首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
INTRODUCTIONFresh water lakes are one of the planet’s mosti mportant freshwater resources.They support life invarious forms,develop tourism and provide uniquerecreational opportunities.It is also a good source ofthe provision of drinking-water for local communi-ties.Studies on trace elements in rivers,lakes,andsedi ments(Zhou et al.,2004;Gray et al.,2000;Grosheva et al.,2000;Klavins et al.,2000;Aucoinet al.,1999;Bortoli et al.,1998;Elbaz-Poulichet etal.,1996;Johansson et al.,1995;F r…  相似文献   

2.
The heavy metal contents of Mn, Ni, Cu, Zn, Cr, Co, Pb, Cd, Fe, and V in the surface sediments from five selected sites of El Temsah Lake was determined by graphite furnace atomic absorption spectrophotometer. Geochemical forms of elements were investigated using four-step sequential chemical extraction procedure in order to identify and evaluate the mobility and the availability of trace metals on lake sediments, in comparison with the total element content. The operationally defined host fractions were: (1) exchangeable/bound to carbonate, (2) bound to Fe/Mn oxide, (3) bound to organic matter/sulfides, and (4) acid-soluble residue. The speciation data reveals that metals Zn, Cd, Pb, Ni, Mn, Cu, Cr, Fe, and V are sink primarily in organic and Fe–Mn oxyhydroxides phases. Co is mainly concentrated in the active phase. This is alarming because the element is enriched in Al Sayadin Lagoon which is still the main site of open fishing in Ismailia. Average concentration of the elements is mostly above the geochemical background and pristine values of the present study. There is a difference on the elemental composition of the sediment collected at the western lagoon (Al Sayadin Lagoon), junction, the shoreline shipyard workshops, and eastern beach of the lake. Depending upon the nature of elements and local pollution source, high concentration of Zn, Pb, and Cu are emitted by industrial wastewater flow (shoreline workshops), while sanitary and agricultural wastewater (El Bahtini and El Mahsama Drains) emit Co and Cd in Al Sayadin Lagoon. On the other hand, there is a marked decrease in potentially toxic heavy metal concentrations in the sediments at the most eastern side of the lake, probably due to the successive sediment dredging and improvements in water purification systems for navigation objective. These result show that El Temsah receives concentrations in anthropogenic metals that risk provoking more or less important disruptions, which are harmful and irreversible on the fauna and flora of this lake and on the whole ecobiological equilibrium.  相似文献   

3.
The BCR sequential extraction procedure is applied to probe into the speciation distribution of heavy metals (Cd, Cr, Zn, Cu and Pb) in lake sediments of Core XJ2 in Xijiu Lake, Taihu Lake catchment, China. The results showed that the effective species concentration of this five heavy metal elements increased obviously during the past century, the proportions of organic/sulphide fractions of Zn, Cu and Pb decreased while the Fe–Mn oxide fractions increased, and the proportion of Fe–Mn oxide fractions of Cd decreased while the exchangeable and carbonate fractions increased. The concentrations of exchangeable and carbonate fractions of these five elements were increased in the past century, especially the proportions of these fractions of Cd, Zn, Cu and Pb increased prominently. These changes could be attributed to the anthropogenic pollution. Since the changes of the heavy metal concentrations were corresponding to the history of human activities, especially the industry development, within the catchment.  相似文献   

4.
福建龙海土壤重金属含量特征及影响因素研究   总被引:1,自引:0,他引:1  
为有效预防土壤重金属生态风险,以福建龙海市表层土壤为研究对象,应用经典统计分析、随机森林等方法,研究重金属元素含量特征及其影响因素。结果表明:(1)第四纪冲洪(海)积成因水稻土中多数重金属元素含量较高;(2)燕山期中酸性岩风化形成的残坡积红壤中重金属元素活动态含量较高;(3)As、Cu、Ni形态含量与全量相关性较好,而Cd、Cr、Hg的多数形态含量与全量相关性较差;(4)除元素全量外,土壤有机质对弱有机结合态重金属(不包括Ni、Pb元素)以及离子交换态、碳酸盐结合态Cd、Zn有重要影响,阳离子交换量对各形态Ni,(Fe×Al)/Si对各形态Cu具有重要影响,而土壤成因、土壤类型对重金属形态组成的影响较小。研究表明土壤重金属形态组成及其富集区与其全量不尽一致,土壤重金属生态风险评价应考虑土壤重金属形态分布特征。  相似文献   

