Wildfire Effects on the Quantity and Composition of Suspended and Gravel-Stored Sediments

In August of 2003 a severe wildfire burnt the majority of Fishtrap Creek, a 170 km² catchment in central British Columbia, Canada. The objective of this study was to determine the short-term (15-month) influence of the wildfire on the amount and composition of fine sediment delivery and retention in the system and to compare it to a similar unburnt catchment. In the spring of 2004 automatic water samplers were installed at a gauging site on Fishtrap Creek to collect suspended sediments from the snowmelt runoff and gravel traps were deployed on the channel bed surface to collect composite samples of suspended fine sediment. Jamieson, the reference creek, exhibits similar geology and pre-burn vegetation and was sampled in the same manner for comparison. Composite suspended sediment collected in the traps was removed from the streams in mid-summer and early September. Quantitative estimates of the amount and particle size structure of the naturally stored fine sediment in, and on, the gravel creekbed were obtained in pre-melt, mid and late-summer conditions. Estimates of suspended sediment yields indicated that while the burnt system delivered 66% more material per unit area, the total seasonal suspended sediment yield was low (855 kg km⁻²) compared to other fire-disturbed systems. While the burnt catchment was primed to deliver sediment, the hydrologic drivers were not of sufficient magnitude to generate a substantial response, suggesting that in this first post-fire year the system was transport-limited, not supply-limited. Differences were noted in the spatial and seasonal composition of the <500 more OM% composite suspended sedimentswith the burnt catchment having significantly (P≤0.05) more OM%. Seasonally a significant increase of OM% in late summer samples was associated with instream biofilms and possible delivery of black carbon. The system’s post-fire response was not geomorphically substantial but significant biological differences were noted in the short-term.     

Spatial and Temporal Variations in the Sediment Habitat of Ranunculus spp. in Lowland Chalk Streams – Implications for Ecological Status?

Ranunculus spp. are the dominant plants of lowland chalk stream habitats in England. The spatial variability of sediment characteristics (silt–clay, organic matter, total phosphorus and total nitrogen content) within stands of Ranunculus spp. was investigated in 12 rivers in lowland England. Variability was found to be high and there were no discernible differences between samples taken from within Ranunculus and a limited number of samples from bare substrate. For two of these rivers, comparisons were also made between reaches upstream and downstream of waste water treatment works outfalls in terms of the characteristics of the sediments within Ranunculus stands. In one river a clear increase in sediment nutrient, fine and organic material content was observed downstream but in the other there was no consistent difference. Temporal variability was considered for two rivers in the Frome catchment, Dorset, by analysing the monthly variability in sediment organic matter and silt–clay content beneath Ranunculus stands over an annual cycle of growth and die-back. Whilst a clear pattern of fine and organic material retention consistent with seasonal plant growth patterns was evident at one site, the three sites displayed different temporal patterns. This inconsistency is believed to reflect differences in sediment supply at the three sites.     

Recent Sediment of Lake Bled (NW Slovenia): Sedimentological and Geochemical Properties

Sediment cores collected in eutrophic subalpine Lake Bled (NW Slovenia) were analyzed sedimentologically in terms of grain size, mineralogy and sedimentation rates, and geochemically in terms of metals and nutrients. Surficial sediment is composed of dark gyttya type clayey silt with 5%–10% of organic matter. The sediment below is fine laminated and composed of homogenous silt and clayey silt: Mineralogically, low-Mg calcite prevails, followed by dolomite, quartz, partially of diatomaceous origin, and feldspar. Clay minerals are composed of muscovite/illite and chlorite. Authigenic minerals are pyrite and ‘lake chalk’ (low-Mg calcite). Lake sediment is especially polluted by Pb, Zn and P. Higher contents were found in the northwestern and eastern parts due to the particle input by local inflows. Increasing eutrophication and pollution, indicated by Cd, Cu, V, Cr, Co and total N and P enrichment in the top layers of the cores, started almost 100 years B.P., and especially 50 years ago.     

