Changes in soil quality indicators under long-term sewage irrigation in a sub-tropical environment   总被引：3，自引：0，他引：3  

Reginald Ebhin Masto  Pramod K. Chhonkar  Dhyan Singh  Ashok K. Patra 《Environmental Geology》2009,56(6):1237-1243

Though irrigation with sewage water has potential benefits of meeting the water requirements, the sewage irrigation may mess up to harm the soil health. To assess the potential impacts of long-term sewage irrigation on soil health and to identify sensitive soil indicators, soil samples were collected from crop fields that have been irrigated with sewage water for more than 20 years. An adjacent rain-fed Leucaena leucocephala plantation system was used as a reference to compare the impact of sewage irrigation on soil qualities. Soils were analyzed for different physical, chemical, biological and biochemical parameters. Results have shown that use of sewage for irrigation improved the clay content to 18–22.7%, organic carbon to 0.51–0.86% and fertility status of soils. Build up in total N was up to 2,713 kg ha⁻¹, available N (397 kg ha⁻¹), available P (128 kg ha⁻¹), available K (524 kg ha⁻¹) and available S (65.5 kg ha⁻¹) in the surface (0.15 m) soil. Long-term sewage irrigation has also resulted a significant build-up of DTPA extractable Zn (314%), Cu (102%), Fe (715%), Mn (197.2), Cd (203%), Ni (1358%) and Pb (15.2%) when compared with the adjacent rain-fed reference soil. Soils irrigated with sewage exhibited a significant decrease in microbial biomass carbon (−78.2%), soil respiration (−82.3%), phosphatase activity (−59.12%) and dehydrogenase activity (−59.4%). An attempt was also made to identify the sensitive soil indicators under sewage irrigation, where microbial biomass carbon was singled out as the most sensitive indicator.  相似文献   

Soil erosion determinations by using 137Cs technique in the agricultural regions of Gediz Basin, Western Turkey     

M. M. Saç  E. Yumurtaci  G. Yener  B. Camgöz  A. Uğur  B. Özden 《Environmental Geology》2008,55(3):477-483

Gediz Basin is one of the regions where intense agricultural activities take place in Western Turkey. Erosion and soil degradation have long been causing serious problems to cultivated fields in the basin. This work describes the application of two different ¹³⁷Cs models for estimating soil erosion rates in cultivated sites of the region. Soil samples were collected from five distinct cultivated regions subject to soil erosion. The variations of ¹³⁷Cs concentrations with depth in soil profiles were investigated. Soil loss rates were calculated from ¹³⁷Cs inventories of the samples using both proportional model (PM) and simplified mass balance model (SMBM). When PM was used, erosion and deposition rates varied from −15 to −28 t ha⁻¹ year⁻¹ and from +5 to +41 t ha⁻¹ year⁻¹, respectively; they varied from −16 to −33 t ha⁻¹ year⁻¹ and from +5 to +55 t ha⁻¹ year⁻¹ with SMBM. A good agreement was observed between the results of two models up to 30 t ha⁻¹ year⁻¹ soil loss and gain in the study area. Ulukent, a small representative agricultural field, was selected to compare the present data of ¹³⁷Cs techniques with the results obtained by universal soil loss equation (USLE) applied in the area before.  相似文献   

Mapping of total nitrogen,available phosphorous and potassium in Amik Plain,Turkey   总被引：1，自引：0，他引：1  

Veli Uygur  Ahmet Irvem  Sema Karanlik  Rifat Akis 《Environmental Earth Sciences》2010,59(5):1129-1138

