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1.

Purpose

In summer 2007, biweekly benthic fluxes of the biogenic elements carbon (C), nitrogen (N), silicon (Si), and phosphorus (P) were studied in the Se?ovlje saltern (salt-making facility) in the northern Adriatic Sea, Slovenia in order to determine the impact of stromatolite (??petola??) on the geochemical properties of saltern sediments.

Materials and methods

The brine and pore waters were analyzed for salinity, NH 4 + , NO 3 ? , PO 4 3? , SiO 4 4? , total dissolved nitrogen, total dissolved phosphorus, and fluorescent dissolved organic matter. The sediment was analyzed for organic carbon (OC), total nitrogen (TN), total and organic phosphorus (OP), and biogenic Si concentrations, as well as values of ?? 13COC and ?? 15NTN.

Results and discussion

Nutrient concentrations in brine water increased along the salinity gradient due to different processes, such as the evaporative concentrations of seawater, bacterial activity, more pronounced transformation and degradation of organic matter, and regeneration of nutrients. The petola from the Se?ovlje saltern, which is predominately composed of cyanobacterial and diatom communities, develops during the early evaporation stage and survives during high salinity and halite crystallization. Nitrogen fixation and P removal were the principal biogeochemical processes controlling dissolved inorganic N and P concentrations. At higher salinities, N limitation was more important. Microbes decomposed at higher salinities, and the remineralized N and P nutrients were released from surface pore waters to the brine. OP remineralization was also an important process influencing the distribution of PO 4 3? concentrations in pore waters deeper in the sediments. The increasing SiO 4 4? concentrations with increasing salinity in the brine waters were due to dissolution of diatom frustules, while the decrease in pore water SiO 4 4? was probably the consequence of microbial uptake.

Conclusions

This study provides a better understanding of nutrient cycling and the geochemical processes in the Se?ovlje saltern.  相似文献   

2.
The study aimed to determine the influence of catchment characteristics and flood type on the relationship between streamflow and a number of chemical characteristics of streamwater. These were specific electrical conductivity (SC), pH, the concentrations of main ions (Ca2+, Mg2+, Na+, K+, HCO 3 ? , SO 4 2? , and Cl?), and nutrients (NH 4 + , NO 2 ? , NO 3 ? , and PO 4 3? ). These relationships were studied in three small catchments with different geological structure and land use. Several flood types were distinguished based on the factors that initiate flooding and specific conditions during events. Geological factors led to a lower SC and main ion concentrations at a given specific runoff in catchments built of resistant sandstone versus those built of less resistant sediments. A lower concentration of nutrients was detected in the semi-natural woodland catchment versus agricultural and mixed-use catchments, which are strongly impacted by human activity. The strongest correlation between streamflow and the chemical characteristics of water was found in the woodland catchment. Different types of floods were characterized by different ion concentrations. In the woodland catchment, higher SC and higher concentrations of most main ions were noted during storm-induced floods than during floods induced by prolonged rainfall. The opposite was true for the agricultural and mixed-use catchments. During snowmelt floods, SC, NO 3 ? , and most main ion concentrations were higher when the soil was unfrozen in the agricultural and mixed-use catchments versus when the soil was frozen. In the case of the remaining nutrients, lower concentrations of NH 4 + were detected during rain-induced floods than during snowmelt floods. The opposite was true of PO 4 3? .  相似文献   

3.
Excess PO 4 3? from agricultural subsurface drainage and runoff degrades the overall water quality of the receiving surface waters in a cumulatively damaging process known as eutrophication. In the past 25 years, PO 4 3? removal by industrial byproducts and minerals has received considerable attention because these materials are both abundant and inexpensive. In this study, the saturated falling-head hydraulic conductivity and phosphate removal capability of granulated blast furnace slag (GBFS), cement kiln dust (CKD), zeolite, silica sand, and coconut shell activated carbon (CS-AC) were assessed. GBFS, zeolite, silica sand, CS-AC, and 5:95% and 10:90% CKD/sand blends all exhibited hydraulic conductivities ??0.001 cm/s. GBFS and the CKD/sand blends exhibited >98% PO 4 3? removal while CS-AC removed 70?C79% of initial PO 4 3? concentrations. In contrast, silica sand and zeolite removed 21?C58% of PO 4 3? . The phosphate removal data for each material was modeled against the Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, and Frumkin sorption isotherms to yield insight into possible removal mechanisms. Overall, GBFS, CKD, zeolite, silica sand, and CS-AC were sufficiently permeable and removed significant amounts of PO 4 3? and should be considered for use in treatment of agricultural effluent.  相似文献   

