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 31 毫秒
1.
Submarine groundwater discharge (SGD) is now recognized as an important pathway for water and chemical species fluxes to the coastal ocean. In order to determinate SGD to the Gulf of Lion (France), we measured the activities of 226Ra and 228Ra by thermal ionization mass spectrometry (TIMS) in coastal waters and in the deep aquifer waters of the Rhone deltaic plain after pre-concentration of radium by MnO2. Compared to conventional counting techniques, TIMS requires lower quantities of water for the analyses, and leads to higher analytical precision. Radium isotopes were thus measured on 0.25–2 L water samples containing as little as 20 fg of 226Ra and 0.2–0.4 fg of 228Ra with precision equal to 2%. We demonstrate that coastal surface waters samples are enriched in 226Ra and 228Ra compared to the samples further offshore. The high precision radium measurements display a small but significant 226Ra and 228Ra enrichment within a strip of circa 30 km from the coast. Radium activities decrease beyond this region, entrained in the northern current along the shelf break or controlled by eddy diffusion. The radium excess in the first 30 km cannot be accounted for by the river nor by the early diagenesis. The primary source of the radium enrichment must therefore be ascribed to the discharge of submarine groundwater. Using a mass-balance model, we estimated the advective fluxes of 226Ra and 228Ra through SGD to be 5.2 × 1010 and 21 × 1010 dpm/d respectively. The 226Ra activities measured in the groundwater from the Rhone deltaic plain aquifer are comparable to those from other coastal groundwater studies throughout the world. By contrast, 228Ra activities are higher by up to one order of magnitude. Taking those groundwater radium activities as typical of the submarine groundwater end-member, a minimum volume of 0.24–4.5 × 1010 l/d is required to support the excess radium isotopes on the inner shelf. This has to be compared with the average rivers water runoff of 15.4 × 1010 l/d during the study period (1.6 to 29% of the river flow).  相似文献   

2.
The input of groundwater-borne nutrients to Adelaide's (South Australia) coastal zone is not well known but could contribute to the ongoing decline of seagrass in the area. As a component of the Adelaide Coastal Waters Study (ACWS), the potential for using the radium quartet (223Ra, 224Ra, 226Ra and 228Ra) and 222Rn to evaluate submarine groundwater discharge (SGD) was evaluated. Potential isotopic signatures for SGD were assessed by sampling groundwater from three regional aquifers potentially contributing SGD to the ACWS area. In addition, intertidal groundwater was sampled at two sand beach sites. In general, the regional groundwaters were enriched in long-lived Ra isotopes (226Ra and 228Ra) and in 222Rn relative to intertidal groundwater. Radium activity (but not 222Rn activity) was positively correlated to salinity in groundwater from one of the regional aquifers and in intertidal groundwater. Radium isotope ratios (223Ra/226Ra, 224Ra/226Ra and 228Ra/226Ra) were less variable than individual Ra isotope activities within potential SGD sources. Recirculated seawater (estimated from the intertidal groundwater samples with seawater-like salinities) also had distinctly higher Ra isotope ratios than the regional groundwaters. The activities for all radioisotopes were relatively low in seawater. The activity of the short-lived 223Ra and 224Ra were highest at the shoreline and declined exponentially with distance offshore. In contrast, 228Ra and 226Ra activities had a weak linear declining trend with distance offshore. Rn-222 activity was at or near background in all seawater samples. The pattern of enrichment in short-lived Ra isotopes and the lack of 222Rn in seawater suggest that seawater recirculation is the main contributor to SGD in the ACWS area. Preliminary modeling of the offshore flux of 228Ra and 226Ra suggest that the SGD flux to the ACWS area ranges between 0.2 and 3 · 10− 3 m3 (m of shoreline)− 1 s− 1.  相似文献   

