冷却塔的噪声特性与控制

某住宅小区建有大型冷却塔,运行时产生的噪声严重干扰了居民的生活。在现场进行噪声测量的基础上,着重分析了冷却塔的噪声特性以及噪声源,进而设计并详细分析了针对不同噪声源的噪声治理方案。实施结果证明,采取的控制措施有效,降噪效果明显,能完全满足国家技术标准的要求。     

Atmospheric oxidation capacity in the summer of Houston 2006: Comparison with summer measurements in other metropolitan studies

Both similarities and differences in summertime atmospheric photochemical oxidation appear in the comparison of four field studies: TEXAQS2000 (Houston, 2000), NYC2001 (New York City, 2001), MCMA2003 (Mexico City, 2003), and TRAMP2006 (Houston, 2006). The compared photochemical indicators are OH and HO₂ abundances, OH reactivity (the inverse of the OH lifetime), HO_x budget, OH chain length (ratio of OH cycling to OH loss), calculated ozone production, and ozone sensitivity. In terms of photochemical activity, Houston is much more like Mexico City than New York City. These relationships result from the ratio of volatile organic compounds (VOCs) to nitrogen oxides (NO_x), which are comparable in Houston and Mexico City, but much lower in New York City. Compared to New York City, Houston and Mexico City also have higher levels of OH and HO₂, longer OH chain lengths, a smaller contribution of reactions with NO_x to the OH reactivity, and NO_x-sensitivity for ozone production during the day. In all four studies, the photolysis of nitrous acid (HONO) and formaldehyde (HCHO) are significant, if not dominant, HO_x sources. A problematic result in all four studies is the greater OH production than OH loss during morning rush hour, even though OH production and loss are expected to always be in balance because of the short OH lifetime. The cause of this discrepancy is not understood, but may be related to the under-predicted HO₂ in high NO_x conditions, which could have implications for ozone production. Three photochemical indicators show particularly high photochemical activity in Houston during the TRAMP2006 study: the long portion of the day for which ozone production was NO_x-sensitive, the calculated ozone production rate that was second only to Mexico City's, and the OH chain length that was twice that of any other location. These results on photochemical activity provide additional support for regulatory actions to reduce reactive VOCs in Houston in order to reduce ozone and other pollutants.     

Effects of sandy desertified land rehabilitation on soil carbon sequestration and aggregation in an arid region in China

The rehabilitation of sandy desertified land in semi-arid and arid regions has a great potential to increase carbon sequestration and improve soil quality. Our objective was to investigate the changes in the soil carbon pool and soil properties of surface soil (0–15 cm) under different types of rehabilitation management. Our study was done in the short-term (7 years) and long-term (32 years) desertification control sites in a marginal oasis of northwest China. The different management treatments were: (1) untreated shifting sand land as control; (2) sand-fixing shrubs with straw checkerboards; (3) poplar (Populus gansuensis) shelter forest; and (4) irrigated cropland after leveling sand dune. The results showed that the rehabilitation of severe sandy desertified land resulted in significant increases in soil organic C (SOC), inorganic C, and total N concentrations, as well as enhanced soil aggregation. Over a 7-year period of revegetation and cultivation, SOC concentration in the recovered shrub land, forest land and irrigated cropland increased by 4.1, 14.6 and 11.9 times compared to the control site (shifting sand land), and increased by 11.2, 17.0 and 23.0 times over the 32-year recovery period. Total N, labile C (KMnO₄–oxidation C), C management index (CMI) and inorganic C (CaCO₃–C) showed a similar increasing trend as SOC. The increased soil C and N was positively related to the accumulation of fine particle fractions. The accumulation of silt and clay, soil C and CaCO₃ enhanced the formation of aggregates, which was beneficial to mitigate wind erosion. The percentage of >0.25 mm dry aggregates increased from 18.0% in the control site to 20.0–87.2% in the recovery sites, and the mean weight diameter (MWD) of water-stable aggregates significantly increased, with a range of 0.09–0.30 mm at the recovery sites. Long-term irrigation and fertilization led to a greater soil C and N accumulation in cropland than in shrub and forest lands. The amount of soil C sequestration reached up to 1.8–9.4 and 7.5–17.3 Mg ha^?1 at the 0–15 cm layer over a 7- and 32-year rehabilitation period compared to the control site, suggesting that desertification control has a great potential for sequestering soil C and improving soil quality in northwest China.     

What adverse health effects will environmental heavy metal co-exposure bring us: based on a biological monitoring study of sanitation workers

Environmental Science and Pollution Research - To investigate the relationship between health effect profile and co-exposure to heavy metal, 254 sanitation workers from Guangzhou, China, were...     

Study on mechanics of crowd jam based on the cusp-catastrophe model

Some characteristics of crowd jam like the phenomena of discontinuous jumping in reality are hard to be explained by the equations governing pedestrians. The catastrophe theory can explain these characteristics. A cusp-catastrophe model is developed to analyze the mechanics of crowd jam by drawing graphs for a cusp-catastrophe model of crowd, the bifurcation set and the projection of catastrophe model. Meanwhile, the critical density and the critical velocity are derived. It is concluded that the cusp model is a more efficient predictor than the linear model or the equations governing pedestrians and is reasonably realistic for dense crowd flow scenarios.     