4.

Purpose

Nitrate (NO 3 ? ) is often considered to be removed mainly through microbial respiratory denitrification coupled with carbon oxidation. Alternatively, NO 3 ? may be reduced by chemolithoautotrophic bacteria using sulfide as an electron donor. The aim of this study was to quantify the NO 3 ? reduction process with sulfide oxidation under different NO 3 ? input concentrations in river sediment.

Materials and methods

Under NO 3 ? input concentrations of 0.2 to 30?mM, flow-through reactors filled with river sediment from the Pearl River, China, were used to measure the processes of potential NO 3 ? reduction and sulfate (SO 4 2? ) production. Molecular biology analyses were conducted to study the microbial mechanisms involved.

Results and discussion

Simultaneous NO3 ? removal and SO4 2? production were observed with the different NO 3 ? concentrations in the sediment samples collected at different depths. Potentially, NO 3 ? removal reached 72 to 91?% and SO 4 2? production rates ranged from 0.196 to 0.903?mM?h?1. The potential NO 3 ? removal rates were linearly correlated to the NO 3 ? input concentrations. While the SO 4 2? production process became stable, the NO 3 ? reduction process was still a first-order reaction within the range of NO 3 ? input concentrations. With low NO 3 ? input concentrations, the NO 3 ? removal was mainly through the pathway of dissimilatory NO 3 ? reduction to NH 4 + , while with higher NO 3 ? concentrations the NO 3 ? removal was through the denitrification pathway.

Conclusions

While most of NO 3 ? in the sediment was reduced by denitrifying heterotrophs, sulfide-driven NO 3 ? reduction accounted for up to 26?% of the total NO 3 ? removal under lower NO 3 ? concentrations. The vertical distributions of NO 3 ? reduction and SO 4 2? production processes were different because of the variable bacterial communities with depth.  相似文献   

5.
The influence of NTA, EDTA, STPP, Triton X100, PO inf4 sup3 and NO inf3 sup? on the mobilization of Pb, Cd, Cu, Cr and Mn from sediments of two rivers located in Northern Greece was studied. The release caused by all examined complexing agents was higher in deionized water than either Axios or Aliakmon river water due to the lack of competition of Ca and Mg cations with the heavy metals for the studied complexing agents, and the decrease of ionic strength. From all examined agents NTA and EDTA showed the greater mobilization ability. Copper showed the greater tendency for remobilization by all examined agents, (according to the order: EDTA?NTA, Triton X1004 PO inf4 sup3? > NO inf3 sup3? ?STPP) while Cr and Mn the smallest following the orders: NTA, PO inf4 sup3? >> NO inf3 sup? , Triton X1004 EDTA, STPP and STPP > EDTA > NTA > Triton X 100 ? PO inf4 sup3? NO3, respectively. An increase in mobilization was noticed with an increase of agent concentration and time of shaking.  相似文献   

