Specific Alkalinity Research Articles

Leachate Experiments to Evaluate Weathering of Waste Rock for Backfill Aquifers in Restored Coal Mine Pits, Powder River Basin, USA

Restoration of open-pit mines may utilize waste rock for landscape reconstruction, which can include the construction of backfill aquifers. Weathering and contaminant transport may be different in backfill aquifers compared to the surrounding aquifer because of newly available mineral surfaces and transportable nano- to micro-scale particles generated during mining. Waste rock from the Cordero Rojo open-pit coal mine in the Powder River Basin was exposed to benchtop leachate experiments for 20 weeks at temperatures of 5 °C and 20 °C. Collected leachate was analyzed for Eh, pH, specific conductance, alkalinity, and cation and anion concentrations as unfiltered and 0.45-μm and 0.2-μm filtered concentrations. During the experiment, leachate Eh and pH substantially varied during the first 55 days, which corresponds to a period of high specific conductance (>1000 µS/cm) and alkalinity (>200 mg/L). Correspondingly, anion and cation concentrations were the largest during this early weathering stage, and the filter fractions indicated multiple forms of transported elements. After this early weathering stage, column leachate evolved towards a weathering equilibrium of neutral, oxidizing, and low solute conditions indicated by positive Eh values, pH near 7, and specific conductance <500 μS/cm. This evolution was reflected in the decline and stabilization or non-detection of metal(loid) concentrations reflective of a shift to primarily bulk aluminosilicate weathering when coal- and salt-associated elements, such as arsenic, cadmium, and selenium, were not detected or at minimal concentrations. Over the course of the experiment, the solute trend of certain elements indicated particular weathering processes—cadmium and nanoparticle transport, selenium and salt dissolution, and arsenic and pyrite oxidation. The mining of overburden formations and use of the waste rock for backfill aquifers as part of landscape reconstruction will create newly available mineral surfaces and nanoparticles that will weather to produce solute concentrations not typically found in groundwater associated with the original overburden.

Exploring the Potential of Aerated Concrete and Clay Bricks from Construction and Demolition Waste as Adsorbents for Pb(II) Removal from Aqueous Solutions

This study aimed to evaluate the potential of utilizing aerated concrete (AC) and clay bricks (CB) sourced from construction and demotion waste (CDW) as low-cost adsorbents for the removal of Pb2+ from aqueous solutions. The effects of various parameters, including particle size, solution pH, contact time, adsorbent dosage, and initial Pb2+ concentration, were analyzed through batch experiments. The results indicated that AC performed more efficiently in removing lead ions than CB under all the tested conditions. The highest removal efficiency of Pb2+ with AC was 99.0%, which was achieved at a pH of 5.0, contact time of 1 h, an adsorbent dosage of 5 g/L, and an initial Pb2+ concentration of 100 mg/L. The maximum adsorption capacities of AC and CB were 201.6 mg/g and 56.3 mg/g, respectively. The adsorption isotherm data of the adsorbents were successfully modeled using both the Langmuir and Freundlich models. The removal of lead ions from aqueous solutions by both adsorbents is primarily achieved through adsorption and microprecipitation. Compared to CB, AC exhibited superior performance, attributed to its larger specific surface area, pore volume, and alkalinity. The cost-effectiveness and availability of AC make it a promising candidate for treating of Pb-contaminated wastewater, providing a new way for resource utilization of CDW.

Do PFAS changes in landfill leachate treatment systems correlate with changes in physical chemical parameters?

