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1.
Salton Sea, California, like many other lakes, has become eutrophic because of excessive nutrient loading, primarily phosphorus
(P). A Total Maximum Daily Load (TMDL) is being prepared for P to reduce the input of P to the Sea. In order to better understand
how P-load reductions should affect the average annual water quality of this terminal saline lake, three different eutrophication
programs (BATHTUB, WiLMS, and the Seepage Lake Model) were applied. After verifying that specific empirical models within
these programs were applicable to this saline lake, each model was calibrated using water-quality and nutrient-loading data
for 1999 and then used to simulate the effects of specific P-load reductions. Model simulations indicate that a 50% decrease
in external P loading would decrease near-surface total phosphorus concentrations (TP) by 25–50%. Application of other empirical
models demonstrated that this decrease in loading should decrease near-surface chlorophyll a concentrations (Chl a) by 17–63% and increase Secchi depths (SD) by 38–97%. The wide range in estimated responses in Chl a and SD were primarily caused by uncertainty in how non-algal turbidity would respond to P-load reductions. If only the models
most applicable to the Salton Sea are considered, a 70–90% P-load reduction is required for the Sea to be classified as moderately
eutrophic (trophic state index of 55). These models simulate steady-state conditions in the Sea; therefore, it is difficult
to ascertain how long it would take for the simulated changes to occur after load reductions.
Guest editor: S. H. Hurlbert
The Salton Sea Centennial Symposium. Proceedings of a Symposium Celebrating a Century of Symbiosis Among Agriculture, Wildlife
and People, 1905–2005, held in San Diego, California, USA, March 2005. 相似文献
2.
The Salton Sea is the largest lake, on a surface area basis, in California (939 km2). Although saline (>44 g/l) and shallow (mean depth approximately 9.7 m), it provides valuable habitat for a number of endangered
species. The distribution of sediments and their properties within the Salton Sea are thought to have significant influence
on benthic ecology and water quality. Sediment properties and their distribution were quantified and compared with predicted
distributions using several sediment distribution models. Sediment samples (n = 90) were collected using a regular staggered-start sampling grid and analyzed for water content, organic carbon (C), calcium
carbonate, total nitrogen (N), total phosphorus (P), organic phosphorus, and other properties. Water content, total N, and
total and organic P concentrations were all highly correlated with organic C content. The organic C concentration showed a
non-linear increase with depth, with low organic C contents (typically 1–2%) present in sediments found in depths up to 9 m,
followed by a strong increase in organic C at greater depths (to about 12% at 15 m depth). The models of Hakanson, Rowan et al.,
Blais and Kalff, and Carper and Bachmann yielded very different predicted critical depths for accumulation (10.5–22.8 m) and
areas of accumulation (0–49.5%). Hakanson’s dynamic ratio model more reasonably reproduced the observed zone of elevated organic
C concentrations in the Salton Sea than either exposure- or slope-based equations. Wave theory calculations suggest that strong
winds occurring less than 1% of the time are sufficient to minimize accumulation of organic matter in sediments that lie at
depths less than 9 m in this system.
Guest editor: S. H. Hurlbert
The Salton Sea Centennial Symposium. Proceedings of a Symposium Celebrating a Century of Symbiosis Among Agriculture, Wildlife
and People, 1905–2005, held in San Diego, California, USA, March 2005 相似文献
3.
The Salton Sea (Sea) is a eutrophic to hypereutrophic lake characterized by high nutrient concentrations, low water clarity,
and high biological productivity. Based on dissolved phosphorus (P) and nitrogen (N) concentrations and N:P ratios, P is typically
the limiting nutrient in the Sea and, therefore, should be the primary nutrient of concern when considering management efforts.
