• <tr id="yyy80"></tr>
  • <sup id="yyy80"></sup>
  • <tfoot id="yyy80"><noscript id="yyy80"></noscript></tfoot>
  • 99热精品在线国产_美女午夜性视频免费_国产精品国产高清国产av_av欧美777_自拍偷自拍亚洲精品老妇_亚洲熟女精品中文字幕_www日本黄色视频网_国产精品野战在线观看 ?

    Seasonal variations of phosphorus species in the Tuohe River,China. Part I. Sediments*

    2018-12-22 06:59:48XUQing徐青YUXiaoping余曉平GUOYafei郭亞飛DENGTianlong鄧天龍CHENYuWeiNelsonBELZILE
    Journal of Oceanology and Limnology 2018年6期
    關(guān)鍵詞:天龍

    XU Qing (徐青) , YU Xiaoping (余曉平) GUO Yafei (郭亞飛) DENG Tianlong (鄧天龍) , CHEN Yu-Wei , Nelson BELZILE

    1 Tianjin Key Laboratory of Marine Resources and Chemistry, College of Chemical Engineering and Materials Science, Tianjin University of Sciences and Engineering, Tianjin 300457, China

    2 School of Architecture and Civil Engineering, Chengdu University, Chengdu 610106, China

    3 Department of Chemistry and Biochemistry, Laurentian University, Sudbury, Ontario, P3E 2C6, Canada

    Abstract Sediment cores were collected at an upstream site (Jintang) and a downstream site (Neijiang)in summer and winter in the Tuohe River, which is one of the five largest tributaries of the Changjiang(Yangtze) River in China. A sequential leaching procedure was applied to determine the concentrations of the different forms of solid phosphorus, including exchangeable phosphorus (Exc-P) as well as phosphorus associated with iron oxides (Fe-P), with aluminum oxides (Al-P), with apatite (Ca-P) and with the residual fraction (Res-P), as correlated with water content and total organic carbon. The seasonal variations and the vertical distributions of phosphorus species in sediments at both sampling sites demonstrated that: 1) total phosphorus (TP) in summer and winter were ranged between 1 313–2 330, 1 491–2 228 mg/kg in Jintang and 543–2 128, 603–1 175 mg/kg in Neijiang, respectively. It can predicated the pollution of TP in Jintang is serious than that in Neijiang both in summer and winter; 2) total inorganic phosphorus (TIP) was the dominant form of TP; 3) Ca-P was the main chemical forms of TIP in the sediments. Based on the profiles in sediments and bio-available phosphorus data, it revealed that bio-available phosphorus (BAP) represented only a minor portion (0.61%–3.59%) of TP, and the vertical distribution of soluble reactive phosphorus(SRP) in corresponding porewaters was more abundant in the upper layer of the sediment, which suggests that BAP may be converted to non-bioavailable phosphorus in deeper layer of the sediment of this dynamic system.

    Keyword: phosphorus species; vertical distribution; seasonal variation; Tuohe River

    1 INTR ODUCTION

    In freshwater aquatic systems, phosphorus is considered as one of the most important nutrient elements for its role in relation to the growth of phytoplankton (Wang et al., 2006), but its excess loading from anthropogenic sources could cause eutrophication and vast phytoplankton bloom can then occur in oceans, lakes or rivers. Ryther and Yentsch (1957) found that phosphorus has a great influence on the growth of plankton communities.After the publication of that paper, the scientific community began to pay attention to the biogeochemistry of phosphorus in aquatic systems. In 1967, an International Symposium on Eutrophication was held in Madison, Wisconsin, USA. At that meeting, phosphorus was determined as the key and restrictive factor of eutrophication (Lund, 1967). In sediments, phosphorus exists under different forms that can be identified and classified using a sequential leaching procedure.

    Fig.1 Sampling sites at an upstream Jintang (north) and a downstream Neijiang (south) in the Tuohe River

    The sediment is the historical record of aquatic environments, and the interaction between sediment and overlying water via the sediment-water interface could allow the transport of phosphorus not only to this reservoir, but also make it a potential source to the overlying water. Therefore, the investigation of phosphorus species at the sediment-water interface is vital to understand the aquatic environment and the biogeochemical processes of nutrients.

    The Tuohe River is one of the five largest tributaries of the Changjiang (Yangtze) River in China. In this study, two sampling sites named Jintang and Neijiang located at the upstream and downstream sections of the river, respectively, were investigated. A series of samples including the sediments and associated porewaters were collected from the two sites in the summer and winter seasons. The different forms of inorganic and organic phosphorus and their vertical distributions in sediments were measured in order to reveal the vertical distribution of different phosphorus forms in surface sediments at different seasons as well as the geochemical characteristics of various phosphorus species in surface sediments in this aquatic system.

    2 EXPERIMENTAL SECTION

    2.1 Site description

    The Tuohe River, located in southwest China,flows through Chengdu, the capital of Sichuan Province (Fig.1), and constitutes one of the five largest tributaries of the Changjiang River. Samples were collected from the upstream in Jintang(104°31′19.0″E, 30°43′44.2″N) and the downstream in Neijiang (105°01′48.9″E, 29°35′49.8″N), in August 2006 and January 2007, respectively.

    2.2 Sediments sampling

    Sediment cores were collected by a diver using a PVC corer at the same sites where porewaters were collected at Jintang and Neijiang, making sure that the overlying water at the top of the core was clear and the surface of the sediment not disturbed. The overlying water was collected immediately in a 250 mL pre-cleaned polyethylene container. The sediments in the corer were sliced at each 1.0 cm and placed in pre-cleaned polyethylene containers using the method of coning and quartering. All sediment samples were stored in a glove-box bag filled with nitrogen gas to prevent oxidation and transported to the laboratory and kept frozen at -80℃ until analysis.

