Groundwater acidification in Triassic sandstones: prediction with MAGIC modelling

 Acidification of groundwater lags behind acid deposition due to the relatively long water residence time in conjunction with various buffering processes in the soil zone and deeper aquifer (chemical weathering, cation exchange, sulfate sorption, and N uptake by the biomass). Extensive field data from eight forested catchments in the Bunter Sandstone of the Black Forest, including results from water budget studies and hydrochemical analysis of stream and spring waters, were used to simulate the future evolution of ground-water acidification with the MAGIC model. The present acid deposition exceeds the “critical load” (here meaning buffering due to chemical weathering and protonation of organic acids) in six of eight catchments. Two catchments are well buffered because they contain carbonate-bearing layers in the Upper Bunter sandstone. Transient buffering (i.e., cation exchange, N uptake, the sulfate sorption) thus far prevents worse acidification, but this effect will decline in the future. For one of the poorly buffered catchments (Seebach), a two-layer simulation was carried out, based on extensive data from 10 years of measurements. Validation of the long-term simulations by hydrochemical and soil data was hampered by strong annual variations but generally supported by paleolimnological studies. In the future, reductions in the S deposition by 20% and the N deposition by 10% up to the year 2030 are assumed as the most probable scenario. N uptake through soil and vegetation will come to an end as suggested by decreasing C/N ratios of the organic matter. This process is arbitrarily included in the simulations. In the periglacial soil layer, acidification will decrease until the year 2030 and then approach a steady-state condition. In the fractured aquifer, acidification will also proceed at a decreasing rate; however, sulfate desorption up to the year 2130, the end of simulated period, will prevent earlier remediation. Despite a significant reduction in S deposition since the mid-1980s, further efforts are necessary to reduce the emission of acidifying substances. Liming in the recharge area is partially effective to ameliorate “shallow” groundwater but largely fails to ameliorate “deeper” groundwater in the sandstone aquifer. Received: 30 July 1996/Accepted: 23 January 1997     

The influence of colloidal material on aluminium speciation and estimated acid neutralising capacity (ANC)

Cationic Al species (Al_i) cause toxic effects towards fish in acidified water. As several factors can influence the Al_i-speciation, acid neutralising capacity (ANC) has been applied as an alternative indicator for acidification and effects towards fish. However, the critical range of ANC for biological stress has been shown to be dependent upon the concentration of organic material (DOC). Using in situ size fractionation techniques the influence of particulate and colloidal DOC (0–400 μM) on Al_i-speciation and ANC-values was investigated in Norwegian streams. During high flow events with high river transport of DOC the Al_i concentration increased by a factor of 2 due to retention of colloidal Al species (>10 kDa), probably organic, in the chromatography column. Ultrafiltration (?10 kDa) of water prior to chromatography reduced the influence of non-toxic organic Al-species, on Al_i-speciation. The charge balanced ANC-values (ANC_cb) were also significantly lower (on average 34 μeq L⁻¹) in ultrafiltered water compared to unfiltered water samples, as base cations were associated with colloidal DOC (>10 kDa to 0.45 μm) and organic acids were not incorporated in the ANC_cb estimate. Thus, ANC_cb will underestimate the acidification effects towards fish in organic waters increasing with concentration of colloidal DOC present. Alkalinity based ANC-values (ANC_alk), which include a fraction of organic acids, were similar in unfiltered and ultrafiltered waters, but higher than ANC_cb-values of ultrafiltered samples. Thus, ANC_alk-values also underestimate the acidification effects on fish in organic waters. Based on ultrafiltered samples, however, ANC_cb-values was negatively correlated with Al_i independent of the DOC present and thus a more correct indicator for toxic Al-species.     

