Adsorption of rare earth elements onto Carrizo sand: Experimental investigations and modeling with surface complexation

Rare earth element (REE) adsorption onto sand from a well characterized aquifer, the Carrizo Sand aquifer of Texas, has been investigated in the laboratory using a batch method. The aim was to improve our understanding of REE adsorption behavior across the REE series and to develop a surface complexation model for the REEs, which can be applied to real aquifer-groundwater systems. Our batch experiments show that REE adsorption onto Carrizo sand increases with increasing atomic number across the REE series. For each REE, adsorption increases with increasing pH, such that when pH >6.0, >98% of each REE is adsorbed onto Carrizo sand for all experimental solutions, including when actual groundwaters from the Carrizo Sand aquifer are used in the experiments. Rare earth element adsorption was not sensitive to ionic strength and total initial REE concentrations in our batch experiments. It is possible that the differences in experimental ionic strength conditions (i.e., 0.002-0.01 M NaCl) chosen were insufficient to affect REE adsorption behavior. However, cation competition (e.g., Ca, Mg, and Zn) did affect REE adsorption onto Carrizo sand, especially for light rare earth elements (LREEs) at low pH. Rare earth element adsorption onto Carrizo sand can be successfully modeled using a generalized two-layer surface complexation model. Our model calculations suggest that REE complexation with strong surface sites of Carrizo sand exceeds the stability of the aqueous complexes LnOH²⁺, LnSO₄⁺, and LnCO₃⁺, but not that of Ln(CO₃)₂^- or LnPO₄^o in Carrizo groundwaters. Thus, at low pH (<7.3), where major inorganic ligands did not effectively compete with surface sites for dissolved REEs, free metal ion (Ln³⁺) adsorption was sufficient to describe REE adsorption behavior. However, at higher pH (>7.3) where solution complexation of the dissolved REEs was strong, REEs were adsorbed not only as free metal ion (Ln³⁺) but also as aqueous complexes (e.g., as Ln(CO₃)₂^- in Carrizo groundwaters). Because heavy rare earth elements (HREEs) were preferentially adsorbed onto Carrizo sand compared to LREEs, original HREE-enriched fractionation patterns in Carrizo groundwaters from the recharge area flattened along the groundwater flow path in the Carrizo Sand aquifer due to adsorption of free- and solution-complexed REEs.     

正态化克立格法在路腊汞矿储量计算中的应用

正态化克立格法是对传统储量计算方法的改革和创新。其计算过程的科学性和计算结果的正确性在路腊汞矿作了探采对比试算，取得了良好的结果。     

Study of portable infrastructure-free cell phone detector for disaster relief

Natural Hazards - In this paper, we investigate the spatial and temporal distributions of rainfall in Qatar, which falls in the arid region of the middle-east. We use rainfall data from 29 rain...     

中国干旱半干旱区农业生态地质环境系统工程研究

干旱半干旱区是当前我国农业经济发展最有潜力的地区。可是，该区生态环境脆弱，并受到一定程度的破坏。利用系统工程学的原理，从农业生态地质环境容量的角度出发，对该区的农业生态地质环境的演化过程和演化模式进行了研究，进而提出了农业生态地质环境系统工程研究模式。在调控社会人口和经济发展的基础上，合理开发利用水、土、生物资源，保护治理生态环境，提高自然资源环境的承载力，抑制对资源环境的破坏力，使该区农业生态环境得以恢复和重建，建立起稳定持续发展的农业基地。     

煤中黄铁矿的成因研究

本文在系统地研究四川晚二叠世高硫煤中黄铁矿矿物学的基础上，运用微区电子探针、中子活化、Ｘ光电子能谱和硫同位素等多 种方法综合地研究煤中黄铁矿的结构、成分、价态及同位素等成因标型特征，对黄铁矿标型特征进行了成因探讨，有效地判别了成岩期形成的Ｉ型脉状黄铁矿及后生热液Ⅱ型脉状黄铁矿。同时提出直接沉淀系列（自形晶→集合→聚晶）和复杂成因（微粒、莓粒→圆球→结核→团块）等两大类成因演化模式。它不仅对不同类型     

