长江河口九段沙上沙湿地芦苇与土壤之间营养元素的灰色关联分析

为探明生长季不同时期芦苇湿地生态系统植物与土壤之间营养元素的关系,利用灰色关联分析方法,对长江河口九段沙上沙芦苇湿地的芦苇营养元素吸收量与土壤营养元素含量之间的关联度进行了研究。结果表明：芦苇主要从0～15 cm土壤吸取N元素,从15～40 cm土壤获取P、K元素,而从40～60 cm土壤吸收N、P、K元素量都较少。芦苇-土壤之间营养元素关联度排序为：4月为N＞K＞P;5月为P＞K＞N,6～8月为K＞P＞N;9～11月为N＞K＞P;12月为P＞N＞K。同一营养元素不同时期芦苇-土壤之间关联度也存在差异,芦苇与土壤营养元素N、P、K元素关联最密切时期分别出现在9、12与6月,均与上层土壤营养元素关联最密切。9、12与6月分别为芦苇-土壤之间N、P、K元素迁移、转化与循环的活跃时期,上层土壤是其活动相对重要的场所。芦苇生长过程中吸收土壤营养元素均存在时空差异,不同时期芦苇对不同深度土壤的营养元素吸收强度也不尽相同。芦苇地下部分不同部位与土壤中营养元素种类的关联度排序相同,而芦苇地上部分的排序则不同。     

川中丘陵区镶嵌式田坎土壤可蚀性变化特征及影响因素

田坎土壤可蚀性是影响梯田稳定的关键因素,为探讨不同修建年限田坎土壤可蚀性,以遂宁市安居区镶嵌式田坎为研究对象,结合野外采样和室内分析,研究了镶嵌式田坎修建1、3和5年的土壤可蚀性(K值)变化及影响因素。结果表明：(1)K值范围0.05～0.06 (t·hm²·h)/(MJ·mm·hm²),田的K值大于坎,随着镶嵌式田坎的修建年限的增加,坎K值呈减小趋势,建成5年时达显著性水平。(2)坎黏粒含量随修建年限递减,而粉粒与砂粒含量呈递增趋势;建成1年的坎土壤容重显著大于建成3年和5年;建成1年和3年时,田和坎的土壤团聚体破坏率(PAD)、不稳定团粒指数(E_LT)、风干土团聚体分形维数(风干D)、水稳性团聚体分形维数(水稳D)、风干性团聚体平均质量直径(风干MWD)和风干性团聚体几何平均直径(风干GMD)有显著差异;建成5年时则无显著差异,说明建成5年时田和坎的土壤物理性质趋于一致。(3)镶嵌式田坎上的土壤有机质含量随修建年限呈增加趋势,建成5年时达显著性水平。(4)K值与PAD、E_LT和水稳D呈极显著正相...     

江汉平原稻田冠层CO2通量变化特征及其影响因素分析

二氧化碳(CO2)、甲烷(CH4)、氧化亚氮(N2O)被认为是最重要的温室气体,在气候变化中扮演着重要角色,实地测定稻田生态系统CO2通量是农业源温室气体监测与控制技术研究的基本内容。采用涡度相关法对江汉平原稻田生态系统进行了通量观测,并对水稻不同生长阶段冠层CO2通量、潜热、显热通量变化特征及其影响因素进行了分析。结果表明:水稻各生育期冠层CO2、潜热、显热通量日变化均表现出明显的单峰特征,但幅度不同,这与太阳总辐射的日变化及下垫面作物叶面积指数大小关系密切。稻田系统作物呼吸与土壤呼吸排放CO2,排放通量一方面与温度的变化有关,另一方面也受灌溉、作物生长状况的影响;稻田光合作用吸收同化大气CO2,吸收通量与作物群体叶面积指数大小、光合有效辐射强度有关。不同生长期冠层CO2通量与温度因子(气温、5cm土层温度)、光辐射强度因子(时光合有效辐射曝辐量)的相关性均达到极显著水平(P<0.01),其中,分蘖-灌浆乳熟期CO2净通量对时光合有效辐射曝辐量响应的灵敏度较大,可以通过直角双曲线模型来拟合评估CO2净通量。     