5.
太湖沉积物中重金属的地球化学形态及特征分析   总被引:24,自引:2,他引:22  
用连续提取法分析了太湖沉积物5种重金属的地球化学形态,对地球化学形态的组成和地理特征进行了分析研究.重金属地球化学形态配分的共同特点是可交换态最低,残渣态最高.两种形态中Cd的可交换态最高,Cr的残渣态最高,可交换态最低.Cd的碳酸盐态较高,Cr的最低;Pb、Cd的Fe-Mn氧化态较高,Cu的偏低;Cu的有机态最高,Cd的最低;Zn的地球化学形态比例大都处于中间.地域上变化较大的元素是Cd和Cu,变化不明显的元素有Pb和Zn.化学成分中Fe2O3、MnO与重金属地球化学形态的相关性最好,TOC与Cu的形态相关系数最高.综合对比分析表明,太湖沉积物重金属的生物有效性以Cd为最高,其次为Pb.  相似文献   

6.
太湖MS岩芯重金属元素地球化学形态研究   总被引:21,自引:4,他引:17  
采用BCR三步提取法对太湖MS岩芯沉积物中Cu、Fe、Mn、Ni、Pb和Zn等6种重金属元素的化学形态进行了研究.结果表明,有效结合态的Cu、Ni和Pb主要以有机物及硫化物结合态、Fe-Mn氧化物结合态存在,Fe和Zn主要以Fe-Mn氧化物结合态存在,Mn主要以可交换态及碳酸盐结合态存在;Fe-Mn氧化物结合态的Ni、Pb和Zn与可还原态的Mn有较好的正相关关系,有机物及硫化物结合态的Cu、Mn、Ni、Pb和Zn与有机碳含量有较好的正相关关系;重金属形态分布体现了重金属元素地球化学性质的差异,以及重金属形态含量与沉积物理化性质的关系.沉积岩芯重金属元素形态垂向变化规律及次生相富集系数表明,Cu、Mn、Ni、Pb和Zn在沉积岩芯13~4 cm有效结合态含量较稳定,为自然沉积;4~0 cm有效结合态含量明显升高,存在一定程度的人为污染.根据137Cs测年结果判断,沉积岩芯Cu、Mn、Ni、Pb和Zn等重金属污染开始于20世纪70年代末期,主要污染元素及污染历史与太湖流域污染工业类型及经济发展阶段相吻合.  相似文献   

7.
The species of Cu, Pb, Zn, Cd and Cr in sediments of the Taihu Lake, China, have been analyzed using the sequential chemical extraction method. Variations in the chemical fractions of these metals and their geographic distributions have also been studied. For all five metals, the residual fraction is highest but the exchangeable fraction is lowest among all the fractions. Compared to other metals, Cd has the highest percentage in the exchangeable fraction, and Cr is associated mainly with the residual fraction. Cu in the organic fraction and Pb in the Fe-Mn fraction are the important species, whereas the lowest percentages are found for Cd in the organic fraction, Cu in the Fe-Mn oxide fraction and Pb in the carbonate fraction. With respect to spatial differences, the total contents in the non-residual fractions of the metals in bay sediments are found to be higher than those in other sediments. The fractions of Cd, Cu and Cr showed significant variations in different regions. The fractions of Pb and Zn, however, did not show significant variations in spatial distribution, suggesting different amounts and different paths of anthropogenic input for the metals. Comparisons of the metal speciation indicated that Cd might be the most bioavailable metal, followed by Pb.  相似文献   

8.
 Bottom-water data and trace metal concentration of Cu, Cr, Ni, Pb, Co, Zn, and organic matter in surficial sediment samples from 13 sampling stations of Lake Chapala in Mexico were studied. The lake is turbid with a great amount of flocculated sediments as a result of wind mixing, sediment re-suspension, and Lerma River discharges. Al distribution pattern in sediments was used as an indicator of the Lerma River discharges into Lake Chapala. The highest values of Cu (33.27 ppm), Cr (81.94 ppm), Pb (99.8 ppm), and Zn (149.7 ppm) were detected in sediments near the lake outlet. The bioavailable metal fraction is low for all metals except Pb, which shows 65–93% of the total metal concentration in bioavailable form. The minimum energy zone in the lake was related to organic matter concentration and was located in the SE part of the lake. An analysis of the studied parameters shows two zones: eastern zone (fluvio-deltaic) and central-western zone (lacustrine). Received: 9 September 1998 · Accepted: 16 November 1998  相似文献   