Soil nitrogen, phosphorous, and potassium concentrations accurately revealed spatial distribution maps and site-specific management-prone areas through inverse distance weighting (IDW) method in the Amik Plain, Turkey. Spatial mapping of soil nitrogen, phosphorous, and potassium is a very severe need to develop an economically and environmentally sound soil management plans. The objectives of this study were (a) to map spatial variability of total N, available P, and exchangeable-K content of Amik Plain’s soils and (b) to locate problematic areas requiring site specific management strategies for the nutrient elements. Spatial analyses of Kjeldhal-N, Olsen-P, and exchangeable-K concentrations of the soils were performed by the IDW method. Mean N content for surface soils (0–20 cm) was 1.38 g kg⁻¹, available P was 28.19 kg ha⁻¹ and exchangeable-K was 690 kg ha⁻¹ with the differences between maximum and minimum being 7.63 g N kg⁻¹, 242 kg P ha⁻¹, and 2,082 kg K ha⁻¹. For the surface soil, site-specific management-prone areas of Kjeldahl-N, Olsen-P, and exchangeable-K for “low and high + very high” classes were found to be 20.1–17.8%, 24.7–10.0%, and 4.1–39.6%, respectively. Consequently, lands with excessive nutrient elements require preventive-leaching practices, whereas nutrient-poor areas need fertilizer applications in favor of increasing plant production.  相似文献   

Selection of bioindicators in coal-contaminated soils of Dhanbad,India     

R. E. Masto  L. C. Ram  P. R. Shandilya  S. Sinha  J. George  V. A. Selvi 《Environmental Earth Sciences》2011,64(4):1107-1115

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   

Weathering fluxes of arsenic from a small catchment in Slovak Republic   总被引：1，自引：1，他引：0  

Ahmed Melegy  Igor Slaninka  Tomas Pa?es  Stanislav Rapant 《Environmental Earth Sciences》2011,64(2):549-555

Inputs of As to a small catchment due to chemical weathering of bedrock, mechanical weathering of bedrock, and atmospheric precipitation were 71.53, 23.98 and 0.02 g ha⁻¹ year⁻¹, respectively. The output fluxes of As due to mechanical erosion of soil, biological uptake, stream discharge, and groundwater flow were 6.32, 4.77, 0.37 and 0.02 g ha⁻¹ year⁻¹, respectively. The results indicate that arsenic accumulates in soil and regolith with a very high rate. This is attributed to the selective weathering and erosion with respect to arsenic and fixation of arsenic in the secondary solids produced by weathering. The output fluxes of As in stream and groundwater in Vydrica catchment in Slovak Republic (0.39 g ha⁻¹ year⁻¹) based on muscovite–biotite granites and granodiorites were much lower compared to catchments in a gold district in the Czech Republic. These results may be ascribed to the low levels of arsenic pollution measured in Vydrica catchment. The arsenic fluxes were estimated by calculation of mechanical and chemical weathering rates of the bedrocks in Vydrica catchment from mass balance data on sodium and silica. The justification of the steady state of Na and Si is that neither of the elements is appreciably accumulated in plants and in exchangeable pool of ions in soil.  相似文献   

Contribution of a Dense Population of the Brittle Star <Emphasis Type="Italic">Acrocnida brachiata</Emphasis> (Montagu) to the Biogeochemical Fluxes of CO<Subscript>2</Subscript> in a Temperate Coastal Ecosystem     

Dominique Davoult  Jérôme Harlay  Franck Gentil 《Estuaries and Coasts》2009,32(6):1103-1110

The production of organic matter and calcium carbonate by a dense population of the brittle star Acrocnida brachiata (Echinodermata) was calculated using demographic structure, population density, and relations between the size (disk diameter) and the ash-free dry weight (AFDW) or the calcimass. During a 2-year survey in the Bay of Seine (Eastern English Channel, France), organic production varied from 29 to 50 g_AFDW m⁻² year⁻¹ and CaCO₃ production from 69 to 104 g_CaCO3 m⁻² year⁻¹. Respiration was estimated between 1.7 and 2.0 mol_CO2 m⁻² year⁻¹. Using the molar ratio (ψ) of CO₂ released: CaCO₃ precipitated, this biogenic precipitation of calcium carbonate would result in an additional release between 0.5 and 0.7 mol_CO2 m⁻² year⁻¹ that represented 23% and 26% of total CO₂ fluxes (sum of calcification and respiration). The results of the present study suggest that calcification in temperate shallow environments should be considered as a significant source of CO₂ to seawater and thus a potential source of CO₂ to the atmosphere, emphasizing the important role of the biomineralization (estimated here) and dissolution (endoskeletons of dead individuals) in the carbon budget of temperate coastal ecosystems.  相似文献   