持久性有机污染物土气交换过程影响因素分析

持久性有机污染物(POPs)在全球范围内进行远距离传输过程中,土壤既是污染物的主要汇,又是空气中污染物的潜在来源.土气交换过程是POPs环境归宿的重要环节,该交换过程受POPs理化性质、近地面气象条件、土壤理化性质及植被覆盖等因素的影响.对近期报道的POPs土气交换过程影响因素研究进行了综述与展望,列出了研究中涉及的重要模型及公式.环境温度的变化既能改变目标物在气固相之间的分配行为,影响空气中污染物的干湿沉降和气态交换过程,也能够通过近地面温度场的梯度变化影响污染物在土气交换过程中的垂直紊流扩散.此外,近地面水平风速的变化也会影响目标物的在近地面空气中的垂直紊流扩散.土壤有机质含量及种类控制了土壤中POPs的吸附/解吸过程,土壤温度和湿度影响污染物的土气分配系数,土壤矿物组成也会影响污染物吸附和解吸过程.地面植被能够吸收和吸附空气中气态和颗粒态POPs,通过雨水淋刷和枯落物凋落转移到土壤中;植被覆盖可以减少土壤的温度变化,减少土壤中POPs的挥发.尽管近年已经取得丰硕的成果,但在土气交换过程多因素耦合影响量化评估、动态评估POPs在典型场地原位复杂环境下的土气交换通量、在区域尺度量化植被对城市中POPs土气交换的影响等方面有待开展深入研究工作.     

南水北调中线工程水源地的土壤可蚀性特征

选定南水北调中线工程水源地丹江口水库区这一国家水土流失重点治理区域为研究地点,对该地的土壤可蚀性特征进行了研究。在研究区不同土地覆盖类型里采取表层(20 cm)土壤样品,室内分析样品土壤的质地和有机质含量,利用EPIC模型及实验室分析的土壤质地和有机质数据计算样品土壤可蚀性K值。在ARCGIS里,利用Ordinary Kriging插值方法生成研究区K值分布图。然后按一定标准将K值进行分级,得出不同K等级值的空间分布及面积。结果表明：研究区K的均值为0034 8（ t·hm2·h）/（hm2·MJ·mm）,主要为中可蚀性土壤(面积占91.71%)。东部(主要是耕地)土壤K值高于西部(主要是林地),是侵蚀治理的重点地区。研究结果可为库区水土流失定量遥感监测提供基础资料,对库区的土壤侵蚀治理有一定的参考作用     

城市土壤重金属含量及其对儿童健康风险的初步评价——以四川省宜宾市为例

通过对宜宾市主要街道47个土壤样中Pb、As、Zn和Cu含量的调查研究,并利用健康风险评价模型,初步评价了城市土壤中重金属对儿童(6~12岁)的健康风险。Pb、Zn和Cu采用火焰 原子吸收光谱仪测定,As采用氢化物发生 原子荧光光谱测定。结果表明,宜宾市城市土壤中Pb、Zn和Cu含量显著高于四川省土壤背景值,表现出明显的累积效应(〖WTBX〗p〖WTBZ〗=0000),As含量显著低于四川省土壤背景值(〖WTBX〗p〖WTBZ〗=002);与四川省土壤基线值相比,土壤中Pb、Zn和Cu含量的超标率分别为362%、297%和511%,As含量尚未超标。城市土壤中Pb、As、Zn和Cu的单危害指数大小(〖WTBX〗HI)依次为HIAs>HIPb>HICu>HIZn,总危害指数THI〖WTBZ〗为346×10-1。单危害指数和总危害指数均低于可接受水平1,未对儿童表现出非致癌危害。土壤中As的总致癌风险〖WTBX〗TCR〖WTBZ〗为872×10-6,在可接受水平内(1×10-6~1×10-4),未对儿童表现出致癌风险。     

