基于氡同位素的平原湖荡枯水期湖水—地下水补排通量

水是人类生存之源,而湖荡被称为地球之“肾”,是河湖水系连接的关键缓冲节点,与人类生存和发展息息相关。长三角平原水系众多,河流纵横,天然湖泊与人工沟渠遍布,平原湖荡湖水与周边地下水的水力联系较为频繁,而地下水对湖泊水均衡贡献尚不明确,对平原湖荡地下水赋存和运移规律的认识不足。本研究以苏州吴江区元荡湖为研究对象,选取氡同位素作为湖水和地下水水力交换过程的示踪剂,建立氡箱模型,揭示元荡湖不同区段与地下水的水力联系过程和补给关系,并通过水位动态验证分析湖水—地下水交互关系。枯水期元荡湖水位和氡浓度空间分布特征指示研究区内地下水向湖水排泄,其中以湖泊西侧较为明显,地下水入流补给的氡为7.137×10⁶ Bq/d,输入量源项占比为90%,地下水流入量为4540.801 m³/d,地下水每日流入量对元荡湖水量的贡献率为2.551%。参数敏感性分析结果表明,风速与地下水²²²Rn活度为特别敏感参数,取值差异较大时会导致计算误差急剧增大,改善测点布置和提高模型参数精度能有效提高模型计算结果的准确性和可靠程度。借助氡同位素示踪方法,建立湖泊氡箱模型,是研究平原湖荡内地下水补、径、排特征的有效方法。本研究在一定程度上加深了对平原湖荡区域水量均衡的认识,有助于了解平原湖荡水均衡和水循环机制,为平原湖荡水资源开发利用与环境保护提供数据支撑。     

测氡仪标准仪器校准法的条件研究

利用AlphaGUARD测氡仪及AquaKIT水氡测量组件,使用水中溶解氡对FD-125测氡仪标配的两个闪烁室进行标准仪器校准。通过改变系统内体积,保证系统内AlphaGUARD测氡仪读数分别在1 000Bq/m~3,1 000~2 000Bq/m~3,……,10 000Bq/m~3等6个不同范围内。结果表明,当系统内氡体积活度大于1 000Bq/m~3时,所得到的K值相对于均值的偏差均≤5%,而且相对于氡气固体源校准得到的k值相对误差均≤5%;而当系统内氡体积活度小于1 000Bq/m~3时,所得到的K值相对于均值的偏差较大(10.2%与13.3%)。因此,认为标准仪器校准需要的条件是系统内氡体积活度1 000Bq/m~3,再根据氡在闭合系统内的水气平衡公式,得到台站开展标准仪器校准所需的最低水氡体积活度。本工作进一步研究了利用水中溶解氡加标准仪器的标准仪器校准技术代替氡气固体源校准的方法,而且基本确定了开展标准仪器校准所需条件,为下一步该校准方法规程的制定与方法推广奠定理论基础。     

太湖蚌类现存量及空间分布格局

于2016年10月和2017年10月对太湖全湖8个湖区129个样点的蚌类进行调查,分析蚌类的物种组成、现存量、空间分布及历史变化.共采集到蚌类704个个体,隶属8属14种.全湖蚌类平均生物量和密度分别为4.169±9.337 g/m²和0.164±0.386 ind./m²;各湖区蚌类平均生物量和密度差异较大,东部沿岸区生物量和密度最高,分别为14.975±16.743 g/m²和0.577±0.758 ind./m²;湖心区生物量和密度最低,仅为0.727±1.622 g/m²和0.029±0.071 ind./m².扭蚌（Arconaia lanceolata）、圆顶珠蚌（Unio douglasiae）和背角无齿蚌（Anodonta woodiana woodiana）为太湖现阶段的优势种.基于蚌类平均密度的聚类分析,8个湖区分为3类.与历史数据相比,太湖蚌类资源呈明显衰退趋势,现状不容乐观,需加强对太湖蚌类的保护和资源的有效管理.     

