Dietary exposure of juvenile common sole (Solea solea L.) to polybrominated diphenyl ethers (PBDEs): Part 1. Bioaccumulation and elimination kinetics of individual congeners and their debrominated metabolites

The uptake and elimination of six PBDE congeners (BDE-28, -47, -99, -100, -153, -209) were studied in juvenile common sole (Solea solea L.) exposed to spiked contaminated food over a three-month period, then depurated over a five-month period. The results show that all of the studied PBDEs accumulate in fish tissues, including the higher brominated congener BDE-209. Several additional PBDE congeners were identified in the tissues of exposed fish, revealing PBDE transformation, mainly via debromination. The identified congeners originating from PBDE debromination include BDE-49 and BDE-202 and a series of unidentified tetra-, penta-, and hepta- BDEs. Contaminant assimilation efficiencies (AEs) were related to their hydrophobicity (log K_ow) and influenced by PBDE biotransformation. Metabolism via debromination appears to be a major degradation route of PBDEs in juvenile sole in comparison to biotransformation into hydroxylated metabolites.     

Uptake, tissue distribution and metabolism of the insecticide endosulfan in Jenynsia multidentata (Anablepidae, Cyprinodontiformes)

The study reports the accumulation, distribution and metabolism of technical endosulfan in Jenynsia multidentata. Adult females were exposed to acute sublethal concentrations (0.072, 0.288 and 1.4 μg L⁻¹). After 24 h, fish were sacrificed and gills, liver, brain, intestine and muscle were removed. Results show that both isomers of technical-grade endosulfan (α- and β-) are accumulated in fish tissues and biotransformation to endosulfan sulfate occurs at all concentrations tested. Significantly differences in endosulfan accumulation were only found at 1.4 μg L⁻¹ but not between the lowest concentrations. However a similar distribution pattern was observed at all exposure levels where liver, intestine and brain had the highest levels of α-, β-endosulfan and endosulfan sulfate. Moreover, liver and brain showed the highest endosulfan sulfate:α-endosulfan ratios due to high biotransfomation capacity. J. multidentata demonstrated to be a sensitive species under exposure to technical endosulfan and, therefore, could be used to assess aquatic pollution.     

农民非农收入与农村土地流转关系的协整分析——以江苏省南京市为例

农村土地流转是提高土地利用率、实现土地规模化、加快农村剩余劳动力转移的重要方式.尤其是在党的十七届三中全会<决定>中明确提出要加快农村土地流转,发展适度规模经营.而农地流转能否增加农民非农收入、缩小收入差距是农地流转过程中必须回答的现实问题.本文以江苏省南京市调查数据为例,采用协整方法对农民非农收入影响农地流转的长期均衡关系及其作用机制进行了探讨.研究结果表明:农民非农收入与农地流转之间存在着长期均衡关系,但短期却存在波动.同时,农民非农收入水平与农地流转之间存在着双向因果关系,而且早期农地流转对农民非农收入的影响程度较弱.在此基础上,本文从加快发展非农产业,提供农民非农收入水平;大力发展农村职业教育,提高农民文化水平与素质;培育完善农地流转和农村劳动力就业市场等方面提出了对策建议.     

Dietary exposure of rainbow trout to 8:2 and 10:2 fluorotelomer alcohols and perfluorooctanesulfonamide: Uptake, transformation and elimination

The bioaccumulation of perfluorooctanesulfonamide (PFOSA) and two fluorotelomer alcohols (8:2 FTOH, 10:2 FTOH) by rainbow trout (Oncorhynchus mykiss) through dietary exposure, including depuration rates and metabolism was investigated. Concentrations in the spiked feed ranged from 10.9 μg g⁻¹ wet weight (wet wt) for PFOSA and 6.7 μg g⁻¹ wet wt for 8:2 FTOH to 5.0 μg g⁻¹ wet wt for 10:2 FTOH. Trout was fed at 1.5% body weight per day for 30 d and depuration was followed for up to 30 d following previously published dietary exposure protocols. Perfluorooctanesulfonate (PFOS) was the major perfluoroalkylsulfonate (PFSA) detected in fish following dietary exposure to PFOSA. Half-lives of PFOS and PFOSA were 16.9 ± 2.5 and 6.0 ± 0.4 d, respectively. A biomagnification factor (BMF) of 0.023 was calculated for PFOSA which indicates that dietary exposure to PFOSA does not result in biomagnification in the rainbow trout. PFOS had a BMF of 0.08. The fluorotelomer saturated acids (8:2 FTCA, 10:2 FTCA) and fluorotelomer unsaturated acids (8:2 FTUCA, 10:2 FTUCA) were the major products detected in rainbow trout following dietary exposure to 8:2 FTOH and 10:2 FTOH, respectively. Half-lives were 3.7 ± 0.4, 2.1 ± 0.5, 3.3, and 1.3 d for 10:2 FTCA, 10:2 FTUCA, 8:2 FTCA, and 8:2 FTUCA, respectively. Small amounts of perfluorooctanoate (PFOA) and perfluorodecanoate (PFDA) were also detected in the FTOH exposed fish.     

