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1.
The size-fractionated phytoplankton biomass and primary production were investigated in four contrasting areas of Hong Kong waters in 2006. Phytoplankton biomass and production varied seasonally in response to the influence of the Pearl River discharge. In the dry season, the phytoplankton biomass and production were low (<42 mg chl m−2 and <1.8 g C m−2 day−1) in all four areas, due to low temperatures and dilution and reduced light availability due to strong vertical mixing. In contrast, in the wet season, in the river-impacted western areas, the phytoplankton biomass and production increased greater than five-fold compared to the dry season, especially in summer. In summer, algal biomass was 15-fold higher than in winter, and the mean integrated primary productivity (IPP) was 9 g C m−2 day−1 in southern waters due to strong stratification, high temperatures, light availability, and nutrient input from the Pearl River estuary. However, in the highly flushed western waters, chl a and IPP were lower (<30 mg m−2 and 4 g C m−2 day−1, respectively) due to dilution. The maximal algal biomass and primary production occurred in southern waters with strong stratification and less flushing. Spring blooms (>10 μg chl a L−1) rarely occurred despite the high chl-specific photosynthetic rate (mostly >10 μg C μg chl a −1 day−1) as the accumulation of algal biomass was restricted by active physical processes (e.g., strong vertical mixing and freshwater dilution). Phytoplankton biomass and production were mostly dominated by the >5-μm size fraction all year except in eastern waters during spring and mostly composed of fast-growing chain-forming diatoms. In the stratified southern waters in summer, the largest algal blooms occurred in part due to high nutrient inputs from the Pearl River estuary.  相似文献   

2.
Symptoms of dental fluorosis have been observed in rural communities located in the Sierras Pampeanas de Córdoba, a mountainous area in Central Argentina. The clinical assessment was performed in the Charbonier Department, where the fluoride (F−) intake was determined to be 3.90 ± 0.20 mg day−1 (n = 16). In this community, mild and severe fluorosis reach an incidence of 86.7% (total teeth surface = 636 teeth) among the children population. To determine the origin and distribution of fluorine in natural waters from the Charbonier Department and nearby regions, sampling was performed in the area covering the San Marcos River basin. The obtained results show that F− concentrations vary between ~1 to ~2.5 mg l−1, with an outlier value of 8 mg l−1. The spatial distribution of F− shows that the lowest concentrations are found at the basin’s catchments. Maximum values are located in two sectors of the basin: the Charbonier depression in the eastern part and at the San Marcos village, downstream the main collector, in the western part of the basin. In these two regions, the F− contents in ground- and surface waters are >2.0 mg l−1 and nearly constant. Dissolved F− in natural waters from the study area has its origin in the weathering of F-bearing minerals present in the region’s dominant lithology. The extent of mineral weathering is mostly determined by the residence time of water within the aquatic reservoir. Longer residence times and a major solid–water interaction lead to enhanced release of F−. This explains the higher F− concentrations found in basin areas with lower run off. The removal of F− from water appears to occur by neither fluorite precipitation, nor by adsorption. Hence, variations in F− concentrations seem to be more related to regional hydrological conditions.  相似文献   

3.
Peatlands are a large potential source of methane (CH4) to the atmosphere. In order to investigate the effects of climate change on CH4 emission from northern ombrotrophic peatlands, a simulation model coupling water table dynamics with methane emission was developed for the Mer Bleue Bog in Ontario, Canada. The model was validated against reported values of CH4 flux from field measurements and the model outputs exhibited high sensitivity to acrotelm thickness, leaf area index, transmissivity and slope of water table. With a 2–4°C temperature rise over the 4-year simulation period, the rate of CH4 release dropped significantly to under 0.1 mg m−2 day−1. On the other hand, mean CH4 emission increased by >26-fold when the increase in precipitation was >15%. When looking at the combined effects, the highest CH4 release (13.3 mg m−2 day−1) was attained under the scenario of 2°C temperature rise and 25% precipitation increase. Results obtained in this study highlight the importance of avoiding more extreme climate change, which would otherwise lead to enhanced methane release from peatlands and further atmospheric warming through positive feedback.  相似文献   