Per- and polyfluoroalkyl substances (PFAS) have been found at relatively elevated concentrations in landfill leachates. Some landfill facilities treat physical-chemical parameters of their leachates using on-site leachate treatment systems before discharge. The objective of this study was to evaluate whether changes in physical-chemical parameters of leachate at on-site treatment systems (including bulk measurements, oxygen demanding components, and metals) were associated with concentration changes in PFAS. Leachates were evaluated at 15 on-site treatment facilities which included pond systems, aeration tanks, powdered activated carbon (PAC), sand filtration, reverse osmosis (RO) and combination treatment processes. Results show that most physical-chemical parameters and PFAS were significantly reduced in RO systems (over 90 %). For pond systems, statistically significant correlations (rs > 0.6, p < 0.05) were observed between ∑26PFAS changes and the changes in pH, alkalinity, ammonia, and some metals. Significant correlations were also found between ∑8PFAAs precursors changes and specific conductivity (SPC), pH, alkalinity, ammonia, and metals changes. For aeration tank systems, significant correlations (rs > 0.6, p < 0.05) were observed between ∑26PFAS changes and changes in total dissolved solids and zinc, and between the changes of ∑8PFAAs precursors and field pH. These correlations are believed to be associated with rainfall dilution and precipitation of calcium carbonate and other metals as leachate is introduced to the atmosphere.

Linking changes in sedimentary Cladocera assemblages to limnological variables in 67 Sudbury (Ontario, Canada) lakes reflecting various degrees of metal smelter impacts

Despite extensive records of chemical recovery, relatively little is known about recovery of aquatic biota in Sudbury (Ontario, Canada). Cladocera (Branchiopoda) are key components of lake food webs, and understanding spatial patterns in their assemblages may emphasize ecosystem recovery challenges. Paleolimnological techniques complement and provide long-term context to modern monitoring. Cladoceran remains from the surface sediments of 67 lakes across a gradient of smelter impacts were examined to determine which measured limnological factors most influenced assemblage composition. Lakes were divided into four categories by acidification histories and location: Acidified (pH &lt; 6) Urban, Non-urban Acidified, Acidified Killarney, and Reference (pH &gt; 6) lakes. Specific conductance, nutrients, alkalinity, and lake depth significantly structured assemblages. Most assemblages were dominated by generalist taxa. Relative abundances of Alona taxa varied strongly along alkalinity and pH gradients. Lakes with high metal concentrations were generally less diverse and dominated by generalist taxa, although metals often co-occurred with other stressors. Recovery targets could be affected by these chemical factors. These data provide useful information for future environmental inferences from cladocerans in metal smelting regions.

A Complicated Groundwater Flow System Supporting Ridge-and-Swale Wetlands in a Lake Michigan Strandplain

Beach ridges and wetland swales formed in embayments along Great Lakes shorelines during Holocene lake-level changes. Vegetation differences among swales suggested influence from differing groundwater flow systems. We characterized the hydrology across 79 ridge/swale wetlands in the Manistique/Thompson embayments of Lake Michigan using chemical and physical methods. Cross-sections were built from geologic data, and nested piezometers were installed across three ridges/swales where upwelling was noted. Stainless steel piezometers driven in 30 swales were sampled and water analyzed for specific conductance, alkalinity, and major ions. Surface water from 11 swales was analyzed. Water dominated by Ca-Mg-HCO3 was prevalent across the strandplain, with specific conductance generally less than 100 μS/cm. Conductivity, Ca, Mg, and HCO3 in groundwater were greater at identified groundwater discharges; where an amalgamated beach ridge forms a surficial groundwater divide; and swales nearer Lake Michigan that likely receive greatly mineralized water from a deeper aquifer. Repositioning of the shoreline as the embayments filled over the past 4700 years, coupled with isostatic rebound and changes in lake water levels, altered head differentials and changed the sources of discharge from local, intermediate, and deep flow systems over time. Extant plant communities are consistent with the groundwater dependence of these wetlands.

Freshwater runoff effects on the production of biogenic silicate and chlorophyll-a in western Patagonia archipelago (50–51°S)

