Impacts of karst paleo-sinkholes on mining and environment in northern China

The karst paleo-sinkhole is a special geological structure widely found in the coal measures of northern China. Some paleo-sinkholes have high permeability and connectivity, making them excellent connectors between the karst aquifer and the coal seam. Consequently, during coal extraction disastrous water inrushes take place frequently, which cause severe loss not only in mine submersions and personnel casualties, but also in environmental quality. Locations and the geological and hydrogeological characteristics of paleo-sinkholes in northern China are presented. In-situ drilling and excavation results show that paleo-sinkholes have different hydrogeological behaviors in different regions and in different mines. Based on observed data, mining-induced strata failure in the seam floor is analyzed. The existence of paleo-sinkholes increases the floor strata failure zone. Numerical simulation then is adopted to model coal mining with the effects of both the paleo-sinkholes and the water pressure in the confined aquifer. Analyses of the simulation conclude that the paleo-sinkhole induces the increase in the strata failure and deformation. These make water inrushes more likely to happen.     

Impacts of climatic variables on water-level variations in two shallow Eastern Mediterranean lakes

Variations in temperature and precipitation have direct impacts on the physical, chemical and biological characteristics of the shallow lakes. This paper examines the possible linkages between climate variables and the water levels of shallow interconnected Lakes Mogan and Eymir, located 20 km south of Ankara in Central Anatolia. The variations in the lakes’ water levels during 1996–2015 are studied and the impacts of climate variables on the lake levels are assessed to address the long-term consequences. The nonparametric Mann–Kendall test was used to quantify trends in the climate variables and the lakes’ level fluctuations between the observation periods 1998–2007 and 2008–2014. Statistical analyses results showed that precipitation and temperature have crucial influence on the variations in the lakes’ levels. The projected increase in temperature and decrease in precipitation over the next century may produce substantial decreases in lake levels, with consequent drying of both lakes.     

Dominance of point source in heavy metal distributions in sediments of a major Sydney estuary (Australia)

 Size-normalized (<63 μm) distributions of Cu, Zn, and Pb in the surficial sediments of one of Sydneys' four major estuaries – the Georges River/Botany Bay estuary – are not facies or depositionally controlled, but rather their distribution is dominated by source. Point sources (waste dumps, sewage overflows, and discharge from a polluted river) are responsible for elevating sediment heavy-metal concentrations up to 50 times above background. Nonpoint sources contribute in raising baseline levels to four times background and comprise mainly stormwater and also marinas, moorings, and wharfs/jetties. Heavy metals disgorged from a point source (Cooks River) strongly impact the sediments in the lower estuary, which has implications for the construction of a new runway for Sydney airport. Received: 3 October 1994 · Accepted: 21 September 1995     

Assessment of heavy metal contamination status in sediments and identification of pollution source in Ichkeul Lake and rivers ecosystem,northern Tunisia

The aim of this study was to determine the concentration of Pb, Zn, Cu, Cd, Cr, and Fe in sediments of the Ichkeul Lake and rivers ecosystem in northern Tunisia; their comparison with international sediment quality criteria was also proposed to assess the extent of metal pollution and their origin using various pollution indicators. For this purpose, sediment samples were collected in thirteen locations and characterized for metal content (Pb, Cr, Zn, Cu, Cd, and Fe) using the total digestion technique. Pollution level was assessed via the geoaccumulation index (Igeo), enrichment factor (EF), contamination factor (C ), potential ecological risk (PER), and pollution load index (PLI). Our results showed that all metals were lower than the threshold effect levels (TEL), the effect range low (ERL), the probable effect level (PEL), the effect range median (ERM), and the probable effect concentration (PEC) value, except Pb and Cr (higher than TEL), the threshold effect concentration (TEC), and the toxicity reference value (TRV). The geoaccumulation index (Igeo) indicated no pollution for Cr, Cu, Zn, and Fe, but moderate pollution for Pb. The enrichment factor showed no enrichment for most of the studied metals. This was further confirmed by the contamination factor that indicated low contamination levels, with the exception of Pb. The pollution load index (PLI) showed moderate pollution status in all the studied stations in the Ichkeul Lake and rivers ecosystem. The statistical results presented similar trends of Zn and Pb probably due to their similar pollution sources. It was found that the Ichkeul Lake and river ecosystems are characterized by moderate pollution status in all the studied sites except for that of a feeder river drained from an old lead mine which had relatively high metallic concentrations of Pb and Cd. It can be argued that effective remediation strategies and environmental management plans are required to control and reduce the input of environmentally hazardous toxic pollutants (Cd and Pb). This study may serve as a useful reference tool pertinent to approaches to the remediation of the old lead mine area surrounding the Ichkeul Lake as well as other areas under similar ecological conditions..     

