树冠火对输油站热辐射影响的数值模拟研究

树冠火是森林火灾的一种,在森林的树冠层燃烧和蔓延,主要由地表火在强风作用下引起.树冠火很少发生,约占森林火灾的5％,但其燃烧温度高、热释放速率大、蔓延速度快,对周围物体的破坏性极大.处在森林地区的输油站面临着树冠火带来的潜在风险.火灾产生的热辐射极有可能导致输油站内人员伤亡,设备遭到破坏.通过确定树冠火热释放速率、火灾发生位置及环境参数来设计火灾场景,采用火灾动力学场模拟软件FDS,模拟分析树冠火对输油站的热辐射影响.结果表明,由于无法采用地面扑救,防火隔离带是应对树冠火威胁的有效措施;当防火隔离带达到一定间距时,有风条件下与无风条件相比目标物体不会接收到更多的热辐射;防火隔离带设置为坡面形式,可以增加其表面积,从而吸收更多的热辐射.     

化学品急性毒性藻红外测试技术的方法改进研究

在以往藻红外测试技术的急性毒性测试中,每次每个测试杯测试1个藻温,共2个测试组,并用藻最大响应温差1个指标进行毒性评价,测试结果的可行性和稳定性不理想,针对这个问题提出了改进方法:1)每次每个测试杯连测3个藻温;2)改为3个测试组;3)将单指标法改为三指标法;4)增加测试结果的重现性分析。通过蒸馏水毒性测试实验和重金属毒性测试实验,分析改进方法的效果。结果显示,不同指标方法中,三指标法控制假结果出现率为20%,控制效果最好;在测试4元重金属共存(总浓度0.066~0.156 mg·L~(-1))的毒性时,测试3个藻温的所有指标法的平均重现率(%)/重现性(%)均为100%/100%,测试1个藻温的三指标法的平均重现率(%)/重现性(%)为67%/100%,表明测试高浓度的重金属毒性时,不同指标法都有很好的评价效果;在测试一元重金属(0.001~0.1 mg·L~(-1))毒性时,只有三指标法的平均重现率(%)/重现性(%)是100%/100%,远高于其他指标法,表明只有三指标法才可准确测试低浓度重金属的毒性。在测试5种不同重金属共存的毒性时,三指标法的平均重现率(%)/重现性(%)平均为86.8%/100%。研究表明,改进后的技术用于化学品急性毒性测试,灵敏度高和稳定性好,结果可靠。     

Concentrations of uranium in drinking water and cumulative,age-dependent radiation doses in four districts of Uttar Pradesh,India

The present work deals with the determination of uranium concentrations in drinking and ground water samples by laser fluorimetry and calculation of cumulative, age-dependent radiation doses to humans. The concentrations were found to be between 0.20 ± 0.03 and 64.0 ± 3.6 μg L^?1, with an average of 11.1 ± 1.5 μg L^?1, well within the drinking water limit of regulatory bodies. The concentrations of uranium increase with depth of water samples collection. The estimated annual ingestion dose due to the intake of uranium through drinking water for all age groups varied between 0.2 and 137 μSv a^?1, with an average of 17.3 μSv a^?1. The mean annual ingestion dose is 5% of the global average ingestion dose, for infants, marginally higher than for other age group. Most effective dose values were less than 20 μSv a^?1.     

现代生活要认识和防范电磁辐射——以一些新信息为例

社会在发展,生活水平和人们的追求也在不断地提高,绿色发展、和谐发展与科学发展,人的健康与提升生活品质都是第一要素.人们身边的电磁辐射内容是“百花齐放”,电磁辐射环境“丰富多彩”;电磁辐射无声地时刻伴随着人们.研究显示,过量、过度地电磁辐射会负影响人们的器官、肌体等.现代生活、工作中光生物安全是一很现实的问题,提升健康水平与生活幸福度,大家当增大对光安全的认知度,并增加、丰富电磁辐射及其防范之常识.参13.     

基于同步辐射的硬X射线荧光技术分析污染土壤中重金属分布

基于同步辐射技术的微束X射线荧光(μ-XRF)分析具备原位分析样品的元素组分,化学特性,物质结构及其二维分布等的能力,可更加直观地揭示目标元素在复杂体系中的分布状态.利用传统的化学消解与原位μ-XRF技术相结合的方法,探测锡矿山土壤中多种元素的含量和空间分布,采用线性回归方法分析各元素的相关性.结果表明,供试土壤Sb和As含量较高,分别为6 681和878 mg·kg-1,μ-XRF分析表明土壤中Fe、Mn分别与As的空间分布相关性较好,决定系数(R2)分别达0.225 8和0.181 1,更直观地揭示了As在土壤中以铁锰结合态为主.μ-XRF技术的应用原位直观地揭示了土壤中多种元素的分布关系,为综合评价和预测土壤中重金属的环境行为以及发展污染土壤修复技术等提供理论支持.     