Eolian deposition of trace elements onto Taylor Valley Antarctic glaciers

The major ion and trace element chemistry in four 60-110 cm deep snow pits was examined from three Antarctic Taylor Valley glaciers (Commonwealth, Canada and Howard), all located within 20 km of the Ross Sea. Taylor Valley (TV) (77°30′S, 163°15′E) is part of the McMurdo Dry Valleys (MDV), the largest ice-free area in Antarctica. Snow chemistry of these glaciers is strongly influenced by cross-valley (SW-NE and NE-SW) winds that deposit eolian materials, including mineral dust and soluble salts. Arsenic, Cd, Cu, Mo, Pb, Sb and Sn in recent TV glacier snow are almost exclusively derived from eolian dust. The relative magnitude of element variations with depth relate to the exposure of snow sites to prevalent winds. Eolian deposition is a primary source of these elements to Canada Glacier snow and supra and proglacial streams. Eolian processes are likely very important to the delivery and availability of nutrients and, potentially toxic elements to dry valley Antarctic ecosystems.     

Total Hg concentrations in stream and lake sediments: Discerning geospatial patterns and controls across Canada

This article presents an analysis of Geological Survey of Canada (GSC) open-file data for total Hg concentrations (THg) in stream and lake sediments at 142,028 sampling locations. This analysis was done for select survey zones across Canada, with emphasis on discerning THg-relevant geographic, geological, atmospheric and topographic controls. THg was generally highest in areas affected by mining and smelting, followed by areas with high metallogenic source locations. Background levels for THg were elevated in the more populated areas along the south, but dropped toward the remote and coldest locations in the east, north and west. This trend was correlated (R² = 0.74; P < 0.0001) with the 2005 GRAHM projections (Global/Regional Atmospheric Heavy Metals Model) for atmospheric Hg deposition (zones and locations with major geogenic sources and mining activities removed). Mean THg was higher for upland lakes (100.9 ± 0.5 SE, ppb) and streams (71.7 ± 0.6 SE, ppb) than for lowland lakes (94.4 ± 0.86 SE, ppb) and streams (64.2 ± 1.26 SE, ppb). The east-central portion of the Yukon Territory (Selwyn Basin) was analyzed in further detail. Here, THg within the sediments increased with increasing loss-on-ignition and increasing trace-element concentrations, and decreased with an increasing wet-area component per catchment above the sediment sampling locations. The characterization and quantification of these Hg trends is important for modeling and mapping health risks to ecosystems and communities across Canada and elsewhere.     

The Drenchwater deposit,Alaska: An example of a natural low pH environment resulting from weathering of an undisturbed shale-hosted Zn–Pb–Ag deposit

The Drenchwater shale-hosted Zn–Pb–Ag deposit and the immediate vicinity, on the northern flank of the Brooks Range in north-central Alaska, is an ideal example of a naturally low pH system. The two drainages, Drenchwater and False Wager Creeks, which bound the deposit, differ in their acidity and metal contents. Moderately acidic waters with elevated concentrations of metals (pH ? 4.3, Zn ? 1400 μg/L) in the Drenchwater Creek drainage basin are attributed to weathering of an exposed base-metal-rich massive sulfide occurrence. Stream sediment and water chemistry data collected from False Wager Creek suggest that an unexposed base-metal sulfide occurrence may account for the lower pH (2.7–3.1) and very metal-rich waters (up to 2600 μg/L Zn, ? 260 μg/L Cu and ?89 μg/L Tl) collected at least 2 km upstream of known mineralized exposures. These more acidic conditions produce jarosite, schwertmannite and Fe-hydroxides commonly associated with acid-mine drainage. The high metal concentrations in some water samples from both streams naturally exceed Alaska state regulatory limits for freshwater aquatic life, affirming the importance of establishing base-line conditions in the event of human land development. The studies at the Drenchwater deposit demonstrate that poor water quality can be generated through entirely natural weathering of base-metal occurrences, and, possibly unmineralized black shale.     

