Gram-negative bacteria responsible for insoluble technetium formation and the fate of insoluble Tc in the water column above flooded paddy soil

We studied the characteristic gram-stain of Tc insolubilizing bacteria using various antibiotics, and the fate of insoluble Tc in a water column above flooded paddy soil to clarify Tc behavior in paddy fields. The formation of insoluble Tc in water column samples was inhibited by the addition of antibiotics, especially reagents against gram-negative bacteria. For a sample without antibiotics, insoluble Tc formation increased with time, and the maximum amount of insoluble Tc was observed on day 4 of incubation with (95m)Tc. In contrast, concentrations of ferrous ion decreased with time. These results suggested that gram-negative bacteria were mainly responsible for insoluble Tc formation, and that these bacteria were able to transform soluble Tc to insoluble forms under oxidizing conditions.     

Degradation of chlorinated dioxin in denitrifying activated sludge from leachate treatment plant of a landfill

The degradation rate of dioxins added to the activated sludge from a leachate treatment plant of a landfill under denitrification conditions was estimated using six bioreactors. Over 99% of the added dioxins (600ng) were degraded within 7 days. Furthermore, continuous cultivation was carried out for 1 month. The activated sludge degraded 600ng of dioxins (that is, all of the added dioxins) placed in each reactor every 7 days, and this activity was maintained for 35 days. Under aerobic conditions with this sludge, the dioxins were not degraded in 7 days, but 90% of the 600ng of dioxins was degraded in 35 days. The high level of activity observed in the present study may only occur under anaerobic conditions, especially under denitrifying conditions.     

A knowledge network to promote the use and valorization of wild food plants in the Pantanal and Cerrado,Brazil

Regional Environmental Change - The conservation and use of wild food plants should include local people in the decision-making process, and many countries have done so. However, interacting with...     

Environmental conditions for the formation of insoluble Tc in water ponds located above paddy fields

Optimum conditions for the formation of insoluble Tc (Tc in >0.2 microm size fraction) were studied using a microcosm including water ponds above a paddy field to understand Tc behavior in such fields. In the microcosm, soluble TcO(4)(-) was converted to insoluble forms, but no changes in the form of Tc were observed in filtered microcosm samples which were microorganisms-free. The formation of insoluble Tc was inhibited by the addition of the antibiotic chloramphenicol. In addition, the reduction of soluble Tc(VII)O(4)(-) to low-valence oxide was not observed in the filtered microcosm samples, although reducing conditions were present. These results indicated that bacteria were involved in the formation of insoluble Tc. Since oxidizing conditions influence bacterial metabolism, the formation of insoluble Tc by bacteria was studied under aerobic and anaerobic conditions. The results showed that anaerobic conditions were favorable for the formation of insoluble Tc. In addition, the addition of formate as an electron donor to a microcosm sample facilitated the formation of insoluble Tc. The results suggested that insoluble Tc in the water ponds above paddy fields was caused by bacteria, which were shown to couple the oxidation of formate to the reduction of Tc(VII) during anaerobic respiration.     

Analysis of bumblebee visitation sequences within single bouts: implication of the overstrike effect on short-term memory

Pollinators whose foraging habitats consist of several plant types (species or morph) may continue to choose the plant type last visited because information about the type of plant last visited dominates over all other memory contents, in particular of short-term memory. In this study, I extracted this overstrike effect on the plant choices of pollinators by analyzing patterns of visitation sequences within a single round-trip between the hive and foraging patch (bout). First, I simulated the visitation sequences within single bouts with a model to show how factors, including the bees plant-type preferences, the arrangement of plants and the effect of overstrike on short-term memory, affect visitation sequences. Here, bees are assumed to forage in a patch consisting of two plant types (H and L). The model predicts that only the effect of overstrike on short-term memory causes assorted visitation sequences according to plant type (within-bout flower constancy). That is, if the overstrike-effect on short-term memory is the primary determinant of plant choice, then bees will fly to a type-L plant after visiting a type-L plant even if they predominantly visit type-H plants and vice versa. Next, I investigated individual bumblebees visitation sequences at a patch of artificial inflorescences with a set-up similar to that assumed in the model. Two types of inflorescences were arranged on a Cartesian grid. Assorted visitation sequences according to inflorescence type were observed, depending on the distances among inflorescences. This result supports the hypotheses that bees fly to the same plant type as that last visited because short-term memory is displaced (overstruck) with information about the most recently visited plant type.Communicated by M. Giurfa     

