Mobility and sulfidization of heavy metals in sediments of a shallow eutrophic lake, Lake Taihu, China

The technique of DGT (diffusive gradients in thin films) using three diffusive gel thicknesses was applied to estimate the mobility and bioavailability of heavy metals in sediments and porewater of Lake Taihu, China. The DGT results showed significantly positive correlations between Co, Pb, Cd and Mn, and Ni and Fe concentrations in porewater. Cu and Zn showed a significantly negative correlation with Mn, due to Cu combination with carbonates and Zn derived from agricultural pollution, respectively. The rank order of average concentrations of Co, Ni and Cd at each station was DGT_1.92 > DGT_0.78 > DGT_0.39, suggesting stronger resupply from sediments to porewater when using thicker diffusive gels. Comparing centrifugation and DGT measurements, Co, Ni and Cd are highly labile; Mn and Fe are moderately labile; and Cu, Zn and Pb are slightly labile. The variations of AVS concentrations in sediment cores indicate that metal sulfides in deeper layers are easily diffused into surface sediments.     

基于模糊AHP模型的飞行评价体系

一种正确有效的飞行训练评估方法是保障飞行训练质量的必要前提和基础,而传统的评估方法多采用单一指标评价法或横向指标比较法,这种方法虽然简单易行,但没有充分考虑到评估体系自身的多样性,不能够真实反映飞行训练状态。本文提出了以模糊综合法为主体,专家评价、层次分析法相结合的综合评价方法,通过构造隶属度矩阵,建立飞行训练评估模型,克服了飞行教员评价的主观性,比较全面、客观的进行综合评估,量化计算过程,为真实、有效的飞行训练奠定基础。     

基于余震序列分布信息的地震极灾区快速判断方法研究

利用震级加权标准差椭圆法研究了基于震后短期内(24 h)余震序列判定地震极灾区的方法,研究结果表明:1利用该方法判断宏观震中是一种比较可行的方法,不同震源破裂方式的震例利用该方法判断宏观震中的精度不同,倾滑-近倾滑型破裂方式的震例利用余震序列判定宏观震中的精度最高;2整体上看,利用该方法判断极灾区长轴方向的准确性低于利用距震中最近活动断裂判断的准确性,但对于倾滑-近倾滑型破裂方式的震例,利用该方法的准确性高于利用断层数据判定的准确性。     

辽河口粪便污染指示菌的时空分布特征

2013年分别于夏季和秋季对辽河口海域的粪便污染指示菌(总大肠菌群、粪大肠菌群和肠球菌)及环境、水化学要素进行分析,研究粪便污染指示菌在海水中的数量、分布特征及其与环境、水化学指标间的相关性,在此基础上,选取河口地区合适的粪便污染指示菌.结果表明:夏季总大肠菌群数量在1.7×105~6.2×106CFU·L-1之间,粪大肠菌群数量在5.0×102~8.7×104CFU·L-1之间,肠球菌数量在1.0×101~2.5×102CFU·L-1之间;秋季总大肠菌群数量在5.0×102~1.1×105CFU·L-1之间,粪大肠菌群数量在4.0×102~1.0×103CFU·L-1之间,肠球菌数量在3~95 CFU·L-1之间.总大肠菌群、粪大肠菌群和肠球菌的数量变化与环境指标之间有着密切联系,特别是与盐度存在显著相关性;粪大肠菌群、肠球菌与水化学指标Si O4-4-Si、NH+4-N、TP和COD之间均存在显著相关性;其中粪大肠菌群与SiO4-4-Si和TP的相关性系数均大于0.742(p0.01),肠球菌与TP和COD的相关性系数均大于0.742.实验结果表明,辽河口粪便污染指示菌的数量在夏季高于秋季,近岸高于远海,其中粪大肠菌群和肠球菌的数量、分布特征与陆源污染物特别是氮磷的输入量密切相关,而且两者之间呈显著正相关关系.粪大肠菌群与肠球菌在一定程度上可以反映河口粪便污染情况,建议采用粪大肠菌群与肠球菌作为河口粪便污染的指示菌.     

Microcystis aeruginosa/Pseudomonas pseudoalcaligenes interaction effects on off-flavors in algae/bacteria co-culture system under different temperatures

We conducted an experiment to study the interaction effects of Microcystis aeruginosa and Pseudomonas pseudoalcaligenes on off-flavors in an algae/bacteria co-culture system at three temperatures (24, 28 and 32°C). Gas chromatography–mass spectrometry was applied to measure off-flavor compounds dimethyl sulfide (DMS), dimethyl trisulfide (DMTS), 2-methylisoborneol, geosmin (GEO) and β-cyclocitral. During the lag phase of co-cultured M. aeruginosa (first 15 days), P. pseudoalcaligenes significantly increased the production of DMS, DMTS and β-cyclocitral at all three temperatures. In the exponential phase of co-cultured M. aeruginosa (after 15 days), M. aeruginosa became the main factor on off-flavors in the co-culture system, and β-cyclocitral turned to the highest off-flavor compound. These results also indicated that DMS, DMTS and β-cyclocitral were the main off-flavor compounds in our M. aeruginosa/P. pseudoalcaligenes co-culture system. Univariate analysis was applied to investigate the effects of M. aeruginosa and P. pseudoalcaligenes on the production of off-flavors. The results demonstrated that both M. aeruginosa and P. pseudoalcaligenes could increase the production of DMS and DMTS, while β-cyclocitral was mainly determined by M. aeruginosa. Our results also provide some insights into understanding the relationship between cyanobacteria and heterotrophic bacteria.     