A 30,000 yr record of land–ocean interaction in the eastern Gulf of Guinea

A 30,000 yr dinocyst and pollen record from the eastern equatorial Atlantic (off Cameroon) has been investigated in order to identify land–ocean linkages during the last deglacial transition. A strong correlation between the abundance of Brigantedinium spp. and the Ca/Fe ratio during the last glacial period suggests enhanced marine productivity in association with cool seawater temperatures and nutrient input linked to coastal upwelling and/or a proximal river mouth. Dry conditions are recorded on the adjacent continent with a significant representation of open vegetation indicators and the Afromontane taxon Podocarpus. After 17 cal ka BP these indicators register a sharp decline as a result of a climatic transition from the dry/cooler conditions of the last glacial period to the wetter/warmer conditions of the deglaciation. Simultaneously, dinocysts show a significant shift from dominant heterotrophs to an increasing abundance of autotrophs, reflecting warmer conditions. Significant changes are observed during the Younger Dryas, with a return to drier conditions and higher salinities. The start of the Holocene is marked by very low-salinity conditions, reflecting optimal monsoonal conditions over west equatorial Africa. The end of the African Humid Period is observed between 6 and 5 cal ka BP, followed by significant fluctuations in both terrestrial and oceanic proxies.     

Precise U–Pb baddeleyite ages of mafic dykes and intrusions in southern West Greenland and implications for a possible reconstruction with the Superior craton

The Archaean block of southern Greenland constitutes the core of the North Atlantic craton (NAC) and is host to a large number of Precambrian mafic intrusions and dyke swarms, many of which are regionally extensive but poorly dated. For southern West Greenland, we present a U–Pb zircon age of 2990 ± 13 Ma for the Amikoq mafic–ultramafic layered intrusion (Fiskefjord area) and four baddeleyite U–Pb ages of Precambrian dolerite dykes. Specifically, a dyke located SE of Ameralik Fjord is dated at 2499 ± 2 Ma, similar to a previously reported ⁴⁰Ar/³⁹Ar age of a dyke in the Kangâmiut area. For these and related intrusions of ca. 2.5 Ga age in southern West Greenland, we propose the name Kilaarsarfik dykes. Three WNW-trending dykes of the MD3 swarm yield ages of 2050 ± 2 Ma, 2041 ± 3 Ma and 2029 ± 3 Ma. A similar U–Pb baddeleyite age of 2045 ± 2 Ma is also presented for a SE-trending dolerite (Iglusuataliksuak dyke) in the Nain Province, the rifted western block of the NAC in Labrador. We speculate that the MD3 dykes and age-equivalent NNE-trending Kangâmiut dykes of southern West Greenland, together with the Iglusuataliksuak dyke (after closure of the Labrador Sea) represent components of a single, areally extensive, radiating swarm that signaled the arrival of a mantle plume centred on what is presently the western margin of the North Atlantic craton. Comparison of the magmatic ‘barcodes’ from the Nain and Greenland portions of the North Atlantic craton with the established record from the north-eastern Superior craton shows matches at 2500 Ma, 2214 Ma, 2050–2030 Ma and 1960–1950 Ma. We use these new age constraints, together with orientations of the dyke swarms, to offer a preliminary reconstruction of the North Atlantic craton near the north-eastern margin of the Superior craton during the latest Archaean and early Palaeoproterozoic, possibly with the Core Zone craton of eastern Canada intervening.     

Human-ecosystem interactions in relation to Holocene environmental change in Port Joli Harbour,southwestern Nova Scotia,Canada

A high-resolution pollen record from Path Lake in Port Joli Harbour, Nova Scotia, Canada, provides a paleo-ecological perspective on Holocene climate and vegetation variability within the context of local archaeological research. Pollen assemblages in the early Holocene reflect a post-glacial forest dominated by Pinus, Tsuga, Betula and Quercus. During this time, a lower frequency of radiocarbon dated cultural material suggests lower human settlement intensity. Shallow water aquatic (Isoetes) and wetland (Alnus, Sphagnum) taxa increased after 3400 cal yr BP in response to a transition towards wetter climatic conditions. Culturally significant periods, where settlement intensity increased in the Maritimes and Maine, coincide with maximum values of reconstructed total annual precipitation, suggesting that environmental conditions may have influenced prehistoric human activity. European settlement, after 350 cal yr BP, was marked by a rise in Ambrosia. The impact of anthropogenic fire disturbances on the landscape was evidenced by peak charcoal accumulations after European settlement.     

