Importance of monsoon rainfall in mass fluxes of filtered and unfiltered mercury in Gwangyang Bay, Korea

We investigated the effects of the East Asian Summer Monsoon (EASM), which brings approximately half of Korea's annual rainfall in July, on the concentration and particle-water partitioning, and sources of Hg in coastal waters. Surface seawater samples were collected from eight sites in Gwangyang Bay, Korea, during the monsoon (July, 2009) and non-monsoon dry (April and November, 2009) seasons and the concentrations of suspended particulate matter, chlorophyll-a, and unfiltered and filtered Hg were determined. We found significant (p < 0.05) increases in filtered Hg in the monsoon season (1.8 ± 0.019 pM) compared to the dry season (0.62 ± 0.047 pM). In contrast, the Hg concentrations associated with particles showed no significant differences (p > 0.05) between the monsoon (459 ± 141 pmol g^− 1) and the dry season (346 ± 30 pmol g^− 1), which resulted in decreased particle-water partition coefficients of Hg in the monsoon season compared to the values in the dry season: 5.7 ± 0.1 in April, 5.3 ± 0.1 in July, and 5.8 ± 0.1 in November. The annual Hg input to Gwangyang Bay was estimated at 64 ± 6.6 mol yr^− 1 and 27 ± 1.9 mol yr^− 1 for unfiltered and filtered Hg, respectively. The Hg discharged from rivers was a major source of Hg in Gwangyang Bay: the river input contributed 83 ± 13% of total input of unfiltered and 73 ± 6.0% of filtered Hg. On a monthly basis, unfiltered Hg input was 17 ± 11 mol month^− 1 in the monsoon season and 3.2 ± 0.70 mol month^− 1 in the dry season, while filtered Hg input was 7.1 ± 4.1 mol month^− 1 in the monsoon and 1.3 ± 0.26 mol month^− 1 in the dry. Consequently, the EASM resulted in an unfiltered Hg input 5.3 times greater than the mean dry month input and a filtered Hg input 5.5 times greater than the mean dry month input, which is mainly attributable to enhanced river water discharge during the monsoon season.     

Monitoring of Cryptosporidium and Giardia river contamination in Paris area

This study evaluates the protozoan contamination of river waters, which are used for drinking water in Paris and its surrounding area (about 615,000 m(3) per day in total, including 300,000 m(3) for Paris area). Twenty litre samples of Seine and Marne Rivers were collected over 30 months and analyzed for Cryptosporidium oocysts and Giardia cysts detection according to standard national or international methods. Cryptosporidium oocysts and Giardia cysts were found, respectively, in 45.7% and 93.8% of a total of 162 river samples, with occasional high concentration peaks. A significant seasonal pattern was observed, with positive samples for Cryptosporidium more frequent in autumn than spring, summer and winter, and positive samples for Giardia less frequent in summer. Counts of enterococci and rainfalls were significantly associated with Giardia concentration but not Cryptosporidium. Other faecal bacteria were not correlated with monitored protozoan. Marne seems to contribute mainly to the parasitic contamination observed in Seine. Based on seasonal pattern and rainfall correlation, we hypothesize that the origin of contamination is agricultural practices and possible dysfunction of sewage treatment plants during periods of heavy rainfalls. High concentrations of protozoa found at the entry of drinking water plants justify the use of efficient water treatment methods. Treatment performances must be regularly monitored to ensure efficient disinfection according to the French regulations.     

Effects of urban grass coverage on rainfall-induced runoff in Xi'an loess region in China

In this study, laboratory rainfall simulation experiments were conducted to investigate the regulatory effects of grass coverage on rainfall-runoff processes. A total of 80 grass blocks planted with well-grown manilagrass, together with their root systems, were sampled from an eastern suburban area of Xi'an City in the northwest arid area of China and sent to a laboratory for rainfall simulation experiments. The runoff and infiltration processes of a slope with different grass coverage ratios and vegetation patterns were analyzed. The results show that the runoff coefficient decreases with the increase of the grass coverage ratio, and the influence of grass coverage on the reduction of runoff shows a high degree of spatial variation. At a constant grass coverage ratio, as the area of grass coverage moves downward, the runoff coefficient, total runoff, and flood peak discharge gradually decrease, and the flood peak occurs later. With the increase of the grass coverage ratio, the flood peak discharge gradually decreases, and the flood peak occurs later as well. In conclusion, a high grass coverage ratio with the area of grass coverage located at the lower part of the slope will lead to satisfactory regulatory effects on rainfall-induced runoff.     

自动气象站雨量传感器现场校准新方法

本文主要介绍了在自动站雨量传感器现场校准时,大胆尝试采用由医用注射针头来调节雨量的流量,并通过试验证明效果良好.     

