Primary production estimated for large lakes and reservoirs in the Mekong River Basin.

Understanding the proximate factors and mechanisms driving primary production in manmade reservoirs is crucial because such production can translate into added fish yields that provide people with food and livelihoods. Furthermore, reservoir fish production could potentially compensate for the loss of fish yields due to habitat fragmentation and alterations caused by damming and impoundment. We monitored primary production, identified environmental factors responsible for its variability, and examined the relationship between primary production and fish production in nine large water bodies of the Lower Mekong Basin for 2 years.

Comparison of 0.1 M Stable CsCl and 1 M NHNO as an Extraction Reagent to Evaluate Cs-137 Mobility in Soils.

To evaluate the mobility and bioavailability of Cs in soils, we compared the extraction of Cs with stable Cs and ammonium solutions from Cs-contaminated minerals and soils. The extraction yields of Cs with stable Cs were significantly lower than those with ammonium for minerals with frayed edge sites, but such differences were not observed for minerals without frayed edge sites. The amount of Cs extracted with stable Cs from soils was lower than, or equal to, that extracted with ammonium.

Composition and Elution Behavior of Various Elements from Printed Circuit Boards, Cathode-ray Tube Glass, and Liquid-crystal Displays in Waste Consumer Electronics.

The contents and elution behavior of metals in consumer electronics parts were determined so as to understand their maximum environmental risk. Elements contained most in printed-circuit boards were Cu, Si, Br, Ca, Al, Sn, Pb, Sb, Ba, Fe, Ni, Ti, and Zn; in cathode-ray tube glass were Si, Pb, Ba, Sr, Zn, Zr, Ca, and Sb; in arsenic contained liquid-crystal displays were Si, Ca, Sr, Ba, As, and Fe; and in antimony contained liquid-crystal displays were Si, Ba, Ca, Sb, Sr, Fe, and Sn. The elements eluted most from printed-circuit boards were Zn, Pb, and Cu; from cathode-ray tube glass were Pb, Zn, B, Ba, and Si; and from liquid-crystal displays were B and Si, and the toxic As and Sb.

The dynamics of pico-sized and bloom-forming cyanobacteria in large water bodies in the Mekong River Basin.

In the face of plans for increased construction of dams and reservoirs in the Mekong River Basin, it is critically important to better understand the primary-producer community of phytoplankton, especially the warm-water cyanobacteria. This is because these algae can serve as the primary source of carbon for higher trophic levels, including fishes, but can also form harmful blooms, threatening local fisheries and environmental and human health. We monitored the dynamics of three cyanobacteria-Synechococcus spp.

Migration of Ag, In, Sn, Sb, and Bi and Their Chemical Forms in a Monolith Lysimeter Filled with a Contaminated Andosol.

Despite the wide use of trace metals in various technologies, such as chemical industries and electronic equipment, insufficient information is available on their behavior in the environment. We investigated changes in chemical forms and vertical distribution during the migration processes of trace metals, whose usage is currently increasing rapidly, such as Ag, In, Sn, Sb, and Bi, in soil contaminated with the equivalent of 50-100 times the background concentrations of these metals using an indoor control type monolith lysimeter filled with Andosol during an 8-year monitoring period. The vertical distribution of the total elemental concentrations, the mobile fractions (exchangeable, carbonate-bound, and metal-organic complex-bound) in soils, and the total elemental concentrations in soil solutions were analyzed to study trace metal migration in soil.

Bismuth solubility through binding by various organic compounds and naturally occurring soil organic matter.

The present study was performed to examine the effects of soluble organic matter and pH on the solubility of Bi in relation to inference with the behavior of metallic Bi dispersed in soil and water environments using EDTA, citric acid, tartaric acid, L-cysteine, soil humic acids (HA), and dissolved organic matter (DOM) derived from the soil organic horizon. The solubility of Bi by citric acid, tartaric acid, L-cysteine, HA, and DOM showed pH dependence, while that by EDTA did not. Bi solubility by HA seemed to be related to the distribution of pKa (acid dissociation constant) values of acidic functional groups in their molecules.

Pollution of montane soil with Cu, Zn, As, Sb, Pb, and nitrate in Kanto, Japan.

Soil cores and rainwater were sampled under canopies of Cryptomeria japonica in four montane areas along an atmospheric depositional gradient in Kanto, Japan. Soil cores (30cm in depth) were divided into 2-cm or 4-cm segments for analysis. Vertical distributions of elemental enrichment ratios in soils were calculated as follows: (X/Al)(i)/(X/Al)(BG) (where the numerator and denominator are concentration ratios of element-X and Al in the i- and bottom segments of soil cores, respectively).

Weathering and dissolution rates among Pb shot pellets of differing elemental compositions exposed to various aqueous and soil conditions.

The present study was performed to investigate the weathering and dissolution rates of Pb shot pellets differing in elemental composition (Pb, Sb, and As) exposed under various aqueous and soil conditions using five commercial shot pellet preparations. Upon immersion in distilled water, the dissolution rates of shot pellets, calculated from the difference in weight before versus after immersion, decreased with increasing Sb + As contents and the dominant precipitate was hydrocerussite. These subsidiary ingredients may be related to the difficulty of metallic Pb oxidation (transformation to PbO).

Effects of bismuth contamination on the growth and activity of soil microorganisms using thiols as model compounds.

The present study was undertaken to obtain information about the effects of Bi contamination on soil microbial growth and activity using a series of Bi complexes with thiol compounds, including mercaptoethanol, thioglycerol, mercaptoethylamine, thioglycolic acid, thiomallic acid, reduced glutathione, 2-mercaptopropionic acid, and L-cysteine. We found that Bi complexes with mercaptoethanol, thioglycerol, and mercaptoethylamine, all of which showed lipophilicity, markedly inhibited bacterial growth in 1/10 TSB liquid media in both Eutric Cambisol (brown forest soil) and Eutric Fluvisol (brown lowland soil), with relative CFU of less than 2% at 50 micro M Bi and 6% at 25 micro M Bi. However, none of the Bi-thiols, including Highly lipophilic complexes, at 200 micro M Bi in rosebengal agar medium inhibited fungal growth, possibly because fungi have a metabolic system that protects against Bi uptake or detoxifies Bi compounds.