A simple model for describing the concentration of 212Pb in the atmosphere

The implementation of the Comprehensive Test Ban Treaty is resulting in the construction of a world-wide system of 80 monitoring stations that will be able to detect air-borne radioactivity, not only from atomic bombs but also from other anthropogenic and natural sources. A prototype monitoring station has been operating since April 1996 in Vancouver, BC, Canada. This station provides daily reports of natural radioactivity, including 7Be and decay products of 220Rn (thoron). Data for 212Pb concentrations have been analyzed over a 6-month period. The concentration is reduced by rainfall, high wind velocity, and low temperatures and it also depends on the wind direction, but atmospheric inversions appeared to have little impact. We present a relatively simple model, which is easy to use and which offers predictive powers that can be applied to other similar environmental situations.     

Effects of the aflatoxins on ATPase activities in mouse and rat liver.

The effects of the aflatoxins on ATPase activities in mouse and rat tissues were investigated in vitro. The hepatic oligomycin-sensitive (O.S.) Mg++ ATPase was inhibited significantly. The order of inhibition was G1 greater than B1 greater than G2 greater than B2. Mouse O.S. Mg++ ATPase was more sensitive than the corresponding rat enzyme. The oligomycin-insensitive (O.I.) Mg++ ATPase activities in rat and mouse liver were not altered. Although aflatoxins G1 and B1 were more potent inhibitors of hepatic O.S. Mg++ ATPase, no concentration-response was observed, whereas aflatoxins G2 and B2 inhibited enzyme activity in a concentration-dependent manner. Spectral analysis of aflatoxin G1 solutions suggested that solubility was not related to the observed effects. In addition, the effects of aflatoxin B1 and G1 on mouse brain microsomal Na+-K+ ATPase were examined. Although aflatoxin B1 was more potent that G1, both mycotoxins significantly inhibited enzyme activity in a concentration-dependent fashion.     

Potential source of asbestos in non-asbestos textile manufacturing company

Recently, a worker with lung carcinoma and a metastatic brain tumor was diagnosed as having a work-related disease. He had been employed in a non-asbestos textile company for 25 years. Consequently, to identify and explore possible causative agents for lung cancer in a non-asbestos textile manufacturing company and establish a causal relationship between exposure and lung cancer, an epidemiological investigative study was conducted and the work processes the worker was engaged in were examined. Air samples were taken from the workplace and during the drilling processes, and a suspected causative material was analyzed. The study revealed that the subject had been employed in the non-asbestos textile manufacturing company for 25 years from 1973 and his responsibilities included repairing spinning machines. In particular, the subject was involved in drilling B-bushings that were used to protect against gear abrasion in the spinning machines. An analysis of the B-bushings using a transmission electron microscope equipped with an energy dispersive X-ray analyzer indicated that they contained crocidolite asbestos fibers. Air samples obtained when drilling the B-bushings clearly indicated that the subject had most likely been exposed to crocidolite fibers when installing the B-bushings in the spinning machines. The frequency and duration of the work suggested that there would be a sufficient degree of exposure to crocidolite fibers to cause lung cancer. Except for smoking and asbestos exposure, no other chemical exposure was suspected for developing lung cancer in the workplace. Smoking appeared to be more of a potentiating risk factor in conjunction with the asbestos exposure. Accordingly, this case may provide significant evidence in identifying the cause of the mesothelioma or lung carcinoma found among workers in non-asbestos textile manufacturing companies elsewhere.     

生物补救、植物工程与人工地下水补充:对发展中国家的潜在用途与技术转让问题

在工业化国家,已经证实了生物补救、植物工程与人工地下永补充的有效性.他们对发展中世界也有巨大的使用潜力.模拟自然的发育过程,它们提供了使环境可持续的解决办法.当这些和那些技术在发展中国家应用的时候,要根据当地的实际情况考虑社会、经济和环境条件.关于技术转让和能力建设的问题,也应该量力而行.     

Methane production from food waste leachate in laboratory-scale simulated landfill

Due to the prohibition of food waste landfilling in Korea from 2005 and the subsequent ban on the marine disposal of organic sludge, including leachate generated from food waste recycling facilities from 2012, it is urgent to develop an innovative and sustainable disposal strategy that is eco-friendly, yet economically beneficial. In this study, methane production from food waste leachate (FWL) in landfill sites with landfill gas recovery facilities was evaluated in simulated landfill reactors (lysimeters) for a period of 90 d with four different inoculum–substrate ratios (ISRs) on volatile solid (VS) basis. Simultaneous biochemical methane potential batch experiments were also conducted at the same ISRs for 30 d to compare CH₄ yield obtained from lysimeter studies. Under the experimental conditions, a maximum CH₄ yield of 0.272 and 0.294 L/g VS was obtained in the batch and lysimeter studies, respectively, at ISR of 1:1. The biodegradability of FWL in batch and lysimeter experiments at ISR of 1:1 was 64% and 69%, respectively. The calculated data using the modified Gompertz equation for the cumulative CH₄ production showed good agreement with the experimental result obtained from lysimeter study. Based on the results obtained from this study, field-scale pilot test is required to re-evaluate the existing sanitary landfills with efficient leachate collection and gas recovery facilities as engineered bioreactors to treat non-hazardous liquid organic wastes for energy recovery with optimum utilization of facilities.     