3.
基于223Ra和224Ra的桑沟湾海底地下水排放通量   总被引：1，自引：0，他引：1  
海底地下水排放（SGD）是陆地向海洋输送水量和营养物质的重要通道之一,对沿海物质通量及其生物地球化学循环有重要的影响,对生态环境起着不可忽视的作用。本文运用天然放射性同位素223Ra和224Ra示踪估算了我国北方典型养殖基地桑沟湾的海底地下水排放通量。结果表明,海底地下水样尤其是间隙水中Ra活度[224Ra=（968±31）dpm/（100 L）,223Ra=（31.4±4.9）dpm/（100 L）,n=9]远高于表层海水[224Ra=（38.7±2.0）dpm/（100 L）,223Ra=（1.70±0.50）dpm/（100 L）, n=21]。假设稳态条件下,考虑Ra的各源、汇项,利用Ra平衡模型,估算出桑沟湾SGD排放通量为（0.23~1.03）×107 m3/d。潮周期内的观测结果显示,涨潮时,水力梯度较小,SGD排放变弱,落潮时,水力梯度较大,导致了相对较多的SGD排放。在一个潮周期间,基于223Ra和224Ra得到的SGD排放通量平均为0.39×107 m3/d。潮汐动力下的SGD排放平均占总SGD排放的61%,因此桑沟湾沿岸的地下水排放主要受潮汐动力的影响,并对海水组成及海陆间物质交换有显著贡献。  相似文献   

4.
The short-lived radium isotopes, 223Ra (T1/2 = 11.4 days) and 224Ra (T1/2 = 3.66 days), have been successfully used as tracers of several environmental processes, e.g., submarine groundwater discharge, coastal mixing processes, and water residence times. In this paper, the uncertainties associated with 223Ra and 224Ra measurements using a Radium Delayed Coincidence Counter are determined on a detailed error propagation basis with a confidence interval of 1σ. From the data analyses of several groups of coastal water samples, the calculated relative uncertainties averaged 12% for the 223Ra and 7% for the 224Ra. These uncertainties can decrease for radium-enriched groundwater samples although asymptotic limits have been found at 7% relative uncertainty for 223Ra and 4% for 224Ra. In this paper, the influence of sampling and measurement parameters on the final radium uncertainties is evaluated in order to provide guidance to optimize these factors and obtain more reliable results.  相似文献   

5.
海底地下水排放(SGD)是近海海域的一个重要的营养盐来源。本研究借助多种天然镭同位素对春季苏北浅滩海域的SGD及其携带入海的营养盐通量进行量化评估。研究发现:苏北浅滩海域的~(224)Ra、~(223)Ra和~(226)Ra等镭同位素的浓度水平较高,呈现近岸高、远岸低的分布趋势;根据~(224)Ra/~(226)Ra的"表观年龄模型"估算的水龄的分布情况推断,春季该海域表层水体主体流向为东北向,流速约为0.1m/s,这与前人物理海洋数值模拟结果一致;最终利用226Ra质量平衡模型发现海域的SGD通量为(46±29)cm/d,由其携带入海的溶解态无机氮、磷、硅营养盐(DIN、 DIP、 DSi)等的通量分别为(2.6±3.1)×1~09、(3.0±2.5)×10~6和(5.5±4.2)×10~8mol/d。  相似文献   

6.
In the current study, low-background γ-spectrometry was employed to determine the 228Ra/226Ra activity ratio and 137Cs activity of 84 coastal water samples collected at six sites along the main island of Japan (Honshu Island) within the Sea of Japan, including the Tsushima Strait, and two other representative sites on Honshu Island (a Pacific shore and the Tsugaru Strait) at 1-month intervals in 2006.The 228Ra/226Ra ratio of coastal waters in the Sea of Japan exhibited similar patterns of seasonal variation, with minimum values during early summer (228Ra/226Ra = 0.6–0.8), maximum values during autumn (228Ra/226Ra = 1.5–3), and a time lag in their temporal changes ( 2.5 months and over  1300 km distance). However, the 2 other sites represented no clear periodic variation.In contrast to the positive correlation between 137Cs activity (0.6–1.7 mBq/L) and salinity (15–35), the 228Ra/226Ra ratio of coastal water samples from the Sea of Japan was not observed to correlate with salinity, and the increase in the 228Ra/226Ra ratio was not as marked (0.5–1; May–June 2004 and 2005) during the migration along Honshu Island. The input of land-derived water and/or the diffusion of radium from coastal sediments is unlikely to have affected the wide seasonal variation in the 228Ra/226Ra ratio observed in these water samples.The seasonal variation in the 228Ra/226Ra ratio recorded for the coastal waters of the Sea of Japan is considered to be mainly controlled by the remarkable changes in the mixing ratio of the 228Ra-poor Kuroshio and the 228Ra-rich continental shelf waters within the East China Sea (ECS). After passing through the Tsushima Strait, this water mass moves northeast along the coastline of the Sea of Japan as the Tsushima Coastal Branch Current (TCBC).  相似文献   