Mobility and sulfidization of heavy metals in sediments of a shallow eutrophic lake,Lake Taihu,China

The technique of DGT (diffusive gradients in thin films) using three diffusive gel thicknesses was applied to estimate the mobility and bioavailability of heavy metals in sediments and porewater of Lake Taihu, China. The DGT results showed significantly positive correlations between Co, Pb, Cd and Mn, and Ni and Fe concentrations in porewater. Cu and Zn showed a significantly negative correlation with Mn, due to Cu combination with carbonates and Zn derived from agricultural pollution, respectively. The rank order of average concentrations of Co, Ni and Cd at each station was DGT_1.92 > DGT_0.78 > DGT_0.39, suggesting stronger resupply from sediments to porewater when using thicker diffusive gels. Comparing centrifugation and DGT measurements, Co, Ni and Cd are highly labile; Mn and Fe are moderately labile; and Cu, Zn and Pb are slightly labile. The variations of AVS concentrations in sediment cores indicate that metal sulfides in deeper layers are easily diffused into surface sediments.     

Microcystis aeruginosa/Pseudomonas pseudoalcaligenes interaction effects on off-flavors in algae/bacteria co-culture system under different temperatures

We conducted an experiment to study the interaction effects of Microcystis aeruginosa and Pseudomonas pseudoalcaligenes on off-flavors in an algae/bacteria co-culture system at three temperatures(24, 28 and 32℃). Gas chromatography–mass spectrometry was applied to measure off-flavor compounds dimethyl sulfide(DMS), dimethyl trisulfide(DMTS),2-methylisoborneol, geosmin(GEO) and β-cyclocitral. During the lag phase of co-cultured M. aeruginosa(first 15 days), P. pseudoalcaligenes significantly increased the production of DMS, DMTS and β-cyclocitral at all three temperatures. In the exponential phase of co-cultured M. aeruginosa(after 15 days), M. aeruginosa became the main factor on off-flavors in the co-culture system, and β-cyclocitral turned to the highest off-flavor compound. These results also indicated that DMS, DMTS and β-cyclocitral were the main off-flavor compounds in our M. aeruginosa/P. pseudoalcaligenes co-culture system. Univariate analysis was applied to investigate the effects of M. aeruginosa and P. pseudoalcaligenes on the production of off-flavors. The results demonstrated that both M. aeruginosa and P. pseudoalcaligenes could increase the production of DMS and DMTS, while β-cyclocitral was mainly determined by M. aeruginosa. Our results also provide some insights into understanding the relationship between cyanobacteria and heterotrophic bacteria.     

酸浸法回收制革污泥中的铬

利用硫酸酸浸提取制革污泥中的金属铬,研究了固液比、酸浓度、浸出时间、温度和搅拌速度等因素对浸出效率的影响,并获得最优浸出条件。结果表明,最优浸出条件为:固液比10g/L,硫酸浓度0.5mol/L,浸出温度50℃,浸出时间1.5h。搅拌速度对硫酸浸出铬影响较小。经硫酸二次浸出铬的效率达到90.95%。因此,用硫酸酸浸的方法提取制革污泥中的铬是可行的。     

运用正弦扫频实现电动振动台模型的频域辨识

目的研究以电动振动台为典型设备的相关振动试验装置的频域辨识技术。方法通过分析电动振动台数学模型,采用正弦扫频试验方法,进行全频带振动台空台面正弦扫频,并对所获得的时域正弦扫频数据进行频谱分析,进而获得系统的频率数据,再运用复数域上的最小二乘拟合算法,完成振动台模型传递函数的辨识。结果通过某型电动台空台面试验,对一组实测数据进行辨识,辨识出的电动振动台模拟与真实模拟一致。结论通过该方法并合理选取模型结构,能够很好地辨识出振动试验装置的模型。     

甘肃南部典型城镇PM2.5浓度及水溶性离子特征分析

为研究甘肃南部城镇PM_2.5及水溶性离子（WSIIs）浓度水平,于2019年4月—2020年2月在甘肃成县按季度进行PM_2.5样品采集,分析了其变化特征,并运用相关和主成分分析法进行来源解析.结果表明：采样期间甘肃成县PM_2.5年平均质量浓度为（57.2±26.9） μg·m^-3,表现为冬季>春季>秋季>夏季的季节变化特征,冬季质量浓度约为夏季的1.9倍,全年空气质量优良率为81%,其中夏季达100%.WSIIs质量浓度呈现SO₄^2->NO₃^->Na⁺>NH₄⁺>Ca²⁺> K⁺>Cl^->Mg²⁺的特征.SNA是浓度水平最高的3种水溶性离子,占8种主要水溶性离子浓度的70.1%.ρ（NO₃^-）/ρ（SO₄^2-）平均值为0.6,表明工农业生产及化石燃料燃烧排放等固定源是颗粒物污染的主要来源.新型冠状病毒疫情期间人员管控对PM_2.5和水溶性离子中SNA质量浓度影响显著,PM_2.5平均质量浓度降幅达44.2%.源解析表明,PM_2.5中WSIIs主要来自化石燃料燃烧、生物质燃烧及二次源和道路建筑扬尘等.