9.
金鹏  祁超  郭炳跃 《江苏地质》2023,47(4):420-427
为查清高邮湖底泥及出入湖河口表层沉积物重金属分布特征,评价其潜在生态风险,以湖区及周边25个底泥和沉积物样品为载体,重点研究8种重金属元素,选用单因子污染指数法、内梅罗综合指数法、地累积指数法和潜在生态风险指数法,相似比对重金属污染等级及评价潜在生态风险。测试数据表明,8种重金属元素中,仅Hg含量(平均值)未超过里下河浅洼平原表层土壤重金属元素背景值,As含量(最大值)超过农用地土壤污染风险筛选值。Pearson相关系数矩阵表明,重金属元素Ni与Cr、Pb、Zn、Cu之间具显著同源性;单因子污染指数法与内梅罗综合指数法评价结果显示,污染指数均值排序均为As>Cd>Pb>Cu>Zn>Ni>Cr>Hg,但对As、Cd评价前者为轻度污染,后者为中度污染;地累积指数Igeo显示,仅As为轻度污染,其余元素均为无污染状态。沉积物单项潜在生态风险指数排序为Cd>Hg>As>Pb>Cu>Ni>Cr>Zn,仅Cd属中风险,其余元素为低风险;研究区综合潜在生态风险指数RI均值为115.7,表明全区总体生态风险属于低风险状态,重金属有沿入湖河口向湖心区富集趋势。  相似文献   

10.
The Pliocene aquifer receives inflow of Miocene and Pleistocene aquifer waters in Wadi El Natrun depression. The aquifer also receives inflow from the agricultural activity and septic tanks. Nine sediment samples were collected from the Pliocene aquifer in Wadi E1 Natrun. Heavy metal (Cu, Sr, Zn, Mn, Fe, Al, Ba, Cr, Ni, V, Cd, Co, Mo, and Pb) concentrations of Pliocene aquifer sediments were investigated in bulk, sand, and mud fractions. The determination of extractable trace metals (Cu, Zn, Fe, Mn, and Pb) in Pliocene aquifer sediments using sequential extraction procedure (four steps) has been performed in order to study environmental pathways (e.g., mobility of metals, bounding states). These employ a series of successively stronger chemical leaching reagents which nominally target the different compositional fractions. By analyzing the liquid leachates and the residual solid components, it is possible to determine not only the type and concentration of metals retained in each phase but also their potential ecological significance. Cu, Sr, Zn, Mn, Fe, and Al concentrations are higher in finer sediments than in coarser sediments, while Ba, Cr, Ni, V, Cd, Co, Mo, and Pb are enriched in the coarser fraction. The differences in relative concentrations are attributed to intense anthropogenic inputs from different sources. Heavy metal concentrations are higher than global average concentrations in sandstone, USEPA guidelines, and other local and international aquifer sediments. The order of trace elements in the bulk Pliocene aquifer sediments, from high to low concentrations, is Fe?>?Al?>?Mn?>?Cr?>?Zn?>?Cu?>?Ni?>?V?>?Sr?>?Ba?>?Pb?>?Mo?>?Cd?>?Co. The Pliocene aquifer sediments are highly contaminated for most toxic metals, except Pb and Co which have moderate contamination. The active soluble (F0) and exchangeable (F1) phases are represented by high concentrations of Cu, Zn, Fe, and Mn and relatively higher concentrations of Pb and Cd. This may be due to the increase of silt and clay fractions (mud) in sediments, which act as an adsorbent, retaining metals through ion exchange and other processes. The order of mobility of heavy metals in this phase is found to be Pb?>?Cd?>?Zn?>?Cu?>?Fe?>?Mn. The values of the active phase of most heavy metals are relatively high, indicating that Pliocene sediments are potentially a major sink for heavy metals characterized by high mobility and bioavailability. Fe–Mn oxyhydroxide phase is the most important fraction among labile fractions and represents 22% for Cd, 20% for Fe, 11% for Zn, 8% for Cu, 5% for Pb, and 3% for Mn. The organic matter-bound fraction contains 80% of Mn, 72% of Cu, 68% of Zn, 60% of Fe, 35% of Pb, and 30% of Cd (as mean). Summarizing the sequential extraction, a very good immobilization of the heavy metals by the organic matter-bound fraction is followed by the carbonate-exchangeable-bound fraction. The mobility of the Cd metal in the active and Fe–Mn oxyhydroxide phases is the highest, while the Mn metal had the lowest mobility.  相似文献   