Flows in the major tributaries to the Sea have been measured since 1965, whereas total P (TP) concentrations were only measured
intermittently by various agencies since 1968. These data were used to estimate annual P loading from 1965 to 2002. Annual
loads have increased steadily from ∼940,000 kg around 1968 to ∼1,450,000 kg in 2002 (∼55% increase), primarily a result of
increased TP concentrations and loads in the New River. Although the eutrophic condition of the Salton Sea is of great concern,
only limited nutrient data are available for the Sea. It is difficult to determine whether the eutrophic state of the Sea
has degraded or possibly even improved slightly in response to the change in P loading because of variability in the data
and changes in the sampling and analytical methodologies.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
Guest editor: S. H. Hurlbert
The Salton Sea Centennial Symposium. Proceedings of a Symposium Celebrating a Century of Symbiosis Among Agriculture, Wildlife
and People, 1905–2005, held in San Diego, California, USA, March 2005 相似文献
4.
The Salton Sea is one of the few saline, inland lakes in the world with a population of barnacles, Balanus amphitrite. It is also one of California’s most impaired water bodies due to excessive nutrient loading which leads to phytoplankton
blooms and low dissolved oxygen. Currently, B. amphitrite growth is limited due to lack of hard substrate in and around the Sea. We have hypothesized that artificial substrate could
support the growth of B. amphitrite and their filter-feeding would lead to improved water quality. Periodic harvesting of the barnacles would result in the permanent
removal of nitrogen and phosphorus from the Sea. A 44-day in-situ experiment was carried out in the Salton Sea to assess the
rate of barnacle growth and phosphorus and nitrogen sequestration on burlap sheets suspended vertically from a floating line.
Burlap panels were collected weekly and the barnacles analyzed for Ca, total-P, inorganic-P, total-N, total-C, CaCO3, and organic matter content. After 44 days of growth, the barnacle mats weighed 7.4 kg m−2 on a dry weight basis, with 80% of the mass as shell material. The nutrient sequestration was 9.4 g P m−2 and 100 g N m−2. Approximately half of the P was inorganic and appears to be coprecipitated with the calcium carbonate shell material. Results
indicate that harvesting barnacles grown on artificial substrate in the Salton Sea would not be an effective method for removing
N or P from the lake because of the relative proportions of shell material and organic material.
Guest editor: S. H. Hurlbert
The Salton Sea Centennial Symposium. Proceedings of a Symposium Celebrating a Century of Symbiosis Among Agriculture, Wildlife
and People, 1905–2005, held in San Diego, California, USA, March 2005 相似文献
5.
Geochemistry of iron in the Salton Sea,California 总被引:1,自引:0,他引:1
The Salton Sea is a large, saline, closed-basin lake in southern California. The Sea receives agricultural runoff and, to
a lesser extent, municipal wastewater that is high in nutrients, salt, and suspended solids. High sulfate concentrations (4×
higher than that of the ocean), coupled with warm temperatures and low-redox potentials present during much of the year, result
in extensive sulfate reduction and hydrogen sulfide production. Hydrogen sulfide formation may have a dramatic effect on the
iron (Fe) geochemistry in the Sea. We hypothesized that the Fe(II)-sulfide minerals should dominate the iron mineralogy of
the sediments, and plans to increase hypolimnetic aeration would increase the amount of Fe(III)-oxides, which are strong adsorbers
of phosphate. Sequential chemical extractions were used to differentiate iron mineralogy in the lake sediments and suspended
solids from the tributary rivers. Iron in the river-borne suspended solids was mainly associated with structural iron within
silicate clays (70%) and ferric oxides (30%). The iron in the bottom sediments of the lake was associated with silicate minerals
(71% of the total iron in the sediments), framboidal pyrite (10%), greigite (11%), and amorphous FeS (5%). The ferric oxide
fraction was <4% of the total iron in these anaerobic sediments. The morphological characteristics of the framboidal pyrite
as determined using SEM suggest that it formed within the water column and experiences some changes in local redox conditions,
probably associated with alternating summer anoxia and the well-mixed and generally well-aerated conditions found during the
winter. The prevalence of Fe(II)-sulfide minerals in the sediments and the lack of Fe(III)-oxide minerals suggest that the
classic model of P-retention by Fe(III)-oxides would not be operating in this lake, at least during anoxic summer conditions.
