Gas emission from active fault zones around the Jilantai faulted depression basin and its implications for fault activities
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摘要: 为了研究吉兰泰断陷盆地周缘断裂带气体排放及其对断层活动性的指示意义,在盆地周缘4条活动断裂上布设了5条土壤气测量剖面和1条电磁测量剖面,观测了土壤气中Rn,Hg和CO2的浓度、释放通量和地电阻率,对各测量剖面进行了土壤化学组分分析,计算得到了断层活动性相对指数KQ。研究结果显示:土壤气体CO2和Rn受渗透性较低的粉砂土阻挡,主要沿结构破碎的断层上盘逃逸,并形成浓度高峰;吉兰泰盆地南缘土壤气Rn,Hg和CO2的浓度和释放通量最高,可能与盆地西南缘花岗岩中U和Ra的运移以及盆地南缘碳酸盐岩的分解有一定的关系。各测量剖面的断层活动性相对指数KQ值的变化特征表明,正断层和逆断层的KQ值大于走滑断层,且巴彦乌拉山山前断裂上的KQ值最高,揭示其活动性最强,有可能是地震发生的潜在危险区。Abstract: Soil gases from fault zones are good indicators of tectonic and seismic activities, to which many seismologists and geochemists have been paid much attention. Five measuring sections for soil gas and one for earth resistivity were designed on the four active faults around the Jilantai basin, northwestern China. The data of earth resistivity, concentration and flux of soil gases Rn, Hg and CO2 were attained, and the chemical compositions of soil were analyzed in all sections and the relative index KQ of fault activity was calculated. All the results showed that soil gases CO2 and Rn were blocked by sandy soil layers with low permeability and escaped along the hanging wall of the faults with broken structures, easily forming concentration peaks. High concentrations and fluxes of Rn, Hg and CO2 were distributed in the southern margin of the Jilantai basin, which might be related to the migration of U and Ra in granites in southwestern margin of the basin and the decomposition of local carbonate rocks in south margin of the basin. The variation characteristics of relative index KQ of fault activity in each section indicated normal and reverse faults with higher KQ values than strike-slip faults. The maximum KQ value was observed in the piedmont fault of Bayanwula mountains, probably indicating that this fault is of the strongest activity and is also a potential area of high seismic hazards.
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Keywords:
- Jilantai faulted depression basin /
- fault zone /
- soil gases /
- geochemistry /
- flux /
- fault activity
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引言