Erosion rates evaluated by the <Superscript>137</Superscript>Cs technique in the high altitude area of the Qinghai–Tibet plateau of China     

Yibo Wang  Genxu Wang  Hongchang Hu  Huiyan Cheng 《Environmental Geology》2008,53(8):1743-1749

Studying spatial and temporal variation of soil loss is of great importance because of global environmental concerns. Understanding the spatial distribution of soil erosion and deposition in the high-cold steppe is important for designing soil and water conservation measures. Measured ¹³⁷Cs losses (Bq m⁻²) from long-term high altitude (4,000 m above sea level) watershed plots on the Qinghai–Tibet plateau and derived soil erosion estimates (Mg ha⁻¹ year⁻¹) were significantly correlated to directly measured soil losses from the same plots, over the same period (1963–2005). The local reference inventory was estimated to be 2,468 Bq m⁻². The result of analyzing ¹³⁷Cs distribution and its intensity in the soil profiles in this area shows similarities to ¹³⁷Cs distribution in other areas. ¹³⁷Cs is basically distributed in the topsoil layer of 0–0.3 m. Soil erosions vary greatly in the entire sampled area, ranging from 5.5 to 23 Mg ha⁻¹ year⁻¹, with an average of 16.5 Mg ha⁻¹ year⁻¹ which is a moderate rate of erosion.  相似文献   

Respiration and Calcification of <Emphasis Type="Italic">Crassostrea gigas</Emphasis>: Contribution of an Intertidal Invasive Species to Coastal Ecosystem CO<Subscript>2</Subscript> Fluxes     

Morgane Lejart  Jacques Clavier  Laurent Chauvaud  Christian Hily 《Estuaries and Coasts》2012,35(2):622-632

Respiration and calcification rates of the Pacific oyster Crassostrea gigas were measured in a laboratory experiment in the air and underwater, accounting for seasonal variations and individual size, to estimate the effects of this exotic species on annual carbon budgets in the Bay of Brest, France. Respiration and calcification rates changed significantly with season and size. Mean underwater respiration rates, deducted from changes in dissolved inorganic carbon (DIC), were 11.4 μmol DIC g⁻¹ ash-free dry weight (AFDW) h⁻¹ (standard deviation (SD), 4.6) and 32.3 μmol DIC g⁻¹ AFDW h⁻¹ (SD 4.1) for adults (80–110 mm shell length) and juveniles (30–60 mm), respectively. The mean daily contribution of C. gigas underwater respiration (with 14 h per day of immersion on average) to DIC averaged over the Bay of Brest population was 7.0 mmol DIC m⁻² day⁻¹ (SD 8.1). Mean aerial CO₂ respiration rate, estimated using an infrared gas analyzer, was 0.7 μmol CO₂ g⁻¹ AFDW h⁻¹ (SD 0.1) for adults and 1.1 μmol CO₂ g⁻¹ AFDW h⁻¹ (SD 0.2) for juveniles, corresponding to a mean daily contribution of 0.4 mmol CO₂ m⁻² day⁻¹ (SD 0.50) averaged over the Bay of Brest population (with 10 h per day of emersion on average). Mean CaCO₃ uptake rates for adults and juveniles were 4.5 μmol CaCO₃ g⁻¹ AFDW h⁻¹ (SD 1.7) and 46.9 μmol CaCO₃ g⁻¹ AFDW h⁻¹ (SD 29.2), respectively. The mean daily contribution of net calcification in the Bay of Brest C. gigas population to CO₂ fluxes during immersion was estimated to be 2.5 mmol CO₂ m⁻² day⁻¹ (SD 2.9). Total carbon release by this C. gigas population was 39 g C m⁻² year⁻¹ and reached 334 g C m⁻² year⁻¹ for densely colonized areas with relative contributions by underwater respiration, net calcification, and aerial respiration of 71%, 25%, and 4%, respectively. These observations emphasize the substantial influence of this invasive species on the carbon cycle, including biogenic carbonate production, in coastal ecosystems.  相似文献   