Kinetics of nutrient and metal release from decomposing lake sediments

Rates of anaerobic decomposition of Lake Erie sediments were determined for seven depth intervals at three temperatures. Sealed sediment sections were incubated under anoxic conditions and the interstitial waters were serially sampled over a period of approximately 200 days. Concentration increases of bicarbonate, phosphate, ammonium, Ca, Mg, Fe and Mn in pore water within any given depth interval followed zero order kinetics over the sampling period and exhibited Arrhenius temperature dependency. Rates of release to the pore waters were proportional to the concentrations in the solid phases, indicating first order kinetics overall.The rates and temperature dependencies of these fermentation reactions were only slightly less than those reported from sediments undergoing sulfate reduction. The observed release rates decreased exponentially with depth in the sediment due to a corresponding decrease in the amount of metabolizable organic matter and acid hydrolyzable mineral phases.A stoichiometric model was constructed utilizing the observed release rates and assumed chemical reactions to predict the stoichiometry of the decomposing organic matter and the nature of the hydrogen buffer. The modeling indicates that 60% of the observed bicarbonate release is the direct result of organic decomposition, that 20% of the release is from the dissolution of calcium carbonate mineral phases, and that the remaining 20% of the release is from the dissolution of magnesium, iron und manganese carbonate mineral phases.Kinetic modeling of the observed production rates accurately predicts the vertical profiles of Ca, Mg, Fe and Mn, but cannot quantitatively account for all the concentration differences of the nutrient elements C, N and P. This implies that in addition to decomposition, increased depositional flux also accounts for the significant changes in concentrations of the nutrient elements in the near surface sediments.     

非点源污染的流域分配方法研究

农业非点源污染的流域分配研究对于提高环境质量具有重要的现实意义。根据遥感技术得到的土地利用类型、河网、道路、圩区等信息,结合地理信息系统（GIS）的空间分析功能,对非点源污染负荷进行了定量计算及可视化分析,在此基础上,得到各主要河段的污染分配量,这可为寻求流域内合理的土地利用模式和农业非点源污染排放总量的控制方法提供决策依据。     

新疆北部主要金属矿产与构造演化

新疆北部古生代可划分为3大古板块：西伯利亚板块、哈萨克斯坦板块和塔里木板块。3个板块之间存在的大洋分别是准噶尔－北天山大洋和南天山大洋。正是这些板块和已经消失了的大洋壳之间的相互作用，决定了该区大地构造演化的基本特征，控制着大地构造格局和矿产分布。古生代新疆北部构造活动极为活跃。此期间，西伯利亚板块不断向南增生，塔里木板块向北运动。塔城地块属哈萨克斯坦板块的一部分，阿尔泰地块从奥陶纪初就随着萨彦—蒙古洋的闭合成为西伯利亚板块的一部分，准噶尔地块在石炭纪初增生于西伯利亚板块西南缘，当时北天山存在较大…     

Effects on nutrient regime in two recipients of nitrogen-rich mine effluents in northern Sweden

The question of the limiting nutrient(s) for production of phytoplankton and macrophytes was explored in two contrasting freshwater systems receiving N- and P-rich mine effluents from the Boliden and Kiruna mine sites, northern Sweden. For both sites, total N (TN), total P (TP) and TN:TP mass ratios in water, sediment and macrophytes were used to examine (1) spatial variations within the systems, (2) differences between the systems and (3) seasonal variations. The TN concentration from the discharge point at the Kiruna site was about seven times higher than at the Boliden discharge point, while the TP concentration was 10 times lower than in the discharge point at the Boliden site. The majority of the studied lakes showed elevated biomass of phytoplankton, with maximum values found in Lake Bruträsket (Boliden). Mining activities have affected the nutrient regime of the two recipients by contributing to elevated TN and TP concentrations and TN:TP mass ratios as well as elevated production of phytoplankton and macrophytes compared to the reference sites. Depending on the NH₄ concentration in the effluent at the Boliden site, water column TN:TP mass ratios shifted from being >22, indicating P-deficiency, to between 9 and 22, indicating a transition from N- to P-deficiency (co-limitation). However, water column TN:TP mass ratios at the Kiruna site always indicated P-deficiency, while TN:TP mass ratios of macrophytes indicate that both sites may vary from N- to P-limitation. The study suggests that for the design of efficient monitoring programmes and remediation measures, it is important to consider the major N and P species in water, phytoplankton, sediment and macrophytes.     

