Mineral Matter Concentrations Research Articles

Atributos produtivos e nutricionais da forragem hidropônica de milho, em diferentes estágios, cultivada em substratos de capim-elefante e serragem de madeira

Abstract The objective of this study was to evaluate the productive and nutritional attributes of hydroponic corn forage grown on elephant grass and wood sawdust substrates at different stages. Two treatments (T) with different substrates were established: T1 - chopped and dehydrated elephant grass and T2 - wood sawdust. Forage samples were collected 13 and 20 days after sowing to evaluate seedling development, biomass production, and nutritional composition. The elephant grass substrate promoted better seedling development and greater biomass production and concentration of mineral matter at 13 days, whereas wood sawdust promoted a greater concentration of dry matter, crude protein, lignin, and non-fibrous carbohydrates (P < 0.05). The elephant grass substrates resulted in greater seedling height, production of green biomass, and concentrations of mineral matter, crude protein, and ether extract at 20 days, while wood sawdust promoted greater root length and greater concentrations of dry matter, acid detergent fiber, and lignin (P < 0.05). Elephant grass substrate and collection for 13 days promoted better production of hydroponic forage and its nutritional composition.

Valor nutritivo e características fermentativas da silagem de milheto com diferentes níveis de casca de café

ABSTRACT: The research was conducted to test the hypothesis that the inclusion of coffee husk (Coffea sp.) would improve the fermentative characteristics and quality of pearl millet silage (Pennisetumglaucum). Thus, the objective was to assess the effect of the inclusion of different levels of coffee husk in pearl millet silage on the chemical composition, fermentative characteristics and degradability in situ of silage. The experimental design used was completely randomized and the treatments consisted of the silage of the whole pearl millet plant with the inclusion of increasing levels of coffee husk: 0%, 7%, 14% and 21%, based on natural matter. After 60 days of fermentation, the silages were evaluated for chemical characteristics, fermentative, degradability in situ dry matter (DM) and neutral detergent fiber (NDF). The inclusion of coffee husk did not alter (P > 0.05) the contents of crude protein (11.94%), NDF (44.89%) and total digestible nutrients (65.09%). There were increases in the concentrations of DM and fiber in acid detergent, accompanied by a reduction in the concentrations of mineral matter and ether extract, as the proportion of coffee husks in silages increased. There was an increase in the lignin content up to the level of 7.59% inclusion of the coffee husk. There was no effect of the inclusion of the coffee husk on the pH of the silage (3.60). However, the inclusion of coffee husk resulted in a reduction in temperature, gas losses, and degradability in situ of silage DM and NDF. It is recommended to include coffee husk up to the level of 14.0% of the natural matter to improve the fermentation pattern and the quality of the pearl millet silage.

Inclusion of exogenous enzymes in feedlot cattle diets: Impacts on physiology, rumen fermentation, digestibility and fatty acid profile in rumen and meat

The objective of this study was to evaluate if the inclusion of a blend composed of exogenous enzymes (amylase, protease, cellulase, xylanase and beta glucanase) in the individual and combined form in the feedlot steers diet has benefits on the physiology, rumen fermentation, digestibility and fatty acid profile in rumen and meat. The experiment used 24 animals, divided into 4 treatments, described as: T1-CON, T2-BLEND (0.5 g mixture of enzyme), T3-AMIL (0.5 g alpha-amylase), T4-BLEND+AMIL (0.5 g enzyme blend+ 0.5 g amylase). The concentration of mineral matter was higher in the meat of cattle of T4-BLEND+AMIL. A higher proportion of monounsaturated fatty acids was observed in the T3-AMIL group when compared to the others. The percentage of polyunsaturated fatty acids was higher in the T2-BLEND and T4-BLEND+AMIL compared to the T1-CON. The combination of exogenous enzymes in the diet positively modulate nutritional biomarkers, in addition to benefits in the lipid and oxidative profile meat.

