Spatial patterns of groundwater‐lake exchange – implications for acid neutralization processes in an acid mine lake

Exchange of groundwater and lake water with typically quite different chemical composition is an important driver for biogeochemical processes at the groundwater‐lake interface, which can affect the water quality of lakes. This is of particular relevance in mine lakes where anoxic and slightly acidic groundwater mixes with oxic and acidic lake water (pH < 3). To identify links between groundwater‐lake exchange rates and acid neutralization processes in the sediments, exchange rates were quantified and related to pore‐water pH, sulfate and iron concentrations as well as sulfate reduction rates within the sediment. Seepage rates measured with seepage meters (?2.5 to 5.8 L m^‐2 d^‐1) were in reasonable agreement with rates inverted from modeled chloride profiles (?1.8 to 8.1 L m^‐2 d^‐1). Large‐scale exchange patterns were defined by the (hydro)geologic setting but superimposed by smaller scale variations caused by variability in sediment texture. Sites characterized by groundwater upwelling (flow into the lake) and sites where flow alternated between upwelling and downwelling were identified. Observed chloride profiles at the alternating sites reflected the transient flow regime. Seepage direction, as well as seepage rate, were found to influence pH, sulfate and iron profiles and the associated sulfate reduction rates. Under alternating conditions proton‐consuming processes, for example, sulfate reduction, were slowed. In the uppermost layer of the sediment (max. 5 cm), sulfate reduction rates were significantly higher at upwelling (>330 nmol g^‐1 d^‐1) compared to alternating sites (<220 nmol g^‐1 d^‐1). Although differences in sulfate reduction rates could not be explained solely by different flux rates, they were clearly related to the prevailing groundwater‐lake exchange patterns and the associated pH conditions. Our findings strongly suggest that groundwater‐lake exchange has significant effects on the biogeochemical processes that are coupled to sulfate reduction such as acidity retention and precipitation of iron sulfides. Copyright © 2012 John Wiley & Sons, Ltd.     

Application of FY-2C Cloud Drift Winds in a Mesoscale Numerical Model

Statistical tests and error analysis of cloud drift winds(CDWs) from the FY-2C satellite were made by using radiosonde observations.According to the error characteristics of the CDW,a bias correction using the thermal wind theory was applied in the data quality control.The CDW data were then assimilated into the GRAPES-meso model via the GRAPES-3DVar.A torrential rain event that occurred in northwestern China during 1-2 July 2005 was simulated.The results indicate that the CDW data were mainly distribute...     

Wet deposition of excess sulfate at Macquarie Island, 54° S

Annual wet deposition of excess sulfate at Macquarie Island has been estimated from 5 months of rainwater composition data covering the Austral summer of 1985/86. The resulting figure of 2.1±0.6 mmol/m²/yr is at the low end of previous estimates of maritime excess sulfate deposition by precipitation. Within estimated uncertainty limits this figure is consistent with the DMS emission flux which would be predicted for latitude 50°–60° S, based solely on available Northern Hemispheric DMS measurements.Temporarily at the International Meteorological Institute, Stockholm University, S-106 91, Stockholm, Sweden.     

四川省宁南县城后山泥石流激发雨强

根据宁南县城后山垂直剖面观测资料，对本区降雨的垂直变化及泥石流激发雨强作了探讨。当地暴雨泥石流发生所需的１０分钟雨强ｉ＿（１０ｍｉｎ）和前期降水量Ｐａ组合为：：ｉ＿（１０ｍｉｎ）≥１５ｍｍ∩Ｐａ≥５０ｍｍ，或ｉ＿（ｍｉｎ）≥１０ｍｍ∩Ｐａ≥６５ｍｍ，或ｉ＿（１０ｍｉｎ）≥５ｍｍ∩Ｐａ≥９０ｍｍ。超过上述各组合值就有可能暴发泥石流。     

