Internal phosphorus loading in a shallow eutrophic lake

Internal loading of phosphorus has been implicated as a major eutrophicating factor in Long Lake, Washington (Kitsap County). As a result of such loading, summer total phosphorus concentrations approach or exceed 100 μgP l⁻¹. Most of the summer loading of phosphorus is thought to have been released directly from the rich, flocculent sediment in the mid and northern part of the lake as a result of high pH (up to 10) related to phytoplankton photosynthesis. The lake also supports a dense submersed macrophyte crop (areal weighted mean dry weight of about 220 g m⁻²) composed primarily of Elodea densa. Although excretion of phosphorus from healthy E. densa was found to be minimal, the potential contribution of P indirectly from sediment via macrophyte uptake and subsequent decomposition in the winter was on the order of 200–400 kg yr⁻¹ or about 25–50% of the external loading. Nevertheless, loading of phosphorus during predrawdown summers is thought to have originated largely as a direct release from sediment due to high pH. Estimates of sediment phosphorus release determined from laboratory experiments, mass balance and core analyses ranged from 2.2 to 5.6 mg m⁻² day⁻¹.As a component of the restoration program, the lake (mean depth of 2 m) was drawn down nearly 2 m for 4 months during the summer and fall of 1979. The lake's trophic status was expected to improve due to sediment consolidation and/or macrophyte reduction. The drawdown resulted in an 84% reduction in macrophyte biomass in 1980 but minimal sediment consolidation (0.1 m). Winter decomposition of the much smaller macrophyte crop, apparently provided insufficient phosphorus in the spring to stimulate phytoplankton and to enrich midlake sediments, which has probably occurred in previous years. Low water column pH during the postdrawndown summer of 1980 resulted from relatively low rates of plankton photosynthesis. During the summer of 1980 internal loading of phosphorus was reduced and total phosphorus remained below 50 μg l⁻¹.     

Mercury accumulation and attenuation at a rapidly forming delta with a point source of mining waste

The Walker Creek intertidal delta of Tomales Bay, California is impacted by a former mercury mine within the watershed. Eleven short sediment cores (10 cm length) collected from the delta found monomethylmercury (MMHg) concentrations ranging from 0.3 to 11.4 ng/g (dry wt.), with lower concentrations occurring at the vegetated marsh and upstream channel locations. Algal mats common to the delta's sediment surface had MMHg concentrations ranging from 7.5 to 31.5 ng/g, and the top 1 cm of sediment directly under the mats had two times greater MMHg concentrations compared to adjacent locations without algal covering. Spatial trends in resident biota reflect enhanced MMHg uptake at the delta compared to other bay locations. Eighteen sediment cores, 1 to 2 m deep, collected from the 1.2 km² delta provide an estimate of a total mercury (Hg) inventory of 2500 ± 500 kg. Sediment Hg concentrations ranged from pre-mining background conditions of approximately 0.1 μg/g to a post-mining maximum of 5 μg/g. Sediment accumulation rates were determined from three sediment cores using measured differences of ¹³⁷Cs activity. We estimate a pre-mining Hg accumulation of less than 20 kg/yr, and a period of maximum Hg accumulation in the 1970s and 1980s with loading rates greater than 50 kg/yr, corresponding to the failure of a tailings dam at the mine site. At the time of sampling (2003) over 40 kg/yr of Hg was still accumulating at the delta, indicating limited recovery. We attribute observed spatial evolution of elevated Hg levels to ongoing inputs and sediment re-working, and estimate the inventory of the anthropogenic fraction of total Hg to be at least 1500 ± 300 kg. We suggest ongoing sediment inputs and methylation at the deltaic surface support enhanced mercury levels for resident biota and transfer to higher trophic levels throughout the Bay.     