Promising biological methods for treating oil-contaminated soils

The article analyses promising methods for treatment of oil-contaminated soils. The main tried and tested groups of oil-contaminated soil treatment methods are reviewed and concrete examples are given. The most promising group of currently used methods has been identified. The authors performed an analysis of accidents accompanied by an accidental oil or oil product spill, considered the main causes of such accidents and their consequences for the environment components using concrete examples of real organizations. The analysis established that the most frequent accidents are caused by failure and depressurization of devices as well as by human errors expressed in the violation of industrial safety requirements and the requirements of the organization of hazardous works. The analysis of the main methods of oil-contaminated soil treatment is presented, the main drawbacks and the negative impact on the environment components are identified. Based on the obtained data, the most promising method with the highest efficiency and the least impact on the components of the environment has been identified. The main groups of methods used to clean the contaminated soil are chemical and biological methods. It is revealed that the most promising group of methods are biological methods, which is associated with a minimal impact on the atmospheric air, as well as a high degree of purification. In addition, modern bioremediation and phytoremediation methods are considered in the article. The considered methods are based on the use of modern biopreparations and agrotechnical methods. These methods are based on an integrated approach, which leads to high efficiency. However, it should be noted that a high degree of treatment requires the maintenance of certain soil parameters such as temperature, moisture, acidity and mineral matter concentration.

Relationship between indoor and outdoor size-fractionated particulate matter in urban microenvironments: Levels, chemical composition and sources

Exposure to particulate matter (PM) has been associated with adverse health outcomes, particularly in susceptible population groups such as children. This study aims to characterise children's exposure to PM and its chemical constituents. Size-segregated aerosol samples (PM0.25, PM0.25–0.5, PM0.5–1.0, PM1.0–2.5 and PM2.5–10) were collected in the indoor and outdoor of homes and schools located in Lisbon (Portugal). Organic and elemental carbon (OC and EC) were determined by a thermo-optical method, whereas major and trace elements were analysed by X-Ray Fluorescence. In school, the children were exposed to higher PM concentrations than in home, which might be associated not only to the elevated human occupancy but also to outdoor infiltration. The pattern of PM mass size distribution was dependent on the location (home vs. school and indoor vs. outdoor). The presence of EC in PM0.25 and OC in PM0.25–0.5 was linked to traffic exhaust emissions. OC and EC in PM2.5–10 may be explained by their adhesion to the surface of coarser particles. Generally, the concentrations of mineral and marine elements increased with increasing PM size, while for anthropogenic elements happened the opposite. In schools, the concentrations of mineral matter, anthropogenic elements and marine aerosol were higher than in homes. High mineral matter concentrations found in schools were related to the close proximity to busy roads and elevated human occupancy. Overall, the results suggest that exposure to PM is relevant and highlights the need for strategies that provide healthier indoor environments, principally in schools.

Contemporary and Historical Atmospheric Deposition of Arsenic and Selenium in the Athabasca Bituminous Sands Region.

Selenium (Se) is one of the trace elements that is enriched in bitumen. To assess the importance of atmospheric Se deposition from mining and upgrading of bituminous sands in northern Alberta, Canada, Sphagnum moss was obtained from 25 bogs near industrial operations. The average Se concentration in moss near industries (58 ± 13 μg/kg; n = 75) was greater than in remote sites in Alberta (29-50 μg/kg), but comparable to bogs in central regions of the province and lower than bogs in southern Ontario (121-244 μg/kg) or the west and east coasts (230-285 μg/kg). In bog vegetation and peat, arsenic (As) concentrations and accumulation rates are 10 times greater at the industrial site (MIL) compared to the control site (UTK), but this is proportional to the differences in scandium (a surrogate for mineral matter concentrations), which points to dust as the predominant As source. An age-dated peat core collected near industries revealed that both Se and As deposition have declined in recent years. A peat core from UTK provided a record of atmospheric deposition dating back over 2700 years, indicating that As and Se deposition in northern Alberta increased considerably in the early 19th century and then went into decline during ∼1950-1970.

Is the Eggshell Quality Influenced by the Egg Weight or the Breeder Age?

