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824 Ergebnisse:

The cultural eutrophication of Lac la Biche, Alberta, Canada: a paleoecological study
Canadian Journal of Fisheries and Aquatic Sciences (1970)
D W Schindler, Alexander P Wolfe, Rolf Vinebrooke, Angela Crowe, Jules M Blais, Brenda Miskimmin, Rina Freed, Bianca Perren

A multiproxy paleoecological investigation of Lac la Biche, a large boreal lake in northeastern Alberta, Canada, revealed that the lake was eutrophic before European settlement but has undergone additional cultural eutrophication in the past 30 to 50 years. Annual fluxes to sediments of phosphorus, nitrogen, carbon, and inorganic sediments have increased with time. A declining N–P ratio has increasingly favored nitrogen-fixing cyanobacteria. Increased deposition of microbial pigments and diatom frustules and a recent shift in diatom species also indicate increasing eutrophication. Biogenic silica increased with time, but there is no evidence of a near-surface decline that would indicate silica limitation. Stable isotopes suggest that an increasing proportion of carbon deposited in sediments is of in-lake origin, indicating increased productivity. In the basin nearest the town of Lac La Biche, an increase in d15N followed the construction of the sewage treatment plant, but more recently, decreased d15N in both basins suggests that nitrogen fixation has become a more important source of nitrogen. Despite documented damage to the fishery of the lake, zooplankton fossils do not show evidence of a strong trophic cascade. The study illustrates the power of a multiproxy approach in obtaining reliable paleolimnological conclusions.

Balancing the Nitrogen Derived from Sewage Effluent and Fertilizers Applied with Drip Irrigation
Water, Air, & Soil Pollution (2017)
Lijun Guo, Jiusheng Li, Yanfeng Li, Di Xu

Balancing the nitrogen derived from sewage effluent and fertilizers is essential for efficiently utilizing the nitrogen and minimizing the environmental degradations when applying sewage effluent. Pot experiments of maize (Zea mays L.) under drip irrigation were performed using 15N labeled urea to quantify the nitrogen balances of sewage effluent and fertilizers. Field experiments were conducted to confirm the findings of pot experiments. Four nitrogen rates ranging from 0 to 2.64 g/pot (0–210 kg/ha equivalently) for pot experiments and from 0 to 180 kg/ha for field experiments were established applying either secondary sewage effluent (SW) or groundwater (GW). Both pot and field experiments revealed that SW irrigation boosted nitrogen uptake and yield of maize compared to GW irrigation. However, the sewage-derived effects decreased with increasing nitrogen rates. SW irrigation could facilitate the uptake of 15N labeled urea relative to GW irrigation. Nonetheless, the nitrogen containing in effluent possibly had lower uptake effectiveness than the fertilizer urea for maize, suggesting greater potential for nitrogen losses resulting from effluent nitrogen compared to urea nitrogen. The percentage utilization of effluent nitrogen declined from 43 to 34% in 2014 and 48 to 32% in 2015 as nitrogen rates increased from 0 to 2.64 g/pot. Besides, the percentages utilization of total nitrogen (including effluent and fertilizers) under SW irrigation increased from 43 to 55% in 2014 and from 48 to 55% in 2015 when the rates increased from 0 to 1.76 g/pot, and subsequently decreased to 48% in 2014 and 44% in 2015 at the rate of 2.64 g/pot. This result was strengthened by the pattern of nitrogen recovery efficiency observed in the field experiments. Overall results of pot and field experiments recommended an optimal rate of 120 kg/ha for maize under drip irrigation applying SW to maximize nitrogen use efficiency and achieve an acceptably high yield.