    2.3 Analysis of moisture, Total Organic Carbon(TOC) and phosphorus species

    To determine the percentage of moisture, about 5 g of sediment was put in a crucible and oven-dried at 105℃ for 24 h. The moisture content was calculated by weight difference. For TOC, about 0.5 g of dried sediment was heated in a muffle furnace at 750℃ for 4 h. After the sample has cooled down to room temperature in the desiccator, the weight difference was used to calculate the percentage of total organic carbon. Different fractions of inorganic phosphorus in sediments were extracted using the method of Zhu and Qin (2003). The extracted fractions can be classified as exchangeable-P (Exc-P), associated to iron oxides (Fe-P), to aluminum oxides (Al-P), to the apatite group (Ca-P) and to the residual fraction(Res-P) for the inorganic P and as organo-phosphorus compounds (Org-P). A flowchart of the sequential extraction for inorganic phosphorus in sediments is shown in Table 1. The total inorganic phosphorus(TIP), total organic phosphorus (TOP) and total phosphorus (TP) were measured using the Standards Measurements and Testing (SMT) method of the European Commission (Huang et al., 2004). The residual fraction (Res-P) was obtained from the difference between TP and TIP+TOP. The so called bio-available phosphorus (BAP) was estimated using the method of Liu et al. (2005) as 60% of the sum of Exc-P, Fe/Al-P and Org-P.

    The concentration of the various phosphorus species in sediments was determined using the spectrophotometric method of phospho-molybdenum blue (Fang, 2004), which is described in detail in the Chinese National Standards Methods (GB 17378.4-1998). The detection limit of this method is 0.2 μg/L,and the precision of this method is 2.1%.

    Table 1 The sequential extraction for inorganic phosphorus in sediments

    Fig.2 Profiles of phosphorus species, TOC and moisture content in sediment at the Jinta site of the Tuohe River in summer

    3 RESULT AND DISCUSSION

    3.1 Distributions of phosphorus species in sediment

    3.1.1 Distribution of phosphorus species in sediment at the Jintang site in summer

    Figure 2 shows that the concentration of Exc-P fluctuated from low background levels of 0.28 mg/kg to a maximum value of 43.7 mg/kg with a clear enrichment of Exc-P close to the surface of the sediment above -10 cm, with peaks appearing around-3 and -6 cm. The average concentration of Exc-P was 10.9 mg/kg, accounting for 0.9% of TIP. Although the Exc-P fraction is small, it is an important one since it is considered as the labile or available fraction of TIP that can be easily absorbed by aquatic organisms specifically because of the facilitated release of phosphorus from the sediment under the action of wind waves and benthic agitation. The moisture fluctuated from 26.6% to 44.2%, with an average value of 33.7%. TOC varied from 11.0% to 26.1%,with an average value of 18.4%, and both sets of values of moisture and TOC decreased with increasing depth.

    It has been shown (Xu et al., under review) that many measured parameters of the sediments such as Res-P (0.643), TP (0.649), moisture (0.745), TOC(0.434) and dissolved sulfide (0.561) were correlated with Exc-P in Table 2, suggesting that there are many factors influencing the concentration of Exc-P in this milieu. The fraction Exc-P also showed a positive correlation of 0.589 with soluble reactive phosphorus(SRP), indicating that SRP and Exc-P influence each other in the vertical distribution of phosphorus in the sediment. The Exc-P content of the upper layer of sediment shows large fluctuations, but it tends to be more stable below -10 cm (Fig.2). It can be related to the high moisture content of the upper layer of sediment where the interchange of phosphorus species between the porewaters and the sediment occur frequently, although the effects of wind waves or bioturbation cannot be excluded. However, the high correlation coefficient existing between Exc-P and moisture (R=0.745) reinforces the possible role of porewater for exchange of phosphorus species from the sediments either to the overlying water or to the different sediment layer as very likely. We can also speculate from the good correlation coefficient between Exc-P and dissolved sulfide (R=0.561) that a portion of the phosphorus may be released from the Al-P and Fe-P fractions under the reducing environment and diffused into porewater, while another portion is re-adsorbed in surface sediment to become part of the Exc-P.

    Table 2 Correlation coefficients ( R) among phosphorus species and other parameters of Jintang in summer, Tuo River

    Many studies have shown that organic matter and metal compounds are important factors affecting the distribution of phosphorus in sediments (Herlihy and McGrath, 2007; Zhao et al., 2017). Because of the difference of organic matter content and composition structure, the influence of the distribution characteristics of phosphorus in sediments was also significantly different. As shown in Table 2, TOC and the phosphorus species in sediments are positively correlated, and the correlation coefficient of TOC and Exc-P (0.434), Res-P (0.429), TP (0.433), SRP (0.441)suggesting that the organic matter affects the distribution of phosphorus, and the higher the TOC content , the higher the content of certain phosphorus forms.

    The presence of Al-P and Fe-P was not detectable at the Jintang site during the summer. Since the Al-P and Fe-P fractions are considered to belong to the bioavailable phosphorus, they are more easily influenced by the redox conditions of the environment and the phosphorus initially present in those two fractions can be released because of a change of the redox environment. The dynamic movements of rivers,being faster than those of lakes, combined to human activities frequently occurring in the Tuohe River, can cause the sediment to change and the Al-P and Fe-P fractions to release phosphorus from the sediment to the porewater.