Nitrogen Pools of Macrophyte Species in a Coastal Lagoon Salt Marsh: Implications for Seasonal Storage and Dispersal     

Tracy Elsey-Quirk  Denise M. Seliskar  John L. Gallagher 《Estuaries and Coasts》2011,34(3):470-482

High nitrogen (N) loading rates received by coastal bays can have deleterious effects on aquatic ecosystems. Salt marshes can intercept land-based N through seasonal plant uptake, denitrification, and burial. Salt marshes fringing Delaware’s Inland Bays are characterized by different plant species occurring in close proximity. To evaluate N pool retention and loss for the dominant plant species, we measured seasonal N concentration and pool size, N resorption efficiency, loss during decomposition, and soil N. Seasonal variation in N pools and fluxes differed among species. Seasonal differences in the total N pools of the herbaceous species were largely influenced by belowground fine root and dead macro-organic matter fluxes. N production rate estimates ranged from 18 g N m⁻² year⁻¹ aboveground for the high marsh shrub to 40.8 g N m⁻² year⁻¹ above- and belowground for the high marsh rush illustrating the importance of incorporating species-specific dynamics into ecosystem N budgets.  相似文献   

Soil erosion risk assessment of the Keiskamma catchment,South Africa using GIS and remote sensing   总被引：4，自引：2，他引：2  

Paidamwoyo Mhangara  Vincent Kakembo  Kyoung Jae Lim 《Environmental Earth Sciences》2012,65(7):2087-2102

This paper examines the soil loss spatial patterns in the Keiskamma catchment using the GIS-based Sediment Assessment Tool for Effective Erosion Control (SATEEC) to assess the soil erosion risk of the catchment. SATEEC estimates soil loss and sediment yield within river catchments using the Revised Universal Soil Loss Equation (RUSLE) and a spatially distributed sediment delivery ratio. Vegetation cover in protected areas has a significant effect in curtailing soil loss. The effect of rainfall was noted as two pronged, higher rainfall amounts received in the escarpment promote vegetation growth and vigour in the Amatole mountain range which in turn positively provides a protective cover to shield the soil from soil loss. The negative aspect of high rainfall is that it increases the rainfall erosivity. The Keiskamma catchment is predisposed to excessive rates of soil loss due to high soil erodibility, steep slopes, poor conservation practices and low vegetation cover. This soil erosion risk assessment shows that 35% of the catchment is prone to high to extremely high soil losses higher than 25 ton ha⁻¹ year⁻¹ whilst 65% still experience very low to moderate levels of soil loss of less than 25 ton ha⁻¹ year⁻¹. Object based classification highlighted the occurrence of enriched valley infill which flourishes in sediment laden ephemeral stream channels. This occurrence increases gully erosion due to overgrazing within ephemeral stream channels. Measures to curb further degradation in the catchment should thrive to strengthen the role of local institutions in controlling conservation practice.  相似文献   

Comparison of soil organic carbon content,hydraulic conductivity,and particle size fractions between a grassland and a nearby black pine plantation of 40 years in two surface depths   总被引：2，自引：0，他引：2  

Ilhami Bayramin  Mustafa Basaran  Gunay Erpul  Melda Dolarslan  Mustafa R. Canga 《Environmental Geology》2009,56(8):1563-1575