盐卤硼酸盐化学Ⅹ Ⅹ Ⅴ Ⅱ盐湖卤水酸化过程中硼酸生长速率

本文提出了一种用激光散射跟踪溶液中粒子粒度在不同时间的分布，求取粒子生长速率的简便而可行的方法，得到了大柴旦盐湖卤水在硫酸酸化过程中硼酸晶体的生长速率，并提出解决酸法提础工艺中所得硼酸晶体粒度太小的方法。     

Formic and acetic acids in atmospheric condensate in Wilmington,North Carolina

Formic and acetic acids occurred in atmospheric condensate with concentrations similar to rainwater collected in Wilmington, North Carolina, during the sampling period from June to October of 1990. Atmospheric concentrations of these acids (calculated from the condensate concentrations) were higher in continental versus maritime air masses. Concentrations of formic and acetic acids were correlated with each other in both condensate and air. Traffic was a source of acetic acid and of bisulfite to atmospheric condensate in this study.     

9012台风倒槽结构与暴雨中尺度系统

利用高空资料、地面资料和红外卫星云图资料,对发生在浙江中北部的9012台风倒槽暴雨的机制进行分析,揭示了该台风倒槽的结构和暴雨的环境场。并进一步研究了产生暴雨的中尺度暴雨云团及其周围的垂直气流分布与地面降水的对应关系。对暴雨云团所对应的高、中、低(地面)层系统亦进行了分析。     

9216号热带风暴的初步分析

对9216号热带风暴在9月1日02时中心分裂的原因,作了初步探讨,认为东南低空急流使热带风暴倒槽区的气旋性环流加强,以及低涡的吸引合并,是产生新中心的原因。青岛产生大暴雨的条件,是充沛的水汽,强烈的上升运动和长波槽东移影响。     

1990 年京津冀三次暴雨的分析

本文分析了1990年京津冀地区三次暴雨过程，结果发现:（1）三次暴雨是属于相伴有冷锋的高空槽影响的暴雨；（2）暴雨开始前约10小时雨区的西南方存在湿有效能量高能舌，高能舌的西方和北方有能量和水汽的积聚；（3）对流层低层的锋生和地形对气流的抬升作用是触发暴雨开始的直接原因。     

Interpretation of210Pb profiles and verification of the CRS dating model in PIRLA project lake sediment cores

This paper reports results and analysis of²¹⁰Pb-activity measurements in 51 lake-sediment cores from 32 lakes in the four PIRLA (Paleoecological Investigations of Recent Lake Acidification) project regions (Adirondack Mountains [New York], Northern New England, Northern Florida, and the Northern Great Lakes States). General application of the Constant Rate of Supply (Constant Flux) model for²¹⁰Pb dating is valid for lakes in the PIRLA study, although application of the model is equivocal in a few lakes.²¹⁰Pb inventories and profiles are replicable among closely spaced cores within a lake. Specific²¹⁰Pb activity in surface sediments is negatively correlated with bulk sediment accumulation rate in seepage lakes, but not in drainage lakes. Drainage lakes with lower pH have lower unsupported²¹⁰Pb inventories in sediments, but the relationship does not occur in seepage lakes.²¹⁰Pb profiles in only seven of the cores, all from either the Adirondacks or the northern Great Lakes states, exhibit exponential decay curves. Deviations from an exponential profile include a flattening of the profile in the top few cm or excursions of one or a few measurements away from an exponential curve.²¹⁰Pb dates typically agree with other chronostratigraphic markers, most of which are subject to greater uncertainty. Several hypotheses, including sediment mixing, hydrologic regime, sediment focusing, and acidification, are proposed to explain variation of²¹⁰Pb distribution among lakes and regions. Hydrologic factors exert control on unsupported²¹⁰Pb inventories in PIRLA lakes, and there is a strong focusing effect in drainage lakes but a weak focusing effect in seepage lakes.This is the third of a series of papers to be published by this journal following the 20^th anniversary of the first application of²¹⁰Pb dating of lake sediments. Dr P. G. Appleby is guest editing this series.