滇池大泊口水域水生植物种子库时空特征与恢复潜力

以滇池典型生态修复区——大泊口水域为研究对象,研究了富营养化高原湖泊种子库时空特征、种子库与地表覆盖水生植被及水环境的相关关系和恢复潜力.利用高密度样方原位观测与温室控制种子萌发实验相结合,基于2014-2016共3年的长期定位研究,分析湖泊平均种子库密度、分布格局及与覆盖水生植物Sørensen相似性关系,结果显示：年平均种子库形成率在20.35%~34.13%之间,种子库密度2014年为546.67粒/m²,2015年为826粒/m²,2016年为1682粒/m²,眼子菜科的篦齿眼子菜（Potamogeton pectinatus L.）、金鱼藻科的金鱼藻（Ceratophyllum demersum L.）等耐污种属对种子库构成和年增长率贡献较大;垂直方向上种子主要分布于深层底泥（5~30 cm）.随着在时间尺度上的延长,种子库分布更为广泛,且规模越来越大（其中500粒/m²以上规模的分布频率显示增多）.离散系数（V/m）与Lloyd平均拥挤指数（m^*）分析显示主要优势群丛（篦齿眼子菜等）为聚集分布,其余为均匀空间分布格局;种子库与水生植被关系评价指标Sørensen相似性系数（SC）研究显示,滇池大泊口平均SC=（0.3628±0.0265）,在湖泊湿地类型和草本群落植被类型属性上处于较低水平,即显示目前植物群落演替过程发生较快,耐污先锋种属在恢复进程上占据优势生态位,而历史优势种和对水环境要求较高的物种却未能规模萌发,一定程度上揭示了高原富营养化湖泊种子库中历史优势植被可恢复性的特征及难点.     

2022年第1期封面

丹江口水库,为南水北调中线工程唯一水源地,位于陕西、湖北、河南三省交界处的汉江上游,面积 1022 km²（水位 170m 时）,库容 290×10⁸m³,多年平均入库水资源量 374×10⁸m³(摄影：胡文波).     

云南程海浮游植物初级生产力的时空变化及其影响因子

2016年4月-2017年2月,采用黑白瓶法研究了云南程海单点（码头点位）浮游植物初级生产力的垂直分布及其季节变化,同时基于全湖9个点位的现场调查和生产力垂向归纳模型（VGPM）估算并探讨了程海浮游植物初级生产力的时空变化及其主要影响因子.结果显示,码头点位的年均（均值±标准误）水柱（0~3 m）总初级生产力（GPP_C）、净初级生产力（NPP_C）和呼吸消耗量（R_C）分别为5.40×10³±0.64×10³、2.36×10³±0.63×10³和3.06×10³±0.82×10³ mg O₂/（m²·d）;不论春夏季（4-8月）、秋冬季（9月-次年2月）还是全年,码头点位的单位生物量GPP（GPP/Chl.a）和单位生物量NPP（NPP/Chl.a）的最大值和最小值均分别出现在水下0.5 m和3.0 m处.经VPGM估算,程海全湖的初级生产力（PP_eu）年均值为6.54×10³±0.30×10³ mg C/（m²·d）（2.74×10³~18.62×10³ mg C/（m²·d））.PP_eu的时空变化方面,春夏季是PP_eu快速上升的时节,秋冬季PP_eu的月变化则呈波动状态,春夏季与秋冬季PP_eu无显著性差异;PP_eu整体空间异质性较弱,仅在降水最为充沛的7、8月表现出南北向的异质性,这与降水条件和流域营养盐输入的空间异质性有关.回归分析发现,虽然程海PP_eu的主要影响因子具有季节异质性,但不论春夏季、秋冬季还是全年,浮游植物生物量均是重要的影响因子,水温亦是春夏季的重要影响因子.     

