Wetland Simulation Model for Nitrogen, Phosphorus, and Sediments Retention in Constructed Wetlands

Steamboat Creek, Washoe County, Nevada, is considered the most polluted tributary of the Truckee River, therefore the reduction of nutrients from the creek is an important factor in reducing eutrophication in the lower Truckee River. Restoration of the wetlands along the creek has been proposed as one method to improve water quality by reducing nutrient and sediments from non-point sources. This study was aimed to design a simulation model wetlands water quality model (WWQM) that evaluates nitrogen, phosphorus, and sediments retention from a constructed wetland system. WWQM is divided into four submodels: hydrological, nitrogen, phosphorus, and sediment. WWQM is virtual Visual Basic 6.0 program that calculates hydrologic parameters, nutrients, and sediments based on available data, simple assumptions, knowledge of the wetland system, and literature data. WWQM calibration and performance was evaluated using data sets obtained from the pilot-scale constructed wetland over a period of four and half years. The pilot-scale wetland was constructed to quantify the ability of the proposed wetland system for nutrient and sediment removal. WWQM simulates nutrient and sediments retention reasonably well and agrees with the observed values from the pilot-scale wetland system. The model predicts that wetlands along the creek will remove nitrogen, phosphorus, and sediments by 62, 38, and 84 %, respectively, which would help to reduce eutrophication in the lower Truckee River.     

Trophodynamic structure of a swampy bog at the clymax stage of limnological succssion I. Prmary production dynamics

Effect of emergent vegetation on the population dynamics of phytoplankton community in Matsumi-ike Bog, a typical bog at the climax stage of limnological succession, was studied. The emergent vegetation grew until August and then withered and collapsed mainly during December and January, supplying the debris of emergent plants into the water column. Population density of the predominant phytoplankton showed sinusoidal fluctuation affected primarily by the water temperature, with various lag phases due to the function of other environmental factors. Shading by the emergent vegetation shifted the initiation of phytoplankton fluctuation earlier. This fluctuation patterns was most obvious among those phytoplankton contain chlorophyll-a and -b, but non -a and-c. The population dynamics were also compared with that of Matsumi-ike Bog at premature stages without (8 yr ago) or with littoral vegetations (3 yr ago). The population density of phytoplankton with chlorophyll-b decreased but those with chlorophyll-c increased, due to the shading effect of the emergent vegetation with the limnological succession of the bog. At the climax of succession, the dynamic state of phytoplankton community has become more stable.     

Treatment Efiiciencies of Constructed Wetlands for Eutrophic Landscape River Water

The efficiencies of two types of constructed wetlands for the treatment of low-concentration polluted eutrophic landscape river water were studied in the western section of the Qingyuan River at the Minhang campus of Shanghai Jiaotong University. The first wetland was a single-stage system using gravel as a filtration medium, and the second was a three- stage system filled with combinations of gravel, zeolite, and fly ash. Results from parallel operations of the wetlands showed that the three-stage constructed wetland could remove organics, nitrogen, and phosphorus successfully. At the same time, it could also decrease ammoniacal odour in the effluent. Compared to the single-stage constructed wetland, it had better nutrient removal efficiencies with a higher removal of 19.37%-65.27% for total phosphorus （TP） and 21.56%- 62.94% for total nitrogen （TN）, respectively, during the operation period of 14 weeks. In terms of removal of chemical oxygen demand （COD）, turbidity, and blue-green algae, these two wetland systems had equivalent performances. It was also found that in the western section of the test river, in which the two constructed wetlands were located, the water quality was much better than that in the eastern and middle sections without constructed wetland because COD, TN, and TP were all in a relatively lower level and the eutrophication could be prevented completely in the western section.     