In highlands of semiarid Turkey, ecosystems have been significantly transformed through human actions, and today changes are taking place very rapidly, causing harmful consequences such as soil degradation. This paper examines two neighboring land use types in Indagi Mountain Pass, Cankiri, Turkey, to determine effects of the conversion of Blackpine (Pinus nigra Arn. subsp. pallasiana) plantation from grassland 40 years ago on soil organic carbon (SOC) and soil erodibility (USLE-K). For this purpose, a total of 302 disturbed and undisturbed soil samples were taken at irregular intervals from two sites and from two soil depths of 0–10 cm (D₁) and 10–20 cm (D₂). In terms of SOC, conversion did not make any statistical difference between grassland and plantation; however, there were statistically significant differences with soil depth within each land use, and SOC contents significantly decreased with the soil depth (P < 0.05) and mostly accumulated in D₁. SOC values were 2.4 and 1.8% for grassland and 2.8 and 1.6% for plantation, respectively, at D₁ and D₂. USLE-K values also statistically differed significantly with the land use, and in contrast to the statistics of SOC, there was no change in USLE-K with the soil depth. Since USLE-K was estimated using SOC, hydraulic conductivity (HC) and soil textural composition––sand (S), silt (Si), and clay (C) contents of soils––as well as SOC did not change with the land use, we ascribed the changes of USLE-K with the land uses to the differences in the HC as strongly affected by the interactions between SOC and contents of S, Si, and C. On an average, the soil of the grassland (USLE-K = 0.161 t ha h ha⁻¹ MJ⁻¹ mm⁻¹) was more erodible than those of the plantation (USLE-K = 0.126 t ha h ha⁻¹ MJ⁻¹ mm⁻¹). Additionally, topographic factors, such as aspect and slope, were statistically effective on spatial distribution of the USLE-K and SOC.  相似文献   

Quantifying Annual Nitrogen Loads to Virginia’s Coastal Lagoons: Sources and Water Quality Response   总被引：3，自引：0，他引：3  

Juliette Christina Poleto Giordano  Mark J. Brush  Iris C. Anderson 《Estuaries and Coasts》2011,34(2):297-309

Coastal lagoons of the Delmarva Peninsula receive varying annual nitrogen loads because of differing land uses. Extensive development and agriculture contribute to elevated nutrient loads in Maryland and Delaware. Agriculture and forests dominate Virginia’s landscape, suggesting these systems receive lower loads. We used a watershed model to achieve three objectives: (1) quantify loads to Virginia lagoons; (2) determine the sources of the loads; and (3) project changes in annual loads under different development scenarios. Model simulations indicated that some Virginia lagoons receive relatively high annual nutrient loads (kg N year⁻¹) due to intensive agriculture and a high watershed/lagoon areal ratio. Model projections also suggested that increased agricultural and residential development in Virginia could lead to annual loads (kg N year⁻¹) typical of impacted Maryland systems. A comparison of Maryland and Virginia water quality responses to nutrient loading suggested that Virginia’s lagoons exhibit a different response to nutrient loading, though the exact mechanism for this difference is unclear.  相似文献   

Soil erosion modeling of a Himalayan watershed using RS and GIS   总被引：5，自引：1，他引：4  

Ashish Pandey  Abhisekh Mathur  S. K. Mishra  B. C. Mal 《Environmental Earth Sciences》2009,59(2):399-410

Employing the remote sensing (RS) and geographical information system (GIS), an assessment of sediment yield from Dikrong river basin of Arunachal Pradesh (India) has been presented in this paper. For prediction of soil erosion, the Morgan-Morgan and Finney (MMF) model and the universal soil loss equation (USLE) have been utilized at a spatial grid scale of 100 m × 100 m, an operational unit. The average annual soil loss from the Dikrong river basin is estimated as 75.66 and 57.06 t ha⁻¹ year⁻¹ using MMF and USLE models, respectively. The watershed area falling under the identified very high, severe, and very severe zones of soil erosion need immediate attention for soil conservation.  相似文献   

Marine Macrophyte Wrack Inputs and Dissolved Nutrients in Beach Sands     

Jenifer E. Dugan  David M. Hubbard  Henry M. Page  Joshua P. Schimel 《Estuaries and Coasts》2011,34(4):839-850

