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1.
Submarine groundwater discharge is an important net source of light and middle REEs to coastal waters of the Indian River Lagoon, Florida, USA 总被引：2，自引：0，他引：2
Karen H. Johannesson Darren A. Chevis Jaye E. Cable Moutusi Roy 《Geochimica et cosmochimica acta》2011,75(3):825-843
Porewater (i.e., groundwater) samples were collected from multi-level piezometers across the freshwater-saltwater seepage face within the Indian River Lagoon subterranean estuary along Florida’s (USA) Atlantic coast for analysis of the rare earth elements (REE). Surface water samples for REE analysis were also collected from the water column of the Indian River Lagoon as well as two local rivers (Eau Gallie River, Crane Creek) that flow into the lagoon within the study area. Concentrations of REEs in porewaters from the subterranean estuary are 10-100 times higher than typical seawater values (e.g., Nd ranges from 217 to 2409 pmol kg−1), with submarine groundwater discharge (SGD) at the freshwater-saltwater seepage face exhibiting the highest REE concentrations. The elevated REE concentrations for SGD at the seepage face are too high to be the result of simple, binary mixing between a seawater end-member and local terrestrial SGD. Instead, the high REE concentrations indicate that geochemical reactions occurring within the subterranean estuary contribute substantially to the REE cycle. A simple mass balance model is used to investigate the cycling of REEs in the Indian River Lagoon and its underlying subterranean estuary. Mass balance modeling reveals that the Indian River Lagoon is approximately at steady-state with respect to the REE fluxes into and out of the lagoon. However, the subterranean estuary is not at steady-state with respect to the REE fluxes. Specifically, the model suggests that the SGD Nd flux, for example, exported from the subterranean estuary to the overlying lagoon waters exceeds the combined input to the subterranean estuary from terrestrial SGD and recirculating marine SGD by, on average, ∼100 mmol day−1. The mass balance model also reveals that the subterranean estuary is a net source of light REEs (LREE) and middle REEs (MREE) to the overlying lagoon waters, but acts as a sink for the heavy REEs (HREE). Geochemical modeling and statistical analysis further suggests that this fractionation occurs, in part, due to the coupling between REE cycling and iron redox cycling within the Indian River Lagoon subterranean estuary. The net SGD flux of Nd to the Indian River Lagoon is ∼7-fold larger than the local effective river flux to these coastal waters. This previously unrecognized source of Nd to the coastal ocean could conceivably be important to the global oceanic Nd budget, and help to resolve the oceanic “Nd paradox” by accounting for a substantial fraction of the hypothesized missing Nd flux to the ocean. 相似文献
2.
Edward J. Phlips Susan Badylak Jane Hart Daniel Haunert Jean Lockwood Kathyrn O’Donnell Detong Sun Paula Viveros Mete Yilmaz 《Estuaries and Coasts》2012,35(1):335-352
The St. Lucie Estuary, located on the southeast coast of Florida, provides an example of a subtropical ecosystem where seasonal
changes in temperature are modest, but summer storms alter rainfall regimes and external inputs to the estuary from the watershed
and Atlantic Ocean. The focus of this study was the response of the phytoplankton community to spatial and temporal shifts
in salinity, nutrient concentration, watershed discharges, and water residence times, within the context of temporal patterns
in rainfall. From a temporal perspective, both drought and flood conditions negatively impacted phytoplankton biomass potential.
Prolonged drought periods were associated with reduced nutrient loads and phytoplankton inputs from the watershed and increased
influence of water exchange with the Atlantic Ocean, all of which restrict biomass potential. Conversely, under flood conditions,
nutrient loads were elevated, but high freshwater flushing rates in the estuary diminished water residence times and increase
salinity variation, thereby restricting the buildup of phytoplankton biomass. An exception to the latter pattern was a large
incursion of a cyanobacteria bloom from Lake Okeechobee via the St. Lucie Canal observed in the summer of 2005. From a spatial
perspective, regional differences in water residence times, sources of watershed inputs, and the proximity to the Atlantic
Ocean influenced the composition and biomass of the phytoplankton community. Long water residence times in the North Fork
region of the St. Lucie Estuary provided an environment conducive to the development of blooms of autochthonous origin. Conversely,
shorter residence times in the mid-estuary limit autochthonous increases in biomass, but allochthonous sources of biomass
can result in bloom concentrations of phytoplankton. 相似文献
3.