大量的地震震害调查及地形地震动观测记录研究发现,山地、丘陵地区对地震波会有显著的放大现象,且狭长、高耸的山体会出现共振及偏振旋转现象,位于山体地形的结构震害程度远大于附近平坦地形(胡聿贤等,1980;Bard,Tucker,1985;Çelebi,1987;Geli et al,1988;Bonamassa,Vidale,1991;Bouchon,Barker,1996;章文波等,2001;薄景山等,2021)。由于山体地形场地条件下的强震动记录较少,关于地震动的山体地形效应尤其是偏振效应研究较为薄弱。随着西部大开发战略的实施,在山区需要兴建大量桥梁、隧道和水电站等基础设施,因此山体地形地震动效应研究对于山区重大工程抗震设计参数的确定尤为重要。
关于地形效应的研究主要有三种途径:解析分析、数值模拟计算及地形台阵观测。解析分析以波函数展开法为主(Wong,Trifunac,1974;袁晓铭,廖振鹏,1996;梁建文等,2006),由于该方法计算模型简单,很难得到三维复杂场地的地震响应,常用于检验数值模拟计算的精度及收敛性;数值模拟主要包括有限差分法(Tessmer,Kosloff,1994;王铭锋等,2017)、有限元法(刘晶波,1996;Kurita et al,2005;章小龙等,2017)、有限元-有限差分法(李小军等,1995,荣棉水等,2009)、边界元法(巴振宁等,2019)及谱元法(周红等,2010)等,数值模拟计算方法发展迅速,但是其研究对象建模的合理性及算法的选取很难控制,计算结果与实际值往往有所偏差;地形台阵观测方法是对复杂地形上台阵记录到的地震动时程进行研究,该方法是研究场地地形效应最直观、最真实可靠的方法。
所谓地形效应,指的是地形对地震波的传播路径和传播特点产生的影响,地形的不规则性和复杂性使得地震波在地形场地的传播过程中发生反射、衍射和折射等现象,从而影响地震波的传播速度、振幅和频谱等。基于地形台阵强震动记录,国内外学者进行了许多研究,例如:Bouchon (1973)对帕科伊马大坝加速度计记录的加速度数据分析表明,峰值加速度(peak ground acceleration,缩写为PGA)由于地形效应被放大30%—50%,对山脊和凹陷地形的研究发现,地震动在通过山体时,放大效应发生在顶部,衰减区域出现在凹陷地形底部;Çelebi (1991)基于强震动记录研究发现,地震能量由于地形的影响而被放大,并指出放大效应与震源的强度和地形构造相关;Pedersen等(1994)、Kurita等(2005)和唐晖等(2012)利用谱比法将山体地形场地的强震动记录分析结果与数值模拟结果进行了对比研究,发现当频率在5 Hz以下时二者有很好的一致性,频率大于5 Hz时,数值模拟结果会小于强震记录分析结果;姚凯等(2009)和孙崇绍等(2011)对局部孤突地形的地震动峰值加速度的研究也发现,加速度随局部地形的高度增加而增大;王海云和谢礼立(2010)、王伟(2011)及王伟等(2015,2016)用傅里叶谱谱比法(Fourier spectral ratio,缩写为FSR)对地震动记录进一步研究发现,地震动的放大效应与输入地震动在各频段的频率含量有关,低频段对地形放大效应不明显,当频率大于1 Hz时,地形放大效应显著,且两水平向的地震动放大效应也有所差别;Vidale等(1991)及Bouchon和Barker (1996)对地形台阵记录的研究表明,地震动传播到狭长的山体地形时会出现共振及偏振旋转现象;周正华等(2009)对自贡西山地形台阵各测点的观测资料进行研究,结果表明,两水平向的地震动明显强于竖直向的,且东西向的地震动放大效应最明显;周港圣等(2022)基于汶川地震主震及余震的地形效应观测台阵记录对山体地形效应进一步研究发现,地震动的地形效应会随着山体地形的变化而改变,且地形效应存在方向性,即会使山体发生偏振。前人对这种方向性的研究只是粗略的比较了两水平向的放大系数,并未全面考虑山体地形其它方位的放大程度,山体地形的偏振效应可能会发生在山体的其它方位,且由于地形台阵观测资料的缺乏,以往基于实际山体地形台阵记录的研究较少。基于此,本文拟利用汶川地震后窦圌山地形效应观测台阵获得的余震记录,绘制9次余震傅里叶谱谱比和质点运动轨迹图,并将强震动记录以10°为单位进行分解,对各分解角度下的傅里叶谱谱比、峰值加速度比等要素进行分析,以期为研究山体地形地震动偏振效应的影响机制提供参考。
1. 窦圌山地形台阵及数据
窦圌山地形效应观测台阵(以下简称窦圌山地形台阵)位于四川省江油市武都镇,窦圌山地质构造复杂,主要成分为砾岩,山体顶部走向为北偏东,坡度约为40°—50°。汶川地震后,地震科考人员在山体的坡顶及坡脚分别布设了一台强震仪,用于观测地震动山体地形效应。坡顶和坡角观测点的高程分别为1 058.0 m和995.0 m,二者高差为63.0 m,山体剖面及观测点高程见图1。
汶川地震后,该地形台阵共记录到9次余震数据,各余震的震中位置如图2所示,各余震的震级、震中距及方位角等信息列于表1。