Freshwater discharged from the continent to the sea plays an important role in the biogeochemistry and productivity of the coastal ocean. The continental drainage basin characteristics can be a key local factor determining the concentration, proportions and timing of bio-active freshwater solutes discharged into an estuary, and thus could play a “bottom up” role modulating the phytoplankton assemblage attributes. In a period from 2015 to 2017 we characterize the concentration of total alkalinity (AT) and silicic acid (DSi) in continental and estuarine surface waters at both limestone and silicates basins of the Madre de Dios archipelago (ca. 50–51°S and 75.5–75°W). Continental waters had high AT in limestone and low AT in silicate basins causing differences in the specific total alkalinity of estuarine waters. Similarly, while limestone continental water is characterized by very low DSi concentrations (3 ± 3 μM, n = 16) that dilute initial DSi concentrations of sub-Antarctic Surface Water (SAASW) at the mixing zone, continental water from silicate drainage basins (Patagonian Batholith; 53 ± 49 μM, n = 18) acts as a source of DSi to the estuary. Experimental SAASW dilution with two types of native continental water, one supplying high AT – low DSi and another supplying low AT – high DSi to the western central Patagonian Archipelago, resulted in phytoplankton assemblages with different characteristics. While “silicate-water” freshening of SAASW resulted in higher biogenic silicate (bSi) content, “limestone-water” freshening of SAASW resulted in higher levels chlorophyll a allocated in small cells-size range (0.45–2 μm). We suggest that the local variability in the suite of solutes delivered from continental runoff can significantly modulate phytoplankton communities attributes, especially in western Patagonian with interior estuarine waters characterized by extensive channels and fjords, together with extreme precipitation/runoff (>6 m y−1) and sharp contrasts in lithology.

Changes in the Status of Native Brook Trout on Laurel Hill, Southwestern Pennsylvania

To evaluate the status of native Salvelinus fontinalis (Brook Trout) on Pennsylvania's Laurel Hill, we sampled fish, assessed habitat, and documented water quality from 20 non-randomly selected headwater streams of northwest- and southeast-facing slopes. In late spring and early summer of 2011 and 2014–2016, we sampled fish communities and measured specific conductance (μS/cm), total alkalinity (mg/l as CaCO3), pH, and total dissolved aluminum (2011 and 2016). In addition, in 2015 we determined land-use patterns, riparian canopy, and substrate composition. Mean pH values among the streams recently assessed were significantly higher than historic values; however, all other water-quality parameters were similar. Native Brook Trout were present in all streams, and annual natural reproduction was evident in 90% of streams. Even though fish were present, we observed marked declines in total catch in both 0-age and adult trout; the overall reduction approached 60% when compared with those documented in 1983. We discuss possible causes for the observed declines, including acid deposition, introduction of nonnative/invasive species, water withdrawal, habitat fragmentation/alteration, predation, and climate change.

Bamboo- and pig-derived biochars reduce leaching losses of dibutyl phthalate, cadmium, and lead from co-contaminated soils

Biochar effect on the potential mobility of dibutyl phthalate (DBP), cadmium (Cd), and lead (Pb) in co-contaminated soils is not well investigated. A laboratory leaching study was conducted to evaluate the effect of biochars derived from bamboo (BB) and pig (PB) on the leachability of DBP, Cd, and Pb through soil columns packed with two soils with low or high organic carbon content (LOC; 0.35% C: HOC; 2.24% C) and spiked with DBP, Cd, and Pb. Application of PB to the LOC soil significantly (P < 0.05) reduced the leaching loss by up to 88% for DBP, 38% for Cd, and 71% for Pb, whereas its impact was insignificant in the HOC soil. The higher efficacy of PB in reducing the leaching of DBP, Cd, and Pb in the LOC soil than that of BB might be related to PB's higher specific surface area, surface alkalinity, pH, and mineral contents compared to those of BB. Co-contamination of Cd and Pb enhanced leaching of DBP in the LOC soil treated with PB, possibly by competition for the sorption sites. Leaching of DBP, Cd, and Pb were significantly (P < 0.05) higher in the LOC soil than in the HOC soil. This study revealed that the effectiveness of biochars was dependent on the soil organic carbon content. Application of PB to the LOC soil was effective in reducing the leaching risk of DBP, Cd, and Pb.