    The concentration of Ca-P fluctuated from 609 to 980 mg/kg, and the average concentration of Ca-P was 798 mg/kg, accounting for 66.6% of TIP. Ca-P increased from the sediment-water interface to -9 cm,then decreased to reach a minimum at -12 cm at 609 mg/kg. It increased again from -12 to -20 cm with peaks appearing at -9 and -20 cm. The Exc-P refers to the weak adsorption of phosphorus, and the Fe-P refers to the redox-sensitive phosphorus, they are all relatively easy to release from the sediments and to be used by aquatic organisms under the environmental changes. This part of phosphorus plays a more active role in the geochemical cycle of phosphorus. The apatite group (Ca-P) is mainly derived from P combined with CaCO3, biogenic apatite, and antigenic carbonate fluorapatite (CFA)(Hou et al., 2009; Sekula-Wood et al., 2012; Yang et al., 2018). Phosphorus from the Ca-P sediment pool is relatively stable, and it’s less likely to be released from the sediments under the environmental changes such as redox, water stirring and temperature, and it is generally considered to be poorly used by aquatic organisms. In the process of early diagenesis, it was easy to be buried rather than to be released, and withdraw from the geochemical cycle of phosphorus temporarily. From this point of view, it can indirectly reflect the input status of phosphorus pollution over the historical period in this area.

    Table 3 Correlation coefficients ( R) among phosphorus species and other parameters of Jintang in winter, Tuohe River

    The concentration of TIP varied from 932 to 1 527 mg/kg and the average concentration was 1 198 mg/kg, accounting for 66.7% of TP. Finally, the concentration of Res-P varied from 133 to 1 085 mg/kg with an average concentration of 609 mg/kg,representing 33.9% of TP. The concentration of Res-P generally decreased with increasing depth. As its name indicates this residual fraction is considered relatively inert and not significantly soluble and bioavailable, so its impact on the environment is relatively small.

    Overall, the concentration of TP fluctuated from 1 313 to 2 330 mg/kg with an average concentration of TP being at 1 795 mg/kg with again the concentration of TP decreasing with depth. TOP was not detectable in the sediments of Jintang in summer. Li et al. (2004)found that sediments in the absence of organic and inorganic phosphorus contain only a small amount of organic carbon. It indicated the priority of organic phosphorus release from organic matter degradation.

    3.1.2 Distribution of phosphorus species in sediment at the Jintang site in winter

    Figure 3 presents the concentration of Exc-P,generally decreasing from 41.3 to 11.4 mg/kg with increasing depth, with an average value of 20.2 mg/kg, accounting for only 1.6% of TIP. The moisture content also decreased gradually from 54.9% to 27.4% with increasing depth and TOC remained relatively constant at an average value of 11.4%. The correlation coefficients among phosphorus species and other parameters are shown in Table 3.The higher content of Exc-P in the upper layer of the sediment was in a close correlation with moisture (R=0.863).However, the correlation between Exc-P and SRP (Xu et al., under review) was very poor (0.034), likely revealing that SRP in the porewater has little relationship with the possible release of phosphorus from Exc-P. The main source of phosphorus in the porewater at the Jintang site in winter is from external pollution as documented in an accompanying paper(Xu et al., under review). If we consider the phosphorus content at this site in summer as a background value, we can further speculate that the high phosphorus content in the porewater which came from external pollution had entered the geochemical cycle of phosphorus in the sediments in winter.

    The concentration of Al-P averaged 4.65 mg/kg(0.54–8.63 mg/kg), accounting for 0.37% of TIP and showing only small fluctuations with depth. The calculated correlation of -0.681 between Al-P and dissolved sulfide suggests that stronger reducing conditions were more favorable to the release of Al-P in the sediment in winter.

    Fe-P was not detectable. Ca-P was again the main component of TIP, with an average concentration of 1 109 mg/kg, representing 89.7%. Its concentration decreased slightly with the increase of depth, before increasing again below -14 cm. The concentration of TIP averaged 1 236 mg/kg, fluctuating between 992 and 1 463 mg/kg, and accounting for 71.0% of total phosphorus TP. The average concentration of Res-P was at 504 mg/kg (ranged from 257 to 898 mg/kg) or 29.0% of TP and that of TP was 1 740 mg/kg (ranged from 1 491 to 2 228 mg/kg).

    Fig.3 Profiles of phosphorus species, TOC and moisture content in sediment at the Jintang site of the Tuohe River in winter

    3.1.3 Distribution of phosphorus species in sediment at the Neijiang site in summer

    The profiles of phosphorus species are presented in Fig.4. The concentration of Exc-P oscillated from 11.0 to 38.1 mg/kg, generally increasing with depth.This labile fraction represented 2.5% of TIP with an average concentration of 21.9 mg/kg. The moisture content and the TOC level also increased with depth from 24.0% to 45.1%, and from 3.8% to 30.2%,respectively. These types of profiles increasing with depth at the Neijiang site differ from those at Jintang.The surficial sediments at Neijiang contained more sand than the upstream site, and this is likely the main factor affecting the vertical distribution of the various forms of phosphorus. Due to the large proportion of sandy sediments of the upper layer, the water content and TOC showed an increasing trend downward.From the vertical distribution of the various phosphorus forms, the maximum concentrations were found at around -10 cm where the junction of sandy and less sandy more muddy sediment exist. With a lower water content, sandy sediments have less contact with porewater than muddy sediments, and the exchange with the overlying flowing water is facilitated.

    Fig.4 Profiles of phosphorus species, TOC and moisture content in sediment at the Neijiang site of the Tuohe River in summer

    The concentrations of Al-P at the Neijiang site were very low (1.3–5.4 mg/kg), representing only 0.38% of TIP. Fe-P was not detectable and the concentration of Ca-P averaged 550 mg/kg,corresponding to 64.0% of TIP and also increasing with depth. The average concentration of TIP of 860 mg/kg represented 77.4% of TP. The concentration of TOP was very low in general, and lower in surficial sediments and only equivalent to 2.5% of TP. It was shown (Pang, 2004) that the SiO2content in sediment was negatively correlated with various forms of phosphorus and that a high percentage of sand in the sediment had a great influence on the distribution of phosphorus, especially for the content of TOP and Ca-P.