Terrigenous organic matter sources in mid-pleistocene sediments from the orphan knoll,Northwest Atlantic Ocean

The concentration and composition of lignin-derived phenols, which are often used as biomarkers for terrigenous organic matter (OM) inputs, were examined in North Atlantic Ocean sediments from IODP core U1302A (50°9.985′N, 45°38.271′W, 3568 m water depth), Orphan Knoll, 650 km NE of St. John’s, Newfoundland, Canada for the period of ca. 1100–810 ka BP. Lignin-derived phenols were extracted from sediments using CuO oxidation which yielded eight characteristic phenols. The majority of sediments have low syringyl phenol to vanillyl phenol (S/V) ratios and high cinnamyl phenol to vanillyl phenol (C/V) ratios, suggesting predominant concentrations of gymnosperm-derived organic matter inputs from adjacent continents (most likely eastern Canada and possibly southern Greenland). The S/V values were lower for the period of ca. 958–840 ka BP relative to ca. 1090–1078, 1042–958 and 840–818 ka BP, indicating fluctuations in the proportion of angiosperm- and gymnosperm-derived lignin delivery to the ocean. The greater fraction of gymnosperms for the period of 958–840 ka BP likely reflects the response of vegetation in source regions to climate cooling in the early part of the mid-Pleistocene. Lignin-derived phenol concentrations also displayed high variability during the investigated period, which did not show positive correlations with magnetic susceptibility or Gamma Ray Attenuation density. Considering that a fundamental climate change (41–100 ka cyclicity) occurred within the mid-Pleistocene, large variations in abundance and composition of lignin-derived phenols in core U1302A is likely indicative of dynamic environmental conditions, reflected by the variability in both concentrations and types of vegetation on adjacent continents and/or different mechanisms to transport terrigenous organic matter to the deep ocean.     

Tracing industrial sulfur contributions to atmospheric sulfate deposition in the Athabasca oil sands region,Alberta, Canada

Anthropogenic S emissions in the Athabasca oil sands region (AOSR) in Alberta, Canada, affect SO₄ deposition in close vicinity of industrial emitters. Between May 2008 and May 2009, SO₄-S deposition was monitored using open field bulk collectors at 15 sites and throughfall collectors at 14 sites at distances between 3 and 113 km from one of the major emission stacks in the AOSR. At forested plots >90 km from the operations, SO₄ deposition was ∼1.4 kg SO₄-S ha⁻¹ yr⁻¹ for bulk deposition and ∼3.3 kg SO₄-S ha⁻¹ yr⁻¹ for throughfall deposition. Throughfall SO₄ deposition rates in the AOSR exceeded bulk deposition rates at all sites by a factor of 2–3, indicating significant inputs of dry deposition especially under forest canopies. Both bulk and throughfall SO₄ deposition rates were elevated within 29 km distance of the industrial operations with deposition rates as high as 11.7 kg SO₄-S ha⁻¹ yr⁻¹ for bulk deposition and 39.2 kg SO₄-S ha⁻¹ yr⁻¹ for throughfall at industrial sites. Sulfur isotope ratio measurements of atmospheric SO₄ deposited in the AOSR revealed that at a few selected locations ³⁴S-depleted SO₄, likely derived from H₂S emissions from tailing ponds contributes to local atmospheric SO₄ deposition. In general, however, δ³⁴S values of SO₄ deposition at distant forested plots (>74 km) with low deposition rates were not isotopically different from δ³⁴S values at sites with high deposition rates in the AOSR and are, therefore, not suitable to determine industrial S contributions. However, O isotope ratios of atmospheric SO₄ in bulk and throughfall deposition in the AOSR showed a distinct trend of decreasing δ¹⁸O-SO₄ values with increasing SO₄ deposition rates allowing quantification of industrial contributions to atmospheric SO₄ deposition. Two-end-member mixing calculations revealed that open field bulk SO₄ deposition especially at industrial sites in close proximity (<29 km) to the operations is significantly (17–59%) affected by industrial S emissions and that throughfall generally contained 49–100% SO₄ of industrial origin. Hence, it is suggested that δ¹⁸O values of SO₄ may constitute a suitable tracer for quantifying industrial contributions to atmospheric SO₄ deposition in the AOSR.     