表 1 窦圌山观测台阵观测到的汶川MS8.0地震的9次余震信息Table 1. Information of nine aftershocks of Douchuan mountain observation array序号 MS 震中距/km 东经/° 北纬/° 方位角/° 序号 MS 震中距/km 东经/° 北纬/° 方位角/° 1 5.0 46.65 104.90 32.32 11 6 3.5 27.55 104.62 32.10 321 2 4.6 30.67 104.56 32.09 311 7 4.1 24.35 104.62 32.06 314 3 6.1 118.28 105.47 32.82 31 8 3.4 22.00 104.86 32.10 13 4 5.9 24.08 104.64 32.07 319 9 5.4 32.83 104.59 32.14 322 5 5.2 26.83 104.67 32.12 331 注:方位角为震中位置相对于山体坡顶测点的角度。 2. 研究方法
地震动主要受震源效应、传播路径效应和场地效应的影响,定义某一测点的地震动傅里叶谱为$A ( f ) $,$A ( f ) $可表示为震源函数$S ( f ) $、传播路径函数$T ( f ) $、场地效应函数$R ( f ) $三者的乘积(王海云,谢礼立,2010;王伟,2011),即
$$ A ( f ) =S ( f ) T ( f ) R ( f ) \text{,} $$ (1) 式中f为频率。$R ( f ) $用下式表示:
$$ R ( f ) =r ( f ) t ( f ) \text{,} $$ (2) 式中,$r ( f ) $为除地形效应之外的其它场地效应,$t ( f ) $为地形效应。则坡脚场地地震动傅里叶谱$A_{1} ( f ) $为
$$ {A}_{1} ( f ) ={S}_{1} ( f ) {T}_{1} ( f ) {r}_{1} ( f ) {t}_{1} ( f ) \text{,} $$ (3) 坡顶场地地震动傅里叶谱${A}_{2} ( f ) $可表示为
$$ {A}_{2} ( f ) ={S}_{2} ( f ) {T}_{2} ( f ) {r}_{2} ( f ) {t}_{2} ( f ) . $$ (4) 假设${S}_{1} ( f ) ={S}_{2} ( f ) $,${T}_{1} ( f ) = {T}_{2} ( f ) $,${r}_{1} ( f ) ={r}_{2} ( f ) $,则傅里叶谱谱比的含义是坡顶与坡脚地形效应的传递函数,表征的是坡体的振动特性,即
$$ \frac{{A}_{2} ( f ) }{{A}_{1} ( f ) }=\frac{{t}_{2} ( f ) }{{t}_{1} ( f ) } . $$ (5) 从上面的假设可以看出,在一次地震中,若参考场地和台站测点二者的间距与震中距相比很小,传播路径效应可以忽略不计,则${S}_{1} ( f ) ={S}_{2} ( f ) $和${T}_{1} ( f ) ={T}_{2} ( f ) $两个假设成立,若想满足${r}_{1} ( f ) ={r}_{2} ( f ) $,则坡脚测点和参考场地的地质环境需保持一致,还需保证坡脚测点不受山体地形的影响,实际情况下此种情况很难存在,故一般将参考点布设在观测山体的底部。
有学者将两水平向记录以某一固定角度依次分解,研究不同角度下的多个共振频率,例如,Vincenzo (2017)利用环境噪声记录进行了不同角度下放大效应的研究。本文用该方法对9次余震坡顶及坡脚的东西向和南北向地震动记录进行滤波和基线校正,在0°—180°之间以10°为单位沿逆时针方向进行分解合成,图3给出了东西向和南北向地震动时程分解合成示意图。
实际山体的走向角度为N47°E、横向角度为北偏西43°,分解方法见下式:
$$ P ( \theta ) =\mathrm{E}\mathrm{W}\cdot \mathrm{c}\mathrm{o}\mathrm{s}\theta + \mathrm{N}\mathrm{S}\cdot \mathrm{s}\mathrm{i}\mathrm{n}\theta \text{,} $$ (6) $$ T ( \theta ) =\mathrm{N}\mathrm{S}\cdot \mathrm{c}\mathrm{o}\mathrm{s}\theta -\mathrm{E}\mathrm{W}\cdot \mathrm{s}\mathrm{i}\mathrm{n}\theta \text{,} $$ (7) 式中,θ为10°,20°,30°,···,180°,$P ( \theta ) $和$T ( \theta ) $分别为两水平向记录以一定角度沿逆时针方向分解得到的新的两条地震动时程。
3. 窦圌山汶川余震强震动记录分析
3.1 傅里叶谱谱比分析