Aeration of the hypolimnion could affect the internal loading of P by changing the relative amounts of Fe(II)-sulfides and
Fe(III)-oxides at the sediment/water interface.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
Guest editor: S. H. Hurlbert
The Salton Sea Centennial Symposium. Proceedings of a Symposium Celebrating a Century of Symbiosis Among Agriculture, Wildlife
and People, 1905–2005, held in San Diego, California, USA, March 2005 相似文献
6.
The Salton Sea is a hypersaline lake located in southeastern California. Concerns over the ecological impacts of sediment
quality and potential human exposure to dust emissions from exposed lakebed sediments resulting from anticipated shrinking
of shoreline led to a study of pesticide distribution and transport within the Salton Sea Basin, California, in 2001–2002.
Three sampling stations—upriver, river mouth, and offshore—were established along each of the three major rivers that discharge
into the Salton Sea. Large-volume water samples were collected for analysis of pesticides in water and suspended sediments
at the nine sampling stations. Samples of the bottom sediment were also collected at each site for pesticide analysis. Sampling
occurred in October 2001, March–April 2002, and October 2002, coinciding with the regional fall and spring peaks in pesticide
use in the heavily agricultural watershed. Fourteen current-use pesticides were detected in water and the majority of dissolved
concentrations ranged from the limits of detection to 151 ng/l. Diazinon, EPTC and malathion were detected at much higher
concentrations (940–3,830 ng/l) at the New and Alamo River upriver and near-shore stations. Concentrations of carbaryl, dacthal,
diazinon, and EPTC were higher in the two fall sampling periods, whereas concentrations of atrazine, carbofuran, and trifluralin
were higher during the spring, which matched seasonal use patterns of these pesticides. Current-use pesticides were also detected
on suspended and bed sediments in concentrations ranging from detection limits to 106 ng/g. Chlorpyrifos, dacthal, EPTC, trifluralin,
and DDE were the most frequently detected pesticides on sediments from all three rivers. The number of detections and concentrations
of suspended sediment-associated pesticides were often similar for the river upriver and near-shore sites, consistent with
downstream transport of pesticides via suspended sediment. While detectable suspended sediment pesticide concentrations were
more sporadic than detected aqueous concentrations, seasonal trends were similar to those for dissolved concentrations. Generally,
the pesticides detected on suspended sediments were the same as those on the bed sediments, and concentrations were similar,
especially at the Alamo River upriver site. With a few exceptions, pesticides were not detected in suspended or bed sediments
from the off-shore sites. The partitioning of pesticides between water and sediment was not predictable from solely the physical–chemical
properties of individual pesticide compounds, but appear to be a complicated function of the quantity of pesticide applied
in the watershed, residence time of sediments in the water, and compound solubility and hydrophobicity. Sediment concentrations
of most pesticides were found to be 100–1,000 times lower than the low-effects levels determined in human health risk assessment
studies. However, maximum concentrations of chlorpyrifos on suspended sediments were approximately half the low-effects level,
suggesting the need for further sediment characterization of lake sediments proximate to riverine inputs.
Guest editor: S. H. Hurlbert
The Salton Sea Centennial Symposium. Proceedings of a Symposium Celebrating a Century of Symbiosis Among Agriculture, Wildlife
and People, 1905–2005, held in San Diego, California, USA, March 2005 相似文献
7.
Kurt A. Schwabe Peter W. Schuhmann Kenneth A. Baerenklau Nermin Nergis 《Hydrobiologia》2008,604(1):181-195
This article, both theoretical and methodological in nature, argues the potential merits of using a net benefits’ framework
as a tool to aid policy makers in their efforts to compare Salton Sea restoration alternatives and inform the public as to
the potential magnitude and distribution of trade-offs associated with each alternative. A net benefits’ approach can provide
a more accurate comparison and evaluation of the potential net returns from public spending on Salton Sea restoration than
what would be provided under the suggested criteria of current legislative mandates. Furthermore, a net benefits’ framework
provides a more lucid and systematic accounting framework by which to enumerate the full array of benefits and costs of each
alternative for policy analysis. Finally, net benefits’ analysis serves to add transparency to the decision-making process
so that the public gains an understanding of how its scarce resources, including both financial and natural capital, are being
appropriated. Additionally, we illustrate and emphasize the importance of estimating the non-market values associated with
many of the ecosystem services provided by the Salton Sea and describe the major techniques that do so.