Speleothem evidence of warm episodes in northeast France during Marine Oxygen Isotope Stage 3 and implications for permafrost distribution in northern Europe

U-Th ages have been obtained by TIMS on the growth periods of a stalagmite from the “Grotte des Puits de Pierre-la-Treiche” (northeastern France), during the middle part of the “Weichselian glaciation” (Marine Isotope Stage 3), between 55.36 ± 0.95 and 53.34 ± 0.49 ka and around 45.85 ± 0.49 ka. These episodes are contemporaneous with abrupt climatic variations recorded in Greenland ice cores (Greenland interstadials 12, 14 and 15) that have been previously recognized in European speleothems. They also coincide with two interstadials, known as “Goulotte” and “Pile” in the Grande Pile pollen sequence (eastern France), which have been correlated with the Moershoofd complex in the Netherlands. Such evidence of speleothem deposition related to temperate episodes gives a strong indication of the absence of continuous shallow permafrost during the middle part of MIS 3 in northeastern France.     

Mercury emission from terrestrial background surfaces in the eastern USA. II: Air/surface exchange of mercury within forests from South Carolina to New England

Mercury air/surface exchange was measured over litter-covered soils with low Hg concentrations within various types of forests along the eastern seaboard of the USA. The fieldwork was conducted at six forested sites in state parks in South Carolina, North Carolina, New Jersey, Pennsylvania, New York and Maine from mid-May to early June 2005. The study showed that the Hg air/surface exchange was consistently very low and similar (overall daytime mean flux = 0.2 ± 0.9 ng m⁻² h⁻¹, n = 310, for all six sites monitored) with the various forest types. These flux values are comparable with those found in a year-long study in Tennessee (yearly daytime mean = 0.4 ± 0.5 ng m⁻² h⁻¹), but lower than many previous flux results reported for background soils. The Hg fluxes at all sites oscillated around zero, with many episodes of deposition (negative fluxes) occurring in both daytime and nighttime. While there were particular days showing significant correlations among the Hg air/surface exchange and certain environmental parameters, perhaps because of the low fluxes encountered, few significant correlations were found for any particular day of sampling between the Hg flux and environmental parameters such as solar radiation, soil temperature, air temperature (little variability seen), relative humidity, and ambient air Hg concentrations. Factors driving the Hg exchange as previously found for enriched soils may not hold for these background litter-covered forest soils. The results suggest that spatial variations of the Hg air/surface exchange were small among these different forest types for this particular time of year.     

The effect of Ca–Fe–As coatings on microbial leaching of metals in arsenic bearing mine waste

Globally arsenic (As) is a ubiquitous trace element derived from the natural weathering of As-bearing rock. With the onset of reducing conditions, the prevalence of aqueous As(III) may be intensified through biotic and abiotic processes. Here we evaluate the stability of arsenic bearing Ca–Fe hydroxide phases collected from exposed tailings at Ketza River mine, Yukon, Canada, during the reductive dissolution of both acid treated and untreated samples by Shewanella putrefaciens 200R and Shewanella sp. ANA-3. Samples were acid treated in order to remove Ca–Fe oxide coatings and evaluate the influence of these coatings on the rates of microbial Fe(III) and As(V) reduction. Environmental scanning electron microscope (ESEM) micrographs of the solid phase show significant differences in the chemistry and physical morphology of the material by the bacteria over time and are especially evident in the acid treated samples. Moreover, while solution chemistry showed similar As(III) respiration rates of the inoculated acid treated samples for both ANA3 and 200R at ~ 1.1 × 10⁻⁶ μM·s^− 1·m^− 2, the Fe(II) respiration rates differed at 1.4 × 10^− 7 and 9.5 × 10^− 8 μM·s^− 1·m⁻² respectively, thus suggesting strain specific metal reduction metabolic pathways Additionally, the enhanced metal reduction observed in the acid treated inoculated samples suggests that the presence of the Ca–Fe hydroxide phase in the untreated samples acted as a barrier, inhibiting the bacteria from accessing the metals. This has implications for increased mobilization of metals by metal reducing bacteria within areas of increased acidity, such as acid mine drainage sites and industrial tailings ponds that can come into contact with surface and ground water sources.     