4.
The effect of the source water quality on As(V) removal by coagulation/microfiltration (C/MF) was investigated systematically using a jar test and a lab-scale test; the results of the lab-scale test coincide with those of the jar test. It showed that the increase of dissolved organic carbon (DOC), HPO4 2− and HCO3 − concentrations would moderately decrease As(V) removal, and the residual As(V) concentration in treated water is no more than 10 μg L−1 when the concentration of DOC, HPO4 2− and HCO3 − in raw water is not beyond 9.22 mg L−1, 1.6 mg L−1 and 300 mg L−1, respectively. Other co-ions, such as Cl−, NO3 −, F−, SO4 2−, and counter-ions including K+, Ca2+ and Mg2+, have little effect on As(V) removal. Both results of the jar test and the lab-scale test demonstrate that Fe3+ dose of 6 mg L−1 is enough to eliminate the influence of HCO3 − whose concentration changes from 350 mg L−1 to 450 mg L−1. In the lab-scale test, As(V) removal ranged from 92.8 to 98.2% at Fe3+ dose of 4 mg L−1 and 5 mg L−1 when As(V) concentration in raw water was about 100 μg L−1. The results obtained in this study suggest that As(V) removal by C/MF process is sensitive to the quality of raw water, and a jar test needs to be done before C/MF process is used for arsenic removal from drinking water.  相似文献   

5.
The Sarcheshmeh copper mine smelter plant is one of the biggest copper producers in Iran. Long-time operation of about 25 years of the smelter plant causes release of potentially toxic heavy metals into the environment. In this paper, geochemical distribution of toxic heavy metals in 28 soil samples was evaluated around the Sarcheshmeh smelter plant. Soils developed over the nonmineralized and uncontaminated areas have an average background concentration of 41.25 mg kg−1 Cu, 26.6 mg kg−1 As, 12.7 mg kg−1 Pb, 0.9 mg kg−1 Sb, 1.9 mg kg−1 Mo, 1.7 mg kg−1 Sn, 0.2 mg kg−1 Cd, 0.15 mg kg−1 Bi, 235 mg kg−1 S and 73.4 mg kg−1 Zn, respectively. As a result of smelting process, the upper soil layers (0–5 cm) were polluted by Cu (>1,397 mg kg−1), Cd (>3.42 mg kg−1), S (>821 mg kg−1), Mo (>10.3 mg kg−1), Sb (>11.7 mg kg−1), As (>120.6 mg kg−1), Pb (>83.8 mg kg−1), Zn (>214.9 mg kg−1), and Sn (>3.7 mg kg−1), respectively. These values are much higher than the normal concentration of the elements in the uncontaminated soil layers. The elemental values decrease with distance travelled away of the smelter plant, especially at minimum wind direction. Furthermore, high contaminated values of Cu (8,430 mg kg−1), As (500 mg kg−1), Pb (331 mg kg−1), Mo (61 mg kg−1), Sb (56.2 mg kg−1), Zn (664 mg kg−1), Cd (17.2 mg kg−1), Bi (13.4 mg kg−1), and S (3,780 mg kg−1) were observed in the upper soil layers close to the smelting waste dumps. Sequential extraction analysis shows that about 270 mg kg−1 Cu, 28 mg kg−1 Pb, 50.33 mg kg−1 Zn, and 47.84 mg kg−1 As were adsorbed by Fe and Mn oxides. The carbonate phases include 151 mg kg−1 Cu, 28 mg kg−1 Pb, 25 mg kg−1 Zn, and 32.99 mg kg−1 As. Organic matter adsorbed 314.6 mg kg−1 Cu and 29.18 mg kg−1 Zn.  相似文献   

