PREDICTION OF LOCAL SCOUR AROUND BRIDGE PIERS USING ARTIFICIAL NEURAL NETWORKS1

This paper describes a method for predicting local scour around bridge piers using an artificial neural network (ANN). Methods for selecting input variables, calibrations of network control parameters, learning process, and verifications are also discussed. The ANN model trained by laboratory data is applied to both laboratory and field measurements. The results illustrate that the ANN model can be used to predict local scour in the laboratories and in the field better than other empirical relationships that are currently in use. A parameter study is also carried out to investigate the importance of each input variable as reflected in data.     

Salinity stress and hydrogen peroxide regulation of antioxidant defense system in Ulva fasciata

The regulation of antioxidant defense system in macroalgae exposed to salinity stress was examined in Ulva fasciata Delile. As compared to the 30‰ control, a long-term (4 days) exposure to hyposaline (5, 15‰) and hypersaline (60, 90, 120, 150‰) conditions inhibited growth rate and TTC reduction ability. A decrease in maximum quantum efficiency (F _v/F _m ratio) and the maintenance of superoxide dismutase activity under salinity stress indicate the potential generation of reactive oxygen species in chloroplasts. An exposure to 15, 60, and 90‰ decreased seawater H₂O₂ contents but increased thallus H₂O₂ contents that are positively correlated with TBARS and peroxide contents. Alleviation of oxidative damage and H₂O₂ accumulation at 15 and 90‰ by a H₂O₂ scavenger, dimethylthiourea, suggests that oxidative damage occurring under moderate hyposaline and hypersaline conditions is ascribed to accumulated H₂O₂. Increased glutathione reductase activity and glutathione content and decreased ascorbate content are responsible for accumulated H₂O₂ at 15, 60, and 90‰, while ascorbate peroxidase activity increased only at salinity ≥ 90‰. Catalase and peroxidase activities also increased at 60 and 90‰ for H₂O₂ removal, but only catalase showed activity increase at 15‰. For the regeneration of ascorbate, the activities of both dehydroascorbate reductase and monodehydroascorbate reductase were increased at 5 and 15‰ while only monodehydroascorbate reductase activity increased at 60 and 90‰. It is hypothesized that the availability of antioxidants and the activities of antioxidant enzymes are increased in U. fasciata to cope with the oxidative stress occurring in hyposaline and hypersaline conditions.     

Reproduction and growth of the freshwater prawn, Palaemon paucidens (Decapoda: Palaemonidae) in a lake of Korea

This study analyzed the reproduction and growth of freshwater prawn, Palaemon paucidens De Haan 1844 from Suk-dang lake(Korea). The analysis of the sex ratio showed a higher proportion of males than that of females. The average size of the eggs was 6.12 (+/-0.55) mm3 in the non-eyed stage (stageA) and 7.20 (+/-0.86)mm3 in the eyed stage (stage B). The reproductive output (RO) calculated with the dried-body weight of an incubating female and the weight of the eggs in dried condition was 26.97% (n = 17) of the average females weight. Incubating prawn appeared in April, and the gonadosomatic indices(GSI) showed the highest value during three months from January to March. Based on the month when there was a high proportion of incubating females with a high GSI, the estimated spawning season of P. paucidens was April. The maturity of the female was evaluated by the development of the ovaries and the existence of eggs. The average body length when 50% of the females in the group reached maturity was 8.55 (+/-2.74) mm. The analysis of the length-frequency distribution showed that the life span of P. paucidens ranged from 12 to 13 months. Females mature faster than males.     

Assessment of Young Dong tributary and Imgok Creek impacted by Young Dong coal mine,South Korea

An initial reclamation of the Young Dong coal mine site, located in northeastern South Korea, was completed in 1995. Despite the filling of the adit with limestone, acid rock drainage (ARD) enters Young Dong tributary and is then discharged to Imgok Creek. This ARD carries an average of 500 mg CaCO₃/l of mineral acidity, primarily as Fe(II) and Al. Before spring runoff, the flow of Imgok Creek is 3.3–4 times greater than that of the tributary and has an alkalinity of 100 mg CaCO₃/l, which is sufficient to eliminate the mineral acidity and raise the pH to about 6.5. From April through September 2008, there were at least two periods of high surface flow that affects the flow of ARD from the adit. Flow of ARD reaches 2.8 m³/min during spring runoff. This raised the concentrations of Fe and Al in the confluence with Imgok Creek. However, by 2 km downstream the pH of the Imgok Creek is 6.5 and only dissolved Fe is above the Korean drinking water criteria (0.30 mg/l). This suggests only a minor impact of Young Dong Creek water on Imgok Creek. Acid digestion of the sediments in Imgok Creek and Young Dong Tributary reveals considerable abundances of heavy metals, which could have a long-term impact on water quality. However, several water-based leaching tests, which better simulate the bioavailable metals pool, released only Al, Fe, Mn, and Zn at concentrations exceeding the criteria for drinking water or aquatic life.     

Geochemical occurrences of arsenic and fluoride in bedrock groundwater: a case study in Geumsan County,Korea

Rio Grande, the southernmost Brazilian port and industrial center, is marked by mercury-polluted ground cover. This pollution varies spatially, with levels exceeding 1,000 μg kg⁻¹ in 30% of the urban territory. The risk of Hg impact as a result of deliberate and involuntary geophagy is increased by restrained urban conditions in combination with the large proportion of the population living at low-income levels. Laboratory tests have demonstrated that ingestion of Hg-polluted soil by rats results in significant alterations in animal health such as stagnation in body weight increase, and significant mercury accumulation in the liver and kidney. The consumption of Hg-contaminated urban soil also provoked changes in hematological profiles of experimental animals by increasing the number of platelets. The present study indicates the potential for the local population of Rio Grande living in mercury-polluted districts, specifically young children, to experience health disturbances.     

A river water quality management model for optimising regional wastewater treatment using a genetic algorithm

To achieve water quality goals and wastewater treatment cost optimisation in a river basin, a water quality management model has been developed through the integration of a genetic algorithm (GA) and a mathematical water quality model. The developed model has been applied to the Youngsan River, where water quality has decreased due to heavy pollutant loads from Kwangju City and surrounding areas. Pollution source, land use, geographic features and measured water quality data of the river basin were incorporated into the Arc/View geographic information system database. With the database, the management model calculated treatment type and treatment cost for each wastewater treatment plant in the river basin. Until now, wastewater treatment policy for polluted rivers in Korea has been, first of all, to construct secondary treatment plants for untreated areas, and secondarily, to construct advanced treatment plants for the river sections whose water quality is impaired and for which the water quality goal of the Ministry of Environment is not met. Four scenarios that do not use the GA were proposed and they were compared with the results of the management model using the GA. It became clear that the results based on the GA were much better than those for the other four scenarios from the viewpoint of the achievement of water quality goals and cost optimisation.