湿地植物对富营养化水体中氮、磷吸收能力研究

用营养液培养方法研究了11种湿地植物对氮、磷的吸收能力。结果表明,湿地植物平均生物量变化范围在9.31～49.53.g/plant(干重)之间;其地上部分与地下部分生物量的比值在1.21～3.09之间。美人蕉、菩提子、凤眼莲和芦苇有较高的地上部分生物量,而麦冬的地上部分生物量较低。地上部分植株氮、磷含量变化范围分别是22.13～33.03.mg/g和2.53～5.38.mg/g(以干重计算);湿地植物对氮、磷的吸收量分别是252.99～1279.98和23.55～251.83.mg/plant,对氮、磷去除率分别是10.91%～59.32%和50.13%～87.26%。氮和磷的吸收主要受湿地植物生物量的影响,美人蕉、菩提子、凤眼莲和芦苇对氮、磷都有较好的吸收能力。     

两种人工湿地处理富营养化景观水体的性能对比研究

The efficiencies of two types of constructed wetlands for the treatment of low-concentration polluted eutrophic land-scape river water were studied in the western section of the Qingyuan River at the Minhang campus of Shanghai Jiaotong University. The first wetland was a single-stage system using gravel as a filtration medium, and the second was a three-stage system filled with combinations of gravel, zeolite, and fly ash. Results from parallel operations of the wetlands showed that the three-stage constructed wetland could remove organics, nitrogen, and phosphorus successfully. At the same time, it could also decrease ammoniacal odour in the effluent. Compared to the single-stage constructed wetland, it had better nutrient removal efficiencies with a higher removal of 19.37%-65.27% for total phosphorus (TP) and 21.56%-62.94% for total nitrogen (TN), respectively, during the operation period of 14 weeks. In terms of removal of chemical oxygen demand (COD), turbidity, and blue-green algae, these two wetland systems had equivalent performances. It was also found that in the western section of the test river, in which the two constructed wetlands were located, the water quality was much better than that in the eastern and middle sections without constructed wetland because COD, TN, and TP were all in a relatively lower level and the eutrophication could be prevented completely in the western section.     

超高产夏玉米养分限制因子及养分吸收积累规律研究

2007年和2008年通过大田试验研究了超高产夏玉米养分限制因子和植株养分吸收积累规律。结果表明:用ASI法推荐的氮、磷、钾平衡施肥产量最高,分别达到12051.2 kg/hm2和13246.3 kg/hm2,施用氮肥平均增产8.92%,钾肥平均增产7.14%,增产效果显著,氮和钾为超高产夏玉米养分主要限制因子。超高产夏玉米植株体内氮、磷、钾的积累量均随生育期的延长而增加,到成熟期达到最大值,养分积累量的大小顺序为氮钾磷,每生产100 kg经济产量吸收养分比例N∶P2O5∶K2O为2.40∶1∶2.73。拔节期至吐丝期是养分吸收的关键时期,养分吸收速率大,积累量高,吐丝后植株仍能吸收较多的氮、磷。从出苗到吐丝期,叶片是氮、磷的分配中心,生育后期茎叶中氮、磷的转运率较高,而钾转移比例较小。超高产夏玉米整个生育期能持续吸收养分,吐丝后适当追肥保证灌浆期养分充足供应对夏玉米超高产至关重要。     

多级串联表面流人工湿地净化生活污水效果

农村生活污水已经成为农业面源污染的主要来源之一。为了研究如何在经济发展水平不高的农村建立能有效治理农村生活污水,且建设成本低、运行维护简单的人工湿地系统,该文通过在桂林市青狮潭灌区构建了多级串联的表面流人工湿地系统,研究分析了不同子系统的水质净化效果及相关检测指标浓度的沿程变化规律。研究结果表明,湿地系统对氮磷的去除效率总体呈现出随时间推移逐渐下降的趋势,同时湿地的表面积越大,其对氮磷的去除率越高。研究还发现,该湿地系统对高浓度进水具有快速、稳定的去除效果,而对低浓度进水的营养盐去除则表现得较为平缓和持久。通过对湿地系统沿程氮磷浓度衰减的拟合及回归分析,建立了与湿地系统进口浓度有关的TN、NH4+-N和TP浓度的沿程衰减模型,相关分析表明其最佳的拟合模型均为指数衰减模型。该湿地系统在整个试验时期内均表现出了良好的净化效果,有效地减轻了农村生活污水对外界水环境的破坏,指数衰减模型的建立也为后续湿地设计及排水水质预测提供了理论分析依据。     

