Prediction of dissolved oxygen concentration in hypoxic river systems using support vector machine: a case study of Wen-Rui Tang River,China

Accurate quantification of dissolved oxygen (DO) is critically important for managing water resources and controlling pollution. Artificial intelligence (AI) models have been successfully applied for modeling DO content in aquatic ecosystems with limited data. However, the efficacy of these AI models in predicting DO levels in the hypoxic river systems having multiple pollution sources and complicated pollutants behaviors is unclear. Given this dilemma, we developed a promising AI model, known as support vector machine (SVM), to predict the DO concentration in a hypoxic river in southeastern China. Four different calibration models, specifically, multiple linear regression, back propagation neural network, general regression neural network, and SVM, were established, and their prediction accuracy was systemically investigated and compared. A total of 11 hydro-chemical variables were used as model inputs. These variables were measured bimonthly at eight sampling sites along the rural-suburban-urban portion of Wen-Rui Tang River from 2004 to 2008. The performances of the established models were assessed through the mean square error (MSE), determination coefficient (R ²), and Nash-Sutcliffe (NS) model efficiency. The results indicated that the SVM model was superior to other models in predicting DO concentration in Wen-Rui Tang River. For SVM, the MSE, R ², and NS values for the testing subset were 0.9416 mg/L, 0.8646, and 0.8763, respectively. Sensitivity analysis showed that ammonium-nitrogen was the most significant input variable of the proposal SVM model. Overall, these results demonstrated that the proposed SVM model can efficiently predict water quality, especially for highly impaired and hypoxic river systems.     

浙江省环境污染与经济发展关系的实证研究

本文在环境库兹涅茨曲线假设基础上,采用1991—2014年浙江省环境和经济数据,运用回归模型对其环境污染与经济发展的关系进行实证检验。结果表明:浙江工业废水、工业废气、工业SO2排放量和工业固体废弃物产生量均符合EKC假设,其中工业SO2和工业废水人均排放量与人均GDP呈倒U形关系,拐点分别出现在2005年与2010年;工业废气排放量和工业固体废弃物产生量尚处于倒U形左侧上升阶段,其中工业固体废弃物人均产生量已接近拐点。而生活污水排放量与EKC假设并不相符,人均生活污水排放量与人均GDP呈单调递增的线形关系。对EKC驱动因子的分析表明,加强政府环境治理,以不断完善的环境法规推动产业结构升级调整,以持续的技术进步与创新促进关键行业节能减排,有利于克服规模效应,推动浙江环境污染与经济发展的关系早日实现解耦。     

Application of hydration reaction on the removal of recalcitrant contaminants in leachate after biological treatment

Leachate contains amounts of non-biodegradable matters with COD range of 400–1500 mg/L after the biological treatment, and should be removed further to attain the Chinese discharge standards. Hydration reaction has the potential to combine and solidify some recalcitrant substances, and thus could be applied as the advanced leachate treatment process. It was found that COD and NH₃N decreased from 485 to <250 mg/L and 91 to 10 mg/L, with the removal rate over 50% and 90% in the first 6 d, respectively, and COD and NH₃N removal capacity were around 23.7 and 9.2 mg/g under the test conditions. The percentage of the substances with low Mn range of <1000 decreased from 32.9% to 3.2% in leachate after hydration reaction. Tricalcium aluminate, tricalcium silicate and dicalcium silicate were the most activity compounds successively for the pollutant removal in leachate, and hydration reaction could be the option for the advanced wastewater treatment process thereafter.     

The reductive degradation of 1,1,1-trichloroethane by Fe(0) in a soil slurry system

Most studies on the treatment of chlorinated contaminants by Fe(0) focus on aqueous system tests. However, few is known about the effectiveness of these tests for degrading chlorinated contaminants such as 1,1,1-trichloroethane (TCA) in soil. In this work, the reductive degradation performance of 1,1,1-TCA by Fe(0) was thoroughly investigated in a soil slurry system. The effects of various factors including acid-washed iron, the initial 1,1,1-TCA concentration, Fe(0) dosage, slurry pH, and common constituents in groundwater and soil such as Cl^?, HCO₃ ^?, SO₄ ^2?, and NO₃ ^? anions and humic acid (HA) were evaluated. The experimental results showed that 1,1,1-TCA could be effectively degraded in 12 h for an initial Fe(0) dosage of 10 g L^?1 and a soil/water mass ratio of 1:5. The soil slurry experiments showed two-stage degradation kinetics: a slow reaction in the first stage and a fast reductive degradation of 1,1,1-TCA in the second stage. The reductive degradation of 1,1,1-TCA was expedited as the mass concentration of Fe(0) increased. In addition, high pHs adversely affected the degradation of 1,1,1-TCA over a pH range of 5.4–8.0 and the reductive degradation efficiency decreased with increasing slurry pH. The initial 1,1,1-TCA concentration and the presence of Cl^? and SO₄ ^2? anions had negligible effects. HCO₃ ^? anions had a accelerative effect on 1,1,1-TCA removal, and both NO₃ ^? and HA had inhibitory effects. A Cl^? mass balance showed that the amount of Cl^? ions released into the soil slurry system during the 1,1,1-TCA degradation increased with increasing reaction time, suggesting that the main degradation mechanism of 1,1,1-TCA by Fe(0) in a soil slurry system was reductive dechlorination with 1,1-DCA as the main intermediate. In conclusion, this study provides a theoretical basis for the practical application of the remediation of contaminated sites containing chlorinated solvent.     