For a long time, it has been said that eggshell quality decreases as eggs increase in size, but this increase is seen as the breeder age advances. Therefore, the present study aimed to evaluate the age and egg weight effect on Cobb 500 broiler breeders on eggshell quality. The quality measures tested were eggshell and mineral matter percentage, eggshell surface, shape and eggshell index, eggshell and membrane thickness and specific gravity. Eggs from 27, 31, 36, 40, 46, 48, 53, 58 and 63 week-old breeders were classified as eggs with a constant weight ranging from 63.8 ± 0.2; and eggs with increasing weight, according to age, being: 55.8g; 60g; 62.2g; 64.2g; 65.2g, 66.6g, 68.1g, 69.9g and 72.5g, respectively. The eggs weight did not influence the eggshell percentage and the specific gravity in seven of the nine tested ages, while for mineral matter in six of the nine studied ages. The shape and shell index, shell and membrane thickness are characteristics independent of egg weight. As the Cobb 500 broiler breeder age advanced, the mineral matter concentration and specific gravity maintained constant, the membrane thickness (R2>70) reduced, and other studied variables were influenced in the same way for both treatments. Thus, the eggshell quality decrease with the advancing age cannot be attributed solely to the increase of egg weight with consequent increase in the eggshell volume and the surface, but there are also age-related factors.

Home composting using different ratios of bulking agent to food waste

The negative environmental impacts associated with home composting may be due to the absence of a defined operation criteria for the degradation process. In addition to the potentially low environmental impact in terms of energy and water usage, which is minimal to the manufacture of the composting unit and avoiding the processing and transportation of waste or byproduct, composting at home can also promote a reduction in the emission of unpleasant gases. The proportion of the food waste and bulking agents in the composting mixture may be decisive to fulfill good practices of waste stabilization. The aim of this study was to investigate how different ratios of bulking agent and organic household waste can affect the progress and outcome of the composting process. Three treatments, varying in the ratio of rice husk: raw fruit and vegetable leftovers (70:30, 50:50, 30:70; v:v) were used in a home composting system on a pilot scale. Results show that the proportion of starting materials used in the composting mixture influenced the degradation of organic matter, nitrogen dynamics of the process and its toxicity on germinating plants. The proportions with greater amounts of food waste had higher concentrations of mineral matter, higher peak temperature, and a better initial carbon-to-nitrogen ratio, while the proportion containing 70% of bulking agent lacked odors and leachate generation and showed a low nitrogen loss. A higher proportion of food waste presented better conditions for microbiological development and less time to obtain characteristics of matured composts. A higher proportion of bulking agents resulted in favorable conditions for household handling and less potential for environmental impacts.

Impact of Sulphur Content on Coal Quality at Delta Plain Depositional Environment: Case study in Geramat District, Lahat Regency, South Sumatra

The research was conducted in Geramat District of Lahat Regency, South Sumatra. An evaluation of the geological condition of the research area shown that the coal deposits were found in Muara Enim Formation as a coal-bearing formation. The method used was literature study, field observation and the laboratory work includes proximate and petrography analysis. The aim of this research is to determine the environmental condition of coal based on the change of total sulphur content and to know the relation between ash content to calorific value. As the result of proximate analysis conducted on five samples of coal, the research area obtained total sulphur (0,21-1,54% adb), ash content (3,16 - 71,11% adb) and gross calorific value (953 - 5676 cal/g. adb). Based on the result of maceral analysis showed the maceral percentage of coal in research area composed by vitrinite (77,8-87,4 %), liptinite (0,6 %), inertinite (8,0 – 17,6 %) and mineral matter concentration in the form of pyrite (1,6-4,6 %). The average reflectance value of vitrinite (Rv) of coal in the research area (0.54%). the results analysis shows that the coal in Muara Enim Formation on the research area is in the transitional lower delta plain depositional environment phase. Any changes in the sedimentary environment affected by sea water will be followed by changes in total sulphur and the higher ash content, on the contrary, the lower calorific value of the coal.

