In this study we describe the degradation of groundwater quality in the Sichuan Basin, one of the most heavily populated and industrialized areas in China. We analyzed the major element chemistry and stable isotopic ratios of H, O, and S from groundwater and surface-water samples collected from four cities along the Minjiang and Yangtze Rivers. On the basis of these data, we examined the sources and downstream variations in groundwater pollutants in relation to increasing human activity in the basin.
Ca²⁺ and HCO₃^- were the dominant ions within groundwater analyzed in this study, although the proportions of Cl^- and SO₄^2- + NO₃^- progressively increased from the source area downstream along the Minjiang River to the Yangtze River. The degradation of groundwater quality was due to anthropogenic sulfur and nitrogen contamination within the basin. Sulfate δ³⁴S values indicated that the primary source of sulfur in contaminated groundwater was air pollutants derived mainly from the combustion of coal, while contamination by household detergents and industrial waste acted to increase SO₄^2- concentrations further downstream. Fertilizer also contributed to elevated SO₄^2- concentrations; however, the area affected by fertilizer contamination was small in comparison with the area affected by other pollutant sources.

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The experiment was conducted to investigate the dissolution of Al and silica when two red soils interact with seawater at different salinities. Different soil weights (3, 10 and 20 g) of bulk soil, coarse sand and silt + clay were mixed with 100 mL of natural seawater, 10, 100, and 1000 times diluted seawaters and shaken for 4 hours to obtain the extracts. Two field surveys were also carried out to observe the impact of red soil in four red soil-impacted estuaries in Okinawa Island during September (summer) and January (winter). Our results revealed that the red soils were acidic (pH ∼5), dominated by SiO₂ and Al₂O₃ contents. During the interaction of red soils with the solutions, dissolved Al and silica increased with an increasing soil/solution ratio while the pH decreased to the lowest value of 3.96 in seawater extracts. The highest Al concentration ranged from 5.03 to 40.3 mgL^-1 in seawater extracts and differed with diluted extracts by 1 to 3 fold, 6 to 24 fold, and 12 to 45 fold for 10, 100 and 1000 times dilution, respectively. The highest silica concentrations of about 1 to ∼11 mgL^-1 were observed in seawater extracts and in 10 times dilution, and they varied with 100 and 1000 times diluted extracts by about 1 to ∼3 fold only. Salinity is more sensitive to Al release than silica but the pH significantly correlated to both logarithmic concentrations of Al (P<0.01) and silica (P<0.001) suggesting the exchange process and H⁺ promoted weathering of silicates, respectively. The field observation also revealed Al increase with salinity from <0.170 mgL^-1 in the river waters to the highest value of 0.474 mgL^-1 in seawater, suggesting an increasing Al solubility by exchange process. The trend of silica in the field differed from that of the laboratory with the highest concentration of 17.8 mgL^-1 in the river and the lowest value of 0.128 mgL^-1 in the seawater, which could be largely attributed to the diatom utilization in summer and dilution in seawater, particularly during winter.

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In this study we investigated the geological and biogeochemical processes that influence groundwater chemistry in the Boso Peninsula, Chiba, central Japan. We also discuss the factors that control groundwater chemistry within a sedimentary basin. Saline groundwater is found throughout the study area, while fresh groundwater is distributed unevenly in the central and southern parts of the study area. The distribution of Cl^- concentration indicates that groundwater in the study area is influenced by not only present-day seawater penetration but also presence of fossil brine water, although their extents remain uncertain. Since thermodynamic calculation of mineral saturation indices indicates that the groundwater is not in equilibrium with the host rock, it is considered that seawater has intruded to inland areas with and/or after progress of geochemical reactions. Consequently, changes in the concentration of various chemical species by geochemical processes (seawater-freshwater mixing is excluded) were calculated and used as a basis for the classification of samples into six reaction types according to the changing trends of the concentration values calculated by assuming that seasalt components of rainwater affect the groundwater chemistry. Chemical composition is not always correlated with a certain reaction type. The groundwater geochemistry of some reaction types is governed mainly by the dissolution of silicates (plagioclase, illite, chlorite and montmorillonite) and carbonates (calcite, dolomite, and siderite) and precipitation of carbonate minerals, as well as ion exchange of cations. The chemical properties of saline water are influenced by bacterial sulfate reduction, bromine, and the production of methane.