Burrowing and foraging activity of marsh crabs under different inundation regimes
Journal of Experimental Marine Biology and Ecology (2017)
Katelyn Szura, Richard A. McKinney, Cathleen Wigand, Autumn Oczkowski, Alana Hanson, John Gurak, Melanie Gárate

New England salt marshes are susceptible to degradation and habitat loss as a result of increased periods of inundation as sea levels rise. Increased inundation may exacerbate marsh degradation that can result from crab burrowing and foraging. Most studies to date have focused on how crab burrowing and foraging can impact the dominant low marsh plant species, Spartina alterniflora. Here we used a mesocosm experiment to examine the relationship of foraging and burrowing activity in two dominant New England crab species, Sesarma reticulatum and Uca pugilator, and the combined effect of inundation, on the dominant high marsh plant species Spartina patens using a 3×2 factorial design with three crab treatments (Sesarma, Uca, control) at two levels of inundation (low, high). Plants were labeled with a nitrogen (N) stable isotope tracer to estimate plant consumption by the two crab species. At both levels of inundation, we found that S. reticulatum had a significant negative impact on both above- and below-ground biomass by physically clipping and uprooting the plants, whereas U. pugilator had no significant impact. Low inundation treatments for both crab species had significantly greater aboveground biomass than high inundation. Stable N isotope tracer levels were roughly the same for both S. reticulatum and U. pugilator tissue, suggesting that the impact of S. reticulatum on S. patens was not through consumption of the plants. Overall, our results suggest the potential for S. reticulatum to negatively impact marsh stability, and that effects of crab foraging behavior may be heightened by increased inundation.

Aged acidic biochar increases nitrogen retention and decreases ammonia volatilization in alkaline bauxite residue sand
Ecological Engineering (2017)
M. Esfandbod, I.R. Phillips, B. Miller, M. Rezaei Rashti, Z.M. Lan, P. Srivastava, B. Singh, C.R. Chen

Bauxite residue sand (BRS) is the primary growth medium for rehabilitating Alcoa’s residue storage areas in south-west Western Australia. Successful revegetation of highly alkaline BRS can be hindered by its low nitrogen (N) use efficiency. Biochar, a carbon (C)-rich material, has been suggested to have the potential to improve water and nutrient retention in soil. However, little is still known about the effect of biochar amendment on N use efficiency in the alkaline BRS environment. This incubation study aimed to evaluate the impact of biochars with different characteristics on N retention and dynamics in BRS. The BRS (pH 9.5 after being pre-treated with 1% gypsum and leached with water) was amended with the acidic biochar (pH 3.86; AC, from wild fire) and alkaline biochars (pH 9.58–10.8; greenwaste, GW; Jarrah, JL; mallee, ML) at a rate of 10%(w/w). The N loss via NH3 volatilization was much lower from the AC treatment (24% of di-ammonia phosphate (DAP)-N added) than the alkaline biochars treatments (76–80% of the DAP-N added). The AC treatment can retain about 73% of N added to BRS, compared with <25% in alkaline biochar treatments. This can be attributed to the acidic nature and the greater NH4+-N sorption capacity arising from the presence of a high density of the oxygen-containing functional groups on the surface of acidic biochar as revealed by the FTIR spectroscopy. These results imply acidic biochar can be used as an effective amendment for increasing N use efficiency by plants growing in alkaline BRS.

Geochemical distribution and fate of arsenic in water and sediments of rivers from the Hokusetsu area, Japan
Journal of Hydrology: Regional Studies (2017)
Emilie Even, Harue Masuda, Takahiro Shibata, Aki Nojima, Yusuke Sakamoto, Yusuke Murasaki, Hitoshi Chiba

STUDY REGION Hokusetsu Region in Osaka, Japan. STUDY FOCUS The As contamination was investigated through the geochemical mapping and analysis of river waters and bed sediments over an area of 440km2. Sulfur from sulfides in rocks and dissolved sulfates in water were compared via isotopic analysis to assess their origin and the subsequently released As. The fate of As (transport, binding on settling particles) was evaluated through the total and dissolved fractions of As and trace metals Fe, Mn and Al in river waters. NEW HYDROLOGICAL INSIGHTS FOR THE REGION The geochemical mapping showed that As in river water exceeded the maximum limit concentration of 10ppb in several places. The highest As levels (waters and sediments) correlated well with the surface geologies, concentrating in a halo around granitic intrusion and nearby faults. The isotopic analysis of sulfur revealed the occurrence of two kinds of sulfide mineralizations responsible for As contamination: one from Late Paleozoic submarine volcanism in sedimentary rocks, and one from Late Cretaceous igneous activities in contact-metamorphosed rocks disseminated with sulfides. The transport of As along river courses occurred mainly as a dissolved species rather than absorbed on Fe/Mn/Al particles, signifying the least role of iron oxy-hydroxides in As adsorption.