藏南羊卓雍错湖面大气湍流特征观测分析

湍流运动是大气边界层的本质特征,是地表与大气之间能量和物质交换的主要方式.本文利用2016和2017年4-10月藏南羊卓雍错湖泊涡动观测资料,分析了湖面大气湍流方差和湍流特征量的统计和变化特征.结果表明：（1）不稳定层结下,三维风速分量和超声虚温、水汽密度、CO₂密度的无量纲标准差随稳定度变化符合Monin-Obukhov相似理论的"1/3"或"-1/3"次幂律,垂直风速的拟合效果最好;稳定层结下,除CO₂密度无量纲标准差与稳定度无明显关系外,其他量基本上满足相似性规律;中性条件下,以上物理量的无量纲标准差分别趋近常数：3.57、3.93、0.77、20.91、6.35和11.96.（2）水平方向平均湍流强度（0.60和0.58）大于垂直方向（0.13）,三维方向湍流强度与平均风速的变化呈显著负相关,相关系数分别为-0.39、-0.42和-0.34.（3）湖面湍流动能随风速呈线性增长,增长率达0.45 m/s;近中性层结时湍流动能最大,层结越稳定或不稳定湍流动能均减小.（4）湖泊下午到傍晚动量输送较强,13：00-22：30时间段平均动量通量达0.091 kg/（m·s²）;热量输送以潜热为主,潜热通量日平均值（77.3 W/m²）是感热通量（14.6 W/m²）的5.3倍,感热和潜热通量日变化峰值分别出现在5：30（22.4 W/m²）和16：00（106.6 W/m²）.     

秋季连续打捞蓝藻对水-气界面温室气体通量的影响

在巢湖西北半湖近岸带设置大型围隔研究秋季连续打捞蓝藻对湖泊温室气体通量的影响,应用YL-1000型大型仿生式水面蓝藻清除设备进行原位打捞蓝藻,通过便携式温室气体分析仪-静态箱法对大型围隔内水-气界面CH₄、CO₂通量特征及其影响因素进行观测.结果表明：对比未打捞区,蓝藻连续打捞下打捞区水体中叶绿素a（Chl.a）、悬浮物（SS）浓度不断下降,两者削减率分别为72%、85%,Chl.a、SS浓度分别下降到29.6±2.5 μg/L、12.5±1.2 mg/L,打捞对围隔内颗粒态物质去除效果十分明显;打捞过程中水体溶解性有机物（DOM）中微生物代谢类腐殖质（C1）、类蛋白（C3）显著下降趋势,打捞区C1、C3组分（0.18±0.02、0.06±0.01 RU）强度明显低于未打捞区（0.26±0.05、0.12±0.03 RU）,打捞能有效控制藻源性溶解性有机质释放.同时,打捞区水-气界面CH₄通量呈显著下降趋势,未打捞区CH₄通量平均值（17.473±1.514 nmol/（m²·s））为打捞区（7.004±4.163 nmol/（m²·s））近2倍,CH₄通量与Chl.a、C1、C3组分均呈显著正相关,水体中藻源性溶解态有机质对CH₄通量具有促进作用;打捞区CO₂释放通量呈显著上升趋势,打捞区CO₂吸收通量（-0.200±0.069 μmol/（m²·s））明显低于未打捞区（-0.344±0.017 μmol/（m²·s））,CO₂通量与Chl.a、温度均呈显著负相关.秋季打捞对CH₄、CO₂综合日平均通量减排量值为0.275±0.076 mol/（m²·d）（以CO₂当量计）.研究结果揭示了巢湖秋季连续打捞蓝藻过程对水-气界面温室气体具有显著减排作用,且能在一定程度上减缓蓝藻水华与湖泊富营养化、气候变暖之间的恶性循环,为湖泊碳循环和蓝藻水华灾害防控提供科学数据支撑和理论参考.     

冰封期乌梁素海沉积物-水界面氨氮的交换特征

为揭示冰封期氨氮（NH₄⁺-N）在沉积物-水界面的迁移机制及内源性营养盐对全湖污染的贡献,于2018年2月初在乌梁素海湖区7个采样点采集了上覆水体与沉积物样品,得到了冰封期上覆水体与沉积物间隙水中的NH₄⁺-N浓度,估算了沉积物-水界面NH₄⁺-N的扩散通量.结果显示,上覆水体中NH₄⁺-N浓度变化范围为0.55~1.60 mg/L,平均值为1.05 mg/L,0~5 cm表层沉积物间隙水中NH₄⁺-N浓度是上覆水体中的10倍以上,其变化范围为6.64~18.63 mg/L,平均值为11.92 mg/L.估算沉积物间隙水NH₄⁺-N向上覆水体的扩散通量为1.282~4.269 mg/（m²·d）,表明在湖水冻结过程中,底泥沉积物接纳了大量的可溶性污染物成为内源污染源,会在冰封稳定期、融冰期和融冰后的一段时间内成为湖水的主要污染源.     