黄河干流潼关断面非点源污染负荷估算

基于平均浓度法原理,根据黄河中游降雨径流特点,将年内过程分为汛期和非汛期两个阶段,同时将高含沙水流中的污染负荷分为水体中的溶解态污染负荷、泥沙吸附态负荷两部分,提出了多沙河流非点源污染负荷估算模型;根据黄河干流潼关断面1950-2006年实测水沙资料,结合水体、泥沙污染物浓度测定试验,分别计算了潼关断面2006年以及丰水年(P=25%)、平水年(P=50%)、枯水年(P=75%)3种不同代表年型下的非点源污染负荷.结果表明:黄河干流潼关断面年污染负荷以汛期为主,汛期污染负荷以非点源为主;非点源污染负荷中,硝酸盐氮、氨氮以溶解态为主,总磷以吸附态为主;潼关断面非点源污染负荷占全年负荷比例:丰水年时,硝酸盐氮占63.09%,氨氮占61.32%,总氮占87.17%、总磷占89.83%;枯水年时,硝酸盐氮占26.92%,氨氮占24.62%,总氮占67.60%、总磷占71.73%.2006年,硝酸盐氮、氨氮、总氮和总磷非点源污染负荷占全年比例依次为:17%、14%、15%和41%.     

基于NPP-VIIRS数据的喜马拉雅山北坡典型湖泊湖冰提取分析

现阶段使用遥感数据监测湖冰物候特征已成为主要的技术手段.NPP-VIIRS是一个较新的卫星数据,它具有空间分辨率较高、波段数多、重访周期短等优点,使用该数据提取湖冰信息是对该领域的一个有益补充.基于NPP-VIIRS数据利用阈值法对拉昂错、玛旁雍错、佩枯错、普莫雍错等典型湖泊进行湖冰提取.获得四个湖泊逐日的冻结百分比,...     

Effect of rainfall and antecedent dry periods on heavy metal loading of sediments on urban roads

Concentration and mass loadings of heavy metals adsorbed on sediment from an urban road surface in Beijing were investigated. The buildup and washoff processes are discussed. Results showed that masses of sediments smaller than 500 μm in diameter varied from 11.2 to 25.5 g/m². On average, sediments smaller than 125 μm accounted for 42.9% of sediments smaller than 500 μm in mass. Cd, Cr, Cu, and Ni were more likely to attach to smaller sediments than bigger ones, compared to Pb and Zn. Mass loading of the sediments generally increased with antecedent dry periods, but the linear relationship was better for smaller sediments than for bigger ones. Heavy metal concentrations adsorbed on sediments with diameter less than 40 μm generally decreased more obviously than those adsorbed on bigger ones after rainfall events.     

Rates of trace metal and nutrient diagenesis in an intertidal creek bank

Carbon mineralization in marine sediments is a key process involved in the cycling of carbon, nutrients and trace metals. However, as marine sediments are usually diffusion dominated, the pace of element and nutrient cycling is slow, because consumption of oxidants and/or nutrients in the pore waters via microbial activity often outpaces resupply. Adding an advective flow component to such a system should change the biogeochemical dynamics considerably. Numerical simulations show that shallow coastal aquifers affected by tidal forces can establish ground water velocities of up to 7 cm h⁻¹, driving a circulation of sea water through the sediments with subsequent discharge. Although known to enhance solute exchange, the impact of advection on early diagenesis has not received much attention.To address this issue we mapped the interstitial water chemistry down to 2.5 m sediment depth along a transect on an intertidal creek bank that is subject to a periodic advective flow. Additionally a recently developed hydrogeological simulation of the creek bank was applied to calculate ages of the sampled pore waters. Sample ages obtained were used to quantify (flow path integrated) production or depletion rates for trace metals, nutrients, and sulphate.We find young sea water percolating relatively fast through sediments close to the creek showing strong signs of alteration, whereas pore waters from diffusion dominated regions are less altered. The increase in inorganic nutrients and some trace elements along the flow path requires high rates of turnover. Sulphate, molybdenum, and uranium are almost completely depleted after 200 days, while dissolved inorganic carbon (DIC), ammonia, and manganese increase. Averaged production rates for DIC appear to be three times higher when advection dominated the subsurface flow regime. Our results demonstrate that sites dominated by advection generally show signs of faster rates of diagenetic reactions.     