11.
The Dongting Lake, the second biggest freshwater lake in China, consists of three wetlands of national importance, namely the East Dongting Lake, the South Dongting Lake, and the West Dongting Lake. Surface sedi-ments were sampled from 57 locations across the lake. Nutrient concentrations [total organic carbon (TOC), total N (TN) and total P (TP)] and 16 element concentrations (Al, As, B, Ca, Cd, Cr, Cu, K, Fe, Hg, Mn, Ni, Pb, Si, Ti and Zn) in the sediments were measured to investigate the impact of industrialization along the lake's coastline and sev-eral tributaries on the profiles of nutrients and heavy metals in the lake's surface sediments. R-mode cluster analysis (CA) was used to integrate geochemical data. The result showed that euthophication of the Dongting Lake resulted mainly from TN and TOC. The main polluting trace metals are Hg, As, Cd, Zn, Pb and Mn, which are largely ad-sorbed on clay minerals or Fe/Mn oxides, or deposited as carbonates. Principal component analysis (PCA) revealed the source of micropollutants. The worst affected district by heavy metals is the East Dongting Lake, the pollution sources may originate mainly from the Xiangjiang drainage area. The results demonstrated that multivariate methods are the potentially great tools for the interpretation of the environmental data on lake sediments.  相似文献   

12.
The sediments of City Park Lake (Baton Rouge, Louisiana, USA) are characterized by Pb concentrations that exceed the corresponding National Oceanic and Atmospheric Administration probable effect level by more than a factor of two and concentrations of As, Cd, Cu, Ni and Zn that exceed the corresponding threshold effect levels. The sediments of the lake are likely to be dredged because of concern over shoaling of the lake. There is concern that exposing these sediments to an oxidizing environment could mobilize toxic metal(loid)s that are effectively sequestered under reducing conditions. To address this concern, mixtures of sediments collected from seven locations in City Park Lake were incubated in microcosms under controlled oxidizing and reducing conditions. The slurries were sampled at time intervals over a period of nearly 750 h, and the dissolved Fe, Mn and trace metal concentrations determined. Eh and pH were negatively correlated, with Eh declining by 600 mV per unit increase in pH. Of the toxic metals, only the concentration of Cu was positively correlated with Eh, apparently because of the sequestration of Cu as a very insoluble sulfide precipitate under low Eh conditions. Precipitation of the other metals as sulfides was evidently insignificant because of the low S content of the sediments. Concentrations of the remaining potentially toxic metals were negatively correlated with Eh, apparently because of their sequestration as oxides and/or adsorption to Fe oxides or oxy-hydroxides. Concentrations of Ca, Mg, and Sr were positively correlated with Eh, presumably because of their sequestration in carbonate precipitates under low Eh/high pH conditions.  相似文献   

13.
为了解大亚湾表层沉积物中重金属的污染状况,对大亚湾海域23个点位表层沉积物中7种重金属元素(Cr、Ni、Cu、Pb、Zn、Cd、As)的质量分数、形态特征、来源控制因素以及潜在生态风险进行了研究。采用优化BCR提取法分析重金属元素赋存形态,并依据各种重金属元素的形态特征与沉积物基质属性进行了相关因子分析,了解其分布的控制因素。结果表明:大亚湾沉积物重金属元素呈现环带状分布特征,从岸向湾内逐渐减小;重金属元素质量分数的高值区主要分布于大鹏澳、哑铃湾及范和港附近;重金属元素赋存形态中Cr、Ni、Cu、Zn、As主要以残渣态存在,Pb主要以可还原态存在,Cd主要以酸提取态存在;7种重金属元素各自非残渣态所占比率从大到小为Pb(78.83%)、Cd(78.65%)、Cu(48.54%)、Zn(48.10%)、Ni(38.31%)、Cr(28.43%)、As(27.76%),即Pb最高,As最低,表明Pb的迁移性最强;通过因子分析,大亚湾重金属主要为沿岸自然风化产物的输入,其次为工业废水及养殖污水。运用酸提取态风险评估法对重金属元素潜在生态风险进行评价,发现研究区所选重金属元素综合风险评价Cd为高风险,其余重金属为中-低风险等级。  相似文献   

