Perspectives on small watershed management in China: the case of Biliu

River basin management in China has focused on large rivers, such as the Yangtze and Yellow Rivers. However, there are also about 20,000 small river basins that deserve attention. The Biliu River basin in Liaoning Province, northeast China, which is 156 km in length, has many features common to small river basins, including divided jurisdiction among governments leading to vertical and horizontal fragmentation. In the Biliu basin, the key municipalities are Dalian with a population of almost 6 million people and Yingkou with about 2.28 million people. Each has different interests and needs, making coordination and collaboration difficult. The literature and practice suggest that effective integrated water resource management (IWRM) requires at least six features: (1) vision, policy and strategy; (2) a legislative or statutory basis to provide credibility and authority; (3) a river basin organization to coordinate development and management; (4) specification of functions and authority of the river basin organization; (5) public participation and community involvement; and (6) an IRWM strategy and plan. Water management in the Biliu River basin is assessed relative to these features of IWRM, with recommendations offered regarding changes to have water management in the Biliu River basin to reflect what is expected in an IWRM approach.     

Influence of planform geometry and momentum ratio on thermal mixing at a stream confluence with a concordant bed

The effects of planform geometry and momentum flux ratio on thermal mixing at a stream confluence with concordant bed morphology are investigated based on numerical simulations that can capture the dynamics of large-scale turbulence. In two simulations, the bathymetry and asymmetrical planform geometry are obtained from field experiments and the momentum flux ratio is set at values of one and four. These two conditions provide the basis for studying differences in thermal mixing processes at this confluence when the wake mode and the Kelvin–Helmholtz mode dominate the development of coherent structures within the mixing interface (MI). The effects of channel curvature and angle between the two incoming streams on thermal mixing processes are investigated based on simulations conducted with modified planform geometries. Two additional simulations are conducted for the case where the upstream channels are parallel but not aligned with the downstream channel and for the zero-curvature case where the upstream channels are parallel and aligned with the downstream channel. The simulations highlight the influence of large-scale coherent structures within the MI and of streamwise-oriented vortical (SOV) cells on thermal mixing processes within the confluence hydrodynamics zone. Simulation results demonstrate the critical role played by the SOV cells in promoting large-scale thermal mixing for cases when such cells form in the immediate vicinity of the MI and in modifying the shape of the thermal MI within cross sections of the downstream channel—predictions consistent with empirical measurements of thermal mixing at the confluence. The set of numerical simulations reveal that the degree of thermal mixing occurring within the confluence hydrodynamic zone varies dramatically with planform geometry and incoming flow conditions. In some cases thermal mixing at the downstream end of the confluence hydrodynamic zone is limited to the MI and its immediate vicinity, whereas in others substantial thermal mixing has occurred over most of the cross-sectional area of the flow. Overall, the simulations highlight the flow conditions and the controls of these conditions that influence mixing within the immediate vicinity of a confluence.     

Coupled aerobic and anoxic biodegradation for quinoline and nitrogen removals

Quinoline (C₉H₇N) commonly occurs in wastewaters from the chemical, pharmaceutical, and dyeing industries. As quinoline is biodegraded, nitrogen is released as ammonium. Total-N removal requires that the ammonium-N be nitrified and then denitrified. The objective of this study was to couple quinoline biodegradation with total-N removal. In a proof-of-concept step, activated sludge was sequenced from aerobic to anoxic stages. The ammonium nitrogen released from quinoline biodegradation in the aerobic stage was nitrified to nitrate in parallel. Anoxic biodegradation of the aerobic effluent then brought about nitrogen and COD removals through denitrification. Then, simultaneous quinoline biodegradation and total-N removal were demonstrated in a novel airlift internal loop biofilm reactor (AILBR) having aerobic and anoxic zones. Experimental results showed that the AILBR could achieve complete removal of quinoline, 91% COD removal, and 85% total-N removal when glucose added as a supplemental electron donor once nitrate was formed.     

A dynamic model of the spatial spread of an infectious disease: the case of fox rabies in Illinois

A spatially explicit computer model is developed to examine the dynamic spread of fox rabies across the state of Illinois and to evaluate possible disease control strategies. The ultimate concern is that the disease will spread from foxes to humans through the pet population. Modeling the population dynamics of rabies in foxes requires comprehensive ecological and biological knowledge of the fox and pathogenesis of the rabies virus. Variables considered including population densities, fox biology, home ranges, dispersal rates, contact rates, and incubation periods, can greatly effect the spread of disease. Accurate reporting of these variables is paramount for realistic construction of a spatial model. The spatial modeling technique utilized is a grid-based approach that combines the relevant geographic condition of the Illinois landscape (typically described in a georeferenced database system) with a nonlinear dynamic model of the phenomena of interest in each cell, interactively connected to the other appropriate cells (usually adjacent ones). The resulting spatial model graphically links data obtained from previous models, fox biology, rabies information and landscape parameters using various hierarchical scales and makes it possible to follow the emergent patterns and facilitates experimental stimulus/result data collection techniques. Results of the model indicate that the disease would likely spread among the native healthy fox population from East to West and would occur in epidemiological waves radiating from the point of introduction; becoming endemic across the State in about 15 years. Findings also include the realization that while current hunting pressures can potentially wipe out the fox in the State, some level of hunting pressure can be effectively utilized to help control the disease. This revised version was published online in July 2006 with corrections to the Cover Date.     

