黄河包头段不同粒径沉积物分形校正下重金属的吸附研究

推导了分粒级的表面分形维数计算公式,根据推导公式计算了分粒级沉积物的分维值.应用已有的表面分形分维计算公式分别计算了黄河包头段沉积物整体的表面分形分维(1.91)及＜63 μm粒级的分维值(1.36),揭示出黄河水环境的磨蚀和分选2个原因引起黄河包头段沉积物低的分维值.用分形校正吸附模型、Freundlich和Langmuir吸附模型对黄河包头段重金属分粒级沉积物吸附进行了拟合,表明分形校正吸附模型具有较好的适用性,同时揭示分形校正吸附模型与MEA理论结合能更好的对热力学吸附结果进行描述;由吸附结果分析得出4种重金属因粒径引起的吸附量变化程度序列为Cu＞Pb＞Zn≈Cd,初始浓度高的吸附量曲线变化较初始浓度低的曲线变化明显,同时指出Cu、Pb的吸附主要与矿物组成有关,而Zn、Cd的吸附则与吸附剂沉积物空间几何性质(或沉积物表面物理特征)有关.     

Monitoring historical changes in soil and atmospheric trace metal levels by dendrochemical analysis

The use of dendrochemistry for monitoring historical changes in trace metal deposition and mobilisation of metals in soils is evaluated. In experimental studies, mobilisation of trace metals in surface soil following deliberate acidification was recorded in sugar maple (Acer saccharum) tree-rings with minimal lateral movement between rings. Furthermore, positive correlations between wood (3 year section 1993-95) and foliar chemistry (mean concentration 1993-95) were found for Cd and Zn, but not for Cu and Ni, showing that mobility up the tree bole differs between metals. Even so, substantial lateral movement of elements between rings occurs in some species. Stable Pb isotope ratios in tree-rings were used to show that sacred fir (Abies religeosa) is not a useful monitor of Pb deposition because Pb accumulates in the heartwood. Numerous sophisticated analytical techniques are now used in dendrochemical studies, including laser ablation sampling in conjunction with inductively coupled plasma mass spectrometry that enable the multi-element analysis of extremely small tree-rings with low detection limits. Clearly, not all tree species are suitable for dendrochemical studies, but if careful sampling strategies are used and suitable tree species are chosen, the chemical analysis of tree-rings can provide information concerning historical changes in soil and atmospheric trace metal levels unavailable from any other source.     

宁夏生态移民社区生活空间融合与重构的影响因素及机理——以宁夏闽宁镇为例

生态移民的空间位移引致了迁入区多因素的相互作用及长期演化,成为多学科深入探究的重要问题之一。以闽宁镇生态移民社区为例,采用主成分分析法和地理探测器分析法,对生态移民社区生活空间融合的影响因素和机理进行了研究,结果发现：（1）生态移民社区生活空间融合与重构受多种因素影响,生活基础设施、经济收入增长、移民社区环境、邻里关系、政府政策、民族生活六个主成分对生态移民社区生活空间融合的影响可以起到解释作用。（2）影响生态移民社区生活空间的因子解释力由强到弱依次排序为：X₁生活基础设施>X₂经济收入增长>X₃邻里关系>X₄政府政策>X₅民族生活>X₆移民社区环境;交互探测结果表明社区各要素因子交互后因子解释力呈双线性增强,即任意两个因子交互作用对于生态移民社区生活空间融合的影响强度都大于单个因子的独自作用强度。（3）各影响因素之间的互动影响,共同促进生态移民社区固有的生活方式、文化习惯、社会交往关系的演化,进而形成了生活空间的融合与重构。     

不同草地资源水平牧户对气候变化的感知与偏差途径

人群感知是气候变化适应行为形成的重要信息基础,基于对中国北方草地草甸草原、典型草原、荒漠草原、草原化荒漠、沙地、农牧交错带等地区1292个牧户的问卷访谈,分2轮调查研究了不同草地类型地区牧民对气候变化的感知,与气候实值比较分析,并研究了牧民气候变化感知的偏差途径,结果表明:1980~2009年间研究区温度变化倾向率为0.63℃/10a(P0.05);温度较强的趋势性与牧民对其感知的分歧存在偏差,降水无明显变化与不同地区牧民感知明确的趋势性判断存在偏差;受草场变化等环境信息的传导是气候变化感知偏差形成的重要原因,其中,降水感知与环境感知之间具有较强的关系,存在明显的传导过程,而温度感知的传导性不明显;通过Probit模型分析显示,气候变化传导感知与否主要与牧户距离行政中心距离、户主年龄、教育背景、载畜水平、草畜资源等因素有关.     

An assessment of the nutrient status of sugar maple in Ontario: indications of phosphorus limitation

Soil acidification, caused by elevated anthropogenic deposition, has led to concerns over nutrient imbalances in Ontario's sugar maple (Acer saccharum Marsh.) forests. In this study, soil chemistry, foliar chemistry, crown condition, and tree growth were measured at 36 sugar maple stands that included acidic (pH?相似文献   

青岛理工大学安全工程专业课程体系设置模式

介绍了我国安全工程专业发展概况、存在的问题及青岛理工大学安全工程专业现状.重点介绍了青岛理工大学安全工程专业课程体系设置情况,提出了2006年安全工程专业课程体系设置调整的构想.     

