Ecotoxicological study of the influence of an industrial effluent on a net-spinning caddisfly assemblage in a regulated river

The influence of an industrial effluent on the spatial distribution of net-spinning caddisflies (Trichoptera, Insecta) in the regulated Rio Duratón (northern Spain) was studied using field and laboratory methods. The effluent caused an increase in the fluoride concentration at three downstream sampling sites (mean values 6.8, 2.7 and 1.3 mg F-L^?1 at S-3, S-4 and S-5) compared with control stations (0.1 mg F-L^?1 at S-1 and S-2). The suspended inorganic matter (SIM) only increased just below the effluent (S-3), settling on the stream bottom at this sampling station. In addition, discharge fluctuations of hypolimnial waters with a significant OZ deficit, < 5 mg L^?1 just below the reservoir (S-2), were produced daily by the dam, causing an hourly variation of fluoride concentrations at S-3, S-4 and S-5. The 48 and 72 hr LC50s (mg F-L^?1) calculated from fluoride toxicity bioassays in soft water were 79.2 and 44.9 for Hydropsyche bulbifera, 86.6 and 43.7 for H. exocellata, 112 and 59.1 for H. pellucidula, 78.2 (72 hr) for H. lobata, and 120 and 79.7 for Chimarra marginata. H. siltalai, H. bulbifera, H. exocellata and Polycentropus flavomaculatus increased their abundances at S-4 and S-5 with regard to the upstream control station (S-1). Densities of Hydropsyche sp., H. lobata, H. pellucidula, Chimarra marginata and Cheumatopsyche lepida decreased or were absent downstream from the dam. No caddisfly species was collected at S-3 during sampling surveys. It is concluded that the main physicochemical factors responsible for changes in structure and composition of the net-spinning caddisfly assemblage along the study area were short-term flow fluctuations, dissolved O₂ deficit and siltation of SIM. The increased fluoride concentration was a minor factor.     

Effects of acid mine drainage on a Southwestern Pennsylvania stream

Physicochemical parameters and benthic macroinvertebrate community structure were studied in a small valley stream in southwestern Pennsylvania. Sampling stations were located upstream and downstream of coal mine drainage input. Due to an alkaline discharge and significant downstream alkalinity the pH below the mine effluent remained between 5.8 and 7.0 throughout the course of this 18 mo study. The major factor affecting the benthic community seemed to be ferric hydroxide deposition. Certain taxa (Plecoptera and Ephemeroptera) were abundant at station sites above the mine discharge, while only those taxa tolerant of polluted conditions, such as Chironomidae and Tubifex, were prevalent at the downstream station sites. An analysis of benthic populations through changes in total numbers, species diversity, and species indicator organisms graphically demonstrated environmental stress within this aquatic ecosystem.     

Residues of 2,3,7,8-tetrachlorodibenzo-p-dioxin in the Spring River,Missouri

Contamination of the Spring River in southwest Missouri by 2,3,7,8-tetrachlorodibenzo-p -dioxin (TCDD) is believed to result from several well-defined point source waste disposal sites. Analyses of 31 fish samples and samples of crayfish, mussels, other aquatic invertebrates, and sediments collected in 1981-1983 demonstrated a rapid decline in TCDD levels in biota both upstream and downstream of the area of contamination and are believed to indicate a continuing, long term input of TCDD into the river. Mean concentrations of TCDD 0.5 km downstream from the area of contamination were 38 parts per trillion (pptr) in whole fish and 20 pptr in fish fillet; mean concentrations beyond 14 km downstream were below 4 pptr in both whole fish and fillets. Caged mussels (65 day exposure) did not accumulate TCDD (detection limit, 10 pptr). High fish consumption by local sportsmen may indicate maximum permissible concentrations of less than 5 pptr. in fish fillets.     

Comparative evaluation of NTA and EDTA for extractive decontamination of Pb-polluted soils

Nitrilotriacetic acid (NTA) and ethylenediaminetetraacetic acid (EDTA) were compared for their ability to solubilize Pb from a highly-contaminated (PbT 21%) soil collected from a battery recycling facility. For chelant concentrations below 0.04 M (representing a 1:1 chelant-to-Pb_T molar ratio), EDTA released 10 to 30% more Pb than NTA. NTA-to-Pb T ratios greater than 1:1 reduced Pb recovery because of readsorption of Pb(NTA)₂ ^4? onto positively-charged oxide soil components at pH < 8.5. For the EDTA system, however, complexation completely bound all coordination sites of Pb and EDTA, leaving no functional groups available for surface adsorption. Thus, Pb recovery progressively increased with higher EDTA concentrations, although the additional Pb release with each EDTA increment became smaller. For pH < 5 and EDTA/Pb of 2:1, Pb recovery exceeded 90%. The addition of 0.5 M NaC1O₄ enhanced Pb recovery by EDTA for pH 5 to 12, but substantially suppressed recovery by NTA for pH < 11. Because Pb release by NTA was diminished by high ionic strength and chelant-to-metal ratios, NTA may be limited as a soil washing reagent. Stronger complexation and consistent Pb desorption behavior by EDTA favors its use.     