Guest editor: S. H. Hurlbert
The Salton Sea Centennial Symposium. Proceedings of a Symposium Celebrating a Century of Symbiosis Among Agriculture, Wildlife
and People, 1905–2005, held in San Diego, California, USA, March 2005 相似文献
8.
Ammonium perchlorate, a component of rocket fuel, entered Lake Mead through drainage and shallow groundwater in the Las Vegas
Valley, Nevada, and is now found in the lower Colorado River from Lake Mead to the international boundary with Mexico. Perchlorate
is a threat to human health through reduction of thyroid hormone production. Perchlorate has been found in water throughout
the lower Colorado system and in crops in the California’s Imperial Valley, as well as in several other states, but it has
not previously been included in investigations of the Salton Sea. Because perchlorate behaves conservatively in the Colorado
River, it was postulated that it could be accumulating at high levels along with other salts in the Salton Sea. Results show
that perchlorate is not accumulating in the Sea, although it is present in tributaries to the Sea at levels similar to those
found in the Colorado River. Bacterial reduction of perchlorate is the most likely explanation for the observed results.
The U.S. Government’s right to retain a non-exclusive, royalty-free license in and to any copyright is acknowledged.
Guest editor: S. H. Hurlbert
The Salton Sea Centennial Symposium. Proceedings of a Symposium Celebrating a Century of Symbiosis Among Agriculture, Wildlife
and People, 1905–2005, held in San Diego, California, USA, March 2005 相似文献
9.
Brandon K. Swan James M. Watts Kristen M. Reifel Stuart H. Hurlbert 《Hydrobiologia》2007,576(1):111-125
The Salton Sea currently suffers from several well-documented water quality problems associated with high nutrient loading.
However, the importance of phosphorus regeneration from sediments has not been established. Sediment phosphorus regeneration
rates may be affected by benthic macroinvertebrate activity (e.g. bioturbation and excretion). The polychaete Neanthes
succinea (Frey and Leuckart) is the dominant benthic macroinvertebrate in the Salton Sea. It is widely distributed during periods
of mixing (winter and spring), and inhabits only shallow water areas following development of anoxia in summer. The contribution
of N. succinea to sediment phosphorus regeneration was investigated using laboratory incubations of cores under lake temperatures and dissolved
oxygen concentrations typical of the Salton Sea. Regeneration rates of soluble reactive phosphorus (SRP) were lowest (−0.23–1.03
mg P m−2 day−1) under saturated oxygen conditions, and highest (1.23–4.67 mg P m−2 day−1) under reduced oxygen levels. N. succinea most likely stimulated phosphorus regeneration under reduced oxygen levels via increased burrow ventilation rates. Phosphorus
excretion rates by N. succinea were 60–70% more rapid under reduced oxygen levels than under saturated or hypoxic conditions. SRP accounted for 71–80% of
the dissolved phosphorus excreted under all conditions. Whole-lake SRP regeneration rates predicted from N. succinea biomass densities are highest in early spring, when the lake is mixing frequently and mid-lake phytoplankton populations
are maximal. Thus, any additional phosphorus regenerated from the sediments at that time has potential for contributing to
the overall production of the lake.
Guest Editor: John M. Melack
Saline Water and their Biota 相似文献
10.