Water quality of surface runoff and lint yield in cotton under furrow irrigation in Northeast Arkansas

Use of furrow irrigation in row crop production is a common practice through much of the Midsouth US and yet, nutrients can be transported off-site through surface runoff. A field study with cotton (Gossypium hirsutum, L.) was conducted to understand the impact of furrow tillage practices and nitrogen (N) fertilizer placement on characteristics of runoff water quality during the growing season. The experiment was designed as a randomized complete block design with conventional (CT) and conservation furrow tillage (FT) in combination with either urea (URN) broadcast or 32% urea ammonium nitrate (UAN) injected, each applied at 101kgNha−1. Concentrations of ammonium (NH4-N), nitrate (NO3-N), nitrite (NO2-N), and dissolved phosphorus (P) in irrigation runoff water and lint yields were measured in all treatments. The intensity and chemical form of nutrient losses were primarily controlled by water runoff volume and agronomic practice. Across tillage and fertilizer N treatments, median N concentrations in the runoff were <0.3mgNL−1, with NO3-N being relatively the highest among N forms. Concentrations of runoff dissolved P were <0.05mgPL−1 and were affected by volume of runoff water. Water pH, specific electrical conductivity, alkalinity and hardness were within levels that common to local irrigation water and less likely to impair pollution in waterways. Lint yields averaged 1111kgha−1 and were higher (P-value=0.03) in FT compared to CT treatments. Runoff volumes across irrigation events were greater (P-value=0.02) in CT than FT treatments, which increased NO3-N mass loads in CT treatments (394gNO3-Nha−1season−1). Nitrate-N concentrations in CT treatments were still low and pose little threat to N contaminations in waterways. The findings support the adoption of conservation practices for furrow tillage and N fertilizer placement that can reduce nutrient runoff losses in furrow irrigation systems.

Water chemistry preferences of five nonnative aquatic macrophyte species in Connecticut: a preliminary risk assessment tool

Our analysis of 156 lakes and 5 nonnative aquatic macrophyte species suggest that 4 water chemistry variables can be used to assess the risk associated with species invasion in Connecticut lakes. Our analysis showed that water chemistry and longitude explained a significant amount of the total data variance (33%). Additionally, individual species logistic regressions suggest that these species’ distributions were determined by the specific conductance and pH of the water body. Lakes were then placed into one of the following groups: (1) Cabomba caroliniana/ Myriophyllum heterophyllum (CM), (2) Myriophyllum spicatum/Najas minor/Potamogeton crispus (MNP), (3) Mixed (Mixed), or (4) No Invasive (NI). Multivariate analysis of variance suggests that water chemistry of the groups CM and MNP differed significantly (p < 0.001), and the variables that contributed to this difference were specific conductance (F = 22.16), alkalinity (F = 19.40), and pH (F = 18.61). The Mixed and No Invasive groups were not significantly different. Discriminant function analysis was used as a final analytical tool to determine the risk of NI group lakes developing populations of our nonnative species. The results suggest that the 4 abiotic variables could predict the identity of the CM and MNP groups with a high degree of certainty (i.e., 79 and 71% correct, respectively). When the NI group was included in the discriminant analysis, 34% of these lakes were grouped with CM and 14% with MNP. The remaining 52% of NI lakes had water chemistry parameters capable of supporting all species examined in this study. From these findings, water chemistry risk assessment ranges were developed for these common nonnative species in Connecticut.

Low Temperature Effects on the Nitrification in a Nitrogen Removal Fixed Biofilm Process Packed with SAC Media

A fixed biofilm reactor system composed of anaerobic, anoxic(1), anoxic(2), aerobic(1) and aerobic(2) reactor was packed with synthetic activated ceramic (SAC) media and adopted to reduce the inhibition effect of low temperature on nitrification activities. The changes of nitrification activity at different wastewater temperature were investigated through the evaluation of temperature coefficient, volatile attached solid (VAS), specific nitrification rate and alkalinity consumption. Operating temperature was varied from 20 to . In this biofilm system, the specific nitrification rates of , and were 0.972, 0.859 and 0.613 when the specific nitrification rate of was assumed to 1.00. Moreover the nitrification activity was also observed at which is lower temperature than the critical temperature condition for the microorganism of activated sludge system. The specific amount of volatile attached solid (VAS) on media was maintained the range of 13.6-12.5 mg VAS/g media at . As the temperature was downed to , VAS was rapidly decreased to 10.9 mg VAS/g media and effluent suspended solids was increased from 3.2 mg/L to 12.0 mg/L due to the detachment of microorganism from SAC media. And alkalinity consumption was lower than theoretical value with 5.23 mg as /mg -N removal at . Temperature coefficient () of nitrification rate () was 1.033. Therefore, this fixed film nitrogen removal process showed superior stability for low temperature condition than conventional suspended growth process.

