Development of a catalytic cracking process for converting waste plastics to petrochemicals

The catalytic degradation of polyolefin using H-gallosilicates was examined using a bench-scale reactor (0.8kg/h) with semicontinuous feeding and the following plastics: (1) low-density polyethylene (LDPE) pellets; (2) linear low-density polyethylene (L-LDPE) pellets; (3) high-density polyethylene (HDPE) pellets; (4) polypropylene (PP) pellets; (5) polyolefin obtained from pulverized industrial waste plastics. The yields of liquid compounds from these materials, which were aromatics in most cases, ranged from 55wt% to 68wt%. With an increase in the ratio of total reactant to catalyst, the liquid yield remained the same. Yields of benzene, toluene, and xylenes (BTXs) decreased rapidly to below 50wt% at a ratio of more than 30. Differences in this ratio for BTXs were always small and were independent of the material. Only about half of the gas product was propane with a fresh catalyst. When the experiments were repeated, propylene, isobutane, and isobutene were found to increase.     

Urinary 8-hydroxy-2'-deoxyguanosine in inhabitants chronically exposed to arsenic in groundwater in Cambodia

Arsenic concentrations in hair and urine, and urinary levels of 8-hydroxy-2'-deoxyguanosine (8-OHdG), a marker of oxidative DNA damage, were examined for inhabitants of the Mekong Basin in Kratie Province, Cambodia. Also, the arsenic levels of tube-well water were determined. Total arsenic concentrations in tube-well water ranged from <1 to 886 microg L(-1), and 44.8% of these exceeded the WHO drinking water guideline of 10 microg L(-1). Elevated levels of arsenic were observed in the human hair and urine, and also a significant positive correlation was observed between the concentrations in hair and urine. These results suggest that the inhabitants are chronically exposed to arsenic through drinking the tube-well water. Levels of urinary 8-OHdG were higher for the subjects with higher arsenic levels in hair and urine, suggesting that induction of oxidative DNA damage was caused by chronic exposure to arsenic in tube-well water for the inhabitants in Kratie Province. To our knowledge, this is the first report on the oxidative DNA damage caused by chronic exposure to arsenic in groundwater for the inhabitants in Cambodia.     

Trichloroethylene decomposition and in-situ dry sorption of Cl-products by calcium oxides prepared from hydrated limes

A comparison of CaOs produced by calcining two types of hydrated lime and calcium carbonate was made for decomposition of trichloroethylene and in-situ dry sorption of the decomposed Cl-products using a lab-scale gas flow type tubular packed bed reactor. About 20 mg of CaO sample was mixed with about 2 g of Al₂O₃ particles and packed in the reactor and allowed to react with a flowing standard gas containing 500 ppm of C₂HCl₃ (N₂ balance) at 673 and 873 K, under the condition that the reaction of CaO with C₂HCl₃ might be completed within a few hours.It was found that no thermal decomposition of C₂HCl₃ at or below 673 K was observed in a reactor packed only with Al₂O₃ particles. However, a considerable amount of decomposition of C₂HCl₃ was obtained in a reactor packed with CaO and Al₂O₃, even at 673 K. For 1 mol of CaO prepared by calcining highly reactive Ca(OH)₂ at 673 K, decomposition of 0.42 mol of C₂HCl₃ and in-situ absorption product of 0.53 mol of CaCl₂ were obtained. At 873 K, about 46% of C₂HCl₃ was thermally decomposed. The total amount of C₂HCl₃ decomposed in CaO-Al₂O₃ particle bed at 873 K became nearly twice larger than that at 673 K. For 1 mol of CaO prepared by calcining highly reactive Ca(OH)₂ at 873 K, decomposition of 0.59 mol of C₂HCl₃ and in-situ absorption product of 0.67 mol of CaCl₂ were obtained. Small amounts of C₂Cl₂, C₂Cl₄, CCl₄, etc. were detected during decomposition of C₂HCl₃ at 673 and 873 K.It was recognized that the data on decomposition of C₂HCl₃ as well as in-situ dry sorption of Cl-products in CaO particle bed were correlated with specific surface area of the CaO employed.     

