On the influence of faulting on small-scale soil-gas radon variability: a case study in the Iberian Uranium Province

In order to evaluate the influence of faulting on the variability of geogenic radon at detailed scale (1:2000), data on gamma ray fluxes, U and Th concentrations in rocks, radon in soil-gas and radon in groundwater were collected in three target areas on the Oliveira do Hospital region (Central Portugal). This region stands on the Iberian Uranium Province, and is dominantly composed of Hercynian granites and metasedimentary rocks of pre-Ordovician age, crosscut by faults with dominant strike N35°E, N55°E and N75°E. Radiometric anomalies are frequent, associated with faults of the referred systems and metasedimentary enclaves; the analytical data confirms that these anomalies are produced by local high uranium contents in rocks and fault-filling materials (n = 34, range 13-724 ppm), while other radiogenic elements are relatively constant (e.g. Th 4-30 ppm). Radon concentration in soil can be extremely high, up to 12,850 kBq m⁻³ (n = 215), with a large proportion of results above 100 kBq m⁻³. Unsurprisingly, groundwater also shows high radon concentrations, with observed values in the range 150-4850 Bq.L⁻¹ (n = 17). From the results it is concluded that metasedimentary enclaves, as well as faults, can accumulate uranium from circulating fluids, and as a consequence, strongly locally enhance geogenic radon potential. Due to this fact, for the purpose of land use planning in such uranium-enriched regions, very detailed geological mapping is needed to precisely recognize radon high risk areas. A correlation between radon concentration in soil or in groundwater and gamma ray fluxes was established pointing to the possible use of these fluxes as a first step in assessing geogenic radon potential, at least to geological setting similar to the study area.     

Porewater as a matrix in toxicity bioassays with sea urchins and bivalves: evaluation of applicability to the Venice lagoon (Italy)

Porewater plays an important role in sediment toxicity assessment using bioassays, but the most reliable extracting method and the potential contribution of confounding factors to the real toxicity need to be studied. The applicability of bioassays with the early life stages of Paracentrotus lividus, Mytilus galloprovincialis and Crassostrea gigas on porewaters extracted by centrifugation from the Venice Lagoon (Italy) is evaluated and demonstrated: toxicity tests can discriminate the toxicity of porewaters from sites with different kinds and levels of pollution and, using toxicity scores, data are classified in five toxicity classes. Sulphides do not represent a confounding factor in porewater toxicity; in contrast ammonia exhibited some concentrations above the toxicity threshold for sea urchin embryos.     

基于农户调查的农用地流转影响因素研究——以重庆市典型区(县)为例

农用地流转是充分发挥土地利用效益,实现农业规模化生产和产业化经营的一种积极探索,采用参与式农户评估法,以重庆市典型区(县)为例,对农用地流转的影响因素进行了探讨。分析结果表明:缺乏规范的操作程序与农用地流转中介组织、缺乏完善的社会保障体系以及区位条件的差异是影响重庆地区农用地流转的主要因素。建立健全农用地流转相关政策和农村社会保障制度,加速城镇化进程和加强农村基础设施建设对重庆地区的农用地流转具有积极的推动作用。     

资本禀赋对农户绿色生产投资意愿的影响——以秸秆还田为例

作为一种典型的绿色生产方式,秸秆还田兼具环境污染治理与资源循环利用之效,但现实中农户响应并不积极。个体的意愿选择通常会面临着个人及家庭资本禀赋的约束,为探究农户在秸秆还田问题上是否也面临着相同的境况,本文基于相关理论分析,提出了资本禀赋水平和结构会对农户秸秆还田投资意愿产生作用的假说,利用实地调研数据,运用熵值法和CVM方法对农户的资本禀赋水平和结构、秸秆还田投资意愿与水平进行了评价分析,以Probit和Tobit模型实证检验了资本禀赋及其结构对农户秸秆还田投资意愿的影响效应。结果表明:(1)农户的资本禀赋水平存在较大差异,各类资本禀赋按照水平排序为:社会资本(97.99)自然资本(95.42)物质资本(94.88)经济资本(94.23)人力资本(90.01),结构方面以社会资本占优型农户居多,占比40.49%,人力资本占优型的农户个数为0。(2)仅有35.26%的农户愿意投资秸秆还田,但投资意愿水平分布较为均衡,平均投资意愿约为5.62—15.94元/666.7m2·季。(3)自然资本(地形)、物质资本(家电数量)、人力资本(性别比例)、经济资本(收入稳定性和融资能力)和社会资本(制度信任)等水平的提升以及资本禀赋结构的优化均被证明可显著增强农户秸秆还田的投资意愿,可见农户秸秆还田投资意愿不高或因资本禀赋约束所致。由此提出了加强农户资本禀赋积累,优化农户资本禀赋结构的政策建议,以促进秸秆还田等绿色生产方式的推广应用。