太湖常见3种沉水植物附着生物的生物量及潜在反硝化速率

反硝化作用是将氮素从湖泊中彻底去除的重要途径之一,对于减轻湖泊富营养化具有重要意义。为了探究太湖沉水植物附着生物的生物量、潜在反硝化速率变化规律及其与环境因素的关系,在沉水植物生长盛期(7月),以太湖沉水植物主要分布区域东部湖湾作为采样区域,研究了太湖常见的3种沉水植物上附着生物的生物量,并利用乙炔抑制法测定沉水植物上附着生物的潜在反硝化速率,分析了太湖沉水植物附着生物的生物量及其潜在反硝化速率的主要影响因素。结果表明,太湖常见的3种沉水植物单位体表面积附着生物的生物量(AFDM)在0.037~0.789 mg/m²之间,均值为(0.389±0.261) mg/m²,沉水植物上附着生物的生物量存在空间差异,最大值出现在贡湖湾G1采样点((0.794±0.007) mg/m²),最小值出现在胥口湾X1采样点((0.041±0.005) mg/m²)。太湖沉水植物单位体表面积附着生物的潜在反硝化速率在3.09~58.80 μmol/(m²·h)之间,均值为(24.75±5.96)μmol/(m²·h)。太湖沉水植物附着生物的潜在反硝化速率存在空间差异,其中最大值出现在贡湖湾G1采样点((58.80±20.20) μmol/(m²·h)),最小值出现在胥口湾X1采样点((3.09±1.79) μmol/(m²·h))。相同条件下,沉水植物附着生物的生物量及潜在反硝化速率因植物种类的不同而存在差异,狐尾藻(Myriophyllum spicatum)上的附着生物的生物量及潜在反硝化速率显著高于苦草(Vallisneria natans)。相关性分析结果表明,沉水植物上附着生物的生物量与水体氮磷浓度相关。沉水植物附着生物的潜在反硝化速率与附着藻类的生物量、水体溶解有机碳及pH存在显著相关关系,这3种因子可以解释81.2%的沉水植物附着生物潜在反硝化速率变化,本研究结果可为进一步研究浅水湖泊脱氮过程及富营养化治理提供一定的理论依据。     

The use of radon as tracer in environmental sciences

Radon can be used as a naturally occurring tracer for environmental processes. By means of grab-sampling or continuous monitoring of radon concentration, it is possible to assess several types of dynamic phenomena in air and water. We present a review of the use of radon and its progeny at the University of Cantabria. Radon can be an atmospheric dynamics indicator related with air mass interchange near land-sea discontinuities as well as for the study of vertical variations of air parameters (average values of different types of stability: 131–580 Bq m^?3). Concerning indoor gas, we present some results obtained at Altamira Cave (Spain): from 222 to 6549 Bq m^?3 (Hall) and from 999 to 6697 Bq m^?3 (Paintings Room). Finally, variations of radon concentration in soil (0.3 to 9.1 kBq m^?3) and underground water (values up to 500 Bq l^?1) provide relevant information about different geophysical phenomena.     

Measurements of indoor radon concentrations and assessment of radiation exposure

In the past decade many international studies have established that the radioactive gas radon is responsible to a large extent for the radiation dose absorbed by the population. Consequently the Swiss Federal Health Office started and sponsored a research program called RAPROS (Radon Programm Schweiz, 1987–1991) to assess the relevant aspects of radon exposure in Switzerland.The average indoor radon concentration in Swiss living rooms is about 60–70 Bq m⁻³, this corresponds to an annual dose of about 2.2 mSv, but values largely exceeding 1000 Bq m⁻³ were also found. Often very strong temporal fluctuations of indoor radon concentrations were measured.The ground directly underneath buildings is the main radon source of indoor radon. The material properties that influence the radon production and transport in soils are: radium content, emanating coefficient and soil gas permeability; among them only the last one can vary over many orders of magnitude. The permeability is consequently the decisive factor that enables radon transport in the subsurface. To characterize the radon potential of soils a radon availability index (rav) was introduced.Our investigations have also shown that in karst systems the radon concentration in the air is often increased to 10–100 times higher than in buildings. This radon-charged air is able to travel over considerable distances through faults and cavities in the underground and reach living rooms built over karstified areas.     

