Guang-ming Zhao, Si-yuan Ye,*, Hong-ming Yuan, Shi-xiong Yang, Lei He,Ewar A.Laws

a Key Laboratory of Coastal Wetlands Biogeosciences, China Geologic Survey, Ministry of Natural Resources, Qingdao 266071, China

b Laboratory for Marine Geology, Qingdao National Laboratory for Marine Science and Technology, Ministry of Natural Resources, Qingdao 266061, China

c Qingdao Institute of Marine Geology, China Geologic Survey, Ministry of Natural Resources, Qingdao 266071, China

d School of the Coast &Environment, Department of Environmental Sciences, Louisiana State University, Baton Rouge, LA 70803, USA

1.Objective

The problems associated with traditional equipment for sampling shallow drilling sediment cores include high production cost, short sample preservation time, inability to store in a freezer, and poor resistance to seawater corrosion(Table 1).We developed a sampler with a new design that overcame these problems.The new design worked well in our study and can efficiently support coastal wetland geological surveys.

Table 1.Brief comparisons between semi-open tubular stainless steel sampler and the new design.

2.Methods and results

The newly designed equipment for sampling undisturbed and shallow drilling sediment cores consists of four major components (Fig.1A): a sealed bag, a pipe, the sharpened end of the pipe and the pipe cap.The inner diameter of the pipe(Fig.1A-b) is 75-100 mm and the length is 60-120 cm.The pipe (Fig.1A-b) can be made of plexiglass or PVC.Fig.1B shows a cross-section of the sampling pipe.

Fig.1.Sampling equipment (A) (a-Sealed bag; b-pipe; c-sharpened end; d-pipe cap) and cross-section of the sampling pipe (B).

The samples obtained from shallow drilling sediment cores can be used to estimate sedimentation accumulation rates (Ward RD et al., 2014; Zhou L et al., 2016) and for geochemical analyses that reveal the geological history of the core (Zhao Q et al., 2016) and historical geological events(Liu Z et al., 2013).

Fig.2 shows a flow diagram of the newly designed sampler.One end of the plexiglass or PVC pipe should be sharpened to facilitate driving the pipe into the sediment.A piece of wood is placed on top of the pipe, and the wood is hit with a hammer to drive the sharpened end of the pipe into the soil.The width of the wood should not exceed the diameter of the pipe mouth (Fig.2b).After the pipe has been driven into the soil, a sealing bag is placed on top of the pipe (Fig.2c),and the air between the sealing bag and the surface layer of the soil sample inside the pipe is discharged.The sealing bag is wrapped tightly around the outer wall of the pipe with tape to ensure that no air gets into the sealing bag.At this time,there is a small vacuum between the sealing bag and the upper part of the soil inside the pipe.A rope is wrapped around the outer wall of the pipe, and the pipe is lifted with the soil samples out of the ground (Fig.2d).Because the pressure at the top of the pipe is much lower than the outside atmospheric pressure, the soil samples remain inside the pipe under the outside atmospheric pressure, even when the pipe is pulled out of the ground.Finally, both ends of the pipe are sealed with a sealing bag or a cap that matches the pipe diameter(Fig.2e).Compared with traditional sampling equipment, this new sampler can increase the core recovery of 15%-20%.

Fig.2.Flow diagram of newly designed sampler.a-Get ready for sampling; b-drive the sampler into the soil; c-vacuum the pipe;d-lift up the sampler; e-seal the sampler.

3.Conclusion

In this study, a sampler with a new design for collecting undisturbed samples from a shallow drilling sediment core was developed and used in our wetland fieldwork.This sampler with low production cost, long sample preservation time, ability to store in a freezer, good resistance to seawater corrosion and high core recovery, can support field studies and geological investigations in coastal wetland geological survey projects, and it can be upgraded with the development of new technology as well.

Acknowledgement

This equipment has obtained the national invention patent and the patent number is ZL 201520003115.0 (Fig.3).This study was jointly funded by the Natural Science Foundations of China (41406082, 41240022, 41706057), National Key R&D Program of China (2016YFE0109600), and Governmental Public Research Funds of China (201111023,DD20189503 and GZH201200503).

Fig.3.Certificate of patent.