Eu Gene Chung S. Geoffrey Schladow Joaquim Perez-Losada Dale M. Robertson 《Hydrobiologia》2008,604(1):57-75
A linked hydrodynamic and water quality model was developed and applied to the Salton Sea. The hydrodynamic component is based
on the one-dimensional numerical model, DLM. The water quality model is based on a new conceptual model for nutrient cycling
in the Sea, and simulates temperature, total suspended sediment concentration, nutrient concentrations, including and DO concentration and chlorophyll a concentration as functions of depth and time. Existing water temperature data from 1997 were used to verify that the model
could accurately represent the onset and breakup of thermal stratification. 1999 is the only year with a near-complete dataset
for water quality variables for the Salton Sea. The linked hydrodynamic and water quality model was run for 1999, and by adjustment
of rate coefficients and other water quality parameters, a good match with the data was obtained. In this article, the model
is fully described and the model results for reductions in external phosphorus load on chlorophyll a distribution are presented.
Guest editor: S. H. Hurlbert
The Salton Sea Centennial Symposium. Proceedings of a Symposium Celebrating a Century of Symbiosis Among Agriculture, Wildlife
and People, 1905–2005, held in San Diego, California, USA, March 2005 相似文献
11.
In order to examine the transport of contaminants associated with river-derived suspended particles in the Salton Sea, California,
large volume water samples were collected in transects established along the three major rivers emptying into the Salton Sea
in fall 2001. Rivers in this area carry significant aqueous and particulate contaminant loads derived from irrigation water
associated with the extensive agricultural activity, as well as wastewater from small and large municipalities. A variety
of inorganic constituents, including trace metals, nutrients, and organic carbon were analyzed on suspended material isolated
from water samples collected at upriver, near-shore, and off-shore sites established on the Alamo, New, and Whitewater rivers.
Concentration patterns showed expected trends, with river-borne metals becoming diluted by organic-rich algal particles of
lacustrine origin in off-shore stations. More soluble metals, such as cadmium, copper, and zinc showed a more even distribution
between sites in the rivers and off-shore in the lake basin. General distributional trends of trace elements between particulate
and aqueous forms were discerned by combining metal concentration data for particulates from this study with historical aqueous
metals data. Highly insoluble trace metals, such as iron and aluminum, occurred almost entirely in the particulate phase,
while major cations and approximately 95% of selenium were transported in the soluble phase. Evidence for greater reducing
conditions in the New compared to the Alamo River was provided by the greater proportion of reduced (soluble) manganese in
the New River. Evidence of bioconcentration of selenium and arsenic within the lake by algae was provided by calculating “enrichment”
concentration ratios from metal concentrations on the algal-derived particulate samples and the off-shore sites.
Guest editor: S. H. Hurlbert
The Salton Sea Centennial Symposium. Proceedings of a Symposium Celebrating a Century of Symbiosis Among Agriculture, Wildlife
and People, 1905–2005, held in San Diego, California, USA, March 2005
Roy A. Schroeder—Retired. 相似文献
12.
Spatial variation of phosphorus fractions in bottom sediments and the potential contributions to eutrophication in shallow lakes 总被引:1,自引:0,他引:1
Yuichi Ishii Satoshi Harigae Shiho Tanimoto Tohru Yabe Tomohiko Yoshida Kazuo Taki Nobuyuki Komatsu Keiji Watanabe Masami Negishi Hideki Tatsumoto 《Limnology》2010,11(1):5-16
Spatial variation of phosphorus fractions in bottom sediment, pore water and overlying water in three shallow eutrophic lakes,
Nishiura, Kitaura and Sotonasakaura, Japan, and the contributions of the fractional P to mobilization of phosphorus from sediment
were examined in this study. The vertical distributions of dissolved inorganic phosphorus (DIP) concentrations in overlying
and pore water differed with lake and sampling site. In particular, DIP was high in pore water in the surface layer of the
sediment for the middle to downlake areas of Lake Kitaura. DIP release flux calculated from a gradient of the concentrations
at the sediment–water interface was high compared with other sites. The distribution of fractional P content in sediments
was highly variable. The citrate–dithionite–bicarbonate–non-reactive phosphorus (CDB–NRP) fraction, in particular, differed
greatly among the three lakes. According to correlation in the ratios between CDB–NRP and loss on ignition, sediments of these
lakes were classified in three clusters. The CDB–NRP fraction was suggested to play a role in DIP release from sediment. The
possibility of nitrate concentration playing a role in the control of DIP release was considered. 相似文献
13.