6.
At Lange Bramke (Harz) soil solution and runoff concentrations of major elements were observed over 16 yr. During this period acid deposition was high but showed a marked decrease of H+ and SO 4 2? both in concentrations and fluxes over the last five years. Among others, this record reveals the following patterns: seasonality in the signals for SO 4 2? and NO 3 ? in runoff which are synchronous; an accumulation of SO 4 2? in the soil, initially up to 50% of the deposition fluxes; apparently no correlation between runoff and SO 4 2? concentration, and no long-term trend in runoff concentration of SO 4 2? . In this paper we use these patterns in the data set from Lange Bramke to test two established acidification models. The test criterion is that the algorithms employed by the SO 4 2? modules of these models must be able to reproduce these features. To that end, both models need not to be run as it can be shown that even with completely unrestricted parameter values the two algorithms are unable to match the observed SO 4 2? dynamics. The MAGIC model (Cosbyet al., 1985) is unable to reproduce, given the existence of net SO 4 2? accumulation, the constant SO 4 2? concentration in runoff during the last 16 years. The second model, BEM (Prenzel, 1986), is succesful in reconstructing the constant SC>4~ levels in runoff. However, on a monthly time scale BEM predicts a shift between the periodic maximum concentrations of SO 4 2? and NO 3 ? which is not observed in the data.  相似文献   

7.
Nitrification is a process in which ammonia is oxidized to nitrite (NO 2 ? ) that is further oxidized to nitrate (NO 3 ? ). The relations between these two steps and ambient ammonia concentrations were studied in surface water of Chinese shallow lakes with different trophic status. For the oxidations of both ammonia and NO 2 ? , more eutrophic lakes generally showed significantly higher potential and actual rates, which was linked with excessive ammonia concentrations. Additionally, both potential and actual rates for ammonia oxidation were higher than those for NO 2 ? oxidation in the more eutrophic lakes, while in the lakes with lower trophic status, both potential and actual rates for ammonia oxidation were almost equivalent to those for NO 2 ? oxidation. This can be explained by the excessive unionized ammonia (NH3) concentration that inhibits nitrite-oxidizing bacteria in the more eutrophic lakes. The laboratory experiment with different ammonia concentrations, using the surface water in a eutrophic lake, showed that ammonia oxidation rates were proportional to the ammonia concentrations, but NO 2 ? oxidation rates did not increase in parallel. Furthermore, NO 2 ? oxidation was less associated with particles in natural water of the studied lakes. Without effective protection, it would be selectively inhibited by the excessive ammonia in hypereutrophic lakes, resulting in NO 2 ? accumulation. Shortly, the increased concentrations of ammonia cause a misbalance between the NO 2 ? -producing and the NO 2 ? -consuming processes, thereby exacerbating the lake eutrophication.  相似文献   

8.
High As groundwater normally contained high concentrations of Cl? and HCO 3 ? . This study examined the effects of Cl?, HCO 3 ? , and As species on As uptake by hyperaccumulator Pteris vittata. Plants were exposed hydroponically to 5.0?mg/L As(III) or As(V) in the presence of 0, 0.5, 1, 2, 5, 10, and 20?mM of Cl? or HCO 3 ? for 10?days. Addition of high Cl? concentrations (>10?mM) slightly inhibited P. vittata growth (biomass), while generally had no significant effect on plant As uptake. High solution pH resulted in reduced plant growth and As uptake, which attributed to the inhibitory effects in HCO 3 ? treatments with the high pH of the high HCO 3 ? concentration. It was speculated that addition of HCO 3 ? (<20?mM) would have no significant effect on plant growth and As uptake. The inhibitory effect of HCO 3 ? on As translocation was less apparent in the As(III) solutions than the As(V) solutions. For the high As groundwater with As(III) as the predominant species, high pH, instead of high concentrations HCO 3 ? and Cl?, was expected to inhibit As uptake. The results suggested that optimum plant growth and maximum As hyperaccumulation could be achieved by adjusting solution pH in the growth media (around 7.2).  相似文献   

9.

Purpose

Nitrous oxide (N2O) production and reduction rates are dependent on the interactions with each other and it is therefore important to evaluate them within the context of simultaneously operating N2O emission and reduction. The objective of this study was to quantify the simultaneously occurring N2O emission and reduction across a range of subtropical soils in China, to gain a mechanistic understanding of potential N2O dynamics under the denitrification condition and their important drivers, and to evaluate the potential role of the subtropical soils as either sources or sinks of N2O through denitrification.