Road traffic and sandy playground influence on ambient pollutants in schools

Urban air pollution has a greater impact on children's health compared to adults. In the framework of the BREATHE (BRain dEvelopment and Air polluTion ultrafine particles in scHool childrEn) project, the present work studies the impact of road traffic and the presence of sandy playgrounds on the outdoor air quality around schools. Four schools were selected for intensive campaigns of one month. PM2.5 samples were collected daily from 8:00 to 20:00 and chemically analysed. Real time measurements of NOx, black carbon (BC), PM1, PM2.5 and PM10 concentrations were carried out. Sand samples from five school playgrounds were characterized. The results confirm the representativeness of the general BREATHE project campaigns (eight weekdays measurements at each of the 39 schools). NOx, BC and PMx concentrations were higher in the school located nearest to traffic in the city centre with the daily pattern reflecting the traffic rush hours. The NOx concentrations were found to decrease with distance to the main road. The road traffic influence on ambient pollutants was higher on weekdays than weekends. The PM10 concentrations at one of the schools were mainly driven by the influence of the sandy playground, with peaks up to 25, 57 and 12 times higher than night background concentrations during mid-morning break, lunch break and end of school day, respectively. The airborne mineral matter concentrations registered at this school further confirm this origin. Nevertheless the influence of the re-suspension from the sandy playground was very local and decreased drastically within a short distance. The possible impact of the use of the private car for children's commuting on the outdoor air quality of the schools cannot be quantitatively assessed due to the overlapping with the rush hour of the city.

Cyclic sedimentation pattern in Lake Veetka, southeast Estonia: a case study

Abstract A sediment core from Lake Veetka, southeast Estonia, 1077 cm in length and covering 10,500 calibrated years, was examined using loss-on-ignition, grain-size distribution and AMS 14C dating to reconstruct depositional dynamics. The studied core, recovered from the northern part of the lake, shows a cyclic pattern of organic and mineral matter concentration with cycle durations of 100-400 years. Cyclicity is displayed better in sediments laid down between 9,200 and 5,600 cal BP. Within two time windows (5,600-5,100 cal BP and from 1,200 cal BP to the present), sediment composition changed drastically on account of a high and fluctuating mineral matter content, obviously driven by different factors. Little Ice Age cooling is characterised by the highest proportion of mineral matter, and the Medieval Warm Period is typified by high organic matter content. The cyclic change of organic and mineral matter has been related to climate dynamics, most likely an alternation of wet and dry conditions, changes in the water level of the lake and differences in bioproduction

Joint analysis of continental and regional background environments in the western Mediterranean: PM<sub>1</sub> and PM<sub>10</sub> concentrations and composition

Abstract. The complete chemical composition of atmospheric particulate matter (PM1 and PM10) from a continental (Montsec, MSC, 1570 m a.s.l.) and a regional (Montseny, MSY, 720 m a.s.l) background site in the western Mediterranean Basin (WMB) were jointly studied for the first time over a relatively long-term period (January 2010–March 2013). Differences in average PMX concentration and composition between both sites were attributed to distance to anthropogenic sources, altitude, and different influence of atmospheric episodes. All these factors result in a continental-to-regional background increase of 4.0 μg m−3 for PM10 and 1.1 μg m−3 for PM1 in the WMB. This increase is mainly constituted by organic matter, sulfate, nitrate, and sea salt. However, higher mineral matter concentrations were measured at the continental background site owing to the higher influence of long-range transport of dust and dust resuspension. Seasonal variations of aerosol chemical components were attributed to evolution of the planetary boundary layer (PBL) height throughout the year, variations in the air mass origin, and differences in meteorology. During warmer months, weak pressure gradients and elevated insolation generate recirculation of air masses and enhance the development of the PBL, causing the aging of aerosols and incrementing pollutant concentrations over a large area in the WMB, including the continental background. This is reflected in a more similar relative composition and absolute concentrations of continental and regional background aerosols. Nevertheless, during colder months the thermal inversions and the lower vertical development of the PBL leave MSC in the free troposphere most of the time, whereas MSY is more influenced by regional pollutants accumulated under winter anticyclonic conditions. This results in much lower concentrations of PMX components at the continental background site with respect to those at the regional background site. The influence of certain atmospheric episodes caused different impacts at regional and continental scales. When long-range transport from central and eastern Europe and from north Africa occurs, the continental background site is frequently more influenced, thus indicating a preferential transport of pollutants at high altitude layers. Conversely, the regional background site was more influenced by regional processes. Continental and regional aerosol chemical composition from the WMB revealed (a) high relevance of African dust transport and regional dust resuspension; (b) low biomass burning contribution; (c) high organic matter contribution; (d) low summer nitrate concentrations; and (e) high aerosol homogenization in summer.