Streambed Sediment Geochemical Controls on In-Stream Phosphorus Concentrations during Baseflow

A spatially extensive geochemical data set of stream water and bed sediment composition across the Tamar catchment in south-west England was analysed to identify the key bed sediment properties that control the in-stream dissolved reactive phosphorus (DRP) concentrations during baseflow conditions. Linear regression analysis of the streamwater DRP concentrations and the distribution coefficient K _d for DRP revealed that the former is positively correlated with total SiO₂ and Al₂O₃, and negatively correlated with K₂O. The primary control on these major element distributions is the dominant bedrock geology. The data suggest that streamwater DRP concentrations are mainly controlled by adsorption to clay minerals. Where P concentrations in streamwater were considerably elevated by inputs from point sources, DRP concentrations are also controlled by precipitation of hydroxyapatite.     

Transformation of Particle-Bound Phosphorus at the Land–Sea Interface in a Danish Estuary

Danish rivers carry >50% of the phosphorus (P) transport as particulate P (PP). In five of six rivers sampled in November 1998 iron-bound P made up > 59% of PP and loosely adsorbed P ranged between 2% and 13%. This fraction could potentially be released in 14‰ seawater. The behaviour of dissolved and particulate P fractions was studied during seven month in a 2 km long estuary with low freshwater retention time and low tidal range. The river carried ∼10% of PP as loosely adsorbed P but increased concentrations of dissolved inorganic P (DIP) relative to the estuarine mixing line was only observed in the summer month with low freshwater flow and was more likely due to DIP release from the bottom sediment. Instead estuarine particles were always enriched with oxidized iron (ox.Fe) and iron-bound P as well as loosely adsorbed P and during May–September this coincided with increasing concentration of PP in estuary. We suggest that flocculation of ox.Fe and adsorption of DIP onto the particles with subsequent transport seawards is a major loss process for P during the summer month. During winter month where 85% of the run-off occurs the dominant process in the estuary is sedimentation of larger particles, however, a comparison of river particles with surface sediment clearly reveals that most PP is mobilized again from the bottom sediments.     

Relationship Between the Sediment Geochemistry and Phosphorus Fluxes in a Great Lakes Coastal Marsh,Cootes Paradise,ON, Canada

Cootes Paradise is a coastal wetland, adjacent to Hamilton Harbour at the western tip of Lake Ontario. The marsh has been considerably degraded due to the excessive sediment and nutrient input from sewage treatment plants (STPs), marsh tributaries and Combined Sewer Overflows (CSOs). Although there has been reduction in nutrient loadings from external sources, high nutrient levels, and a prolific algal growth remain a problem in Cootes Paradise. To assess the importance of external versus internal nutrient loadings to the marsh, nutrient fluxes from sediments were estimated using porewater profiles at three locations from 2001 and five additional sites from 2002. The fluxes varied between 0.27 and 5.25 mg P m⁻² day⁻¹, with sites receiving outfalls of STP and CSO having highest fluxes (∼5 mg P m⁻² day⁻¹). Mean phosphorus release rate of 2.02 mg P m⁻² day⁻¹ was calculated from the spatial distribution of the non-apatite inorganic phosphorus (NAI-P) in sediments, employing a relationship between the NAI-P and P fluxes. The results confirm that sediment P geochemistry is important in regulating the P pool in porewater which, consequently, governs the P fluxes from sediments.     