对窦圌山余震的傅里叶谱谱比进行分析,分别计算9次余震东西向和南北向的坡顶/傅里叶谱谱比,相应的傅里叶谱谱比云图见图4。对于东西向谱比云图(图4a),山体的自振频率主要分布在1.3—2.8 Hz,7.1—10.1 Hz,11.5—16.0 Hz范围内;由南北向谱比云图(图4b)可见,山体的自振频率主要分布在1.8—4.2 Hz和9.2—14.2 Hz范围内。由9次余震东西向和南北向的傅里叶谱谱比平均值(图5)可以看出,9次余震两水平向记录的傅里叶谱谱比平均值曲线与单次余震傅里叶谱谱比曲线的一致性较好。由图4和图5可见,山体的自振频率并不唯一,傅里叶谱谱比极大值会出现在不同的频段,山体存在明显的多阶性;由表1可知,各余震的震源、震级、震中距、传播路径等存在显著差异,但是各余震谱比曲线的一致性很好,说明山体的自振频率与山体本身的几何形状等因素有关。合并9次余震两水平向的自振频率可以发现,1.0—4.0 Hz为山体的低阶振型,9.0—15.0 Hz为山体的高阶振型。
3.2 质点运动轨迹图分析
窦圌山台阵记录到的汶川地震9次余震的质点运动轨迹图见图6 (x,y轴分别代表山体的东西向和南北向,正值分别为东向和北向),可以看出窦圌山在不同余震作用下的运动轨迹有明显的差别,说明不同的余震会使山体在不同方向上发生偏振旋转现象,在1,3,4,9号余震作用下,坡脚和坡顶均在横向方向发生偏振运动;在2,5,6号余震作用下,坡脚和坡顶均在走向方向发生偏振运动;在7,8号余震作用下,坡脚与坡顶分别在山体走向和横向发生偏振,质点运动优势方向不一致。
3.3 峰值加速度偏振效应分析
为了研究9次余震质点运动轨迹图的偏振效应出现在不同方位的原因,对9次余震坡脚及坡顶的地震动数据进行分解合成,方法见图3和式(6),(7)。将分解合成后同一分解角度的坡顶峰值加速度与坡脚峰值加速度相比,所得比值列于表2。通过表2可以分析9次余震峰值加速度的偏振效应,同时绘制了9次余震坡顶/坡脚测点各分解角度峰值加速度放大系数图(图7)。由表2和图7可知,1,2,3,4,8号余震的放大系数最大值均出现在山体横向及其附近,5次余震放大系数最大值出现的方位与各自质点运动轨迹图偏振方位基本一致;5,6,7号余震的放大系数最大值出现在山体走向及其附近,3次余震放大系数最大值出现的方位与各自质点运动轨迹图偏振方位相一致;9号余震放大系数最大值出现在山体走向和横向上;故9次余震各分解角度的PGA放大系数具有明显的偏振效应。
表 2 9次余震坡顶/坡脚测点各分解角度峰值加速度PGA放大系数Table 2. PGA amplification factor for the decomposition angles of the nine aftershocks at the top/foot of the slope measurement points分解角度/° PGA放大系数 余震1 余震2 余震3 余震4 余震5 余震6 余震7 余震8 余震9 10 0.765 0.767 1.048 0.881 1.148 1.620 0.704 0.721 1.051 20 0.722 0.697 1.016 0.901 1.159 1.744 0.820 0.745 0.904 30 0.671 0.761 0.910 0.907 1.170 1.747 0.912 0.777 0.796 40 0.697 0.836 0.801 0.841 1.176 1.394 0.984 0.822 0.709 50 0.711 0.913 0.825 0.783 1.041 1.072 0.895 0.851 0.624 60 0.773 1.015 0.852 0.864 0.903 0.832 0.836 0.843 0.521 70 0.888 1.163 0.843 0.948 0.770 0.629 0.791 0.828 0.459 80 0.998 1.278 0.791 1.053 0.695 0.592 0.784 0.893 0.451 90 1.095 1.375 0.739 1.172 0.754 0.579 0.844 1.020 0.453 100 1.196 1.418 0.723 1.334 0.747 0.579 0.901 1.098 0.456 110 1.154 1.446 0.786 1.323 0.712 0.580 0.851 1.120 0.465 120 1.045 1.471 0.860 1.262 0.680 0.580 0.792 1.141 0.484 130 0.981 1.554 0.937 1.239 0.644 0.582 0.737 1.165 0.549 140 0.930 1.375 1.049 1.268 0.668 0.680 0.683 1.191 0.687 150 0.893 1.228 1.079 1.331 0.717 0.895 0.627 1.081 0.852 160 0.863 1.091 1.075 1.320 0.772 1.188 0.621 0.898 0.879 170 0.834 0.976 1.064 1.206 0.812 1.372 0.638 0.743 0.919 180 0.801 0.870 1.057 0.964 1.017 1.493 0.659 0.682 1.114 3.4 傅里叶谱分析