庐山不同森林植被类型土壤特性及其健康评价

土壤作为森林生态系统的一个重要因子,评价森林土壤健康状况对森林健康的维护经营以及森林系统功能的发挥具有重要意义。在系统调查和分析庐山8种森林植被类型土壤特性的基础上,评价指标分别从物种多样性以及不同的森林土壤特性中进行筛选,包括物种多样性系数、枯落物层厚度、腐殖质层厚度、土层厚度、容重、粘粒含量、有机质、p H值、阳离子交换量、全氮、水解氮、有效磷、速效钾、磷酸酶活性等指标,基于SPSS19.0软件对所获得数据进行差异性检验和相关分析,确定各项指标的权重,应用合适的土壤健康评分函数,将测得的指标值转换为对应指标的分值,最后通过加权综合法,计算其土壤健康指数,并对不同森林植被类型土壤健康状况进行评价。结果表明,8种森林植被类型下最终的土壤健康指数大小排序为:针阔混交林(0.78)常-落混交林(0.72)灌丛(0.69)常绿阔叶林(0.67)落叶阔叶林(0.64)竹林(0.59)马尾松林(0.53)黄山松林(0.46)。     

缙云山针阔混交林碳通量变化特征及影响因子研究

基于涡度相关技术,以2016年6月～2017年5月的通量数据为依据,分析了缙云山针阔混交林生态系统碳通量变化特征及其对环境因子的响应。结果表明:各月CO_2通量平均日变化呈"U"字形,最小值出现在7月,为-0.95 mg·m~(-2)·s~(-1),最大值在12月,为0.43 mg·m~(-2)·s~(-1),CO_2通量正负值转换时刻具有明显的季节变化规律,夏季日碳汇时间最长,冬季日碳汇时间最短;净生态系统碳交换量累积量除12月为正值(20.38 gC·m~(-2)·mon~(-1)),表现为碳源外,其他月份均为负值,表现为碳汇,碳积累量最多的是7月(-129.53 gC·m~(-2)·mon~(-1)),净生态系统碳交换、生态系统呼吸、总生态系统碳交换年总量分别为-566.49、1 196.68、-1 761.63 gC·m~(-2)·a~(-1);光合有效辐射是影响日间净碳交换量的主导因子,二者关系符合Michaelis-Menten模型,日间净碳交换量随光合有效辐射增大而降低,光合有效辐射PAR能解释14.1%～58.2%的日间净碳交换量变化,饱和水汽压差是日间净碳交换量限制因子,最适范围是0.5～1.0 kPa,过高和过低均会使日间净碳交换量对光合有效辐射的响应减弱;影响夜间净碳交换量的主导因子是5 cm土温,二者关系符合Van’t Hoff模型,夜间净碳交换量随5 cm土温增大而增加,土壤体积含水率是夜间净碳交换量的限制因子,饱和水汽压差大于或小于0.28 m~(-3)·m~(-3)均会对夜间净碳交换量产生抑制作用,但作用较小。缙云山针阔混交林净生态系统碳交换能力与相近纬度其他森林生态系统基本持平,总生态系统碳交换能力和生态系统呼吸强度则较大。     

南京某地农业土壤中有机污染分布状况研究

对某大型矿业企业周边农业土壤中两类POPs物质——15种多环芳烃和有机氯农药（DDTs和HCHs）的残留量进行了调查。结果表明,PAHs检出率为100%,总残留量范围为312.2~27 580.9 μg·kg-1,且以四环以上多环芳烃组分为主。不同样区土壤PAHs残留量受常年风向影响明显。农业土壤中有机氯农药六六六和滴滴涕均有检出,但残留水平不高,分别为3.60 μg·kg-1(0.81~9.43 μg·kg-1)和11.13 μg·kg-1(3.31~43.81 μg·kg-1)。土壤有机氯农药的残留以p,p′ DDE和p,p′ DDT为主。土壤中HCHs的各异构体组分含量特征为α>β>γ>δ。部分采样点土壤仍可能有新的有机氯污染物来源。     