圆盘固相萃取富集-气相色谱法测定地表水中有机氯和有机磷农药 总被引：4，自引：2，他引：2
采用环境友好的圆盘固相萃取新技术富集水体中有机氯农药和有机磷农药,分别用微池电子捕获检测器(μECD)和火焰光度检测器(FPD)气相色谱法检测,实现了水中有机氯和有机磷农药残留物的测定。结果表明,16种有机氯农药的平均回收率为64.7%~102%,精密度(RSD,n=6)为2.9%~15%;13种有机磷农药的平均回收率为65.9%~104%,精密度(RSD,n=6)为1.7%~17%。方法快速、灵敏、低污染,可用于水体中多种有机氯农药和有机磷农药的残留分析。 相似文献
4.
St. Lucia Estuary is on the subtropical, predominantly microtidal Zululand coast of South Africa. Lake St. Lucia's surface area fluctuates between 420 and 215 km2 and has a mean depth of less than 1 m. The 21-km-long narrows connects Lake St. Lucia with the Indian Ocean. Tidal effects penetrate 14 km up the narrows. The St. Lucia system has changed substantially since the 1930s due to bad farming techniques within its catchment. Large amounts of sediment were deposited in the estuary mouth, resulting in relocation of the Mfolozi River mouth to the south at Mapelane. The St. Lucia catchment was subjected to two devastating floods in the last ten years: Cyclone Domoina during February 1984 and the September 1987 cutoff low flood. After floods scoured out the estuary, marine sand advanced up the estuary at a rate of 1200 m/y as a series of flood-tidal deltas. Over 600,000 m3 of sediment accumulated in the St. Lucia Estuary mouth from February 1988 to November 1989. Of this amount, 466,000 m3 of sediment was removed by dredging, although this has not stopped the shoaling. During high rainfall years, the estuary mouth is able to maintain an open outlet to the sea, but as lake levels drop, shoaling causes the mouth to constrict and eventually close. Without the dredging program the mouth would ultimately close during low rainfall years, causing management problems. 相似文献
5.
The need of surface soil removal during reclamation of the former underground landfills makes environmental monitoring difficult to perform. Environmental quality assessment after reclamation is very important because it provides information about: (1) the efficiency of remediation, (2) the rate of biodegradation of contaminants which were not removed during reclamation works and (3) the possible migration of contaminants from soil and permeable host rocks to surface waters and groundwaters. The concept of geoindicators, which was introduced to facilitate the assessment of environmental changes, can help assess environmental quality at sites previously subjected to reclamation. The groundwater quality is usually used as a geoindicator of inorganic contaminants. This concept was applied to find changes in organochlorine pesticide concentrations in groundwaters after toxic pesticide burial ground reclamation. The aim of this study was to monitor the concentrations of organochlorine pesticides and their metabolites in groundwaters at the former pesticide landfill site after its remediation. The study showed that very high concentrations of organochlorine pesticides and their metabolites in a contaminated soil had a small influence on pesticide concentrations in groundwaters and that this influence decreased in time. It has been 2 years since reclamation of the landfill took place, and the concentrations of organochlorine pesticides in groundwaters dropped to acceptable levels within the current environmental quality standards. 相似文献
6.
我国南海海鱼中有机氯农药残留分析 总被引：3，自引：0，他引：3
建立了凝胶渗透色谱前处理,毛细管气相色谱测定我国南海海鱼中11种有机氯农药的方法。分析了油鲽鱼块、鲷鱼片、银鳕鱼、哈哈鱼块、海鳗鱼中的有机氯农药残留情况,发现在禁用20多年后,六六六(HCHs)、滴滴涕(DDTs)、狄氏剂、环氧七氯在鱼肉中均有不同程度的检出,其中滴滴涕的残留水平最高达到26.73μg/kg。研究发现我国南海海鱼中4种HCH的总残留量高于北京市场上的淡水鱼的残留水平;多数有机氯农药残留污染的平均水平也高于英国和巴西等国鱼类的水平。南海海鱼中有机氯农药残留水平具有指示环境污染的意义。 相似文献
7.
