AHW19-01

Japan Geoscience Union Meeting 2016

Study on the mechanism of soil and groundwater contamination by 1,4-Dioxane*Makoto Nakashima1, Ray Uwe Hidaka1
1.Kokusai Kogyo Co., Ltd.
It is planned to implemented the Environmental Quality Standard (EQS) for soil pollution of
1,4-Dioxane (DXA) in Japan soon. DXA (C2H8O2) has a density similar to that of water at room
temperature and is a colorless and transparent liquid. It has a relatively low boiling point at101℃, dissolves well in both water and oil, and belongs to the group of volatile organic compounds(VOC). Due to these characteristics DXA is a widely used solvent and was used in large amounts asstabilizer for 1,1,1-Trichloroethane (MC). It is assumed that DXA has a low affinity to adsorb on
organic substances within the soil matrix, has a lower volatilization rate and is hence highly
mobile. Therefore, it is likely that its soil and groundwater contamination mechanism is different
compared to other VOC.
In this study, in order to understand the behavior characteristics of DXA in soil and groundwater,
as well as soil and groundwater contamination mechanism, distribution experiments regarding DXA
between solid-liquid phase and liquid-gas phase as well as three kinds of soil column experiments
were conducted. Toyoura sand and organic soil were used for all experiments respectively. The
results of these experiments about the behavior of DXA were compared to that of MC which often
occurs together with DXA.
DXA was almost only present in pore water in the distribution experiments, and only a small amountadsorbed on soil particles or vaporizes into the gas phase. In case that MC was present as NAPL inwater, the presence of MC phase did not affect the distribution of DXA.
Soil column experiments in order to understand the volatilization in unsaturated soil showed thatDXA which vaporized from contaminated soil dissolves in soil water while spreading upwards throughthe soil gas, in case that DXA is present in the unsaturated soil. Therefore, the probability ofDXA to spread until close to the soil surface through soil gas is low, and it was further shown thepossibility that soil leachate values exceed the EQS for soil pollution in intermediate depths.
Further soil column experiments, in order to understand the infiltration properties during
precipitation into the unsaturated soil, showed that DXA in the unsaturated zone will dissolve ininfiltrating rain water and percolate with it; however, in case that rain water does not infiltrate
into the unsaturated soil, the concentration of DXA remains high within the soil matrix. Hence it
is likely that at places where rain water infiltration does not occur, such as under buildings, theconcentration of DXA in the unsaturated soil remains high within the soil matrix and that DXA canbe mobilized after demolition of buildings through infiltrating rain water until it reaches theaquifer where it may cause groundwater contamination.
In this research, DXA specific soil and groundwater contamination characteristics were examined byunderstanding the behavior characteristics of DXA in the unsaturated zone.
The content of this presentation was partly funded by the Environmental Research and Technology
Development Fund (5-1503) of the Ministry of the Environment, Japan.
Keywords: 1,4-Dioxane, soil and groundwater contamination, contamination mechanism, unsaturated
soil, soil column experiment©2016. Japan Geoscience Union. All Right Reserved.

- AHW19-01 -AHW19-02

Japan Geoscience Union Meeting 2016

Hydrochemical and isotopic composition of groundwater in Douala, Cameroon: Effect ofrecharge and waste water on water contamination*Mengnjo Jude Wirmvem1, Takeshi Ohba1, Brice Tchakam Kamtchueng2, Wilson Yetoh Fantong2, Muga
Yaguchi1, Mumbfu Ernestime Mimba1,2, Tasin Godlove Bafon3, Gloria Eneke Takem2, Ako Andrew Ako2
1.Sch. of Sci, Tokai Univ., 2.IRGM, Cameroon, 3.Compagnie Minière Du Cameroun SA
High water demand for domestic use in the Douala urban city with over 3 million inhabitants is met
mainly by shallow groundwater through shallow wells, boreholes and springs in Pleistocene alluvium
and Pliocene sand deposits. Chemical controls and recharge process of the groundwater have not beenthoroughly investigated. Accordingly, this study examines the main controls on groundwatercomposition and spatial view of its contamination, timing of recharge and link between the recharge
process and quality of the water. Conventional field measurements in January 2015 were followed byanalysis of major ions and stable hydrogen and oxygen isotopes in 52 water samples. A significant
range of EC values from 15 to 6890 µS/cm in both surface water and the groundwater suggests variouscontrols on the chemical composition of the water. Low pH values in the groundwater from 3.61 to
6.92 with an average value of 5.04 indicate an acidic aquifer. The water types were Na-Cl, Ca-Mg-SO
4-Cl,