太湖辐射和能量收支的时间变化特征

湖泊的辐射和能量收支的观测研究对于气象学和水文学研究都具有重要的意义。于2012年采用涡度相关系统和小气候观测系统观测太湖表面的辐射平衡、湖泊与大气之间的感热和潜热通量、水温廓线和常规气象要素数据,分析太湖表面辐射及能量收支的时间变化特征以及环境控制因子。结果表明:(1)太湖2012年辐射收支四分量(向下短波辐射、向上短波辐射、向下长波辐射和向上长波辐射)的年均值分别为146.5、9.4、359.7和405.4 W/m~2,反照率的年均值为0.06,各辐射分量日变化和季节变化特征明显;(2)净辐射和热储量日变化趋势相同,正午最高,午夜最低;湍流能量通量的日变化幅度较小;不同天气条件下能量分配具有一定差别:晴天条件下能量分配以潜热通量为主,阴天净辐射能量主要被水体吸收转换为热储量;(3)通过分析湍流能量通量与环境因子的相关性发现:感热通量变化最主要的相关因子是风速与湖–气界面温度差的乘积;风速与湖-气界面水汽压的乘积是潜热通量的主要驱动因子。本研究结果能为边界层气象学、全球能量和物质循环以及湖泊生态环境治理等研究提供理论基础和数据支持。     

Radiological maps for Trabzon, Turkey

The activity concentrations and absorbed gamma dose rates due to primordial radionuclides and ¹³⁷Cs have been ascertained in 222 soil samples in 18 counties of the Trabzon province of Turkey using a HPGe detector. The mean activity concentrations of ²³⁸U, ²³²Th, ⁴⁰K and ¹³⁷Cs in soil samples were 41, 35, 437 and 21 Bq kg⁻¹, respectively. Based on the measured concentrations of these radionuclides, the mean absorbed gamma dose in air was calculated as 59 nGy h⁻¹ and hence, the mean annual effective dose due to terrestrial gamma radiation was calculated as 72 μSv y⁻¹. In addition, outdoor in situ gamma dose rate (D) measurements were performed in the same 222 locations using a portable NaI detector and the annual effective dose was calculated to be 66 μSv y⁻¹ from these results. The results presented in this study are compared with other parts of Turkey. Radiological maps of the Trabzon province were composed using the results obtained from the study.     

Concentrations of natural radionuclides in imported mineral substances

Levels of natural radionuclides, such as thorium-232 (232Th), radium-226 (226Ra) and potassium-40 (40K), were determined in about 2,000 samples of imported mineral substances using gamma spectrometry. The maximum concentration levels of 232Th, 226Ra and 40K were 1,260 +/- 54, 13,400 +/- 94 and 1,256 +/- 260 Bq kg(-1), respectively, in zirconium compounds. Due to relatively high concentrations of the above-mentioned radionuclides in some imported mineral substances, the National Radiation Protection Department (NRPD), as the competent authority, has established national limits (900 Bq kg(-1) for 232Th, 1800 Bq kg(-1) for 226Ra and 11,000 Bq kg(-1) for 40K), based on the external exposures, for general importation permits of these materials.     

Natural radioactivity levels in topsoil from the Pearl River Delta Zone, Guangdong, China

Concentrations of the natural radionuclides ²³⁸U, ²²⁶Ra, ²³²Th and ⁴⁰K have been measured by γ-ray spectrometry in 796 topsoil samples from the Pearl River Delta Zone (PRDZ) of Guangdong, China. The mean concentrations for ²³⁸U, ²²⁶Ra, ²³²Th and ⁴⁰K were found to be 140 ± 37 Bq kg⁻¹, 134 ± 41 Bq kg⁻¹, 187 ± 80 Bq kg⁻¹ and 680 ± 203 Bq kg⁻¹ dry mass, respectively. These values were all higher than the mean values in soil for China and the world. Outdoor air-absorbed dose rates, calculated from activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K, ranged from 86 to 237 nGy h⁻¹, with a mean value of 165 ± 46 nGy h⁻¹. The corresponding annual outdoor effective dose rate per person was estimated to be between 0.11 and 0.29 mSv y⁻¹, with a mean value of 0.20 ± 0.06 mSv y⁻¹, which was also higher than the world mean value of 0.07 mSv y⁻¹. The radium equivalent activity (Ra_eq) and the external hazard index (I_r) resulted from the natural radionuclides in soil, were also calculated and found to vary from 230 to 676 Bq kg⁻¹ and from 0.6 to 1.8, respectively. The Ra_eq and the I_r in all the investigated regions were up to 75% higher than the set limits of 370 Bq kg⁻¹ and 1.0, respectively.     