6.
In 2005 and 2006, hydrogeochemical study was carried out in the bipartite Wiśniówka Mała pit lake of the Holy Cross Mountains (south-central Poland). This is the largest acidic water body in Poland. This report presents the element concentrations in the water and sediment, stable sulfur and oxygen isotope ratios in the soluble sulfates, and stable oxygen isotope ratio in the water. The scope of the investigation also encompassed mineralogical examinations (scanning electron microscope, X-ray diffraction) of the sediment. The results of this study show that there is a spatial and temporal variability in concentrations of most elements and sulfur isotope ratios in the examined pit lake. The water of the western pond displayed a lower pH with a mean of 3.73 and higher conductivity (390 μS cm−1) as well as higher concentrations of sulfates (156 mg L−1) and most of the cations and anions. The concentrations of Fe2+ and Fe3+ averaged 0.8 and 0.4 mg·L−1. In contrast, the eastern pond water revealed a higher pH (mean of 4.36), lower conductivity (293 μS cm−1) and lower sulfate (90 mg L−1) and trace metal levels. Similar variations were recorded in the stable sulfur isotope ratios. The δ34SV-CDT(SO4 2−) values in the water of the western pit pond were in the range of −6.7 to −4.6‰ (mean of −5.6‰), whereas that in the eastern pit pond ranged from −2.2 to −0.9‰ (−1.6‰). The alkalinity of the entire lake water was below 0.1 mg·L−1 CaCO3. No distinct difference in the δ18OV-SMOW(SO4 2−) was noted between the western and eastern pit ponds. Compared to the Purple Pond in the Sudetes (Poland) and similar sites throughout the world, the examined pit lake is highlighted by distinctly low concentrations of sulfates, iron and other trace metals. Based on this and other studies performed in the Holy Cross Mountains, a conclusion can be drawn that the SO4 2− in the Wiśniówka Mała pit lake water is a mixture of SO4 2− derived from the following sources: (1) pyrite oxidation (especially in the western pond water), (2) leaching of soluble sulfates from soils and waste material, as well as (3) subordinate deposition of airborne sulfate precipitation.  相似文献   

7.
Natural oyster shells (NOS) and calcined oyster shells (COS) were used to immobilize arsenic (As) from contaminated mine tailings. In addition, a blend of Portland cement (PC)/cement kiln dust (CKD) was used as a stabilizing agent. The Korean Standard Test (KST) method (1 N HCl extraction) was used to evaluate the effectiveness of the treatment. The experimental results showed that COS effectively immobilized As in treated mine tailings. Specifically, an As concentration less than 1 mg L−1 was obtained following COS treatment at 25 and 30 wt%. However, all the samples subjected to NOS treatments failed the Korean warning standard of 1.2 mg L−1 after 28 days of curing. All of the COS-PC treatments were successful meeting the Korean warning standard after 7 days of curing. However, the PC-only treatment failed to meet the Korean warning standard. Similarly, the CKD-only treatment was failed to meet the Korean warning standard after 7 days of curing. However, the COS-CKD treatment showed that when the COS content was greater than 20 wt%, less than 1 mg L−1 of As leachability was obtained. Scanning electron microscopy–energy dispersive X-ray spectroscopy (SEM–EDX) showed needle-like and torpedo-like Ca–As phases in the COS-treated samples suggesting that As was strongly associated with Ca and O. X-ray absorption near edge structure (XANES) analyses confirmed that As(V) was prevalent in the tailings and that there were no changes in As speciation following NOS or COS treatment.  相似文献   

8.
We measured seasonal variations in microzooplankton grazing in Long Island Sound (LIS) and San Francisco Bay (SFB). There was consistent evidence of nutrient limitation in LIS, but not SFB. We found higher chlorophyll a concentrations in LIS compared with SFB. In spite of differences in phytoplankton, there were no differences in microzooplankton abundance (summer: LIS, 12.4 ± 1.8 × 103 indiv. L−1; SFB, 14.1 ± 3.0 × 103 indiv. L−1), biomass (summer: LIS, 30.4 ± 5.0 μg C L−1; SFB, 26.3 ± 5.9 μg C L−1), or grazing rates (summer: LIS, 0.66 ± 0.19 day−1; SFB, 0.65 ± 0.18 day−1) between the two estuaries. In common with many other investigators, we found many instances of saturated as well as insignificant grazing. We suggest that saturation in some cases may result from high particle loads in turbid estuarine systems and that insignificant grazing may result from extreme saturation of the grazing response due to the need to process non-food particles.  相似文献   

