Preliminary hydrogeological observations in Phong Nha–Ke Bang National Park and Tu Lan Karst Area, Quang Binh Province, Vietnam

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Publication Date

June 2020

Abstract

Preliminary hydrogeological and geochemical observation were conducted in the Phong Nha—Ke Bang National Park and Tu Lan Karst Area, Quang Binh Province, Vietnam to evaluate and document the hydrogeologic conditions, karst surface features, water geochemistry and limestone composition. The study area provides an excellent benchmark for karst hydrogeological investigations in central Vietnam. The data generated from this project will guide future research and conservation efforts of this unique karst landscape. Five rock samples and 20 water samples were collected in 2016. Four of the five rock samples are pure limestones, easy to dissolve which combine with a well-developed secondary porosity, and large amount of rain, forms a good environment for karst landscape and cave formation. There is a significant variation between 20 study sites in water chemistry baseline, specific conductance and temperature. The water samples had slightly acidic-to-neutral pH values (6.15–7.91), moderate specific conductance (SC) and total dissolved solids (TDS) values 65–418 μS/cm and 32–209 milligrams per liter (mg/L), respectively. Temperatures varied from 17.9 to 22.8 ºC. ORP ranged from 68 to 194 at Phong Nha Cave outlet. Total alkalinity as CaCO3 fluctuates between 38 mg/L and 166 mg/L and total hardness ranged between 28 mg/L and 248 mg/L CaCO3. All samples exhibit slightly elevated chlorite, nitrate, and sulphate levels.

Keywords

Hang (Cave), Karst Spring, Carbonate Rocks, Hydrogeology, Stable Isotopes, Tower Karst

Document Type

Article

Notes

Carbonates and Evaporites, Vol. 35 (2020-06-10).

Identifier

SFS0070001_00001

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