    Table 4 Correlation coefficients ( R) among phosphorus species and other parameters of Neijiang in summer, Tuohe River

    Finally, the concentration of Res-P represented 27.0% of TP with an average value of 301 mg/kg and that of TP averaged 1 111 mg/kg (543–2 128 mg/kg).

    The correlation coefficients among phosphorus species and other parameters are shown in Table 4.There were also showed some significant positive correlation between Exc-P and Ca-P (0.481), TOP(0.623), Res-P (0.544) and TP (0.570), and between TOC and Ca-P (0.505), TIP (0.503), and between Moisture and Ca-P (0.775), TIP (0.871), TOP (0.549),TP (0.552) and TOC (0.681). The organic matter controls the vertical distribution of different forms of phosphorus and the migration and transformation between them to some extent.

    3.1.4 Distribution of phosphorus species in sediment at the Neijiang site in winter

    The main forms of phosphorus as well as the moisture and TOC content all increased slightly with increasing depth at the Neijiang site in winter,similarly to the situation in summer at this location. It suggests that the mechanisms controlling the vertical distribution of phosphorus in sediments are similar to those operating in summer. Those mechanisms are very likely in close correlation with the special physical and chemical characteristics of the sandy sediments at this site. As shown in Fig.5, the proportion of Exc-P corresponded to only 2.0% of TIP with an average value of 16.6 mg/kg whereas that proportion was only 0.42% for Al-P and 0.04% for Fe-P. The largest fraction of phosphorus was still Ca-P representing 80.9% of TIP, which in turn counts for 90.3% of TP. As a result, the proportion of Res-P was only 0.8% of TP.

    The correlation coefficients among phosphorus species and other parameters are shown in Table 5.Significant calculated correlations between Exc-P and Fe-P (0.662), TIP (0.765), TP (0.808) and TOC(0.510), and between TIP and Fe-P (0.605) and Ca-P(0.914), and between TP and Exc-P (0.808), Fe-P(0.610), Ca-P (0.807) and TIP (0.925) indicate that the various forms of phosphorus contents are influenced by each other under certain conditions and can be transferred and transformed within the sediment pool of phosphorus.

    3.2 Vertical distribution characteristics of bioavailable phosphorus (BAP) at the two sampling sites

    BAP was estimated using the method of Liu et al.(2005) by taking 60% of the sum of Exc-P, Fe/Al-P and Org-P. BAP has an important guiding significance in the prediction of the potential ecological risk in the river. Figure 6 shows that the vertical distribution of BAP decreased with the increasing depth at the two sampling sites except for Neijiang in summer. It indicates that with the increase of depth, the phosphorus forms of BAP gets converted to nonactive and less bioavailable phosphorus in the sediment, which is consistent with the conclusions in another recent study (Zhang et al., 2006). The different trend observable at the Neijiang site during the summer is very likely related to the different nature of the sandy sediment at this particular location.

    Table 5 Correlation coefficients ( R) among phosphorus species and other parameters of Neijiang in winter, Tuohe River

    Fig.5 Profiles of phosphorus species, TOC and moisture content in sediment at the Neijiang site of the Tuohe River in winter

    Fig.6 Vertical distributions of BAP in sediment at the two sampling sites of the Tuohe River

    3.3 Spatial comparison of phosphorus forms in sediments of the two sampling sites

    The average contents of Ca-P, TIP and TP were higher at the Jintang than those at the Neijiang site in both summer and winter due to some local source of pollution at the first site. Studies have shown that with the increase of iron, aluminum, calcium and other metal compounds and organic matter content, the content of Fe/Al-P and Ca-P in the sediments also increased significantly (Igwe et al., 2010; Kleeberg et al., 2013). As shown in Tables 2 to 5, both Ca-P and TOC have a significant positive correlation (except for Jintang, summer). However, the contents of Exc-P,Al-P, Fe-P and TOP showed no clear trend at the two sampling sites, confirming that these forms of phosphorus are easily influenced by external factors such as wind waves and biological agitation, redox state changes, sediment characteristics and microbial activities. These various forms of phosphorus which belong to the BAP are easily absorbed to but also easily released from the sediment.

    The average content of BAP was higher at the Neijiang site in summer whereas it was higher at Jintang in winter. Similarly, the content of soluble reactive phosphorus (SRP) (Xu et al., under review)in porewater was higher at the Neijiang site in summer and higher at Jintang in winter, indicating that temporarily and spatially, the BAP in sediments has a close correlation with the SRP in porewater.

    3.4 Seasonal variations of phosphorus forms in sediments of the two sampling sites

    The main component of TP in the sediments both in summer and winter at the two sampling sites was TIP, many studies have come to the same conclusion(Li et al., 2004; Xiang and Zhou, 2011; M?ynarczyk et al., 2013). The difference is the main phosphorus form of inorganic phosphorus is not consistent, which may be related to the difference of composition of sediments and the sedimentary geological conditions in the different study area. In this study, inorganic phosphorus mainly existed as Ca-P. The concentrations of the various phosphorus fractions in sediments of the Tuohe River at the two sampling sites followed this order: TP > TIP > Ca-P > Res-P > Exc-P > Fe/Al-P. Through the comparison of the different forms of phosphorus in sediments in summer and winter we can see that the average contents of TP, TIP and Res-P in winter were lower than those in summer, and the content of Ca-P in winter was higher than that in summer. We suggest that the phosphorus released from the various forms in sediments in summer was converted to Ca-P and returned to the sediments. The content of BAP in winter was higher than that in summer at Jintang, whereas it was higher in summer than that in winter at Neijiang.