添加剂对堆肥降解多环芳烃的影响

为了研究多环芳烃(PAHs)污染土壤堆肥修复的加速机制,在人工控温的堆肥装置中以芘、菲和芴为研究对象,采用室内模拟实验的方式研究了添加硫酸钙、过磷酸钙、草炭、竹炭、十二烷基硫酸钠(K12)和十二烷基苯磺酸钠(SD-BS)等对锯末高温堆肥降解污染土壤PAHs的影响。研究结果表明,生物堆肥可以有效的去除土壤中PAHs,堆肥7周后所有处理下芘、菲和芴的降解率基本达到80%以上。不同添加剂处理下芘、菲和芴降解率不同,尤其是添加草炭和竹炭处理中芴和菲在第4周的时候就取得90%以上的降解率,芘在第6周也取得80%以上的降解率,而且氮素的损失率也分别下降了42.6%和36.09%,比其他处理的PAHs降解率和保氮效果都要好。分析其原因,一方面可能是添加不同添加剂对堆肥过程中pH值、有机质(SOM)、总氮(TN)和过氧化氢酶(CAT)都有一定的影响,提高了土壤微生物的活性;另一方面可能是由于草炭和竹炭对氨有良好的吸附性,具有良好的保氮效果,同时也能改善了微生物和目标化合物的接触方式,从而提高了PAHs的降解率。     

基于10辆轻型汽油车的实际行驶与台架工况排放特征及影响因素研究

利用便携式排放测试系统(Portable emission measurement system,PEMS)分析了10辆轻型汽油车分别在实验室台架和实际行驶排放(Real driving emission,RDE)工况下典型空气污染物的排放特征和影响因素.测试结果表明,轻型汽油车在冷启动和热启动阶段产生的一氧化碳(CO)、碳氢化合物(HC)、氮氧化物(NO_x)分别是热运行1阶段和热运行2阶段的28.0、32.9、28.4倍和4.0、11.2、5.4倍,表明车辆启动对机动车排放贡献显著.台架工况排放因子受车辆启动排放影响较大,在台架实验去除启动排放影响的情况下,台架CO₂、CO、HC和NOx排放因子将分别减小2.3%±1.3%、44.2%±30.6%、47.5%±29.6%和44.9%±30.8%.在相同速度下,RDE工况下的CO₂排放因子相比不考虑启动排放的台架工况排放因子要高出31.7%±5.0%.单车瞬态排放数据分析结果表明,RDE测试相比于台架工况测试覆盖了更多的机动车行驶工况特征,可以更准确地量化车辆在实际道路行...     

废包装容器定性问题研究

废包装容器源头分类管理较为混乱,近年来其非法转移利用或处置事件频发。通过废包装容器定性相关法律法规梳理,解读了目前废包装容器定性的三个关键问题,并从目前较为模糊的关键问题出发,重点辨析了含有或沾染的概念,阐述了毒性或感染性的判断方法及要点。感染性主要依据《医疗废物分类目录》确定;毒性可以从化学品分类方法、物料相关规范标准、《国家危险废物名录》中危险特性定性三个方面,对照危险废物毒性鉴别标准来综合评估。     

高层建筑火灾防烟空气幕的实验研究

通过分析高层建筑火灾时引起烟气流动的因素 ,建立了高层建筑火灾时防烟空气幕流量、吹风口宽度和吹风口的射流速度的计算模型。通过实验研究 ,验证了理论计算的正确性     

压力管道施工、检验和使用管理环节的探讨

本文以压力管道相关规范和日常工作实际为基础,对压力管道定义进行剖析,着重从使用单位角度上讨论了压力管道施工、检验和使用管理环节需要了解和注意的问题.通过本文对压力管道各管理环节的阐述,表明了压力管道管理的重要性,它需要各岗位人员意识到压力管道管理方面所承担的责任,需要各部门各岗位通力合作,通过过程管理实现本质安全.     

连云港东西连岛附近海域表层溶解氧含量多年变化趋势分析

对1995年-2005年国家海洋局连云港海洋环境监测站的溶解氧等数据进行了分析,结果表明,连云港东西连岛附近海域表层溶解氧含量多年来呈现增加的趋势,同时冬季平均含量高于春季,春季高于秋季,而夏季最低;东西连岛附近海域表层溶解氧含量与表层水温呈现良好的线性负相关关系,据此相关性可以获取表层溶解氧含量的动态变化值;此外,东西连岛附近海域表层溶解氧过饱和程度在2000年之后呈加剧趋势。