Water Quality Monitoring Using Remote Sensing and an Artificial Neural Network

In remotely located watersheds or large waterbodies, monitoring water quality parameters is often not feasible because of high costs and site inaccessibility. A cost-effective remote sensing-based methodology was developed to predict water quality parameters over a large and logistically difficult area. Landsat spectral data were used as a proxy, and a neural network model was developed to quantify water quality parameters, namely chlorophyll-a, turbidity, and phosphorus before and after ecosystem restoration and during the wet and dry seasons. The results demonstrate that the developed neural network model provided an excellent relationship between the observed and simulated water quality parameters. These correlated for a specific region in the greater Florida Everglades at R ²?>?0.95 in 1998?C1999 and in 2009?C2010 (dry and wet seasons). Moreover, the root mean square error values for phosphorus, turbidity, and chlorophyll-a were below 0.03?mg?L^?1, 0.5 NTU, and 0.17?mg?m^?3, respectively, at the neural network training and validation phases. Using the developed methodology, the trends for temporal and spatial dynamics of the selected water quality parameters were investigated. In addition, the amounts of phosphorus and chlorophyll-a stored in the water column were calculated demonstrating the usefulness of this methodology to predict water quality parameters in complex ecosystems.     

黄河口新生湿地土壤氮磷分布特征研究

研究了黄河口新生湿地土壤中氮磷的分布特征,并进行了初步环境效应评价。结果表明,黄河口新生湿地土壤氮含量比较低,磷含量相对丰富;全氮分布水平变异系数较大,全磷变异系数较小;除裸滩外,土壤中氮含量垂直变异规律比较明显,土壤磷含量与土壤层次相关性普遍较差,只有滩涂碱蓬表现为异常。湿地土壤中氮磷含量均具有明显的季节动态特征。研究表明,黄河口新生湿地土壤中氮磷含量水平尚不会对近海环境产生富营养污染威胁。     

DETECTION AND DISCRIMINATION OF NUTRIENT DEFICIENCIES IN SUNFLOWER BY BLUE-GREEN AND CHLOROPHYLL-A FLUORESCENCE IMAGING

Fluorescence imaging was utilized to demonstrate the potential of blue-green fluorescence (BGF) and chlorophyll-a fluorescence (ChlF) to discriminate nitrogen (N), phosphorus (P), and potassium (K) deficiencies in sunflower plant showing similar growth inhibition. Only K-deficient leaves displayed significant increase of the BGF intensity. The epidermal UV-transmittance estimated by the ratio of ChlF intensities induced by UV and blue excitations (ChlF_UV/ChlF_BLUE) markedly decreased in both N- and P-deficient leaves but only in the latter that we observed significant decrease of the ratio of red and far-red ChlF intensities (RF/FRF) (that is inversely related to leaf chlorophyll concentration). The BGF increase in K-deficient was limited at leaf apex and margins and was spatially correlated to localized RF/FRF increases. Images analysis allows a better interpretation of the fluorescence changes by showing the spatial relationships between BGF, the ChlF_UV/ChlF_BLUE and the RF/FRF ratios that are indicative of physiological disturbances occurring in leaves of nutrient deficient plants.     