Temporal Trends in Mercury Accumulation in Lake Sediments in Sweden

Lake sediment cores were analyzedto study the history of mercury (Hg) pollution andparticularly to determine whether recent sedimentconcentrations have declined in response todeclining atmospheric deposition of Hg. Sedimentcores from 6 forest lakes distributed fromsouthern to northern Sweden and 3 northernmountain lakes were analyzed for Hg using CVAAS. A400 cm sediment profile from Måkevatten insouthwest Sweden indicates that the onset of Hgpollution occurred in the 18th century. Anindisputable increase in Hg concentrationsoccurred concurrent with the appearance ofspheroidal carbonaceous flyash particles (SCP)derived from fossil-fuel combustion, in themid-19th century. There is a strong correlationbetween Hg and SCP concentrations in the sedimentcores (r=0.67 to 0.91), which suggests a strongrelationship between historical Hg pollution andfossil fuel burning. In contrast to sediment corestaken in 1979, maximum Hg concentrations are nowobserved below the sediment surface and declinetowards the sediment surface. This study confirmsthat reductions in atmospheric deposition of Hgover Sweden have resulted in a decreased transferof total Hg to aquatic environments as reflectedby lake sediments, and that lake sediment profilesof Hg concentrations reflect relative trends inthe atmospheric deposition of Hg rather thanpost-depositional diagenetic processes.     

The Use of Numerical Weather Prediction Model Output in Spill Modelling

Numerical weather prediction model output may be used in simulating the movement of water borne pollutants with little significant loss of accuracy in comparison to the use of observed wind data of equivalent temporal resolution. Spatial variations in the instantaneous wind field over the region of influence of a spill were found to be less significant than the uncertainties in the wind at a single point. However, temporal variations in the wind must be included in the spill simulations, with a minimum recommended resolution of 3 h.     

Dissolved Oxygen and Nutrient Fluxes Across the Sediment–Water Interface of the Neckar River,Germany: In Situ Measurements and Simulations

A benthic in situ flume and a 1D biogeochemical sediment model to evaluate solute fluxes across the sediment–water interface have been developed. The flume was successfully used to determine oxygen and nutrient fluxes at various locations of the Neckar River in Germany. The experimental results were linked with vertical pore water concentration profiles and independently verified with the model. By combining experimental and model results we assessed the influence of dissolved oxygen concentrations in the water column and the availability of degradable organic matter on sediment oxygen demand. The results and the derived relations can be used to parameterize the sediment module of large scale water quality models, allowing one to assess the influence of sediment–water interactions on various aspects of river water quality. Moreover, the biogeochemical sediment model can help to improve the general understanding of the processes governing solute concentrations and fluxes in sediments and across their interfaces.     

Study of fine sediments for making lightweight aggregate.

The objective of this study was to investigate the recycling of the fine sediments of Shih-Men Reservoir to manufacture lightweight aggregate. By qualitative and quantitative analysis of the fine sediment and sintered aggregate through soil test, X-ray fluorescence, X-ray diffraction and scanning electron microscopy, a strategy of recycling fine sediment as aggregate for other similar material is proposed. The test results indicate that such fine sediment can be classified as low plastic clay, and clay of such chemical composition is located in the Riley's 'area of bloating'. The particle density of sintered lightweight aggregate decreases when the sintering temperature increases especially above 1200 degrees C due to phase transformation and formation of a vitrified layer on the surface through subsequent dehydration, bloating and collapsing stages. Our findings show that the fine sediment of Shin-Men Reservoir could be a suitable raw material for making expanded lightweight aggregate sintered at 1200 to 1300 degrees C for 10 to 12 min by a programmable furnace and a diffusion process.     

Changes in Sediment Sources following Wildfire in Mountainous Terrain: A Paired–Catchment Approach,British Columbia,Canada

This paper describes a study examining the potential of mineral magnetic, geochemical and organic properties to determine if a 2003 wildfire in a catchment in British Columbia, Canada, caused a change in the sources of the suspended sediment transported in the channel relative to a nearby unburnt (reference) catchment. The results show that some of the properties offer the potential to determine sediment sources in the unburnt catchment. However, the 2003 wildfire modified the concentrations of some properties and this can either compromise or enhance their ability as tracers in the burnt catchment. At present, the source tracing results are inconclusive. This has implications for the use of certain properties as fingerprints and raises important issues about approaches to sediment source identification.     

Micrometeorological measurements of N2O and CH4 emissions from a municipal solid waste landfill.

