The effect of emergent macrophytes on the dynamics of sulfur species and trace metals in wetland sediments

This study focuses on the effect of plants on the biogeochemistry of sulfur species and the mobility of heavy metals in wetland sediments. Results showed that, in the presence of plants, sediments had elevated sulfate concentrations in the rhizosphere during the growing season, ranging from 0.2 to 6.20 mmol L(-1), whereas only a small difference in the sulfate profiles between vegetated and non-vegetated sediments was observed during senescence. Based on the sulfate concentration increase, the oxygen release rate from the roots to achieve the corresponding oxidation of sulfide was estimated as 0.85 g m(-2) day(-1). Evapotranspiration-induced advection is a major contributor to the transport of sulfate from the water column into the sediments, and also allows dissolved trace metals (i.e. Cd, Pb, and Zn) to be transported into the sediments and react with the acid volatile sulfide pool, resulting in the immobilization of trace metals in these sediments.     

The environmental impact of industrialization in East Asia and strategies toward sustainable development

The East Asian economy has been growing fast in recent years, and environmental stresses are building up rapidly. Transboundary air pollution, water shortages, drinking water contamination, freshwater and marine pollution, deforestation, climatic disasters, and other environmental problems are becoming serious threats to the well-being of people in this densely populated region. The ESI (environmental sustainability index) reported by the World Economic Forum in 2005 is a good indicator of the environmental status of the region; most East Asian countries ranked at the bottom. East Asia is not moving toward a sustainable society, and the environment will not sustain the current rate of economic development for long. The traditional culture of East Asia used to be sustainable, so we can learn much from our traditions. Land use should be planned from an ecological point of view so as to best preserve the land’s productivity and stability. There should be definite goals as to where and how much to preserve the three important ecological bases: forests, coastal wetlands and agricultural farms. The forest is the base for the terrestrial ecosystem, including flood control, water resources, and climate; the coastal wetland is the base for the marine ecosystem; farmland is the base for producing food. Within these defined goals, limits should be set on how much land can be utilized for activities like urban development, manufacturing, and recreation. Limits on the pollution load resulting from such activities should be set so as not to irreversibly damage the environment. Economic development should be planned to allow the use of energy and resources only after satisfying these constraints.

A taxonomy of performance influencing factors for human reliability analysis of emergency tasks

This paper introduces the process for, and the result of, the selection of performance influencing factors (PIFs) for the use in human reliability analysis (HRA) of emergency tasks in nuclear power plants. The approach taken in this study largely consists of three steps. First, a full-set PIF system is constructed from the collection and review of existing PIF taxonomies. Secondly, PIF candidates are selected from the full-set PIF system, considering the major characteristics of emergency situations and the basic criteria of PIF for use in HRA. Finally, a set of PIFs is established by structuring representative PIFs and their detailed subitems from the candidates. As a result, a set of PIFs comprised of the 11 representative PIFs and 39 subitems was developed.     

Electrocoagulation process for the treatment of metal-plating wastewater: Kinetic modeling and energy consumption

The wastewater from industrial area was treated by EC via Fe and Al electrodes. Cu, Ni, Cr and Zn were highly removed at the first minutes, simultaneously. Pseudo-2nd-order was found to be more suitable for kinetics. Adsorption capacities based on kinetic modeling were observed as Cr>Cu>Ni>Zn. The chemical cost in the case of pH adjustment after EC was less as 3.83 $/m³. It is known that wastewater produced by the metal-plating industry contains several heavy metals, which are acidic in nature and therefore toxic for the environment and for living creatures. In particular, heavy metals enter the food chain and accumulate in vital organs and cause serious illness. The precipitation of these metals is mostly achieved by pH adjustment, but as an alternative to this method, the electrocoagulation process has investigated in this study using iron and aluminum electrodes. The effects of the pH adjustment on removal before and after the electrocoagulation process were investigated, and cost analyses were also compared. It was observed that a high proportion of removal was obtained during the first minutes of the electrocoagulation process; thus, the current density did not have a great effect. In addition, the pH adjustment after the electrocoagulation process using iron electrodes, which are 10% more effective than aluminum electrodes, was found to be much more efficient than before the electrocoagulation process. In the process where kinetic modeling was applied, it was observed that the heavy metal removal mechanism was not solely due to the collapse of heavy metals at high pH values, and with this modeling, it was seen that this mechanism involved adsorption by iron and aluminum hydroxides formed during the electrocoagulation process. When comparing the ability of heavy metals to be adsorbed, the sequence was observed to be Cr>Cu>Ni>Zn, respectively.     