An integrated modelling approach to reconstruct complex solute transport mechanisms - Cl and δCl in pore water of sediments from a former brackish lagoon in The Netherlands

A one-dimensional transport model was developed to reconstruct historical conservative transport of chloride and δ³⁷Cl in pore water of sediments from a former brackish lagoon in The Netherlands, an area now covered by the freshwater Lakes IJssel and Marken. Knowledge of the mechanism of historical solute transport in the sediments and environmental conditions during transport is critical in understanding observed pore water chemistry and will form a basis for simulating effects of changing environmental (climate change) conditions. The model synthesizes present knowledge of geology and historical information on storm surges in the area and takes into account processes such as erosion of sediments, mixing of pore water, sedimentation, and diffusion (EMSD). The chemistry of pore water from one particular boring in the area was found to be mainly controlled by alternating seawater and freshwater diffusion. Models with a constant (averaged) porosity (? = 0.55) and tortuosity factor (τ = 0.3) showed similar results as models incorporating the measured bulk porosity variations (? = 0.4-0.8) and variable tortuosity factors calculated with Archie’s law, τ = ?. The relatively small tortuosity factor either results from anion exclusion or from the heterogeneous build-up of the profile in which a peaty layer in the middle part may obstruct diffusion. Diffusion of ³⁵Cl⁻ was found to be 1.0017 times faster than of ³⁷Cl⁻. Seawater diffusion into the sediments started at least 400 years ago and refreshening took place since the lagoon was isolated from the sea by a dam in 1932.     

Total particulate and reactive gaseous mercury in ambient air on the eastern slope of the Mt. Gongga area,China

Total particulate mercury (TPM) and reactive gaseous mercury (RGM) concentrations in ambient air on the eastern slope of the Mt. Gongga area, Sichuan Province, Southwestern China were monitored from 25 May, 2005 to 29 April, 2006. Simultaneously, Hg concentrations in rain samples were measured from January to December, 2006. The average TPM and RGM concentrations in the study site were 30.7 and 6.2 pg m⁻³, which are comparable to values observed in remote areas in Northern America and Europe, but much lower than those reported in some urban areas in China. The mean seasonal RGM concentration was slightly higher in spring (8.0 pg m⁻³) while the minimum mean concentration was observed in winter (4.0 pg m⁻³). TPM concentrations ranged across two orders of magnitude from 5.2 to 135.7 pg m⁻³ and had a clear seasonal variation: winter (74.1 pg m⁻³), autumn (22.5 pg m⁻³), spring (15.3 pg m⁻³) and summer (10.8 pg m⁻³), listed in decreasing order. The annual wet deposition was 9.1 μg m⁻² and wet deposition in the rainy season (May–October) represented over 80% of the annual total. The temporal distribution of TPM and RGM suggested distinguishable dispersion characteristics of these Hg species on a regional scale. Elevated TPM concentration in winter was probably due to regional and local enhanced coal burning and low wet deposition velocity. The RGM distribution pattern is closely related to daily variation in UV radiation observed during the winter sampling period indicating that photo-oxidation processes and diurnal changes in meteorology play an important role in RGM generation.     

Timing of advance and basal condition of the Laurentide Ice Sheet during the last glacial maximum in the Richardson Mountains,NWT

This study presents new ages for the northwest section of the Laurentide Ice Sheet (LIS) glacial chronology from material recovered from two retrogressive thaw slumps exposed in the Richardson Mountains, Northwest Territories, Canada. One study site, located at the maximum glacial limit of the LIS in the Richardson Mountains, had calcite concretions recovered from aufeis buried by glacial till that were dated by U/Th disequilibrium to 18,500 cal yr BP. The second site, located on the Peel Plateau to the east yielded a fossil horse (Equus) mandible that was radiocarbon dated to ca. 19,700 cal yr BP. These ages indicate that the Peel Plateau on the eastern flanks of the Richardson Mountains was glaciated only after 18,500 cal yr BP, which is later than previous models for the global last glacial maximum (LGM). As the LIS retreated the Peel Plateau around 15,000 cal yr BP, following the age of the Tutsieta phase, we conclude that the presence of the northwestern margin of the LIS at its maximum limit was a very short event in the western Canadian Arctic.     