We investigated the role of sandy beaches in nearshore nutrient cycling by quantifying macrophyte wrack inputs and examining relationships between wrack accumulation and pore water nutrients during the summer dry season. Macrophyte inputs, primarily giant kelp Macrocystis pyrifera, exceeded 2.3 kg m⁻¹ day⁻¹. Mean wrack biomass varied 100-fold among beaches (range = 0.41 to 46.43 kg m⁻¹). Mean concentrations of dissolved inorganic nitrogen (DIN), primarily NO_x⁻-N, and dissolved organic nitrogen (DON) in intertidal pore water varied significantly among beaches (ranges = 1 to 6,553 μM and 7 to 2,006 μM, respectively). Intertidal DIN and DON concentrations were significantly correlated with wrack biomass. Surf zone concentrations of DIN were also strongly correlated with wrack biomass and with intertidal DIN, suggesting export of nutrients from re-mineralized wrack. Our results suggest beach ecosystems can process and re-mineralize substantial organic inputs and accumulate dissolved nutrients, which are subsequently available to nearshore waters and primary producers.  相似文献   

Whole Ecosystem Evidence of Eutrophication Enhancement by Wetland Dredging in a Shallow Tropical Lake     

Humberto Marotta  Luiz Bento  Francisco de A. Esteves  Alex Enrich-Prast 《Estuaries and Coasts》2009,32(4):654-660

The purpose of this research was to assess the effects of dredging performed in a marginal wetland colonized by aquatic macrophytes on eutrophication of the adjacent shallow tropical lake (Imboassica Lake, Brazil). The river mouth of the Imboassica River that drains into Imboassica Lake had been densely colonized by aquatic vegetation dominated by Typha domingensis (Pers.) when it was dredged. Total and dissolved nitrogen and phosphorus concentrations were measured monthly over 13 years at four stations in the Imboassica river-lake system. Dredging activities reduced phosphorus and nitrogen retention at the river mouth and subsequently increased these nutrient stocks in the lake waters. Nutrient retention by non-dredged wetland was estimated to be ca. 1,200 kg year⁻¹ (87.3 g m⁻² year⁻¹) for nitrogen and 60 kg year⁻¹ (4.5 g m⁻² year⁻¹) for phosphorus. Our whole-lake approach suggested that dredging might intensify rather than mitigate eutrophication in shallow tropical lakes when the removal of aquatic macrophytes is coupled to the persistence of anthropogenic nutrient inputs from the watershed.  相似文献   

Soil organic carbon storage changes in Yangtze Delta region,China   总被引：1，自引：1，他引：0  

Xu Naizheng  Zhang Taolin  Wang Xingxiang  Liu Hongying 《Environmental Earth Sciences》2011,63(5):1021-1028

Soil carbon sequestration plays an essential role in mitigating CO₂ increases and the global greenhouse effect. This paper calculates soil organic carbon (SOC) storage changes during the course of industrialization and urbanization in Yangtze Delta region, China, based on the data of the second national soil survey (1982–1985) and the regional geochemical survey (2002–2005), with the help of remote sensing images acquired in periods of 1980, 2000, 2005. The results show that soils in the top 0–20 and 0–100 cm depth in this region demonstrate the carbon sink effect from the early 1980s to the early 2000s. The SOC storage in 0–20 cm depth has resulted in increase from 213.70 to 238.65 Tg, which corresponds to the SOC density increase from 2.94 ± 1.08 to 3.28 ± 0.92 kg m⁻², and mean carbon sequestration storage and rate are 1.25 Tg a⁻¹, 17.14 g m⁻² a⁻¹, respectively. The SOC storage in 0–100 cm depth has resulted in increase from 690.26 to 792.65 Tg, which corresponds to the SOC density increase from 9.48 ± 4.22 to 10.89 ± 3.42 kg m⁻², and mean carbon sequestration storage and rate are 5.12 Tg a⁻¹, 70.32 g m⁻² a⁻¹, respectively. Urban area in Yangtze Delta region, China, increased more than 3,000 km² and the urban growth patterns circled the central city region in the past 20 years. The SOC densities in 0–20 cm depth decrease gradually along urban–suburban–countryside and the urban topsoil is slightly enriched with SOC. Compared to the data of the second national soil survey in the early 1980s, the mean SOC density in urban area increased by 0.76 kg m², or up 25.85% in the past 20 years. With the characteristics of SOC storage changes offered, land-use changes, farming system transition and ecological city construction are mainly attributed to SOC storage increases. Because of lower SOC content in this region, it is assumed that the carbon sink effect will go on in the future through improved soil management.  相似文献   