9.
Simulated acidic precipitation (1:1 equivalent basis H2SO4:HNO3) at pH values of 2.5, 3.0, 3.5, 4.0, 4.5, 5.0 and 7.0 were conducted using column leaching to determine impacts of simulated acid rain on phosphorus (P) leaching from a calcareous sandy loam soil over a 40-day period. Soil columns were irrigated every day to make a total of 1,061 mm, equivalent to 3.5 years of rainfall (based on average annual rainfall). Leachates were collected and analyzed for anions and cations. There was significant nonlinear correlation between the amount of P leached and the simulated acid rain (R 2 = 0.61). Losses of P from the pH 2.5 and 7.0 treatments were 1.23, and 1.32 mg kg−1, respectively. The results showed that the amount of P leached from pH 4 (1.46 mg kg−1) and 5 treatments (1.52 mg−1 kg−1) were significantly larger than other treatments. Linear equation adequately described leaching of P in different treatments. The slope (mg kg−1 day−1) in the linear equation was defined as the leaching rate and for the pH 2.5 was 0.0354, and 0.0382 and 0.0406 for pH 4.5 and 7.0, respectively. The geochemical code Visual MINTEQ was used to calculate saturation indices. Leaching of P in different treatments was controlled by rate-limited dissolution of hydroxyapatite, β-tricalcium phosphate and to some extent octacalcium phosphate. The results indicate that acid rain in calcareous sandy loam soils may pose a risk in terms of groundwater contamination with P.  相似文献   

10.
Benthic respiration, sediment–water nutrient fluxes, denitrification and dissimilatory nitrate reduction to ammonium (DNRA) were measured in the upper section of the Parker River Estuary from 1993 to 2006. This site experiences large changes in salinity over both short and long time scales. Sediment respiration ranged from 6 to 52 mmol m−2 day−1 and was largely controlled by temperature. Nutrient fluxes were dominated by ammonium fluxes, which ranged from a small uptake of −0.3 to an efflux of over 8.2 mmol N m−2 day−1. Ammonium fluxes were most highly correlated with salinity and laboratory experiments demonstrated that ammonium fluxes increased when salinity increased. The seasonal pattern of DNRA closely followed salinity. DNRA rates were extremely low in March, less than 0.1 mmol m−2 day−1, but increased to 2.0 mmol m−2 day−1 in August. In contrast, denitrification rates were inversely related to salinity, ranging from 1 mmol m−2 day−1 during the spring and fall to less than 0.2 mmol m−2 day−1 in late summer. Salinity appears to exert a major control on the nitrogen cycle at this site, and partially decouples sediment ammonium fluxes from organic matter decomposition.  相似文献   

11.
The Cu–Co–Ni Texeo mine has been the most important source of Cu in NW Spain since Roman times and now, approximately 40,000 m3 of wastes from mine and metallurgical operations, containing average concentrations of 9,263 mg kg−1 Cu, 1,100 mg kg−1 As, 549 mg kg−1 Co, and 840 mg kg−1 Ni, remain on-site. Since the cessation of the activity, the abandoned works, facilities and waste piles have been posing a threat to the environment, derived from the release of toxic elements. In order to assess the potential environmental pollution caused by the mining operations, a sequential sampling strategy was undertaken in wastes, soil, surface and groundwater, and sediments. First, screening field tools were used to identify hotspots, before defining formal sampling strategies; so, in the areas where anomalies were detected in a first sampling stage, a second detailed sampling campaign was undertaken. Metal concentrations in the soils are highly above the local background, reaching up to 9,921 mg kg−1 Cu, 1,373 mg kg−1 As, 685 mg kg−1 Co, and 1,040 mg kg−1 Ni, among others. Copper concentrations downstream of the mine works reach values up to 1,869 μg l−1 and 240 mg kg−1 in surface water and stream sediments, respectively. Computer-based risk assessment for the site gives a carcinogenic risk associated with the presence of As in surface waters and soils, and a health risk for long exposures; so, trigger levels of these elements are high enough to warrant further investigation.  相似文献   