Stormwater impact on urban waterways in a cold climate: variations in sediment metal concentrations due to untreated snowmelt discharge

Purpose

Stormwater discharges include contaminated sediments that accumulate in the receiving water body. It is thus important to investigate sediment and pollutant processes and pathways from the catchment to, and within, the receiving water. These processes may be influenced by seasonal changes. The objective of this study was to investigate the stormwater impact on receiving waters in the Luleå area, Northern Sweden; seasonal changes in contamination loads in the receiving waters due to snowmelt; and factors influencing the pollutant pathways in the receiving waters.

Materials and methods

In front of three storm sewer outlets in Luleå, samples of bottom sediment (surface layer 0–2 cm) were collected from the connecting ditches and the downstream water body in autumn and spring (before and after the snow season 2009/2010). The characteristics of the receiving waters differed in geomorphology and vegetation. The sediment was analyzed for loss-on-ignition (LOI), grain size, and bulk concentrations of SiO₂, Al₂O₃, CaO, Fe₂O₃, MnO, Na₂O, P₂O₅, TiO₂, As, Cd, Co, Cr, Cu, Hg, Ni, Pb, S, V, and Zn. The sediment contamination was compared to concentrations at a reference point in Luleå where the bottom sediment was not affected by stormwater discharges and with Swedish environmental quality guidelines. Pearson’s correlation and a principal component analysis were used to further evaluate the results.

Results and discussion

Relative to the reference point, elevated trace metal concentrations were detected in sediments at all three sampling stations. At two of the stations, seasonal variations in ditch sediment grain size, LOI, and contaminant concentrations were observed, originating from stormwater sediment. Snowmelt runoff caused an increased proportion of fine-grained sediment fractions (<0.063 mm) in spring, mainly due to changes in runoff intensity and high sediment loads in the snowmelt runoff. The retention of metals appeared to be due to low turbulence in the water and the presence of organic material.

Conclusions

Stormwater discharge affected the contaminant concentrations in the bottom sediments. The observed seasonal variation of contaminants indicated that relatively high amounts of contaminants are discharged during snowmelt and then reallocated within the receiving water body, either directly or after some temporal retention, depending on the characteristics of the receiving water. A calm water column and the presence of organic material in the receiving water body were crucial for the retention of metals.

     

Influence of acidification and aluminum on the density and biomass of lotic benthic invertebrates

Experiments were carried out in plasticized wooden channels fed by a small creek in the Reserve des Laurentides, 80 km north of Quebec city. Channels were naturally colonized by invertebrates for 65 d before treatment. Treated channels were acidified in August with dilute H₂SO₄ only, or with acid plus a solution of Al sulfate (final concentration of 0.19 mg L^?1). The control channel received creek water only (pH 6.3 to 6.9). The addition of Al had no effect on invertebrate density and biomass. After 73 d of acidification, invertebrate densities were only one third the number found in the control channel. Invertebrate hiomass was not different within channels, although biomass was generally higher in the two acidified channels. Difference in densities between acidified and non-acidified channels was attributed to lack of colonization and not to an increase in drift. Microtendipes, a large and resistant larva of Chironomidae constituted a large fraction of the hiomass, largely outweighing numerous very small larvae. Effects on the density were attributed to the direct effect of low pH and not to indirect action through food limitations.     

The benthic fauna of 41 acid sensitive headwater lakes in North Central Ontario

The benthic fauna of 41 nonhumic, soft water lakes situated north of lakes Superior and Huron were sampled during 1980. The pH range of the lakes sampled was 4.6 to 7.7. The benthic infauna displayed regional differences in abundance and composition, with large variation within each district. Total abundance, biomass, and number of taxa were not correlated with lake pH or alkalinity. The Chironomidae displayed a slight change in percent composition of the major species (p < 0.2) with lower pH. The Tanytarsini andChironomus salinarius group decreased, whileC. anthracinus group increased in relative abundance in those lakes with lower pH. Other factors appear to control the distribution of the various invertebrate orders, with depth and sediment nature being important variables.     