Treatment of textile dye wastewater using ozone combined with photocatalyst

Ozonolysis combined with photocatalysis was used as a new approach for the treatment of textile dye wastewater containing azo dyes. The color reduction was very fast when only ozone was used for the treatment, but a 90% Total Organic Carbon (TOC) reduction was obtained only during a combined treatment. Reactive Black 5 dye containing two different percentages of NaCl was used for the experiment. The color reduction was fast in the neutral and basic pH. However for a fast TOC reduction acidic pH was found to be more effective. On‐line UV‐Vis spectrophotometry was used to measure the color reduction.     

Physicochemical forms of technetium in surface water covering paddy and upland fields

The behavior of an element in the environment depends on its physicochemical form. Basic data for the behavior of technetium in an agricultural environment were obtained by determining the physicochemical forms of Tc in 28 surface water samples from paddy and upland fields. Most of the (95m)Tc was present as TcO(4)(-) in the samples. The relative amount of this chemical form was 72% on average. A significant amount of insoluble Tc (particles more than 0.2 microm in size), however, was found in some samples. The maximum amount of the insoluble Tc was 91%. Other forms were found in insignificant amounts. The amount of insoluble Tc was relatively high in paddy soil samples. Paddy soils, gley soils and gray lowland soils were particularly effective in the insolubilization of Tc. Among the soil characteristics studied, cation exchange capacity, anion exchange capacity, and active aluminum showed significant correlations with the relative amount of insoluble Tc. When microorganisms were eliminated from the surface water samples before the addition of (95m)TcO(4)(-), little insoluble Tc was found, suggesting that microorganisms cause the physicochemical transformation. These results showed that the physicochemical form of Tc changes from TcO(4)(-) to insoluble forms in surface water covering paddy fields. The insoluble forms would restrict the mobility of Tc in paddy fields.     

Influence of microorganisms on the behavior of technetium and other elements in paddy soil surface water

Insolubilization patterns of technetium (Tc) and other trace elements (Sc, Co, Zn, Se, Rb, Sr, Y, Nb, Ce, Pm, Gd, Lu, Hf, and Re) in surface water covering paddy fields were compared to gain insight into the behavior of Tc in an agricultural environment. The insolubilization of Tc, which did not pass through a 0.2-microm-pore-size filter, was mainly caused by bacteria. Among the 14 other elements investigated, Nb was insolubilized by bacteria and the amounts of insoluble Nb were positively correlated with those of Tc. Although Re is a chemical analog of Tc, no similarity was observed. These results suggest that Tc behaves similarly to Nb in the insolubilization in surface water covering paddy fields.     

Microfluidic quantification of multiple enteric and opportunistic bacterial pathogens in roof-harvested rainwater tank samples

Potable and non-potable uses of roof-harvested rainwater (RHRW) are increasing due to water shortages. To protect human health risks, it is important to identify and quantify disease-causing pathogens in RHRW so that appropriate treatment options can be implemented. We used a microfluidic quantitative PCR (MFQPCR) system for the quantitative detection of a wide array of fecal indicator bacteria (FIB) and pathogens in RHRW tank samples along with culturable FIB and conventional qPCR analysis of selected pathogens. Among the nine pathogenic bacteria and their associated genes tested with the MFQPCR, 4.86 and 2.77% samples were positive for Legionella pneumophila and Shigella spp., respectively. The remaining seven pathogens were absent. MFQPCR and conventional qPCR results showed good agreement. Therefore, direct pathogen quantification by MFQPCR systems may be advantageous for circumstances where a thorough microbial analysis is required to assess the public health risks from multiple pathogens that occur simultaneously in the target water source.