中国与基性—超基性岩有关的Cu－Ni（Pt）矿床成矿系列类型

中国与基性—超基性岩有关的Ｃｕ－Ｎｉ（Ｐｔ）矿床，主要形成于以前寒武系为基底的大陆裂谷，部分形成于增生褶皱带中显生宙地层为基底的裂陷槽环境。根据形成时代、当时所在的构造环境单元及成矿岩浆系列，划分为９个矿床成矿系列和８个矿床成矿亚系列。成矿时代以元古代、晚古生代为主。现今，矿床主要分布于地台边缘，造山带中也有产出，但不代表其当时形成的地质背景。成矿物质来源为上地幔，原始岩浆以上地幔部分熔融的高ＭｇＯ拉斑玄武岩（拉斑橄榄玄武岩）岩浆系列为特征，也有钙碱性岩浆（喀拉通克）和科马提岩岩浆系列（桂北）。地壳物质混染比较普遍。矿床成因类型主要为岩浆熔离型，且以硅酸盐岩浆上侵前的深部熔离作用为主。还有热液成因类型（煎茶岭）。矿床成矿系列的时空分布与中国大陆的构造演化密切相关     

Accumulation and risk of heavy metals in relation to agricultural intensification in the river sediments of agricultural regions

The enrichment characteristics and risk of heavy metals were studied in the sediments of Liucha River in Chao Lake Valley, where agricultural intensification has developed rapidly since the 1980s. The results revealed that Cd, Pb and Zn showed the lowest levels in the upper reaches and peak values in the lower reaches, increasing from 0.064, 7.75 and 59.75 mg/kg to 0.176, 12.33 and 96.82 mg/kg on average, respectively. Enrichment factor (EF) analysis showed that the EF values of Cd, Pb and Zn (maximum 4.76, 2.51 and 2.74, respectively) all increased from the upper reaches to the lower reaches (>1.5), while correlation analysis and cluster analysis showed that they primarily originated from the extensive use of phosphate fertilizer. In addition, the comprehensive potential ecological risk due to Cd, Cr, Cu, Ni, Pb and Zn in the sediments showed low degree, but Cd showed moderate and high risk at some sites. Therefore, heavy metal pollution due to agricultural intensification in the agricultural regions of Chao Lake Valley should be given great attention during management of the water environment.     

Past atmospheric trace metal deposition in a remote lake (Lake Ngoring) at the headwater areas of Yellow River,Tibetan Plateau

A complete record derived from a core dated both by ²¹⁰Pb and ¹³⁷Cs chronologies from Lake Ngoring at the headwater areas of the Yellow River provides new insight into the changing atmospheric deposition of trace metals including Cd, Cr, Cu, Ni, Pb, and Zn. This study showed that there was an inflection in the early 1960s, before which both fluxes and contents of Cd, Ni, Pb, and Zn remained relatively steady or slowly increased, and thereafter continued increases both in fluxes and contents were found. Taking Pb as an example, the flux increased from 0.13 (before 1960) to 0.25 mg m^?2 a^?1 (averaged 1963–2006). According to atmospheric flux calculations using Al as a reference element, atmospheric fluxes of trace metals generally showed a rapid increase and peaked in recent years, closely following the historical economic development of the neighboring region, mainly for Qinghai and Gansu provinces. The atmospheric inventory for Zn was the highest, reaching 1.068 g m^?2, while the lowest was for Cd, at only 0.079 gm^?2. The percentage proportions of atmospheric deposition for Cd, Ni, and Zn were 37, 12, and 8.7 %, respectively. Hence, the atmospheric contribution to the trace metal content via long range transport is not negligible when considering input of materials to lake ecosystems.