Examining nitrogen dynamics in the unsaturated zone under an inactive cesspit using chemical tracers and environmental isotopes
Applied Geochemistry (2017)
Claudia Varnier, Ricardo Hirata, Ramon Aravena

This study evaluates the dynamics of nitrogen compounds generated by infiltration of wastewater from an inactive cesspit in the unconfined and sedimentary Adamantina Aquifer in Urânia, Brazil. A monitoring station, consisting of an 11.2 m well (1.8 m in diameter) with an array of 12 tensiometers and 12 suction lysimeters, was installed to monitor the shallow unsaturated zone from 0.5 to 9 m depth. A monitoring well was also installed below the water level to monitor the shallow aquifer. High amounts of ammonium (up to 96 mg/L NH4+-N) and nitrate (up to 458 mg/L NO3−-N) were observed in the unsaturated zone porewater which is comparable to active septic systems effluents. The distribution of NO3−, Cl− and Na+, typical constituents of sewage effluents, varied seasonally and spatially, which is correlated with changes in infiltration rates between the wet and dry seasons and with hydraulic conductivity variations in interlayered sandy and clayey sediments. A detailed monitoring of porewater geochemistry demonstrated the occurrence of several important reactions affecting nitrogen dynamics in the unsaturated zone: i) oxidation of organic matter, ii) ammonification, iii) nitrification, iv) methanogenesis, v) denitrification and likely, vi) sulfate reduction. The changes in nitrogen compound distribution and δ15NNO3 and δ18ONO3 values in porewater, in association with the N2O concentration and δ15NN2O and δ18ON2O signatures in gas samples, indicate the occurrence of nitrification and denitrification, suggesting the coexistence of reducing and oxidizing microsites in the unsaturated zone. This study indicated that cesspits can generate a significant amount of nitrate even a few years after being inactivated which can represent a potential long-term source of nitrate to groundwater in highly populated areas.

Examining nitrogen dynamics in the unsaturated zone under an inactive cesspit using chemical tracers and environmental isotopes
Applied Geochemistry (2017)
Claudia Varnier, Ricardo Hirata, Ramon Aravena

This study evaluates the dynamics of nitrogen compounds generated by infiltration of wastewater from an inactive cesspit in the unconfined and sedimentary Adamantina Aquifer in Urânia, Brazil. A monitoring station, consisting of an 11.2 m well (1.8 m in diameter) with an array of 12 tensiometers and 12 suction lysimeters, was installed to monitor the shallow unsaturated zone from 0.5 to 9 m depth. A monitoring well was also installed below the water level to monitor the shallow aquifer. High amounts of ammonium (up to 96 mg/L NH4+-N) and nitrate (up to 458 mg/L NO3−-N) were observed in the unsaturated zone porewater which is comparable to active septic systems effluents. The distribution of NO3−, Cl− and Na+, typical constituents of sewage effluents, varied seasonally and spatially, which is correlated with changes in infiltration rates between the wet and dry seasons and with hydraulic conductivity variations in interlayered sandy and clayey sediments. A detailed monitoring of porewater geochemistry demonstrated the occurrence of several important reactions affecting nitrogen dynamics in the unsaturated zone: i) oxidation of organic matter, ii) ammonification, iii) nitrification, iv) methanogenesis, v) denitrification and likely, vi) sulfate reduction. The changes in nitrogen compound distribution and δ15NNO3 and δ18ONO3 values in porewater, in association with the N2O concentration and δ15NN2O and δ18ON2O signatures in gas samples, indicate the occurrence of nitrification and denitrification, suggesting the coexistence of reducing and oxidizing microsites in the unsaturated zone. This study indicated that cesspits can generate a significant amount of nitrate even a few years after being inactivated which can represent a potential long-term source of nitrate to groundwater in highly populated areas.

