Variations In Surface Water Chemistry Research Articles

Models for the acute and chronic aqueous toxicity of vanadium to Daphnia pulex under a range of surface water chemistry conditions

Alberta's oil sands petroleum coke (PC) generation has in recent years surpassed 10 million tonnes. Petroleum coke has been proposed as an industrial-scale sorbent to reduce concentrations of organic chemicals in oil sands process-affected water (OSPW). However, PC contains up to 1000 mg of vanadium (V) per kg of PC, and during the treatment it leaches from coke reaching levels of up to 7 mg/L in “treated” OSPW. Little information is available on how common water quality variables affect the toxicity of V to aquatic organisms. Here descriptive relationships are presented to describe how site-specific surface water characteristics representative of the Alberta oil sands region influence the toxicity of V to Daphnia pulex. Results revealed that when D. pulex was exposed to an increase in pH, a threshold relationship was found where acute V toxicity increased from a lethal median concentration (LC50) of 1.7 to 1.2 mg V/L between pH 6 and 7 and then levelled off at around 1 mg V/L. When alkalinity (from 75 to 541 mg/L as CaCO3) and sulphate (from 54 to 394 mg/L) increased, the acute toxicity of V decreased slightly with LC50s changing from 0.6 to 1.6, and from 0.9 to 1.4, respectively. When the length of V exposure was extended (from 2 to 21 d), only an increase of sulphate from 135 to 480 mg/L caused a slight increase in V toxicity from a LC50 of 0.6 to 0.4 mg V/L, the opposite trend seen in the acute exposures. In addition, the influence of two OSPW representative mixtures of increasing sodium and sulphate, and increasing alkalinity and sulphate on V acute toxicity to D. pulex were evaluated; only the mixture of increasing sodium (from 18 to 536 mg/L) and sulphate (from 55 to 242 mg/L) caused a slight decrease in V acute toxicity (LC50 1.0–2.1 mg V/L). Evidence is presented that variations in surface water chemistry can affect V toxicity to daphnids, although only to a small degree (i.e. within a maximum factor of 2 in all cases evaluated here). These relationships should be considered when creating new water quality guidelines or local benchmarks for V.

Hydrochemical characterisation of water quality in the Sarcheshmeh copper complex, SE Iran

Hydrochemical investigations were conducted to identify variations in surface water chemistry in different parts of the Sarcheshmeh copper complex. Twenty-three water samples from mine drainage, stream water, processing water of the concentrator plant and tailings dam water were collected to understand processes that control the elements’ mobility. Changes in trace metal concentrations and variation of major ions show two distinct water types: (a) neutral mine drainage (NMD) associated with the Sarcheshmeh mine waters containing lower trace metal, SO42− concentrations and neutral pH values, and (b) acid mine drainage (AMD) with waters from tailings impoundments and waste rock dumps corresponding to higher trace metals (Fe, Cu, Zn, Mo) and major anions (SO42− and Cl−) than the first type with typically acidic pH contents. As a result of Cu–Mo sulphides flotation process under alkaline conditions, high pH values, high Mo concentration and low contamination loads of Al, Mn, Fe, Cu and Cd were observed in reject waters from the concentrator plant. Sulphide oxidation (especially pyrite), dissolution–precipitation of the secondary minerals and discharge of the reject waters from concentrator plant were some of the most important factors that influence water quality at the tailings impoundments. The results of PHREEQC speciation and solubility modelling indicated supersaturation of the waters in the tailings impoundments with respect to hydronium jarosite, schwertmannite and gypsum.

Seasonal variations in surface water chemistry at disturbed and pristine peatland sites in the Flow Country of northern Scotland

Weekly monitoring of surface water chemistry took place over a one-year period in a small boggy sub-catchment of the River Thurso, northern Scotland. Monitoring started 6months after the felling to waste of plantation conifers. The chemistry of ground surface waters was monitored at four bog sites situated in former forestry plots as well as one control site situated in an intact bog. The chemistry of the receiving stream (Sleach Water) was monitored at seven points along a 2km stretch.Dissolved organic carbon and metals were very significantly affected by seasonal factors. On land, seasonal variations accounted for between 35% (Al) and 80% (Fe) of the total variance in the data at the intact bog site, with similar seasonal effects observed at the impacted sites. The amplitude of the seasonal signal was generally much higher at the impacted sites than at the control site.Except for dissolved Al and Mn, the chemical composition of the stream was only marginally influenced by surface runoff from the felled plantation despite evidence of intense seasonal mobilisation of e.g. DOC, K or Fe at or near the ground surface within the felled plots. This was attributed to the presence of a buffer zone between the plantation and the stream. On the other hand, surface inputs from former forestry plots caused measurable increases in stream water [Al] and [Mn]. The likely sources of Al and Mn were the disturbance of the mineral soil that had taken place some 20years previously as a result of forestry ground preparation and the leaching from the recently felled conifer material, respectively. Such inputs occurred in late autumn or winter for Al and in summer for Mn, thus intensifying their natural seasonal patterns in this peat draining stream.