The transport and leaching potential hazards of various pesticides were studied in a shallow unconfined aquifer located in Northwest Bangladesh. Pesticide leaching potential was quantified using a one-dimensional advective–dispersive transport equation for a non-conservative chemical that follows first-order decay and linear adsorption in soils. Leaching potential index (LPI) was calculated for 69 sites in the study area to evaluate the relative vulnerability to pesticide leaching and to prioritize sites for model study and soil sampling. The numerical ranks of computed LPI were grouped by quantiles into very high, high, moderate, low and very low categories; and based on these rankings, the most vulnerable site was selected. The fate and transport of pesticides in this most vulnerable site was modeled using MT3D. The model results indicate that pesticides with high sorptivity and moderate to high persistence have low potential impact on groundwater. Top soils are found to be particularly vulnerable to the accumulation of organochlorine pesticides. Results also revealed that decreasing the soil organic matter and increasing the half-life of the pesticides at deeper depths did not make any significant change. Finally, six soil samples were collected from the same site at depths of 0.0, 1.5, 3.0, 4.5, 6.0, and 7.5 m for the analysis of pesticide residues. The soil–water was extracted from the samples following standard extraction technique and tested using gas chromatography (GC) and high-performance liquid chromatography (HPLC) for pesticide residues. Results showed no trace of pesticide residues in the soil–water; however, a few unknown peaks were detected indicating the use of some unknown brand of chemicals in the study area. 相似文献
8.
9.
R. Paperno D. M. Tremain D. H. Adams A. P. Sebastian J. T. Sauer J. Dutka-Gianelli 《Estuaries and Coasts》2006,29(6):1004-1010
During the summer of 2004, four hurricanes (Charley, Frances, Ivan, and Jeanne) affected Florida between August 13 and September
27. Two storms (Frances: category 2 and Jeanne: category 3) made landfall in the southern portion of the Indian River Lagoon
(IRL) on the east-central coast of Florida. The presence of Florida Fish and Wildlife Conservation Commission's long-term
fisheries monitoring program in the IRL provided a unique opportunity to examine the effects of large tropical events on estuarine
fish communities. Increased sampling efforts to monitor the effects of tropical disturbances on the fish community within
the IRL and one of its major tributaries (St. Sebastian River) were initiated within days after the passing of the last hurricane
(Jeanne). The objectives of the study were to characterize changes to the composition of the fish community within the lagoon
and river immediately after the passage of two hurricanes, and to examine the recovery of the fish communities. Analyses indicated
that immediately after the last hurricane passed, community diversity within the estuary decreased following these storms
due to the absence of many marine species, whereas the fish community within the St. Sebastian River shifted to one containing
a greater percentage of freshwater species. Recovery of the community structure to pre-hurricane conditions was evident within
several weeks following the last hurricane, and by mid December 2004 (ca. 3 mo after the last storm), there was little difference
between the pre-hurricane and post-hurricane fish communities. 相似文献
10.