12.
We developed light requirements for eelgrass in the Pacific Northwest, USA, to evaluate the effects of short- and long-term reductions in irradiance reaching eelgrass, especially related to turbidity and overwater structures. Photosynthesis-irradiance experiments and depth distribution field studies indicated that eelgrass productivity was maximum at a photosynthetic photon flux density (PPFD) of about 350–550 μmol quanta m−2 s−1. Winter plants had approximately threefold greater net apparent primary productivity rate at the same irradiance as summer plants. Growth studies using artificial shading as well as field monitoring of light and eelgrass growth indicated that long-term survival required at least 3 mol quanta m−2 day−1 on average during spring and summer (i.e., May-September), and that growth was saturated above about 7 mol quanta m−2 day−1. We conclude that non-light-limited growth of eelgrass in the Pacific Northwest requires an average of at least 7 mol quanta m−2 day−1 during spring and summer and that long-term survival requires a minimum average of 3 mol quanta m−2 day−1.  相似文献   

13.
Drilling fluids are used for drilling natural gas, oil and water wells. These spill over into the surrounding soil at the point of drilling, which may impair soil health. A laboratory investigation was carried out to determine the effect of non aqueous drilling fluid (NADF) and synthetic base oil used with it on soil health as indicated by the dehydrogenase activity. A non-sterile sandy loam soil was treated with different amounts of NADF and base oil at a rate of 800, 8,000 and 16,000 mg kg−1. Initially, reduction in dehydrogenase activity was observed, but it increased with the incubation time. On the 60th day of incubation dehydrogenase activity in untreated control was 1.04 mg TPF g−1 h−1 whereas in the soil samples treated with NADF and the base oil (16,000 mg kg−1), the activity was 1.53 mg TPF h−1 and 1.90 mg TPF h−1, respectively, which was 72 and 82% more than in untreated control. Base oil-treated soil showed more dehydrogenase activity than that observed with NADF. Both NADF and base oil stimulated the soil dehydrogenase activity.  相似文献   

14.
Heavy metal pollution and their fractionations in the sediments of Changjiang River in Nanjing Reach was monitored for cadmium (Cd), lead (Pb), zinc (Zn), chromium (Cr), and copper (Cu). Moreover, the biological enrichment of metals by riverine plants was studied. The results demonstrated there were highly significant variations among different sampling stations for the concentrations of tested metals. The highest range was for Cu (38.8–120.4 mg kg−1), followed by Cr (74.4–120.0 mg kg−1), Zn (80.9–121.1 mg kg−1), Ni (26.0–55.5 mg kg−1), Pb (15.8–46.7 mg kg−1) and Cd (0.28–0.48 mg kg−1). Cd was the element with highest biological enrichment factor (BEF). The highest BEF of Cd in Erigeron bonariensis reached 3.0, indicating a significant Cd enrichment in this aquatic plant. In addition, 60% of Cd was found in reducible fraction and exchangeable and acid-soluble fraction, which was consistent with its high mobility. The consistency of Cd fraction in sediment and suspended particle indicated they came from the same source. Accumulated Cd concentration calculated according to the release curve showed significant relativity with the total Cd concentration in the sediment.  相似文献   

15.
A field survey was conducted to identify potential hyperaccumulators of Pb, Zn or Cd in the Beichang Pb/Zn mine outcrop in Yunnan Province, China. The average total concentrations of Pb, Zn, and Cd in the soils were up to 28,438, 5,109, and 52 mg kg−1, respectively. A total of 68 plant species belonging to 60 genera of 37 families naturally colonizing the outcrop were recorded. According to metal accumulation in the plants and translocation factor (TF), Silene viscidula was identified as potential hyperaccumulator of Pb, Zn, and Cd with mean shoot concentrations of 3,938 mg kg−1 of Pb (TF = 1.2), 11,155 mg kg−1 of Zn (TF = 1.8) and 236 mg kg−1 of Cd (TF = 1.1), respectively; S. gracilicanlis (Pb 3,617 mg kg−1, TF = 1.2) and Onosma paniculatum (Pb 1,837 mg kg−1, TF = 1.9) were potential Pb hyperaccumulators. Potentilla griffithii (Zn 8,748 mg kg−1, TF = 1.5) and Gentiana sp. (Zn 19,710 mg kg−1, TF = 2.7) were potential Zn hyperaccumulators. Lysimachia deltoides (Cd 212 mg kg−1, TF = 3.2) was a potential Cd hyperaccumulator. These new plant resources could be used to explore the mechanisms of Pb, Zn and/or Cd hyperaccumulation, and the findings could be applied for the phytoremediation of Pb, Zn and/or Cd-contaminated soils.  相似文献   