Uptake and recycling of lead by boreal forest plants: Quantitative estimates from a site in northern Sweden

As a consequence of deposition of atmospheric pollution, the lead concentration in the mor layer (the organic horizon) of remote boreal forest soils in Sweden is raised far above natural levels. How the mor will respond to decreased atmospheric pollution is not well known and is dependent on future deposition rates, downward migration losses and upward fluxes in the soil profile. Plants may contribute to the upward flux of lead by ‘pumping’ lead back to the mor surface through root uptake and subsequent litter fall. We use lead concentration and stable isotope (²⁰⁶Pb, ²⁰⁷Pb and ²⁰⁸Pb) measurements of forest vegetation to quantify plant uptake rates from the soil and direct from the atmosphere at two sites in northern Sweden; an undisturbed mature forest and a disturbed site with Scots pine (Pinus sylvestris) growing on a recently exposed mineral soil (C-horizon) containing a minimum of atmospherically derived pollution lead. Analyses of forest mosses from a herbarium collection (spanning the last ∼100 yr) and soil matrix samples suggest that the atmospheric lead deposited on plants and soil has an average ²⁰⁶Pb/²⁰⁷Pb ratio of 1.15, while lead derived from local soil minerals has an average ratio of ∼1.47. Since the biomass of trees and field layer shrubs has an average ²⁰⁶Pb/²⁰⁷Pb ratio of ∼1.25, this indicates that 70% ± 10% of the inventory of 1 ± 0.8 mg Pb m⁻² stored in plants in the mature forest originates from pollution. Needles, bark and apical stemwood of the pine growing on the disturbed soil, show lower ²⁰⁶Pb/²⁰⁷Pb ratios (as low as 1.21) than the roots and basal stemwood (having ratios > 1.36), which indicate that plants are able to incorporate lead directly from the atmosphere (∼50% of the total tree uptake). By partitioning the total uptake of lead into uptake from the atmosphere and different soil layers using an isotopic mixing model, we estimate that ∼0.03 ± 0.01, 0.02 ± 0.01 and 0.05 ± 0.01 mg Pb m⁻² yr⁻¹ (mean ± SD), is taken up from the mor layer, the mineral soil and the atmosphere, respectively, by plants in the undisturbed mature forest. These small fluxes, which are at least a magnitude lower than reported downward migration losses, suggest that plant uptake will not strongly prolong the self-cleaning rate of the mor layer.     

Trace metal deposition and mobility in the sediments of two lakes near Sudbury,Ontario

The accumulation and mobility of Fe, Mn, Al, Cu, Ni and Pb in the sediments of two lakes (Clearwater, pH 4.5; and McFarlane, pH 7.5) near Sudbury, Ontario have been investigated. The Al, Cu and Ni concentrations are expectedly relatively high in the overlying waters of Clearwater Lake and much lower for Al and Cu in McFarlane Lake. The low trace metal concentrations found in the anoxic porewaters of Clearwater Lake could be explained by a sharp increase in porewater pH concomitant with SO₄² reduction and H₂S production within the first 1–2 cm of the sediments, which has conceivably led to the precipitation of mineral phases such as AL(OH)₃, NiS, and CuS. In both lakes, Fe concentrations in anoxic porewaters appear to be controlled by FeS and/or FeCO₃ formation. Solubility calculations also indicate MnCO₃ precipitation in McFarlane Lake. In Clearwater Lake, however, both porewater and total Mn were relatively low, a possible result of the continuous loss of Mn(II) through the acidic interface. It is suggested that upwardly decreasing total Mn profiles resulting from the removal of Mn from the top sediment layers under acidic conditions may constitute a reliable symptom of recent lake acidification.The downward diffusion of AI, Cu and Ni from the overlying water to the sediments has been estimated from their concentration gradients at the interface and compared to their total accumulation rates in the sediments. In both lakes the diffusion of Al is negligible compared to its accumulation rate. However, diffusion accounts for 24–52% of the accumulation of Cu in the sediments of Clearwater Lake, but appears negligible in McFarlane Lake. The downward diffusive flux of Ni is important and may explain 76–161% of the estimated Ni accumulation rate in Clearwater Lake, and 59% in McFarlane Lake. The porewater Cu and Ni profiles suggest that the subsurface sedimentary trace metal peaks observed in Clearwater Lake (as in other acid lakes) may not be caused by sediment leaching or by a recent reduction in sedimentation but may have a diagenetic origin instead. Diffusion to the sediments thus appears to be an important and previously overlooked trace metal deposition mechanism, particularly in acid lakes.     

