Potential Use of the Plant Antioxidant Network For Environmental Exposure Assessment of Heavy Metals in Soils

In recent years, awareness has risen that the total soil content of pollutants by itself does not suffice to fully assess the potential ecotoxicological risks involved. Chemical analysis will require to be complemented with biological assays in a multidisciplinary approach towards site specific ecological risk assessment (SS-ERA). This paper evaluates the potential use of the plants' antioxidant response to metal-induced oxidative stress to provide a sensitive biological assay in SS-ERA. To this end, plants of Phaseolus vulgaris were grown for two weeks on 15 soils varying in contamination level. Morphological parameters and enzymatic plant responses were measured upon harvest. Foliar concentrations of the (heavy) metals Al, Cu, Cd, Cr, Fe, Mn, Ni, Pb, Zn were also determined. Metal mobility in the soil was further assessed by determining soil solution and NH₄OAc extractable levels. In general more significant correlations were observed between plant responses and foliar metal concentrations or exchangeable/soluble levels than between plant responses and the total soil content. The study demonstrates the potential use of the plants' antioxidant defence mechanisms to assess substrate phytotoxicity for application in SS-ERA protocols. However, the system, based on calculation of a soil Phytotoxicity Index (PI), will require adaptation and fine-tuning to meet the specific needs for this type of environmental monitoring. Large variation was observed in phytotoxicity classification based on the various test parameters. The thresholds for classification of the various morphological and enzymatic response parameters may require adaptation according to parameter stress sensitivity in order to decrease the observed variation. The use of partial PI's (leaves and roots separately) may in addition increase the sensitivity of the system since some metals show specific effects in one of both organs only. Loss of biological functionality of enzymes, as was observed for ICDH in one of the more strongly contaminated soils, may also be recognized as an additional stress symptom when assigning phytotoxicity classification, whereas the current system only considers increasing enzymatic capacities. Other easily distinguishable parameters, which could be added to the current indexation are: failure to germinate and the incapacity to develop roots in the toxic substrate.Additional research will be required to determine the possible application range of soil properties for this biological assay and to further improve its performance in SS-ERA.     

南极粒雪芯中的硝酸盐记录─—平流层冬/春季脱氮作用的证据

采白南极威德尔海地区极地涡流中的一支粒雪芯表明，在春季或夏初出现硝酸盐峰值。在更北面获得的两支粒雪芯的硝酸盐浓度要低得多。尽管还需要其它的数据，间接的证据已表明峰值可能是由于冬春季期间来自平流层的极地平流层云的沉积作用造成的。过去三十年中，峰形反有变化。从冰芯中观察过去平流层在较长时间尺度上的状况是可能的，但其它因素可能会消除冰期冰芯中的信息。     

美国油页岩的核磁共振研究

<正> 美国油页岩中有机质的性质Smith(1981)评述了作为将来合成燃料来源的美国油页岩资源的潜在储量,并逐个地叙述了美国的主要沉积岩——始新世格林河建造、泥盆纪大陆中部黑色页岩和二叠纪波斯波里亚建造。本文是Smith报告的扩充,报道了用固态~(13)C核磁共振(NMR)测量来确定美国油页岩中有机质的性质。美国约有20%的面积覆盖着含有机质沉积岩,这些岩石属于油页岩类,其地质年代范围     

火山灰流凝灰岩的对比

<正> 火山灰流岩席(以下简称岩席)常常是难以对比的。其原因有:(1)原始分布不连续;(2)保存不完整;(3)熔结和结晶具有垂直分带和水平分带特征;(4)平均粒度和分选度在垂向和径向上是渐变的;(5)斑晶在化学成分以及数量、种类和矿物成分上具有分带性;(6)各喷发旋回连续形成的岩席在物理性质、化学性质和分带性方面具有相似性;(7)侵位在源区周围不同地段的带状灰流岩席是连续脉动式喷出形成的;(8)带状岩席溢出相与火山塌陷内部相在成分、厚度和熔结度上有显著的差别。     

用海洋沉积物吸附锕系元素:沉积物与海水比率对测量分配率的影响

使用一种标准分次处理技术研究了固体与溶液比率对测量分配率的影响。研究了锕系元素镅镎及钚和两个不同深度的海沉积物,结果表明由一种少量不可分离的或低 R_d 的物种存在常常可以解释随沉积物浓度增加分配率显著降低。同时也表明在不同的固体与溶液比例时,由测量这个R_d 来估计低 R_d 物种存在的比例是可能的。这些物种可能是胶体或稳定的络合物。与高含量碳酸盐沉积物一起的钚呈现出反常状态,随这个高含量碳酸盐沉积物与溶液比率从2 g/L 增加到20g/L 时,钚的分配率则从大于10~4ml/g 降低到10~2ml/g。在高浓度沉积物时,钚在溶液中主要是 Pu~(+v)和 Pu~(+v(?))的氧化态形式,认为碳酸钚(Ⅴ)或碳酸钚(Ⅵ)是存在的主要物种。     

An ultra-clean firn core from the Devon Island Ice Cap, Nunavut, Canada, retrieved using a titanium drill specially designed for trace element studies

An electromechanical drill with titanium barrels was used to recover a 63.7 m long firn core from Devon Island Ice Cap, Nunavut, Canada, representing 155 years of precipitation. The core was processed and analysed at the Geological Survey of Canada by following strict clean procedures for measurements of Pb and Cd at concentrations at or below the pg g(-1) level. This paper describes the effectiveness of the titanium drill with respect to contamination during ice core retrieval and evaluates sample-processing procedures in laboratories. The results demonstrate that: (1) ice cores retrieved with this titanium drill are of excellent quality with metal contamination one to four orders of magnitude less than those retrieved with conventional drills; (2) the core cleaning and sampling protocols used were effective, contamination-free, and adequate for analysis of the metals (Pb and Cd) at low pg g(-1) levels; and (3) results from 489 firn core samples analysed in this study are comparable with published data from other sites in the Arctic, Greenland and the Antarctic.     