Spatial and Seasonal Variability in Surface Water Chemistry in the Okavango Delta, Botswana: A Multivariate Approach

The annual flood pulse in the Okavango Delta (Botswana), has a major influence on water chemistry and habitat. We explore spatial and temporal patterns in a suite of chemical variables, analysed from 98 sample points, across four regions, taken at different stages of the flood cycle. The major pattern in water chemistry is characterised by an increasing gradient in ionic concentration from deep-water sites in the Panhandle to more shallow, distal regions to the south. Concentrations of cations, anions, dissolved organic carbon, and SiO2 are significantly higher in the seasonally inundated floodplains than in permanently flooded regions. Several variables (including Na and total nitrogen) significantly increase from low flood to high flood, while others (including HCO3, SiO2, and Cl) increase in concentration, initially between low flood and flood expansion, before declining at maximum flood extent. Redundancy analysis (RDA) revealed that hydrological variables (water depth, flow velocity, flood frequency, and hydroperiod class) significantly explain 17% variation in surface water chemistry. Predictions of increasing flood volume in the near future may result in a decline in alkalinity and dilution of DOC. Our study provides an important baseline from which to monitor future change in the Delta.

Atmospheric pollution histories of three Cumbrian surface waters

1. The CHemistry of the Uplands Model (CHUM), driven by measured and estimated atmospheric deposition, was used to simulate the chemical compositions of three upland Lake District surface waters, Devoke Water (DW), Levers Water (LW) and Mosedale Beck (MB) over several hundred years. 2. “Natural acidification” combined with human activities, notably forest clearance, was assumed to have brought about chemically stable acid moorlands by the period 1000–1500 A.D. Deposition of sulphur, nitrogen, chlorine and heavy metals, released into the atmosphere by coal-burning and industrial processes, then took place, gradually increasing to maximum levels in the late 20th century. 3. Surface water concentrations of chloride are consistent with depositional inputs, whereas the transfer of atmospherically deposited sulphur to the surface waters is delayed by temporary retention processes within the catchment. Over the last 40 years, concentrations of pollutant (non-marine) sulphate in the surface waters declined to one-third of their maximum levels. Atmospherically deposited pollutant N continues to accumulate in catchment soils, although a significant fraction appears in surface waters as nitrate. Annual average surface water bicarbonate concentrations were 20 - 60 µmol L-1 in the pristine past, fell nearly to zero in all three waters when acidification was most intense, but now are increasing. 4. Combined data from several Lake District upland waters suggest substantial recent increases in concentrations of dissolved organic carbon (DOC). If this can be attributed to acidification reversal, a corresponding decline in DOC concentrations would have occurred as acidification intensified, and pristine surface waters would have been comparatively rich in DOC. 5. Major cationic elements enter the soil-water system in deposition (H+, Na, Mg, K, Ca), from organic matter decomposition (H+), or by chemical weathering (Mg, Al, Ca), and are much affected by sorption to soil organic matter (SOM). The surface soils of all three catchments are acid (current pH ~ 4.5) and so variations in surface water chemistry among sites reflect differences in mineral dissolution rates deeper in the soil-rock profile. The simulations indicate pH values of 6.9, 6.1 and 6.4 for DW, LW and MB respectively in the period up to 1800, followed by declines to minima of c. 6.0, 4.7 and 5.0 in around 1980, then acidification reversal in agreement with observations. 6. The transfer of atmospherically deposited heavy metals to surface waters depends upon their sorption by SOM. Nickel, zinc and cadmium adsorb relatively weakly and therefore are quite readily leached, and sensitive to changes in acidification status. The higher affinities of organic matter to Cu and Pb promote retention and these two metals are continuing to accumulate in soil, despite major declines in deposition over the past several decades. 7. The WHAM-FTOX model was used to estimate the maximum number of Ephemeroptera, Plecoptera and Trichoptera species in MB through time, as influenced by chemical variability. The maximum number is estimated to have fallen from 14-15 under pristine conditions to 9-10 when acidification was greatest and a modest recovery to 10-11 species since then.