Contamination by arsenic and other trace elements in tube-well water and its risk assessment to humans in Hanoi, Vietnam

Concentrations of As and other trace elements and their association were examined in groundwater (n = 25) and human hair (n = 59) collected at Gia Lam District and Thanh Tri District, suburban areas of Hanoi, Vietnam, in September 2001. Concentrations of As in the groundwater ranged from <0.10 to 330 microg/l, with about 40% of these exceeding WHO drinking water guideline of 10 microg/l. Also, 76% and 12% of groundwater samples had higher concentrations of Mn and Ba than WHO drinking water guidelines, respectively. Arsenic concentrations in hair of residents in Gia Lam and Thanh Tri Districts (range 0.088-2.77 microg/g dry wt.) were lower than those in other As-contaminated areas of the world, but were higher than those of people in non-contaminated areas. Concentrations of As and Mn in hair of some individuals from the Gia Lam and Thanh Tri Districts exceeded the level associated with their toxicity and, therefore, a potential health risk of As and Mn is a concern for the people consuming the contaminated water in this area. Cumulative As exposure was estimated to be lower than the threshold levels at the present, which might explain the absence of manifestations of chronic As poisoning and arsenicosis in the residents of Gia Lam and Thanh Tri Districts. To our knowledge, this study revealed for the first time that the residents are exposed not only to As but also Mn and Ba from groundwater in the Red River Delta, Vietnam.     

TURBULENCE MEASUREMENT OF A FLOW WITH SUSPENDED SOLID PARTICLES1

ABSTRACT: Success in measuring turbulence in water has been achieved by replacing the hot-wire probe by the hot-film probe. Accordingly, these results have greatly increased knowledge and understanding of hydromechanics. However, there are few published measurements of turbulent properties of flow with suspended solid particles. With this in mind, the authors conducted measurements of turbulent properties of flow with suspended solid particles by using a quartz-coated, wedge-shaped hot-film probe. Turbulent intensities and macroscale of eddy change in the flow with suspended solid particles on a movable bed is discussed.     

A study on the Spatial Distribution of Nitrogen and Phosphorus Balance, and Regional Nitrogen Flow Through Crop Production

The spatial distribution patterns of the nitrogen and phosphorus input/intake amounts in crop production within two small basins are examined, based upon a cropping unit distribution map that is obtained from remote sensing data analysis. Firstly, we examine the availability and suitability of approaches to the spatial distribution analysis of cultivation patterns classified from material flow characteristics of crop production using seasonal remote-sensing data. Secondly, material flow units in crop production are grouped according to the cultivation patterns obtained from the remote-sensing data analysis. Consequently, the spatial patterns of the amounts of both nitrogen and phosphorus inputs/intakes through crop production on farmland are examined and their spatial distribution maps are prepared according to the material flow units. In addition, we developed a nitrogen flow and runoff model and the model is simulated based on the examination of the results of spatial distribution patterns of the material flow units. The annual nitrogen runoff from small catchments, where various crops are cultivated, varies from 2.7 kg ha^–1 year^–1 to 108 kg ha^–1 year^–1 and the annual balanced losses of nitrogen in small catchments varied from –30 kg ha^–1 year^–1 to 101 kg ha^–1 year^–1. Also, the monthly changes in soil nitrogen of each material flow unit is estimated at –55 kg ha^–1 as a maximum decrease and 114 kg ha^–1 as a maximum increase. These results indicate that the spatial distribution patterns of nutrient input and intake through agricultural activities should be considered when analyzing the material flows and nutritient movement in soil–water systems in rural areas for watershed environmental control and regional agricultural management.     

Effect of acute nitrogen dioxide exposure on the composition of fatty acid associated with phospholipids in alveolar lavage

In vivo exposure of rats to 10 ppm nitrogen dioxide (NO₂) for 12h caused changes in fatty acids composition of alveolar lavage phospholipids. Among the fatty acid species, the relative ratio of palmitic acid, myristic acid and palmitoleic acid increased significantly. While the relative ratio of stearic acid, oleic acid, linoleic acid and arachidonic acid decreased significantly. Both the increase in the incorporation of palmitic acid in phosphatidylcholine which would be released into the alveoli and the increase in the release of phosphatidylcholine into the alveoli may account for the changes in the fatty acid composition of the present findings.     