对各余震坡脚测点输入地震动的傅里叶谱图进行分析,研究9次余震质点运动轨迹图的偏振效应出现在不同方位的原因。由图8可知,1,3,4,9号余震频率丰富的频段主要集中在0.5—4.0 Hz的低频段及5.0—11.0 Hz的中高频段,因此容易激发山体的低阶及高阶振型;2,5,6,7,8号余震频率丰富的频段主要集中在4.0—9.0 Hz中高频段,容易激发山体的高阶振型。
为了更深入地研究山体地形发生偏振效应的影响机制,采用与峰值加速度分解合成相同的方法对9次余震地震动记录进行处理并绘制各分解角度的傅里叶谱谱比云图(图9)。由图9可知,各余震在不同分解角度下的谱比极大值所在的频段比较接近,均分布在0.8—2.8,7.8—10.2,11.5—16 Hz频段,但是各余震谱比极大值所在的角度范围有所不同。对余震1,3,4,9分析可知,在0.8—2.8 Hz低频段,傅里叶谱谱比最大值对应的分解角度在110°—160°范围,即山体横向方位;在7.8—10.2 Hz中高频段,傅里叶谱谱比最大值对应的分解角度在30°—60°范围,即山体走向方位;说明4次余震在低频和中高频段都含有丰富的能量,容易同时激发山体的低阶和高阶振型,导致山体振动具有明显的偏振效应,该现象与各自质点运动轨迹图及峰值加速度的偏振方位大致相同。对余震2,5,6,7,8分析可知,这5次余震的地震能量主要集中在中高频段,谱比最大值对应的分解角度集中在30°—60°范围,即山体走向方位,该角度范围更容易激发山体的高阶振型,该现象也与各自质点运动轨迹图及峰值加速度的偏振方位大致相同。
4. 讨论与结论
基于窦圌山地形台阵记录到的汶川地震9次余震信息,利用傅里叶谱谱比法研究了山体地形地震动偏振效应,得出如下结论:
1) 同一山体,9次余震的傅里叶谱谱比曲线基本一致,主要集中在1.0—4.0 Hz低频段及9.0—15.0 Hz中高频段,说明山体具有明显的多阶性,且山体的振动特性与山体本身的几何形状、地质构造等因素有关。
2) 在9次余震作用下,山体的质点运动轨迹图和分解合成后的峰值加速度放大系数在山体横向及走向上均具有明显的偏振效应,且二者的偏振方位具有很好的一致性。低频和中高频均比较丰富的地震动容易同时激发山体的低阶和高阶振型;中高频含量比较丰富的地震动容易激发山体的高阶振型。
3) 坡脚输入地震动的傅里叶谱表明,各输入地震动频率含量丰富的频段有所不同。分解合成后的地震动傅里叶谱谱比显示,山体的偏振效应主要发生在山体横向及走向方位上,低阶振型易引起山体横向振动,高阶振型易引起山体走向振动。
4) 地震动作用下的山体,其位移幅值最大方位会出现在山体横向及走向上,与输入山体地震动的频谱特性有密切关系。在对跨山体桥梁、隧道、水电站等长大结构进行抗震设计时,应重点考虑山体地形的偏振效应。
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图 1 研究区构造简图和1970年7月19日至2018年6月10日的地震分布(a)以及垂向剖面AA' 简图(b)
F1:巴彦乌拉山山前断裂;F2:狼山山前断裂;F3:桌子山西缘断裂;F4:正谊关断裂
Figure 1. The tectonic settings and distribution of earthquakes from 19 July 1970 to 10 June 2018 in the studied area (a) and the vertical profile AA' (b)
F1:Bayanwula mountain Piedmont fault;F2:Langshan mountain Piedmont fault;F3:Zhuozi mountain Western margin fault of;F4:Zhengyiguan fault
图 14 中国不同地区土壤气浓度和释放通量对比图
数据引自Li等(2013),Zhou等(2016)和杨江(2018)
Figure 14. Contrast map of concentrations and fluxes of soil gases from different places in China
Data is after Li et al (2013),Zhou et al (2016) and Yang (2018)
表 1 土壤气Rn,Hg和CO2测量剖面基本信息
Table 1 Basic information about the measurement sections for soil gases Rn,Hg and CO2
剖面 剖面编号 断裂 断裂编号 断裂性质 北纬/° 东经/° 巴彦乌拉 BYWL 巴彦乌拉山山前断裂 F1 正断层 39.5 105.2 乌兰巴兴 WLBX 狼山山前断裂 F2 正断层 40.4 106.2 那仁乌布尔嘎查 NRWBEGC 狼山山前断裂 F2 正断层 40.9 106.6 大路盖 DLG 桌子山西缘断裂 F3 逆断层 40.0 106.8 正义关 ZYG 正谊关断裂 F4 左旋走滑 39.3 106.7 注:土壤气剖面的经纬度是测线中央(剖面与断层相交处)的经纬度。 表 2 土壤气Rn,Hg和CO2浓度的测量结果
