活性污泥数学模型中异养菌产率系数的测定

活性污泥数学模型常被用于预测污水处理厂中的生物过程。模型中异养菌产率系数YH对其他组分的测定值有显著的影响。目前．测定YH的主要方法有序批式活性污泥法和序批式呼吸计量法。在序批式呼吸计量法中．起始F／M值的选择十分关键。以醋酸钠为底物．对这两种方法进行了分析比较,序批式呼吸计量法为文章的推荐方法。     

森林火灾地面扑救的最佳路线的计算

建立了森林火灾地面扑救方式(直接扑救、间接扑救和平行扑救)的最佳扑救路线的数学模型,设计了模型的计算机数值求解算法。给出了匀速扩张的椭圆形火场的一个算例,从其计算结果中导出的一些实用的结论与以往用解析方法得到的结论是一致的,以此初步验证了模型的有效性。     

基于机器学习的大气PM2.5中金属浓度预测模型的研究

基于2013—2018年哈尔滨市气象数据、大气污染物数据和细颗粒物（PM_2.5）中金属成分数据,采用机器学习方法探索大气PM_2.5中金属浓度预测模型,并选择最优模型进行污染物浓度预测。结果表明,多元线性回归（MLR）、人工神经网络（BP-ANN）、支持向量机（SVM）和随机森林（RF）4种模型中,RF对大气PM_2.5中5种金属［锑（Sb）、砷（As）、铅（Pb）、镉（Cd）、铊（Tl）］的浓度预测效果最佳,在训练集和测试集中表现均较稳定,其中相关系数（r）均＞0.7, 平均绝对误差（MAE）和均方根误差（RMSE）数值较小。RF在大气PM_2.5中金属浓度预测上具有较好的表现,可在缺乏监测和实验数据的情况下,实现对大气颗粒物中金属浓度的快速预测,为全面了解颗粒物中金属污染特征提供数据基础。     

干旱荒漠区人工绿洲土壤盐碱化风险综合评估与演变分析

为明晰干旱荒漠区人工绿洲水盐时空分异特征与盐碱化风险空间格局演变过程,以甘肃省景电灌区为研究区,以2002,2010及2018年为研究代表年,基于多级模糊理论从地质气候驱动、水土环境驱动和自然-人类驱动3个驱动过程构建土壤盐碱化风险评估体系,集成云发生器原理、黄金分割率法、组合赋权法以及排队理论构建土壤盐碱化空间风险综...     

三唑酮对大型溞21天慢性毒性效应

三唑类杀菌剂是一种在农业上广泛应用的广谱性杀菌剂。三唑类杀菌剂在农田施用后能够向土壤深处迁移和扩散,从而污染土壤和地下水体,因此三唑类杀菌剂对土壤生态环境能够造成一定的破坏。选择三唑酮为研究对象,参照经济合作与发展组织(Organization for Economic Co-operation and Developement,OECD)标准方法研究三唑酮对大型溞的慢性毒性效应。21d慢性毒性研究结果表明,大型溞繁殖指标-内禀增长率是对三唑酮最为敏感的毒性参数。其慢性毒性下限值(LCL)和慢性毒性上限值(UCL)分别为40和80μg·L-1。三唑酮对于第2代大型溞,染毒的影响比对第1代的影响更大。对第2代恢复的大型溞除了第1次产卵数没有显著性差异,其他指标都有所变化,这说明毒物被转移到子代中。     

Calcite-seeded crystallization of calcium phosphate for phosphorus recovery

For phosphorus recovery from wastewater, the present paper aims at understanding the crystallization of calcium phosphate by using calcites (Juraperle and Coccolith) as seeds from hard water. Synthetic hard water with 60 mgCl(-1) carbonate and 10 mgPl(-1) phosphate was prepared and used in the batch experiments of calcite-seeded crystallization. The solution composition was measured throughout the batch crystallization process, and the corresponding saturation indices with respect to the minerals were calculated with PHREEQC Program. The surface of the calcite seeds was observed and measured with environmental scanning electron microscopy (ESEM), Fourier transform infrared (FTIR) and BET method. The studies show that both calcites are effective seeds for the crystallization of calcium phosphate from hard water; the used calcites are more efficient than the original ones because newly formed crystals with calcium phosphate have covered their surfaces. The studies show that the calcite seeds can be used for phosphorus recovery from hard waters.     

水库大型围隔放养鲢鱼、鳙鱼控藻的研究

为减轻水源地水华的发生,在天津于桥水库建立了10个300m2大型围隔,分别放养密度为0,10,30,60g/m3的鲢鱼、鳙鱼进行控藻试验.结果表明,无鱼围隔内的蓝藻比例上升并形成微囊藻水华,各有鱼围隔内蓝藻比例始终保持在低位水平.与此同时,鲢鱼、鳙鱼的滤食导致小型藻类的大量增长进而造成藻类总生物量及叶绿素a不同程度地升高.由此可知,鲢鱼、鳙鱼适用于控制蓝藻水华而非藻类总量.     

Trace metal contents of the pacific oyster (Crassostrea gigas) purchased from markets in Hong Kong

Arsenic, cadmium, chromium, and copper concentrations of the Pacific oyster,Crassostrea gigas, purchased from four different markets were determined in this project. In general, gill tissue had the highest proportion of metal contents (34%–67%) when compared with other tissue parts (mantle, viscera, and adductor muscle), except for arsenic, which showed the highest level in adductor muscle (44%). Smaller oysters (longitudinal length of soft body part less than 6 cm) had higher metal levels than larger ones (longitudinal length of soft body part more than 6 cm), except copper. None of the four metals examined showed an obvious seasonal trend, although cadmium levels seemed to be higher in autumn and winter months. Arsenic, cadmium, and copper levels in oysters purchased from different markets and different months obtained in the present study were higher when compared with past reports. Cadmium levels, as high as 10.98 mg/kg (dry weight basis) have been obtained. This approaches the safety limit that may be hazardous to human health. Continual monitoring of cadmium and other trace metals of toxicological significance to man in Hong Kong seafood is recommended.