Ca-Mg-HCO3 and Na-HCO3 with the Na-Cl water type being the most dominant in shallow open

wells, boreholes and springs. Despite the nearness to the sea, only the River Wouri and few
groundwater samples were strongly affected by salinization. Nitrate, which exceeded the WHO guidevalue of 50 mg/l in 22 % of the groundwater, poses a health problem, particularly infant
methaemoglobinaemia. Mass ratios of Cl/Br in the groundwater ranged from 54 up to 3249 (with anaverage value of 652). The ratios scattered mostly along the mixing lines between dilute waters,
septic-tank effluent and domestic sewage. The majority of samples especially the high NO3- shallow
open wells clustered around the septic-tank effluent end member. This cluster indicates thatshallow groundwater in the urban city of Douala is highly contaminated by seepage from the numerous
and widely distributed pit latrines. The stable isotopes in the groundwater indicated its meteoric
origin and rapid infiltration after rainfall. Most groundwater samples plotted between
precipitation in the months of April and August along the Douala meteoric line showing no isotopic
signatures of the most depleted and heaviest September to October monsoon rains. The narrow plotsuggests a timing of the main recharge between the April and August rains and no considerable
variation in recharge conditions during the hydrological year. The δ18O values showed narrow ranges
and overlaps in rivers (-3.10 to -2.13 ‰), springs (-3.09 to -2.90 ‰), shallow wells (-3.79 to-2.47 ‰), and boreholes (-3.53 to -2.88 ‰) with an even spatial distribution. These observations
depict hydraulic connectivity, good water mixing and a homogeneous aquifer system mainly receiving
local diffuse/direct uniform areal recharge from rainfall. The rapid and diffuse recharge throughthe permeable alluviums and sands favour the leaching of effluent from the pit latrines into theaquifer system; hence, the high NO3- and Cl- in shallow wells. Based on ionic relations, thegroundwater chemistry is mainly controlled by silicate weathering, ion exchange and leaching ofwaste from pit toilets. Drilling of deep boreholes is highly recommended.
Keywords: groundwater chemistry, Cl/Br ratio, waste water contamination, environmental isotopes,
diffuse groundwater recharge, Douala-Cameroon©2016. Japan Geoscience Union. All Right Reserved.

- AHW19-02 -AHW19-03

Japan Geoscience Union Meeting 2016

Ammonium and nitrate contamination source and dynamics in groundwater of Kathmandu Valley,Nepal*Takashi Nakamura1, Kei Nishida1, Suresh Das Shrestha3, Yuki Yamamoto1, Kazuki Akahane2, YasuhiroTakimoto2
1.International Research Center for River Basin Environment, University of YAMANASHI, 2.Faculty ofLife and Environmental Sciences, University of Yamanashi, 3.CDG, Tribhuvan University
Groundwater quality is a critical problem in the Kathmandu Valley, Nepal. The population of thecity increased by 6 times in the last six decades and more than half of water demand depends ongroundwater source. Microbial and nitrogen contamination causes loss of water resources,
nevertheless, understanding of ammonia and nitrate source and contamination process in groundwater
system. Objective of this study is to identify the source and contamination processes of theammonium and nitrate in the groundwater.
Groundwater samples were collected from 32 shallow dug wells, 7 tube wells and 5 deep tube wells in
September 2014 and August 2015. About 87% and 60% of groundwater exceeded WHO guideline values forammonium and nitrate concentrations respectively. Nitrogen isotope values of ammonium suggest thatnatural soil production from lake sediments layer in the valley is main contamination sources fordeep and shallow tube wells. In case of dug wells are contaminated by soil production with sewagenitrogen. And nitrogen and oxygen isotopes in nitrate suggest the sewage is main contamination
sources of shallow dug wells and denitrification occurrence in shallow groundwater.
Ammonium nitrogen isotope values are shows less than 10‰. On the other hand nitrate isotope values
are above 10‰, these differences of ammonium and nitrate-nitrogen isotope values are suggests thenitrate contamination sources are only sewage with out nitrification by ammonium originated fromnatural soil. The ammonium stored in groundwater body with out nitrification and denitrifications.
Acknowledgement
This study are supported by the Science and Technology Research Partnership for Sustainable
Development Program (SATREPS, Project Manager: Prof. Narendra Man Shakya and Prof. Futaba Kazama)of Japan Cooperation Agency (JICA)/Japan Science and Technology Agency (JST).
Keywords: Kathmandu Valley, Groundwater, Nitrogen isotope in ammonia, Nitrogen and oxygen isotopein nitrate©2016. Japan Geoscience Union. All Right Reserved.

