[Estimate the abatement rate of septic tank sewage outfall soil on nitrogen pollutants of typical farmer household sewage].

The surface soil on sewage outfall and effluent of farmer household septic tank were collected in situ from the typical region of plain river network areas in Taihu Lake Basin, and the typical rainfall (summer 30 mm . times-1, winter 5 mm times -1), temperature (summer 27 degrees C, winter 5 degrees C ) condition and pollutant load were artificial simulated by indoor simulation soil column experiments for estimating nitrogen abatement rate of rural sewage treated by the outfall soil and exploring the abatement rule in different seasons and weather process (7 days before the rain, 3 rainy days, 7 days after the rain). Results showed that: there was the significant difference (P <0.05) in abatement/increase rate of outfall soil on nitrogen between summer and winter. The TN abatement rate, NO-3 -N increase rate of summer showed a significant difference (P <0.01) among different weather processes, but the NH+4 -N abatement rate of summer and the TN, NH+4 -N abatement rate, NO -N increase rate of winter were not significant (P > 0. 05). Therefore, the TN, NH+4 -N abatement rate, NO-3 -N increase rate need to be divided by seasons, TN abatement rate, NO-3 -N increase rate of summer need to be divided by the weather process, which were 38.5% , - 25.0% , 46. 0% and 478. 1%, 913.8%, 382. 0% , before the rain, in rainy day, after the rain, respectively; while the NH+4 -N abatement rate of summer and the TN, NH+4 -N abatement rate, NO-3 -N increase rate of winter do not need to be divided by weather process, were 91.7% , 50.4% , 85.5% and 276.0% , respectively. In the summer, the TN abatement rate in different weather processes was not correlated with NH+4 -N abatement rate, but significantly negative correlated with NO-3 -N increase rate. In the winter, the stable accumulation of TN in soil was an important reason of the TN abatement rate which had no significant difference and kept a high level among different weather processes, and it was closely related to the stable accumulation of NH+4 -N in soil.

[Impact of dissolved organic matter on plant uptake of phenanthrene and its mechanisms].

Hydroponic assays were conducted to investigate the influence of dissolved organic matter on uptake of phenanthrene by wheat as well as its mechanisms. The results showed that, under hydroponic condition, phenanthrene impairment of plant growth occurred with wheat growth inhibited rate of 18.01%. The impairment would be greatly enhanced in the presence of dissolved organic matter (DOM) derived from pig manure, and the inhibited rate increased to 24.38%. Wheat could uptake and accumulate phenanthrene in the nutrient solution, which could be escalated by DOM, as indicated by wheat root bioconcentration factor being increased to 37.63 L x kg(-1) in the presence of DOM from 2.84 L x kg(-1) in the absence of DOM. At the same time, DOM could facilitate phenanthrene translocation from plant roots to the upper. As a result, the pH value of nutrient solution could increase by more than 1 unit when the co-existence of DOM and phenanthrene occurred in solution, suggesting that H+ -phenanthrene cotransport system is involved in the uptake of phenanthrene by plants. A synergism was also found between wheat uptakes of phenanthrene and inorganic nutrients, Moreover, DOM accelerated markedly the synergism. It is concluded that DOM affects the uptake of phenanthrene by plants and the environmental behaviors of phenanthrene.

[Influence of dissolved organic matter on the eco-toxicity of phenanthrene in a soil].

Biological and physico-chemistry experiments were conducted to study the effects of dissolved organic matter (DOM) on eco-toxicity of phenanthrene in a soil. The results showed that DOM was a kind of surfactant. The sensitive range of phe inhibiting wheat root elongation was from 0 to 200 mg/kg, and median inhibition concentration (IC50) was 200 mg/kg. In the presence of DOM, the eco-toxicity of phe could be alleviated and the inhabited degree was related to the content of hydrophobic components and surface activity. This effect could be strengthened by the high concentration of DOM. As a kind of hydrophobic organic compound, phe could reduce the moisture of topsoil, and DOM would slightly increase the moisture of topsoil polluted by phe. It was concluded that DOM could lighten the eco-toxicity of phe in soil.