不同国家土壤生态筛选值比较与启示

土壤污染生态风险防控是我国土壤环境保护和管理的重要目标.与国外发达国家相比,我国尚未建立基于生态风险的土壤筛选值(土壤生态筛选值),当前有关土壤生态筛选值的综述相对较少.本文系统梳理了美国环境保护局(EPA)、英国环境署(EA)、荷兰住房、空间规划和环境部(VROM)和加拿大环境部长理事会(CCME)制定的土壤生态筛选值,从标准定位、关键受体、暴露途径、推导方法和生物有效性等方面进行对比分析.结果表明,不同国家土壤生态筛选值均考虑了土壤直接接触毒性和经生物富集和生物放大的二次毒性,推导方法普遍采用生态风险评估方法,并充分考虑污染物的生物有效性.然而,当前我国土壤风险管控标准中仅GB 15618—2018农用地标准的部分考虑了污染物对农作物生长和土壤生态的影响,且试验和推导方法与国外筛选值存在较大差异.因此,“十四五”期间建议初步构建我国土壤生态风险评估框架,明确土壤生态筛选值的定位、作用和使用形式,加强代表性物种和典型土壤的陆生生态毒理学等基础研究,建立科学、规范的土壤生态筛选值制定方法和配套指南,尝试建立适合我国土壤区域特征的土壤污染归一方程和淋洗/老化因子,为我国土壤生态筛选值的制...     

江阴长江公路大桥塔墩和锚锭的场地设计地震动工程参数

江阴长江公路大桥建成后将是主垮1385m,总长2888m 的大型悬索桥。本文在对大桥桥址区域地震地质和区域地震活动、桥址区地震构造条件及其断裂活动性综合研究的基础上,用概率方法对桥址区进行地震危险性分析;并结合桥址两岸不同的岩土条件,大桥塔墩和锚锭部位局部地形地貌、地下介质的横向非均匀性,绘出了大桥塔墩和锚锭场地不同土层的设计地震动工程参数。为大桥的抗震设计提供了可靠的科学依据。     

催化分解N_2O催化剂的研究新进展

直接催化分解N2O技术已成为当前国内外工业脱除N2O应用研究的主流和发展方向,催化剂是技术核心。综述了贵金属、金属氧化物、沸石以及其他用于分解N2O的新型固体催化剂的最新研究现状。对催化剂的研究方法、思路进行了评述,总结了现存的问题,并展望了直接催化分解N2O催化剂未来的发展方向。其中,沸石类催化剂由于高活性和结构稳定性,有望成为理想的商用催化剂。     

大尺度料斗卸料扬尘控制技术的研究与探讨

针对大尺度料斗在抓料斗、重载汽车等卸料过程中产生的扬尘问题,分别对单侧抽风式扬尘控制技术、多侧抽风式扬尘控制技术、单侧吹吸式扬尘控制技术和多侧吹吸式扬尘控制技术等扬尘控制技术的扬尘控制效果进行了探讨。另外,针对两边同时具有卸料点的大尺度料斗,在重载汽车卸料过程中产生的扬尘问题,提出了移动式扬尘控制技术对其扬尘进行控制;并结合具体实例对移动式扬尘控制技术的应用进行了介绍,同时指出了其使用过程中存在的问题。     

改进的GA-BP神经网络在矿井突水水源判别中的应用

矿井突水水源的判别是制定防治水措施的重要环节。通过对某矿含水层水化学特 性的相关性分析,将PCA算法、K折交叉验证算法嵌入GA-BP神经网络,提出了一种新的 GA-BP神经网络,将其应用于实例分析中,并与传统的方法进行比较。结果表明:针对 水化学特性相近的含水层,PCA算法能够排除样本中的冗余信息,降低样本指标维度, 简化BP神经网络结构;K折交叉验证算法能够提高GA算法对BP神经网络权值的寻优质量 ,使GA算法的进化方向更具合理性;二者的引入大大优化了传统GA-BP神经网络性能, 其判别精度更高、适用性更强、结果更可靠,在矿井突水水源判别方面具有很好的应用 前景。     

Low blood lead levels and hemoglobin concentrations in preschool children in China

