Effect of cadmium on nodulation and N2-fixation of soybean in contaminated soils

The effects of cadmium stress on nodulation, N2-fixation capabilities of the root nodule, the change in ultrastructure of the root nodule, soybean growth, and the distribution of cadmium in plants were studied. The results obtained show that the nodulation of soybean roots was greatly inhibited by the addition of Cd, especially at the addition level of 10 and 20 mg kg(-1) soil. The inhibition of plant growth, especially the root growth, increased as the cadmium concentration increased, with deleterious effects observed for the roots. The weight ratio of soybean root/leaf decreased as the Cd concentration increased, which might explain the reason for nodulation decreases. The results also indicate that N2-fixation of root nodule was stimulated to some extent at the low levels of Cd addition, but decreased sharply with further increase of the Cd concentration. High Cd levels were also associated with changes in the ultrastructure of root nodule, in which the effective N2-fixing area was reduced and the N2-fixing cells in the area also reduced. In addition, the results also reveal that the content of Cd in different parts of the plants was as follows: roots > stems > seeds, indicating that the accumulation of Cd by roots is much larger than that by any other part of the soybean plant, and might cause deleterious effects to root systems.     

Livelihood vulnerability approach to assessing climate change impacts on mixed agro-livestock smallholders around the Gandaki River Basin in Nepal

Climate change vulnerability depends upon various factors and differs between places, sectors and communities. People in developing countries whose subsistence livelihood depends mainly upon agriculture and livestock production are identified as particularly vulnerable. Nepal, where the majority of people are in a mixed agro-livestock system, is identified as the world’s fourth most vulnerable country to climate change. However, there is limited knowledge on how vulnerable mixed agro-livestock smallholders are and how their vulnerability differs across different ecological regions in Nepal. This study aims to test two vulnerability assessment indices, livelihood vulnerability index and IPCC vulnerability index, around the Gandaki River Basin of central Nepal. A total of 543 households practicing mixed agro-livestock were surveyed from three districts, namely Dhading, Syangja and Kapilvastu representing three major ecological zones: mountain, mid-hill and Terai (lowland). Data on socio-demographics, livelihood determinants, social networks, health, food and water security, natural disasters and climate variability were collected and combined into the indices. Both indices differed for mixed agro-livestock smallholders across the three districts, with Dhading scoring as the most vulnerable and Syangja the least. Substantial variation across the districts was observed in components, sub-components and three dimensions (exposure, sensitivity and adaptive capacity) of vulnerability. The findings help in designing site-specific intervention strategies to reduce vulnerability of mixed agro-livestock smallholders to climate change.     

Organically bound tritium (OBT) for various plants in the vicinity of a continuous atmospheric tritium release

In order to quantify tritium impact on the environmental, we studied vegetation continuously exposed to a tritiated atmosphere. We chose lichens as bio-indicators, trees for determination of past tritium releases of the Valduc Centre, and lettuce as edible vegetables for dose calculation regarding neighbourhood. The Pasquill and Doury models from the literature were tested to estimate tritium concentration in the air around vegetable for distance from the release point less than 500m. The results in tree rings show that organically bound tritium (OBT) concentration was strongly correlated with tritium releases. Using the GASCON model, the modelled variation of OBT concentration with distance was correlated with the measurements. Although lichens are recognized as bio-indicators, our experiments show that they were not convenient for environmental surveys because their age is not definitive. Thus, tritium integration time cannot be precisely determined. Furthermore, their biological metabolism is not well known and tritium concentration appears to be largely dependent on species. An average conversion rate of HTO to OBT was determined for lettuce of about 0.20-0.24%h(-1). Nevertheless, even if it is equivalent to values already published in the literature for other vegetation, we have shown that this conversion rate, established by weekly samples, varies by a factor of 10 during the different stages of lettuce development, and that its variation is linked to the biomass derivative.     

Radionuclide transfer to fruits: A critical review. Foreword

After completion of the (Validation of Environmental Model Predictions) (VAMP) and (BIOspheric Model Validation Study) (BIOMOVS II) Programmes, the Division of Radiation and Waste Safety of the IAEA decided to promote a new co-ordinated research programme to continue activities in the area of biosphere modelling. As a result, the BIOMASS Programme on BIOsphere Modelling and ASSessment was launched in Vienna in October 1996. The Programme is scheduled to finish in October 2000. The overall objective of BIOMASS is to provide an international focal point in the area of biosphere assessment modelling. There are 3 Themes and 11 working groups in BIOMASS. The objective of the Theme 3 Fruits Working Group is to improve understanding of the uptake and transfer of radionuclides from different sources to fruit. As part of the work programme, a review was undertaken of the experimental, field and modelling information on the transfer of radionuclides to fruit.     

