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排序方式: 共有891条查询结果,搜索用时 78 毫秒
561.
562.
采用数值模拟计算的方法分别对批处理缓蚀剂和连续处理缓蚀剂在某天然气集输管道内的分布规律进行研究,根据缓蚀剂在管道顶部和底部的分布规律,通过腐蚀模拟试验分别研究了管道的底部和顶部腐蚀行为.结果表明:在天然气流作用下,批处理缓蚀剂膜在管道内部分布不均,缓蚀剂膜在管道顶部的厚度低于管道底部,弯头内侧的批处理缓蚀剂膜明显减薄;连续处理缓蚀剂在重力作用下主要沉降在管道底部,仅弯头的顶部受少量缓蚀剂的保护.在批处理缓蚀剂和某一浓度的连续处理缓蚀剂作用下,管道底部的腐蚀基本上得到了控制,但管道顶部发生了明显的局部腐蚀. 相似文献
563.
上海市城乡梯度上土壤重金属空间分布及其影响因素定量分析 总被引:2,自引:1,他引:1
提出了两种上海市城乡梯度上土壤重金属空间格局及影响因素的研究方法:缓冲区分析方法和滑动窗口分析方法.缓冲区分析的结果表明,人口变化指数及2~3 km范围内的建设用地比例能显著影响Cd和Cu的空间分布(p0.05),而3 km范围内的道路密度显著影响Pb的浓度.滑动窗口分析的结果表明,Cd和Cu主要受工业活动的影响,而Pb受交通流量,以及反映城市景观扩张过程的景观形状指数的影响.相关分析表明,两种方式揭示了较为相似的土壤重金属空间累积影响因素,即工业活动相关的城市化过程.研究对理解城市化的发生机制及其重金属环境风险的管理有重要意义. 相似文献
564.
Adsorption behavior of sulfamethazine in an activated sludge process treating swine wastewater 总被引:1,自引:0,他引:1
Swine wastewater is an important pollution source of antibiotics entering the aquatic environment. In this work,the adsorption behavior of sulfamethazine(SMN),a commonlyused sulfonamide antibiotic,on activated sludge from a sequencing batch reactor treating swine wastewater was investigated. The results show that the adsorption of SMN on activated sludge was an initially rapid process and reached equilibrium after 6 hr. The removal efficiency of SMN from the water phase increased with an increasing concentration of mixed liquor suspended solids,while the adsorbed concentration of SMN decreased. Solution pH influenced both the speciation of SMN and the surface properties of activated sludge,thus significantly impacting the adsorption process. A linear partition model could give a good fit for the equilibrium concentrations of SMN at the test temperatures(i.e.,10,20 and 30°C). The partition coefficient(Kd) was determined to be 100.5 L/kg at 20°C,indicating a quite high adsorption capacity for SMN. Thermodynamic analysis revealed that SMN adsorption on activated sludge was an exothermic process. This study could help to clarify the fate and behavior of sulfonamide antibiotics in the activated sludge process and assess consequent environmental risks arising from sludge disposal as well. 相似文献
565.
566.
Chemical and optical properties of aerosols and their interrelationship in winter in the megacity Shanghai of China 总被引:2,自引:0,他引:2
Tingting Han Liping Qiao Min Zhou Yu Qu Jianfei Du Xingang Liu Shengrong Lou Changhong Chen Hongli Wang Fang Zhang Qing Yu Qiong Wu 《环境科学学报(英文版)》2015
A field campaign on air quality was carried out in Shanghai in winter of 2012. The concentrations of NO, NO2, NOx, SO2, CO, and PM2.5 increased during haze formation. The average masses of SO42-, NO3- and NH4+ were 10.3, 11.7 and 6.7 μg/m3 during the haze episodes, which exceeded the average (9.2, 7.9, and 3.4 μg/m3) of these components in the non-haze days. The mean values for the aerosol scattering coefficient (bsp), aerosol absorption coefficient (bap) and single scattering albedo (SSA) were 288.7, 27.7 and 0.91 Mm-1, respectively. A bi-peak distribution was observed for the mass concentrations of CO, NO, NO2, and NOx. More sulfate was produced during daytime than that in the evening due to photochemical reactions. The mass concentration of NH4+ achieved a small peak at noontime. NO3- showed lower concentrations in the afternoon and higher concentrations in the early morning. There were obvious bi-peak diurnal patterns for bsp and bap as well as SSA. bsp and bap showed a positive correlation with PM2.5 mass concentration. (NH4)2SO4, NH4NO3, organic mass, elemental carbon and coarse mass accounted for 21.7%, 19.3%, 31.0%, 9.3% and 12.3% of the total extinction coefficient during non-haze days, and 25.6%, 24.3%, 30.1%, 8.1% and 8.2% during hazy days. Organic matter was the largest contributor to light extinction. The contribution proportions of ammonium sulfate and ammonium nitrate to light extinction were significantly higher during the hazy time than during the non-haze days. 相似文献
567.
Polycyclic aromatic hydrocarbons (PAHs) in atmospheric dustfall from the industrial corridor in Hubei Province,Central China 总被引:1,自引:0,他引:1
568.
569.
The effects and mechanism of chemical oxygen demand (COD), nitrogen, and phosphorus concentration removal by an integrated vertical-flow constructed wetland were studied in the wetland system during one inlet–outlet operating period, in two typical stages (each stage is connective 24 h, sampled once every 4 h). The concentration of ammonia decreased along the flow direction in the system, while levels of nitrate (NO3?-N) increased. In one operating period, total nitrogen (TN) concentration fell with rising operation time due to evacuative reoxygenation. The TN and NH3-N removal rates in the system were 26.6% and 97.5%, respectively. COD decreased rapidly in the early stages and more gradually in the direction of water flow of the wetland system. Average total phosphorus (TP) removal rate was 20.71%. TN and NO3?-N levels in water of the wetland had a tendency to decline gradually with increasing operation time. Ammonia concentrations displayed only a small variation with operation time. The results also indicated that the wetland was able to maintain its temperature. The oxygen content differed during the various operating stages and exerted a marked influence on COD, TP, and TN removal. 相似文献
570.
Wang Zhaolun Yang Yuxiang Qu Xuping Zhang Jianbo Chen Yaru Nie Linxi 《Environmental Chemistry Letters》2005,3(1):33-37
We report the adsorption isotherm of methylene blue on the surface of Zhejiang and Jilin diatomite. The relationship between the adsorption isotherm and diatomite pore structure is discussed. The degree of decolouring was found to be strongly related to pH and isoelectrical value. Furnace ash residue and diatomite were found to be very effectively treating printing and dyeing wastewater. 相似文献