Regional variations in water quality and relationships to soil and bedrock weathering in the southern Sacramento Valley, California, USA

Regional patterns in ground- and surface-water chemistry of the southern Sacramento Valley in California were evaluated using publicly available geochemical data from the US Geological Survey’s National Water Information System (NWIS). Within the boundaries of the study area, more than 2300 ground-water analyses and more than 20,000 surface-water analyses were available. Ground-waters from the west side of the Sacramento Valley contain greater concentrations of Na, Ca, Mg, B, Cl and SO 4 , while the east-side ground-waters contain greater concentrations of silica and K. These differences result from variations in surface-water chemistry as well as from chemical reactions between water and aquifer materials. Sediments that fill the Sacramento Valley were derived from highlands to the west (the Coast Ranges) and east (the Sierra Nevada Mountains), the former having an oceanic provenance and the latter continental. These geologic differences are at least in part responsible for the observed patterns in ground-water chemistry. Thermal springs that are common along the west side of the Sacramento Valley appear to have an effect on surface-water chemistry, which in turn may affect the ground-water chemistry.

Temporal and spatial variation in quality of hyporheic water in one unregulated and two regulated boreal rivers

AbstractThis study describes the temporal and spatial variations in hyporheic water quality in three boreal rivers, the River Tobyälven, an unregulated river, the river Mangälven, a regulated river with a minimum discharge requirement and the river Järperudsälven, a regulated river without any minimum discharge requirements. A total of 43 permanent piezometers were used to measure dissolved oxygen (DO), temperature, electrical conductivity, pH, NO and NH in the hyporheic water at 150 mm and 300 mm depth, at monthly intervals from October 2001 to October 2002. Another seven piezometers were installed in brown trout redds and monitored during the incubation period, from December 2001 to April 2002. In the river Tobyälven, temporal patterns in hyporheic water chemistry correlated to variations in surface water chemistry and discharge. In the river Järperudsälven, the hyporheic water chemistry did not correlate to discharge or surface water chemistry. In the river Mangälven, the water chemistry was dominated by releases from a large upstream lake, and there were weak correlations between surface water chemistry and hyporheic water chemistry at some sites. The incubation conditions for brown trout eggs were most favourable in the unregulated river, characterized by high DO levels that remained high throughout the incubation period. In the river Järperudsälven the DO levels were variable during spawning, and then gradually declined to critically low levels during incubation, whereas in the river Mangälven the DO conditions were intermediate and stable. Thus we observed a stronger coupling between surface water conditions and hyporheic conditions, i.e. vertical connectivity, in the unregulated river than in the regulated river with minimum flow requirements, which in turn was stronger than in the river without minimum flow requirements. Copyright © 2007 John Wiley & Sons, Ltd.

Strategies for emission controls to mitigate snowmelt acidification

Elevated atmospheric deposition of strong acids contributes to short‐term/seasonal acidification of surface waters draining sensitive northern forests of North America and Europe during high flow. Reducing atmospheric deposition of NO3− and/or SO42−, therefore, could improve the health of aquatic ecosystems by mitigating episodic acidification. We used an integrated biogeochemical model (PnET‐BGC) to simulate the effects of acidic deposition on seasonal variations in surface water chemistry, and to evaluate emission control scenarios to decrease acidification during snowmelt. Model calculations suggest that historical long‐term inputs of acidic deposition have altered the seasonal patterns in surface water chemistry. Although short‐term increases in NO3− coincide with snowmelt acidification, model simulations indicate reductions in SO42− deposition result in larger benefits than an equivalent reduction in NO3− deposition. Year‐around reductions in NO3− deposition are also more beneficial to the acid‐base status of stream water than summer‐only reductions.