A natural tracer investigation of the hydrological regime of Spring Creek Springs, the largest submarine spring system in Florida

This work presents results from a nearly two-year monitoring of the hydrologic dynamics of the largest submarine spring system in Florida, Spring Creek Springs. During the summer of 2007 this spring system was observed to have significantly reduced flow due to persistent drought conditions. Our examination of the springs revealed that the salinity of the springs' waters had increased significantly, from 4 in 2004 to 33 in July 2007 with anomalous high radon (²²²Rn, t_1/2=3.8 days) in surface water concentrations indicating substantial saltwater intrusion into the local aquifer. During our investigation from August 2007 to May 2009 we deployed on an almost monthly basis a continuous radon-in-water measurement system and monitored the salinity fluctuations in the discharge area. To evaluate the springs' freshwater flux we developed three different models: two of them are based on water velocity measurements and either salinity or ²²²Rn in the associated surface waters as groundwater tracers. The third approach used only salinity changes within the spring area. The three models showed good agreement and the results confirmed that the hydrologic regime of the system is strongly correlated to local precipitation and water table fluctuations with higher discharges after major rain events and very low, even reverse flow during prolong droughts. High flow spring conditions were observed twice during our study, in the early spring and mid-late summer of 2008. However the freshwater spring flux during our observation period never reached that reported from a 1970s value of 4.9×10⁶ m³/day. The maximum spring flow was estimated at about 3.0×10⁶ m³/day after heavy precipitation in February-March 2008. As a result of this storm (total of 173 mm) the salinity in the spring area dropped from about 27 to 2 in only two days. The radon-in-water concentrations dramatically increased in parallel, from about 330 Bq/m³ to about 6600 Bq/m³. Such a rapid response suggests a direct connection between the deep and the surficial aquifers.     

Radon and remediation measures near Băiţa-Ştei old uranium mine (Romania)

B?i?a-?tei mine is an open pit mine in NW Romania (West Carpathian Mountains). It was the largest surface uranium deposit in the world. Two means of uranium transport and dissemination were used over time. The first was the natural way, represented by transportation of geological sediments by Cri?ul-B?i?a River that crosses the B?i?a surface deposit. These sediments were used as building materials (stone, gravel, sand). The second way was related to the people living in this valley, who used also the uranium waste as building material. The preliminary indoor radon concentrations measured in the buildings ranged from 40 to 4000 Bq m^?3 with a mean value of 241 Bq m^?3. A focused radon survey facilitated the selection of 20 houses with the highest indoor radon that were therefore proposed for remediation. To find the radon sources of these houses, systematic investigations on radon were performed. The remedial measures for these 20 houses were tested on a chosen pilot house.     

Sub‐surface water contribution to recession flow in a mountain headwater stream system based on single monitoring campaign

Discharge in mountain streams may be a mixture of snowmelt, water from surface runoff, and deep return flow through valley bottom alluvia. We used δ¹⁸O and δ²H, solute concentrations, and ²²²Rn to determine water sources of a headwater stream located at the McDonald Creek watershed, Glacier National Park, USA, during summer recession flow period. We analysed minimal water isotope ranges of ?17.6‰ to ?16.5‰ and ?133‰ to ?121‰ for δ¹⁸O and δ²H, respectively, potentially due to dominance of snow‐derived water in the stream. Likewise, solute concentrations measured in the stream through the watershed showed minimal variation with little indication of subsurface water input into the stream. However, we observed ²²²Rn activities in the stream that ranged from 39 to 2646 Bq/m³ with the highest value measured in middle of the watershed associated with channel constriction corresponding to changes in local orientation of underlying rocks. Downstream from this point, ²²²Rn activity decreased from 581 to 117 Bq/m³ in a series of punctuated steps associated with small rapids and waterfalls that we hypothesized to cause radon degassing with a maximum predicted loss of 427 Bq/m³ along a 400 m distance. Based on mass balance calculations using ²²²Rn activity values, streamflow, and channel characteristics, we estimated that groundwater contributed between 0.3% and 29% of total flow. Overall, we estimated a 5.9% of groundwater contribution integrated for stream reach measured at McDonald Creek during recession flow period. Finally, a lower mean hyporheic flux of 14 m³/day was estimated compared to the groundwater flux of 70 710 m³/day. These assessments highlight the potential for radon as a conservative tracer that can be used to estimate subsurface water contribution in mountain streams within a complex geologic setting. Copyright © 2015 John Wiley & Sons, Ltd.     