Materials and methods

Soils (45, from a range of different land uses and soil parent materials) were collected from the subtropical region of Jiangxi Province, China, and tested for their potential capacity for N2O emission and N2O reduction to N2 during denitrification. N2O emission and reduction were determined in a closed system under N2 headspace after the soils were treated with 200?mg?kg?1 NO 3 ? -N and incubation at 30?°C for 28?days. The soil physical and chemical properties, the temporal variations in headspace N2O concentration, and NO 3 ? -N and NH 4 + -N concentrations in the soil slurry were measured.

Results and discussion

Variations in N2O concentration (N) over incubation time (t) were consistent with an equation in which average R 2?=?0.84?±?0.11 (p?<?0.05): $ N = A \times \left( {1 - \exp \left( { - {k_1} \times t} \right)} \right) - B \times \exp \left( {{k_2} \times t} \right) $ , where A is the total N2O emission during the incubation, B is a constant, and k 1 and k 2 are the N2O emission constant and reduction constants, respectively. The results of the simulation showed that k 1 was greater than k 2. The reduced amount of NO 3 ? -N in the first 7?days of incubation and the N2O emission rate (the percentage of A value relative to the amount of NO 3 ? -N reduced during the 28-day incubation, R n) were able to explain 82.9?% (p?<?0.01) of the variation in total N2O emission (A) during the incubation for the soil samples studied, indicating that the total amount of N2O emitted was determined predominately by denitrification capacity. Soil organic carbon content and soil nitrogen mineralization are the key factors that determine differences in the amounts of reduced NO 3 ? -N among the soil samples. The R n value decreased with increasing k 2 (p?<?0.01), indicating that soils with higher N2O reduction capacity under these incubation conditions would emit less N2O per unit of denitrified NO 3 ? -N than the other soils. Results are valuable in the evaluation of net N2O emissions in the subtropical soils and the global N budget.

Conclusions

In a closed, anaerobic system, variations in N2O concentration in the headspace over the incubation time were found to be compatible with a nonlinear equation. Soil organic carbon and the amount of NH 4 + -N mineralized from the organic N during the first 7?days of incubation are the key factors that determine differences in the N2O emission constant (k 1), the N2O reduction constant (k 2), the total N2O emission during the incubation (A) and the N2O emission rate (R n).  相似文献   

10.
Stable isotopes of S are used in conjunction with dissolved SO 4 2? concentrations to evaluate the utility ofδ 34S ratios in tracing contributions of bedrock-derived S to SO 4 2? in runoff. Water samples were collected over the annual hydrograph from two tributaries in the West Glacier Lake, Wyoming, catchment. Concentrations of SO 4 2? ranged from 12.6 to 43.0 Μeq L?1;δ 34S ratios ranged from ?1.8‰ to +4.9‰ Theδ 34S value of atmospherically derived SO 4 2? is about +5.6%c.; four samples of pyrite from the bedrock hadδ 34S ratios that ranged from +0.7 to +4.1‰ Concentrations of SO 4 2? were inversely related toδ 34S and discharge. The data for the tributary with the higher SO 4 2? concentrations were reasonably consistent with mixing between atmospheric S and S from a bedrock source with aδ 34S ratio of about ?4.5‰. The difference from the measured bedrock values presumably indicates that S isotopes in the bedrock pyrite are heterogeneously distributed. The data from the tributary with lower SO 4 2? concentrations did not follow a two-component mixing line. Deviation from a two-component mixing line is most likely caused by preferential elution of SO 4 2? from the snowpack during the early stages of snowmelt, although microbially mediated fractionation of S isotopes in the soil zone also may cause the deviation from the mixing line. Sulfur isotopes are useful in identifying whether or not there is a substantial contribution of bedrock S to runoff, but quantifying that contribution is problematic.  相似文献   