Speciation/fractionation of nickel in airborne particulate matter: improvements in the Zatka sequential leaching procedure

Modifications are reported to the sequential leaching analytical method for nickel speciation/fractionation specified by Zatka so that larger sample masses can be analyzed. Improvements have been made in the completeness of the sulfide/metallic separation during the peroxide-citrate leach step by use of a larger volume of leachant, a longer leach duration and an orbital shaker. Minimal extraction of metallic nickel in this prolonged sulfidic nickel extraction has been confirmed. An increase in the number of samples analyzed simultaneously using these modifications has resulted in substantial productivity improvements and concomitant lower costs. It is critical for practitioners of sequential leaching techniques to recognize potential limitations and to use professional judgment when interpreting results. For example, results obtained may not be biologically relevant in assessing health risks; the acts of sampling and storage may result in changes in fractionation with time; surface coatings/films may alter the ability of a leachant to react with the target compound; and leaching behaviours may be different for samples differing only in particle size distributions.     

Assessing urban runoff program progress through a dry weather hybrid reconnaissance monitoring design

Characterizing dry weather conditions in urban Municipal Separate Storm Sewer Systems (MS4s), and then prioritizing and addressing problems due to urban pollutants, is a daunting challenge. The size and complexity of most MS4s and the ephemeral nature of many dry weather problems hamper efforts to identify and eliminate pollutant sources, and to track trends in condition. As a result, assessing overall program progress has proven difficult. We describe a hybrid dry weather urban monitoring design from southern California that combines probabilistic and targeted sampling to rigorously identify and prioritize problems and track program progress. Data from probabilistic sites define the urban background and establish tolerance intervals, which identify sites that persistently exceed the overall urban background. Targeted sites focus on locations where nearby activities and/or past history suggest that pollutant levels will be elevated. Embedding targeted monitoring within a probabilistic design enables data from targeted sites to be interpreted in a more meaningful regional context. Data from all sites are also used to construct site- and pollutant-specific control charts. These charts quickly identify instances where a site's behavior significantly changes, compared to its past behavior, suggesting an active source in the upstream drainage area. The hybrid design, and the use of formal statistical tools (tolerance intervals and control charts), permit the program to systematically prioritize problematic sites, compare conditions to the regional urban background, and track trends over time. In addition, the program's design allows several measures of program progress to be defined and thus consistently followed over time. Such hybrid designs can provide substantial advantages compared to more traditional monitoring approaches.     

Chemical and biological characteristics of streams in the Owabi watershed

In this investigation, concentrations of physico-chemical and bacteriological qualities of water samples from the major streams within the Owabi watershed in Kumasi, Ghana, were measured at five different locations. The streams were moderately soft and neutral, having a mean pH range of 7.08 ± 0.2 to 7.88 ± 0.6. Total dissolved solids, total suspended solids, grease and oil, alkalinity, and the major ion levels varied significantly at each sampling site. Nutrient levels were however low and did not show any clear variation at sample locations. The bacteriological quality of the water was poor, rendering it unsafe for domestic purposes without treatment. The poor bacteriological quality was due to direct contamination by animal and human wastes. The streams have an appreciable self-purification capacity which is stressed by persistent pollution overloads caused by expanding human activities within the catchment. Cluster analysis performed on the data to determine pollution patterns between the streams depicts that River Owabi was less polluted, Rivers Akyeampomene and Sukobri were moderately polluted, while River Pumpunase was highly polluted.     

Detection of polybrominated diphenyl ethers in tilapia (Oreochromis mossambicus) from O'ahu, Hawai;i

Polybrominated diphenyl ethers (PBDEs) have been detected for the first time at a range from 231.58 to 685.61 ng g(-1) lipid weight in the muscles of tilapia (Oreochromis mossambicus) collected from O'ahu, an island of the geographically isolated Hawaiian archipelago.     

Influence of geomorphological variability in channel characteristics on sediment denitrification in agricultural streams

Within fluvial systems, the spatial variability of geomorphological characteristics of stream channels and associated streambed properties can affect many biogeochemical processes. In agricultural streams of the midwestern USA, it is not known how geomorphological variability affects sediment denitrification rates, a potentially important loss mechanism for N. Sediment denitrification was measured at channelized and meandering headwater reaches in east-central Illinois, a region dominated by intensive agriculture and high NO(3)-N stream export, between June 2003 and February 2005 using the chloramphenicol-amended acetylene inhibition procedure. Sediment denitrification rates were greatest in separation zones, ranging from 0.6 to 76.4 mg N m(-2) h(-1), compared with riffles, point bars, pools, and a run ranging from 0 to 36.5 mg N m(-2) h(-1). Differences in benthic organic matter (r = 0.70) and the percentage of fine-grained sediments (r = 0.93) in the streambeds controlled much of the spatial variations in sediment denitrification among the geomorphological features. Although two meandering study reaches removed 390 and 99% more NO(3)-N by sediment denitrification than adjacent channelized reaches, NO(3)-N loss rates from all reaches were between 0.1 and 15.7% d(-1), except in late summer. Regardless of geomorphological characteristics, streams in east-central Illinois were not able to process the high NO(3)-N loads, making sediment denitrification in this region a limited sink for N.