Interactive effects of irrigation and nitrogen fertilizer on yield, nitrogen uptake, and recovery of two successive Chinese cabbage crops as assessed using 15N isotope
Scientia Horticulturae (2017)
Na Gao, Yu Liu, Hanqing Wu, Peng Zhang, Na Yu, Yuling Zhang, Hongtao Zou, Qingfeng Fan, Yulong Zhang

The aim of this study was to evaluate the interactive effect of irrigation and nitrogen fertilization on yield, nitrogen (N) uptake, and recovery of two successive Chinese cabbage (Brassica campestris L.) crops and to assess the residue effects of N on the 2nd season crop under greenhouse conditions. 15N-labeled urea was administered to pot-grown Chinese cabbage in the 1st season. The cabbage plants were subjected to three irrigation treatments, 60 (W1), 75 (W2), and 90% (W3) of the soil field capacity, and four N rates, 0 (N0), 0.1 (N1), 0.2 (N2), and 0.3 (N3) g N kg−1 soil. The highest yield, dry matter (DM), N uptake, %Ndff (the percentage of N derived from fertilizer), N recovery rate, and the lowest loss rate were recorded in W3 treatment. N1 treatment had the maximum values for yield, DM, N recovery rate, and the lowest N loss rate. The highest %Ndff was recorded in N2 treatment, with no significant difference observed compared to N3 treatment in the 1st season. In addition, no significant difference among the N rates was observed in the 2nd season. Besides, roots exhibited higher %Ndff values than leaves. Only 5.30–23.00% fertilizer was absorbed by the Chinese cabbage, 56.22–71.29% remained in the soil, and 13.17–37.10% was presumably lost in the 1st season. The recovery rate in the 2nd season was approximately 3.51–17.40%. Therefore, in terms of yield, nitrogen recovery, and environmental impact, W3N1 treatment was recommended as the best combination for Chinese cabbage production and this treatment showed a productive potential in the 2nd season, as well.

Human diets during the social transition from territorial states to empire: Stable isotope analysis of human and animal remains from 770BCE to 220CE on the Central Plains of China
Journal of Archaeological Science: Reports (2017)
Ligang Zhou, Sandra J. Garvie-Lok, Wenquan Fan, Xiaolong Chu

Chinese history from the Eastern Zhou to the Han Dynasty (770BCE to 220CE) witnessed a social transition from conflicting territorial states to a prosperous empire. This study investigates the effects of social changes on human diet using stable isotope analysis. Human remains (n=134) and contemporary faunal remains (n=14) from three sites located on the Central Plains of China were analyzed, and the results have shed light on human diets in the two different eras. Most individuals of the Eastern Zhou had diets based on millet and a limited amount of animal protein. The poor ate a significant amount of wheat, which may have been a response to the food pressures of their urban environment. Wheat consumption in the Han Dynasty increased significantly, likely in response to a population increase during the early imperial period, and patterns of animal protein consumption also differed from that of the Eastern Zhou. Status-related dietary variation in the two eras was reflected in the amount of wheat eaten rather than animal protein consumption. The dietary changes seen likely reflect both adaptive strategy and active change, and seem to have benefited human health in the following dynasties. The results also indicate that significant wheat consumption started in the lowest social classes, suggesting a bottom-up mode for the adoption of wheat into human diets of the area.

The adoption of pottery by north-east European hunter-gatherers: Evidence from lipid residue analysis
Journal of Archaeological Science (2017)
Ester Oras, Alexandre Lucquin, Lembi Lõugas, Mari Tõrv, Aivar Kriiska, Oliver E. Craig

Pottery was adopted by hunter-gatherers in the Eastern Baltic at the end of the 6th millennium cal BC. To examine the motivations for this cultural and technological shift, here we report the organic residue analysis of ceramic vessels from the earliest pottery horizon (Narva) in this region. A combined approach using GC-MS, GC-C-IRMS and bulk IRMS of residues absorbed into the ceramic and charred surface deposits was employed. The results show that despite variable preservation, Narva ceramic vessels were preferentially used for processing aquatic products. We argue that pottery was part of a new Late Mesolithic subsistence strategy which included more intensive exploitation of aquatic foods and may have had important implications, such as increased sedentism and population growth.