Comparison of general water quality of rivers in Indonesia and Japan

In Java and Kalimantan in Indonesia, river water plays important roles in human life; for example, for transportation, and economic activities of the inhabitants. However, industrial, agricultural and domestic water is discarded into rivers directly in many developing countries, including Indonesia, since drainage systems have not been completely constructed. In this study, to evaluate the water quality and to compare those levels of environmental contaminants in developing and developed countries, water quality and contents of endocrine disrupters were measured in a total of 64 water samples (Indonesia; 28 samples and Japan; 36 samples) from 53 sites. The results indicated that, rivers in both capital cities, Jakarta and Tokyo, were contaminated. Water in rivers in Indonesia was not so heavily polluted as in Japan. Pollution in the river water in Indonesia appeared to be caused by the lack of sewerage systems. In addition, the findings on endocrine disrupters indicated that the concentration of alkylphenol in water samples was large enough to affect living organisms.     

Evaluation method of automobile recycling systems for Asia considering international material cycles: application to Japan and Thailand

To examine an appropriate recycling system for end-of-life vehicles (ELVs) from Japan in the context of Asia, an Asian international automobile recycling input-output (AI-ARIO) analysis is presented. The AI-ARIO analysis spatially expands the existing ARIO analysis within the framework of the waste input-output (WIO) analysis developed by Nakamura et al., which considers the interdependence between the flow of goods and wastes in a country. This analysis focuses on the local and global cycles for ELVs in Asia and can evaluate the environmental and economic effects of alternative recycling systems. We estimated the AI-ARIO table for Japan and Thailand and applied it to scenario analyses covering the restriction of ELV trade between the two countries, the introduction of new recycling techniques in Thailand, and centralized treatment in Japan. We verified the applicability and effectiveness of the AI-ARIO analysis through the scenario analyses.     

Organic acids and aldehydes in throughfall and dew in a Japanese pine forest

We analyzed low molecular weight organic acids and aldehydes in throughfall under pine forest, and organic acids in dew on chemically inert surfaces and pine needle surfaces at urban- and mountain-facing sites of pine forest in western Japan. Low molecular weight organic acids and aldehydes accounted for less than 5% of the dissolved organic carbon in throughfall at both sites. Formaldehyde at both sites and formate at the mountain-facing site were found at significantly lower concentrations in throughfall than in rainfall, which may be explained by the degradation and/or retention of these components by the pine canopy as the incident precipitation passed through it. The oxalate concentration in throughfall was significantly higher than those in rainfall at both sites, suggesting that oxalate was derived from leaching from the pine foliage. At both sites, organic acid concentrations were higher in dew on the pine needles than in throughfall or dew on chemically inert surfaces. This could be due to the long contact time of dew on pine needles, during which leached substances from pine needles and dry deposits accumulated on their surfaces can dissolve into the small volume of dew. The role of enhanced concentrations of oxalate in an aqueous phase on the plant surfaces (e.g., dew) is discussed in relation to hydroxyl radical formation via the photo-Fenton reaction.     

Photodegradation of hexachlorobenzene and theoretical prediction of its degradation pathways using quantum chemical calculation

Experimentally determined photodegradation pathways of hexachlorobenzene (HCB), a chlorinated aromatic compound, in hexane, 2-propanol (IPA), and methanol were compared with those predicted by quantum chemical calculation based on density functional theory (DFT), and the adequacy of the prediction method was evaluated. The experimental main degradation pathways of HCB were virtually the same for the three solvents and also agreed with the predicted main degradation pathways. In the DFT method, the main degradation product was the dechlorinated benzene at the position where the C-Cl bond was predicted to have the lowest bond dissociation energy. This result suggested that the photodechlorination pathways of chlorinated aromatic compounds could be predicted by comparing the bond dissociation energies calculated with the DFT method.     

Pyrolysis of tetrabromobisphenol-A containing paper laminated printed circuit boards

Tetrabromobisphenol-A (TBBA) is the most common brominated fire retardant. In this study, a TBBA containing paper laminated printed circuit board (PCB) prepared from novolac was pyrolysed by both TGA and in a quartz glass reactor between 40 and 1,000 degrees C. The products were online detected by MS. It was found that the PCB degraded in three steps. Step one (<270 degrees C) consisted of the evolution of water and CO(2) from the paper laminate. In the second step, between 270 and 370 degrees C, the fire retardant decomposed, releasing HBr and brominated aromatics. In the third step, at temperatures above 370 degrees C, the phenol resin decomposed and char was formed. Compared to pure TBBA, which mainly produces brominated phenols, the brominated products enclosed in the char released HBr during the last degradation step as well as during the second step. Most of the bromine left the resin in the form of HBr, with about 14% of the bromine being fixed in brominated aromatics and less than 2% remaining in the residue.     