11.
A modeling study on fertilizer by-products fate and transport was performed in an unconfined shallow aquifer equipped with a grid of 13 piezometers. The field site was located in a former agricultural field overlying a river paleochannel near Ferrara (Northern Italy), cultivated with cereals rotation until 2004 and then converted to park. Piezometers were installed in June 2007 and were monitored until June 2009 via pressure transducer data loggers to evaluate the temporal and spatial variation of groundwater heads, while an onsite meteorological station provided data for recharge rate calculations via unsaturated zone modeling. The groundwater composition in June 2007 exhibited elevated nitrate (NO 3 ? ) and chloride (Cl?) concentrations due to fertilizer leaching from the top soil. The spatial distribution of NO 3 ? and Cl? was heterogeneous and the concentration decreased during the monitoring period, with NO 3 ? attenuation (below 10?mg/l) after 650?days. A transient groundwater flow and contaminant transport model was calibrated versus observed heads and NO 3 ? and Cl? concentrations. Cl? was used as environmental tracer to quantify groundwater flow velocity and it was simulated as a conservative species. NO 3 ? was treated as a reactive species and denitrification was simulated with a first order degradation rate constant. Model calibration gave a low denitrification rate (2.5e?3 mg-NO 3 ? /l/d) likely because of prevailing oxic conditions and low concentration of dissolved organic carbon. Scenario modeling was implemented with steady state and variable flow time discretization to identify the mechanism of NO 3 ? attenuation. It was shown that transient piezometric conditions did not exert a strong control on NO 3 ? clean up time, while transient recharge rate did, because it is the main source of unpolluted water in the domain.  相似文献   

12.
A long-term hydrological and water chemistry research was conducted in three experimental microbasins differing in land cover: (1) a purely agricultural fertilized microbasin, (2) a forested microbasin dominated by Carpinus betulus (European hornbeam), and (3) a forested microbasin dominated by Picea abies (L.) (Norway spruce). The dissolved inorganic nitrogen (DIN: NH 4 + , NO 2 ? , NO 3 ? ) budget was examined for a period of 3 years (1991–1993). Mean annual loads of DIN along with sulfate SO 4 2? and base cations Ca2+, Mg2+, Na+, K+, and HCO 3 ? were calculated from ion concentrations measured in stream water, open-area rainfall, throughfall (under tree canopy), and streamwater at the outlets from the microbasins. Comparison of the net imported/exported loads showed that the amount of NO 3 ? leached from the agricultural microbasin is ～3.7 times higher (43.57 kg ha?1?a?1) than that from the spruce dominated microbasin (11.86 kg ha?1?a?1), which is a markedly higher export of NO 3 ? compared to the hornbeam dominated site. Our analyses showed that land cover (tree species) and land use practices (fertilization in agriculture) may actively affect the retention and export of nutrients from the microbasins, and have a pronounce impact on the quality of streamwater. Sulfate export exceeded atmospheric rainfall inputs (measured as wet deposition) in all three microbasins, suggesting an additional dry depositions of SO 4 2? and geologic weathering.  相似文献   

13.
The effect of the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) on N transformations and composition of ammonia-oxidizing bacteria (AOB) communities was investigated at the centimeter scale in a microcosm experiment under laboratory conditions. After 28 days, samples were collected from soil treated with urea or urea and DMPP at increasing distance from the fertilizer zone; this distance ranged from 0 to 5 cm in both horizontal and vertical directions. The results showed that DMPP application significantly increased soil pH and NH 4 + -N and mineral N (NH 4 + -N, NO 3 ? -N, and NO 2 ? -N) concentrations but decreased (NO 3 ? + NO 2 ? )-N concentration, and such effect was decreased by increasing the distance from the fertilizer zone. Fingerprint profiles of denaturing gradient gel electrophoresis showed that the number of bands decreased by increasing the distance from the fertilizer zone due to decreasing NH 4 + -N concentrations in the urea treatment. Compared to urea applied alone, DMPP application increased NH 4 + -N concentrations and decreased AOB diversity from 0 to 3 cm but promoted diversity from 3 to 5 cm distance from the fertilizer zone. A phylogenetic analysis showed that AOB communities were dominated by Nitrosospira cluster 3. Therefore, the nitrification inhibitor DMPP modified the composition of AOB communities by increasing the distance from the fertilizer zone and this probably was related to the changes in soil pH and inorganic N concentration.  相似文献   

14.

