[Show abstract][Hide abstract]ABSTRACT: Rare earth element (REE) geochemistry is a useful tool in delineating hydrogeochemical processes and tracing solute transport, which can be used to reveal groundwater chemical evolution in the complexed groundwater systems of the North China Plain (NCP). Groundwaters and sediments were collected approximately along a flow path in shallow and deep aquifers of the NCP to investigate REE geochemistry as a function of distance from the recharge zone. Groundwater REE concentrations are relatively low, with ranges from 81.2 to 163.6 ng/L in shallow groundwaters, and from 65.2 to 133.7 ng/L in deep groundwaters. Speciation calculation suggests that dissolved REEs mainly occur as dicarbonato (Ln(CO3)2−) and carbonato (LnCO3+) complexes. Although along the flow path groundwater REE concentrations do not vary substantially, relatively lower HREEs are observed in central plain (Zone II) compared to recharge area (Zone I) and discharge plain (Zone III). Shale-normalized REE patterns are characterized by different degrees of enrichment in the HREEs, as indicated by the variation in average (Er/Nd)NASC value. The similar REE compositions and shale-normalized REE patterns of shallow and deep groundwaters demonstrate that interactions of groundwaters between shallow and deep aquifers possibly occur, which is likely due to the long-term groundwater over-exploration. Cerium anomalies (Ce/Ce∗ = CeNASC/(LaNASC × PrNASC)0.5) generally increase from Zone I, through Zone II, to Zone III, with trends from 0.79 to 3.58, and from 1.22 to 2.43 in shallow groundwaters and deep groundwaters, respectively. This is consistent with the variations in oxidation–reduction potential and redox sensitive components (i.e., dissolved Fe, Mn, NO3− and As concentrations) along the flow path. Positive Ce anomaly and redox indicators suggest that redox conditions progressively evolve from oxic to moderate anaerobic in the direction of groundwater flow. In the recharge zone (Zone I), groundwater low positive Ce anomalies are likely due to partially oxidative scavenging of Ce(III) to Ce(IV), and HREE enrichment would result from preferential scavenging of the LREEs relative to the HREEs during Fe/Mn oxides/oxyhydroxides precipitations, which is well supported by the low concentrations of dissolved Fe and Mn. In the down-gradient (Zone II and Zone III), reductive dissolution of Fe/Mn oxides/oxyhydroxides increases positive Ce anomalies along the flow path. The positive correlations between (Er/Nd)NASC values and dissolved Fe/Mn concentrations suggest that reductive dissolution of Fe/Mn oxides/oxyhydroxides, as well as readsorption, are the geochemical controls on groundwater REE fractionation patterns. Groundwaters mostly have positive Eu anomalies (Eu/Eu∗ = EuNASC/(SmNASC × GdNASC)0.5), which would be the result of chemical weathering of feldspars (e.g., plagioclase) detected in aquifer sediments by XRD technique.
Full-text · Article · Nov 2015 · Journal of Asian Earth Sciences
[Show abstract][Hide abstract]ABSTRACT: The potential developmental toxicity of environmental estrogenic endocrine disruptors have become a great concern in recent years. In this study, two typical environmental oestrogen, namely, bisphenol A (BPA) and genistein (GEN) were investigated for potential embryotoxicity using the embryonic stem cell test model. Afterwards, a 4×4 full factorial design and the estimated marginal means plot were performed to assess the combined effects of these two compounds. According to the linear discriminant functions and classification criteria, bisphenol A and genistein were classified as weakly embryotoxic and strongly embryotoxic respectively. As for combined effects, the overall interaction between BPA and GEN on embryonic stem cells (ESCs) differentiation was synergistic at low dosages, however, on ESCs and 3T3 cell proliferation, the predominate action was additive. Considering the actual daily intake of these chemicals, it is concluded that BPA alone might not have adverse reproductive or developmental effects on human being. However, given that BPA and GEN do have synergistic effect at low concentration, they may disturb normal embryo development together, which could result in birth defect and behavioral alterations later in life.