Analysis of tree rings using inductively coupled plasma mass spectrometry to record fluctuations in a metal pollution episode

Analysis of Acer pseudoplatanus L. (sycamore) tree rings using ICP-MS was used to assess the impact of metal deposition on trees growing in the vicinity of a metal refinery at Prescot, north-west England compared to a reference site at Croxteth 6 km distant receiving minimal deposition. No difference in tree growth between sites was recorded. Large reductions in Cu and Cd deposition since the late 1970s was accompanied by a steep decline in Cd concentrations in the outer rings in trees close to the refinery. A similar reduction in Cu concentrations was less apparent due to a tendency for Cu to increase in the outer rings. Zinc and Ni were higher in xylem at Prescot compared to Croxteth. There was no trend in Zn concentrations at either site although Ni concentrations increased in trees close to the refinery after 1982. Manganese concentrations in xylem were much higher at Prescot; Mn levels declined until the late 1970s and then increased slightly in later years interspersed by large concentration peaks within individual years during the 1980s. There was little change in Mn concentrations in trees at Croxteth during this period. Calcium, Mg and Sr concentrations remained steady or declined slightly in rings formed since 1965 in trees at Croxteth. Concentrations of Ca, Mg and Sr were higher in rings formed prior to the mid 1970s in trees at Prescot, but declined steadily after this period, although peaks in concentrations of each element were recorded in individual years during the 1980s. Phosphorous concentrations in rings increased towards the cambium at Croxteth, although P levels decreased in rings formed after 1982 at Prescot. No difference in K concentrations between sites was recorded. Lead concentrations in xylem at both sites declined steadily in rings formed after 1970, although concentrations were higher at the reference site. Analysis of individual sycamore tree rings appears to record short-term changes in pollution episodes, with little lateral movement of elements occurring. It is suggested that changes in element concentrations in trees close to the refinery are a result of reduced metal deposition combined with increased soil acidity due to reduced buffering capacity of metal ions in rainfall.     

Metal partitioning and uptake in central Ontario forests

Evaluation of the potential environmental risk posed by metals depends to a great extent on modeling the fate and mobility of metals with soil-solution partitioning coefficients (Kd). However, the effect of biological cycling on metal partitioning is rarely considered in standard risk assessments. We determined soil-solution partitioning coefficients for 5 metals (Cd, Zn, Pb, Co and Ni) at 46 forested sites that border the Precambrian Shield in central Ontario, where soil pHaq varied from 3.9 to 8.1. Foliage from the dominant tree species and forest floor samples were also collected from each site to compare their metal levels with Kd predictions. Analogous to other studies, log Kd values for all metals were predicted by empirical linear regression with soil pH (r2=0.66-0.72), demonstrating that metal partitioning between soil and soil solution can be reliably predicted for relatively unpolluted forest mineral soils by soil pH. In contrast, whereas the so-called bioavailable water-soluble metal fraction could be predicted from soil pH, metal concentrations in foliage and the forest floor at each site were not consistently related to pH. Risk assessment of metals should take into account the role of biota in metal cycling and partitioning in forests, particularly if metal bio-accumulation and chronic toxicity in the food chain, rather than metal mobility in soils, are of primary concern.     

Uptake of 207Pb and 111Cd through bark of mature sugar maple,white ash and white pine: a field experiment

A field study was undertaken to determine whether 207Pb and 111Cd, applied to the exterior bark of sugar maple (Acer saccharum Marsh.), white ash (Fraxinus americana L.) and white pine (Pinus strobus L.), could enter xylem tissue. Stable isotope tracers (3 microg Pb ml(-1); 2 microg Cd ml(-1)) were applied separately to bark in simulated rainfall, acidified to pH 4.5, in multiple doses over a 4 month (July-October) period. Tree cores were extracted from the region of application in the following March, and Pb and Cd isotopes were measured in bark and the outer tree rings using inductively coupled plasma mass spectrometry. The majority of the applied stable isotope tracer recovered (over 94%) was present in bark tissue, although a small amount of each metal tracer entered the outer (1-3) tree rings in all trees. Despite high concentrations of excess 207Pb in bark (up to 50 microg g(-1)), the maximum concentration of excess 207Pb measured in tree rings was only around 50 ng g(-1), which represents less than 30% of the background Pb concentration in wood at the study site. High excess 111Cd concentrations in bark (up to 35 microg g(-1)) also resulted in small increases in 111Cd in wood (up to 50 ng g(-1)), but due to lower background Cd concentrations in wood, such increases more than doubled the amount of Cd in wood compared with background levels. However, at sites where such high bark Cd concentrations are found, uptake from Cd-contaminated soil would probably be much greater than found at our study site. It appears that Cd and Pb applied to bark can enter woody tissue, but that this route of uptake is likely to be a minor contributor to the metal burden in wood.     

The quantification and distribution of pollution Pb at a woodland in rural south central Ontario, Canada

Lead concentrations and Pb isotope ratios were measured in the forest floor, mineral soil and vegetation at a white pine and a sugar maple stand in a woodland in south central Ontario. Lead concentrations decreased and 206Pb/207Pb ratios increased with mineral soil depth reflecting the mixing of pollution and natural Pb sources. Lead concentrations and 206Pb/207Pb ratios at 20-30 cm depth were approximately 6-7 mg/kg and 1.31-1.32, respectively. Assuming an integrated 206Pb/207Pb ratio in deposition over time of 1.18, estimated from lichen measurements and published data for the region, approximately 65% of Pb in the surface (0-1 cm) mineral soil is from anthropogenic sources. Approximately 90% of pollution Pb is found in the 0-10 cm soil layer (Ah) and less than 3% of the pollution Pb is present in the forest biomass and mull-type forest floor combined. Despite low Pb concentrations in vegetation (<2.5 mg/kg), we estimate that between 65 and 100% of the Pb in vegetation and approximately 75% of the Pb in the forest floor is from pollution sources. In total, the pollution Pb burdens at the pine and maple stands are estimated to be 860 and 750 mg/m2, respectively.