Spatial and Temporal Variations of Heavy Metals' Bioavailability in Soils Regulated by a Combined Material of Calcium Sulfate and Ferric Oxide.

Heavy metal pollution in soils threatens food safety and human health. Calcium sulfate and ferric oxide are commonly used to immobilize heavy metals in soils. However, the spatial and temporal variations of the heavy metals' bioavailability in soils regulated by a combined material of calcium sulfate and ferric oxide (CSF) remain unclear. In this work, two soil column experiments were conducted to investigate the spatial and temporal variations of CSF immobilized Cd, Pb, and As. In the horizontal soil column, the results showed that CSF's immobilization range for Cd increased over time, and adding CSF in the center of the soil column decreased the concentrations of bioavailable Cd significantly, up to 8 cm away by day 100. The CSF immobilization effect on Pb and As only existed in the center of the soil column. The CSF's immobilization depths for Cd and Pb in the vertical soil column increased over time and extended to 20 cm deep by day 100. However, the CSF's immobilization depths for As only extended to between 5 and 10 cm deep after 100 days of incubation. Overall, the results from this study can serve as a guide to determine the CSF application frequency and spacing distance for the in-situ immobilization of heavy metals in soils.

Simultaneous immobilization of the cadmium, lead and arsenic in paddy soils amended with titanium gypsum.

In situ immobilization of heavy metals in contaminated soils using industrial by-products is an attractive remediation technique. In this work, titanium gypsum (TG) was applied at two levels (TG-L: 0.15% and TG-H: 0.30%) to simultaneously reduce the uptake of cadmium (Cd), lead (Pb) and arsenic (As) in rice grown in heavy metal contaminated paddy soils. The results showed that the addition of TG significantly decreased the pH and dissolved organic carbon (DOC) in the bulk soil. TG addition significantly improved the rice plants growth and reduced the bioavailability of Cd, Pb and As. Particularly, bioavailable Cd, Pb and As decreased by 35.2%, 38.1% and 38.0% in TG-H treatment during the tillering stage, respectively. Moreover, TG application significantly reduced the accumulation of Cd, Pb and As in brown rice. Real-time PCR analysis demonstrated that the relative abundance of sulfate-reducing bacteria increased with the TG application, but not for the iron-reducing bacteria. In addition, 16S rRNA sequencing analysis revealed that the relative abundances of heavy metal-resistant bacteria such as Bacillus, Sulfuritalea, Clostridium, Sulfuricella, Geobacter, Nocardioides and Sulfuricurvum at the genus level significantly increased with the TG addition. In conclusion, the present study implied that TG is a potential and effective amendment to immobilize metal(loid)s in soil and thereby reduce the exposure risk of metal(loid)s associated with rice consumption.

Arsenic adsorption and removal by a new starch stabilized ferromanganese binary oxide in water.

A new starch stabilized ferromanganese binary oxide (starch-FMBO) with an Fe/Mn ratio of 1.00-2.00 and a synthetic pH of 2 was prepared using an organic polymer (starch) as the stabilizing dispersant. The maximum arsenic adsorption capacity of starch-FMBO was 161.29 mg/g. Adsorption optimization was also conducted, which revealed that starch-FMBO had a high adsorption capacity over a wide pH range (pH 3.0 to pH 11.0) and in the presence of some common anions (HCO3-, SO42-, Cl-, and NO3-). Arsenic removal by FMBO and starch-FMBO followed pseudo-second-order dynamics (R2 ≥ 0.99), indicating that the adsorption rate depended on the chemical adsorption process. Through the analysis of X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared spectroscopy (FTIR), it was shown that hydroxyl was continuously produced and complexated with As(III) and As(V) during the adsorption process. Thus, the reaction of iron oxide and manganese oxide with arsenic was inferred and explained. The developed starch-FMBO shows promise for its application in the treatment of arsenic-contaminated water.

Impacts of land-use on surface waters at the watershed scale in southeastern China: Insight from fluorescence excitation-emission matrix and PARAFAC.

In recent years, the Chinese government has strengthened its efforts in surface water protection and restoration through strict policies and heavy investments. A clear understanding of the impacts of land use on water quality is necessary in order to ensure an effective and efficient implementation of the ongoing surface water restoration program in China. To this end, four small watersheds (less than 5000 ha) in southeastern China, which have clear gradients in the intensities of agriculture (17.0-45.4%), forest (35.2-73.6%) and built-up area (3.3-8.5%), were investigated regarding the impacts of land use on water quality. In addition to the general water quality indices, characteristic components derived by fluorescence excitation-emission matrices (FEEMs) coupled with parallel factor analysis (PARAFAC) were employed to explore a more accurate association between land use and water quality. The results show that agricultural intensity has significant effects by elevating the concentrations of dissolved organic carbon (DOC, an approximate six-fold increase) and total phosphorous (TP, an approximate four-fold increase) in the surface waters. A total of five PARAFAC components representing terrestrial (three components) and protein-like (two components) substances were identified. The PARAFAC results indicate that land-use patterns affected the dissolved organic matter (DOM) in the aspects of both amount and composition. The intensity (R.U.) of the terrestrial components showed a strong correlation (r2 = 0.95, p = 0.01) with agricultural land percentage. Moreover, although the proportion of built-up area varies with a relatively small range, a protein-like component could predict its impact with excellent sensitivity (r2 = 0.94, p = 0.02), whereas the general water quality indices were incapable of predicting the impact due to their multiple sources. The results of this study demonstrate that the FEEMs-PARAFAC technique provides an inexpensive and effective tool for policy makers to overcome the insensitivity of general water quality indices, particularly for the restoration of watersheds with complex land-use patterns.

Expression of SIRT1 and P53 in Rat Lens Epithelial cells in Experimentally Induced DM.

PURPOSE: To determine the etiopathogenesis of diabetic cataract by studying changes in relative expressions of silent information regulator protein-1 (SIRT1) and P53 in rat lens epithelial cells (LECs) in experimentally induced diabetes mellitus (DM). METHODS: Six-week-old male SD rats (n = 120) were randomly divided into experimental (n = 80 rats) and control (n = 40 rats) groups. DM was induced in the experimental group (diabetic model) by intraperitoneal (i.p.) injection of 60 mg/kg streptozotocin (STZ). Control group rats were injected similarly with phosphate-buffered saline (PBS). Four and eight weeks after successful induction of DM, relative expressions of SIRT1 and P53 in LECs were analyzed using quantitative real-time (qRT) fluorescence polymerase chain reaction (qRT-PCR) and Western blot analysis. RESULTS: Expression of both SIRT1 and P53 was observed in LECs of control and experimental group rats at 4 and 8 weeks but was significantly greater in experimental compared with control group rats (p < 0.05). CONCLUSIONS: Expression of both SIRT1 and P53 increases in the early stages of diabetic cataract formation, indicating that they play potentially important roles in the pathogenesis of diabetic cataract.