Groundwater nitrate contamination and risk assessment in an agricultural area,South Korea   总被引：2，自引：1，他引：1  

Jae-Yeol Cheong  Se-Yeong Hamm  Jeong-Hwan Lee  Kwang-Sik Lee  Nam-Chil Woo 《Environmental Earth Sciences》2012,66(4):1127-1136

The nitrate of groundwater in the Gimpo agricultural area, South Korea, was characterized by means of nitrate concentration, nitrogen-isotope analysis, and the risk assessment of nitrogen. The groundwaters belonging to Ca–(Cl + NO₃) and Na–(Cl + NO₃) types displayed a higher average NO₃ ⁻ concentration (79.4 mg/L), exceeding the Korean drinking water standard (<44.3 mg/L NO₃ ⁻). The relationship between δ¹⁸O–NO₃ ⁻ values and δ¹⁵N–NO₃ ⁻ values revealed that nearly all groundwater samples with δ¹⁵N–NO₃ ⁻ of +7.57 to +13.5‰ were affected by nitrate from manure/sewage as well as microbial nitrification and negligible denitrification. The risk assessment of nitrate for groundwater in the study area was carried out using the risk-based corrective action model since it was recognized that there is a necessity of a quantitative assessment of health hazard, as well as a simple estimation of nitrate concentration. All the groundwaters of higher nitrate concentration than the Korean drinking water standard (<44.3 mg/L NO₃ ⁻) belonged to the domain of the hazard index <1, indicating no health hazard by nitrate in groundwater in the study area. Further, the human exposure to the nitrate-contaminated soil was below the critical limit of non-carcinogenic risk.  相似文献   

Patterns of mangrove forest structure and soil nutrient dynamics along the Shark River estuary, Florida   总被引：1，自引：0，他引：1  

Ronghua Chen  Robert R. Twilley 《Estuaries and Coasts》1999,22(4):955-970

The basal area and productivity of managrove wetlands are described in relation to selected soil properties to understand the general pattern of optimum forest stature at the mouth of estuaries in the Everglades, such as the Shark River Slough, Florida (U.S.). The basal area of mangroves decreases from 40.4 m² ha⁻¹ and 39.7 m² ha⁻¹ at two stations 1.8 km and 4.1 km from the estuary mouth to 20.7 m² ha⁻¹ and 19.6 m² ha⁻¹ at two sites 9.9 km and 18.2 km from the mouth, respectively. The gradient in basal area at these four sites is mostly the result of approximately 34 yr of growth since Hurricane Donna. Wood productivity is higher in the lower estuary (10.7 Mg ha⁻¹ yr⁻¹ and 12.0 Mg ha⁻¹ yr⁻¹) than in the upper estuary (3.2 Mg ha⁻¹ yr⁻¹ and 4.2 Mg ha⁻¹ yr⁻¹). Porewater salinity among these four mangrove sites during seasonal sampling in 1994 and 1995 ranged from 1.6 g kg⁻¹ to 33.5 g kg⁻¹, while sulfide was generally<0.15 mM at all sites. These soil values indicate that abiotic stress cannot explain the decrease in forest structure along this estuarine gradient. Concentrations of nitrogen (N) and phosphorus (P) are more closely related to patterns of forest development, with higher soil fertility at the mouth of the estuary as indicated by higher concentrations of extractable ammonium, total soil P, and available P, along with higher ammonium production rates. The more fertile sites of the lower estuary are dominated by Laguncularia racemosa, whereas the less fertile sites in the intermediate and upper estuary are dominated by Rhizophora mangle. Relative N mineralization per unit of total N is higher in the lower estuary and is related positively to concentrations of available P, indicating the importance of turnover rates and nutrient interactions to soil fertility. Concentrations of Ca-bound P per volume soil in the lower estuary is 40-fold higher than in the upper estuary, and along with an increase in residual P in the upper estuary, indicate a shift from mineral to organic P along the estuarine gradient. Mineral inputs to the mouth of Shark River estuary from the Gulf of Mexico (rather than upland inputs) apparently control the patterns of mangrove structure and productivity.  相似文献   