Effects of UV-B radiation on the gills of Catla catla during early development

Scanning electron microscopic (SEM) study of gills of Catla catla catla (17-day-old) exposed to UV-B radiation (145?µW?cm^?2 at the water surface) for three different exposure times: 5, 10 and 15?min was conducted. Fish without UV-B exposure served as control. UV-B radiation damaged both gill filaments and lamellae. The intensity of damage was minimal in 5?min exposed fish, followed by 10?min exposed fish and maximal in 15?min. The gill epithelium was severely damaged in 15?min irradiated fish compared to control. Pavement cells (PVCs) were damaged and the numbers of microridges within PVCs decreased. The deep boundary of PVC was not clear. In some area of gill epithelium, PVCs were destroyed and mitochondrion-rich cells (MRCs) were exposed. The 5?min exposure reduced the number of microridges in the PVCs, but the boundary of PVCs was still visible. MRCs in the gill epithelium were not exposed in 5?min exposed fish. The damage to PVCs and subsequent exposure of MRCs in UV-B irradiated fish may hamper respiratory functions and disturb osmoregulation in catla.     

The role of the cloud optical thickness in the attenuation of the solar ultraviolet radiation reaching the ground: Implications to the human health impacts

Cloud optical depth, as it is derived from the King's method, is compared with that deduced from the simple two stream approximation for the greater Athens, Greece area. The results show that King's method overestimates the cloud optical thickness, in comparison to the two stream approximation. These estimations were also compared with satellite observations provided by the International Satellite Cloud Climatology Project. This comparison showed that there are large deviations between ground‐based and satellite observations. These deviations are probably due to the uncertainty introduced by the integration procedure of the satellite spatial analyzing resolution (distinctness). Furthermore, values of the simple scattering albedo were calculated by employing a recently proposed theoretical method and using the solar ultraviolet irradiance measurements performed at the Athens University on a routine basis. These results are of great importance for the densely populated areas like Athens, in a sense of health impacts, from enhanced incident solar ultraviolet radiation.     

O3和UV-B共同作用对大豆干物质和产量的影响

为揭示O₃和UV-B共同作用对大豆干物质和产量的影响,以大豆“八月黄”为供试材料,利用OTC(开顶式气室)和紫外灯模拟O₃和UV-B共同作用环境,研究大豆干物质和产量的变化. 结果表明:与对照组相比,T1(UV-B辐射增强10%左右)、T2(100nL/L O₃与增强10%左右的UV-B复合)和T3(150nL/L O₃与增强10%左右的UV-B复合)处理下,成熟期大豆株高分别降低了12.73%、12.78%和14.15%;w〔Chl(a+b)〕分别减少了-1.16%(P>0.05)、34.20%(P<0.05)和57.38%(P<0.05);净光合速率(P_n)分别下降了11.50%、46.65%和48.58%;单株干物质质量显著降低(P<0.05),分别减少了31.02%、61.35%和67.53%;大豆产量分别减少了4.13%、54.09%和79.34%. O₃和UV-B对大豆的生长和干物质累积均有不利影响,并且存在一定的协同影响,2个因子共同作用对大豆生长和干物质累积更为不利;O₃和UV-B共同作用下大豆产量的降低主要是由粒数和粒质量降低所致.      

UV-B辐射下悬沙对小球藻生长和DNA损伤的影响

研究了UV-B辐射(17μW cm-2,5 min/d)下不同浓度(0、100和1 000 mg L-1)和粒径组成(全粒径组和粒径<38μm组)的悬沙对小球藻(Chlorella sp.)生长和DNA损伤的影响.结果显示,小球藻的生长可用Logistic增长模型拟合,拟合后的生长参数表明悬沙的"遮荫效应"减轻了UV-B辐射对小球藻细胞的DNA损伤,从而对小球藻生长产生正影响.悬沙浓度越高,UV-B辐射对小球藻细胞DNA损伤程度越低,小球藻的环境负载能力a和瞬时增长率K越大.当悬沙浓度为100 mg L-1时,全粒径组a值和K值小于粒径<38μm组,且两组间小球藻细胞DNA损伤差异显著(P<0.05),但当悬沙浓度达1 000 mg L-1时,全粒径组a值和K值大于粒径<38μm组,两组间细胞的DNA损伤无显著差异(P>0.05).图3表2参24     

沙尘天气对北京大气环境质量及太阳辐射的影响

利用空气污染指数(API)、地面气象数据和辐射观测数据,分析了2009年3月一次典型沙尘天气发生时的大气环境质量及太阳辐射变化,并分析了2008年10月—2009年6月不同污染情形下各太阳辐射要素之间的关系. 结果表明:API与辐射关系明显,沙尘天气导致总辐射、直接辐射和反射辐射减小.净辐射白天减小而夜间增大. 能见度和气压等气象要素对沙尘过程影响明显. 沙尘到来时,能见度降低,地面处于低气压控制下;沙尘过境后地面被高压控制. 随着污染的加重,总辐射与反射辐射相关关系显著,变化不大但略有偏差;直接辐射和总辐射、散射辐射、反射辐射的相关性先降低后增加;散射辐射与总辐射的比值持续增大,但增加的速度随着污染的加重趋于平缓,且离散度增大.