    4 CONCLUSION

    In the sediment samples collected at two sites on the Tuohe River, the concentrations of total phosphorus largely consisted of inorganic forms, and Ca-P was the most abundant fraction of TIP. The contents of phosphorus species in all four sediment cores followed the order: TP > TIP > Ca-P > Res-P >Exc-P > Fe/Al-P, and the concentrations of TP, TIP and Res-P were more abundant in summer than those in winter, whereas the concentrations of Ca-P were inversely more abundant in winter. Total phosphorus(TP) ranged from 1 313–2 330 mg/kg and 1 491–2 228 mg/kg in Jintang in summer and winter respectively; and ranged from 543–2 128 mg/kg and 603–1 175 mg/kg in Neijiang in summer and winter respectively.It can prediceted the pollution of P in Jintang is serious than that in Neijiang in both summer and winter. BAP represented only a minor portion of the total phosphorus as 0.6%–3.6%. A comparison of BAP with the vertical distributions of SRP, which were shown more abundant in the upper layer of the sediment and decreased in depths, suggests that BAP may be converted to non-bioavailable phosphorus and that some fractions of phosphorus are involved in the very dynamic system of the river sediments.

    5 ACKNOWLEDGEMENT

    Thanks to Dr. WU Y., Ms. WANG S. and Ms.ZHANG R. at Chengdu University of Technology for their active assistance in this work.