Estuaries receive large quantities of suspended sediments following the first major storm of the water year. The first-flush events transport the majority of suspended sediments in any given year, and because of their relative freshness in the hydrologic system, these sediments may carry a significant amount of the sediment-associated pesticide load transported into estuaries. To characterize sediment-associated pesticides during a first-flush event, water and suspended sediment samples were collected at the head of the San Francisco Bay during the peak in suspended sediment concentration that followed the first major storm of the 1996 hydrologic year. Samples were analyzed for a variety of parameters as well as 19 pesticides and degradation products that span a wide range of hydrophobicity. Tidal mixing at the head of the estuary mixed relatively fresh suspended sediment transported down the rivers with suspended sediments in estuary waters. Segregation of the samples into groups with similar degrees of mixing between river and estuary water revealed that transport of suspended sediments from the Sacramento-San Joaquin drainage basin strongly influenced the concentration and distribution of sediment-associated pesticides entering the San Francisco Bay. The less-mixed suspended sediment contained a different distribution of pesticides than the sediments exposed to greater mixing. Temporal trends were evident in pesticide content after samples were segregated according to mixing history. These results indicate sampling strategies that collect at a low frequency or do not compare samples with similar mixing histories will not elucidate basin processes. Despite the considerable influence of mixing, a large number of pesticides were found associated with the suspended sediments. Few pesticides were found in the concurrent water samples and in concentrations much lower than predicted from equilibrium partitioning between the aqueous and sedimentary phases. The observed sediment-associated pesticide concentrations may reflect disequilibria between sedimentary and aqueous phases resulting from long equilibration times at locations where pesticides were applied, and relatively short transit times over which re-equilibration may occur. 相似文献
11.
Erwin E. Klaas Stanley N. Wiemeyer Harry M. Ohlendorf Douglas M. Swineford 《Estuaries and Coasts》1978,1(1):46-53
Eggs of barn owls (Tyto alba) were collected from 18 nests in offshore duck blinds on the Maryland side of the lower Potomac River estuary in 1972 and 1973 and analyzed for organochlorine residues. DDE was found in 100% of the clutches, PCBs in 89%, and dieldrin in 78%. Eggshell thickness was inversely correlated with concentrations of DDE, DDD, and dieldrin residues. Six of the 18 clutches had mean DDE residues above 5 ppm, and eggshell thickness in these six clutches was significantly less (P<0.001) than in the other 12 clutches. The owls produced 1.7 young per active nest in 1973. This rate is slightly below the reproductive rate needed to maintain a stable population. An estimated 15% of the population carried concentrations of organochlorine residues that may have been detrimental to their reproduction. Passerine birds, taken extensively as food by a small proportion of the population, are believed to have been the source of elevated concentrations of organochlorines in these barn owls. 相似文献
12.
The Manzala Lagoon in Egypt's Nile Delta has become a sediment sink of reduced area and depth, with increased contaminant
levels. Loss of much-needed fresh to brackish water reserves and decreased fish catches have serious ramifications. Herein,
maps of temporal and regional sediment distributions in Manzala incorporate petrological and statistical analyses of 200 surficial
and short core samples. These provide baseline information needed to help implement protection measures for this vital wetland.
Four periods are considered: 1920s, 1940s, ∼1965, and 1990. Important depositional changes between 1940s and ∼1965 resulted
from anthropogenic effects on this quasi-closed lagoon system, including industrial buildup, wetland conversion to agricultural
land, and irrigation waterway development. Further modification from ∼1965 to 1990 is associated with closure of the Aswan
High Dam, continued construction of waterways that discharge waste water into lagoon margins, and marine incursion into the
northern lagoon. If current practices continue, the lagoon could be reduced to about one-third of its present area by 2050
AD.
Received: 2 October 1997 · Accepted: 13 January 1998 相似文献
13.
A study was carried out in fall 1987 to determine if red drum (Sciaenops ocellatus) spawned in the southern portion of Mosquito Lagoon, Florida, 30 km from the nearest tidal pass. Weekly plankton tows were taken from mid-September to mid-November. Floating sciaenid eggs were removed from the samples and incubated 16–36 h: 329 red drun eggs were hatched. Viable red drum eggs were collected from October 27 to November 18 at salinities of 29‰ to 32‰ and water temperatures of 21°C to 23°C. The largest number of eggs was collected on November 4, during a full moon. This is the first documentation of red drum spawning in an estuary. The physiography and high salinity (which are more characteristic of marine than estuarine waters) of Mosquito Lagoon were probable factors in producing this phenomenon. 相似文献
14.