The variations of mercury in sediment profiles from a historically mercury-contaminated reservoir, Guizhou province, China

Baihua Reservoir in Guizhou Province, China, experienced serious Hg contamination from Guizhou Organic Chemical Plant (GOCP) between 1971 and 1997. However, the biogeochemical cycling of Hg in this reservoir is not well studied. Sediment cores were collected in fall 2002, spring 2003 and in spring and fall 2004. THg and MeHg concentrations in all sediment profiles ranged from 0.26 to 38.9 mg/kg and from 0.5 to 27.5 μg/kg (d.w.), respectively. The distribution of THg in sediment cores was characterized by a few peaks, which may correspond to the Hg-containing wastewater discharge history of the GOCP. The average THg concentrations in sediments cores decreased from upstream to downstream due to the deposition of particulate Hg, which is the major form of Hg in water. THg and MeHg concentrations in pore water varied from 6.1 to 5860 ng/L and from 0.3 to 15.4 ng/L, respectively, which were significantly higher than levels in the overlying water column. Average diffusive flux from sediment to water is 1642 and 36 ng/m²/day for THg and MeHg. The spatial distribution of THg in pore water from upstream to downstream showed the same trend as the sediment, but MeHg in pore water did not show a declining pattern with distance from the GOCP. These results suggested that sediments experienced serious contamination of Hg, and the contaminated sediment is an important Hg contamination source to the overlying water.     

In situ sediment oxygen demand determinations in the Passaic River (NJ) during the late summer/early fall 1983

In situ sediment oxygen demand rate determinations were performed on the freshwater Passaic River system during the late summer/early fall of 1983. Values obtained ranged from non-detectable to 2.43 g m⁻² day⁻¹. The values obtained were compared with values obtained historically from similar locations. The dependency of the SOD rate on temperature was observed in consonance with the observations of other investigators performing laboratory experiments.     

Kinetics of sediment oxygen demand

Sediment oxygen demand (SOD) is expressed in terms of oxygen uptake when using a batch method. For small quantities of sediment, the oxygen uptake is independent of initial oxygen present. The kinetics of the SOD reaction in a batch method can best be explained by the relationship SOD = k log t + c. This empirical relationship is perceived to be the result of an inhibition effect that comes into play through the oxidation of iron (Fe²⁺) on the surface of the sediment. The formation of an insoluble coating (Fe³⁺) presumably reduces the rate of oxidation and consequently the rate of oxygen uptake at the surface of the sediment. A derivation of this relationship is offered in support of this view.     

Degradation of 14c‐maneb in sediment from a Nicaraguan estuary

Sediment samples were collected at 5 sites in the Nicaraguan estuary “El Naranjo” in July 94 and September 94. The samples were incubated with ¹⁴C‐maneb (0.08 μg.g^‐1 dw sediment), and evolved ¹⁴CO₂ and residual ¹⁴C‐ETU in soil were measured. Mineralization kinetics of ^I4C‐maneb was best described with kinetic models which include growth of microorganisms. The amounts of ¹⁴C‐maneb mineralized were highest at the sites closest to the mouth of the river. No significant differences in degradation between July and September were seen. After 67 days between 9.73 and 16.18% of added ¹⁴C had evolved as ¹⁴CO₂ in the July samples and after 150 days between 11.18 and 27.37% of added ¹⁴C had evolved as ¹⁴CO₂ from the September samples. When 4.61–8.20% of added ^I4C was found in the soil extract, 0.00–2.72% was ¹⁴C‐ETU.     

Benthic oxygen demand in Lake Apopka, Florida

The benthic oxygen demand of Lake Apopka, Florida was determined using laboratory core uptake and flow through system techniques. The core-uptake for 5 stations in Lake Apopka averaged 67 mg O₂ m⁻²-h and partitioning experiments indicated that the oxygen uptake was primarily biological, with bacterial respiration dominating. No significant statistical correlations were found between core oxygen uptake rates and TKN levels (r = 0.33), percent volatile solids (r = 0.49), or macroinvertebrate densities (r = 0.59). Sediment oxygen uptake rates (D_B) were logarithmically related to flow rate in the following form D_B = − A + B In flow. Flow-through system sediment oxygen uptake at each station approached similar maximum uptake rates of 130 mg O₂ m⁻²-h at high (> 200 l h⁻¹) flow rates. Lake Apopka is an extremely shallow, wind mixed system and sediment uptake rates are expected to approximate this value during periods of intense wind mixing. The relatively low sediment uptake rates obtained for Lake Apopka, a hypereutrophic lake, supports the view that during eutrophication sediment respiration is progressively replaced by respiration in the water column.     