    猜你喜歡
    天龍
    不夠減怎么辦繪
    一個(gè)變五個(gè)
    同床異夢(mèng)
    Design of a novel correlative reflection electron microscope for in-situ real-time chemical analysis?
    萌娃趣語
    只有嘴巴想睡覺
    萌娃趣語
    DENON(天龍)DCD-50/PMA-60CD機(jī)/功放組合
    Antimony speciation at the sediment-water interface of the Poyang Lake: response to seasonal variation*
    Preface: Value and dynamics of salt lakes in a changing world
    久久精品久久久久久噜噜老黄| 又大又黄又爽视频免费| 色94色欧美一区二区| 国产又色又爽无遮挡免| 亚洲少妇的诱惑av| 欧美3d第一页| 熟女人妻精品中文字幕| 亚洲四区av| 久久 成人 亚洲| 黄片播放在线免费| 国产精品一区二区在线不卡| 国产国拍精品亚洲av在线观看| 免费播放大片免费观看视频在线观看| 免费观看a级毛片全部| 亚洲国产精品一区二区三区在线| 亚洲人成77777在线视频| 亚洲久久久国产精品| 蜜桃在线观看..| 大香蕉久久网| 亚洲成色77777| 少妇高潮的动态图| 99re6热这里在线精品视频| h视频一区二区三区| 久久久欧美国产精品| 日韩,欧美,国产一区二区三区| 欧美最新免费一区二区三区| 亚洲,欧美,日韩| 国产精品.久久久| av视频免费观看在线观看| 一区二区日韩欧美中文字幕 | 国产精品一二三区在线看| 麻豆乱淫一区二区| 少妇猛男粗大的猛烈进出视频| 五月开心婷婷网| 久久青草综合色| a级毛片黄视频| 伦理电影大哥的女人| 久久国产精品男人的天堂亚洲 | 亚洲熟女精品中文字幕| 欧美日韩成人在线一区二区| 日本av免费视频播放| 国产欧美日韩综合在线一区二区| 街头女战士在线观看网站| freevideosex欧美| 亚洲精品乱码久久久久久按摩| 2022亚洲国产成人精品| 亚洲精品视频女| 久久99一区二区三区| 老司机影院毛片| 国产白丝娇喘喷水9色精品| 亚洲经典国产精华液单| 亚洲欧美精品自产自拍| 一区二区三区精品91| 成人黄色视频免费在线看| 久久精品久久久久久噜噜老黄| 搡女人真爽免费视频火全软件| 中国三级夫妇交换| 亚洲国产欧美在线一区| 久久人人爽人人爽人人片va| 丰满迷人的少妇在线观看| 成人午夜精彩视频在线观看| 久久久久精品性色| 国产老妇伦熟女老妇高清| 久久久久国产精品人妻一区二区| 欧美日韩av久久| 免费黄色在线免费观看| 麻豆乱淫一区二区| 天天躁夜夜躁狠狠躁躁| 国产日韩欧美亚洲二区| 亚洲三级黄色毛片| 两个人免费观看高清视频| 国产不卡av网站在线观看| 另类亚洲欧美激情| 国产精品不卡视频一区二区| 捣出白浆h1v1| 成年人免费黄色播放视频| 国产毛片在线视频| 亚洲中文av在线| 成年美女黄网站色视频大全免费| 午夜福利网站1000一区二区三区| 亚洲av中文av极速乱| 街头女战士在线观看网站| 少妇被粗大猛烈的视频| 七月丁香在线播放| 国产精品人妻久久久影院| 中文精品一卡2卡3卡4更新| 国产亚洲最大av| 久久人人爽av亚洲精品天堂| 亚洲综合精品二区| 国产精品嫩草影院av在线观看| 成人无遮挡网站| 久久国内精品自在自线图片| 午夜激情av网站| 亚洲美女搞黄在线观看| 亚洲国产看品久久| 97超碰精品成人国产| 不卡视频在线观看欧美| 人人妻人人澡人人爽人人夜夜| 午夜福利网站1000一区二区三区| 日本av免费视频播放| 99热国产这里只有精品6| 大码成人一级视频| 国产精品国产三级国产av玫瑰| 免费不卡的大黄色大毛片视频在线观看| 国产一区亚洲一区在线观看| 人人澡人人妻人| 亚洲高清免费不卡视频| 欧美精品亚洲一区二区| 欧美日韩亚洲高清精品| 久久久a久久爽久久v久久| 欧美变态另类bdsm刘玥| 九草在线视频观看| 中文字幕人妻丝袜制服| 国产永久视频网站| 国产 一区精品| 亚洲av福利一区| 精品第一国产精品| 咕卡用的链子| 国产精品国产三级国产专区5o| 亚洲精品国产av蜜桃| 午夜影院在线不卡| 精品人妻在线不人妻| 精品人妻熟女毛片av久久网站| 国产av码专区亚洲av| 蜜臀久久99精品久久宅男| 26uuu在线亚洲综合色| 黑人猛操日本美女一级片| 中文字幕av电影在线播放| 成年人午夜在线观看视频| 欧美日韩亚洲高清精品| 久久精品熟女亚洲av麻豆精品| 欧美人与善性xxx| 免费女性裸体啪啪无遮挡网站| 这个男人来自地球电影免费观看 | 中文字幕亚洲精品专区| 精品国产一区二区久久| 亚洲av电影在线进入| 天天操日日干夜夜撸| 五月伊人婷婷丁香| 国产亚洲午夜精品一区二区久久| 最近中文字幕高清免费大全6| 国语对白做爰xxxⅹ性视频网站| 在线观看www视频免费| 国产淫语在线视频| 国产探花极品一区二区| 亚洲av日韩在线播放| 免费观看a级毛片全部| 免费在线观看黄色视频的| 国产男女内射视频| av在线播放精品| 一二三四在线观看免费中文在 | 亚洲欧美成人精品一区二区| www.av在线官网国产| 一级片免费观看大全| 日日撸夜夜添| 精品少妇久久久久久888优播| 亚洲四区av| 免费黄网站久久成人精品| 欧美激情 高清一区二区三区| 中文字幕人妻丝袜制服| av播播在线观看一区| 一本—道久久a久久精品蜜桃钙片| 亚洲精品久久午夜乱码| 丰满少妇做爰视频| 国产亚洲一区二区精品| 日本91视频免费播放| 尾随美女入室| 母亲3免费完整高清在线观看 | 边亲边吃奶的免费视频| 日本vs欧美在线观看视频| 人人妻人人添人人爽欧美一区卜| 久久久久网色| 极品少妇高潮喷水抽搐| 十八禁网站网址无遮挡| 一级,二级,三级黄色视频| av片东京热男人的天堂| 在线观看国产h片| 曰老女人黄片| 久久久a久久爽久久v久久| 在线精品无人区一区二区三| 交换朋友夫妻互换小说| 亚洲国产精品专区欧美| 国产视频首页在线观看| 