Micrometeorological measurements of methane (CH4) and nitrous oxide (N2O) emissions were made at the decommissioned Park Road Landfill in Grimsby, Ontario, Canada between June and August 2002. The influence of precipitation, air temperature, wind speed and barometric pressure on the temporal variability of landfill biogas emissions was assessed. Gas flux measurements were obtained using a micrometeorological mass balance measurement technique [integrated horizontal flux (IHF)] in conjunction with two tunable diode laser trace gas analyser (TDLTGA) systems. This method allows for continuous, non-intrusive measurements of gas flux at high temporal resolution. Mean fluxes of N2O were negligible over the duration of the study (-0.23 to 0.02 microg m(-2) s(-1)). In contrast, mean emissions of CH4 were much greater (80.4 to 450.8 microg m(-2) s(-1)) and varied both spatially and temporally. Spatial variations in CH4 fluxes were observed between grass kill areas (biogas 'hot spots') and the densely grass-covered areas of the landfill. Temporal variations in CH4 fluxes were also observed, due at least in part to barometric pressure, wind speed and precipitation effects.     

Nutrients Seasonal Variation and Budget in Jiaozhou Bay,China: A 3-Dimensional Physical–Biological Coupled Model Study

A 3-D biological model was developed and coupled to a hydrodynamic model, i.e., Princeton Ocean Model, to simulate the seasonal variation and budget of dissolved inorganic nitrogen, phosphate, and silicate in Jiaozhou Bay. The modeled nutrients distribution pattern is consistent with observation. Silicate, the most important limiting element for phytoplankton growth, is characterized by consumption in spring, increase in summer and autumn, and accumulation in winter, whereas dissolved inorganic nitrogen and phosphorous have increasing trend with low rates in spring, due to excessive river loads. Phytoplankton plays an important role in nutrient renewal by photosynthesis and respiration processes. During an annual cycle, 7.83 × 10³ t N, 0.28 × 10³ t P, and 3.93 × 10³ t Si are transported to the bay’s outer sea, i.e., the Yellow Sea, suggesting that Jiaozhou Bay is a significant source of nutrients for the Yellow Sea. The spatial distribution of nutrients is characterized by vertically homogeneous profiles, with high concentration inside the bay and low concentration toward the bay channel. These features are mainly governed by strong turbulent mixing, fluvial influx, water exchange rate, and Yellow Sea water intrusion. Numerical experiments suggest that the government should pay enough attention to proper layout of sewage drainage.     

SedTrap: A Conceptual Model for Trap Efficiencies in a Sedimentation Basin

Sedimentation basins and sediment traps are established methodologies for reducing sediment and other pollutants exiting small watersheds such as urban areas and construction sites. However, estimating the trap efficiency or designing a basin or trap to provide a pre-determined trap efficiency, is difficult, especially for dynamic conditions of water and sediment inflow. A conceptual dynamic model, called SedTrap, was developed that can be used to assess the varying removal efficiencies as a storm is routed through different sized basins or traps. The model uses the STELLA® modeling software from Iseesystems, Inc. to build a dynamic model to route both water and sediment through the system. Settling velocities are determined for a range of sediment sizes and temperatures using the Rubey-Watson law and compared to the more traditional Stokes’ law. The variation of efficiencies with time and by sediment size as the basin fills with sediment is also addressed. The results for the example used show a decrease in trap efficiencies with decreasing particle size, which leads to an increase in percent fine material of total sediment load at the outlet of the basin. This “fining” of the material coupled with the higher surface area per mass of the fine particles has implications for changes in the upstream-downstream concentrations of adsorbed contaminants.     

Modelling Seasonal Dynamics from Temporal Variation in Agricultural Practices in the UK Ammonia Emission Inventory