On the Estimation of Dispersal Kernels from Individual Mark-Recapture Data

We present a new method for estimating a distribution of dispersal displacements (a dispersal kernel) from mark-recapture data. One conventional method of calculating the dispersal kernel assumes that the distribution of displacements are Gaussian (e.g. resulting from a diffusion process) and that individuals remain within sampled areas. The first assumption prohibits an analysis of dispersal data that do not exhibit the Gaussian distribution (a common situation); the second assumption leads to underestimation of dispersal distance because individuals that disperse outside of sampling areas are never recaptured. Our method eliminates these two assumptions. In addition, the method can also accommodate mortality during a sampling period. This new method uses integrodifference equations to express the probability of spatial mark-recapture data; associated dispersal, survival, and recapture parameters are then estimated using a maximum likelihood method. We examined the accuracy of the estimators by applying the method to simulated data sets. Our method suggests designs for future mark-recapture experiments. Received: January 2004 / Revised: July 2005     

Simulating the dynamics of sulfur species and zinc in wetland sediments

In situ measurements comparing vertical SO₄²⁻ profiles in vegetated and non-vegetated sediments showed that SO₄²⁻ concentrations in vegetated sediments increased significantly at the beginning of the growing season and then gradually decreased during the rest of the growing season. Throughout the growing season, SO₄²⁻ concentrations remained higher in the vegetated sediments than in the sediments without plants. The higher SO₄²⁻ concentrations in the vegetated sediments indicate that oxygen release from roots and evapotranspiration-induced advection by plants play an important role in the dynamics of sulfur species in sediments. Since the total pool of solid-phase sulfide is relatively large compared to the mass of SO₄²⁻ in the sediments, the gradual decrease of SO₄²⁻ concentrations may result from limitation of the solid-phase sulfide that is in direct contact with or very close to the roots and rhizomes. This would mean that the main pool of solid-phase sulfide and associated trace metals are not affected by the oxygen release from roots, and the associated trace metals will not become bioavailable during the growing season.     

Time-course uptake and elimination of benzo(a)pyrene and its damage to reproduction and ensuing reproductive outputs of Pacific oyster, <Emphasis Type="Italic">Crassostrea gigas</Emphasis>

The time-course of uptake and elimination of benzo(a)pyrene (BaP) for the Pacific oyster, Crassostrea gigas and reproduction damage and reproductive outputs were studied. Sexually immature C. gigas broodstock were fed for 28 days with live algae grown in four BaP solutions of 0, 50, 500, and 5,000 μg L⁻¹ (hereafter, control, 50, 500, and 5,000 oysters) and were subsequently conditioned to maturation by a feeding with BaP-free live algae under temperature manipulation for another 28 days. The 5,000 μg L⁻¹ oysters gained a steady state concentration, around 30,000 ng g⁻¹ d.w. for digestive gland, a week earlier compared to the 500 μg L⁻¹ oysters. The earlier gain or longer persistence of the steady state concentration influenced elimination of BaP, with an eliminating trend for 500 μg L⁻¹ oysters, while no elimination for 5,000 μg L⁻¹ oysters. The maternal persistence of the steady state concentration resulted in significant damages in the reproductive success and their reproductive outputs in terms of the hatching rate and larval growth, survival, and settlement. The 50 μg L⁻¹ oysters remained far below the steady state concentration, and showed a manifest eliminating behavior during the subsequent BaP-free 28 day maturation period. The reproductive success and initial larval events of 50 μg L⁻¹ oysters were comparable to those of control. However, the damage potential of the 50 μg L⁻¹ oysters might be more significant if their maternal exposure continued beyond 28 days, since the accumulation profile at this dose was linear.