Spatio-temporal assessment and trend analysis of surface water salinity in the coastal region of Bangladesh

The study was designed to collect water samples over two seasons—wet-monsoon season (n = 96) (March–April) and dry-monsoon season (n = 44) (September–October)—to understand the seasonal variation in anion and cation hydrochemistry of the coastal rivers and estuaries contributing in the spatial trend in salinity. Hydrochemical examination of wet-monsoon season primarily revealed Ca–Mg–HCO₃ type (66%) and followed by Na–Cl type (17.70%) water. In the dry-monsoon season, the scenario reversed with primary water being Na–Cl type (52.27%) followed by Ca–Mg–HCO₃ type (31.81%). Analysis of Cl/Br molar ratio vs. Cl (mg/L) depicted sampling area affected by seawater intrusion (SWI). Spatial analysis by ordinary kriging method confirmed approximately 77% sample in the dry-monsoon, and 34% of the wet-monsoon season had shown SWI. The most saline-intruded areas in the wet-monsoon seasons were extreme south-west coastal zone of Bangladesh, lower Meghna River floodplain and Meghna estuarine floodplain and south-eastern part of Chittagong coastal plains containing the districts of Chittagong and Cox’s Bazar adjacent to Bay of Bengal. In addition, mid-south zone is also affected slightly in the dry-monsoon season. From the analyses of data, this study could further help to comprehend seasonal trends in the hydrochemistry and water quality of the coastal and estuarine rivers. In addition, it can help policy makers to obligate some important implications for the future initiatives taken for the management of land, water, fishery, agriculture and environment of coastal rivers and estuaries of Bangladesh.

     

Degradation of 1,4-dioxane in water with heat- and Fe2+-activated persulfate oxidation

This research investigated the 1,4-dioxane (1,4-D) degradation efficiency and rate during persulfate oxidation at different temperatures, with and without Fe²⁺ addition, also considering the effect of pH and persulfate concentration on the oxidation of 1,4-D. Degradation pathways for 1,4-D have also been proposed based on the decomposition intermediates and by-products. The results indicate that 1,4-D was completely degraded with heat-activated persulfate oxidation within 3–80 h. The kinetics of the 1,4-D degradation process fitted well to a pseudo-first-order reaction model. Temperature was identified as the most important factor influencing the 1,4-D degradation rate during the oxidation process. As the temperature increased from 40 to 60 °C, the degradation rate improved significantly. At 40 °C, the addition of Fe²⁺ also increased the 1,4-D degradation rate. Interestingly, at 50 and 60 °C, the 1,4-D degradation rate decreased slightly with the addition of Fe²⁺. This reduced degradation rate may be attributed to the rapid conversion of Fe²⁺ to Fe³⁺ and the production of an Fe(OH)₃ precipitate which limited the ultimate oxidizing capability of persulfate with Fe²⁺ under higher temperatures. Higher persulfate concentrations led to higher 1,4-D degradation rates, but pH adjustment had no significant effect on the 1,4-D degradation rate. The identification of intermediates and by-products in the aqueous and gas phases showed that acetaldehyde, acetic acid, glycolaldehyde, glycolic acid, carbon dioxide, and hydrogen ion were generated during the persulfate oxidation process. A carbon balance analysis showed that 96 and 93 % of the carbon from the 1,4-D degradation were recovered as by-products with and without Fe²⁺ addition, respectively. Overall, persulfate oxidation of 1,4-D is promising as an economical and highly efficient technology for treatment of 1,4-D-contaminated water.     

Lead immobilization in mechanochemical fly ash recycling

In previous studies, we focused on a mechanochemical process for recycling fly ash for use in cement; this process was expected to immobilize heavy metals in the fly ash, a desirable outcome in light of the fact that recycled fly ash is commonly used in the synthesis of inorganic materials. Here, we investigated the leaching of lead (Pb) from fly ash treated by a mechanochemical process and from cement prepared from the treated fly ash. We used lead oxide (PbO), a typical Pb compound in fly ash, as a model substance. Mechanochemical treatment of the fly ash inhibited Pb leaching by 93%, and further inhibition (more than 99.9%) was observed in cement produced from the treated fly ash. During the mechanochemical treatment, PbO was reduced to Pb by iron from the stainless-steel mill used for processing, and the lower solubility of Pb in water resulted in immobilization of the Pb.     

Determining storm sampling requirements for improving precision of annual load estimates of nutrients from a small forested watershed

This study sought to determine the lowest number of storm events required for adequate estimation of annual nutrient loads from a forested watershed using the regression equation between cumulative load (∑L) and cumulative stream discharge (∑Q). Hydrological surveys were conducted for 4 years, and stream water was sampled sequentially at 15-60-min intervals during 24 h in 20 events, as well as weekly in a small forested watershed. The bootstrap sampling technique was used to determine the regression (∑L-∑Q) equations of dissolved nitrogen (DN) and phosphorus (DP), particulate nitrogen (PN) and phosphorus (PP), dissolved inorganic nitrogen (DIN), and suspended solid (SS) for each dataset of ∑L and ∑Q. For dissolved nutrients (DN, DP, DIN), the coefficient of variance (CV) in 100 replicates of 4-year average annual load estimates was below 20% with datasets composed of five storm events. For particulate nutrients (PN, PP, SS), the CV exceeded 20%, even with datasets composed of more than ten storm events. The differences in the number of storm events required for precise load estimates between dissolved and particulate nutrients were attributed to the goodness of fit of the ∑L-∑Q equations. Bootstrap simulation based on flow-stratified sampling resulted in fewer storm events than the simulation based on random sampling and showed that only three storm events were required to give a CV below 20% for dissolved nutrients. These results indicate that a sampling design considering discharge levels reduces the frequency of laborious chemical analyses of water samples required throughout the year.