Suppression of phosphorus release from lake sediments by the addition of nitrate

An assessment was made of the effectiveness of nitrate in reducing phosphorus release from the anoxic sediments of a small dimictic lake, White Lough, N. Ireland. Laboratory experiments on sediment cores showed that nitrate delayed and reduced phosphorus release with an input of 61 gN m⁻² causing complete suppression. The addition of 24 gN m⁻² of nitrate to the sediment of White Lough resulted in a delay and reduction of phosphorus release similar to that observed in the laboratory core experiments. Sediment release of iron in the lake was also delayed and reduced but manganese release and the rate of hypolimnetic deoxygenation were unaffected by the nitrate addition. Ammonium release rates in the sediment cores and in the whole lake experiment did not vary with nitrate input. Comparing the costs of using nitrate or iron/aluminium salts to suppress sediment phosphorus release indicated that the nitrate method was at least 80% more expensive.     

Characterization, performance modeling, and design of an active capping remediation project in a heavily polluted urban channel

Collateral Channel is a heavily polluted former navigation slip to the Chicago Sanitary and Ship Canal (Illinois, USA). Characterization of sediment cores taken in the channel show high levels of heavy metals, polycyclic aromatic hydrocarbons (PAHs) and other contaminants in deposited sediment dating back to the 1800's. Of these, PAHs were the contaminants of greatest concern based upon exceedance of sediment contamination criteria (Σ₁₆ PAHs up to 1500 mg/kg). Benthic animal counts revealed a lack of biodiversity, with relatively low levels of small tubificid oligochaetes (generally < 3000/m²) in surficial sediments. Comparison of surficial sediment contaminant levels between 1995 and 2005 showed few decreases in contaminant levels, indicating a lack of “natural recovery” processes occurring in the channel. These results led to an analysis of sediment amendments for an active capping demonstration project in the channel using transport models developed in our previous work (Viana et al., 2008). Based on the sediment characterization and modeling results, the active capping design will be focused on organic contaminant sequestration through the use of organoclay. A site-specific difficulty is the substantial rates of gas ebullition from anaerobic organic matter biodegradation in the sediments, particularly in the summer months. These gases can open advective channels that may result in substantial pollution release and compromise cap effectiveness, and thus the capping scenario must control for such releases. The active capping layer will underlay a sloped sand layer and a high permeability gas venting system to allow biogenically-produced gas migration to shoreline collectors through an innovative support grid. The cap will include an overlaying wetland to remove nutrients from the adjoining Chicago River and provide a public recreational space.     

Sorption and accumulation of cadmium in the sediment of the Tama River

Cadmium contents in the water and the sediment samples collected from the Tama River and several branches were measured. Cadmium (above 0.005mgl⁻¹) was detected in only four of the water samples, while the sediment samples showed cadmium content of 1.0–9.8 μg g⁻¹ dry sediment. Cadmium concentration in the sediments of the main stream was correlated against ignition loss of the samples and it was found that 1 g of ignition loss (organic matter) corresponded to 35 μg of cadmium.The batch adsorption experiment in the laboratory using an aqueous solution of cadmium for 14 sediment samples with a higher concentration of cadmium indicated that the amount adsorbed by the sediment is highly dependent on the ignition loss. The amount adsorbed on unit mass of ignition loss q_IL could be correlated by a Freundlich-type equilibrium relation as where C is the equilibrium concentration in the aqueous phase ranging between 7 × 10⁻³ and 10 mg l⁻¹, while k_IL and n are equilibrium constants.The adsorption rate measurement showed that the intraparticle diffusion coefficient of cadmium in the sediment was about 1.1 × 10⁻⁶ cm²s⁻¹, which is of a reasonable order of magnitude assuming the pore diffusion mechanism inside the particle.The results suggest that suspended solid particles of high organic content in flowing water contribute significantly to the transport of cadmium along the river.     