16.
Mineralization of organic matter (OM) in sediment is crucial for biogeochemical cycle of nitrogen (N) and phosphorus (P) in lake ecosystem. Light fraction OM (LFOM) is a reactive pool in sediment and is considered as labile fraction contributing to N and P cycling. In our study, the effect of LFOM on the process and characteristics of N and P mineralization in sediments of Taihu Lake were investigated with 77-day waterlogged incubation plus intermittent leaching at 27°C. Sediments from Yuantouzhu (Y) and Gonghu (G) were used, which were removed the LF. Results indicated that the organic nitrogen mineralized ranged from 14.3 to 19.5% of total nitrogen (193.49–378.93 mg kg−1 sediment) and the organic phosphorus mineralized ranged from 5.7 to 7.9% of total phosphorus (19.86–60.65 mg kg−1 sediment). The heavily polluted sediment had a higher mineralization rate and net mineral-N and mineral-P than slightly polluted sediment. LF stimulated the initial amounts of inorganic N and P and also can be the potential source for mineralization. After the LFOM removal, the net mineral-N of Y and G decreased 116.47 mg kg−1 sediment and 48.03 mg kg−1sediment, respectively, and the net mineral-P decreased 2.67 mg kg−1sediment for Y and 4.82 mg kg−1sediment for G. Two models were used to fit the observed mineral-N data vs. incubation days using a non-linear regression procedure: one is the effective cumulated temperature model, a thermodynamic model which assumes that N mineralization is affected by temperature; the other is the single first-order exponential model, which is a dynamic model. Based on root mean square error values for the two models, the effective cumulated temperature model made a better prediction of N mineralization than the other model for all the four treatments. The single first-order exponential model underestimated N mineralization during the first 14 days and the last 21 days, and overestimated it in the other days during the 77-day incubation. This indicated that temperature was the primary factor influencing N mineralization and the amount of mineral-N were correlated significantly with the effective cumulated temperature (T ≥ 15°C) and incubation time when waterlogged incubation plus intermittent leaching was used.  相似文献   

17.
Coal handling, crushing, washing, and other processes of coal beneficiation liberate coal particulate matter, which would ultimately contaminate the nearby soils. In this study, an attempt was made to determine the status of soil bio-indicators in the surroundings of a coal beneficiation plant, (in relation to a control site). The coal beneficiation plant is located at Sudamudih, and the control site is 5 km away from the contaminated site, which is located in the colony of Central Institute of Mining and Fuel Research Institute, Digwadih, Dhanbad. In order to estimate the impact of coal deposition on soil biochemical characteristics and to identify the most sensitive indicator, soil samples were taken from the contaminated and the control sites, and analyzed for soil organic carbon (SOC), soil N, soil basal respiration (BSR), substrate-induced respiration (SIR), and soil enzymes like dehydrogenase (DHA), catalase (CAT), phenol oxidase (PHE), and peroxidase (PER). Coal deposition on soils improved the SOC from 10.65 to 50.17 g kg−1, CAT from 418.1 to 804.11 μg H2O2 g−1 h−1, BSR from 8.5 to 36.15 mg CO2–C kg−1 day−1, and SIR from 24.3 to 117.14 mg CO2–C kg−1 day−1. Soils receiving coal particles exhibited significant decrease in DHA (36.6 to 4.22 μg TPF g−1 h−1), PHE (0.031 to 0.017 μM g−1 h−1), PER (0.153 to 0.006 μM g−1 h−1), and soil N (55.82 to 26.18 kg ha−1). Coal depositions significantly (P < 0.01) decreased the DHA to 8.8 times, PHE to 1.8 times, and PER to 25.5 times, but increased the SOC to 4.71 times, CAT to 1.9 times, SIR to 4.82 times, and BSR to 4.22 times. Based on principal component analysis and sensitivity test, soil peroxidase (an enzyme that plays a vital role in the degradation of the aromatic organic compounds) is found to be the most important indicator that could be considered as biomarkers for coal-contaminated soils.  相似文献   

