Numerical simulations on anomalous solute transport and risk maps of nitrate nitrogen

2018 Fiscal Year Final Research Report

• Project/Area Number: 16K07941
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Rural environmental engineering/Planning
• Research Institution: Kobe University
• Principal Investigator: Inoue Kazuya 神戸大学, 農学研究科, 准教授 (00362765)
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: 異常輸送 / 硝酸態窒素 / 溶質輸送 / 模型実験 / リスクマップ

Outline of Final Research Achievements

This study presented a stochastic approach for estimating time-related solute capture zones of two pumping wells in three dimensions in a groundwater contamination site. In order to visualize a contaminated area as a risk map, random walk particle tracking was applied to assess the travel time and subsequent spatial probability distributions of introduced ensemble lattice cells having the probability that particles located initially within cells reach the pumping wells during a certain duration of the pumping. Laboratory tracer experiments were also conducted to elucidate variations of contaminated area. The results demonstrated that weighted volumes of solute capture zones coincide with the total pumping rate and outer solute capture zone in the site evolves deeper areas of inner solute capture zone. Moreover, entropy related to the spatial probability distributions increased with elapsed time, providing a time-related risk map.

Free Research Field

農業工学

Academic Significance and Societal Importance of the Research Achievements

溶質の異常輸送は局所性の高い現象であり，フィールドにて観測することが難しい現象であるため，理論的・数値的検討が多くなされてきた．当該研究では，模型実験により，異常輸送現象の発現とその伝播をマクロ分散現象の観点から定量化することに成功した点に学術的意義を有している．地下水管理を想定して，地下水揚水に伴う地下水流れと溶質輸送の関係を可視化できる数値シミュレータをランダムウォーク粒子追跡法により開発し，実際の汚染サイトを対象に検証した点は社会的意義を有していると判断される．揚水井を軸として，時々刻々と移り変わる汚染領域の変動をリスクマップとして可視化するシステムを構築した点は当該研究の特徴である．