Bioaccumulation of mercury in a vestimentiferan worm living in Kagoshima Bay,Japan

The present study reports on the mercury concentrations of the vestimentiferan worm, Lamellibrachia satsuma, (Annelida: Pogonophora) found near hydrothermal vents at a depth of 80-100 m in the northern parts of Kagoshima Bay. The vestimentiferan worms had total mercury concentrations of 238 ng/g in the anterior muscle of the body and 164 ng/g in the posterior trophosome. Methylmercury constituted only 7.6% of total mercury detected anteriorly and 16.3% posteriorly. The mean total mercury concentration in filtrated ambient seawater of the worm habitat was 1.1 ng/l. The worm should accumulate mercury in seawater by a one-step into the anterior and posterior parts as 2.2 x 10(%) and 1.5 x 10(5) times those of the filtered ambient seawater, respectively. The bioaccumulation factor of mercury by the worms with only their respiration would be actually larger than that by other marine animals through food webs. The high bioaccumulation factor of mercury in the worms suggest the following two possibilities: (i) the biological half-life of organomercury in the worm could be exceptionally long; or (ii) the lifetime of vestimentiferan worms examined in the present study could be extremely long. Various metals in one specimen of the worm were analyzed by using ICP-MS, and then gold as well as silver were detected in the worm. Gold was detected for the first time from marine animals.     

Variation in CO2 assimilation rate induced by simulated dew waters with different sources of hydroxyl radical (*OH) on the needle surfaces of Japanese red pine (Pinus densifora Sieb. et Zucc.)

The hydroxyl radical (*OH) is generated in polluted dew on the needle surfaces of Japanese red pine (Pinus densiflora Sieb. et Zucc.). This free radical, which is a potent oxidant, is assumed to be a cause of ecophysiological disorders of declining trees on the urban-facing side of Mt. Gokurakuji, western Japan. Mists of *OH-generating N(III) (HNO2 and NO2-) and HOOH + Fe + oxalate solutions (50 and 100 microM, pH 5.1-5.4) simulating the dew water were applied to the foliage of pine seedlings grown in open-top chambers in the early morning. Needles treated with 100 microM N(III) tended to have a greater maximum CO2 assimilation rate (Amax), a greater stomatal conductance (g(s)) and a greater needle nitrogen content (Nneedle), suggesting that N(III) mist acts as a fertilizer rather than as a phytotoxin. On the other hand, needles treated with 100 microM HOOH + Fe + oxalate solution showed the smallest Amax, g(s), and Nneedle, suggesting that the combination of HOOH + Fe + oxalate caused a decrease in needle productivity. The effects of HOOH + Fe + oxalate mist on pine needles were very similar to the symptoms of declining trees at Mt. Gokurakuji.     

Energy reduction of a submerged membrane bioreactor using a polytetrafluoroethylene (PTFE) hollow-fiber membrane

The fiber length and packing density of the PTFE membrane element were increased. The MBR was stably operated under an SAD^m of 0.13 m³·m^-2·hr^-1. Specific energy consumption was estimated to be less than 0.4 kWh·m^-3. In this study, we modified a polytetrafluoroethylene (PTFE) hollow-fiber membrane element used for submerged membrane bioreactors (MBRs) to reduce the energy consumption during MBR processes. The high mechanical strength of the PTFE membrane made it possible to increase the effective length of the membrane fiber from 2 to 3 m. In addition, the packing density was increased by 20% by optimizing the membrane element configuration. These modifications improve the efficiency of membrane cleaning associated with aeration. The target of specific energy consumption was less than 0.4 kWh·m^-3 in this study. The continuous operation of a pilot MBR treating real municipal wastewater revealed that the MBR utilizing the modified membrane element can be stably operated under a specific air demand per membrane surface area (SAD_m) of 0.13 m³·m^-2·hr^-1 when the daily-averaged membrane fluxes for the constant flow rate and flow rate fluctuating modes of operation were set to 0.6 and 0.5 m³·m^-2·d^-1, respectively. The specific energy consumption under these operating conditions was estimated to be less than 0.37 kWh·m^-3. These results strongly suggest that operating an MBR equipped with the modified membrane element with a specific energy consumption of less than 0.4 kWh·m^-3 is highly possible.     