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Variations of the chemical composition and elemental speciation of aeolian dust transported from China to Japan were investigated in this study. During 6-12 April 2002, a large-scale dust event was observed in China, Korea, and Japan. Aerosol samples collected in Beijing, Fukuoka, Nagoya, and Tsukuba at that time were used for this study. Variations of most elemental concentrations against the particle size showed similar trends to that of Al concentration. The particle size distributions indicate that myriad elements in the aerosols originated mainly from mineral aerosols. The metal/Al concentration ratios showed little difference in chemical compositions for aerosols sampled at Beijing and Japanese stations: the chemical composition of aeolian dust is conserved during transportation. Examination by X-ray absorption near-edge structure (XANES) spectroscopy revealed that the Fe(III)/Total Fe (T-Fe) ratios of the aerosols collected in Beijing and Fukuoka were mutually resemblant, indicating that the oxidation-reduction reaction of Fe in aeolian dust during its transportation is negligible. However, their ratios were much higher than those of China loess and simulated Asian mineral dust (Chinese geo-reference materials: CJ-1 and CJ-2). Because the aerosol grain size is much smaller than those of CJ-1 and CJ-2, the fine mineral was transported selectively by wind from top soils. It was easily oxidized and had a high Fe(III)/T-Fe ratio. The XANES spectra of Mn in the aerosol indicated that the Mn(III)/Total Mn (T-Mn) ratios of the aerosol collected in Fukuoka were smaller than those of the dust collected in Beijing. The ratios of the aerosols in Beijing resembled those of CJ-1 and CJ-2. Moreover, only medium grains of the aerosol in Fukuoka had high Mn(III). The other grains had an almost identical Mn(III)/T-Mn ratio as the aerosol collected in Fukuoka in the no event. Thereby, most medium grain aerosols collected in Fukuoka comprised aeolian dust coming from China with high Mn(III)/T-Mn ratios like those of CJ-1 and CJ-2, but the other grain aerosols mixed greatly with local aerosols having low Mn(III)/T-Mn ratios. On the other hand, some elements such as Zn and Pb had different Al concentration ratios from Mn and Fe. The Zn/Al and Pb/Al concentration ratios of fine grains increased tenfold to a hundredfold with the decrease of particle size. Therefore, the increasing trend for these elements indicates that the fraction of anthropogenic materials was greatly increased in fine grains. The XANES spectra of Zn suggested that the contribution of mineral aerosols decreased gradually with decreasing particle size and that the residual components were explained by Zn(NO₃)₂ in coarse-medium grains and ZnSO₄ in fine grains. However, Zn in aeolian dust, which is a main component of mineral aerosols, only rarely originated from anthropogenic materials when a large-scale dust event was observed.

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Ultramafic (mg#>88) xenoliths from the Tertiary Veneto Volcanic Province (SE Alps, Italy) are characterized by variable depletion due to removal of a basaltic component and show significant trace element and isotopic (⁸⁷Sr/⁸⁶Sr: 0.703031-0.704356; ¹⁴³Nd/¹⁴⁴Nd: 0.512817-0.513085; ²⁰⁶Pb/²⁰⁴Pb: 18.539-19.694; ²⁰⁷Pb/²⁰⁴Pb: 15.608-15.658; ²⁰⁸Pb/²⁰⁴Pb: 38.412-39.660; δ¹⁸O: 6.6-11.2‰) heterogeneity. Variable large-ion lithophile and light rare earth/high field strength element ratios and isotopic compositions occur in samples showing comparable mineralogy and major element content. Petrologic and geochemical characteristics of whole rocks and minerals may be explained by metasomatism of the local mantle lithosphere induced by both alkaline magmas upwelling to the surface (OIB-like mantle diapirism) and interaction with slab-derived material. In comparison with the geochemistry of xenoliths carried by alkaline magmas in typical within-plate tectonic environments, the Veneto xenoliths record a major heterogeneity of the local lithosphere. This appears to be related to a geodynamic scenario that was previously dominated by active continental collision, in which plume-like magmatism subsequently manifested itself.

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A carbon and oxygen stable-isotope study was undertaken on samples from the uppermost Turonian-Santonian Aleg Formation and the Campanian-lowest Maastrichtian Abiod Formation from four wells in the Miskar Field (W1, W2, W3, and W4), Gulf Gabès, offshore southeastern Tunisia. The strontium contents of the same samples were also determined. Carbon isotopes generally yielded values typical of Upper Cretaceous chalks. Calculation of palaeotemperatures using the δ¹⁸O data obtained from the analysis of whole-rock samples from the four wells, in most cases generated higher values than those believed to characterize Santonian-Campanian ocean surface waters. This general negative shift in δ¹⁸O values is thought to be related to alteration that has resulted from burial diagenesis. Strontium contents in the Abiod Formation are typical of Cretaceous - Tertiary chalks.
Top Aleg samples are depleted by around -0.6‰ δ¹⁸O and -0.1‰ δ¹³C compared to the Abiod samples, and by up to -300 μg/g Sr. Depletion in δ¹³C, δ¹⁸O and strontium in the Aleg Formation is attributed to alteration by meteoric waters, indicating that the top of the Formation has been subject to both meteoric and burial diagenesis. This contrasts with the Abiod Formation which yields unaltered δ¹³C and strontium values, and oxygen-isotope data which, although lighter than those typical of pristine Upper Cretaceous sediments, are heavier than those recorded in the Aleg Formation, suggesting that only burial diagenesis has affected the younger sediments. In our case, the use of the oxygen data for the calculation of marine palaeotemperatures is not reliable.
The strontium concentration, oxygen and carbon stable-isotope data indicate the presence of an unconformity between the Abiod Formation and the Aleg Formation, with possible subaerial exposure of the top of the Aleg Formation, probably during the Coniacian-Santonian and earliest Campanian. This result is consistent with the biostratigraphy of the four wells which confirms that an unconformity exists between the two formations.

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