Purpose

Hoop pine (Araucaria cunninghamii) is a nitrogen (N)-demanding native Australian softwood plantation species. Litter quality and its effects on soil mineral N and 15N transformations have not been well studied in the hoop pine plantation and adjacent native forest. The present study was conducted to determine the impact of 15N injection depth and litter additions on the dynamics and fate of mineral 15N and also to compare the difference in litter quality, 15N dynamics, and fate between the hoop pine plantation (HP) and the adjacent native forest (NF).

Materials and methods

The experiments were done in the Yarraman State Forest (26°52′ S, 151°51′ E), southeastern Queensland. Materials of litter addition were prepared on the basis of ten random samples of litters taken from the NF and HP sites using a 1?×?1-m quadrat. Litter additions were defined as: SL represented the average condition of forest floor in the forest ecosystems and DL represented the double average amount of litters in the forest ecosystem. Experiment 1 covered 2 forest types (NF and HP)?×?3 litter rates (nil litter, SL, and DL)?×?3 15N injection depths (0, 2.5, and 5.0 cm). Experiment 2 included 2 forest types (NF and HP)?×?2 litter rates (nil litter and SL)?×?3 injection depths (0, 2.5, and 5.0 cm) of distilled water. The in situ core incubation method was used with an incubation period of 28 days. The isotope ratio of mineral N or/and total N (soil and litter) were analyzed using an isotope ratio mass spectrometer with a Eurovector elemental analyzer (Isoprime-EuroEA 3000).

Results

Total N and δ 15N were significantly higher, and C/N ratios and δ 13C were significantly lower in the NF litters than in the HP litters. The NF litters had significantly lower total 15N and total 15N recovery than the HP litters after 15N addition. Litter addition had no significant effect on mineral 15N transformations and δ 15N in the NF soil, but decreased 15NO 3 ? –N, mineral 15N, and δ 15N and increased immobilized 15N in the HP soil. The depth of added 15NH 4 + significantly altered total 15N, δ 15N, and total 15N recovery in the litters, whereas it did not influence 15NH 4 + –N, 15NO 3 ? –N, mineral 15N, or immobilized 15N in soils in the two forest ecosystems.

Discussion

The NF litters had significantly higher δ 15N than the HP litters, indicating that the NF soil had a higher rate of nitrification than the HP soil. Higher litter quality in the NF was an important driving force for N cycling to promote strong N dynamics in the NF soil over the HP soil. The HP litters had significantly higher total 15N than the NF litters after 15N addition, implying that soil mineral N was relatively deficient in the HP in comparison with the NF. Litters decreased nitrification and increased immobilization in the HP soil, showing forest litters resulted in more N immobilization to prevent the loss of substantial quantities of NO 3 ? through leaching or denitrification. The depth of 15N injection did not significantly alter concentrations of 15NH 4 + –N, 15NO 3 ? –N, mineral 15N, and immobilized 15N in the NF and HP soils, suggesting that the depth of 15N injection had no significant influence on the evaluation of soil N transformations.

Conclusions

The NF litters had significantly higher total N and δ 15N and lower C/N ratios and δ 13C than the HP litters. Mineral N was relatively insufficient in the HP soil relative to the NF soil. The HP litters facilitated more N immobilization in the soil to reduce the loss of substantial quantities of NO 3 ? through leaching or denitrification. The depth of 15N added did not significantly alter concentrations of 15NH 4 + –N, 15NO 3 ? –N, mineral 15N, and immobilized 15N in the NF and HP soils. The application of 15N solution by uniform sprinkling onto the soil surface can be used to study in situ field N (including mineral 15N) transformations in the 10-cm depth soils of both forest ecosystems.  相似文献   