Wetting of Carbonaceous Fuel Particles by Molten Alkali Metal Hydroxide and Carbonate Electrolytes

The method of capillary rise in a random bed of particles, as measured by the rate of mass increase of packed beds of sample particles, was applied to measurements of the relative wetting characteristics of selected particulate carbonaceous fuels by different molten electrolytes of general interest in electrochemical energy applications. In particular, a series of activated chars as well as Pittsburgh (#8) and Beulah-Zap lignite coal samples (both as-received and pyrolyzed) were investigated. It was found that the wetting coefficient (k = cos θ) of the molten electrolytes (NaOH, KOH, a binary NaOH/KOH eutectic mixture, and a ternary alkali metal carbonate eutectic) on an activated char all increased with the temperature in an approximately linear fashion over the limited temperature ranges investigated. It was also found that the wetting coefficient increased with decreasing particle size. This was observed for both the activated chars and the coal samples. In addition, it was found that pyrolysis significantly improved the wetting of both coals investigated. In the current work, this was attributed to increasing the concentration of mineral matter in the resultant pyrolyzed samples at the liquid−solid interface.

Comparison of methods to obtain ash from coal of the Southwest of Colombia

The method for concentration of mineral matter at low temperature (about 250 °C), called Low Temperature Ash (LTA) was applied to a sample of coal from the mine “Las Mercedes” located in Colombia southwestern. This method provides better information about the content of mineral matter in natural coal (NC), removing the organic matter more efficiently without significant transformations of mineral phases present in that coal. These results were observed through Mossbauer spectra and X-ray patterns taken from samples of NC, (LTA) and the conventional method of High Temperature Ash (HTA). The results show that the LTA process provides more representative data of the mineral phases for natural coal than that using the conventional HTA process.

The inorganic geochemistry of a peat deposit on the eastern Qinghai-Tibetan Plateau and insights into changing atmospheric circulation in central Asia during the Holocene

Peat records enable the reconstruction of changes in the global biogeochemical mineral dust cycle and the detection of variations in atmospheric circulation patterns during the Holocene. They can therefore provide a key tool for understanding the relationship between the geochemical dust cycle and past climate change. Here, we present the first detailed study of the inorganic geochemistry of a peat core collected at an altitude of 3500m from the Hongyuan peatland, on the eastern Qinghai-Tibetan Plateau, and test its potential as an archive of atmospheric dust deposition. We find that the low accumulation rates of the peat and the presence of the extensive dust sources of northern China in the vicinity of the study site lead to approximately five times higher concentrations of mineral matter compared to temperate ombrotrophic peats. A detailed geochemical assessment of the core and surface samples from local and non-local dust sources, as well as of the hydrology and hydrochemistry of the surrounding waters, suggests that external and internal post-depositional processes have not affected the record of lithogenic elements, including the rare earth elements (REE), Sc, Y and Th.Changes in Ti-normalized major element profiles, La/Yb, Y/Tb and the Eu anomaly identify seven major shifts among the dominant dust sources and therefore potential changes in atmospheric circulation patterns. Bivariate plots using the REE-based tracers La/Yb, Y/Tb, La/Th, Y/Er, Sc/La, Th/Sc and Th/ΣREE suggest that the Taklamakan desert and the Chinese loess plateau in northern China were the dominant non-local dust sources to the peat. Local dust input dominated throughout the early Holocene until 4.9kyr BP. Increased dust input from the non-local sources thereafter suggests an enhanced influence of winds associated with the East Asian winter monsoon and the Westerly jet throughout most of the late Holocene. Sharp increases in non-local dust fluxes between 3.1–2.7 and between 1.3–0.9kyr BP suggest a particular strengthening of these wind systems during these times, in agreement with the organic characteristics of the core.Our results show that the Hongyuan peat is a reliable archive to study dust deposition in central Asia and allows the identification of changes in atmospheric circulation patterns and in the larger climatic arrangements of the monsoon system in this region during the Holocene.