Pyro- and tripoly-phosphate contents of sediments

A method to determine pyrophosphate (PP) and tripolyphosphate (TPP) in sediments was developed. Sediment was extracted with 2% EDTA + 0.1 M NH₄F followed by a second extract of 2% EDTA + 1 N NaOH. Orthophosphate (OP), PP, and TPP were separated by anion exchange chromatography, the fractions collected, and P determined after extraction into isobutanol. The limit of detection of the method was 0.5 μg P g^?1 sediment. Fourteen sediments were tested and the highest TPP found was 1.8 μg P g^?1 sediment. Thirteen of the sediment samples contained less than 1 μg P g^?1 as TPP. Only three of the 14 samples contained more than 1 μg P g^?1 as PP. The highest level of PP (8.5 μg P g^?1) was found in sediment from an animal waste lagoon. Estimates of error and reproducibility were made from analysis of samples with added PP and TPP. The error for samples containing 36.9 μg P g^?1 as PP was ± 7.6, and for TPP at 12.3 μg P g^?1 the error was ± 3.3. The values for PP and TPP were underestimated by 6 and 36%, respectively.     

Partitioning characteristics of PAHs between sediment and water in a shallow lake

Goal, Scope and Background

Distribution of hydrophobic organic contaminants in abiotic compartments is essential for describing their transfer and fate in aquatic ecosystems. Taihu Lake is the third largest freshwater lake in China. Water quality of Taihu Lake has deteriorated greatly during the last decades and has threatened the water supply. The aim of the present study was to investigate the partitioning of polycyclic aromatic hydrocarbons (PAHs) among overlying water, suspended particulate matter (SPM), sediments, and pore water in Meiliang Bay, Taihu Lake and to provide useful information for the ecological engineering in this area.

Materials and Methods

Overlying water and surface sediment were sampled from six sites in Meiliang Bay, Taihu Lake, China. Within 72 h of sampling, sediments were centrifuged to obtain the pore water. Overlying water samples were filtered to separate dissolved and SPM samples. After extraction, samples were purified following a clean-up procedure. PAH fraction was obtained by elution with a mixture of hexane: DCM (7:3, V/V) and analyzed by GC/MS.

Results

PAHs concentrations in overlying water varied from 37.5 ng/L to 183.5 ng/L. Concentrations of PAHs in pore water were higher than those in overlying water. The total concentrations of 16 priority PAHs in sediments ranged from 2091.8 ng/g-dw to 4094.4 ng/g-dw. PAHs concentrations on SPM were decreased with suspended solid concentrations (SSC). Total PAHs concentrations on SPM varied in the range of 3369.6 ng/g-dw to 7531.1 ng/g-dw. The partition coefficients between sediment and overlying water (log K _oc) for PAHs with log K _ow<5 were positively correlated with their octanol-water partition coefficients (log K _ow) (n=39, r=0.79, p<0.0001). Partition coefficients between sediment and pore water (log K _oc′) for all PAHs were also significantly correlated with their log K _ow values (n=48, r=0.82, p<0.0001).

Discussion

In general, PAHs derived from combustion sources tend to bind strongly to soot particles in natural sediment. Consequentially, K _oc values observed in the natural environment could be orders of magnitude higher than those predicted by linear correlation relationships under laboratory conditions. In the present study, the ratio of log K _oc values to log K _ow values falls consistently above 1, indicating that the sediment soot carbon in the bay was more attractive for PAHs than n-octanol. The log K _oc′ was also higher than that predicted under laboratory conditions, suggesting that the measured pore water PAH concentrations were lower than those predicted. That is to say, not all the sediment PAHs can be available to partition rapidly into sediment pore waters. A variation in soot content is a possible reason. Furthermore, concentrations of PAHs on SPM were higher than those in sediments. The compositions of PAHs on SPM and in sediments were similar, indicating the importance of re-suspension process of sediments in the partitioning process of the shallow lake.

Conclusions

The results indicated the equilibrium partitioning model could be used to predict PAHs distribution in various phases of a shallow lake in the stagnation period, but re-suspension processes should be considered to modify the relationship between log K _ocs and log K _ows.

Recommendations and Perspectives

Concentration, particle size and composition of resuspended particles could affect the relationship between log K _ocs and log K _ows. Further work should be done under field conditions, especially where a steady thermodynamic equilibrium state could be assumed.