中国经济增长与耕地资源数量变化阶段性特征研究——协整分析及Granger因果检验

利用Eviews 6.0软件,基于协整分析与Granger因果关系检验方法,探讨经济增长和耕地资源数量变化的相互关系和相互作用,以协调耕地保护和经济发展的矛盾。研究结果表明,不同经济增长阶段,我国耕地资源数量变化与经济增长存在长期均衡关系;自1952年以来,我国经济增长和耕地资源数量变化经历了3个阶段,具体表现为:(1)互为因果(1952～1978年),这一阶段农业在国民经济中具有重要地位,耕地的产出在经济增长中占据较大的份额;(2)前者是后者的Granger原因(1978～1992年),此阶段耕地资源投入量顺应了经济增长的要求,发挥了自己应有的作用;(3)后者是前者的Granger原因(1992～2008年),耕地资源作为要素投入支撑了经济的低质量增长,由此产生了重复建设、土地低效利用等问题。因此,关注经济增长和耕地资源数量变化在不同经济发展阶段的均衡关系,发现其中的规律,掌握其中的因果变化趋势,适时调整土地政策以适应经济增长的要求是亟待解决的战略问题。     

中国城镇化与土地集约利用关系的动态计量分析

在测度城镇化与土地集约利用的基础上,运用动态计量经济模型探讨城镇化与土地集约利用的相互作用。研究结果表明：（1）城镇化与土地集约利用均为一阶单整序列;（2）城镇化与土地集约利用之间存在长期均衡关系,但短期内却存在失衡,短期波动向长期均衡趋近的调整幅度达到18.98%;（3）城镇化是土地集约利用的Granger原因,而反向关系得不到实证支持;（4）土地集约利用对来自城镇化的冲击响应强烈,城镇化的冲击对土地集约利用的解释水平达到了90%,而城镇化对来自土地集约利用的冲击响应较弱,土地集约利用的冲击对城镇化的解释水平仅为3%。因此,应采取长期而非短期的策略,有序推进城镇化进程,加强土地利用监督管理,不断提高土地资源集约利用水平     

场地土壤六价铬污染治理试验研究

为深入研究唐山市老自行车厂场区六价铬污染机理和确定治理方案,本文通过一系列的浸泡和土柱试验,查明了六价铬在场地包气带中的污染原理和硫酸亚铁还原固定治理土壤六价铬污染的可行性与相关参数。试验结果表明:污染场地内包气带中六价铬的运移主要受吸附和解析作用的控制。使用PH值为3.0,质量浓度为2.4%的硫酸亚铁溶液作为治理药剂,可将污染场地包气带中93.24%的六价铬去除。     

Uptake of carbamazepine by cucumber plants--a case study related to irrigation with reclaimed wastewater

Reclaimed wastewater is an important source of irrigation in semiarid and arid zones. Here we report data on carbamazepine (CBZ) uptake by cucumber plants in hydroponic culture and greenhouse experiments using different soil types irrigated with fresh water or reclaimed wastewater. Data obtained from the hydroponic culture experiments suggest that CBZ is mainly translocated by water mass flow, and thus it is concentrated and accumulated to the largest extent in the mature/older leaves. Carbamazepine concentration in cucumber fruits and leaves was negatively correlated with soil organic matter content. The concentrations of CBZ in the roots and stems were relatively low, and most CBZ in the plant (76-84% of total uptake) was detected in the leaves. A greenhouse experiment using fresh water and reclaimed wastewater spiked, or not, with CBZ at 1 μg L⁻¹ (typical concentration in effluents) revealed that CBZ can be taken up and bioaccumulated from its background concentration in reclaimed wastewater. Bioaccumulation factor (calculated as the ratio of CBZ concentration in the plant to that in the soil solution) for the fruits (0.8-1) was significantly lower than the value calculated for the leaves (17-20).This study emphasizes the potential uptake of active pharmaceutical compounds by crops in organic-matter-poor soils irrigated with reclaimed wastewater and highlights the potential risks associated with this agricultural practice.