Modeling of Rainfall-Induced Shallow Landslides of the Flow-Type

The paper deals with the modeling of failure and postfailure stage of shallow landslides of the flow-type that often affect natural shallow deposits of colluvial, weathered, and pyroclastic origin. The failure stage is frequently associated to rainfall that directly infiltrates the slope surface and to spring from the underlying bedrock. The postfailure stage is characterized by the sudden acceleration of the failed mass. The geomechanical modeling of both stages, based on site conditions and soil mechanical behavior, represents a fundamental issue to properly assess the failure conditions and recognize the potential for long travel distances of the failed soil masses. To this aim, in this paper, the current literature on the failure and postfailure stages of the shallow landslides of the flow-type is first reviewed. Then, an approach for their geomechanical modeling is proposed and three different modeling alternatives are presented. These models are then used to analyze, at different scales, a relevant case study of Southern Italy (Sarno-Quindici event, May 4–5, 1998). Numerical analyses outline that both site conditions and hydraulic boundary conditions are among the key factors to evaluate the reliability of landslides of the flow-type. The potentialities and limitations of the available models are also evidenced as well as the perspectives related to the use of more advanced numerical models.     

Short-Duration Rainfall Intensity Equations for Urban Drainage Design

A practical method for developing rainfall-intensity equations for short durations (approximately one hour or less) for locations in the United States covered by NOAA Atlas 14 Volumes 1, 2, 3, and 4 is presented. For the semiarid western United States covered by Volume 1, for Puerto Rico and the U.S. Virgin Islands covered by Volume 3, and for Hawaii covered by Volume 4, single formulas apply to rainfall of all average recurrence intervals (ARIs). For the central and mid-Atlantic regions of the United States covered by Volume 2, formula coefficients are provided for several ARIs ranging from 1.58 to 1,000 years. All equations are based on a single-term exponential expression plus a constant that provides excellent fits to the available data. Mathematical expressions for the central and mid-Atlantic region coefficients as functions of the ARI are provided to simplify application of the approach. Mathematical relations representing design storm hyetographs are developed using the intensity-duration expression by distributing rainfall about the time of peak intensity proportioned by a factor r = tp/td, where tp = time to peak rainfall intensity, and td = storm duration.     

摆喷式人工降雨机的特性试验

在试验率定的基础上，对摆喷式人工模拟降雨的试验特性进行了研究。该机的原始技术结构取自于奥地利维也纳农业大学，原装置仅适于平缓农地，经改装后可用于陡坡坡面流及坡面侵蚀研究。经率定，该机在一定的雨强范围内均匀度可达８０％以上，且模拟降雨试验表明，其径流泥沙过程与作者导出的坡面流及侵蚀的理论模型是吻合的。该机喷嘴喷出的水股具有一定的初速。利用力学原理，还得出了在有初速条件下雨滴在有限高度下降的终点速度公     

人工模拟降雨装置的研制与应用

本文介绍为现场核素迁移试验而研制的人工模拟降雨装置,着重了设计参数和选择和性能测试的方法及其结果。该装置采用医用注射针头在一圆圈内振动洒落水滴模拟降雨。     

Engineering geology assessment of El-Rabweh landslide, south-east of Amman City, Jordan

The paper focuses on the geological and geotechnical characteristics of the area of the El-Rabweh landslide, south-east of Amman City. From the topography, geology and climate of the area, it is apparent that the landslide has taken place mainly due to the presence of a quarry, the actual slide occurring during the abnormally wet winter of 1991/1992. The stability of the landslide area has been assessed using limit equilibrium analysis and stereonets. The shear strength parameters were both determined by direct shear measurements and calculated from the RMR and Q values obtained using extensive field data. Electronic Publication     

Mathematical interpretation of pollutant wash-off from urban road surfaces using simulated rainfall

In the context of stormwater quality modelling, an in-depth understanding of underlying physical processes and the availability of reliable and accurate mathematical equations, which can replicate pollutant processes are essential. Stormwater pollutants undergo three primary processes, namely, build-up, wash-off and transport, before accumulating into receiving waters. These processes are expressed mathematically by equations in stormwater quality models. Among the three processes, wash-off is the least investigated. This paper presents the outcomes of an in-depth investigation of pollutant wash-off processes on typical urban road surfaces. The study results showed that a storm event has the capacity to wash-off only a fraction of pollutants available and this fraction varies primarily with rainfall intensity, kinetic energy of rainfall and characteristics of the pollutants. These outcomes suggest that the exponential equation commonly used for mathematically defining pollutant wash-off would need to be modified in order to incorporate the wash-off capacity of rainfall. Consequently, the introduction of an additional term referred to as the 'capacity factor'C(F) is recommended. C(F) primarily varies with rainfall intensity. However, for simplicity three rainfall intensity ranges were identified where the variation of C(F) can be defined. For rainfall intensities less than 40mm/h, C(F) varies linearly from 0 to 0.5. For rainfall intensities from 40 to around 90mm/h, C(F) is a constant around 0.5. Beyond 90mm/h, C(F) varies between 0.5 and 1.