Vertical evolution of petrographic and organic geochemical parameters in Las Dueñas mire (Cantabrian Coast, North Spain)

Las Dueñas mire has developed on a flat siliceous substrate over the Holocene. The sedimentary cover has a thickness of around 50 cm and the mire comprises a surface area of 27 ha. A core sample obtained using a manual probe was split into sub-samples of around 3–4 cm thickness for petrographic and organic geochemical analysis. The fen originated by minerogenesis and contains a high concentration of mineral matter throughout its profile which decreases towards the top. The present day vegetation is dominated by Sphagnum . A variety of transparent textinite with intense fluorescence is evidence of the low maturity of the profile, which is also confirmed by the presence of low reflecting huminite of the A variety (Hr ~ 0.15%). The fluorescence spectra of sporinite and cutinite are similar and, compared with those of transparent textinite, they have a lower intensity and are shifted to higher wavelengths. The low maturity of the organic matter is also confirmed by the presence of unstable ββ hopane configurations, the abundance of hopene, and the presence of functionalized hopanoids, steroids and other triterpenoids. The evolution of the geochemical parameters in the peat profile indicates the presence of more humid conditions in the top 4 cm and at a depth of 11–15 cm. These periods are characterized by a high Sphagnum /higher plant contribution as deduced from the n- alkane ratios. The low reflectance of huminite at the depth of 11–15 cm could also support less oxidizing condition. The sediment at a depth of 22 cm where peaty matter starts to accumulate has been dated as 9603 cal BC, whereas the plant fraction at the same depth dates back to a maximum of 200 years. Sediment reworking derived from radiocarbon dates indicates that this fen is not suitable for palaeoenvironmental studies. ►Organic petrology and geochemistry of Las Dueñas mire (North Spain) is included. ►The mire is at a coastal cliff location. It is a low maturity high ash profile (49 cm depth). ►The sediment age is around 9500 cal BC whereas the plant material dates back 200 years. ►Geochemical parameters indicate more humid conditions at the top of the profile

Recent patterns of sediment accumulation in a small closed eutrophic lake revealed by the sediment records

A short-core palaeolimnological investigation was undertaken with the aim ofacquiring knowledge of sediment deposition. Analyses of the lithological composition of sediments from the whole-lake basin were performed on the small eutrophic L. Linajarv (northern Estonia) and the concentrations of mineral and organic matter were measured on 647 sub-samples from 14 sediment cores. The accumulation rate of the sediment sequences was established and C/N ratios of organic matter in some cores were recorded. Results indicate that the water depth, basin slopes and distance to the shore have the most important impact on the physical sediment properties. It was shown that variations in the mineral matter concentrations were influenced by the changes in deposition conditions in the areas with steep slopes. The study indicated that more objective information about the sedimentation mechanisms is obtained using analysis of the concentration ratio of mineral and organic matter since it reduces the implied role of diagenetic compaction.

Microbial alteration of organic matter of humic coal during biological desulphurisation

The biodegrading influence of biological desulphurisation on bituminous coal and its density fractions was investigated using gas chromatography–mass spectrometry for organic matter alteration and atomic absorption for the assessment of changes in several trace element concentrations. Changes in extract group composition were assessed by comparing the contents of aliphatic, aromatic and polar compounds separated by preparative thin layer chromatography. Aliphatic compounds show extensive alteration due to biodegradation, mainly removal of n-alkanes and lighter acyclic isoprenoids from extracts. The sterane distribution was strongly affected while hopane/moretane distributions show minor changes. Aromatic hydrocarbons were less influenced but some changes were found. It can be assumed that the degree of biodegradation of density fractions increases with increasing concentration of mineral matter since density fractions with lower mineral concentration show smaller changes as a result of biodegradation than those with higher content of minerals. Reduction of concentrations of the following trace elements occurred: beryllium, chromium, zinc, gallium, cadmium, cobalt, lithium, manganese, copper, molybdenum, nickel, lead, and vanadium. The content decrease of an element is not influenced by its geochemical properties. An equally important factor seems to be bonding to organic and inorganic coal substances.