Effect of nitrate concentration in lake water on phosphate release from the sediment

Thirty-one Danish eutrophic lakes were investigated routinely over 1 year during the period 1978–1980. Nine lakes were dimictic with anoxic hypolimnia and 22 were very productive and shallow, polymictic lakes. Phosphate release from the sediment resulted in large increases in phosphate concentrations in anoxic hypolimnion, if concentrations of oxidized nitrogen in hypolimnion were less than about 0.1 g N m⁻³. If concentration of oxidized nitrogen (mainly nitrate) in hypolimnion was about 1 g N m⁻³ or higher, no release of phosphate from the sediment to anoxic hypolimnion occurred. In lakes with no summer stratification a release of phosphate from the sediment to the well oxygenated water resulted in summer maxima of phosphate in the lake water, when nitrate concentration in the water was less than about 0.5 g N m⁻³, but no release took place if nitrate concentration exceeded about 0.5 g N m⁻³. This effect of oxidized nitrogen in preventing phosphate release from the sediment demonstrates the ability of oxidized nitrogen to buffer the redox potential of the surface sediment at a level high enough to prevent a release of phosphate. Thus, among the efforts to limited phytoplankton biomass in lakes an artificial enrichment with nitrate may in some cases be an important supplement to the usually necessary reduction in phosphorus loading, but the possibility of a stimulation of phytoplankton growth through the addition of nitrate must be carefully considered.     

Temporal variation of pharmaceuticals in an urban and agriculturally influenced stream

Pharmaceuticals have become ubiquitous in the aquatic environment. Previous studies consistently demonstrate the prevalence of pharmaceuticals in freshwater but we do not yet know how concentrations vary over time within a given system. Two sites in central Indiana with varying land use in the surrounding watershed (suburban and agricultural) were sampled monthly for pharmaceutical concentrations and stream physiochemical parameters. Sediment samples were also collected at each sampling event for measurement of δ¹⁵N natural abundance and sediment organic content. Across sites and sampling events, twelve pharmaceuticals were detected including acetaminophen, caffeine, carbamazepine, cotinine, N,N-diethyl-meta-toluamide (DEET), gemfibrozil, ibuprofen, sulfadimethoxine, sulfamethazine, sulfamethoxazole, triclosan, and trimethoprim. Sulfathiazole, lincomycin, and tylosin were not detected at either site at any time. The agriculturally-influenced site had comparable pharmaceutical concentrations to the urban-influenced site. In general, pharmaceutical concentrations increased during winter at both sites and decreased during spring and summer. Multiple regression analyses indicated that water column dissolved oxygen, the number of days since precipitation, and solar radiation influenced total pharmaceutical concentration in the urban-influenced site; whereas pH, chlorophyll a concentration, and total amount of rainfall in the previous 10 days influenced total pharmaceutical concentrations in the agriculturally-influenced site. Pharmaceutical concentrations were not correlated with sediment δ¹⁵N across or within sites. However, sediment in the urban-influenced site had higher mean δ¹⁵N signatures relative to sediment in the agriculturally-influenced site. These data indicate pharmaceuticals are persistent in aquatic ecosystems influenced by both agricultural and suburban activity. Pharmaceuticals are designed to have a physiological effect; therefore, it is likely that they may also influence aquatic organisms, potentially threatening freshwater ecosystem health.     

Effect of particulate Abate insecticide on invertebrate stream drift communities in Newfoundland

A particulate formulation of Abate was used to control blackfly (Diptera: Simuliidae) larvae in Newfoundland. The effects of this compound on stream invertebrates during routine field use was observed by using drift fauna collected in relation to five insecticide treatments using dosage ranging from 0.059–0.091 ppm Abate applied for 18–23 minutes in four different streams. Invertebrate populations varied from stream to stream and the effects of the insecticide on the drift reflect community structure and physical parameters in the stream. Numbers of larvae of Chironomidae (Diptera), Trichoptera, Ephemeroptera and Plecoptera increase in drift after dosing at concentrations of insecticide less than those recommended for Abate when administered as an emulsifiable concentrate. Drifting blackfly larvae increased from five percent up to 40 percent of total drifting communities after the insecticide was applied.     

