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The objective of the present study was to increase understanding of the effects of heavy metal pollution and soil properties on microorganisms in relation to the biomass and microbial functional community. Soil samples were collected from aged polluted and reference sites on a floodplain. The soil Cu, Zn and Pb total concentrations were much higher at the polluted sites (average 231.6-309.9 mg kg −1 , 195.7-233.0 mg kg −1 , and 72.4-86.0 mg kg −1 , respectively) than at the reference site (average 33.3-44.0 mg kg −1 , 76.7-98.0 mg kg −1 , and 30.8-41.6 mg kg −1 , respectively), while the available heavy metal concentrations in CaCl 2 extraction were similar in all sites. Small seasonal variations in the size of microbial biomass were observed. Ambient soil properties (e.g. total C, N, pH, moisture content, and CEC) affected the soil microbial biomass more than the heavy metal pollution. However, the aged pollution tended to impact on the composition of the microbial community. PICT (pollution-induced community tolerance) test using BIOLOG Ecoplates showed enhanced tolerance of the microbial community to Cu stress in the polluted site. In non polluted but low nutrient, low pH and low moisture soil, the microbial biomass was lower and the microbial community was more vulnerable to Cu stress. In spite of the low heavy metal availability due to ageing, the BIOLOG technique provided sensitive detection of microbial community level changes in PICT analysis.

Prediction of heavy metal bioavailability in intact soil is important to manage soil pollution risks. We developed a regression model for representative Japanese soils to judge their potential vulnerability to cadmium (Cd) pollution. We added four rates of Cd to 17 sample soils to mimic artificial contamination. After aging the contaminated soils, we measured Cd’s bioavailability using the diffusive gradients in thin-films (DGT) technique. We then evaluated the relationships between bioavailability of Cd ([Cd DGT ]) and intact soil properties by statistical analyses. Cation exchange capacity (CEC) and pH emerged as significant factors to explain the cadmium bioavailability in Japanese soils. Specifically, lower CEC and lower pH were associated with higher [Cd DGT ], which poses a higher risk for soil ecosystems. The correlation between pH and [Cd DGT ] had a high dependence on [Cd Add ], whereas that for CEC did not. Regression analysis also showed that the interaction between intact soil pH and spiked concentration ([Cd Add ]) had a significant contribution to [Cd DGT ]. The regression model developed was rationally supported by a biotic ligand model. This simplified but realistic model would be useful in estimating the vulnerability of representative Japanese soils and determining the risk for Japanese soils in relation to Cd contamination.

To elucidate geochemical characteristics of groundwater and sources of dissolved ions in groundwater at the southern slope and the base of Mt. Fuji, central Japan, in 2011 and 2012, dissolved ions in 199 samples of both well water or spring water from the study region and 12 monthly precipitation samples at each of four elevations were collected and analyzed. Most of the groundwater was of the Ca-HCO 3 type. The study region was divided from the near summit to the base of the mountain into four areas based on water quality, topography, geology, and land use at the watershed. The concentration of chlorine ion (Cl -) in the groundwater and precipitation tended to decrease with elevation, and the Na ＋ /Clratio in the precipitation (0.56 on average) was close to that of seawater (0.56) at all sites. The atmosphere-derived fractions of major cations in the groundwater, which were estimated by assuming that all Clwas derived from sea salt in the atmosphere, were in ascending order: Ca (average 0.05), Mg (0.08), K (0.28), and Na (0.29). The concentrations of PO 4 3and Fand the cation: Clratios of all cations were high in the groundwater in the eastern area, where the surface geology consists of Gotemba mud flow sediments, which are composed of volcanic materials of the Old Fuji period. These results indicate that groundwater quality is strongly affected by the basaltic materials composing Mt. Fuji, which are enriched with Ca and Mg, and are susceptible to chemical weathering, but differs between aquifers in volcanic rocks of the Old Fuji period (about 100 ka) and those in rocks of the New Fuji period (after about 10 ka). In the southwestern and southeastern areas, the groundwater was characterized by a high concentration of NO 3 -. Because tea plantations are distributed at upper elevations in these areas, we inferred the major source of nitrogen in the water to be fertilizer. Moreover, spring water was enriched more with NO 3 than well water collected at similar elevations, suggesting that the recharge area of well water is at a higher elevation than the spring water recharge area.