The Salton Sea is a highly eutrophic, hypersaline terminal lake that receives inflows primarily from agricultural drainages
in the Imperial and Coachella valleys. Impending reductions in water inflow at Salton Sea may concentrate existing contaminants
which have been a concern for many years, and result in higher exposure to birds. Thus, waterbird eggs were collected and
analyzed in 2004 and compared with residue concentrations from earlier years; these data provide a base for future comparisons.
Eggs from four waterbird species (black-crowned night-heron [Nycticorax nycticorax], great egret [Ardea alba], black-necked stilt [Himantopus mexicanus], and American avocet [Recurvirostra Americana]) were collected. Eggs were analyzed for organochlorine pesticides, polychlorinated biphenyls (PCBs), metals, and trace elements,
with current results compared to those reported for eggs collected from the same species and others during 1985–1993. The
two contaminants of primary concern were p,p′-DDE (DDE) and selenium. DDE concentrations in night-heron and great egret eggs collected from the northwest corner of Salton
Sea (Whitewater River delta) decreased 91 and 95%, respectively, by 2004, with a concomitant increase in eggshell thickness
for both species. Decreases in bird egg DDE levels paralleled those in tissues of tilapia (Oreochromis mossambicus × O. urolepis), an important prey species for herons and egrets. Despite most nests of night-herons and great egrets failing in 2004 due
to predation, predicted reproductive effects based on DDE concentrations in eggs were low or negligible for these species.
The 2004 DDE findings were in dramatic contrast to those in the past decade, and included an 81% decrease in black-necked
stilt eggs, although concentrations were lower historically than those reported in night-herons and egrets. Selenium concentrations
in black-necked stilt eggs from the southeast corner of Salton Sea (Davis Road) were similar in 1993 and 2004, with 4.5–7.6%
of the clutches estimated to be selenium impaired during both time periods. Because of present selenium concentrations and
future reduced water inflow, the stilt population is of special concern. Between 1992 and 1993 and 2004 selenium in night-heron
and great egret eggs from the Whitewater River delta at the north end of the Sea decreased by 81 and 55%, respectively. None
of the night-heron or egret eggs collected in 2004 contained selenium concentrations above the lowest reported effect concentration
(6.0 μg/g dw). Reasons for selenium decreases in night-heron and egret eggs are unknown. Other contaminants evaluated in 2004
were all below known effect concentrations. However, in spite of generally low contaminant levels in 2004, the nesting populations
of night-herons and great egrets at Salton Sea were greatly reduced from earlier years and snowy egrets (Egretta thula) were not found nesting. Other factors that include predation, reduced water level, diminished roost and nest sites, increased
salinity, eutrophication, and reduced fish populations can certainly influence avian populations. Future monitoring, to validate
predicted responses by birds, other organisms, and contaminant loadings associated with reduced water inflows, together with
adaptive management should be the operational framework at the Salton Sea.
Guest editor: S. H. Hurlbert
The Salton Sea Centennial Symposium. Proceedings of a Symposium Celebrating a Century of Symbiosis Among Agriculture, Wildlife
and People, 1905–2005, held in San Diego, California, USA, March 2005 相似文献
14.
Phosphorus release from the sediments of very shallow lakes, the Norfolk Broads, can be as high as 278 mgP m-2 d-1. These high rates are associated with high total sediment Fe:P ratios and occur when sulphide from sulphate reduction removes Fe(II) from the pore water. There is also evidence that bioturbation from benthic chironomids can enhance phosphorus release rates, particularly in sediments low in total iron. The release of phosphorus from the sediments of these lakes is delaying restoration following the control of phosphorus from sewage discharges. Biomanipulation is being used in these lakes to create clear water and re-establish aquatic macrophytes. This removal of fish has allowed larger populations of benthic chironomid larvae to develop which may result in an increase in the rate of phosphorus release and changes to the pore profiles of dissolved phosphorus, soluble iron and free sulphide. 相似文献
15.