王馨瑶露胸无遮挡在线观看| 久久国内精品自在自线图片| 99久久人妻综合| 伦理电影大哥的女人| 91aial.com中文字幕在线观看| 伦理电影免费视频| 亚洲综合精品二区| 中文字幕免费在线视频6| 欧美+日韩+精品| 美女大奶头黄色视频| 亚洲av.av天堂| 国产成人免费无遮挡视频| 激情视频va一区二区三区| 精品一品国产午夜福利视频| 你懂的网址亚洲精品在线观看| 亚洲欧美成人综合另类久久久| 人人妻人人添人人爽欧美一区卜| 久久人人爽人人片av| 精品一品国产午夜福利视频| 寂寞人妻少妇视频99o| 观看av在线不卡| 欧美精品av麻豆av| 丰满少妇做爰视频| 欧美 日韩 精品 国产| 久久狼人影院| 国产av精品麻豆| 极品人妻少妇av视频| 卡戴珊不雅视频在线播放| 丝袜在线中文字幕| 欧美+日韩+精品| 国产极品天堂在线| 亚洲精品乱久久久久久| 嫩草影院入口| 午夜精品国产一区二区电影| 精品人妻熟女毛片av久久网站| 汤姆久久久久久久影院中文字幕| 又粗又硬又长又爽又黄的视频| 亚洲高清免费不卡视频| 国产深夜福利视频在线观看| 免费大片黄手机在线观看| 国产精品国产三级专区第一集| 2018国产大陆天天弄谢| 日本欧美国产在线视频| 亚洲精品一区蜜桃| 亚洲,欧美精品.| 欧美精品一区二区大全| 国产亚洲欧美精品永久| 性色avwww在线观看| 妹子高潮喷水视频| 久久狼人影院| 久久久久久久久久久久大奶| 亚洲内射少妇av| 国产精品一区www在线观看| 丝袜喷水一区| 国产在线免费精品| 免费在线观看黄色视频的| 午夜福利视频精品| 国产亚洲一区二区精品| 蜜桃在线观看..| 精品国产露脸久久av麻豆| 九色成人免费人妻av| 免费日韩欧美在线观看| 精品人妻一区二区三区麻豆| 99视频精品全部免费 在线| 一级毛片 在线播放| 国产成人a∨麻豆精品| 国产精品蜜桃在线观看| 看十八女毛片水多多多| 免费观看a级毛片全部| 日日爽夜夜爽网站| 国产欧美日韩一区二区三区在线| 看免费成人av毛片| 亚洲婷婷狠狠爱综合网| 曰老女人黄片| 亚洲第一av免费看| 免费女性裸体啪啪无遮挡网站| 爱豆传媒免费全集在线观看| 亚洲欧美清纯卡通| 欧美97在线视频| 午夜福利网站1000一区二区三区| av免费在线看不卡| 我要看黄色一级片免费的| 亚洲伊人色综图| 精品酒店卫生间| 日韩精品有码人妻一区| 亚洲,一卡二卡三卡| 亚洲国产欧美日韩在线播放| 国产成人精品福利久久| 色婷婷av一区二区三区视频| 亚洲欧美日韩卡通动漫| 日韩制服丝袜自拍偷拍| 波野结衣二区三区在线| 菩萨蛮人人尽说江南好唐韦庄| 日日爽夜夜爽网站| 亚洲av在线观看美女高潮| 欧美xxⅹ黑人| 精品午夜福利在线看| 下体分泌物呈黄色| 日韩一区二区视频免费看| 母亲3免费完整高清在线观看 | 日本午夜av视频| 午夜免费鲁丝| 中文字幕制服av| 国产男女超爽视频在线观看| 日本vs欧美在线观看视频| 久久精品国产综合久久久 | 日韩制服骚丝袜av| 男男h啪啪无遮挡| 极品少妇高潮喷水抽搐| 熟女电影av网| 日韩中文字幕视频在线看片| 亚洲欧美清纯卡通| 亚洲三级黄色毛片| 国产精品 国内视频| 黑人猛操日本美女一级片| 狂野欧美激情性bbbbbb| 亚洲精品久久成人aⅴ小说| 日本免费在线观看一区| 各种免费的搞黄视频| 欧美国产精品va在线观看不卡| 亚洲精品久久成人aⅴ小说| 美女大奶头黄色视频| 中文字幕最新亚洲高清| 国产黄色视频一区二区在线观看| 18+在线观看网站| 街头女战士在线观看网站| 黄片播放在线免费| 在线免费观看不下载黄p国产| 免费黄频网站在线观看国产| 精品国产一区二区三区久久久樱花| 免费不卡的大黄色大毛片视频在线观看| 9热在线视频观看99| 一区二区日韩欧美中文字幕 | 男女边吃奶边做爰视频| 久久久久精品性色| 国产成人午夜福利电影在线观看| 国产精品一国产av| 久久 成人 亚洲| 久久精品国产鲁丝片午夜精品| 亚洲精品aⅴ在线观看| 亚洲国产精品一区三区| 亚洲精品456在线播放app| 伦理电影大哥的女人| 日韩制服骚丝袜av| 性色avwww在线观看| 亚洲第一av免费看| 欧美精品一区二区大全| 日本猛色少妇xxxxx猛交久久| 人妻系列 视频| 国产一区二区三区综合在线观看 | 另类精品久久| 欧美最新免费一区二区三区| 国产精品人妻久久久影院| 秋霞在线观看毛片| 国产欧美亚洲国产| 成人国语在线视频| 曰老女人黄片| 国产探花极品一区二区| 国产成人91sexporn| 国产在视频线精品| 国产免费又黄又爽又色| 男女啪啪激烈高潮av片| 久久人人爽av亚洲精品天堂| 乱人伦中国视频| 纵有疾风起免费观看全集完整版| 一级a做视频免费观看| 亚洲精品456在线播放app| 伦理电影大哥的女人| 色吧在线观看| 亚洲人与动物交配视频| 少妇的逼水好多| 香蕉国产在线看| 美女福利国产在线| tube8黄色片| 日本与韩国留学比较| 嫩草影院入口| 成年女人在线观看亚洲视频| av在线观看视频网站免费| 久久国产亚洲av麻豆专区| 男女午夜视频在线观看 | 91精品国产国语对白视频| 欧美精品高潮呻吟av久久| 国产免费一级a男人的天堂| 成人18禁高潮啪啪吃奶动态图| 18禁观看日本| 制服丝袜香蕉在线| 成人漫画全彩无遮挡| 久久精品国产a三级三级三级| 国产精品 国内视频| 在线观看免费高清a一片| 精品一区二区三卡| 国产精品国产三级专区第一集| 一区二区三区四区激情视频| av在线老鸭窝| 亚洲精品久久久久久婷婷小说| 美女内射精品一级片tv| 久久狼人影院| 美女主播在线视频| 日韩免费高清中文字幕av| 97超碰精品成人国产| 又大又黄又爽视频免费| 亚洲国产色片| 在线天堂中文资源库| 日韩三级伦理在线观看| 国产乱来视频区| 你懂的网址亚洲精品在线观看| 成人18禁高潮啪啪吃奶动态图| 亚洲国产精品国产精品| 国产精品国产av在线观看| 国产一区二区三区av在线| 午夜老司机福利剧场| 尾随美女入室| 色吧在线观看| 国产亚洲一区二区精品| 精品国产一区二区三区久久久樱花| 欧美国产精品一级二级三级| 免费看av在线观看网站| 中文字幕另类日韩欧美亚洲嫩草| 亚洲成国产人片在线观看| 9191精品国产免费久久| 