A Risk-Based Approach for Managing Hazardous Waste

In 1992, the U.S. Environmental Protection Agency (EPA) proposed risk-based management of hazardous waste. A major component of the proposed rule is the determination of non-site- specific screening concentration levels from waste leachate. Ground water at a downgradient exposure point must not exceed those screening levels, or more stringent requirements would apply.
The screening concentration level is determined with verified models and equations that simulate the transport and attenuation of chemicals as they travel from the source area to the exposure point. A consortium of screening levels is determined in this paper by considering varying physical, chemical, and biological conditions. In addition, a method is developed for multi component leaching from contaminated soils in a landfill to determine the time-dependent behavior of a finite source. Finally, this paper discusses infiltration rate through the clay liner.     

Merging multiple precipitation sources for flash flood forecasting

We investigated the effectiveness of combining gauge observations and satellite-derived precipitation on flood forecasting. Two data merging processes were proposed: the first one assumes that the individual precipitation measurement is non-bias, while the second process assumes that each precipitation source is biased and both weighting factor and bias parameters are to be calculated. Best weighting factors as well as the bias parameters were calculated by minimizing the error of hourly runoff prediction over Wu-Tu watershed in Taiwan. To simulate the hydrologic response from various sources of rainfall sequences, in our experiment, a recurrent neural network (RNN) model was used.

The results demonstrate that the merged method used in this study can efficiently combine the information from both rainfall sources to improve the accuracy of flood forecasting during typhoon periods. The contribution of satellite-based rainfall, being represented by the weighting factor, to the merging product, however, is highly related to the effectiveness of ground-based rainfall observation provided gauged. As the number of gauge observations in the basin is increased, the effectiveness of satellite-based observation to the merged rainfall is reduced. This is because the gauge measurements provide sufficient information for flood forecasting; as a result the improvements added on satellite-based rainfall are limited. This study provides a potential advantage for extending satellite-derived precipitation to those watersheds where gauge observations are limited.     

Local economic linkages to community‐based tourism in rural Costa Rica

This paper reports on the contribution of tourism to the wellbeing of rural residents through the development of economic linkages engaged by community‐based tourism (CBT) in rural Costa Rica. In a qualitative case study of local economic linkages surrounding one such project in Chira Island, economic linkages were assessed at two levels: discourse and practice. The findings indicate that CBT does not involve the collective property of the community, but rather, the collective property of a group of community members organized in a formal association. As a result, a discourse on local economic linkages has been promoted by CBT support organizations in which hopes of wider benefits are placed on small linkages to services and products provided by local community members. However, a field survey suggested that the economic linkages generated by CBT in the community were sporadic and polyvalent and, furthermore, that the linkages with agriculture are negatively affected by scale and seasonality, resulting in leakages out of the community. These findings caution practitioners that CBT may only have small‐scale positive impacts on the local economy.     

Analysing the Relationship Between Typhoon‐Triggered Landslides and Critical Rainfall Conditions

Many landslides are triggered by rainfall. Previous studies of the relationship between landslides and rainfall have concentrated on deriving minimum rainfall thresholds that are likely to trigger landslides. Though useful, these minimum thresholds derived from a log–log plot do not offer any measure of confidence in a landslide monitoring or warning system. This study presents a new and innovative method for incorporating rainfall into landslide modelling and prediction. The method involves three steps: compiling radar reflectivity data in a QPESUMS (quantitative precipitation estimation and segregation using multiple sensors) system during a typhoon (tropical hurricane) event, estimating rainfall from radar data and using rainfall intensity and rainfall duration as explanatory variables to develop a landslide logit model. Given the logit model, this paper discusses ways in which the model can be used for computing probabilities of landslide occurrence for a real‐time monitoring system or a warning system, and for delineating and mapping landslides. Copyright © 2007 John Wiley & Sons, Ltd.     

Distribution of erosion across bedrock channels

Lateral erosion in bedrock rivers is an important control on the shape of channel cross‐sections, and the coupling of channels and hillslopes. Recent observations link lateral erosion to the variability of flow. We propose two mechanisms to explain this. One is based on changing shear stress distributions within the channel with varying flood level, the other on the competition between cover and tool effects in fluvial bedrock erosion. We assess these processes for the Liwu River, Taiwan, and conclude that cover and tool effects dominate the partitioning of lateral and vertical erosion in this case. Copyright © 2007 John Wiley & Sons, Ltd.     

Particulate carbohydrates and uronic acids in the northern East China Sea

Carbohydrate species, such as uronic acids, play an important role in oceanic carbon cycling, coagulation and adsorption processes. Concentrations of particulate carbohydrates (PCHO) and uronic acids (PURA) were measured in the northern East China Sea (ECS) during June and November, 2006. In June, maximum concentrations of PCHO and PURA were observed in the surface layer of coastal waters. Their concentrations rapidly decreased with depth, suggesting that they are both bio-reactive. Moreover, phytoplankton abundance and bacterial biomass seem to be associated with observed PCHO and PURA concentrations in the ECS during June, suggesting that production of carbohydrate species in the ECS is regulated by phytoplankton assemblages, bacterial assimilation or degradation. In November, however, PCHO and PURA concentrations were homogenous within the water column due to strong vertical mixing. No strong correlations were observed between carbohydrate species (PCHO and PURA) and phytoplankton or bacterial biomass, suggesting that production of these compounds in November might be caused by the physiological difference between nutrient limited and non-nutrient limited phytoplankton. Furthermore, strong negative correlations between nutrients and PCHO species suggest that nutrient levels may be one of the driving forces behind the production of these compounds in the ECS.     

Microbial dynamics in an oligotrophic bay of the western subtropical Pacific: Impact of short-term heavy freshwater runoff and upwelling

This two-year study investigates the possible factors that determine spatial and temporal dynamics of picoplankton (heterotrophic bacteria, autotrophic picoplankton—Synechococcus spp., Prochlorococcus, and picoeukaryotes) and nanoflagellate abundance in the subtropical Ilan Bay, Taiwan, where the inner bay is affected by freshwater run-off from the Lanyang River and the eastern outer bay by the Kuroshio Current. In the inner bay, there was more rain and freshwater discharge in 2005 than in 2004 during the warm season (>24° C, June–September). The abundance of bacteria, Synechococcus spp., Prochlorococcus, and picoeukaryotes and the percentage contributions of pigmented nanoflagellate (PNF %) were two- to eight-fold greater during this period (July in 2005) than for other sampling periods. Relatively low abundance of heterotrophic nanoflagellates (HNF) in the presence of abundant picoplankton prey suggests that top-down control determined HNF abundance in the Ilan Bay, Taiwan.     

Morphological Studies on the Infraciliature of a Planktonic Ciliate, Tintinnopsis brasiliensis （ Ciliophora ： Tintinina）

A poorly-described marine planktonic ciliate, Tintinnopsis brasiliensis Kofoid ＆ Campbell, 1929, collected from the Taiping Cape of Qingdao, China, was morphologically investigated based on permanent preparation after protargol impregnation and was compared with other related congeners. According to the infraciliature, three ciliary groups can be recognized, which reveals a very stable structure among specimens and denotes that the pattern of infraciliature is, apart from the features of the lorica, a highly reliable criterion for species identification.