Occupational exposure to radon and natural gamma radiation in the La Carolina, a former gold mine in San Luis Province, Argentina

Radon and gamma radiation level measurements were carried out inside the La Carolina mine, one of the oldest gold mining camps of southern South America, which is open for touristic visits nowadays. CR-39 track-etch detectors and thermoluminescent dosimeters of natural CaF₂ and LiF TLD-100 were exposed at 14 points along the mine tunnels in order to estimate the mean ²²²Rn concentration and the ambient dose equivalent during the summer season (November 2008 to February 2009). The values for the ²²²Rn concentration at each monitoring site ranged from 1.8 ± 0.1 kBq m⁻³ to 6.0 ± 0.5 kBq m⁻³, with a mean value of 4.8 kBq m⁻³, indicating that these measurements exceed in about three times the upper action level recommended by ICRP for workplaces. The correlations between radon and gamma radiation levels inside the mine were also investigated. Effective doses due to ²²²Rn and gamma rays inside the mine were determined, resulting in negligible values to tourists. Considering the effective dose to the mine tourist guides, values exceeding 20 mSv of internal contribution to the effective doses can be reached, depending on the number of working hours inside the mine.     

Concentration ratios for small mammals collected from the exposed sediments of a 137Cs contaminated reservoir

(137)Cs concentration ratios were computed for small mammals collected from the dried sediments of a partially drained, contaminated reservoir. Soil (137)Cs activity concentrations were heterogeneous on small and large spatial scales and had a geometric mean of 253 (range 23-2110) Bq/kg dry weight. Mean (137)Cs activity concentrations in composite cotton rat Sigmodon hispidus and cotton mouse Peromyscus gossypinus samples averaged 2480 (range 556-6670) and 471 (range 96-1000) Bq/kg whole body dry weight, respectively. About 50% of the variance in cotton rat tissue (137)Cs activity was explained by variation in soil (137)Cs activity. Soil-to-animal dry weight concentration ratios averaged 6.0 for cotton rats and 1.2 for cotton mice and were generally similar to (137)Cs concentration ratios for herbivorous, homeothermic animals from other contaminated ecosystems. In the RESRAD-BIOTA dose model, the default wet-weight concentration ratio for (137)Cs in terrestrial animals is 110 resulting in an estimate of internal and external radiation doses to terrestrial biota that is 44 times more than the dose calculated with the actual measured wet-weight concentration ratio for cotton rats (1.6). These results show that site-specific concentration ratios can significantly affect the estimation of dose.     

Derivation of hazardous doses for amphibians acutely exposed to ionising radiation

Derivation of effect benchmark values for each taxonomic group, which has been difficult due to lack of experimental effects data, is required for more adequate protection of the environment from ionising radiation. Estimation of effects doses from nuclear DNA mass and subsequent species sensitivity distribution (SSD) analysis were proposed as a method for such a derivation in acute irradiation situations for assumed nuclear accident scenarios. As a case study, 5% hazardous doses (HD₅s), at which only 5% of species are acutely affected at 50% or higher lethality, were estimated on a global scale. After nuclear DNA mass data were obtained from a database, 50% lethal doses (LD₅₀s) for 4.8 and 36% of the global Anura and Caudata species, respectively, were estimated by correlative equations between nuclear DNA mass and LD₅₀s. Differences between estimated and experimental LD₅₀s were within a factor of three. The HD₅s obtained by the SSD analysis of these estimated LD₅₀s data were 5.0 and 3.1 Gy for Anura and Caudata, respectively. This approach was also applied to the derivation of regional HD₅s. The respective HD₅s were 6.5 and 3.2 Gy for Anura and Caudata inhabiting Japan. This HD₅ value for the Japanese Anura was significantly higher than the global value, while Caudata had no significant difference in global and Japanese HD₅s. These results suggest that this approach is also useful for derivation of regional benchmark values, some of which are likely different from the global values.     

Indoor radon distribution of subway stations in a Korean major city

The overall survey on indoor radon concentration was conducted at all subway stations in a major city, Daejeon in the central part of Korea. It was quarterly performed from September 2007 to August 2008. The annual arithmetic mean of indoor radon concentration of all the stations was 34.1 ± 14.7 Bq m⁻³, and the range of values was from 9.4 to 98.2 Bq m⁻³. The radon concentrations in groundwater (average 31.0 ± 0.8 Bq m⁻³) were not significantly high in most stations, but the concentration (177.9 ± 2.3 Bq L⁻¹) of one station was over the level of 148 Bq L⁻¹ in drinking water proposed by U.S. EPA. Based on indoor survey results, the approximate average of the annual effective dose by radon inhalation to the employees and passengers were 0.24 mSv y⁻¹, and 0.02 mSv y⁻¹, respectively. Although the effective dose based on the UNSCEAR report was potentially estimated, for more accurate assessment, the additional survey on the influence by indoor radon will be necessary.     