Table 2 Measurement results of the concentrations of soil gases Rn,Hg and CO2
测线编号 测项 Qmean σ Qmean+σ/2 Qmean-σ/2 Qmax Qmin KQ BYWL-1 CO2 0.08% 0.03 0.09% 0.07% 0.14% 0.06% 2.33 BYWL-2 0.11% 0.04 0.13% 0.09% 0.18% 0.04% 4.50 DLG-1 0.10% 0.02 0.11% 0.08% 0.14% 0.06% 2.33 DLG-2 0.10% 0.04 0.12% 0.08% 0.23% 0.07% 3.29 NRWBEGC-1 0.22% 0.06 0.25% 0.19% 0.38% 0.14% 2.71 WLBX-1 0.14% 0.05 0.16% 0.11% 0.28% 0.11% 2.55 WLBX-2 0.12% 0.03 0.13% 0.10% 0.16% 0.07% 2.29 ZYG-1 0.23% 0.06 0.26% 0.20% 0.32% 0.16% 2.00 ZYG-2 0.22% 0.06 0.25% 0.19% 0.36% 0.15% 2.48 BYWL-1 Hg 13 6 16 10 30 6 5.00 BYWL-2 10 3 11 8 15 6 2.50 DLG-1 12 4 14 10 24 8 3.00 DLG-2 12 3 13 11 19 8 2.38 NRWBEGC-1 10 4 12 8 18 4 4.50 WLBX-1 10 3 11 8 16 8 2.13 WLBX-2 10 3 11 9 15 7 2.14 ZYG-1 9 2 10 8 12 7 1.85 ZYG-2 11 3 12 9 15 7 2.14 BYWL-1 Rn 9.784 6.768 13.168 6.400 27.827 4.403 6.32 BYWL-2 16.966 18.015 25.973 7.958 60.091 3.974 15.12 DLG-1 2.486 1.099 3.036 1.937 4.975 0.739 6.73 DLG-2 2.417 0.947 2.891 1.944 4.381 1.008 4.35 NRWBEGC-1 9.394 2.899 10.843 7.944 13.376 5.818 2.30 WLBX-1 2.215 0.417 2.423 2.007 2.842 1.643 1.73 WLBX-2 2.018 0.674 2.355 1.681 3.764 0.739 5.09 ZYG-1 7.058 2.409 8.263 5.854 10.420 3.833 2.72 ZYG-2 7.289 1.970 8.274 6.304 10.822 4.706 2.30 注:Rn和Hg的浓度Q的单位分别为kBq·m−3和ng·m−3;Qmean,σ,Qmean+σ/2,Qmean-σ/2,Qmax和Qmin分别为每条测线上浓度的平均值、标准偏差、异常上限、异常下限、最大值和最小值;KQ为断层活动性指数。 表 3 土壤气剖面的平均浓度Q和释放通量F
Table 3 The average values of concentration Q and flux F at each soil gas section
剖面 FCO2/(g·m−2·d−1) FRn/(mBq·m−2·s−1) FHg/(ng·m−2·h−1) QCO2 QRn/(kBq·m−3) QHg/(ng·m−3) BYWL 11.76 39.07 7.46 0.09% 13.375 11 ZYG 15.17 12.71 0 0.23% 7.174 10 DLG 10.52 22.82 0 0.10% 2.452 12 NRWBEGC 9.38 17.25 3.69 0.22% 9.394 10 WLBX 6.54 5.17 0.62 0.13% 2.117 10 平均值 10.67 19.40 2.35 0.15% 6.902 11 表 4 土样化学组分分析测试结果
Table 4 The test results of chemical composition analysis of soil samples
剖面 CU/(Bq·kg−1) CTh/(Bq·kg−1) CRa/(Bq·kg−1) CK/(Bq·kg−1) TC含量 CHg/(ng·g−1) BYWL 39.8 46.2 28.7 616 0.972% 1.54 DLG 24.2 36.8 23.7 546 0.762% 13.30 NRWBEGC 40.2 52.7 30.6 944 0.163% 5.67 WLBX 17.6 17.6 13.0 553 0.577% 5.85 ZYG 8.1 44.5 27.2 559 2.420% 28.90 注:所采土样于2017年8月由核工业地质研究所进行检测;C为质量活度。 -
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