Much work in recent years has reported on the role of submarine groundwater discharge (SGD) on coastal biogeochemistry, but most of those studies have focused on temperate or tropical climates where year-round rainfall recharges surficial aquifers. The aim of this work, however, was to examine SGD behaviors in an arid setting??Marina Lagoon on the Egyptian Mediterranean coast. SGD was estimated via radon surveys and time-series measurements in lagoon waters during two campaigns (wet season in March 2009 and dry season in July 2010). Relatively higher values of radon were detected in March (maximum >30?dpm/L) compared to July (up to 16?dpm/L), which would indicate either enhanced input rates, or lower mixing/atmospheric losses during the wet season. Lower salinity waters within Marina Lagoon were characterized by higher radon and higher concentrations of dissolved inorganic nitrogen (DIN) and silica (DISi), characteristic of groundwater inputs. Based on lagoon and groundwater radon measurements and an advection-diffusion model, SGD average rates between 0.83 to 2.4?×?108?L/day were estimated for both surveys. Since no seasonal pattern was detected, we suspect that either (1) SGD is derived from a regional aquifer not influenced by recharge from local rainfall or (2) local water use for irrigation and domestic purposes artificially recharges the surficial aquifer in the dry summer (tourist) months, which compensates for the lack of rainfall occurring at that time. 相似文献
15.
广西百朗地下河水和沉积物中有机氯农药的分布特征 总被引：4，自引：2，他引：2
为了解典型岩溶地区广西乐业百朗地下河表层水和沉积物中有机氯农药的分布特征,采集地下河不同断面的水和沉积物样品,利用气相色谱仪测定了19种有机氯农药。结果表明:(1)百朗地下河表层水中19种有机氯农药总量(∑OCPs)浓度为1.95～71.45ng/L,HCHs和DDTs浓度分别为未检出至58.40ng/L和未检出至0.44ng/L;(2)沉积物中∑OCPs浓度为0.75～14.85ng/g,HCHs和DDTs浓度分别为0.11～3.52ng/g和0.03～2.90ng/g;(3)地下河表层水和沉积物中有机氯农药的分布与吸附作用、环境温度以及和地下河连通的天坑的底部的土壤侵蚀有关,即因温差作用,大气沉降的有机氯农药易富集在天坑底部(“冷陷阱效应”),并在土壤侵蚀作用下向水体移动,使地下河沉积物中有机氯农药浓度升高;(4)百朗地下河出口沉积物吸附系数最低,但水中有机氯农药浓度较高且种类最多,推测可能是地下河沉积物中因有机氯农药被释放而引起二次污染;(5)表层沉积物中大多数断面的异狄氏剂浓度及乐业县城附近断面的DDTs和DDD浓度在风险评估低值与风险评估中值之间,表明百朗地下河处于较低的生态风险水平;(6)目前,流域部分断面尚有新的γ-HCH(林丹)和DDTs农药输入。由于有机氯农药长期累积,可能对地下河生态系统造成危害,应采取防治措施。 相似文献
16.
Khalid F. Al-Mutlaq 《Environmental Geology》2006,51(4):493-497
Organic contents of agricultural soils are major sources of organic compounds and pesticides into atmosphere. Therefore, surface soil samples from different locations in the city of Corvallis, USA were collected over a course of 1 year (2004/2005). The samples were subject to chemical extraction and analysis by gas chromatography–mass spectrometry (GC–MS). The results of the chemical analysis showed pesticide residues were present in soils and varied seasonally. For example, the highest total relative concentration of pesticide residues in Canola field was 0.16% in January 2005, and was 0.56% in Wheat Field in August 2005, and was 0.14% in the River Front Park in December 2004 and was 0.33 in Rose Garden. Sometimes in the year, these pesticide residues were not detected in the same sites. 相似文献
17.
18.