Long-term trends of Great Lakes major ion chemistry

Data from U.S. and Canadian federal monitoring programs are compiled to assess long-term trends of major ions in each of the Laurentian Great Lakes. Time series are developed for the primary cations and anions as well as for specific conductance and alkalinity. When combined with historical estimates, these modern datasets provide a 150-year overview of each lake's chemical makeup. Because of their long residence times, lakes Superior, Michigan and Huron exhibit persistent increases in most ions. For lakes Erie and Ontario, several ions (chloride, sodium, calcium and sulfate), as well as specific conductance, reached peak levels between 1965 and 1975, but then began to decline. The decreases are attributable to different mechanisms: industrial point discharge reductions (sodium, chloride), atmospheric loading declines (sulfate), and the introduction of exotic dreissenid mussels (calcium). Recent data indicate that these ions are now increasing again (chloride, sodium) or have leveled off (calcium, sulfate). The results establish how much the chemical makeup of the Great Lakes has changed due to anthropogenic influences, and underscore the importance of long-term, systematic, water-quality monitoring.

Using porous ceramic media in the upflow packed-bed reactor (UPBR) system for nitrogen removal via autotrophic nitrification and denitrification

In this study, the feasibility of an innovative upflow packed-bed reactor (UPBR) system using porous sulfur and lime ceramic media (CERAMED-L and CERAMED-SL) to remove nitrogen for wastewater treatment was evaluated. The specific lime dissolution rates for CERAMEDs in the UPBRs show an inverse proportion to pH and resulted in 2.32 g as CaCO3 kg−1 CERAMED-L d−1 and 1.64 g as CaCO3 kg−1 CERAMED-SL d−1 at a pH 6.7. The calculated specific nitrification rate resulted 1.73–2.29 kg NH4 +-N m−3 CERAMED-L d−1, with a F/M ratio in the range 0.08–0.31 g NH4 +-N g−1 VS d−1. The alkalinity shortage in the feed solution seemed to be overcome by supplying specific alkalinity of 3.88 kg as CaCO3 m−3 CERAMED-L d−1 through the dissolution of lime from CERAMED-L. Autotrophic denitrification efficiencies were in the range of 83–96% during the test period, and the average specific denitrification rates of 0.97–1.92 kg NO3 −N m−3 CERAMED-SL d−1 and 0.19–0.36 g NO3 −-N g−1 VS d−1 were obtained.

Anion exchange pretreatment for the removal of natural organic matter from humic rich water

The treatment of humic rich water using anion exchange, coagulation and PAC-adsorption was studied, both independently and in sequence in that order. The commercial aluminium-based coagulant PAX-16, powdered activated carbon W35 and the magnetic ion exchange resin (MIEX®) were used in the study. The source of humic substances was natural water (25.0 g C/m3 as DOC) flowing out from the Great Batorow Peat-Bog (Lower Silesia, Poland). In addition to DOC, color, UV254 absorbance, specific UV absorbance (SUVA254), turbidity, pH and alkalinity were also analyzed. Regardless of the applied technology, in the phase of raw water treatment extraordinary solutions were necessary to treat the humic rich water – a high coagulant (13.1 g Al/m3) or PAC (&amp;gt;200 mg/dm3) dose or a low bed volume (200 BVs) in the case of anion exchange. MIEX®DOC pretreatment had a very positive influence on the course and effects of coagulation resulting in a higher coagulant efficiency for removing organic compounds. In this respect, MIEX®DOC pretreatment allowed the application of a required coagulant dose four times lower compared to the coagulation of raw water. In testing the sequence of processes (MIEX®DOC – coagulation – PAC-adsorption), coagulation was the main process responsible for reducing the SUVA254 value. The improvement in water quality after PAC-adsorption was not significant, although the process removed DOC fractions that could not be removed by coagulation. Each of the applied methods played a role in the treatment of humic rich water and the nearly complete removal of NOM was achieved (in the sequence of processes) under relatively rational operating conditions for the treatment techniques.