Some insight into the influence of urban ground surface properties on the air-surface exchange of total gaseous mercury

Experiments utilizing meteorologically normalized sampling conditions were used to illustrate the role and function of urban pavement, bare soil and turf grass surface properties with respect to the air-surface exchange of total gaseous Hg (TGM). After ensuring uniform meteorological effects to each surface, resultant TGM fluxes from turf grass, bare soil and pavement were specifically representative of their diverse physical and biogeochemical properties. Results spanning the entire sampling year show distinct TGM flux signatures for each surface (5.69 ± 5.79 (ng/m² h) for bare soil, 0.53 ± 1.25 for turf grass, 0.26 ± 0.41 for pavement). Based on medians, the surface limitations of pavement decreased TGM flux by a factor of 22 compared to bare soil and by a factor of 2 compared to turf grass. Turf surface limitations decreased TGM flux by a factor of 11 compared to bare soil. By comparing these results to a parallel study, meteorological effects were found to develop 24% of the TGM flux signature for pavement, 53% for turf and 60% for bare soil. The remaining percentage contributions to each TGM flux signature were from the cumulative surface property effects of each surface. These results suggest that the greater the TGM flux magnitude for a particular surface, the more measurements are needed under a wide variety of meteorological conditions to develop a broad understanding of its TGM flux characteristics. Seasonal observation allowed closer investigation of a large shift to TGM deposition for the turf surface during the fall season. The large shift toward deposition was suspected to be linked to the formation of a thatch layer on the unexposed soil surface just beneath the turf layer.     

Naturally acidic surface and ground waters draining porphyry-related mineralized areas of the Southern Rocky Mountains,Colorado and New Mexico

Acidic, metal-rich waters produced by the oxidative weathering and resulting leaching of major and trace elements from pyritic rocks can adversely affect water quality in receiving streams and riparian ecosystems. Five study areas in the southern Rocky Mountains with naturally acidic waters associated with porphyry mineralization were studied to document variations in water chemistry and processes that control the chemical variations. Study areas include the Upper Animas River watershed, East Alpine Gulch, Mount Emmons, and Handcart Gulch in Colorado and the Red River in New Mexico. Although host-rock lithologies in all these areas range from Precambrian gneisses to Cretaceous sedimentary units to Tertiary volcanic complexes, the mineralization is Tertiary in age and associated with intermediate to felsic composition, porphyritic plutons. Pyrite is ubiquitous, ranging from ∼1 to >5 vol.%. Springs and headwater streams have pH values as low as 2.6, SO₄ up to 3700 mg/L and high dissolved metal concentrations (for example: Fe up to 400 mg/L; Cu up to 3.5 mg/L; and Zn up to 14.4 mg/L). Intensity of hydrothermal alteration and presence of sulfides are the primary controls of water chemistry of these naturally acidic waters. Subbasins underlain by intensely hydrothermally altered lithologies are poorly vegetated and quite susceptible to storm-induced surface runoff. Within the Red River study area, results from a storm runoff study documented downstream changes in river chemistry: pH decreased from 7.80 to 4.83, alkalinity decreased from 49.4 to <1 mg/L, SO₄ increased from 162 to 314 mg/L, dissolved Fe increased from to 0.011 to 0.596 mg/L, and dissolved Zn increased from 0.056 to 0.607 mg/L. Compared to mine drainage in the same study areas, the chemistry of naturally acidic waters tends to overlap but not reach the extreme concentrations of metals and acidity as some mine waters. The chemistry of waters draining these mineralized but unmined areas can be used to estimate premining conditions at sites with similar geologic and hydrologic conditions. For example, the US Geological Survey was asked to estimate premining ground-water chemistry at the Questa Mo mine, and the proximal analog approach was used because a mineralized but unmined area was located adjacent to the mine property. By comparing and contrasting water chemistry from different porphyry mineralized areas, this study not only documents the range in concentrations of constituents of interest but also provides insight into the primary controls of water chemistry.