     

Effects of acid,aluminium and lime additions on fish and invertebrates in a chronically acidic welsh stream

A chronically acidic stream, mean pH 5.2, in upland mid-Wales was subjected to an induced episode of acidity, during which acid, Al and limestone were added at different points along the stream length. An upstream reference zone (A), an acid zone (B), an acid plus Al zone (C) and a downstream zone of Al at low pH with added limestone to increase pH (D) were created for a 24 hr period. Four species of fish and 10 species of invertebrates were exposed in each zone and response criteria measured included mortality, metal uptake, feeding and the ability of stressed animals to recover. Fish mortalities were greater in zones B and C than in zone A and were greatly reduced by the addition of lime in zone D. Overall mortality was low amongst the invertebrate species found in acid waters. Greatest mortalities were recorded for Gammarus pulex. G. pulex infected with the acanthocephalan parasite Pomphorhynchus laevis exhibited greater mortality than uninfected animals. The feeding rate of G. pulex was suppressed in all zones during the dosing period; uninfected G. pulex consumed more than infected animals, and the feeding rate of all gammarids increased post-dosing but not to the level of unexposed animals. Aluminium concentrations in fish gills increased with time. Invertebrate body burdens of Al were greatest in zone D, with significant increases over the dosing period for both G. pulex and Isoperla grammatica. No significant patterns were observed in the concentration of Ca, Na or K for either fish or invertebrates.     

Industrial impact in Northwestern Whatcom County,Washington

A field study designed to determine the nature and extent of environmental impact by an industrial complex was carried out during the period 1966–76. The industrial complex consists of two oil refineries, Mobil and Atlantic Richfield (ARCO), and an aluminium reduction plant, Intalco. The location is northwestern Whatcom County, Washington, U.S.A. The study consisted of critical examination of native, exotic, and cultivated plants in 75 sites; productivity analysis at two sites; plant community analysis at three sites; total-S analysis of leaves at 37 sites; and soil S analysis at 10 sites. The effect of SO₂ emission by Mobil and ARCO appeared to be negligible, except in regard to injury to lichens and bryophytes; however S accumulation was strongly correlated with distance from the refineries, wind pattern, and ambient air concentrations of SO₂. Hydrogen fluoride is an established pollutant from Intalco and is thought to have reacted synergistically with SO₂ to produce injury symptoms at S concentrations below reported injury threshold levels.     

Sediment transport below a small alpine reservoir desilted by controlled flushing: field assessment and one-dimensional numerical simulation

Purpose

Sediment transport and riverbed sedimentation were investigated in an alpine stream below a small hydropower reservoir desilted by a controlled sediment flushing (CSF) operation. The term “controlled” refers to the operational tasks implemented to mitigate the downstream environmental impact of the operation. The experimental dataset acquired before, during, and after the CSF was also used to carry out and calibrate a one-dimensional sediment transport model of the monitored event.

Materials and methods

The investigated reservoir is located in the central Italian Alps, and its original storage was 160,000 m³, about 30% filled by a mixture of sand and silt/clay before the CSF. Downstream sediment concentration was controlled by releasing clear water from upstream reservoirs and regulating the work of earth-moving equipment in the emptied reservoir. A 3.6-km-long reach with average slope of 0.015 was monitored: concentration and grain size of suspended sediment were measured during the CSF and the riverbed alteration was evaluated by volumetric sampling and measurements of the deposits’ thickness. Sedimentation and River Hydraulics—One Dimensional (SRH-1D) was used to simulate sediment transport during the monitored CSF. Model parameters were calibrated by comparing the computed and the observed amount of sediment deposited along the study reach.

Results and discussion

Sediment flushing was carried out in October 2010 for 3 days. Ca. 16,000 m³ of sediment were evacuated, representing approximately 30% silt/clay and 70% sand. 2.4 Mm³ of clear water was released to reduce sediment concentration and increase transport capacity downstream. About 3000 m³ of sand was deposited in the study reach after the CSF, with maximum height up to 0.2 m. Although the riverbed before the CSF was simply set as mono-granular, after calibrating the parameters, good agreement was achieved between the depositional pattern computed by SRH-1D and the one observed, both in terms of deposit thickness and grain size of deposited sediment. The sensitivity analysis revealed a major role of the parameters controlling bed mixing processes in affecting the simulated deposition after the CSF.