14.
The lakes of the Himalaya are degrading due to increase in toxic heavy metal loading. This study reports the last 50-year heavy metal pollution loading in the Rewalsar Lake, Himachal Pradesh, India. Sediment cores were recovered to study the pollution loading in the lake sediments. The 137Cs and 210Pb isotope-based sedimentation rate suggest rapid sedimentation in the lake during the last ~50 years. The concentrations of Mn, Cu, Zn, Cd, Pb, Co, Ni, Cr metals in the lake sediments owe its contributions both to the natural and anthropogenic sources. Prior to ca 1990 AD, metal loading was dominated by the lithogenic input, whereas post ca 1990 AD the metal loading was controlled by the anthropogenic factors. The Pb concentration in the lake gradually increased during 1990–2004 and then decreased significantly till present. The higher concentration of Pb seems to be derived from the fossil fuel burning, while the Cr concentration in the lake indicates the use of fertilizer in the catchment area. The lowest concentrations of elements around ca 1990 AD seem to have occurred due to channelization of the lake feeding system.  相似文献   

15.
This paper examines the surface sediments collected from Dongping Lake in China for speciation and distribution of toxic heavy metals (Cu, Pb, Ni, Cd) in different grain size fractions, and for the factors that need to be considered in potential hazard of metals to the environment. Four grain size fractions (<63, 63–78, 78–163 and 163–280 μm), divided in wet condition, and bulk samples less than 280 μm in diameter were analyzed for their distribution, density and appearance. A three-stage extraction procedure following the BCR protocol was used to chemically fractionate metals into “acid soluble”, “reducible”, “oxidizable” and “residual” fractions. Correlation analysis was used to analyze the datasets. The results showed that <63 μm grain size part constitutes the major proportion of the sediments, but its density is the smallest among the four grain size fractions. In general, the metal content curve against grain size presents “S” distribution, and the highest concentrations do not exist in <63 μm grain size. Appearance observation indicates that the adsorbed substance increases gradually along with the decreasing grain size. The dominant speciation of elements and the extent of pollution are responsible for the metal distribution in different grain size sediments. While studying bioavailability and mobilization of metals, it is advisable to take metal speciation, grain size distribution and density into consideration.  相似文献   

16.
太湖沉积物中重金属的测定及环境意义   总被引:38,自引:2,他引:38  
通过对太湖地区水域湖泊沉积物中重金属含量的抽样测试,描述了太湖水域重金属(Ag、As、Cd、Cr、Cu、Hg、Ni、Pb、Zn等)元素的污染状及其分布,结果表明:太湖沉积物中重金属含量北部明显高于东部,来自太湖北岸城镇和工业区的未处理工业及生活污水,对太湖北部水域造成的重金属污染程度远高于以养殖业为主的东太湖及湖心水域。  相似文献   

17.
研究目的】白洋淀为雄安新区核心生态功能区,为支撑白洋淀湿地生态修复与保护,系统开展了全淀区表层沉积物环境质量调查。【研究方法】在白洋淀湿地采集表层沉积物样品484组,查明了白洋淀表层沉积物重金属地球化学特征,并采用地累积指数法、潜在生态风险指数法等多种方法开展了重金属生态风险评价。【研究结果】白洋淀表层沉积物重金属含量普遍偏高于河北省表层土壤重金属含量背景值,府河入淀口及白沟引河入淀口为重金属元素主要富集区,入淀河流输入为白洋淀重金属主要来源;环境地球化学综合评价结果为清洁无污染等级分布面积144.54 km2,占表层沉积物分布总面积的96.68%;各重金属污染程度由重到轻排序为Cd>Cu>Hg>Pb>Zn>Ni>Cr>As,Cd元素污染程度等级以中度和偏中度为主,Cu元素以轻度和清洁为主,其他元素以清洁无污染为主;重金属潜在生态风险以轻度和中度为主,河流入淀口所在淀区重金属潜在生态风险高于其他淀区,潜在生态风险由高到低排序为南刘庄>烧车淀>小白洋淀>王家寨>藻苲淀>捞王淀>池鱼淀>泛鱼淀。【结论】白洋淀表层沉积物环境质量总体较好,南刘庄等局部淀区存在重金属污染潜在生态风险,以Cd元素污染最为突出。创新点:采用地累积指数法、潜在生态风险指数法等多种方法,系统评价白洋淀湿地表层沉积物重金属污染程度和生态风险;重金属地球化学特征分析与主成分分析法相结合,揭示表层沉积物重金属污染主要来源为河流输入。  相似文献   