Determination of Pb in the ash fraction of plants and peats using the Energy-dispersive Miniprobe Multielement Analyser (EMMA)

Dry ashing at 550 °C was used to pre-concentrate Pb in peat and plant material prior to analysis using the Energy-dispersive Miniprobe Multielement Analyser (EMMA). Using approximately 1 g of starting material, precise determination of the ash content using a conventional laboratory balance (±1 mg precision) was possible provided the mineral matter concentration exceeded about 3.5%, yielding approximately 35 mg of ash for analysis. To assess possible loss of Pb upon ashing, certified plant reference materials and independent analytical methods (ICP-MS of acid digests and EMMA analysis of whole peats) were used for comparison. No significant systematic loss of Pb occurred during ashing. The accuracy of Pb determinations using dry ashing was within 10% in plant materials containing as little as 0.5 µg g–1 (estimated from certified plant material). The EMMA determinations of Pb in peat by dry ashing generally agreed with the ICP-MS analyses of acid digests within 12% down to 0.2 µg g–1. The average limit of detection for a sample containing 2% of mineral matter was 100 ng g–1, more than five times better than the detection limit obtained using EMMA analyses of whole peats. Overall accuracy and precision were better when Pb was measured by dry ashing compared to direct analysis of solid peats or plants.

Material Fluxes Across Wetland Ecotones in Northern Landscapes.

The spatial and temporal distribution of sediment, nutrients, and cations in a 2-ha wetland near Shawano, Wisconsin (USA) was used to evaluate the effect of wetland ecotones on water- and windborne fluxes at ecosystem and landscape scales. Within the wetland ecosystem the ecotones studied were beach ridges deposited by post-glacial White Clay Lake, and stream levees deposited by a second-order stream flowing through the wetland. Snow, soil, and surface water data collected from a 52-point sampling grid were geostatistically analyzed to derive contour plots of within-wetland concentrations. Wind-blown snow form the frozen lake surface accumulated in the wetland behind a low beach ridge to a depth of >65 cm, nearly 7 times the depth at wind-protected areas of the wetland. As a result of this snow accumulation, areas to the lee of the beach ridge annually received 10% more water and 1.5% more inorganic N from direct precipitation than did other areas of the watershed. The use of geostatistical plots to analyze wetland surface waters revealed that: (1) within-wetland spatial variability was high on every sampling date except early snowmelt; (2) on a given sampling date, concentration patterns differed for different elements, sometimes substantially; (3) with the exception of NO3 -N, the spatial patterns for a given material changed considerably over time; and (4) many of these spatial patterns were interpretable on the basis of observed water flow patterns and wetland ecology. In general, there was a decrease in the concentrations of inorganic solids and most ions, and an increase in Ca++ and chemical oxygen demand with distance from the stream. Overbank fluxes contributed P to the wetland during spring and fall floods, but diluted ambient P concentrations during snowmelt events. During snow-free periods there was a sharp gradient in NO3 -N concentrations from a streamside value of °5 mg/L to <0.4 mg/L in wetland areas >45 m from the stream. Measurement of the concentration gradient perpendicular to the stream indicated NO3 -N disappearance rates of 6.6 g/100 m of distance during the spring flood. Soil concentrations of mineral matter and P were highest in areas of the wetland closest to the stream; soil concentrations of ammonium and nitrate were spatially disaggregated, and related to levee elevation. At the watershed scale the wetland retained and/or denitrified 15.2% of the total solids, 13.7% of the N, and 14.2% of the P fluxes from the watershed, thus benefitting the water quality of White Clay Lake.