Endogenous nitrate production in an experimental enclosure during summer stratification

The biological production of nitrate was studied during the summer of 1976 in the water column of an 18.500 m³ capacity experimental enclosure in Blelham Tarn, English Lake District, to which 11 kg NaNO₃ (enriched with 9.63 atom % excess ¹⁵N) and 0.789 kg KH₂PO₄ had been added. Nitrification was detected in the water column during stratification and was maximal within a 2 m deep zone centered on a depth of 8.0 m in the metalimnion and upper hypolimnion, where numbers of autotrophic nitrifying bacteria were highest. Calculated rates of nitrification in this zone based on BOD measurements. N-Serve-sensitive bicarbonate incorporation, regression analysis of the daily changes in nitrate-nitrogen at 8.0 m and integrated changes in nitrate-nitrogen throughout the metalimnion and hypolimnion during late August 1976 were respectively: 55.4, 45.0, 22.4 and 39 μg N 1⁻¹ day⁻¹. The importance of sediment-derived ammonium for nitrifying bacteria and the fate of nitrate produced by nitrification are discussed.     

The effects of hypolimnetic aeration on iron-phosphorus interactions

Two circular enclosures (8 m dia × 14 m deep) were used to monitor rates of phosphorus sedimentation and regeneration in the presence of oxygenated and anoxic hypolimnetic water and under conditions of low and high iron concentrations. These manipulations showed that during spring turnover, sedimentation of soluble reactive phosphorus (SRP-P) was greater in the enclosure that received hypolimnetic aeration than in the non-aerated enclosure. During the summer (June–September), SRP-P moved from the sediments to the water columns of both enclosures. This suggested that iron (III) substrate might be lacking and so we added iron to the hypolimnetic water of both enclosures. In the aerated enclosure, phosphorus sedimentation occurred almost at once. In the non-aerated enclosure, iron addition had no effect. Sediment trap analysis showed that during the period of iron addition, the rate of TP-P sedimentation in the aerated enclosure increased threefold and the ratio of iron to phosphorus in the sedimented material was 10:1. Throughout the experiment, the non-aerated enclosure lost an average of 0.7 mg SRP-P m⁻² d⁻¹ to the sediments and the aerated enclosure lost 6.1 mg SRP-P m⁻² d⁻¹. The results appeared to be entirely controlled by hypolimnetic oxygen concentrations and by concentration of SRP-P and T-Fe. This suggests that management of these parameters in combination with hypolimnetic aeration should yield predictable results in any stratified fresh water environment.     

Quantifying panel zone effect on deflection amplification factor

Drift is a dominant feature in tall‐building design and can dictate the selection of structural systems. Because a reliable estimate of actual drifts is crucial for controlling structural damage, estimating drift considering intricate details seems noteworthy. In order to estimate story drifts during massive quakes, seismic design provisions generally specify a deflection amplification factor (C_d) to amplify elastic design drifts. In most of these codes, the amount of C_d is calculated from line‐element models without considering panel zone effects, despite the panel zone intensifying the story drift considerably. Therefore, the effect of panel zone on the story drift and C_d has been investigated in the current paper. Because C_d is independent of the number of stories, 4‐story frames, as benchmarks for special steel moment frames, with different thicknesses of the panel zone, are used. The effect of panel zone is provided as a correction factor for C_d. The results show that the panel zone should be considered in the analytical models; otherwise, the story drift will be underestimated up to 35%. Finally, a relation has been derived to consider panel zone effects on C_d, as a function of the panel zone thickness.     