赣南红壤丘陵区137Cs示踪土壤侵蚀对土壤养分元素的影响

赣南红壤丘陵区是我国土壤侵蚀与土地退化比较严重的地区,以南丰县为例,应用137 Cs示踪技术探讨不同土地利用方式下土壤侵蚀与养分元素的关系。结果表明:(1)湿地松林、桔园、水田3种土地利用方式作用下土壤中137 Cs与养分元素分布差异显著,在垂直剖面上,湿地松林137 Cs含量呈指数递减分布,水田与桔园137 Cs含量因人为干扰在耕层内均匀分布;有机质与137 Cs有相似的分布特征;全氮、碱解氮、速效磷、速效钾含量均呈现一定表聚性。(2)位于坡地的2种土地利用方式中,湿地松林137 Cs、全氮、碱解氮、速效磷、速效钾、有机质含量均表现为下坡>上坡>中坡;桔园137 Cs活度表现为中坡>下坡>上坡,全氮、碱解氮、速效磷表现为下坡>中坡>上坡,而速效钾、有机质最大值均出现在上坡。(3)相关性分析表明,土壤137 Cs与有机质、全氮、碱解氮显著正相关,表明小流域有机质、氮元素可能与137 Cs有相同的物理运移方式,pH与137 Cs显著负相关,速效磷、速效钾则与137 Cs不相关。(4)3种土地利用方式中位于小流域谷地的水田137 Cs、有机质、全氮、碱解氮含量最高,坡地上桔园坡面137 Cs与土壤养分元素含量均高于湿地松林地,表明一定程度的坡改梯桔园种植模式能有效缓解土壤侵蚀与养分流失,改善区域生态环境。     

黄河口新生湿地土壤氮磷分布特征研究

研究了黄河口新生湿地土壤中氮磷的分布特征,并进行了初步环境效应评价。结果表明,黄河口新生湿地土壤氮含量比较低,磷含量相对丰富;全氮分布水平变异系数较大,全磷变异系数较小;除裸滩外,土壤中氮含量垂直变异规律比较明显,土壤磷含量与土壤层次相关性普遍较差,只有滩涂碱蓬表现为异常。湿地土壤中氮磷含量均具有明显的季节动态特征。研究表明,黄河口新生湿地土壤中氮磷含量水平尚不会对近海环境产生富营养污染威胁。     

Responses of nitrogen cycling and related microorganisms to brackish wetlands formed by evapotranspiration

Elevated evapotranspiration due to warmer air temperature could raise salinity and nutrient levels of some inland wetlands, potentially impacting nitrogen cycling. To characterize the impact of high evapotranspiration on soil microbial nitrogen cycling in inland wetlands, we compared freshwater and brackish marsh(or non-marsh) wetlands in terms of sediment ammonia-oxidizing rate(AOR), denitrifying rate(DR), and related microbial communities in a typical inland basin, the Hulun Lake basin, in Chi...     

Evaluation of the Ability of a Natural Wetland to Remove Heavy Metals Generated by Runways and Other Paved Areas from an Airport Complex in Brazil

In recent years, wetlands have received increasing attention in environmental engineering. Both natural and constructed wetland systems are now being used to treat a wide range of industrial, urban, and agricultural effluents. In the present study, we measured the heavy metal uptake of a wetland area in Brazil that receives runoff water from runways and paved areas. We analyzed the water, sediments, and emergent macrophytes and compared the data with the results of other studies of the retention of pollutants by wetlands. We also determined the heavy metal accumulation by the dominant macrophyte using transfer coefficients to determine metal transfer among sediments, roots, and leaves. We found that although the wetland removed significant amounts of pollutants from the airport??s drainage water through sedimentation, precipitation, and uptake by plants, additional work must be done to increase water retention times in the wetland to improve the wetland??s ability to immobilize pollutants.     

Nutrient Accumulation in Typha latifolia L. and Sediment of a Representative Integrated Constructed Wetland

This paper investigates the role of plants and sediment in removing nutrients from wastewater being treated in a representative integrated constructed wetland (ICW). It discusses the role of plants and sediment in removing nutrients from an ICW treating agricultural wastewater for more than 7 years. More nitrogen and phosphorus were stored in wetland soils and sediments than in plants. The first cell had the highest depth of sediment accumulation (45 cm). Over the 7-year operation period, the accretion rate was approximately 6.4 cm/year. With respect to maintenance, desludging of the first wetland cell of the ICW system appears to be necessary in 2011. An average of 10,000 m³ per year of wastewater entered the ICW. Approximately 74% (780 kg) of the phosphorus and 52% (5,175 kg) of the nitrogen that entered the wetland system was stored in the wetland soils and sediments. Plants stored a small fraction of nutrients compared to soils (<1% for both nitrogen and phosphorus). This study demonstrates that soils within a mature wetland system are an important and sustainable nutrient storage component.     