A graphical screening method for assessing stream water quality using specific conductivity and alkalinity data

In areas of varying geology, it is difficult to infer water quality from specific conductance or electrical conductivity (EC) data without an understanding of the expected range of EC values based on local bedrock composition. This paper describes a user-friendly graphical screening method that addresses this issue by plotting the EC against concurrent alkalinity data, which correlates well with the presence of carbonate bedrock under natural conditions, and thus serves as an index of bedrock type. The upper limit of EC vs. alkalinity expected in a stream is determined using regional groundwater quality data, based on the assumption that stream chemistry reflects groundwater under baseflow conditions. Stream samples with EC/alkalinity values that consistently plot above this limit are considered impacted by anthropogenic sources. The effect of dilution and runoff on the EC vs. alkalinity plot of stream samples is considered using a simple baseflow/storm runoff-mixing model. The graphical method's utility as a screening tool is demonstrated by application to stream chemistry data from watersheds of southeastern Pennsylvania and northwestern New Jersey in several distinct geologic settings; however the method is general and widely applicable to watersheds in humid temperate regions. Its use is intended for watershed stewards of both professional and nonprofessional qualification.

Further observations on the scaled Chrysophycean and Synurophycean flora of the Ocala National Forest, Florida, U.S.A.

The distributions of silica‐scaled chrysophytes in 30 freshwater ponds located in the Ocala National Forest, Florida, U.S.A., relative to chemical gradients are described. Phytoplankton, periphyton, and surface sediments from each of the 30 sites were collected in March of 2000 and later analyzed extensively with both scanning electron microscopy (SEM) and light microscopy (LM) for scaled chrysophytes. In addition, water samples were used to measure a suite of chemical characteristics, including specific conductance, pH, alkalinity, total phosphorus, total nitrogen, chlorophyll‐a, chloride, sulfate and base cation concentrations. Overall, waterbodies included in this study are oligotrophic, dilute, poorly buffered and low in pH. Including six previously described species which are largely known only from the Ocala National Forest, we have identified forty‐nine taxa of silica‐scaled Chry‐sophyceae and Synurophyceae, 23 of which were present in 5 or more waterbodies, indicating that lakes in this region are quite diverse and abundant in scaled chrysophytes. The most important species included Synura petersenii, S. echinulata and one recently reported new species from this region, Mallomonas wujekii, which was found in 73% of the lakes in this survey. The number of taxa found per lake ranged from 2 to 23 and observations include new records of several rarely reported species. Although the flora includes species commonly found in more northern regions, it also includes a group of taxa that appear to be endemic to the region and others commonly found in more tropical regions. Lastly, a new form found in ten ponds, Mallomonas transsylvanica f. curvata, is described.

Chemistry of Selected High-Elevation Lakes in Seven National Parks in the Western United States

A chemical survey of 69 high-altitude lakes in seven national parks in the western United States was conducted during the fallof 1999; the lakes were previously sampled during the fall of 1985, as part of the Western Lake Survey. Lakes in parks in the Sierra/southern Cascades (Lassen Volcanic, Yosemite, Sequoia/Kings Canyon National Parks) and in the southern RockyMountains (Rocky Mountain National Park) were very dilute; medianspecific conductance ranged from 4.4 to 12.2 μS cm-1 andmedian alkalinity concentrations ranged from 32.2 to 72.9 μeqL-1. Specific conductances and alkalinity concentrations were substantially higher in lakes in the central and northernRocky Mountains parks (Grand Teton, Yellowstone, and GlacierNational Parks), probably due to the prevalence of more reactivebedrock types. Regional patterns in lake concentrations of NO3 and SO4 were similar to regional patterns in NO3 and SO4 concentrations in precipitation, suggestingthat the lakes are showing a response to atmospheric deposition.Concentrations of NO3 were particularly high in Rocky Mountain National Park, where some ecosystems appear to be undergoing nitrogen saturation.