Psychrotrophic bacteria in sediments from the great lakes

The in vitro growth rates at 0°C of 8 representative psychrotrophs, isolated from Great Lake's sediment, ranged from k values of 0.047-0.022 h⁻¹ and generation times of 14.46-30.69 h. Faster rates were obtained at 15, 20 and 25°C, ranging from k values of 0.205-0.055 h⁻¹ and generation times of 3.38-12.48 h, with the optimum growth rate occurring at either 20°C or higher. Measurement of in situ microbial growth at 0°C in sediment columns by direct microscopy and protein-labelling fluorescent staining showed increases in microbial numbers of 10-fold when the sediment columns were amended with glucose, and 23-fold when amendment was with a more natural supplement, specifically, algal detritus. Determination of the number of viable microorganisms in the sediment columns again showed that considerable increases occurred at 0°C when glucose and detritus were added as substrates. Examination of the types of microbes occurring, during the growth conditions at 0°C when the substrates were added, by microscopy, and isolation of representative microbial types by replica plating showed that different populations responded to the two amendments.     

Comparative study on organic constituents in polluted and unpolluted inland aquatic environments—II: Features of fatty acids for polluted and unpolluted waters

Fatty acids were analyzed for polluted river waters from the Tokyo area and unpolluted river, brook, reservoir and pond waters from the Ogasawara (Bonin) Islands to elucidate their features for polluted and unpolluted waters. Fatty acids ranging from the carbon chain length of C₈-C₃₄ including unsaturated and branched acids were found with the great predominance of even-carbon numbers and lower molecular weight ranges (C₁₃–C₁₉) in the water samples from the Tokyo area and Ogasawara Islands. It was thus confirmed that no marked changes in fatty acid composition between polluted and unpolluted waters are absent. However, the total contents of the acids (average, 270 ± 120 μg 1⁻¹ at 90% confidence limits) as well as the FAC (fatty acids as carbon)/TOC (total organic carbon, 2.6 ± 0.93%) and FAC/EOC (extractable organic carbon with ethyl acetate, 16 ± 6.7%) of river water samples from the Tokyo area were considerably higher than those of the waters from the Ogasawara Islands (58 ± 29 μg 1⁻¹, 0.79 ± 0.48% and 2.1 ± 0.51%, respectively). These higher values for the Tokyo area should be due to sewage.A filtering method showed that most of fatty acids (>95%) was present in particulate fractions. In addition, the content of free fatty acids was fairly lower than that of combined fatty acids. Further, unsaturated fatty acids were detected only in combined forms both in particulate and dissolved fractions. They are considered to be present as esters in polluted and unpolluted waters.     

Changes in zooplankton populations in the White Volta with particular reference to the effect of Abate

The 24‐hour LC 50 of the nauplii of Thermocyclops hyalinus using Abate CE 200 solution was 0.23 ppm., while the 24‐hour LC 50 of both the copepodite and adult stages was 0.2 ppm.

The numbers of drifting zooplanktonic Microcrustacea in the White Volta increased in numbers during the months of March, April, May, June and July in the dry season. The increase in numbers in the post‐sunset samples related to the vertical migration of the zoqplankton in the reservoir upstream. The aerial weekly application of Abate CE 200 solutions at very high lethal concentrations did not seem to affect the Microcrustacea population probably because (a) Microcrustacea drifting into the reservoir from upstream sustained populations in the reservoir; (b) Microcrustacea living at the banks of the reservoir escaped the abate effect flowing downstream; and (c) spraying was done around noon, when the majority of the zooplankton population had migrated to the bottom of the reservoir.     

Oxygen depletion of Hamilton Harbour

Processes involved in the oxygen cycles of the highly eutrophic Hamilton Harbour were studied. Sediment oxygen demand k_s(O₂ m⁻² day⁻¹) was measured by an in situ method and was determined to be dependent on oxygen concentrations c (m l⁻¹) in the water phase. This dependence was expressed by the equation k_s = 0.72 + 0.26 c. The water column oxygen demand of the harbour was determined experimentally and revealed a significant dependence on oxygen concentration. It was estimated that over 80% of the oxygen supplied to the harbour was used within the water column. The sediment oxygen consumed about 18% of the oxygen entering the harbour and was relatively most important in the early stages of stratification when the hypolimnetic dissolved oxygen concentrations were high. The main sources of oxygen were atmospheric reaeration (80%), lake-harbour exchange (10%) and photosynthesis (10%).