Evaluation and assessment of 25 years of environmental radioactivity monitoring data at Tarapur (India) nuclear site

The evaluation and assessment of monitoring data generated over a period of 1983-2007 (25 years) of a nuclear facility is presented. Time trends of particulate radioactivity, correlation between ¹³⁷Cs in discharge canal seawater and station discharged activity and correlation of ¹³⁷Cs, ⁶⁰Co, and ¹³¹I in marine species such as sponge and Nerita (gastropod) and corresponding discharged activity are discussed. The concentration of ¹³⁷Cs and ¹³¹I in seawater versus biota are discussed. A good correlation between ¹³⁷Cs in seawater and ¹³⁷Cs in liquid waste discharged was observed (R² = 0.8, p < 0.001). Similarly, correlation was good for Nerita and discharged concentration of ¹³⁷Cs, ¹³¹I and ⁶⁰Co (R² = 0.55-0.73 and p < 0.001). The measurements over the years indicated that there is no accumulation of radionuclides in either the terrestrial or aquatic environments. The mean ¹³⁷Cs decreased from the pre-operational levels: 7.0-3.6 Bq kg⁻¹ in soil, 0.91-0.016 Bq L⁻¹ in milk and 0.28-0.036 Bq kg⁻¹ in vegetation. Similarly, the mean ⁹⁰Sr in these matrixes decreased from 3.9 to 0.26 Bq kg⁻¹; 0.37-0.011 Bq L⁻¹ and 0.34-0.022 Bq kg⁻¹ respectively. Cesium-137 of about 700 μBq m⁻³ was measured in the air filter disks during 1986 and there was a decrease of three orders of magnitude in concentration over the 25 years. The evaluation of environmental data indicated that the radionuclide concentrations and potential impacts, in terms of effective dose to the members of public, have significantly reduced since 1969.     

Radiological risk assessment and biosphere modelling for radioactive waste disposal in Switzerland

Long-term safety assessments for geological disposal of radioactive waste in Switzerland involve the demonstration that the annual radiation dose to humans due to the potential release of radionuclides from the waste repository into the biosphere will not exceed the regulatory limit of 0.1 mSv. Here, we describe the simple but robust approach used by Nagra (Swiss National Cooperative for the Disposal of Radioactive Waste) to quantify the dose to humans as a result to time-dependent release of radionuclides from the geosphere into the biosphere. The model calculates the concentrations of radionuclides in different terrestrial and aquatic compartments of the surface environment. The fluxes of water and solids within the environment are the drivers for the exchange of radionuclides between these compartments. The calculated radionuclide concentrations in the biosphere are then used to estimate the radiation doses to humans due to various exposure paths (e.g. ingestion of radionuclides via drinking water and food, inhalation of radionuclides, external irradiation from radionuclides in soils). In this paper we also discuss recent new achievements and planned future work.     

An approach to comparative assessments of potential health risks from exposure to radionuclides and hazardous chemicals

The need to compare potential health risks to the public associated with different activities that can result in releases of hazardous substances to the environment is becoming increasingly important in decision-making. In making such comparisons, it is desirable to use equivalent indicators of potential health risks for radionuclides, chemical carcinogens, and noncarcinogenic hazardous chemicals. Current approaches to risk assessment that were developed for purposes of protecting human health do not provide equivalent indicators of potential risks from exposure to radionuclides and hazardous chemicals. Comparisons of environmental concentrations or calculated exposures or risks with standards for protection of public health also do not provide equivalent indicators of potential risks. We propose a simple approach to comparative risk assessments in which calculated exposures to any hazardous substances are expressed relative to no-observed-effect levels (NOELs) or, preferably, lower confidence limits of benchmark doses (BMDLs) in humans. This approach provides an equivalent, science-based indicator of the relative risks posed by different exposures to any hazardous substances.