Growth and macronutrient removal of water hyacinth in a small secondary sewage treatment plant

Studies have been made of the growth characteristics of water hyacinth, Eichhornia crassipes (Mart.) Solms, and its ability to remove N, P and K, in a secondary settling pond of a small secondary sewage treatment plant serving both the academic and residential blocks of the Swire Marine Laboratory, University of Hong Kong. The treatment plant consists of, in series, a primary settling tank, a trickling filter compartment and a secondary settling pond from which part of the treated wastewater is recycled to the primary settling tank while the remaining effluent (1 to 2 m³ daily) mixes with and hence is diluted by the outflowing seawater from the aquarium system of the Swire Marine Laboratory before discharge to the sea. Samples of wastewater have been taken regularly from the primary sedimentation pond, the outflow of the trickling filter, the secondary settling pond and the effluent of the treatment plant (before mixing with aquarium outflow) since January, 1992. Physical, chemical and biological characteristics of the samples have been determined and are typical of secondary effluents, with a mean pH of about 7.5, total solids 1200 mg L⁻¹, suspended solids 45 mg L⁻¹, conductivity 2000 μS cm⁻¹, salinity 1 ppt, dissolved oxygen 2 mg L⁻¹, BOD₅ 45 mg L⁻¹, Kjeldahl-N 30 mg L⁻¹, NH₄,-N 25 mg L⁻¹, NO₃-N 4 mg L⁻¹, total P 10 mg L⁻¹, K 35 mg L⁻¹ and total coliforms of less than 10⁵ colonies 100 ml⁻¹.Water hyacinth plants have been stocked in the secondary settling pond as an integral part of the treatment plant so as to improve the quality of, as well as to retrieving and recycling nutrient elements from, the wastewater. The plants are periodically harvested to maintain an active growing crop. The growth rate, standing crop biomass, tissue nutrient composition, nutrient storage and accumulation rate of two growth cycles, one from February 25 to March 18 (mean temperature 17.6°C) and the other from 22 April to 12 May (24.8°C) are reported. The water hyacinth assumed a relatively high standing crop biomass of 10 kg m⁻² (5 to 6 t DM ha⁻¹), and growth rates of 48 and 225 g m⁻² day⁻¹, respectively, for the first and second growth period. Nutrient storage capacities were relatively high, at about 20, 7.5 and 16.5 g m⁻² for N, P and K, respectively. The nutrient composition was very high, reaching 5.42% for N, 1.97 for P, and 4.57 for K. Both the stem and lamina accumulated high levels of N, while the petiole had the highest level of P and K. Apart from nutrient removal, the water hyacinth also helped to decrease the suspended solids, BOD₅ value and total coliforms of the wastewater.It is concluded that water hyacinth improves the quality of wastewater in such small-scale sewage treatment plants and it is recommended that frequent harvests of water hyacinth would increase the treatment efficiency, especially during the active growing season with high temperatures coupled with intense solar radiation.     

Eco-health evaluation for the Shanghai metropolitan area during the recent industrial transformation (1990-2003)

Shanghai is a cosmopolitan city and one of the most important economic centers in China, but is saddled with serious environmental problems resulting from a recent industrial transformation. This paper examines the interactive relationships between economic growth, eco-efficiency of urban metabolism, and environmental performance of the Shanghai metropolitan area since the 1990s using 15 indicators. This study has revealed an enhanced eco-efficiency of water and energy use as well as an improved overall environmental quality in the central urban districts of Shanghai. Both TGDP (total GDP) and GDP per capita increased rapidly at the annual rate of 16.28% and 15.91%, respectively. In contrast, energy consumed per 10000RMB YUAN GDP (ECG), water consumed per 10000RMB YUAN GDP (WCG), wastewater discharged per 10000RMB YUAN GDP (WWDG), and waste gases emitted per 10000RMB YUAN GDP (WGEG) decreased at the annual rate of 9.34%, 10.69%, 14.57%, and 8.52%, respectively. The rapid decline in ECG, WCG, WWDG, and WGEG indicates an enhanced eco-efficiency of urban metabolism. However, uncontrolled emission of wastes from domestic instead of industrial sources adversely affected the overall environmental quality. In addition, suburban areas have undergone rapid economic growth at the cost of human health deterioration, as measured by mortalities and relative mortality ratios of three major diseases (tumor, respiratory disease, and trauma/toxicosis). With Shanghai serving as the "locomotive" driving the economy of the Yangtze River Basin, effective pollution control policies and a network of regional coordination are urgently needed in the globalization and ecological security of the entire area.     

Effects of Temperature and Relative Humidity on Polylactic Acid Plastic Degradation

Three high molecular weight (120,000 to 200,000 g mol^–1) polylactic acid (PLA) plastic films from Chronopol (Ch-I) and Cargill Dow Polymers (GII and Ca-I) were analyzed for their degradation under various temperature and relative humidity (RH) conditions. Two sets of plastic films, each containing 11 samples, were randomly hung in a temperature/humidity-controlled chamber by means of plastic-coated paper clips. The tested conditions were 28, 40, and 55°C at 50 and 100% RH, respectively, and 55°C at 10% RH. The three tested PLA films started to lose their tensile properties when their weight-average molecular weight (M _w) was in the range of 50,000 to 75,000 g mol^–1. The average degradation rate of Ch-I, GII, and Ca-I was 28,931, 27,361, and 63,025 M _w/week, respectively. Hence, GII had a faster degradation rate than Ch-I and Ca-I under all tested conditions. The degradation rate of PLA plastics was enhanced by the increase in temperature and relative humidity. This trend was observed in all three PLA plastics (Ca-I, GII, and Ch-I). Of the three tested films, Ch-I was the first to lose its mechanical properties, whereas Ca-I demonstrated the slowest loss, with mechanical properties under all tested conditions.     

Local authority waste paper recovery operations: An appropriate costing system

This article reviews attempts by other workers to derive full economic evaluations of local authority waste paper recovery operations and proposals from government bodies to devise uniform costing systems for these schemes. In the light of this work a standard costing system for local authority waste paper recovery operations is proposed. Empirical data was obtained from a number of local authorities and analysed using this standard costing system. The viability of each scheme under the standard costing system and the Council's original costing system is compared.