7.
北黄海水体的226Ra和228Ra   总被引：1，自引：0，他引：1  
王芬芬  门武  刘广山 《台湾海峡》2010,29(2):265-276
用锰纤维富集-射气法测定了北黄海海水中的镭同位素226Ra和228Ra,研究了该海域水体中镭同位素的含量和分布.研究结果表明北黄海水体夏季226Ra的比活度为1.80～4.35 Bq/m3,平均值为3.06 Bq/m3;冬季226Ra的比活度为2.08～5.20 Bq/m3,平均值为3.28 Bq/m3.北黄海夏季228Ra的比活度为3.85～25.60 Bq/m3,平均值为10.60 Bq/m3;冬季228Ra的比活度为3.14～15.60Bq/m3,平均值为7.66 Bq/m3.该数据范围和中国近海其他海域、孟加拉湾、泰国昭披耶河口、濑户内海等海域相近.北黄海东北部海域,渤海海峡靠近山东半岛的海区和中北部海区表层镭同位素活度较高.C1断面镭同位素的分布特征从镭同位素的方面证实了渤海海峡水交换表现为北进南出特征这一结论的正确性.226Ra和228Ra的垂直分布较为复杂,大部分站位呈现出底层活度变高的趋势,其他少数站位呈现出中间层活度高的分布特征,不同来源的镭同位素输入至该海域形成了这样的分布特征.  相似文献   

8.
Coastal waters contain elevated dissolved activities of short-lived radium isotopes, 223Ra and 224Ra, having half-lives of 11.4 and 3.66 days, respectively. The input of these isotopes near the coast must be balanced by decay and mixing into the open ocean, where excess activities are zero. Since the decay rate is known, in the ideal case the mixing rate may be determined from the offshore distribution of these isotopes. This study found that samples collected in June 2000 followed the expected exponential decrease with distance offshore. We assign a dispersion coefficient of 28–39 m2 s−1 for this study. During January 2002 and November 2003, there was not a consistent decrease of activity with distance offshore. This is likely due to the ruggedness of the coastline, where many bays and small islands interrupt simple mixing patterns. To estimate exchange rates during 2002 and 2003, we used a model based on the decrease in the 224Ra/223Ra activity ratio (AR) with time for samples isolated from fresh inputs of Ra. This model yielded residence times of 1–2 weeks for samples collected within 20 km of the coast. We used this residence time to calculate the flux of 228Ra (half-life = 5.7 years) to the study area necessary to maintain the enrichment relative to ocean water. This enrichment is a factor of ten greater than the flux of 228Ra expected from submarine groundwater discharge (SGD) occurring within 50 m of shore.  相似文献   

9.
《Marine Chemistry》2007,103(1-2):131-145
We have investigated submarine groundwater discharge to Nueces Bay (Texas) using naturally occurring Ra isotopes. Dissolved Ra activities in Nueces Bay are among the highest observed in coastal estuaries; as great as 2600 dpm m− 3 for 228Ra and 1000 dpm m− 3 for 226Ra. Using a combination of salt and Ra mass balances, we demonstrate that river discharge and bay bottom sediments cannot supply the Ra needed to balance tidal export. In the case of 226Ra there is an additional source of 218 × 106 ± 105% dpm day− 1 which is 9 times the maximum supply from bay bottom sediments and 50 times the Ra supplied by the Nueces River. A groundwater flux of 310,000 m3 day− 1 is required to supply the needed 226Ra, based on the measured maximum Ra activity of local groundwater. Though as little as 10% of this flux may be advecting terrestrial groundwater this would still represent 160% of the Nueces River discharge. This makes it unlikely that groundwater discharge alone is supplying all of the additional 226Ra. Oil-field brine could potentially account for the remainder. Leakage of 6290 m3 day− 1 of oil-field brine from the submerged petroleum wells and pipelines within the bay could supply all of the needed 226Ra. Such large fluxes of brackish groundwater and oil-field brine could significantly affect bay nitrogen budgets, salinities, and dissolved oxygen concentrations and should be considered when determining the freshwater inflow requirements for Nueces Bay and similar estuaries.  相似文献   