18.
鲁静  李广玉  叶思源 《地球学报》2006,27(6):603-608
本文首先利用同站位多介质同采的资料分析研究了各环境介质中的不同痕量金属对生物富集的贡献,提出孔隙水中Pb、Zn、Cd、Cr对生物体中同名组分富集的贡献较大;进而采用PHREEQC软件模拟了孔隙水中Pb、Zn、Cd、Cr四种元素的组分存在形态,结果表明:PbCO3、Zn2 、CdCl2、Cr(OH)3分别为孔隙水中Pb、Zn、Cd、Cr的优势态,但其生物有效形态依次为PbSO4、ZnOHCl、CdCl 、Cr(OH)2 。最后作者提出生物对其所处环境介质中痕量金属的富集并不取决于痕量金属的总量或其相应的优势态浓度的多寡,而是取决于痕量金属的生物有效态的浓度大小。  相似文献   

19.
The behaviour of trace elements (Al, As, Cd, Co, Cr,Cu, Fe, Mn, Ni, V, Zn) was studied in five humus-richstreams (dissolved organic carbon = 14–40 mg/L)impacted by acid sulphate soils developed in marinesulphide-bearing fine-grained sediments. During heavyrainfalls in autumn, on which the study focusses, themetals Al, Cd, Co, Cu, Mn, Ni and Zn are extensivelyleached from these acidic soils (pH = 2.5–4.5), whileAs, Cr, Fe and V are not leached more strongly fromthis soil type than from areas of till and peat. Aspeciation experiment, based on anion and cationexchange of the stream waters in the field, showedthat (1) the metals Al, Cd, Co, Mn, Ni and Zn aretransported in the streams mainly as inorganiccations, (2) Cu exists mainly in cationic form but isalso to a significant extent associated with dissolvedhumic substances, (3) Fe occurs mainly in the anionicfraction explained by organic coating on colloidal Feoxyhydoxides and (4) the hydrochemistry of As, Cr andV is complex as these elements may exist in severalunquantified anionic fractions and to a minor extentin cationic species/forms. Whereas the proportion ofacid sulphate soils in the catchments had a largeimpact on concentrations levels of several elements inthe stream waters, these soils did not have a largeaffect on the speciation of elements in water.  相似文献   

20.
青岛胶州湾沉积物痕量元素黄铁矿化程度及其剖面类型   总被引:4,自引:0,他引:4  
为了探索青岛近海不同沉积环境下不同痕量元素的黄铁矿化规律, 2003年5月潜水员潜入海底采集了4个不同沉积环境的未扰动柱样, 并利用Huerta-Diaz and Morse (1990)连续提取技术测试分析了沉积物痕量金属的不同存在形式(活性态和黄铁矿结合态) 在垂直剖面上的分布规律.结果表明: 除了在涨潮三角洲上部沉积和潮下带沉积物柱子的Cd和Cr外, 痕量元素的黄铁矿化度的增高取决于其相应剖面上的DOP的增高; 并且不同痕量元素向黄铁矿中转移的规模存在着较大的差别, 即元素As、Hg和Mo转移的规模最大, Cu、Zn、Cd、Cr、Co和Ni中等, Pb和Mn最小; 此外, 还进一步揭示了河流三角洲沉积物的下部各元素的黄铁矿化程度高, 而潮下带沉积物以及涨潮三角洲沉积物低.最后指出在河口水下三角洲进行的清淤工作应注意黄铁矿结合态痕量元素的活化而产生生物有效的毒性元素.   相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号