Most ammonia (NH₃) emission inventories have been calculated on an annual basis and do not take into account the seasonal variability of emissions that occur as a consequence of climate and agricultural practices that change throughout the year. When used as input to atmospheric transport models to simulate concentration fields, these models therefore fail to capture seasonal variations in ammonia concentration and dry and wet deposition. In this study, seasonal NH₃ emissions from agriculture were modelled on a monthly basis for the year 2000, by incorporating temporal aspects of farming practice. These monthly emissions were then spatially distributed using the AENEID model (Atmospheric Emissions for National Environmental Impacts Determination). The monthly model took the temporal variation in the magnitude of the ammonia emissions, as well as the fine scale (1-km) spatial variation of those temporal changes into account to provide improved outputs at 5-km resolution. The resulting NH₃ emission maps showed a strong seasonal emission pattern, with the highest emissions during springtime (March and April) and the lowest emissions during summer (May to July). This emission pattern was mainly influenced by whether cattle were outside grazing or housed and by the application of manures and fertilizers to the land. When the modelled emissions were compared with measured NH₃ concentrations, the comparison suggested that the modelled emission trend corresponds fairly well with the seasonal trend in the measurements. The remaining discrepancies point to the need to develop functional parametrisations of the interactions with climatic seasonal variation.     

The Influence of Chironomus plumosus Larvae on Nutrient Fluxes and Phosphorus Fractions in Aluminum Treated Lake Sediment

One of the methods to diminish the internal phosphorus (P) loading is inactivation of P by aluminum (Al). After addition of Al to lake water an Al(OH)₃ floc is formed, which settles to the bottom and initially form a lid on the sediment surface. The effects of Chironomus plumosus larvae on sediment nutrient fluxes and P binding-sites in the sediment after addition of Al were tested. C. plumosus larvae were added to sediment cores in which sediment–water fluxes of nutrients were measured four times. After one month, the sediment was sectioned with depth and P fractions were measured by sequential chemical extraction. The chironomids created burrows through the Al layer which caused a significantly increased efflux of P from the Al treated sediment, because the P had only limited contact to the added Al. The chironomids also affected the P fractions in the sediment by their bioturbating activity. Thus, they caused increased Al concentrations in the upper part of the Al treated sediment. This created an enhanced contact between Al and P in the upper 7 cm of the sediment and, as a result, an increased binding of P to Al and a lowered porewater P. The DIP efflux is therefore expected to be lowered after the initial phase. Al had no effects on the nitrogen fluxes, but the chironomids enhanced the release, and decreased the release or increased the uptake by the sediments.     

Study of Pollution of the Plitvice Lakes by Water and Sediment Analyses

The process of eutrophication in form of intense plant growth has been observed in some lakes and water streams at the Plitvice Lakes National Park in central Croatia. Here we investigate whether this phenomenon is a consequence of anthropogenic pollution or due to naturally produced organic matter in the lakes. We applied chemical analysis of water at two springs and four lakes (nutrients, dissolved organic carbon (DOC), trace elements) and measurements of surface lake sediments (mineral and organic fraction analyses, trace elements) in four different lakes/five sites. The chemical composition of water does not indicate recent anthropogenic pollution of water because the concentrations of most trace elements are below detection limits. The concentrations of DOC and nutrients are slightly higher in the area of increased eutrophication-plant growth. Also the content of organic matter in the sediment is at the highest level in areas with highest C/N ratio indicating that the organic fraction of this sediment is mainly of terrestrial origin. There is no significant difference among the trace element concentration in the upper segment of all cores, deposited approximately during last 50 years when higher anthropogenic influence is expected due to development and touristic activity, and the lower part of the cores, corresponding to the period approximately 100–200 years before present. The content of trace elements and organic matter in sediments decreases from the uppermost lake downstream. According to our results there is no indication of recent anthropogenic pollution in water and sediment. Higher concentrations of DOC in water as well as phosphorus and some other elements in the lake sediment can be a consequence of input of natural organic matter to the lake water.     

Spatial and Temporal Comparison of Polycyclic Aromatic Hydrocarbons and Spheroidal Carbonaceous Particles in Remote European Lakes

Spheroidal carbonaceous particles (SCP) and polycyclicaromatic hydrocarbons (PAH) have been measured in the dated sediment cores of 10 remote lakes distributed across Europe. The geographic trends were evaluated by examination of the superficial sediment fluxes and total sediment inventories. The highest levels of both markers were observed in the Eastern European lakes whereas the minimal values corresponded to the lake located in the Arctic. However, this SCP-PAH correlation was not observed after exclusion of the end member lakes from the series. The temporal trends of both pollutant markers are consistent with the history of pyrolytic emissions over Europe. However, the downcore SCP distributions are shorter than the PAH profiles in nearly all lakes. The differences are probably related to the different size particle fractions involved in the measurement of each marker, >5 and >1 m for SCP and PAH, respectively. Thus, the two proxies probably reflect pollution inputs from closer (SCP) and more distant sites (PAH).     