The Salton Sea, a hypersaline lake located in Southern California, is a major habitat for migratory waterfowl, including endangered species, recently threatened by selenium toxicity. Selenium is both an essential micronutrient and a contaminant and its speciation and cycling are driven by microbial activity. In the absence of oxygen, microorganisms can couple the oxidation of organic matter with the reduction of soluble selenate and selenite to elemental selenium. In order to better understand and quantify selenium cycling and selenium transfer between water and underlying sediments in the Salton Sea, we measured the maximum potential selenate reduction rates (R max) and selenate adsorption isotherms in sediments collected from seven littoral locations in July 2011. We also measured salinity, organic carbon, nitrogen, and elemental selenium content and the abundance of selenate-reducing prokaryotes at each site. Our results showed a high potential for selenate reduction and limited selenate adsorption in all studied sites. Maximum potential selenate reduction rates were affected by sediment Corg content. We showed that selenate reduction potential of Salton Sea sediments far outweighs current dissolved inputs to the lake. Selenate reduction is thus a likely driver for selenium removal from the lake’s water and selenate retention in littoral sediments of the Salton Sea. 相似文献
16.
The Salton Sea is a 1000-km2 terminal lake located in the desert area of southeastern California. This saline (44000 mg l–1 dissolved solids) lake started as fresh water in 1905–07 by accidental flooding of the Colorado River, and it is maintained by agricultural runoff of irrigation water diverted from the Colorado River. The Salton Sea and surrounding wetlands have recently acquired substantial ecological importance because of the death of large numbers of birds and fish, and the establishment of a program to restore the health of the Sea. In this report, we present new data on the salinity and concentration of selected chemicals in the Salton Sea water, porewater and sediments, emphasizing the constituents of concern: nutrients (N and P), Se and salinity. Chemical profiles from a Salton Sea core estimated to have a sedimentation rate of 2.3 mm yr–1 show increasing concentrations of OC, N, and P in younger sediment that are believed to reflect increasing eutrophication of the lake. Porewater profiles from two locations in the Sea show that diffusion from bottom sediment is only a minor source of nutrients to the overlying water as compared to irrigation water inputs. Although loss of N and Se by microbial-mediated volatilization is possible, comparison of selected element concentrations in river inputs and water and sediments from the Salton Sea indicates that most of the N (from fertilizer) and virtually all of the Se (delivered in irrigation water from the Colorado River) discharged to the Sea still reside within its bottom sediment. Laboratory simulation on mixtures of sediment and water from the Salton Sea suggest that sediment is a potential source of N and Se to the water column under aerobic conditions. Hence, it is important that any engineered changes made to the Salton Sea for remediation or for transfer of water out of the basin do not result in remobilization of nutrients and Se from the bottom sediment into the overlying water. 相似文献
17.
Iron:phosphorus ratio in surface sediment as an indicator of phosphate release from aerobic sediments in shallow lakes 总被引:29,自引:8,他引:29
Analysis of Danish lakes showed that both mean winter and mean summer concentrations of lake water total phosphorus in the trophogenic zone correlated negatively with the total iron to total phosphorus ratio (Fe:P) in surface sediments. No correlation was found between the water total phosphorus concentration and either the sediment phosphorus concentration alone or with sediment calcium concentration. The increase in total phosphorus from winter to summer, which is partly a function of net internal P-loading, was lowest in lakes with high Fe:P ratios in the surface sediment.A study of aerobic sediments from fifteen lakes, selected as representative of Danish lakes with respect to the sediment Fe and phosphorus content, showed that the release of soluble reactive phosphorus was negatively correlated with the surface sediment Fe:P ratio. Analysis of phosphate adsorption properties of surface sediment from 12 lakes revealed that the capability of aerobic sediments to buffer phosphate concentration correlated with the Fe:P ratio while the maximum adsorption capacity correlated with total iron. Thus, the Fe:P ratio may provide a measure of free sorption sites for orthophosphate ions on iron hydroxyoxide surfaces.The results indicate that provided the Fe:P ratio is above 15 (by weight) it may be possible to control internal P-loading by keeping the surface sediment oxidized. Since the Fe:P ratio is easy to measure, it may be a useful tool in the management of shallow lakes. 相似文献
18.