A case study is presented to assess the use of sedimentary chemical indicators for estuarine health. Reliable and efficient estuarine indicators are essential for management and monitoring purposes. Estuarine and fluvial sediments from Brisbane Water estuary were analysed for heavy metals to assess the quality of sediments and to determine the source and dispersion of contaminants in the estuary. Brisbane Water, 50 km north of Sydney, is a shallow (～5 m in main water body), wave-dominated barrier estuary with a generally sparsely developed catchment, except in the north where it is urbanised and industrialised. Heavy-metal loadings calculated for sub-catchments and the distribution of metals in surficial sediment identified Narara Creek, which drains the urbanised northern part of the catchment, as the main source of contaminants. Vertical profiles of sedimentary contaminants show that contamination continues to increase rapidly in all parts of the waterway to the present day. Concentrations of Cu, Pb and Zn in sediment adjacent to Narara Creek exceeded lower guideline levels, although moderate bioavailability (～40% for Cu, Pb and Zn) suggests the risk posed by sediments to benthic populations is low. Sediments in all parts of Brisbane Water show evidence of minor anthropogenic influence with maximum human-induced change (up to 5× enrichment) in the north of the estuary. Results demonstrate the use of sediment-bound heavy metal as an appropriate indicator of estuarine health. 相似文献
19.
Groundwater-dependent ecology of the shoreline of the subtropical Lake St Lucia estuary 总被引：1，自引：0，他引：1
Ricky Taylor Bruce Kelbe Sylvi Haldorsen Greg A. Botha Bente Wejden Lars Været Marianne B. Simonsen 《Environmental Geology》2006,49(4):586-600
The ecology of the St Lucia estuary in South Africa is of unique international importance. During droughts the estuary experiences
high salinities, with values above that of seawater. Ion-poor groundwater flowing into the estuary from prominent sand aquifers
along its eastern shoreline forms low-salinity habitats for salt-sensitive biota. During droughts, plants and animals can
take refuge in the groundwater discharge zone until the condition in the estuary regains tolerable salinity. Simulations of
the groundwater discharge indicate that the flow can persist during droughts over at least a decade, and be of great important
for the resilience of the estuary. Anthropogenic activities have reduced the river inflow and made the St Lucia estuary more
sensitive to droughts. The groundwater has thereby become increasingly important for the estuary’s ecology. Protection of
the groundwater discharge along the shoreline itself and actions to increase the groundwater recharge are therefore important
management tasks. 相似文献
20.
Edward J. Phlips Susan Badylak Mary C. Christman Margaret A. Lasi 《Estuaries and Coasts》2010,33(2):498-512
This paper describes the results of 10 years of water quality monitoring in the Indian River Lagoon Florida, with special
emphasis on the relationships between trends in climatic conditions and the distribution, composition, and abundance of the
phytoplankton community. The Indian River Lagoon, which spans 220 km of Florida’s east coast, is a region of particular concern
because of the rapid rate of human development throughout the region and the hydrologically restricted character of the lagoon,
which heightens the potential for algal bloom. Water sampling was carried out on a monthly to twice-monthly basis at six sites
located in the northern and central lagoon. The 10-year study included both extended periods of below and above average rainfall.
A number of ecologically distinct regions exist within the lagoon, which differ considerably in water exchange properties
and watershed inputs. The northern lagoon is characterized by longer water residence times, lower phosphorus concentrations,
higher nitrogen concentrations, and more stable salinity conditions than the central lagoon. Mean phytoplankton biovolumes
were substantially higher at the sites in the northern lagoon than at the sites in the central lagoon, and algal blooms were
more common and intense in the former region. Inter-annual patterns of phytoplankton biovolume were also different in the
northern and central lagoon. In the northern lagoon, phytoplankton biovolumes were lowest during the drought period, from
the autumn of 1998 to the spring of 2001. By contrast, algal bloom events in the central lagoon were not only less frequent
but were not tied to periods of high rainfall. The most widespread and common bloom formers were the potentially toxic dinoflagellate
Pyrodinium bahamense var. bahamense and two centric diatoms, Dactyliosolen fragilissimus and Cerataulina pelagica. Many of the biovolume peaks observed over the study period were attributable to these three species. The results of time
series modeling of phytoplankton dynamics further highlighted the disparities between the two regions of the lagoon in terms
of the suite of parameters that best predict the observed trends in the biomass of phytoplankton. Overall, the outcome of
this initial modeling effort in the Indian River Lagoon suggests that time series approaches can help define the factors that
influence phytoplankton dynamics. 相似文献