松辽盆地北部登娄库组二段烃源岩分布定量研究

勘探开发初期有限的油气资源评价资料限制了暗色泥岩预测方法的可靠性,松辽盆地北部登娄库组烃源岩主要为登二段灰色泥岩,其分布情况是评价松辽盆地北部深层致密砂岩气藏资源量的重要基础。本文以井震信息和基于沉积特征的多元地震属性定量方法,预测研究区泥岩厚度平面分布,综合地层沉积厚度平面信息、地震相平面信息及井点暗色泥岩和泥岩厚度比值信息,预测全区暗色泥岩和泥岩厚度比值的平面分布,预测结果显示松辽盆地北部登二段烃源岩主要有3个较大的发育,同时伴有其它零星小范围暗色泥岩发育,大部分厚度分布在70 m以下,最大暗色泥岩预测厚度约为350 m。该方法以井震信息为基础结合沉积规律定量预测暗色泥岩分布,为松辽盆地北部深层致密砂岩气藏资源量的可靠评价提供了必要的基础。     

平台巴西圆盘研究综述及三维启裂点研究

总结了对平台巴西劈裂试验平台中心角的研究,归纳总结了抗拉强度计算公式的修正系数k。通过建立两种平台角的三维有限元模型探究试样内应力分布状态,通过对受压直径所在平面及过平台末端的竖直平面的受力分析,发现Griffith等效应力分布规律会随平台角的改变而改变,且在两种平台角下等效应力最大值均出现在平台边缘处。结合三维离散元方法模拟试验中裂纹开展过程,发现微裂纹最早集中于平台末端,但随着荷载的增加致使试样破裂的裂纹起始于试样中部。有限元的力学分析与离散元的破裂过程模拟可很好地相互印证。通过与试验现象对比发现,加工精度对裂纹模式有着重要影响,为保证由平台巴西劈裂试验测量岩石抗拉强度的有效性,在试样与试验机之间垫入垫片是较为可行的方法。     

气候变化对大兴安岭北部沼泽景观格局的影响

大兴安岭北部地区由于在高纬、高海拔双重因素作用下,形成了独特的山地沼泽类型。首先使用Logistic回归模型分析了沼泽湿地与18种环境因子(11种地形因子和7种气候因子)的关系,结合CGCM3未来气候模型(加拿大气候模拟和分析中心推出的第三代全球气候耦合模型)预测未来分布,然后利用Fragstats软件计算景观格局的变化。所建模型具有很高的预测精度(ROC为0.96),预测结果表明:到2100年,SRESB1情景下,大兴安岭北部沼泽的潜在分布面积减少54.16%,南部相对平坦的丘陵和山间平原的沼泽大量消失;SRESA1B情景下,面积减少59.62%,南部林区的沼泽几乎全部消失;SRESA2情景下,面积减少73.51%,沼泽几乎完全退化到北部海拔较高处。另外,沼泽景观格局随气候变暖,平均斑块面积变小,形状指数减小,聚集度减少但幅度不大,这说明沼泽分布趋于破碎化,斑块的形状趋向于简单化,沼泽分布由边缘向中心收缩。     

Importance of geochemical transformations in determining submarine groundwater discharge-derived trace metal and nutrient fluxes

Seasonal (Spring and Summer 2002) concentrations of dissolved (<0.22 μm) trace metals (Ag, Al, Co, Cu, Mn, Ni, Pb), inorganic nutrients (NO₃, PO₄, Si), and DOC were determined in groundwater samples from 5 wells aligned along a 30 m shore-normal transect in West Neck Bay, Long Island, NY. Results show that significant, systematic changes in groundwater trace metal and nutrient composition occur along the flowpath from land to sea. While conservative mixing between West Neck Bay water and the groundwaters explains the behavior of Si and DOC, non-conservative inputs for Co and Ni were observed (concentration increases of 10- and 2-fold, respectively) and removal of PO₄ and NO₃ (decreases to about half) along the transport pathway. Groundwater-associated chemical fluxes from the aquifer to the embayment calculated for constituents not exhibiting conservative behavior can vary by orders of magnitude depending on sampling location and season (e.g. Co, 3.4 × 10²– 8.2 × 10³ μmol d⁻¹). Using measured values from different wells as being representative of the true groundwater endmember chemical composition also results in calculation of very different fluxes (e.g., Cu, 6.3 × 10³ μmol d⁻¹ (inland, freshwater well) vs. 2.1 × 10⁵ μmol d⁻¹(seaward well, S = 17 ppt)). This study suggests that seasonal variability and chemical changes occurring within the subterranean estuary must be taken into account when determining the groundwater flux of dissolved trace metals and nutrients to the coastal ocean.