10.
The four naturally-occurring radium isotopes (223Ra, 224Ra, 226Ra and 228Ra) were used to estimate the submarine groundwater discharge (SGD) in the Isola La Cura marsh area in the northern Venice Lagoon (Italy). By determining the radium contributors to the study area (river, coastal ocean and sediments) the radium excess in the lagoon water was quantified through a mass balance model. This radium excess is attributed to a submarine groundwater discharge source and represents the most important input of radium. Possible endmembers were considered from analysis of groundwater samples (subtidal and marsh piezometers, marsh wells and seepage meters) that were enriched in Ra by one to two orders of magnitude relative to surface waters. In particular, a permeable layer at 80 cm depth in the surrounding marsh is considered to be representative of the most likely SGD source, although similar radium activities were measured in other subtidal porewater samples collected in the Isola La Cura area. The estimated SGD flux to the study area ranged from 1 · 109 to 6 · 109 L·d− 1, the same order of magnitude as the overall riverine input to the lagoon (3 · 109 L·d− 1). A major fraction of this SGD flux is likely recirculated seawater, as evidenced by the endmember salinity. The water residence time of 2 days was estimated by both using the shortest-lived radium isotope and estimating the volume of water exchanged between the lagoon and the open sea during a tidal cycle (tidal prism approach). This SGD flux could be used to estimate the input of other chemical species (metals, nutrients, etc.) via SGD which might affect the Venice Lagoon ecosystem.  相似文献   

11.
In the framework of the KEOPS project (KErguelen: compared study of the Ocean and the Plateau in Surface water), we aimed to provide information on the water mass pathways and vertical mixing on the Kerguelen Plateau, Southern Ocean, based on 228Ra profiles. Because 228Ra activities are extremely low in this area (~ 0.1 dpm/100 kg or ~ 2.10− 18 g kg− 1), the filtration of large volumes of seawater was required in order to be able to detect it with minimal uncertainty. This challenging study was an opportunity for us to test and compare methods aimed at removing efficiently radium isotopes from seawater. We used Mn-fiber that retains radium and that allows the measurement of all four radium isotopes (226Ra, 228Ra, 223Ra, 224Ra). First, we used Niskin bottles or the ship's seawater intake to collect large volumes of seawater that were passed onto Mn-fiber in the laboratory. Second, we filled cartridges with Mn-fiber that we placed in tandem on in situ pumps. Finally, we fixed nylon nets filled with Mn-fiber on the frame of in situ pumps to allow the passive filtration of seawater during the pump deployment.Yields of radium fixation on the cartridges filled with Mn-fiber and placed on in situ pumps are ca. 30% when combining the two cartridges. Because large volumes of seawater can be filtered with these pumps, this yields to effective volumes of 177–280 kg (that is, higher than that recovered from fourteen 12-l Niskin bottles). Finally, the effective volume of seawater that passed through Mn-fiber placed in nylon nets and deployed during 4 h ranged between 125 and 364 kg. Consequently, the two techniques that separate Ra isotopes in situ are good alternatives for pre-concentrating radium from seawater. They can save ship-time by avoiding repeated CTD casts to obtain the large volumes of seawater. This is especially true when in situ pumps are deployed to collect suspended particles. However, both methods only provide 228Ra/226Ra ratios. The determination of the 228Ra specific activity is obtained by multiplying this ratio by the 226Ra activity measured in a discrete sample collected at the same water depth.  相似文献   

12.
There is increasing evidence that submarine groundwater discharge (SGD) in many areas represents a major source of dissolved chemical constituents to the coastal ocean. In Great South Bay, NY, previous studies have shown that the discharge of nutrients with SGD may cause harmful algal blooms. This study estimates SGD to Great South Bay during August 2006 by performing a mass balance for each of the dissolved Ra isotopes (224Ra, 223Ra, 228Ra, 226Ra). The budget indicates a major unknown source (between 30 and 60% of the total input) of Ra to the bay. This imbalance can be resolved by a flux of Ra-enriched groundwater on the order of 3.5–4.5 × 109 L d− 1, depending on the Ra isotope. The Ra-estimated SGD rates compare well with those previously estimated by models of flow that decreases exponentially away from shore. Compared to previous reports of fresh groundwater discharge to the bay, the Ra-estimated discharge must comprise approximately 90% recirculated seawater. The good agreement between Ra- and model-estimated flow rates indicates that the primary SGD endmember may be best sampled at shallow depths in the sediments a short distance bayward of the low tide line.  相似文献   