Spatio-temporal variations in the diet and stable isotope composition of the Argentine hake <Emphasis Type="Italic">Merluccius hubbsi</Emphasis> Marini, 1933 of the continental shelf of southeastern Brazil

The feeding ecology of Merluccius hubbsi was investigated in 2 regions of SE Brazil. The major food sources for the hakes were fish, crustaceans, and squid. In the upwelling system of Cabo Frio, the diet was very similar in the summers of 2001/2002 and spring 2002; fish were the most important prey followed by crustaceans. In Ubatuba, euphausiids were an important prey during the winter 2001 (100 m), while in the summer 2002, fish and amphipods predominated in the diet in the shallower site (40 m) and squid in the deeper site (100 m). The hakes showed temporal differences in stable isotope signatures in both regions, while C:N ratios varied only in Cabo Frio. δ¹⁵N and δ¹³C (bulk and corrected for lipid content) increased with fish length, which seems to be related to the increasing importance of fish and decreasing importance of euphausiids and amphipods in the diet of larger hakes. The mean trophic level of 3.7 for M. hubbsi was estimated using δ¹⁵N of bivalves as baseline and the fractionation of 3.4‰ between trophic levels.     

Temporal variation of Cs and Pu in the sea of Japan

Concentrations of the anthropogenic ¹³⁷Cs and ^239,240Pu in surface water of the Sea of Japan were in the ranges of 2·7–3·8 mBq l^-1 and 1·3–8·0 μBq l^-1, respectively, in 1993–1994, which are in the same order of magnitude as those in the North Pacific. The time-series data indicated a marked increase of surface ¹³⁷Cs in 1986 and 1987 after the major radioactive dumping and the Chernobyl fallout in 1986 and then rapidly decreased thereafter. The apparent half-residence time of ¹³⁷Cs in the surface water was estimated to be about 3 years for excess ¹³⁷Cs and 16 years for a rather long time-scale transport, respectively. For ^239,240Pu in the surface water, no systematic temporal variation was observed over the past two decades, which may reflect rapid recycling of deeper Pu. The results revealed that most of the recent radioactivity in water columns of the Sea of Japan was of global fallout origin from atmospheric nuclear testing and partly the Chernobyl fallout. No clear signal about the effect of radioactivity from Russian dumping was observed.     

The sorption of heavy metal species by sediments in soakaways receiving urban road runoff

Infiltration facilities are designed for both the retention of non-point pollutants and the replenishment of groundwater in urban areas. In this study, sorption tests were conducted to evaluate the speciation of heavy metals and their behaviour in infiltration facilities receiving urban road runoff containing high DOC concentrations and stable heavy metal organic complexes. Road dust and three soakaway sediments were collected from heavy traffic areas and a residential area with an infiltration-type sewerage system in Tokyo, Japan. Sequential multiple batch tests were conducted by adding prepared road dust leachate (artificial road runoff) or deionised water to soakaway sediment to obtain soakaway sediment leachate (artificial percolating water from soakaway sediment), which mimicked the sorption by sediments in soakaways receiving urban road runoff. Heavy metal speciation was assessed by means of a combination of anion-exchange resin measurements and MINTEQA2 model calculations, and further validated by chelating resin measurements. In road dust leachates and soakaway sediment leachates, Cu predominantly existed as organic complexes and carbonates, whereas most Mn, Zn and Cd were found to exist in the form of free ions and carbonate complexes. Stable organic complexes of Cu in road dust leachates were strongly adsorbed by soakaway sediments despite the limited adsorption of DOC. On the other hand, desorption of free Mn, Zn and Cd ions from the sediment receiving road dust leachates was observed, indicating that heavy metals such as Mn, Zn and Cd may ultimately reach groundwater as free ions.     