Contributions of ant mounds to soil carbon and nitrogen pools in a marsh wetland of Northeastern China

Ant mounds often occur at high densities in marsh wetlands. However, little information is available regarding their impacts on soil nutrient pools in these ecosystems. We studied C_org, dissolved organic carbon (DOC), total nitrogen (TN), NO₃⁻ and NH₄⁺ concentrations in above-ground ant mounds and in soils under mounds for three ant species (Lasius flavus, Lasius niger and Formica candida), and estimated their contribution to the total soil nutrient pools in a marsh wetland. Ant impacts were greatest in above-ground soils. All measured nutrient concentrations in above-ground mounds were significantly higher than the average values in reference soils (upper 25 cm). However, except for DOC, no significant differences for nutrient concentrations existed between soils under mounds and reference soils. The impacts of ant mounds on soil C and nutrient concentrations varied by ant species. L. niger above-ground mounds stored less C_org, TN and NO₃⁻ than F. candida and L. flavus mounds, or reference soils. At the ecosystem scale, soils in above-ground mounds and under ant mounds all contained less C_org per hectare than the reference soils. Total amounts in nutrient pools from mounds of the three ant species comprised from 5.3% to 7.6% of the total in natural marsh soils. More importantly, ant mounds increased the spatial heterogeneity of nutrient pools. Thus, ant mounds can be important to a fully integrated understanding of the structure and function of wetland nutrient cycles and balances.     

Nutrient flows and balances in intensively managed vegetable production of two West African cities

This study reports and analyzes nutrient balances in experimental vegetable production systems of the two West African cities of Tamale (Ghana) and Ouagadougou (Burkina Faso) over a two‐year period comprising thirteen and eleven crops, respectively. Nutrient‐use efficiency was also calculated. In Tamale and Ouagadougou, up to 2% (8 and 80 kg N ha^?1) of annually applied fertilizer nitrogen were leached. While biochar application or wastewater irrigation on fertilized plots did not influence N leaching in both cities, P and K leaching, as determined with ion‐absorbing resin cartridges, were reduced on biochar‐amended plots in Tamale. Annual nutrient balances amounted to +362 kg N ha^?1, +217 kg P ha^?1, and –125 kg K ha^?1 in Tamale, while Ouagadougou had balances of up to +692 kg N ha^?1, +166 kg P ha^?1, and –175 kg K ha^?1 y^?1. Under farmers' practice of fertilization, agronomic nutrient‐use efficiencies were generally higher in Tamale than in Ouagadougou, but declined in both cities during the last season. This was the result of the higher nutrient inputs in Ouagadougou compared to Tamale and relatively lower outputs. The high N and P surpluses and K deficits call for adjustments in local fertilization practices to enhance nutrient‐use efficiency and prevent risks of eutrophication.     

Effects of different green manure treatments on soil apparent N and P balance under a 34-year double-rice cropping system

Purpose

Although green manure rotation is often used to promote soil fertility and crop yield, the effects of this management practice on the nitrogen or phosphorus balance and the relationship between nutrient balance and the increase in soil nutrients have not been systematically studied.

Materials and methods

We investigated the apparent nitrogen and phosphorus balances and their associations with soil nitrogen and phosphorus increases, respectively, in a 34-year-old experimental site with various green manures and rice rotations using linear and logistic models. Cropping treatments included a rice-rice-winter fallow treatment as a control (RRW) and three green manure rotation treatments: rice-rice-ryegrass (RRR), rice-rice-oil rape (RRO), and rice-rice-Chinese milk vetch (RRC).