Conclusions

Sediment below 0.1 mm in diameter was not detected in river deposits after the flushing: the effects on river biota associated with substrate clogging by very fine sediment were therefore minimized. After proper calibration, 1-D sediment transport modeling can effectively support the planning of CSF operations: to minimize the downstream environmental effects, concurrently achieving acceptable flushing efficiency, the analyzed scenarios as well as the model outputs need to be carefully evaluated from a multidisciplinary perspective.

     

Annual dynamics of persistent organic pollutants in various aquatic matrices: a case study in the Morava River in Zlín district,Czech Republic

Purpose

A multi-compartment monitoring study was performed to characterize the effect of environmental variables, such as temperature and water flow as well as sediment characteristics, on the distribution and transport of persistent organic pollutants (POPs) in a dynamic river system during 1 year in an industrial region in central Europe.

Materials and methods

Waterborne polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) were assessed over a period of 1 year at five sampling sites in the Morava River in the Czech Republic. Contaminants were measured monthly in riverbed sediments, freshly deposited sediments, water samples and passive samplers.

Results and discussion

Sediments are the main carrier of POPs in the river. Distinguishable patterns of PAHs, OCPs and PCBs in sediment indicate that their origin is from distinct sources and different transport pathways. The PAHs were identified as the dominant contaminant group of compounds with a mean concentration in sediment of 5,900 μg kg^?1. Such concentrations are up to 10 times higher than in the Danube River, into which Morava drains. In contrast, mean concentrations of PCBs, hexachlorocyclohexanes (HCHs), dichlorodiphenyltrichloroethane and its breakdown products (DDTs) and hexachlorobenzene (HCB) of 6.0, 0.4, 4.2 and 6.0 μg kg¹, respectively, are similar to those in the Danube. With some exceptions, no significant difference in composition of surficial riverbed sediments and those collected using sediment traps was observed. Despite the presence of potential local pollutant sources, the differences in contaminant concentrations between sites in the region were in most cases not significant. Variations in POP concentrations in sediments are mainly induced by high flow events, whereas seasonal variability was not observed.

Conclusions

The changes in contaminant concentrations in Morava River sediments are induced by episodic high flow events that cause erosion of contaminant-containing particles and their deposition at suitable downstream sites.     

Characteristics of bacterial community in the water and surface sediment of the Yellow River,China, the largest turbid river in the world

Purpose

Few studies have described the bacterial community structures of turbid rivers. In this paper, the characteristics of the bacterial community in the water and surface sediment of the Yellow River, China, the largest turbid river in the world, were studied.

Materials and methods

Water and sediment samples were collected from six sites along the river. Bacterial community composition was determined using the 16S ribosomal RNA (rRNA) gene clone library technique. The relationship between environmental parameters and bacterial diversity was analyzed.

Results and discussion

A total of 1,131 gene sequences were obtained and clustered into 639 operational taxonomic units (at the 97 % identity level), with Proteobacteria as the predominant phylum. The Shannon index for water samples ranged from 3.39 to 4.40 and was generally higher than that in other rivers; this was probably due to the high suspended particulate sediment (SPS) concentration in the Yellow River, which can provide more habitats for both aerobic and anaerobic bacteria. Also, the bacterial diversity of the water samples was slightly higher than that of the surface sediment samples. The bacterial diversity of water increased along the river in the downstream direction, while there was no trend for the sediment. Redundancy analysis indicated that pH, dissolved organic carbon (DOC), and SPS were the main factors controlling the water bacterial community in the Yellow River, and pH, nitrate–nitrogen, and water content were the main factors for the surface sediment bacterial community.

Conclusions

This study indicated that the bacterial diversity of the Yellow River is generally higher than that in other rivers, suggesting that SPS plays an important role in regulating bacterial diversity and community structure in aquatic environments.     

Atmospheric hydrogen sulfide levels at the sulphur bay wildlife area,Lake Rotorua,New Zealand

At the Sulphur Bay Wildlife area on Lake Rotorua, shore and water birds are exposed to natural H₂S at concentrations of 125 to 3900 ppbV from continuous shore and lake sources. Nevertheless, 62 bird species, 45 native, have been recorded there. Regular residents include Red-Billed Gull, Dabchick Mallard Duck, Black Swan and Caspian Tern. Some, the Red Billed Gull and Little Black Shag, have initiated colonization within the past half-century. We suggest that exposure to H₂S at the levels reported here may be less of a biohazard than previously supposed.     

