Effect of groundwater flow on forming arsenic contaminated groundwater in Sonargaon, Bangladesh

Three-dimensional groundwater flow in Sonargaon, Bangladesh is numerically simulated in order to evaluate the flow paths of As-contaminated drinking groundwater in the Holocene aquifer of the Ganges-Blamaptra-Meghna delta plain over a recent 30-year period. The model indicates that vertical infiltration of surface groundwater into the shallow Holocene aquifer occurs frequently in the Ganges-Blamaptra-Meghna delta plain. It predicts that the water recharged from ground surface moves approximately 10-20 m vertically downward beneath the flood plain, with a gradually increasing horizontal flow, toward the underlying Pleistocene middle mud layer (aquitard). The model also predicts that groundwaters containing highest As concentrations (>700 mu g/L) are formed on the vertical groundwater flow paths where surface water recharges the Holocene aquifer and not on the horizontal flow paths. Combining with the groundwater chemistry, reducing groundwater condition is not essential for the As-contaminated groundwater of the studied area in the Ganges delta plain.ArticleJOURNAL OF HYDROLOGY. 409(3-4):724-736 (2011)journal articl

Relevance of Some Damage Factors to Structures Damage in the 1995 Kobe Earthquake

The 1995 Kobe Earthquake (Hyogoken-nanbu Earthquake) caused a severe damage to various kinds of structures. As damage factors of these structures, the characteristics of seismic motion, distance from the earthquake source fault, ground conditions, liquefaction, and strength of structures can be considered. In this paper, paying attention to the distance from the earthquake source fault and ground conditions among them, the relevance to structures damage in wooden houses (on-ground structure) and water supply pipelines (under-ground structure) in Nishinomiya-City area was examined. As the results, the relationship between wooden houses damage and the distance from the fault can be approximately represented as a unique exponential function. In liquefied areas, however, the rate of completely collapsed wooden houses decreases 5 to 20% from the average value. This might be because the damping of earthquake motion brought the decrease of the damage rate. While, the relationship between water supply pipelines damage and the distance from the fault completely differs from the above-mentioned for wooden houses. A characteristic value Tg estimated from the distribution of N value at each location can be used for the ground classification in earthquake-proof design. The damage rate of water supply pipelines increases as increasing Tg , while that of wooden houses decreases as increasing Tg