溴氰菊酯对菲律宾蛤仔体内酶活性和组织损伤的初步探索

采用不同质量浓度的溴氰菊酯(0.0070 mg·L~(-1)、0.014 mg·L~(-1)、0.020 mg·L~(-1)、0.027 mg·L~(-1))对菲律宾蛤仔进行20 d半静置染毒,测定不同时间淋巴液中乙酰胆碱酯酶(ACh E)和钠离子-钾离子-三磷酸腺苷酶(Na~+-K~+-ATPase)活性、鳃和肝脏中谷胱甘肽转硫酶(GST)活性的变化,并观察染毒20 d后鳃丝组织和消化盲囊组织的损伤情况。酶活性分析结果显示,与对照组相比,低浓度组(0.0070 mg·L~(-1))试验期间酶活性均无显著差异(P0.05);中浓度组(0.014 mg·L~(-1)、0.020 mg·L~(-1))淋巴液中ACh E和Na~+-K~+-ATPase均呈先激活后抑制的变化规律(P0.05),鳃和肝脏中GST活性均呈上升趋势(P0.05);高浓度组(0.027mg·L~(-1))淋巴液中ACh E和Na~+-K~+-ATPase、肝脏中GST活性在试验期间持续下降(P0.01),而鳃中GST活性呈先抑制后升高的趋势(P0.05)。研究表明,低中浓度的溴氰菊酯对菲律宾蛤仔体内的酶活性表现为先诱导后抑制,具有明显的时间、剂量效应;高浓度的溴氰菊酯对菲律宾蛤仔体内酶活持续抑制,且染毒浓度越高,组织细胞变异越显著,表现为鳃丝上皮细胞纤毛层萎缩、纤毛脱落,消化盲囊上皮细胞膨胀,出现包涵体样结构。     

某兽药厂废气治理改造工程实例

结合江苏常州某兽药厂废气污染的监测和改造经验,总结了兽药厂废气污染特点,并采用低温等离子体、碱液吸收和植物除臭剂等综合治理技术有效控制了废气污染。低温等离子体净化设备采用2组串联式布置,反应器内设计风速≤1 m/s,反应时间≥4 s。植物除臭净化设备利用原有活性炭吸附塔改造,改造成本较低。改造设备总投资约60万元,废气处理系统运行费用约788元/d。相关监测数据表明上述工艺在设备正常运行时可确保污染物达标排放。     

Removal of tetracycline from aqueous solution by a Fe3O4 incorporated PAN electrospun nanofiber mat

Pollution of antibiotics, a type of emerging contaminant, has become an issue of concern, due to their overuse in human and veterinary application, persistence in environment and great potential risk to human and animal health even at trace level. In this work, a novel adsorbent, Fe₃O₄ incorporated polyacrylonitrile nanofiber mat (Fe-NFM), was successfully fabricated via electrospinning and solvothermal method, targeting to remove tetracycline (TC), a typical class of antibiotics, from aqueous solution. Field emission scanning electron microscopy and X-ray diffraction spectroscopy were used to characterize the surface morphology and crystal structure of the Fe-NFM, and demonstrated that Fe-NFM was composed of continuous, randomly distributed uniform nanofibers with surface coating of Fe₃O₄ nanoparticles. A series of adsorption experiments were carried out to evaluate the removal efficiency of TC by the Fe-NFM. The pseudo-second-order kinetics model fitted better with the experimental data. The highest adsorption capacity was observed at initial solution pH 4 while relative high adsorption performance was obtained from initial solution pH 4 to 10. The adsorption of TC on Fe-NFM was a combination effect of both electrostatic interaction and complexation between TC and Fe-NFM. Freundlich isotherm model could better describe the adsorption isotherm. The maximum adsorption capacity calculated from Langmuir isotherm model was 315.31 mg/g. Compared to conventional nanoparticle adsorbents which have difficulties in downstream separation, the novel nanofiber mat can be simply installed as a modular compartment and easily separated from the aqueous medium, promising its huge potential in drinking and wastewater treatment for micro-pollutant removal.     

固城湖水环境污染状况与来源分析

对2001~2011年固城湖水环境污染状况评价与时空变化特征分析的基础上,探讨了固城湖的特征污染物及污染来源。结果表明,固城湖水质污染的主要超标因子为TN和TP;总体水质呈现先恶化再改善的趋势,污染由拦河网水域向小湖区水域扩散;固城湖湖体水质基本上劣于水环境功能区划要求;固城湖特征污染物为COD+M n、NH4-N、TN、TP、BOD 5;富营养化程度不断加重,之后又有所改善;氮磷污染的主要来源是水产养殖污染。     

广西钦州湾营养状况季节分析与评价研究

根据2009年1月、4月、8月和11月对钦州湾海域调查结果,分析并评价了该海域营养状况的季节变化。结果表明,钦州湾海域总溶解无机氮(DIN)含量范围在0.023 mg/L~1.750 mg/L,硅酸盐(SiO3-Si)含量范围在0.027 mg/L~3.900 mg/L,磷酸盐(PO4-P)含量范围在0.001 mg/L~0.158 mg/L。NO3-N是DIN的主要存在形式,占62%~78%。不同的营养盐季节分布有所差异。DIN季节分布表现为夏季春季秋季冬季;PO4-P季节分布为春季秋季冬季夏季;SiO3-Si季节变化为夏季秋季春季冬季。从营养结构看,与Justic'等提出的营养盐化学计量限制标准比较符合P限制条件,PO4-P可能成为浮游植物生长的潜在限制因子。按照营养状态指数值,钦州湾海域春季、夏季和秋季表层海水处于富营养化状态,钦州湾内湾富营养化程度高,一旦水文气象条件适宜,从春季到秋季该区域随时都会发生赤潮灾害的可能。