<Superscript>210</Superscript>Pb-derived Sedimentation Rates and C<Subscript>org</Subscript> Fluxes in Soledad Lagoon (Cispatá Lagoon System,NW Caribbean Coast of Colombia)     

Ana Carolina Ruiz-Fernández  José Luis Marrugo-Negrete  Roberth Paternina-Uribe  Libia Hascibe Pérez-Bernal 《Estuaries and Coasts》2011,34(6):1117-1128

With the aim of evaluating temporal changes in sedimentation and organic carbon (C_org) supplied over the last ~100 years, a sediment core was collected at Soledad Lagoon, a costal ecosystem surrounded by mangroves, located in the Cispatá Estuary (Caribbean coast of Colombia). The core sediments were characterized by low concentrations of calcium carbonate (0.2–2.9%), organic matter (3–8%), total nitrogen (0.11–0.38%), and total phosphorus (0.19–0.65 mg g⁻¹). Fe and Al concentrations ranged from 4% to 5%, and Mn from 356 to 1,047 μg g⁻¹. The ²¹⁰Pb-derived sediment and mass accumulation rates were 1.54 ± 0.18 mm year⁻¹ and 0.08 ± 0.01 g cm⁻² year⁻¹, respectively. The sediment core did not provide evidence of human impact, such as enhancement of primary production or nutrient enrichment, which may result from recent land uses changes or climate change. The C_org fluxes estimated for Soledad Lagoon core lay in the higher side of carbon fluxes to coastal ecosystems (314–409 g m⁻² year⁻¹) and the relatively high C_org preservation observed (~45%) indicate that these lagoon sediments has been a net and efficient sink of C_org during the last century, which corroborate the importance of mangrove areas as important sites for carbon burial and therefore, long-term sequestration of C_org.  相似文献   

Analysis of the spatial and temporal changes in soil CO<Subscript>2</Subscript> flux in alpine meadow of Qilian Mountain     

Zongqiang Chang  Qi Feng  Jianhua Si  Yonghong Su  Haiyang Xi  Jianlin Li 《Environmental Geology》2009,58(3):483-490

Field experiments on the CO₂ flux of alpine meadow soil in the Qilian Mountain were conducted along the elevation gradient during the growing season of 2004 and 2005. The soil CO₂ flux was measured using the Li-6400-09 soil respiration chamber attached to the Li-6400 portable photosynthesis system. The effects of water and heat and roots on the soil CO₂ flux were statistically analyzed. The results show that soil CO₂ flux along the elevation gradient gradually decreases. The soil CO₂ flux was low at night, with lowest value occurring between 0200 and 0600 hours, started to rise rapidly during 0700–0830 hours, and then descend during 1600–1830 hours. The peak CO₂ efflux appears during 1100–1600 hours. The diurnal average of soil CO₂ efflux was between 0.56 ± 0.32 and 2.53 ± 0.76 μmol m⁻² s⁻¹. Seasonally, soil CO₂ fluxes are relatively high in summer and autumn and low in spring and winter. The soil CO₂ efflux, from the highest to the lowest in the ranking order, occurred in July and August (4.736 μmol m⁻² s⁻¹), June and September, and May and October, respectively. The soil CO₂ efflux during the growing season is positively correlated with soil temperature, root biomass and soil water content.  相似文献