Seasonal variations of Rn concentrations in the air of a tunnel located in Nagano city

The seasonal variation of 222Rn concentrations in the air of tunnels constructed during World War II at Nagano City has been investigated. The determination of 222Rn concentrations in tunnel air was performed using a solid-state nuclear track detector technique. The monthly radon concentrations changed smoothly, decreasing towards winter and increasing towards summer, and it was found that the concentrations strongly correlate with the temperature difference between the inside and the outside of the tunnel. In the innermost areas of the tunnel, the maximum concentration was observed in July, its value being about 6500 Bq m (-3). The concentrations of radon in the tunnel air decrease exponentially towards the openings of the tunnel, which indicates that the radon concentration in the tunnel is basically governed by diffusion and mixing of radon gas with air. These observations lead to the conclusion that the seasonal variation of the radon concentration in the tunnel air is mainly caused by a convection current due to a stack effect induced by the temperature difference between the tunnel air and the outside air.     

Radioactivity and heavy metal composition of Nigerian phosphate rocks: possible environmental implications

Phosphate rock samples collected from the Dange Formation within the Sokoto basin were analyzed for trace element constituents using instrumental neutron activation analysis (INAA) and X-ray fluorescence analysis (XRFA) techniques, while natural activity concentrations due to 235U, 232Th, and 40K were determined by gamma-ray spectrometry. The analytical results show that the average concentrations of some toxic elements (As, Sb, Cr, and Zn) in phosphate rocks are not appreciably different from that in agricultural soils. However the U and Th contents are enriched significantly in comparison. The results were used to assess the environmental toxicity of heavy metals and radiation hazard attributable to the direct application of phosphate rock as fertilizer.     

用脉冲电旋风除尘器处理催化剂厂分子筛尾气

介绍了脉冲电旋风除尘器的工作原理及用其处理催化剂分子筛尾气的试验情况。试验结果表明,分子筛尾气很适合脉冲电旋风除尘处理,除尘效果较好,在进气含尘质量浓度为1324．9mg／m^3时,除尘效率达89．4％左右,粉尘驱进速度达0．15～0．17m／s,比常规电除尘技术提高1倍左右。     

Proposal for the integration of decentralised composting of the organic fraction of municipal solid waste into the waste management system of Cuba

Municipal solid waste (MSW) generation and management in Cuba was studied with a view to integrating composting of the organic fractions of MSW into the system. Composting is already included as part of the environmental strategy of the country as an appropriate waste management solution. However, no programme for area-wide implementation yet exists. The evaluation of studies carried out by some Cuban and international organisations showed that organic matter comprises approximately 60-70% of the MSW, with households being the main source. If all organic waste fractions were considered, the theoretical amount of organic waste produced would be approximately 1 Mio. Mg/a, leading to the production of approximately 0.5 Mio. Mg/a of compost. Composting could, therefore, be a suitable solution for treating the organic waste fractions of the MSW. Composting would best be carried out in decentralised systems, since transportation is a problem in Cuba. Furthermore, low technology and low budget composting options should be considered due to the problematic local economic situation. The location for such decentralised composting units would optimally be located at urban agricultural farms, which can be found all over Cuba. These farms are a unique model for sustainable farming in the world, and have a high demand for organic fertiliser. In this paper, options for the collection and impurity-separation in urban areas are discussed, and a stepwise introduction of source-separation, starting with hotel and restaurant waste, is suggested. For rural areas, the implementation of home composting is recommended.     

Durability of recycled aggregate concrete using pozzolanic materials

In this study, pulverized fuel ash (PFA) and ground granulated blast furnace slag (GGBS) were used to compensate for the loss of strength and durability of concrete containing recycled aggregate. As a result, 30% PFA and 65% GGBS concretes increased the compressive strength to the level of control specimens cast with natural granite gravel, but the tensile strength was still lowered at 28 days. Replacement with PFA and GGBS was effective in raising the resistance to chloride ion penetrability into the concrete body, measured by a rapid chloride ion penetration test based on ASTM C 1202-91. It was found that the corrosion rate of 30% PFA and 65% GGBS concretes was kept at a lower level after corrosion initiation, compared to the control specimens, presumably due to the restriction of oxygen and water access. However, it was less effective in increasing the chloride threshold level for steel corrosion. Hence, it is expected that the corrosion time for 30% PFA and 65% GGBS concrete containing recycled aggregate mostly equates to the corrosion-free life of control specimens.