A two‐layer model to simulate variations in surface water chemistry draining a northern forest watershed

Seasonal patterns are evident in surface water chemistry draining forested headwaters in the northeastern United States. This variation in surface water chemistry is largely driven by seasonal fluctuations in hydrologic flow paths and biological activity. Especially during spring snowmelt, high‐flow conditions are characterized by high concentrations of NO3‒, naturally occurring organic anions and aluminum species, and depression in surface water pH and acid neutralizing capacity (ANC). Under extreme conditions, decreases in pH and ANC and increases in aluminum can have adverse effects on aquatic biota. As a result, there is a critical need to be able to simulate seasonal variations in surface water acid‐base chemistry. Previously, a single soil layer biogeochemical model (PnET‐BGC) was found to be inadequate to simulate seasonal variations in stream chemistry draining acid‐sensitive forest watersheds. In order to better simulate the seasonal variations in the acid‐base chemistry of surface waters, a two‐layer model (PnET‐BGC2) was formulated and applied to a northern forest ecosystem. End‐member mixing analysis was used to better understand hydrologic flow paths contributing to temporal patterns in stream chemistry and to parameterize the model. The resulting two‐layer model is generally able to reproduce the seasonal variations in surface water runoff, concentrations of base cations, SO42‒, NO3‒, pH, and ANC.

Chemical Variation and Catchment Characteristics in High Altitude Lochs in Scotland, U.K.

Previous research has established clear relationshipsbetween the chemical composition of surface waters andthe nature of their contributing catchments. Theserelationships are particularly strong when broadenvironmental gradients are considered. However, forfreshwaters at higher altitudes, some of the catchmentprocesses that mediate chemical composition are lessinfluential than those at lower altitudes. The waterchemistry of 85 upland lochs in Scotland, U.K. is examinedto assess differences in chemical composition along arelatively short altitude gradient. Principal componentsanalysis identifies the main gradients of variationwithin the dataset. A series of digital datasets is usedto characterise the catchments according to a range ofattributes including soils and landcover. Multivariatestatistical analysis is undertaken to examine the extentto which the catchment attributes can explain variationin surface water chemistry in upland systems. Theseempirical relationships may be used in the development ofregionalisation procedures, which will allow upscaling ofknowledge from individual sites to regions.

AN OVERVIEW OF FACTORS THAT INFLUENCE THE DEVELOPMENT OF CANADIAN PEATLANDS

AbstractCanadian peatlands can be classified into ombrotrophic bogs and minerotrophic fens, the latter subdivided into poor, moderate-rich, and extreme-rich fens, each with distinctive indicator species, acidity, alkalinity, and base cation content. If hydrology is considered the most important factor in peatland classification then the primary division must be between ombrotrophic bogs and minerotrophic fens; however both chemical and vegetational differences strongly indicate that the primary division of peatlands should be between acidic, Sphagnum-dominated bogs and poor fens on the one hand, and alkaline, brown-moss-dominated rich fens on the other. Although some metals such as sulphur and aluminum also vary along this gradient, nutrient contents of the surface waters do not. Bogs and fens are oligotrophic to mesotrophic wetlands that should be distinguished from eutrophic, non-peat-forming wetlands such as marshes and swamps by the presence in the former of a well-developed ground layer of bryophytes associated with relatively little seasonal water level fluctuation. Oligotrophy is probably maintained in bogs and poor fens by reduced water flow, whereas rich fens maintain mesotrophy by having larger water through-puts; however this is not well documented. Sphagnum appears to have real ecological significance, both in the initial stages of acidification and in controlling surface water temperature. Seasonal variation in surface water chemistry in all peatland types is relatively small, however precipitation events leading to changes in water levels do affect some chemical components. Although both autogenic and allogenic factors affect peatland development, initiation of peat formation and early development of peatlands during the Early and Mid Holocene were considerably influenced by regional climatic change. Later developmental patterns during the late Holocene and those seen at the present time appear to be more influenced by autogenic factors.

Longitudinal patterns of concentration-discharge relationships in stream water draining the Hubbard Brook Experimental Forest, New Hampshire

Longitudinal variations of concentration-discharge relationships and chemical fluxes were evaluated in two headwater streams at the Hubbard Brook Experimental Forest, New Hampshire. At high elevations changes in subsurface flow paths explained variations in H +, inorganic Al and Si concentrations, whereas variations of DOC concentration were inconsistent with this mechanism. Flow responses of middle and low elevation subcatchments were influenced by variable contributions of hydrologic source areas and the elevational concentration gradient which exists in these catchments, but in most cases were not consistent with responses predicted by changes in flow paths. Spatial patterns of chemical fluxes indicate that, in general, catchment neutralization processes increased in effectiveness in the downslope direction. However, this pattern can be interrupted by secondary tributaries, both ephemeral and persistent, which originate in variable source areas that contribute acidic surface runoff during high flow conditions. Current models of catchment acidification need to incorporate spatial variations of biogeochemical processes and flow responses to improve predictions of short-term variations in surface water chemistry.