18.
Nitrate pollution of groundwater in Toyserkan,western Iran   总被引：5，自引：2，他引：3  
A total of 95 groundwater samples were collected from Toyserkan, western Iran to assess the chemical composition and nitrate (NO3 −) status of groundwater. The most prevalent water type is Ca–HCO3 followed by water types Ca–Mg–HCO3. In comparison with the World Health Organization (WHO) drinking water guideline of 50 mg l−1 for NO3 −, a total of nine wells (9.5%) showed higher concentrations. In 36% of samples (34) NO3 − concentration was low (<20 mg l−1), and in 53.7% of samples (51), in the range of 20–50 mg l−1. The samples were classified into four groups based on NO3 − and chloride (Cl−) concentrations. Of the samples, 40% were classified as group 4 and were relatively high in Cl− and NO3 − (Cl− > 47 mg l−1, NO3 − > 27 mg l−1). The high correlation between NO3 − and Cl− (r = 0.86, p < 0.01) is consistent with a manure source, resulting from the practice of adding salt to animal feed. Pollution of groundwaters appeared to be affected by the application of inorganic fertilizer at greater than agronomic rates, Cl-salt inputs, and irrigation practice.  相似文献   

19.
This paper estimates CO2 fluxes in a municipal site for final disposal of solid waste, located in Gualeguaychu, Argentina. Estimations were made using the accumulation chamber methods, which had been calibrated previously in laboratory. CO2 fluxes ranged from 31 to 331 g m−2 day−1. Three different populations were identified: background soil gases averaging 46 g m−2 day−1, intermediate anomalous values averaging 110 g m−2 day−1 and high anomalous values averaging 270 g m−2 day−1. Gas samples to a depth of 20 cm were also taken. Gas fractions, XCO2 < 0.1, XCH4 < 0.01, XN2 ~0.71 and XO2 ~0.21, δ13C of CO2 (−34 to −18‰), as well as age of waste emplacement, suggest that the study site may be at the final stage of aerobic biodegradation. In a first approach, and following the downstream direction of groundwater flow, alkalinity and δ13C of dissolved inorganic carbon (−15 to 4‰) were observed to increase when groundwater passed through the disposal site. This suggests that the CO2 generated by waste biodegradation dissolves or that dissolved organic matter appears as a result of leachate degradation.  相似文献   

20.
We investigated the effects on phosphorus (P) release of the addition of potato, wheat, and sunflower residues and fruit compost to five calcareous soils. Residue was added at the rate of 20 g kg−1. After 2 months of incubation, P values in control and amended soils were used for kinetic studies and fractionated by a sequential extraction procedure. The relative contribution of available P fraction (KCl-P) increased from 1.4% in control soils to 1.8%, 1.9%, 2.2%, and 2.3% in soils amended by fruit, wheat, potato, and sunflower residue addition, respectively, indicating that organic residues increased P in this fraction. In soils amended with different residues, the percentage of Olsen-P released over 86-h successive extractions with 0.01 M CaCl2 ranged from 57.6% for fruit residue addition (average of five soils) to 60.5% for potato residue addition. The ability of residues to release P depended on the soil properties, with 21.9 mg kg−1 (average of all residues) released to soil 2 and 77.4 mg kg−1 released to soil 4. Also residues behaved differently, with 31.5 mg kg−1 (average of five soils) released by fruit residues and 40.0 mg kg−1 released by sunflower residues. Release of P was best described by a parabolic diffusion model. The corresponding rate constant (mg kg−1 h−1/2) for P release for amended soils, defined as the release rate averaged for five soils, was found to decrease in the order: potato (2.73) > sunflower (2.61) > wheat (2.56) > fruit (2.50). The present study demonstrates that addition of residues improves P availability of these calcareous soils by increasing extractable P and the release rate and could be an alternative, indigenous source of P. However, the increase in P availability and the release rate following organic residue application suggests high potential mobility to water sources.  相似文献   

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