No preview · Article · Aug 2013 · Food and chemical toxicology: an international journal published for the British Industrial Biological Research Association
[Show abstract][Hide abstract]ABSTRACT: The North China Plain is one of the biggest plains in China, where municipal, agricultural and industrial water supplies are highly dependent on groundwater resources. It is crucial to investigate water chemistry and hydrogeochemical processes related to hydrogeologic settings for sustainable utilization of groundwater resources. Two hydrochemical profiles proximately along the groundwater flow paths were selected for hydrogeochemical study. Major components and 2H and 18O isotopes were analyzed in groundwater samples from the profiles. The study area was divided into three zones, including strong runoff-alluvial/pluvial fans in the piedmont area (Zone I), slow runoff-alluvial/lacustrine plain in the central area (Zone II), and discharge-alluvial/marine plain in the coastal area (Zone III). Major components of groundwater samples showed obvious zonation patterns from Zone I to Zone III. Total dissolved solid (TDS) concentrations gradually increased, and the hydrochemical type changed from HCO3–SO4–Ca–Mg and HCO3–Cl–Ca–Mg types to HCO3–SO4–Na–Ca, SO4–Cl–Na–Ca and SO4–Cl–Na types from Zone I to Zone III. Abrupt increases in concentrations of Na+, Cl− and SO42- in deep groundwater were observed around the depression cones, which indicated that overexploitation resulted in water quality deterioration. Calcite and dolomite precipitation occurred in Zone I of deep groundwater systems and shallow groundwater systems. Cation exchange was believed to take place along the entire flow paths. Gypsum tended to dissolve in groundwater systems. The depletion in D and 18O isotopes in deep groundwater was related to the recharge from precipitation in paleo-climate conditions in glacial or interglacial periods, indicating that renewal groundwater was very limited. Efficient strategies must be taken to preserve the valued water resources for sustainable development.
Full-text · Article · Jul 2013 · Journal of Asian Earth Sciences
[Show abstract][Hide abstract]ABSTRACT: Bisphenol A (BPA) has been widely used in the manufacture of polycarbonate plastic, water bottles and food containers. Previous studies have established that BPA could cause developmental toxicity by inhibiting the proliferation and differentiation of rat embryonic midbrain (MB) cells in vitro. However, the underlying mechanisms have not been well studied yet. In the current study, we examined the proliferation and differentiation of MB cells treated with 10(-12)-10(-4) M BPA and found that only 10(-4) M BPA inhibited proliferation and differentiation. Then, we investigated the cell cycle progression and apoptosis of MB cells; 10(-4) M BPA caused an explicit S phase and G2/M phase arrest in the cell cycle and increased the percentage of apoptotic cells. Moreover, the phosphorylation of mitogen-activated protein kinase (MAPK) and cyclic-AMP response binding protein (CREB) and the expression of some apoptotic regulatory genes were investigated. BPA (10(-4) M) reduced the phosphorylation of C-Jun N-terminal kinase (JNK) and CREB, and increased the mRNA expression level of Bax and p53. Our findings demonstrated that BPA could cause developmental toxicity through anti-proliferation and pro-apoptosis in MB cells. Multiple signaling pathways, such as the JNK, CREB and p53- mitochondrial apoptosis pathways, participate in these effects.
No preview · Article · Nov 2012 · Food and chemical toxicology: an international journal published for the British Industrial Biological Research Association
[Show abstract][Hide abstract]ABSTRACT: a b s t r a c t Twenty-nine wells were selected for groundwater sampling in the town of Shahai, in the Hetao basin, Inner Mongolia. Four multilevel samplers were installed for monitoring groundwater chemistry at depths of 2.5–20 m. Results show that groundwater As exhibits a large spatial variation, ranging between 0.96 and 720 lg/L, with 71% of samples exceeding the WHO drinking water guideline value (10 lg/L). Fluoride concentrations range between 0.30 and 2.57 mg/L. There is no significant correlation between As and F À concentrations. Greater As concentrations were found with increasing well depth. However, F À concen-trations do not show a consistent trend with depth. Groundwater with relatively low Eh has high As con-centrations, indicating that the reducing environment is the major factor controlling As mobilization. Low As concentrations (<10 lg/L) are found in groundwater at depths less than 10 m. High groundwater As concentration is associated with aquifers that have thick overlying clay layers. The clay layers, mainly occurring at depths <10 m, have low permeability and high organic C content. These strata restrict diffu-sion of atmospheric O 2 into the aquifers, and lead to reducing conditions that favor As release. Sediment composition is an additional factor in determining dissolved As concentrations. In aquifers composed of yellowish-brown fine sands at depths around 10 m, groundwater generally has low As concentrations which is attributed to the high As adsorption capacity of the yellow–brown Fe oxyhydroxide coatings. Fluoride concentration is positively correlated with pH and negatively correlated with Ca 2+ concentra-tion. All groundwater samples are over-saturated with respect to calcite and under-saturated with respect to fluorite. Dissolution and precipitation of Ca minerals (such as fluorite and calcite), and F À adsorption–desorption are likely controlling the concentration of F À in groundwater.