氡气固体源的准确度、稳定性和重复性及其影响因素研究

通过实验、理论分析和结构解剖，对地震前兆观测台网中广泛使用的氡气固体源的准确度、稳定性和重复性进行了研究和论证，并找出了其主要影响因素是密封性、渗漏和堵塞，在此基础上给出了氡气固体源在使用过程中的维护对策。     

Measurement of radon potential from soil using a special method of sampling

Soil radon gas and/or its exhalation rate are used as indicators for some applications, such as uranium exploration, indoor radon concentration, seismic activity, location of subsurface faults, etc., and also in the studies where the main interest is the field verification of radon transport models. This work proposes a versatile method for the soil radon sampling using a special manner of pumping. The soil gas is passed through a column of charcoal by using passive pumping. A plastic bottle filled with water is coupled to an activated charcoal column and the flow of water through an adjustable hole made at the bottom of bottle assures a controlled gas flow from the soil. The results obtained for the activity of activated charcoal are in the range of 20–40 kBq/m³, for a depth of approximately 0.8 m. The results obtained by this method were confirmed by simultaneous measurements using LUK 3C device for soil radon measurements. Possible applications for the estimation of radon soil potential are discussed.     

Localizing and quantifying groundwater-surface water interactions at different scales: A tracer approach at the River Moselle,Germany

Groundwater-surface water interactions (GSI) connect rivers and streams with riparian areas and the adjacent aquifer. Although these interactions exert a substantial control of quantity and quality of both groundwater and surface water, knowledge on GSI along rivers at the regional scale, particularly for inland waterways, is still limited. We investigated GSI along the river Moselle, an important federal inland waterway in Germany, by using radon and tritium to identify gaining (water flux from the aquifer to the surface water) and losing (water flux from the surface water to the aquifer) stream conditions, respectively. Gaining stream conditions were identified by continuously measuring radon along the river during boat surveys with a high spatial resolution (every 2 km) during intermediate (October 2020) and near low flow conditions (August/September 2021). The tritium concentrations in surface water and groundwater and the resulting tritium inventories were used to characterize losing stream conditions Monthly tritium inventories from 2017 to 2022 revealed a mean loss for the whole period of 20.3 % and a mean gain of 21.8%. Both were probably triggered by a combination of losing stream conditions and flood-induced mass transfer of water from the aquifer back into the river as well as discharge fluctuations. At the investigated site Lehmen there were direct indications of an influence of surface water due to elevated tritium concentrations in the groundwater (up to 13.3 Bq L⁻¹). Using radon mass balance modelling, good agreements of simulated versus measured radon data with respect to two groundwater end-member scenarios were obtained during intermediate flow (Spearman's ρ: 0.97 and 0.99; MAE: 10.1 and 3.4 Bq L⁻¹) and near low flow (Spearman's ρ: 0.97 and 0.99; MAE: 11 and 6.5 Bq L⁻¹). Considerable groundwater inflow was limited to the meander of Detzem, where cumulated groundwater inflow of about 19 m³ s⁻¹ (9.5% of total discharge) and 4.2 m³ s⁻¹ (3.8% of total discharge) was simulated during intermediate and near low flow, respectively. However, the groundwater inflow was relatively low compared to alpine streams, for example. The study will help to better identify and quantify GSI at the regional scale and provide methodological guidance for future studies focusing on inland waterways.     

地震氡观测计量溯源初步探究

根据氡观测仪的氡室校准和氡气固体源校准两种校准方式的实验结果, 讨论了使用标准仪器校准氡观测仪器的可靠性问题。 用国际公认的计量传递仪器AlphaGUARD P2000Pro或AlphaGUARD P2000F测氡仪作为氡气溯源仪器, 对九江地震台FD-125氡钍分析器的三个闪烁室进行了氡室校准、 氡气固体源校准和仪器校准三种方法实验, 得到标准仪器校准、 氡气固体源校准得出K值相对氡室校准结果偏差均小于6%, 结果表明, 三种方法的校准结果均符合目前氡观测计量溯源技术要求, 能达到与国家氡计量刻度相统一目的。