久久精品熟女亚洲av麻豆精品| 在线天堂最新版资源| 一本—道久久a久久精品蜜桃钙片| 国产 精品1| 国产一区二区三区综合在线观看 | 精品人妻一区二区三区麻豆| 一级片免费观看大全| av国产久精品久网站免费入址| 国产成人午夜福利电影在线观看| 亚洲av成人精品一二三区| 韩国av在线不卡| 色网站视频免费| 久久久久人妻精品一区果冻| 老女人水多毛片| av在线观看视频网站免费| 中文字幕精品免费在线观看视频 | 久久综合国产亚洲精品| 国产精品久久久av美女十八| 波多野结衣一区麻豆| 国产精品99久久99久久久不卡 | a 毛片基地| 欧美最新免费一区二区三区| 美女xxoo啪啪120秒动态图| 巨乳人妻的诱惑在线观看| 亚洲熟女精品中文字幕| 国产精品嫩草影院av在线观看| 精品少妇黑人巨大在线播放| 国产国拍精品亚洲av在线观看| 欧美成人精品欧美一级黄| 亚洲av日韩在线播放| 一二三四中文在线观看免费高清| 成年女人在线观看亚洲视频| 欧美日韩成人在线一区二区| 人妻人人澡人人爽人人| 熟女av电影| 黑人高潮一二区| 丝瓜视频免费看黄片| 亚洲av国产av综合av卡| 中文字幕精品免费在线观看视频 | 久久韩国三级中文字幕| 免费在线观看完整版高清| 大片电影免费在线观看免费| videos熟女内射| av免费观看日本| 99热全是精品| 日本免费在线观看一区| 久久婷婷青草| 国产成人精品福利久久| 91久久精品国产一区二区三区| 午夜福利视频在线观看免费| 两性夫妻黄色片 | 午夜免费男女啪啪视频观看| 99久久中文字幕三级久久日本| 亚洲国产成人一精品久久久| 超色免费av| 熟女人妻精品中文字幕| 香蕉丝袜av| 高清不卡的av网站| 亚洲精华国产精华液的使用体验| 国产男人的电影天堂91| 国产乱人偷精品视频| 91aial.com中文字幕在线观看| 最近2019中文字幕mv第一页| 欧美xxⅹ黑人| 成人无遮挡网站| 精品酒店卫生间| 观看美女的网站| 欧美激情 高清一区二区三区| 少妇的逼好多水| 丁香六月天网| 日本vs欧美在线观看视频| 狠狠精品人妻久久久久久综合| 日产精品乱码卡一卡2卡三| 成年人午夜在线观看视频| 熟女电影av网| 王馨瑶露胸无遮挡在线观看| 国产一区二区激情短视频 | 中文字幕人妻熟女乱码| 天堂俺去俺来也www色官网| 精品人妻偷拍中文字幕| 亚洲精品国产av成人精品| 久久女婷五月综合色啪小说| 久久精品久久精品一区二区三区| a级片在线免费高清观看视频| 国产精品人妻久久久影院| 久久久国产欧美日韩av| 精品国产一区二区久久| 亚洲国产成人一精品久久久| 在线观看免费日韩欧美大片| 99热6这里只有精品| 一级,二级,三级黄色视频| 欧美国产精品va在线观看不卡| 熟女电影av网| 国语对白做爰xxxⅹ性视频网站| 女性生殖器流出的白浆| 久久精品久久精品一区二区三区| 欧美+日韩+精品| 精品第一国产精品| 97超碰精品成人国产| 国产精品欧美亚洲77777| 欧美97在线视频| 一本—道久久a久久精品蜜桃钙片| 内地一区二区视频在线| 美女主播在线视频| 亚洲成人一二三区av| 国产一区二区三区av在线| 国产乱来视频区| 超色免费av| 国产亚洲一区二区精品| 亚洲精品自拍成人| 免费黄色在线免费观看| 欧美精品人与动牲交sv欧美| a级毛片黄视频| 亚洲av日韩在线播放| 老司机亚洲免费影院| 欧美日韩一区二区视频在线观看视频在线| 热re99久久国产66热| 国产一区二区激情短视频 | 欧美激情极品国产一区二区三区 | 欧美+日韩+精品| 黑人欧美特级aaaaaa片| 一本一本久久a久久精品综合妖精 国产伦在线观看视频一区 | 满18在线观看网站| 热99国产精品久久久久久7| 制服丝袜香蕉在线| 免费日韩欧美在线观看| 国产免费福利视频在线观看| 国产精品久久久久成人av| 人人妻人人澡人人爽人人夜夜| 国精品久久久久久国模美| 日本黄色日本黄色录像| 久久99热这里只频精品6学生| 国产毛片在线视频| 观看美女的网站| 亚洲精品美女久久久久99蜜臀 | 9191精品国产免费久久| 女人久久www免费人成看片| av国产精品久久久久影院| 十八禁网站网址无遮挡| 啦啦啦中文免费视频观看日本| 久久鲁丝午夜福利片| 日本爱情动作片www.在线观看| 91精品三级在线观看| 日本猛色少妇xxxxx猛交久久| 成年动漫av网址| 男女国产视频网站| 国产又色又爽无遮挡免| 搡老乐熟女国产| 伦精品一区二区三区| 久久97久久精品| 精品酒店卫生间| 毛片一级片免费看久久久久| 免费高清在线观看日韩| 一区二区三区乱码不卡18| 亚洲av日韩在线播放| 曰老女人黄片| 1024视频免费在线观看| 青春草国产在线视频| av免费观看日本| 在线亚洲精品国产二区图片欧美| 69精品国产乱码久久久| 久久久久久久大尺度免费视频| 欧美bdsm另类| 亚洲av在线观看美女高潮| 国产成人免费观看mmmm| 国产精品久久久av美女十八| 亚洲av福利一区| 亚洲三级黄色毛片| 精品久久国产蜜桃| 国产精品国产av在线观看| 欧美性感艳星| 日本黄色日本黄色录像| 黄色毛片三级朝国网站| 90打野战视频偷拍视频| 精品久久久精品久久久| 在线看a的网站| 九色亚洲精品在线播放| 免费高清在线观看视频在线观看| 亚洲av综合色区一区| 国产欧美日韩综合在线一区二区| 国产乱人偷精品视频| 777米奇影视久久| 成年女人在线观看亚洲视频| 中文字幕最新亚洲高清| 蜜桃在线观看..| av国产精品久久久久影院| 女性生殖器流出的白浆| 美国免费a级毛片| 亚洲av欧美aⅴ国产| 99热这里只有是精品在线观看| 中文欧美无线码| 国产爽快片一区二区三区| 久久这里只有精品19| 久久久久久久亚洲中文字幕| 精品久久国产蜜桃| 国产成人一区二区在线| av卡一久久| 亚洲av电影在线进入| 免费日韩欧美在线观看| 男女免费视频国产| 欧美xxxx性猛交bbbb| 久久99蜜桃精品久久| 韩国精品一区二区三区 | 中文字幕制服av| 亚洲国产精品专区欧美| 男人添女人高潮全过程视频| 国产日韩一区二区三区精品不卡| 99re6热这里在线精品视频| 午夜免费鲁丝| 黄色配什么色好看| 国产免费视频播放在线视频| 国产一区二区三区综合在线观看 |