15.
Following the Deepwater Horizon explosion and crude oil contamination of a marsh ecosystem in AL in June 2010, hydrocarbon-degrader microbial abundances of aerobic alkane, total hydrocarbon, and polycyclic aromatic hydrocarbon (PAH) degraders were enumerated seasonally. Surface sediment samples were collected in October and December of 2010 and in April and July of 2011 along 40?C70-m transects from the high tide to the intertidal zone including Spartina alterniflora-vegetated marsh, seagrass (Ruppia maritima)-dominated sediments, and nonvegetated sediments. Alkane and total hydrocarbon degraders in the sediment were detected, while PAH degraders were below detection limit at all locations examined during the sampling periods. The highest counts for microbial alkane degraders were observed at the high tide line in April and averaged to 8.65?×?105 of cells/g dry weight (dw) sediment. The abundance of alkane degraders during other months ranged from 9.49?×?103 to 3.87?×?104, while for total hydrocarbon degraders, it ranged between 5.62?×?103 and 1.14?×?105 of cells/g dw sediment. Pore water nutrient concentrations (NH 4 + , NO 3 ? , NO 2 ? , and PO 4 3? ) showed seasonal changes with minimum values observed in December and April and maximum values in October and July. Concentrations of total petroleum hydrocarbons in sediments averaged 100.4?±?52.4 and 141.9?±?57.5?mg/kg in January and July, 2011, respectively. The presence of aerobic microbial communities during all seasons in these nearshore ecosystems suggests that an active and resident microbial community is capable of mineralizing a fraction of petroleum hydrocarbons.  相似文献   

16.
A 2 yr field study on the influence of N fertilization and rainfall on groundwater pollution was carried out in the sandy area of Belgium. The NO inf3 sup? -N and Cl? content of the groundwater at 0.5, 1.0, 1.5, and 2.0 m depths was monitored every two weeks on a field, grown with barley in 1980 and with maize in 1981. Turnips for cattle feed were grown in between the two crops. The total annual rainfall during the period under study was about 800 mm. The NO inf3 sup? -N content at all depths was at all times above 11.3 mg NO inf3 sup? -N dm?3, the WHO safe limit. Fluctuation of the NO inf3 sup? -N content occurred mainly at 0.5 and 1.0 m. The concentration at 1.5 and 2.0 m depths was higher most of the time than at 0.5 and 1.0 m. Leaching of NO inf3 sup? -N into deeper layers occurred when there was heavy rainfall. There was no important loss of NO inf3 sup? -N through denitrification at 1.5 and 2.0 m depths.  相似文献   

17.
This study assessed the foliar uptake of 15N-labelled nitrogen (N) originating from wet deposition along with leaf surface conditions, measured by wettability and water storage capacity. Foliar 15N uptake was measured on saplings of silver birch, European beech, pedunculate oak and Scots pine and the effect of nitrogen form (NH 4 + or NO 3 ? ), NH 4 + to NO 3 ? ratio and leaf phenology on this N uptake was assessed. Next to this, leaf wettability and water storage capacity were determined for each tree species and phenological stage, and the relationship with 15NH 4 + and 15NO 3 ? uptake was examined. Uptake rates were on average five times higher (p?<?0.05) for NH 4 + than for NO 3 ? and four times higher for deciduous species than for Scots pine. Developing leaves showed lower uptake than fully developed and senescent leaves, but this effect was tree species dependent. The applied NH 4 + to NO 3 ? ratio did only affect the amount of N uptake by senescent leaves. The negative correlation between measured leaf contact angles and foliar N uptake demonstrates that the observed effects of tree species and phenological stage are related to differences in leaf wettability and not to water storage capacity.  相似文献   