- AHW19-03 -AHW19-04

Japan Geoscience Union Meeting 2016

Temporal variation of contamination in perched water and groundwater at an open dumpsite
in Sri Lanka*Udayagee PubuduPriya Kumarasinghe1, Yudzuru Inoue1, Takeshi Saito1, Masanao Nagamori2, Mowjood
Mohamad 3, Ken Kawamoto1,4
1.Gaduate school of science and engineering, Saitama University, Japan, 2.Center for Environmental
Science in Saitama, Japan, 3.University of Peradeniya, Peradeniya, Sri Lanka, 4.International
Institute for Resilient Society, Saitama University. JapanIn Sri Lanka, solid waste management is mainly focused on waste collection and dump into opendumpsites. The leachate produced from these dumpsites often pollutes surface water and groundwater.
Identification of temporal variation for leachate and groundwater quality is an important factor
when installing leachate treatment systems, since water quality depends on many factors. In thisstudy, an open dumpsite was selected from wet zone, Sri Lanka, and its perched water inside waste
layer and groundwater quality were monitored for two years (March 2013 to March 2015). Perchedwater and groundwater samples were collected with one month interval and samples were analyzed for
14 parameters. Leachate pollution index (LPI) and piper diagrams were used to analyze the temporalvariation of water quality. Overall and sub-indices of LPI were calculated to identify temporalvariation of risk for groundwater contamination. Groundwater samples showed constant and low LPI
values except for the initial stage of the monitoring and those constant values were similar to
those for the control, a well located at out of the dumpsite. LPI indices calculated for perchedwater is higher than that of groundwater, but it gradually decreased with the time. There is no
considerable different observed in perched water and groundwater with respect to the presence ofheavy metals. Reduction of LPI exhibited the high dissolution of the pollutants over the time. Nocorrelation was observed between LPI and amount of rainfall received over the time.
Keywords: Open solids waste dumps, perched water, groundwater, contamination, leachate pollution
index (LPI)©2016. Japan Geoscience Union. All Right Reserved.

- AHW19-04 -AHW19-05

Japan Geoscience Union Meeting 2016

V&V approach for the groundwater analysis
Hiroyuki Tosaka2, *Tomonari Shiraishi1
1.SHIMIZU CORPORATION, 2.The Univ. of Tokyo
In recent years, V&V (Verification and Validation) which supports the quality guarantee ofnumerical simulation is remarkably examined in a wide range of simulation fields, in addition tothe quality guarantee in the ISO9001 series. There was not so much attention paid to V&V in view ofgroundwater flow analysis in the past. In the field of safety evaluation which is necessary forradioactive waste disposal, however, JSCE (Japan Society of Civil Engineers) has showed a series ofprocedures from creating numerical models to V&V for the purpose of groundwater flow analysis. In
the related researches, there is a challenge which is using one of chemical characteristics for theprediction V&V of the age of groundwater, as well as traditional data like water level, pressure,and flow rate. There are also several researches about the evaluation method of heterogeneity anduncertainty.On the other hand, the basic law on the water cycle was enacted in 2014. It isestimated in the future that the necessity of groundwater flow analyses with V&V would rise up forthe design and safety evaluation of underground facilities.In JAGH (Japanese Association ofGroundwater Hydrology), a research group named as "the problem finding of V&V approach forgroundwater analysis" started from 2015 in the investigation and research committee. The group isdiscussing which problems should be tackled for meeting social needs; collecting actual examples
and experimental data for V&V of groundwater analysis code. In 2016, the group is planning topublish a book collecting code-verification samples and to give seminars concerning V&V.
Keywords: Grouondwater flow analysis, Verification, Validation©2016. Japan Geoscience Union. All Right Reserved.

- AHW19-05 -AHW19-05©2016. Japan Geoscience Union. All Right Reserved.

Japan Geoscience Union Meeting 2016

- AHW19-05 -AHW19-06

Japan Geoscience Union Meeting 2016

Precise measurement of river cross-section using photogrammetry for discharge observation*Yu Tabayashi1
1.University of TsukubaRiver discharge data can be calculated by multiplying river cross-section area and flow rate. Asgaining precise river cross-section area is difficult, river discharge data often include someerrors. Photogrammetry is a method to gain a precise shape of objects but it was hard for
non-expert to master. Thank to the improved technology of digital photo, computer and computer
software, we non-expert nowadays have chance to apply this technology to multiple fields. In thisstudy, I used photogrammetry technology to acquire river cross-section data at Kosakuragawa River,foot of Mt. Tsukuba. The data matched with the data I gained with tape measure. By using
photogrammetry, it is expected that we could gain much precise river cross-section data as we could
gain continuous data of riverbed. When the light condition and water clarity is fine, we could
apply this method and improve accuracy of discharge data.
Keywords: Photogrammetry, River cross-section, Discharge©2016. Japan Geoscience Union. All Right Reserved.

- AHW19-06 -