Full-text · Article · Nov 2012 · Applied Geochemistry
[Show abstract][Hide abstract]ABSTRACT: Genistein (GEN) is one kind of phytoestrogen. Several studies have demonstrated the teratogenic potential of GEN in vitro by postimplantation rat whole embryo culture (WEC) assay, but GEN showed no teratogenic effects in vivo even at a dose up to 1000 mg/kg bw/day. The mechanism of such discrepancy is still unclear. Because more than 80% of total genistein (free plus glycoside form) in circulation is its glycoside metabolite, genistin (GIN), we thus hypothesize that genistin is non-teratogenic. To prove this hypothesis, rat whole embryo culture (WEC) and limbud micromass culture methods were applied to compare the teratogenic effects of GEN and GIN on developing embryos in vitro. In WEC assay, we found that the development of embryos was affected by GEN treatment dose-dependently, while GIN-treated embryos displayed slight developmental defects only at the highest dose (222 μM). In micromass culture assay, the IC50 of cell proliferation and differentiation for GEN were 15.6 and 37.2 μM, respectively, while neither was influenced by GIN treatment up to 111 μM. Collectively, our study indicated that GEN showed no teratogenic effects in vivo probably due to its transformation to the non-teratogenic metabolite, GIN.
No preview · Article · May 2012 · Food and chemical toxicology: an international journal published for the British Industrial Biological Research Association
[Show abstract][Hide abstract]ABSTRACT: Bisphenol A (BPA), widely used in industry and dentistry, and genistein (GEN), the predominant component of soy product, are both known environmental estrogen. In the present study, we investigated the developmental toxicity of BPA and GEN and their combined effect using micromass test, which is one of three standard alternative developmental toxicity tests recommended by European Center for the Validation of Alternative Methods (ECVAM). The results showed that IC50-P (cell proliferation) and IC50-D (cell differentiation) of BPA and GEN were approximately 20 and 5 μg/ml, respectively. No observed adverse effect level (NOAEL) of BPA and GEN were 10 and 0.94 μg/ml, respectively. The manifestation of BPA as a teratogen was insufficient, although the "low dose" effect should be paid attention to. While the evidence of GEN as a teratogen was solid, especially with the consideration of "high dose" application in clinical treatment. The combined effect of BPA and GEN was generally additive action except that in MB proliferation.
No preview · Article · Oct 2010 · Toxicology in Vitro
[Show abstract][Hide abstract]ABSTRACT: Some studies show that Cd(2+) and Hg(2+) may induce cell proliferation and apoptosis via biphasic dose-response relationship in human cells. However, mechanisms underlying this phenomenon are still in puzzle. In this study, we aim at detecting the biphasic effects of Cd(2+) and Hg(2+) on proliferation and apoptosis of human embryonic kidney 293 (HEK293) cells, analyzing the change of the mitogen-activated protein kinase (MAPK) pathways, and discussing the relationship between them. The results demonstrate that Cd(2+) and Hg(2+) can stimulate cell proliferation at lower concentrations (0.05 and 0.5 microM) but inhibit it at higher concentrations (50 and 500 microM). Apoptosis increases at higher concentrations (50 and 500 microM) of Cd(2+) and Hg(2+). While 0.5 microM Cd(2+) and Hg(2+) decrease the JNK phosphorylation, 50 microM Cd(2+) and Hg(2+) increase the JNK and P38 phosphorylation. When HEK293 cells are treated with 20 microM JNK inhibitor or 100 microM ERK1/2 inhibitor, the cell proliferation do not increase significantly at low concentrations (0.05 and 0.5 microM), but still decrease at high concentrations (50 and 500 microM). When HEK293 cells are treated with 20 microM P38 inhibitor, the tendency of cell proliferation is not affected. Data in our study suggests that activation of MAPK pathway may be involved in the biphasic effect induced by Cd(2+) and Hg(2+).
Preview · Article · Apr 2009 · Toxicology in Vitro