It is well known that lead (Pb) produces reduced haemoglobin (Hb) levels and risk of anemia when blood lead levels (BPb) are greater than 20?µg?dL^?1. Two recent studies reported an increased risk of anemia in children with BPb between 10–20?µg?dL^?1, but few studies examined the association between Hb levels or risk of anemia and BPb under 10?µg?dL^?1. In the present study this association was examined using data of 140 preschool children from a larger prospective cohort study in China. Data showed that compared to children with BPb <5?µg?dL^?1, children with BPb between 7.5–10?µg?dL^?1 had significantly lower Hb levels, but there were no marked differences for other groups. A linear regression model showed a negative relationship between BPb and Hb levels after controlling for age, gender, height, weight, and iron (Fe) deficiency. This finding, although limited by a small sample size, suggests it may be important to examine Pb-induced hemosynthesis effect at concentrations less than 10?µg?dL^?1.     

助剂强化罐底油泥的压滤脱水性能

采用实验室压滤装置对胜利油田某联合站罐底清罐油泥进行压滤脱水研究,采用单独添加助滤剂G、絮凝剂PAM或PAC均可改善过滤效果,提高滤速,降低过滤比阻。但仅使用助滤剂G时滤速的提高尚不够理想,单独使用絮凝剂PAM或PAC时,滤饼含水率偏高,滤饼不易从滤布上剥离;絮凝剂PAM 0.1%与助滤剂G 3.0%复配,滤饼比阻由空白样的18.7×1012 m/kg降低到0.05×1012 m/kg,3 min即可使滤饼含水率降到74.16%,滤液澄清,滤饼成形性好,较仅添加絮凝剂PAM时,更容易从滤布上剥离。     

Effects of particle characteristics on flame propagation behavior during organic dust explosions in a half-closed chamber

To reveal the effects of particle characteristics on the mechanisms of flame propagation during organic dust explosions clearly, three long chain monobasic alcohols which are solids at room temperature and have similar physical–chemical properties were chosen to carry out experiments in a half-closed small chamber. A high-speed video camera was used to record the flame propagation process and to obtain the direct light emission photographs. Flame temperature was detected by a fine thermocouple. Based on the experimental results above, analysis was conducted on flame propagation characteristics and temperature profiles of organic particle cloud. As a result, it was found that the particle materials, especially volatility, strongly affected the flame propagation behavior. Particle concentration also affects the combustion zone propagation process significantly. With increasing the particle concentration, the maximum temperature of the combustion zone increases at the lower concentration, reaches a maximum value, and then decreases at the higher concentration. The propagation velocity of the combustion zone has a linear relationship with the maximum temperature, which implies conductive heat transfer is dominant in the flame propagation process of the three different volatile dusts.     

Preparation and characterization of surface modified powder of calcium hydroxide used as chlorine scavenger

In order to avoid existing shortcomings of chlorine leakage treatment, we developed a new chlorine scavenger. The main composition of the chlorine scavenger was calcium hydroxide. The chlorine scavenger was prepared by wet process with water as solvent through adding surface active agent and silicone oil, etc. The influence of surfactant on modified powder was investigated, which included the sodium dodecyl benzene sulfonate, the sodium stearate, the water-soluble silicone oil, the emulsifying silicon oil and the amino silicone oil, and the effect of modification of judgment were illustrated, which mainly involved the sifting rate, the bulk density, the contact angle, on this basis, also the author analyzed the powder of modification by using SEM analysis and size distribution, The modified powder had the following characteristics: high absorptivity, anti-caking, good air permeability and so on. The results showed that overall performance of modified powder was better than the performance of unmodified powder. The adding amount of sodium stearate was preferably 2% while the optimum amount of emulsifying silicon oil and amino silicone oil was 3%. The comprehensive performance of powder modified with compound modifiers was better than the performance of the powder modified with a single modifier. The property of powder modified with sodium stearate and amino silicone oil had a good performance analyzed from the uniformity of particle size distribution of the powder and anti-caking. The powder modified with sodium stearate and emulsifying silicon oil had a good absorption rate of chlorine.     

模糊综合评价在建筑机械管理中的应用

应用模糊综合评价方法对建筑机械管理进行定量的综合评判,以期能够定量地预警。