Determination of cerium in marine sediments

Marine sediments carry almost all the radioactive Ce that enters the ocean with the effluents released from the nuclear industry. The uptake of radioactive¹⁴⁴Ce by the sedentary organisms is influenced by the amount of stable Cc present in the sediment. A method has been described for the determination of stable Cc in the sediments, based on ion exchange separation and colorimetric measurement with Arsenazo I reagent. The effect of diverse cations on the recovery of Cc is discussed. Lanthanum, Y, Th and Zr which form colored complexes with Arsenazo I, do not interfere under the conditions of the experiment. The recovery of stable Ce ranges from 95 to 98% Using the method, the stable Ce content in some sediments from coastal Bombay was observed to range from 20 to 99 ppm. The same method with minor changes is described for the determination of radioactive Ce in the sediments and illustrated with the analysis of a sediment sample.     

Mössbauer studies of the speciation of tributyltin compounds in seawater and sediment samples

The antifoulant agents, bis-(tributyltin) oxide (TBTO), tributyltin acetate (TBTOAc) and tributyltin chloride (TBTCI) were mixed with various media. These media included distilled water, seawater, aerobic and anaerobic sediments. The Mossbauer spectra of the chloroform extracts of the distilled water and seawater mixed with these compounds were examined. The componds were mixed with aerobic and anaerobic sediments, and the Mossbauer spectra of the sediments were also examined. TBTO was converted to the hydroxide compound in all media except in anaerobic sediment where it was converted to an unidentified compound. TBTOAc and TBTCI were not changed by mixing with distilled water and aerobic sediment but were converted to the hydroxide compound in seawater and in anaerobic sediment.     

Research on the sedimentation and erosion problem of the Ergene River Basin in Western Turkey and precautions to control it

The objective of this study was to asses the rainfall-runoff-sedimentation relationship from directly measured data since 1972, to find out the effect of the present land use and soil cultivation techniques on the sediment yield, and to offer practical solutions to the problems in the Ergene River Basins located in the European Part of Turkey. The suspended sediment yield was calculated by multiplying the daily average discharged water by the average sediment concentration, while the eroded coarse sediment yield was computed using a regression equation developed by the Japanese Ministry of Construction. The relationship between the runoff and suspended sediment rates was explained exponentially as S = 1.99 Q _A ^1.62 (P > 0.01 and R ² = 0.846) (S is the suspended sediment rate in t d^?1, and Q _A is the average daily runoff rate in m³ s^?1). The suspended sediment rates of the Ergene Basin can then be predicted from the flow rate at any time of the year using this produced regression equation. According to the results, 70% of the basin’s soil (9534 km² and occupying 81.76% of the total area of the region) is under erosion hazard varying in intensity, namely, 25.3% light, 34.6% moderate, 8.6% strong, and 1.5% very strong. 47.09% of the average 604 mm precipitation falls in the critical period of October–January in terms of the sedimentation. The coarse and suspended sediment yield was 74.040 t km^?2 per year, which was well below the average for Turkey. However, it was 2 and 2.5 times larger than the average for Europe and Africa, respectively. Because 76.93% of the eroded land is in the 1rst, 2nd, and 3rd class, the severity of the sedimentation situation is proved. The causes of the high sediment yield were identified, and a series of precautions were suggested to minimize them.     

Geochemistry of aquatic and terrestrial sediments,precambrian shield of Southeastern Ontario

Lake water and sediment samples from approximately 2200 lakes and glacial sediment (sub-solum) samples from about 1800 sites were collected throughout a 38000 km² rectangular area extending from Georgian Bay east to the Ottawa and St. Lawrence Rivers, Ontario, Canada. Lake water alkalinity and pH patterns are similar to the distribution of carbonate components in glacial drift. Carbonate-rich drift derived from the Paleozoic limestone terrain on the northeast flank of the Precambrian Frontenac Arch has been dispersed in a southwestward direction across a variety of non-calcareous metasedimentary and igneous rocks of the Canadian Shield, providing a buffering capacity to lakes situated in granitic terrain. The distribution patterns of mobile trace and minor elements are influenced by geochemical processes associated with subaerial weathering, ground and surface water transport, and the geochemical environment within the lakes themselves. Although composition of the drift is generally reflected by lake geochemistry, these post depositional processes can cause significant variations between patterns derived from the two sample types. Anions and cations such as S0₄ , Cl^?, Na⁺, and F^? exhibit concentration patterns thought to reflect both anthropogenic inputs and natural variations due to differences in the geology. All regional geochemical patterns may show evidence of local enhancement caused by high concentrations of chemically distinctive minerals in drift or nearby bedrock.