城市黑臭河道夏季产甲烷通量研究——以南宁市朝阳溪为例

利用静态箱法测定城市黑臭河道!南宁市朝阳溪夏季产甲烷通量,结果表明朝阳溪是重要的甲烷排放源,夏季甲烷排放通量平均值为12.2mg/(m2·h),上游、中游、下游排放通量变化不显著。利用偏最小二乘法进行相关性分析可得,甲烷通量与温度、化学需氧量、底泥有机碳呈显著正相关,与溶解氧呈显著负相关,与总氮、氨氮、总磷、pH相关性较小。     

基于PCA-LSSVM的厌氧废水处理系统出水VFA在线预测模型

采用IC厌氧废水处理系统处理人工合成废水,并利用PCA-LSSVM模型对系统出水挥发性脂肪酸(VFA)进行预测.首先利用主成分分析法(PCA)分析影响厌氧废水出水VFA浓度的多个变量的相关性并降低输入变量维数,然后用网格搜索结合10倍交叉验证优化LSSVM模型参数sig2和gam,最后利用建立的模型对实验数据进行仿真预测.仿真结果表明,稳态LSSVM模型对稳态条件下厌氧废水处理系统出水VFA具有很好的仿真预测能力,相对误差在4.72%以内,平均相对百分比误差(MAPE)为1.61%,均方根误差(RMSE)为1.08,相关系数达0.9996;稳态干扰LSSVM模型对厌氧废水处理系统出水VFA的仿真预测精度有所降低但仍然具有较好的预测能力,平均相对百分比误差(MAPE)为15.83%,均方根误差(RMSE)为15.45,相关系数为0.9984,该方法可为厌氧出水VFA在线预测和厌氧废水处理系统的优化控制提供指导.     

Effect of Water Variables On Lead Tolerance in Postlarvae of Penaeus Indicus (H. Milne Edwards)

Lead tolerance in Penaeus indicus post-larvae (PL) was studied in relation to the water variables: salinity, temperature and pH. the LC₅₀ for 96 hrs was 7.22 ppm at ambient conditions of salinity (20%_o), temperature (29°C) and pH (7.2). the post-larvae were found to be sensitive to salinity variations with a significant (P < 0.05) low LC₅₀ values at lower (2%_o) and higher (29%_o) ranges. Though a decrease in LC₅₀ value was observed both at higher (45°C) and lower (10°C) temperatures, it was significantly (P < 0.05) low only at higher temperature indicating more toxicity. the LC₅₀ values also showed a significant (P < 0.05) decrease in acidic (pH 2.8) and alkaline (pH 11.0) conditions. the data indicate that lead toxicity increases in the PL of P. indicus with variations in the water variables.     

Opposite response of phosphorus sorption to pH and ionic strength: a comparative study in two different shallow lake sediments

Phosphorus (P) sediment sorption is regarded as the most important buffering process against P increases in overlying water. In this study, two shallow eutrophic sediments (Mei and Hua) with distinct compositions were selected to assess effects of pH (from 6 to 9) and ionic strength (IS) (0, 0.001, 0.01 and 0.1 M KCl) on P sorption. In Mei sediments, the P sorption decreased as pH increased (6.97–9.13), but it increased as IS increased over the pH range in question. These results could be attributed to the negatively charged surface of Mei sediments, as indicated by the salt titration curve, and the high cation exchange capacity (CEC). P sorption in Hua sediments was facilitated by a pH increase (6.12–7.49), but it was hindered by an IS increase. A reasonable explanation for this phenomenon is that calcium phosphate precipitates at high pHs and that Cl^? exchanges with P because the surface is weakly charged (small CEC). These results indicate that the sediment P sorption may have trends opposite to one another in relation to the salt change (e.g. drought and rainy season) in the lake water between the two sediments. These data provide additional support to explain P concentration variations in lakes.     

Evidence for Ph Insensitivity in Some Insects Inhabiting Peat Pools in the Loch Fleet Catchment

The impact of liming on the insects associated with peat pools was studied in the Loch Fleet catchment in 1991 and 1992. Fifty-six taxa were identified from 121 timed samples. Despite the raised pH associated with liming in 1986, the population densities of Odonata, Hemiptera and Coleoptera appeared to be unaffected when compared with those of untreated peat pools in the same area. the study demonstrated the existence of two main types of community, that of the steep-sided edges of pools, dominated by odonate nymphs and large species of beetles, and that of the shallower pools, dominated by Hydroporus species (Col., Dytiscidae).     

Ionic contribution to the self-potential signals associated with a redox front

In contaminant plumes or in the case of ore bodies, a source current density is produced at depth in response to the presence of a gradient of the redox potential. Two charge carriers can exist in such a medium: electrons and ions. Two contributions to the source current density are associated with these charge carriers (i) the gradient of the chemical potential of the ionic species and (ii) the gradient of the chemical potential of the electrons (i.e., the gradient of the redox potential). We ran a set of experiments in which a geobattery is generated using electrolysis reactions of a pore water solution containing iron. A DC power supply is used to impose a difference of electrical potential of 3 V between a working platinum electrode (anode) and an auxiliary platinum electrode (cathode). Both electrodes inserted into a tank filled with a well-calibrated sand infiltrated by a (0.01 mol L^− 1 KCl + 0.0035 mol L^− 1 FeSO₄) solution. After the direct current is turned off, we follow the pH, the redox potential, and the self-potential at several time intervals. The self-potential anomalies amount to a few tens of millivolts after the current is turned off and decreases over time. After several days, all the redox-active compounds produced initially by the electrolysis reactions are consumed through chemical reactions and the self-potential anomalies fall to zero. The resulting self-potential anomalies are shown to be much weaker than the self-potential anomalies observed in the presence of an electronic conductor in the laboratory or in the field. In the presence of a biotic or an abiotic electronic conductor, the self-potential anomalies can amount to a few hundred millivolts. These observations point out indirectly the potential role of bacteria forming biofilms in the transfer of electrons through sharp redox potential gradient in contaminant plumes that are rich in organic matter.     

温度和pH值对重组杆状病毒(AcMNPV-BmKIT-Chi)的毒力影响

研究了温度、酸碱度对重组杆状病毒(AcMNPV-BmKIT-Chi)毒力的影响.结果显示,多角体病毒在温度4~50℃,pH6.0~8.0范围内可以保持较高的毒力稳定性;不同虫龄棉铃虫幼虫对重组病毒的毒力敏感性差异显著,低虫龄对重组核型多角体病毒更为敏感;病毒对幼虫存在亚致死作用,饲毒组与对照组幼虫体重差异显著.图3表3参13     

Forecasting energy demand of China using Bayesian Combination model

To analyze the impact of the related economic factors on China's energy demand, Path analysis is used to analyze the major factors and their direct and indirect effects on energy demand. This study showed that the main factors that affect the energy demand are the economic growth, the total population, and the primary energy structure, the economic growth is the main determining factor, and the primary energy structure is the major restrictive factor. On this basis and considering the multicollinearity and the validity of the forecast, we established a partial least-square (PLS) and the trend extrapolation prediction model, and then we sum up all the information to found a PLS—trend extrapolation combination forecasting model based on the optimized combining forecast theory. Finally, we obtain the probability distribution of the error using the Bayesian statistic theory and find the confidence interval of combining forecasting result. The results indicate that the outcome of combining forecasting will be more precise after using the Bayesian error correction approach.