Long-term monitoring data (1968–2008) were used to investigate internal phosphorus (P) loading following external P loading
reduction in shallow Loch Leven, Scotland. A whole-lake sediment P inventory (upper 3 cm of sediment; 2005) suggested a release-potential
of 29.7 tonnes (t) from the release sensitive sediment P pools. 18.5 t was contained within shallow water sediments (<4.5 m
water depth) with 7.6 t in deeper water sediments below the photic zone (>5 m water depth). The “observed” release (<5.1 t),
estimated using a water column P mass balance approach (1989–2008), was <5.1 t, indicating the presence of regulating mechanisms.
Observed P release declined between 1989 and 2008, with the exception of 2003–2006. Observed P release estimates were positively
correlated with annual average water column P concentration after 1989, highlighting the role of internal loading in maintaining
poor water quality conditions after management intervention. Multiple regression analysis suggested that internal loading
was driven by the wave mixed depth in spring (positive driver), summer water temperature (positive driver) and spring water
clarity transparency (negative driver). The potential importance of biological and physico-chemical feedback mechanisms in
the regulation of benthic–pelagic coupling and water quality in Loch Leven are discussed. 相似文献
19.
Chemical and physical characteristics of the Salton Sea, California 总被引:15,自引:15,他引:0
A 1-year sampling program was conducted to assess current chemical and physical conditions in the Salton Sea. Analyses included general physical conditions and a suite of water quality parameters, including nutrients, trophic state variables, major cations and anions, trace metals and organic compounds. Samples were collected from three locations in the main body of the lake and from the three major tributaries. Nutrient concentrations in the Salton Sea are high and lead to frequent algal blooms, which in turn contribute to low dissolved oxygen concentrations. The tributaries consist primarily of agricultural return flows with high nutrient levels. Concentrations of trace metals and organic compounds do not appear to be of major concern. Two geochemical models, PHRQPITZ and PHREEQC, were used to evaluate potential chemical reactions limiting the solubility of selected water quality variables. Modeling indicated that the Salton Sea is supersaturated with respect to calcite, gypsum, and other minerals. Precipitation of these minerals may serve as a sink for phosphorus and limit the rate of salt accumulation in the Salton Sea. 相似文献
20.
Characterization of phosphorus fractions in the sediments of a tropical intertidal mangrove ecosystem 总被引:2,自引:0,他引:2
Solid phases of phosphorus fractions in the surface and core sediments were studied to understand the biogeochemical cycling
and bioavailability of phosphorus in the Pichavaram intertidal mangrove sediments of India. Total P in surface and core sediments
ranged between 451–552 and 459–736 μg g−1 respectively and Fe bound P was the dominant fraction. Low levels of Fe bound P in the mangrove zone than the two estuarine
zones may be because of high salinity inhibition of phosphate adsorption onto the Fe-oxides/hydroxides. Post-depositional
reorganization of P was observed in surface sediments, converting organic P and Fe bound P into the authigenic P. High levels
of organic P in the mangrove zone is primarily due to intensive cycling and degradation of organic matter and adsorption of
phosphate on the organic molecules. The burial rates and regeneration efficiency of P in the intertidal mangrove ecosystem
ranged from 5.41 to 7.27 μmol P cm−2 year−1 and 0.122 to 0.233 μmol P cm−2 year−1, respectively. High burial efficiency (≈99%) of P proves the earlier observation of limiting nature of P for the biological
productivity. Further, bioavailable P (exchangeable P + Fe bound P + organic P) constituted a considerable proportion of sedimentary
P pool of which an average accounted for 55 and 50% in surface and core sediments respectively. The results indicate that
significant amount of P is locked in sediments in the form of authigenic P and detrital P which makes P as a limiting nutrient
for the biological productivity. 相似文献