[Bioavailability of Silicon Fertilizer Coupled Water Management on Soil Bioavailability and Cumulative Control of Rice in Compound Contaminated Paddy Soils].

The effect of wet irrigation (CK), agronomic measure flooding (WF), instantaneous silicon fertilizer combined with flooding measures (FYsi), mineral silicon fertilizer combined with flooding measures (FKsi), and a mix of two kinds of silicon fertilizer combined with flooding measures (FYK) on the bio-availability of As and Cd in soil and the accumulation of As and Cd in rice were investigated by pot experiments. The results showed that the pH of the soils combined with flooding measures was increased by 0.12-0.72 units with similar trends of an increase and then a decrease before finally become neutral. The Eh of the soil combined with flooding was significantly decreased, but the Eh of soil after flooding treated by FYsi, FKsi, and FYK combined with the flooding was significantly higher than that treated by WF, and the content of Cd in brown rice was reduced by 38.83%-65.05% compared with that treated by CK. The WF and FYK treatments can significantly reduce the accumulation of Cd in brown rice, resulting in the lowest Cd contents in brown rice of 0.98 and 0.72 mg·kg-1, respectively. The contents of As in brown rice treated by FYsi, FKsi, and FYK were decreased by 23.80%, 38.10%, and 47.62%, respectively, compared with that with the CK treatment, except that the content of As in brown rice treated by WF increased by 36.64%. FYsi and FYK treatments had the best inhibitory effect on the accumulation of As in brown rice, with the lowest As contents of 0.13 mg·kg-1 and 0.11 mg·kg-1 in brown rice (P <0.01), respectively. There was an extremely significant correlation between the contents of extractable Cd and the total content of Cd in the brown rice (P <0.05), and there was no significant difference between the contents of extractable As and the total content of As in the brown rice. Therefore, FYsi, FKsi, and FYK can effectively inhibit the accumulation of Cd and As in rice grown in Cd-As compound polluted soil, and FYK showed the best performance.

[Effects of protein kinase C and motigen-activated protein kinase kinase/extracellular regulated protein kinases signaling pathway on mRNA level of inducible nitric oxide synthase in Tca8113 cells].

OBJECTIVE: To explore the regulatory mechanism of inducible nitric oxide synthase (NOS-2) expression related to proliferation of Tca8113 cells. METHODS: RNAi mediated by short hairpin RNAs was utilized to knock down NOS-2, protein kinase C (PKC)-α, PKC-ß and PKC-δ. Griess Reagent played a significant role on the detection of NO product after NOS-2 silence. The cell proliferation was determined by CCK8 method. Quantitative real-time polymerase chain reaction (q-PCR) was recruited to check the mRNA level of NOS-2, PKC-α, PKC-ß and PKC-δ after treated by a variety of ways. Eventually, the measure of phosphorylation of extracellular regulated protein kinases (ERK)1/2 was performed by Western blotting in PMA-treated Tca8113 cells. RESULTS: The cell viability of Tca8113 decreased obviously after transfected with NOS-2 siRNA (P<0.01). PKC reduced the expression level of NOS-2 mRNA (P<0.05). PKC-α, PKC-ß and PKC-δ worked together to regulate the level of NOS-2 mRNA (P<0.01). Motigen-activated protein kinase kinase (MEK)/ERK signaling pathway regulated the level of NOS-2 mRNA negatively (P<0.05). PKC down regulated the level of NOS-2 mRNA through MEK/ERK signaling pathway (P<0.05). CONCLUSIONS: PKC regulates the mRNA level of NOS-2 related to proliferation through MEK/ERK signaling pathway in Tca8113 cells.

[Major Factors Influencing the Cd Content and Seasonal Dynamics in Different Land Cover Soils in a Typical Acid Rain Region].

Understanding the seasonal variations in active heavy metal components and sensitive impact factors is of importance for the ecological risk reduction during the agricultural production processes. Paddy fields, vegetable lands, and hilly forests were selected as three main land cover types to assess the seasonal characteristics of Cd bioavailability and reveal how or to what extent it was affected by the physiochemical parameters of soils, under different land-use types in a typical Cd-contaminated watershed in the middle and lower reaches of Xiangjiang River. One-year in situ monitoring results showed that natural rainfall pH in winter and spring was lower than in summer and autumn in the study region. The total Cd content of paddy soils was significantly higher than that of the vegetable soil, while the hilly forest soil showed the lowest total Cd value. Similar seasonal variations in total Cd content were found in three soil types with slightly lower summer and autumn concentrations than spring and winter values, but no obvious correlation was detected between the total and the available Cd components. The paddy soil available Cd concentration during the 5-9-month crop growth season was significantly lower than the other months of the year, while vegetable cultivation and hilly forest soils showed the opposite trend. Eh was the key factor that had a positive influence on the Cd activity in paddy soil. Soil TOC concentration was negatively correlated with soil activity in vegetable soil. TOC, water soluble organic carbon, showed a significant positive correlation with Cd effectiveness. The results provide scientific references for Cd contamination control and safe agricultural production.

[Phytoexclusion potential studies of Si fertilization modes on rice cadmium].

The research used serious situ multi-metal contaminated soils to explore Cd repair potential in rice by adding different kinds of fertilizers, based on the outdoor pot experiment. The experiment was consisted of four treatments including non-used fertilizers (CK), the silicon fertilizer applicated into soil (Tsi), the silicon fertilizer applicated as foliar spray (Ysi) and the silicon fertilizer applicated into soil combined with the foliar spray silicon fertilizer application( Tsi + Ysi). The research examined Cd concentrations in tissues of five key growth periods to reveal cadmium (Cd) migration rules, translocation coefficients, rice biomass and yields. The results showed that, compared to CK, different fertilization methods of Si had significant impacts on decreasing Cd in brown rice and polished rice, but not in rice yields; In addition, Tsi + Ysi had the best effects to decrease Cd in edible grains, which resulted in Cd concentrations of husk, brown rice and polished rice reduced by 62.59%, 58.33% and 65.83%, respectively, and the effects of applying Tsi and Ysi were the second. Therefore, Tsi, Ysi and Tsi + Ysi were confirmed to be potential Cd pollution control technologies to rice.

[Non-point loads of soluble cadmium by in situ field experiment with different landuses, in central Hunan province mining area].

Non-point source loads of heavy metals from contaminated soil has increasingly become the major cause of heavy metal concentrations of rivers and lakes surpassed the limitation value, while only few studies had focused on quantitative monitoring of soil heavy metal transportation to water, in situ field conditions. As reported, agricultural farmland heavy metal contamination was the major contamination problem, especially for cadmium (Cd) pollution in middle and downstream of Xiangjiang River. This study selected the typical Cd polluted agricultural watershed for a case study, three typical landuse types of rice, dry farmland and unused grassland with three replicate quadrates were carried out for natural rainfall runoff hydrology processes monitoring, from 2011-2012. Results showed that, precipitation pH value increased from spring to summer, soluble Cd concentration of spring runoff was significantly higher than that of summer rainfall runoff, which presented an obviously seasonal heterogeneity and had a negative correlation with rainfall pH value, and rainfall pH value can obviously impact soil soluble Cd transportation into surface runoff charge. In the same rainfall event, soluble Cd concentration and non-point load of rice were significantly lower than those of dry land and unused grassland, while no obviously seasonal trend was found for non-point load of Cd from three typical landuse types because of the rainfall depth variance, which needs more researches and concerns in the future. These results can provide valuable data and scientific supports for watershed scale's heavy metal non-point source load quantitative estimation and water environment management and water quality diagnosis and early warning.