Multivariate analysis of trace elements in shallow groundwater in Fuchu in western Tokyo Metropolis, Japan

Abstract

A rapid increase in the use of ground source heat pump (GSHP) systems for heating and cooling of buildings potentially threatens to harm shallow groundwater quality. As a necessary preliminary step toward evaluating GSHP impact on shallow groundwater quality, this study used multivariate statistical analyses to investigate characteristics of trace elements in groundwater in Fuchu city in western Tokyo Metropolis. Water samples were collected twice a month from two aquifers at 30-and 45-m depths using four observation wells for more than a year. Concentrations of 14 trace elements (Li, B, Al, Cr, Mn, Fe, Ni, Cu, As, Se, Sr, Cd, Sb, and Pb) and Si as well as oxidation-reduction potential (ORP), dissolved oxygen (DO), electrical conductivity (EC), and pH were measured. All elements were under the environmental water quality criteria issued by the Japanese Ministry of the Environment. No clear seasonal trends were observed in the concentrations of 15 elements in groundwater. Principal component analyses showed the element properties were well characterized by three principal components (PC). PC1, which represents the more mobile trace elements in the groundwater, consisted of Li, B, Mn, Fe, As, and Si. PC2 included Al, Ni, Cd, and Sb, and represents ORPinsensitive properties. PC3 consisted of Pb, Cu, and Se, which are less mobile in groundwater. Samples collected from the same aquifer had high similarity in distribution and variation of the trace elements. This study proposes a useful statistical platform for assessing future effects of GSHP systems on shallow groundwater quality.

Assessment of major ions and trace elements in groundwater supplied to the Monterrey metropolitan area, Nuevo León, Mexico

“…These facts could suggest that Pb and Cu have a low mobility in groundwater and that the solubility of both elements is controlled by the same geochemical processes. Similar results have been found in groundwater supplied to western Tokyo, which have indicated that Pb and Cu are the less mobile elements in these waters (Thuyet et al 2016 ). Furthermore, Chen et al ( 2007 ) have found significant correlations between Pb and Cu in groundwater from coastal area in Shenzhen, China.…”

“…Regarding trace element abundances, the mean concentration values of these in groundwater of the studied area (with the exception of Pb) were lower than the mean concentrations of trace elements in groundwater supplied to other megacities such as Tokyo (Mn 82 μg/L, Cu 3.7 μg/L, Se 4.7 μg/L, Cr 1.8 μg/L, As 1.8 μg/L, and Cd 0.1 μg/L), mainly because groundwater in that region is in contact with volcanic ash soils (which can be rich in trace elements) and unconsolidated layers of silt, sand, and gravel (Thuyet et al 2016 ). However, the mean trace element contents in groundwater supplied to MMA were higher than those found in groundwater supplied to heavily urbanized areas of Hong Kong (Mn 2.72 μg/L, Cu 1.16 μg/L, Zn 40.8 μg/L, Se 0.38 μg/L, Cr 0.71 μg/L, Co 0.02 μg/L, As 0.42 μg/L, Mo 0.29 μg/L, and Cd 0.07 μg/L), a region in which the geology is dominated by acidic volcanic rocks and granite bedrocks (Leung and Jiao 2006 ).…”

“…On the other hand, Mn exhibits an opposite behavior than that shown by As and Mo. In oxygen-depleted groundwater, soluble Mn exists in the form of Mn 2+ (Thuyet et al 2016 ), which also shows a moderate solubility. However, alkaline and oxidizing conditions promote the oxidation of soluble Mn 2+ to insoluble Mn-oxyhydroxides (such as Mn 2 O 3 , MnOOH, and MnO x ) (Tebo et al 2005 ).…”

“…Owing to large urban areas demanding a large amount of water for drinking, domestic and industrial purposes, studies about the quality of groundwater in megacities such as Shanghai, New Delhi, Tokyo, and Hong Kong have received increased attention (Leung and Jiao 2006 ; Gao et al 2012 ; Thuyet et al 2016 ; Singh et al 2017 ). Similarly, current published information regarding groundwater quality indicates that both major ion and trace element abundances can be a matter of health concern for humans.…”

A computationally efficient pseudo-3D model for the numerical analysis of borehole heat exchangers

“…1. Two 50-m long vertical boreholes with an inner diameter of 180 mm were drilled in 2011 at TUAT to be used as borehole heat exchangers for a groundsource heat pump system installed for a 25 m 2 constant temperature room [26]. Without finishing with casing, two U-shaped 3-mm thick 20-mm diameter pipes made of high-density polyethylene (HDPE) were inserted into the borehole along with space-filling grout, which consisted mainly of silicate sand.…”