13.
Radium isotopes (223Ra, 224Ra, 226Ra, and 228Ra) and water chemistry were used to identify two chemically distinct sources of submarine groundwater discharge (SGD) in Celestún Lagoon, Yucatán, Mexico. Low salinity groundwater discharging from springs within the lagoon has previously been identified and extensively sampled for nutrient concentrations. However, a second type of groundwater discharging into the lagoon was detected during this study using radium isotope activity measurements. This second type of groundwater is characterized by moderate salinities (within the range of lagoon salinities) and very elevated radium activities in comparison to the low salinity groundwater, mixed lagoon water, and seawater. Further analysis showed that the two types of groundwater also have distinct chloride, strontium, and sulfate ratios, along with slightly different nutrient concentrations. Groundwater discharge occurs through large and small springs scattered throughout the lagoon, and both types of groundwater were detected discharging from one of the larger springs. The relative proportions of low salinity groundwater and brackish high radium groundwater varied over the tidal cycle. In order to better understand the relative contributions of each type of groundwater to the lagoon, a three end-member mixing model based on the distinct chemical and isotopic compositions of both types of groundwater and of seawater was used to estimate the distribution of each water type throughout the lagoon in different seasons. This study suggests that substantial groundwater discharge to the lagoon can occur during both dry and rainy seasons. The presence of two groundwater sources has implications for monitoring and protection of the Celestún Lagoon Biosphere Reserve, since the two sources may have different susceptibilities to anthropogenic contamination depending on their respective recharge area and recharge rates.  相似文献   

14.
盐度对镭同位素在海南红树林沉积物解吸行为的影响   总被引：1，自引：0，他引：1  
天然放射性镭同位素在沉积物上的解吸行为是影响其在陆-海交换过程中的关键所在。采用沉积物室内解吸实验和现场采集间隙水测量224Ra含量两种方法,对水体盐度梯度控制镭在海南八门湾红树林沉积物的解吸行为进行了讨论。结果表明:沉积物上可交换态224Ra的最大量为0.44dpm/g,解吸比为35%。利用间隙水的224Ra含量确定镭的分配比Kd与水体盐度S呈反比例函数:Kd=8.4×102/S,与室内解吸实验的结果相比更能代表镭在沉积物上的真实解吸行为。在深度25—40cm内,湿地沉积物的224Ra处于与其母体228Th的平衡状态,但223Ra很可能处于相对其母体227Th亏损状态。  相似文献   

15.
白令海峡水团来源的镭同位素示踪   总被引：4，自引：3，他引：1       下载免费PDF全文
对白令海峡64.3°N纬向断面镭同位素的研究表明,水体中226Ra比活度、228Ra比活度和228Ra/226Ra)A.R.存在明显的纬向变化,反映出太平洋与北冰洋水体交换的多种路径.根据温度、盐度和镭同位素的水平与垂直分布,太平洋水进入北冰洋的路径可能主要有3支,分别为白令海峡西侧的阿拉德水、白令海峡东侧的阿拉斯加沿...  相似文献   

16.
A mass balance for the naturally-occurring radium isotopes (224Ra, 223Ra, 228Ra, and 226Ra) in Jamaica Bay, NY, was conducted by directly estimating the individual Ra contributions of wastewater discharge, diffusion from fine-grained subtidal sediments, water percolation through marshes, desorption from resuspended particles, and water exchange at the inlet. The mass balance revealed a major unknown source term accounting for 19–71% of the total Ra input, which could only be resolved by invoking a source from submarine groundwater. Shallow (< 2 m depth) groundwater from permeable sediments in Jamaica Bay was brackish and enriched in Ra relative to surface bay waters by over two orders of magnitude. To balance Ra fluxes, a submarine groundwater input of 0.8 × 109–9.0 × 109 L d− 1 was required. This flux was similar for all four isotopes, with individual estimates varying by less than a factor of 2. Our calculated groundwater flux was 6- to 70-fold higher than the fresh groundwater discharge to the bay estimated by hydrological methods, but closely matched direct flow rates measured with seepage meters. This suggests that a substantial portion of the discharge consisted of recirculated seawater. The magnitude of submarine groundwater discharge varied seasonally, in the order: summer > autumn > spring. Chemical analyses suggest that the recirculated seawater component of submarine groundwater delivers as much dissolved nitrogen to the bay as the fresh groundwater flux.  相似文献   