Effects of an Experimental Enrichment of Instream Habitat Heterogeneity on the Stream Bed Morphology and Chironomid Community of a Straightened Section in a Sandy Lowland Stream

A straightened stream stretch with poor habitat heterogeneity was divided into a “control” section with a low amount of submerged woody debris and an experimentally “wood-enriched” downstream section to study the effect of enhanced habitat diversity on the benthic invertebrate community. The downstream section was enriched by fixing 25 wood packages constructed from 9–10 branches on the stream bottom. Succession processes occurring in the two stream sections were compared by chironomid exuviae drift from July to November 2000 and from April to August 2001. During the first sampling period, more drifting chironomid exuviae (medians of control vs. wood-enriched: 446 vs. 331, no significant difference) and total number of taxa (44 vs. 36, Wilcoxon signed-rank test P = 0.019) were recorded for the control section. Although species compositions of both stream sections were highly similar (Sørensen index: 0.83) the diversity in the wood-enriched section was distinctly lower compared to the control section (Shannon–Weaver index: 1.19 vs. 1.50). During the second sampling period, exuviae numbers remained higher in the control section (median: 326 vs. 166), but total numbers of taxa were nearly equal (51 vs. 49), as well as species diversity (Shannon–Weaver index: 1.67 vs. 1.64). The lower chironomid diversity observed during the first sampling period coincided with a gradual but significant change of the streambed morphology in the wood-enriched section. There, the initially more U-shaped profile (V/U = 0.81 ± 0.37) had turned into a pronounced V shape (V/U = 1.14 ± 0.21), whereas the control section retained its unaltered U shape (V/U = 0.62–0.75). This small-scale study on experimental of woody debris in sandy lowland streams showed that the negative impact of increased hydraulic disturbance of the existing streambed more than outweighed any positive impact resulting from the increase in woody debris.     

Environmental load of Cryptosporidium parvum oocysts from cattle manure in feedlots from the central and western United States

The first step in assessing the risk of water contamination by Cryptosporidium parvum oocysts from feedlot cattle (Bos taurus) production systems is to quantify the number of C. parvum oocysts present in the fecal material deposited by feedlot cattle. Our primary objective for this project was to estimate the daily environmental load of C. parvum oocysts in fecal material deposited by feedlot cattle from across the central and western USA. Our secondary goal was to genotype isolates of C. parvum from feedlot cattle to help facilitate proper identification of mammalian sources of waterborne C. parvum. Based on 5274 fecal samples from 22 feedlots in seven states (California, Washington, Colorado, Oklahoma, Texas, Nebraska, and South Dakota), we estimated a point prevalence of C. parvum of 0.99 to 1.08% in fecal material from feedlot pens from a wide range of climates and a diverse range of feedlot management systems. On average, fresh fecal material from throughout feedlot systems (recent arrivals to nearing slaughter) contained about 1.3 to 3.6 oocysts/g feces, which roughly translates to about 2.8 x 10(4) to 1.4 x 10(5) oocysts/animal per day.     

Energy and redox status, and carbon allocation in one- to three-year-old spruce needles

Metabolite pools were determined in lyophilized homogenates of one- to three-year-old needles from 13-year-old spruce trees. These were exposed in open-chambers for five consecutive years to SO(2) (30 microg m(-3)) and O(3) (50 to 180 microg m(-3)), singly and in combination. The samples were taken shortly before bud break (mid-March). The energy (ATP/ADP) and redox status (NAD(P)H/NAD(P)) increased with needle age. This increase was most pronounced in needles exposed to both pollutant gases. To evaluate carbohydrate metabolism, levels of starch, sugars (sucrose, fructose, glucose), sugar phosphates (dihydroxyacetone phosphate, glyceraldehyde 3-phosphate (triose phosphates, TP), fructose 6-phosphate, fructose 2,6-bisphosphate: F2,6BP) and 3-phosphoglyceric acid (PGA) were measured. The concentrations of starch, glucose, fructose and TP on a dry weight basis increased with needle age, while those of sucrose and F2,6BP decreased. Interestingly, the total amount of soluble sugars remained constant in needles from control chambers and large fluctuations mainly occurred after a single application of the pollutants. Needles from fumigated trees generally showed somewhat lower starch and sugar, and fructose 6-phosphate levels. The content of TP increased with needle age while that of sucrose and F2,6BP decreased. This inverse behavior was even more prominent in the presence of both pollutants and is discussed in the context of recent knowledge on the regulation of carbon partitioning. There was a significant increase in the ratio of TP/PGA in samples from the combined exposure treatments. This also indicates an increase in the redox charge and corroborates the data on both the redox status of the pyridine nucleotide system and the significantly increased ATP/ADP ratio. The results are indicative of a switch in metabolism, from anabolic to predominantly catabolic reactions, which is most pronounced in the samples fumigated with both O(3) and SO(2). The data are compared to those obtained from naturally exposed trees in the southern Black Forest (K?lbelescheuer/Haldenhof, near Freiburg, Germany).