Field survey of a sustainable sanitation system in a residential house

Sustainable sanitation is an approach for more ecological and sustainable water resources management. In this paper, we proposed one of the new integrated waste treatment systems： an ＂sustainable sanitation system＂ that includes separation of the black water from water system by a non-flushing toilet （bio-toilet）, and a gray water treatment based on a biological and ecological concept. Sustainable sanitation system also converts the domestic waste to soil conditioners and fertilizers, for farmland use. As one of the case studies, Environmentally Symbiotic Housing in which people actually live using the bio-toilet for the black water treatment and the household wastewater treatment facility for the gray water was introduced. The availability of this system was investigated by analyzing the sawdust used in the bio-toilet and the quality of the effluent in the household wastewater treatment facility. As the result, the water content of the sawdust did not exceed 60% in any of the sampling points and the BOD and COD of the effluent of the household wastewater treatment facility were below 10 and 20 mg/L respectively, due to the low loading. Compared to the pollution load on the water environment created by the conventional system, it was found that the effluent of the house has a lower load than the tertiary treatment and the volume of the water consumption is 75% of the conventional system.     

Land-Cover Changes and Its Impacts on Ecological Variables in the Headwaters Area of the Yangtze River, China

Land cover changes affect ecological landscape spatial pattern, and evolving landscape patterns inevitably cause an evolution in ecosystem functionality. Various ecological landscape variables, such as biological productivity (plant biomass and stock capacity), soil nutrients (organic matter and N content) and water source conservation capacity are identified as landscape function characteristics. A quantitative method and digital model for analyzing evolving landscape functionality in the headwaters areas of the Yangtze River, China were devised. In the period 1986–2000, patch transitions of the region's evolving landscapes have been predominantly characterized by alpine cold swamp meadow, with the highest coverage tending to be steppified meadow or steppe, and desertification landscape such as sand and bare rock land expansion. As the result of such changes, alpine swamp areas decreased by 3.08 × 10³ km² and the alpine cold sparse steppe and bare rock and soil land increased by 6.48 × 10³ km² and 5.82 × 10³ km², respectively. Consequently, the grass biomass production decreased by 2627.15 Gg, of which alpine cold swamp meadows accounted for 55.9% of this loss. The overall stock capacity of the headwaters area of the Yangtze River decreased by 920.64 thousand sheep units, of which 502.02 thousand sheep units decreased in ACS (Alpine cold swamp) meadow transition. Soil organic matter and N contents decreased significantly in most alpine cold meadow and swamp meadow landscape patches. From 1986 to 2000 the total losses of soil organic matter and total N in the entire headwaters region amounted to 150.2 Gkg and 7.67 Gkg. Meanwhile, the landscape soil water capacity declined by 935.9 Mm³, of which 83.9% occurred in the ACS meadow transition. In the headwater area of the Yangtze River, the complex transition of landscape resulted in sharp eco-environmental deterioration. The main indication for these changes involved the intensity of the climate in this region is becoming drier and warmer, resulting in a gradual degradation of the permafrost.     

Specific accumulation of arsenic compounds in green turtles (Chelonia mydas) and hawksbill turtles (Eretmochelys imbricata) from Ishigaki Island, Japan

Concentrations of total arsenic (As) and individual compounds were determined in green and hawksbill turtles from Ishigaki Island, Japan. In both species, total As concentrations were highest in muscle among the tissues. Arsenobetaine was a major compound in most tissues of both turtles. High concentrations of trimethylarsine oxide were detected in hawksbill turtles. A significant negative correlation between standard carapace length (SCL), an indicator of age, and total As levels in green turtles was found. In contrast, the levels increased with SCL of hawksbill turtles. Shifts in feeding habitats with growth may account for such a growth-dependent accumulation of As. Although concentrations of As in marine sponges, the major food of hawksbill turtles are not high compared to those in algae eaten by green turtles, As concentrations in hawksbill turtles were higher than those in green turtles, indicating that hawksbill turtles may have a specific accumulation mechanism for As.