Comparison of PM2.5 and PM10 in A Suburban Area in Korea During April, 2003

Airborne particulate matter (PM) concentrations were measured in Iksan, a suburban area in South Korea during April, 2003. PM_2.5 (particles with an aerodynamic diameter less than 2.5 μm) and PM₁₀ (particles with an aerodynamic diameter less than 10 μm) samples were collected, and the chemical characteristics of particles were examined for diurnal patterns, yellow dust/rainfall influences, and scavenging effects. Average concentrations of PM_2.5 and PM₁₀ mass measured were 37.3 ± 16.2 μg m⁻³ and 60.8 ± 29.5 μg m⁻³, respectively. The sum of ionic chemical species concentrations for PM_2.5 and PM₁₀ was 16.9 ± 7.3 and 23.1 ± 10.1 μg/m³, respectively. A significant reduction in PM mass concentrations during rainfall days was observed for coarse mode (PM_{2.5 − 10}) particles, but less reduction was found for fine (PM_2.5) mass concentration. SO₄ ²⁻, NH₄ ⁺, and K⁺ predominated in fine particulate mode, NO₃ ⁻ and Cl⁻ predominated in fine particle mode and coarse particle mode, but Na⁺, Mg²⁺, and Ca²⁺ mostly existed in coarse mode. The high concentration of ammonium due to local emissions and long-range transport neutralized sulfate and nitrate to ammonium sulfate and ammonium nitrate, which were major forms of airborne PM in Iksan. Average mass concentrations of PM₁₀ in daytime and at night were 57.6 and 70.0 μg m⁻³, and those of PM_2.5 were 35.4 and 42.5 μg m⁻³, respectively. NO₃ ⁻ and Cl⁻ in both PM_2.5 and PM₁₀ were about double at night than in the daytime, while the rest of the chemical species were equal or a little higher at night than in the daytime. The results suggest the formation of ammonium nitrate and chloride when high ammonia concentration and low air temperature are allowed. Backward air trajectory analyses showed that air masses arriving at the site during yellow dust period were transported from arid Chinese regions, which resulted in high concentrations of airborne PM mass concentrations. In the meantime, air mass trajectories during a rainfall period were mostly from the Pacific Ocean or the East China Sea, along with a relatively low PM concentration.     

Numerical simulation of surfactant-enhanced remediation of heterogeneous aquifer contaminated with nonaqueous phase liquids

A three-dimensional, multiphase, multicomponent compositional simulator was employed to simulate nonaqueous phase liquid (NAPL) migration during surfactant-enhanced aquifer remediation (SEAR) in spatially correlated heterogeneous fields. Aquifer heterogeneity was accounted for by considering the permeability to be a spatially random variable, and a geostatistical method was used to generate random distributions of the permeability. Spatial distributions of saturations in the NAPL and temporal changes of organic recovery, effluent concentrations of organics and surfactant, and pressure drop at the injection well for heterogeneous aquifers were compared with those in a homogeneous aquifer to examine the effects of different levels of heterogeneity. Variations in permeability fields have a pronounced effect on the organic recovery efficiency due to the long-term persistence of nonaqueous phase liquid and additional dispersion. Permeability heterogeneity also leads to the tailing off of effluent organic concentrations and significant loss in injectivity over the remediation period. For a small slug of surfactant, surfactant-enhanced remediation resulted in a relatively small improvement in the recovery of NAPL, especially in highly heterogeneous aquifers. Migration of high-concentration organic plumes to other layers by crossflow was also found to have a significant influence on SEAR behavior.