Analysis of biomagnification of persistent organic pollutants in the aquatic food web of the Mekong Delta, South Vietnam using stable carbon and nitrogen isotopes

The present study elucidated the biomagnification profiles of persistent organic pollutants (POPs) through a tropical aquatic food web of Vietnam based on trophic characterization using stable nitrogen analysis. Various biological samples collected from the main stream of the Mekong Delta were provided for the analysis for both POPs, and stable nitrogen and carbon isotope ratios. Of the POPs analyzed, dichlorodiphenyltrichloroethane and its metabolites (DDTs) were the predominant contaminants with concentrations ranging from 0.058 to 12 ng/g wet weight, followed by polychlorinated biphenyls (PCBs) at 0.017-8.9 ng/g, chlordane compounds (CHLs) at 0.0043-0.76 ng/g, tris-4-chlorophenyl methane (TCPMe) at N.D.-0.26 ng/g, hexachlorocyclohexane isomers (HCHs) at N.D.-0.20 ng/g and hexachlorobenzene (HCB) at 0.0021-0.096 ng/g. Significant positive increases of concentrations in DDTs, CHLs, and TCPMe against the stable nitrogen ratio (delta(15)N) were detected, while, concentrations of HCHs and HCB showed no significant increase. The slopes of the regression equations between the log-transformed concentrations of these POPs and delta(15)N were used as indices of biomagnification. The slopes of the POPs for which positive biomagnification was detected ranged from 0.149 to 0.177 on a wet weight basis. The slopes of DDTs and CHLs were less than those reported for a marine food web of the Arctic Ocean, indicating that less biomagnification had occurred in the tropical food web. Of the isomers of CHLs, unlike the studies of the Arctic Ocean, oxychlordane did not undergo significant biomagnification through the food web of the Mekong Delta. This difference is considered to be due to a lack of marine mammals, which might metabolize cis- and trans-chlordane to oxychlordane, in the Mekong Delta ecosystem. The biomagnification profile of TCPMe is reported for the first time in the present study.     

Spatial heterogeneity of vegetation under different grazing intensities in the Northwest Heilongjiang Steppe of China

In northern China, recent degradation of semi-arid grasslands caused by overgrazing is serious. At Green Grassland Village, west of Daqing City in Heilongjiang Province, three grasslands with different degrees of degradation were surveyed. In the survey, a new method of vegetation analysis based on the beta-binomial distribution, was adopted to describe the frequency of occurrence and spatial heterogeneity for each plant species.Chenopodium centrorubrum, Cleistogenes squarrosa and a Carex species were commonly found in the three grasslands. Non-degraded grassland with light grazing was dominated by Arundinella hirta, Filifolium sibiricium, Lespedeza hedysaroides, Potentilla verticillaris, Stipa baicalensis and Thymus serpyllum. These species belong to the erect-type or do not develop large clones under light grazing. These species can be used as indicators of a well-managed grassland in this area. On the other hand, the degraded grassland with heavy grazing was dominated by Artemisia spp. and Euphorbia humifusa var. pilosa. Artemisia spp., E. humifusa var. pilosa, Eragrostis pilosa and Setaria viridis belong to the creeping-type or develop rather large stocks or stolons under heavy utilization. These species increased the spatial heterogeneity in the degraded grassland with heavy grazing.Under degraded conditions, species diversity decreased and spatial heterogeneity of the communities tended to increase.     

An estimate of the conversion rates of SO2 to SO2-4 and NO2 to HNO3+ NO3- for the evaluation air pollution in Beijing

The conversion rates of SO₂ to SO^2-₄ and NO₂ to HNO₃₊NO₃- are estimated from the field-data obtained in Beijing in summer, 1988. The results show that the conversion rate of NO₂ is about four times as much as that of SO₂; The conversion rates have a diurnal variation in a day. On the average, the rate of SO₂ is estimated to be 4.7% h^-1 during the daytime and 3.4% h^-1 during the nighttime. Similarly, the rate of NO₂ is estimated to be 17.2% h^-1 and 12% h^-1 respectively.