17.
A total of 21 surface water samples were collected on the east side of the East China Sea (ECS) (3 sites) and at the Tsushima Strait (1 site), and 226Ra and 228Ra activities were measured using low-background γ-spectrometry. The 228Ra/226Ra ratios among the samples exhibited notable seasonal variation (228Ra/226Ra = 0.2–2.6) accompanying changes of salinity (31.7–34.7). Seasonal water circulation within the ECS is hypothesized to cause the change by altering the mixing ratio of 228Ra-rich continental shelf water and 228Ra-poor Kuroshio water.  相似文献   

18.
226Ra and 228Ra have non-conservative excess concentrations in the mixing zones of the Pee Dee River-Winyah Bay estuary, the Yangtze River estuary, and the Delaware Bay estuary. Laboratory experiments, using Pee Dee River sediment, indicate desorption of 226Ra to increase with increasing salinities up to 20‰. In Winyah Bay desorption from river-borne sediments could contribute almost all of the increases for both isotopes. Desorption adds only a portion of the excess 228Ra measured in the Yangtse River and adjacent Shelf waters and Delaware Bay. In the Yangtze River the mixing zone extends over a considerable portion of the Continental Shelf where 228Ra is added to the water column by diffusion from bottom sediments, while 226Ra concentrations decrease from dilution. Diffusion of 228Ra from bottom sediments in Delaware Bay primarily occurs in the upper part of the bay (< 22‰ water) where fine grained sediments predominate. A diffusive flux for 228Ra of 0·33 dpm cm−2 year was determined for Delaware Bay.  相似文献   

19.
We determined groundwater flow rates shortly after the wet season into an embayment near Ubatuba, Brazil as part of an international intercomparison experiment for submarine groundwater discharge (SGD) assessment techniques. Our estimated rates were determined by the combined use of continuous radon measurements and assessment of radium isotope patterns. The spatial distribution of the short-lived radium isotopes (223Ra and 224Ra) provided the means for independent evaluations of radon losses by mixing and atmospheric evasion. We were thus able to construct a well-constrained mass balance for radon that included a groundwater flux term. Our results showed that the groundwater discharge into this embayment from the fractured crystalline rock aquifer is not steady-state but varies with tidal modulation and rain-induced forcing. Tidally modulated and rain-induced flow rates were comparable during this period. The SGD rates estimated from radon ranged from 1 cm/day to 29 cm/day (cm3/cm2 day) with a mean and standard deviation of 13 ± 6 cm/day. These estimates were mostly similar to a dye-dilution automatic seepage meter (15 ± 19 cm/day) and were within the broad ranges estimated by manual and continuous heat seepage meters but lower than indicated by an artificial tracer test performed nearshore.  相似文献   

20.
Measurements of methane (CH4) so far have always shown supersaturation in the entire North Sea relative to the atmospheric partial pressure and the distribution of surface CH4 reveals a distinct increase towards the shore. Since North Sea sediments presumably are an insignificant source for CH4 the coastal contribution via rivers and tidal flats gains in importance.In this work, CH4 data from the River Weser, the back barrier tidal flats of Spiekeroog Island (NW Germany), and the German Bight are presented. Results from the River Weser are compared to other rivers draining into the German Bight. Measurements in the tidal flat area of Spiekeroog Island highlight this ecosystem as an additional contributor to the overall CH4 budget of the southern North Sea. A tidally driven CH4 pattern is observed for the water column with maximum values during low tide. Tidal flat sediments turn out to be the dominating source because pore waters discharged during low tide are highly enriched in CH4. In contrast, the freshwater contribution to the tidal flats by small coastal tributaries has almost no impact on water column CH4 concentrations. The CH4 level seems to be disturbed irregularly by wind forcing due to elevated degassing and prevention of advective flow when tidal flats remain covered by water.Based on our data, two model calculations were used to estimate the impact of tidal flats on the CH4 budget in the German Bight. Our results demonstrate that the back barrier tidal flats of the east Frisian Wadden Sea contribute CH4 in an order of magnitude between the Wash estuary and River Elbe and thus have to be considered in budget calculations.  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