Maternal transfer of organochlorine pesticides, polychlorinated dibenzo-p-dioxins, dibenzofurans, and coplanar polychlorinated biphenyls in frogs to their eggs

Previous study confirmed that there were sexual differences in concentrations of organochlorine pesticides and dioxins in frogs during the breeding season. The present study utilized the egg masses from the previous study to determine the cause(s) of the sexual differences. When concentrations of the detected chemicals were compared between the female frogs and their eggs, it was found that the concentrations in the eggs were several times those in their mothers. The results indicated that maternal transfer reduced tissue concentrations in females. Since the weight of each egg mass was half that of the mother, two-thirds of the chemicals in a female frog were transferred to its eggs. In addition, the degree of maternal transfer differed among compounds. Maternal transfer of PCDDs and PCDFs with four or five chlorine atoms and coplanar PCBs followed the fugacity model. However, maternal transfer decreased for PCDDs/DFs with six or more chlorines as the octanol-water partition coefficient increased. From these results, maternal transfer was confirmed as the cause of sexual differences in concentrations of organochlorine pesticides and dioxins in adult frogs during the breeding season.     

Groundwater-soil-crop relationship with respect to arsenic contamination in farming villages of Bangladesh--a preliminary study

To clarify the groundwater-soil-crop relationship with respect to arsenic (As) contamination, As concentration was measured in tubewell (TW) water, surface soil from farmyards and paddy fields, and fresh taro (Colocasia esculenta) leaves from farmyards in the farming villages of Bangladesh. The As concentration in TW water from farmyards was at least four times higher than the Bangladesh drinking water standard, and the concentration in fresh taro leaves was equal to or higher than those reported previously for leafy vegetables in Bangladesh. As concentration of surface soils in both farmyards and paddy fields was positively correlated with that of the TW water. Further, the concentration in surface soil was positively correlated with levels in fresh taro leaves in the farmyard. This study, therefore, clarified the groundwater-soil-crop relationship in farmyards and the relationship between groundwater-soil in paddy fields to assess the extent of As contamination in Bangladeshi villages.     

Effects of amine, amine salt and amide on the behaviour of carbon dioxide absorption into calcium hydroxide suspension to precipitate calcium carbonate

The amount of carbon dioxide （CO2） absorption and calcium ion （Ca^2＋） concentration besides the pH of aqueous solution were observed during the COz absorption to precipitate calcium carbonate （CaCO3） from calcium hydroxide （Ca（OH）2）. A reaction rate-limiting effect of an amount of CO2 absorption without any organic additives in the early stage of the precipitation was observed, which was attributed to an interruption effect of bicarbonate ion （HCO3） on the precipitation of CaCO3. The improvement for the reaction rate was achieved not only by amine additives but also by neutral additives such as ε-caprolactam or amine salt. When the hexamethylene diamine was dissolved in the solution, successive change of crystal forms of CaCO3 aragonite to calcite in aqueous suspensions, confirmed by Ca^2＋ concentration change and X-ray diffraction, was concluded that a local environment around the amine group in aqueous solution and an interaction of the diamine with precipitated CaCO3 particles were important factors for these reactions.     

The cost of stratospheric climate engineering revisited

Stratospheric aerosol injection (SAI) has been receiving increasing attention as a possible option for climate engineering. Its direct cost is perceived to be low, which has implications for international governance of this emerging technology. Here, we critically synthesize previous estimates of the underlying parameters and examine the total costs of SAI. It is evident that there have been inconsistencies in some assumptions and the application of overly optimistic parameter values in previous studies, which have led to an overall underestimation of the cost of aircraft-based SAI with sulfate aerosols. The annual cost of SAI to achieve cooling of 2 W/m² could reach US$10 billion with newly designed aircraft, which contrasts with the oft-quoted estimate of “a few billion dollars.” If existing aircraft were used, the cost would be expected to increase further. An SAI operation would be a large-scale engineering undertaking, possibly requiring a fleet of approximately 1,000 aircraft, because of the required high altitude of the injection. Therefore, because of its significance, a more thorough investigation of the engineering aspects of SAI and the associated uncertainties is warranted.     

酸化水体中的浮游生物及其与主要化学因子的关系

１９９１－１９９２年对重庆市郊若干酸化水体的生物待正与理化参数进行综合研究的结果表明，藻类的种类数、细胞密度、生物量和叶绿素ａ含量以及浮游动物的种类数等均与呈正相关，但与Ｈ＋和总Ａｌ浓度呈负相关。浮游动物的个体密度在酸化水体中明显下降，但是鱼的捕食作用掩盖了其与上述化学参数之间的相关性。水体中Ｈ＋和总Ａｌ浓度的增加在很大程度上对浮游生物产生了不利影响，水体的透明度、总Ａｌ．ＴＰ和ＳＯ与ｐＨ的相关性十分明显，ｒ值分别为－０．６３７５、－０．６８６８、０．７５６１和０．７３２３。