18.
Over 3 yr of particulate measurements were made at two high elevation sites in the southern Appalachian Mountains of Tennessee and Virginia. Both dichotomous samplers and filter packs were used to obtain day and night, week-long samples for subsequent elemental and ionic analysis. Total No inf3 sup? (HNO3 + No in3 sup? ) and SO inf4 sup2? averaged, respectively, 1.1 and 5.0 µg m?3 at Look Rock, Tennessee and 2.0 and 6.4 µg m?3 at Whitetop Mountain, Virginia. At Whitetop Mountain, the spring and summer seasons had the highest average SO inf4 sup2? concentrations. Seasonally, total N03 varied little. The diurnal variation of elements and SO inf4 sup2? was small. Only total NO inf3 sup? varied substantially with highest values during the day. The fine fraction (particle diameter < 2.5 µm) accounted for about 67% of the total mass. Fine mass and elemental concentrations were generally higher at Look Rock. The elements comprising the principal mass fraction of the coarse samples (2.5 gm < particle diameter < 10 to 15 µm) were of crustal origin (e.g., Al, Si, Ca, Fe) while the element comprising the principal mass fraction of the fine samples (i.e., S) was of manmade origin. Cluster analysis identified two groups of elements at Whitetop Mountain. These groups, in both the coarse and fine fraction, were associate with a soil and an automobile emission component. At Look Rock, only a soil component was obvious.  相似文献   

19.
The objectives of this study are to assessδ 34S as a tracer of anthropogenic SO 4 2? in groundwater and to document geochemical interactions that take place as a result of industrial SO 4 2? loading. During four separate sampling excursions, groundwater samples were obtained from 13 piezometers which surround the elemental S storage blocks at a processing facility for sour (H2S) natural gas in Alberta, Canada. Each sample was analyzed forδ 34Ssulfate,δ 18Osulfate,δ 18Owater,δDwater, major aqueous species, alkalinity, pH, temperature and dissolved O2. Hydraulic head measurements were taken to define the groundwater flow field. In the study area, anthropogenic SO 4 2? has aδ 34S of approximately +18‰ (CDT), while natural groundwater SO 4 2? is depleted to about ?12%. Low activity of sulfate reducing bacteria in the groundwater at this site assures thatδ 34S is a conservative tracer. Groundwater SO 4 2? concentrations increase asδ 34S approaches +18‰, suggesting that elevated SO 4 2? concentrations are due to S released by sour gas processing. Acidic waters generated by the oxidation of industrial S from the gas plant are neutralized by rock-water reactions.  相似文献   

20.
A constructed wetland composed of a pond- and a marsh-type wetland was employed to remove nitrogen (N) and phosphorus (P) from effluent of a secondary wastewater treatment plant in Korea. Nutrient concentrations in inflow water and outflow water were monitored around 50 times over a 1-year period. To simulate N and P dynamics in a pond- and a marsh-type wetland, mesocosm experiments were conducted. In the field monitoring, ammonium (NH 4 + ) decreased from 4.6 to 1.7 mg L?1, nitrate (NO 3 ? ) decreased from 6.8 to 5.3 mg L?1, total N (TN) decreased from 14.6 to 10.1 mg L?1, and total P (TP) decreased from 1.6 to 1.1 mg L?1. Average removal efficiencies (loading basis) for NO 3 ? , NH 4 + , TN, and TP were over 70%. Of the environmental variables we considered, water temperature exhibited significant positive correlations with removal rates for the nutrients except for NH 4 + . Results from mesocosm experiments indicated that NH 4 + was removed similarly in both pond- and marsh-type mesocosms within 1 day, but that NO 3 ? was removed more efficiently in marsh-type mesocosms, which required a longer retention time (2?C4 days). Phosphorus was significantly removed similarly in both pond- and marsh-type mesocosms within 1 day. Based on the results, we infer that wetland system composed of a pond- and a marsh-type wetland consecutively can enhance nutrient removal efficiency compared with mono-type wetland. The reason is that removal of NH 4 + and P can be maximized in the pond while NO 3 ? requiring longer retention time can be removed through both pond and marsh. Overall results of this study suggest that a constructed wetland composed of a pond- and a marsh-type wetland is highly effective for the removal of N and P from effluents of a secondary wastewater treatment plant.  相似文献   

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