Results and discussion

We found that apparent nitrogen and phosphorus balances of RRR, RRO, and RRC were 164, 162, and 149 kg hm^?2, which were all significantly lower than 200 kg hm^?2 of RRW (P <?0.05). Moreover, the optimal fitted model of the relationship between cumulative nutrient balance and the increase in soil nutrients was different among treatments. Specifically, the correlation coefficients of cumulative nitrogen balance and soil nitrogen increase of RRR, RRO, and RRC in the linear model (0.49, 0.80, and 0.63) were all significantly lower than in the logistic model (0.81, 0.90, and 0.82). The correlation coefficients of cumulative phosphorus balance and increase in soil phosphorus of RRW in the linear model (0.81) were significantly lower than in the logistic model (0.91). Parameter analysis of the optimal fitted model revealed that RRC would increase the storage capacity of soil nitrogen and decrease the rate of soil phosphorus accumulation.

Conclusions

Our results suggested that long-term rice-rice-green manure rotation could significantly change the apparent nitrogen and phosphorus balance and their association with soil nitrogen and phosphorus content, respectively. Our study highlights the importance of green manure rotation in an agro-ecological environment and soil fertility in a double rice cropping system in red paddy soil.

     

几种挺水植物净化生活污水总氮和总磷效果的研究

研究了石菖蒲、灯心草和蝴蝶花3种不同植被系统、基质为河砂的潜流型人工湿地净化生活污水总氮和总磷的效果,并同无植被系统、相同基质的潜流型人工湿地净化效果进行了比较,结果表明:在较低浓度范围里无植被的人工湿地和3种有植被的人工湿地对污水中总氮有较好的去除作用,随着污水中总氮浓度的增加,虽然无植被的人工湿地和有植被的人工湿地去除总氮的效果均有下降的趋势,但有植被的人工湿地仍然能维持较高的总氮去除水平,无植被的人工湿地总氮去除效果则下降较快。在有植被的人工湿地中,以石菖蒲植被人工湿地氮素净化能力最强,其次为灯心草和蝴蝶花,这与植被自身吸收同化污水中氮素水平以及植物根系微生物作用有关。对于污水中总磷的去除,本研究中由于污水中磷素浓度较低,无植被和有植被的人工湿地对污水中磷素均有很好的去除作用,没有明显差异,但不同的植物体中磷素仍有明显的吸收同化富集现象,其中石菖蒲吸收同化磷素能力最强,其次为蝴蝶花和灯心草,植被在人工湿地系统中对于污水中总氮和总磷的去除起着重要的作用。     

Ecological stoichiometry of carbon, nitrogen, and phosphorus in estuarine wetland soils: influences of vegetation coverage, plant communities, geomorphology, and seawalls

Purpose

Little is known about carbon, nitrogen, and phosphorus stoichiometrical characteristics and influencing factors in estuary wetland soils. The purpose of this work is to study ecological stoichiometric characteristics of carbon, nitrogen, and phosphorus (R _CN, R _CP, and R _NP) in estuarine wetland soils of Shuangtaizi, northeast China and the potential affecting factors like vegetation coverage, plant communities, geomorphology, and seawall.

Materials and methods

During 2008–2010, soil samples in estuarine wetland were collected for soil organic carbon, total nitrogen and phosphorus, and other elements determination. Mole ratios of R _CN, R _CP, and R _NP were calculated.

Results and discussion

As a whole, R _CN was in the range of 8.26～52.97 (mean, 16.15), R _CP was in the range of 23.21～862.53 (mean, 90.66), and R _NP was in the 0.93～29.52 (mean, 5.07). R _CN, R _CP, and R _NP distribution were all with high spatial heterogeneities and significantly affected by vegetation coverage, plant communities, geomorphology, and seawalls. During the typical plant succession sequence of the halophytes–the mesophyte–the hydrophyte in estuarine wetland, P might be the primary limiting elements for nutrients stoichiometrical characteristics. R _CN, R _CP, and R _NP in soils of low-lying areas were all higher than that in highlands. Plant coverage and communities formation would help to reduce restriction from nitrogen, but to increase restrictions from phosphorus meanwhile.

Conclusions

C, N, and P ecological stoichiometry had high complexities. R _CN in estuarine wetland soils were generally high, whereas R _CP and R _NP were comparatively low, indicating that ecosystems in the estuary were limited by nutrients such as N and P, with the latter being the primary factor. Vegetation covers, plant communities, geomorphology, and seawall all affected nutrient stoichiometry in soils.