Chemical speciation of copper and zinc in surface waters of the western Black Sea

The chemical speciation of Cu and Zn was investigated by voltammetric titration methods in the surface waters (∼10 m) of the western Black Sea during an Istanbul–Sevastopol cruise conducted in November 1998. Supporting parameters (temperature (T), salinity (S), pH, alkalinity (Alk), suspended particulate matter (SPM) and dissolved and particulate 234Th) were obtained in order to distinguish hydrographic features against involvement of the metals in biogeochemical processes. In the Turkish continental slope region, the cruise track intersected a narrow vein of colder water originating on the western shelf. The core of this cold water vein was characterised by a relatively low salinity, higher specific alkalinity and higher metal (especially Cu) and metal-binding ligand concentrations. A very large portion of Cu (93–99.8%) and Zn (82–97%) was organically complexed. The degree of complexation was highest in shelf waters and lowest in the central gyre. Titration data for Cu were modelled by two classes of organic binding ligands characterised by (CL1=3–12 nM, log K1′=13.1–13.9) and (CL2=20–70 nM, log K2′=9.4–11.2). These ligands occurred mainly in the ‘dissolved’ phase, as defined by 0.4-μm filtration. The stronger Cu-binding ligand seemed to be produced in situ in response to Cu concentration, whereas the weaker Cu-binding ligand appeared to be derived from terrestrial sources and/or reducing shelf sediments. Titration results for Zn were generally represented by one class of ligands (CL1=8–23 nM, log K1′=9.4–10.2), which were almost uniformly distributed between the ‘dissolved’ (78±8%) and the particulate phase (22±8%). The concentration of these strong Zn-binding ligands showed a very good correlation with SPM (r2=0.64), which improved when the dissolved ligands alone were considered (r2=0.78). It is hypothesised that these ligands were produced in situ by the bacterial breakdown of particulate organic matter.

Thermal and Chemical Properties of Waldo Lake, Oregon

ABSTRACT Thermal and chemical profiles were obtained periodically in ultraoligotrophic Waldo Lake, Oregon during years 1986 through 1999. Profiling was done on a seasonal basis between May and October. During this period the lake becomes thermally well-stratified. Epilimnetic temperatures peak in August, then rapidly diminish in response to decreasing solar radiation. By October, the lake nears autumnal turnover. During winter, the lake freezes over. The lake features an orthograde oxygen profile, and is well-oxygenated to all depths. The lake is highly dilute, as indicated by extremely low values for specific conductance (2.9–5.2 μmhos cm−1) and alkalinity (0.39–0.71 mg·L−1 as HCO3). pH readings were nearly all less than 7.0. Inorganic phosphorus and nitrogen concentrations were mostly less than the minimum detection limit of 1.0 μg·L−1. Dissolved silica concentrations ranged between 0.12 and 0.34 mg·L−1. TDS concentrations averaged 4.04 mg·L−1, with roughly 10% of all test results reported as 0.000 mg·L−1. The cause of the lake's extreme dilution is uncertain, but a major contributing factor may be the fact that the lake is fed entirely by direct precipitation and runoff, with no rivers or permanent streams entering the lake.

Toxicity of total dissolved solids associated with two mine effluents to chironomid larvae and early life stages of rainbow trout

AbstractAsessment of total dissolved solids (TDS) represents anintegrated measure of the concentrations of common ions (e.g., sodium, potassium, calcium, magnesium, chloride, sulfate, and bicarbonate) in freshwaters. Toxicity related to these ions is due to the specific combination and concentration of ions and is not predictable from TDS concentrations. Short‐term chronic toxicity tests were conducted with larval chironomids and trout (eggs and swim‐up fry) to assess their TDS tolerance relative to effluents from two Alaskan mines. Both effluents are characterized by high TDS content but differ with respect to concentrations of specific ions and alkalinity. The toxicity tests were conducted with synthetic effluents formulated to match the ionic composition of each mine discharge. No toxicity was observed at &gt;2,000 mg of TDS/L with embryos or developing fry, but chironomids exhibited effects above 1,100 mg of TDS/L. These tests, together with information on the health of field populations (fish and benthic invertebrates), are appropriate and relevant for determining site‐specific whole effluent TDS concentrations.