) concentrations in this house behind a plastic tarp.Radioactive radon gas is being generated in soil from uranium and thorium trace metals. Dry, porous mud walls and floors in mud-built homes emit radon into room air. Two radon isotopes and their radioactive decay products cause radiation damage in lung tissues. The longer-lived radon-222 with a half-life of ca. 3.8 days can be effectively diluted by exchanging room air with outside air. In contrast, the radiation geohazard from radon-220 (thoron) with a half-life of only ca. 55 seconds can only be mitigated by sealing of porous surfaces. Above: Jan digs a hole in a plowed field in Ha Giang in March 2016 in preparation for the collection of radon-containing soil gas.Jan and fellow EOS members pose in front of newly built mud-house in a Hanoi suburb in November 2017. The model mud-house was specifically built for scientific experiments aiming at (1) developing recommendations for affordable and reasonable detection methods for radon and thoron in mud-built homes; (2) assessing the concentrations and distributions of thoron and radon in mud-house air; (3) devising affordable, non-toxic and socially acceptable methods for sealing of porous mud surfaces in homes to mitigate the radiation geohazard and to improve public health.
Geosciences are improving the lives of people in Vietnam
