Effects of Land Use,Topography and Socio-Economic Factors on River Water Quality in a Mountainous Watershed with Intensive Agricultural Production in East China

Understanding the primary effects of anthropogenic activities and natural factors on river water quality is important in the study and efficient management of water resources. In this study, analysis of Variance (ANOVA), Principal component analysis (PCA), Pearson correlations, Multiple regression analysis (MRA) and Redundancy analysis (RDA) were applied as an integrated approach in a GIS environment to explore the temporal and spatial variations in river water quality and to estimate the influence of watershed land use, topography and socio-economic factors on river water quality based on 3 years of water quality monitoring data for the Cao-E River system. The statistical analysis revealed that TN, pH and temperature were generally higher in the rainy season, whereas BOD₅, DO and turbidity were higher in the dry season. Spatial variations in river water quality were related to numerous anthropogenic and natural factors. Urban land use was found to be the most important explanatory variable for BOD₅, COD_Mn, TN, DN, NH₄ ⁺-N, NO₃ ⁻-N, DO, pH and TP. The animal husbandry output per capita was an important predictor of TP and turbidity, and the gross domestic product per capita largely determined spatial variations in EC. The remaining unexplained variance was related to other factors, such as topography. Our results suggested that pollution control of animal waste discharge in rural settlements, agricultural runoff in cropland, industrial production pollution and domestic pollution in urban and industrial areas were important within the Cao-E River basin. Moreover, the percentage of the total overall river water quality variance explained by an individual variable and/or all environmental variables (according to RDA) can assist in quantitatively identifying the primary factors that control pollution at the watershed scale.     

滇池流域退耕区植物群落构建对地表径流污染物的削减效应

为探索不同群落的构建在滇池流域的实际应用,以确定削减污染物最优植物群落的配置方式,该研究选取地表径流悬浮物(SS)、COD含量、总氮(TN)、总磷(TP)、氨氮(NH_4~+-N)、硝氮(NO_3~--N)六个指标作为主要的分析对象,在滇池流域退耕区开展了不同植物群落配置对地表径流污染物削减效应的试验研究。结果表明:三个植物群落对SS、COD、TN、TP、NO_3~--N在2014年和2015年间均表现出显著性的削减趋势,且三个植物群落对SS、TP和NO_3~--N的削减率均在45%以上,但并未对NH_4~+-N表现出削减效果。不同植物群落对污染物的削减效应存在一定的差异性,但是三个不同群落与年度的交互作用对SS、COD、TN、TP、NO_3~--N五个养分指标的削减并没有表现出显著的差异性。从整体上来看,三种植物群落类型中,以乔-灌-草构建的立体式植物群落对地表径流污染物的削减效果最佳。     

洱海入湖河流弥苴河下游氮磷季节性变化特征及主要影响因素

入湖河流携带污染物对洱海水环境的影响日益明显,对洱海入湖水量最大的河流——弥苴河下游水体氮磷进行了连续采样分析,以期为河口湿地建设和水质改善提供基础数据.结果表明:1)弥苴河水质介于地表水Ⅲ-Ⅴ类之间,主要污染物为氮和磷,其中总氮平均浓度为1.17 mg/L,最高浓度达到2.00 mg/L;总磷平均浓度为0.06 mg/L;2)弥苴河下游总氮、总磷浓度丰水期高于枯水期,并呈现出季节性变化规律;3)弥苴河下游水体总氮、总磷年均浓度远高于洱海水体总氮、总磷年均浓度,其中总氮高出2.10倍,总磷高出2.90倍;4)弥苴河下游河段非点源污染占据主导地位.     

Nitrogen and Phosphorus Pollutants Removal from Rice Field Drainage with Ecological Agriculture Ditch: A Field Case

Excessive nitrogen and phosphorus in agricultural drainage can cause a series of water environmental problems such as eutrophication of water bodies and non-point source pollution. By monitoring the water purification effect of a paddy ditch wetland in Gaochun, Nanjing, Jiangsu Province, we investigated the spatial and temporal distribution patterns of N and P pollutants in paddy drains during the whole reproductive period of rice. Then, the dynamic changes of nitrogen and phosphorus in time and space during the two processes of rainfall after basal fertilization and topdressing were analyzed after comparison. At last, the effect of the ditch wetland on nutrient purification and treatment mechanism, along with changing flow and concentration in paddy drains, was clarified. The results of this study showed that the concentrations of various nitrogen and phosphorus in the ditch basically reached the peak on the second and third days after the rainfall (5.98 mg/L for TN and 0.21 mg/L for TP), which provided a response time for effective control of nitrogen and phosphorus loss. The drainage can be purified by the ecological ditch, about 89.61%, 89.03%, 89.61%, 98.14%, and 79.05% of TN, NH₄⁺-N, NO₃⁻-N, NO₂⁻-N, and TP decline. It is more effective than natural ditches for water purification with 80.59%, 40%, 12.07%, 91.06% and 18.42% removal rates, respectively. The results of the study can provide a theoretical basis for controlling agricultural non-point source pollution and improving the water environment of rivers and lakes scientifically.     

绿色屋面降雨径流水质及消减污染负荷研究

2011年5月至11月对12场降雨时段的屋面径流和干湿沉降进行采样监测,比较了屋面径流(绿色屋面和沥青屋面)、干湿总沉降和降雨中污染物的浓度和污染负荷,并运用多元统计方法分析了降雨特征对绿色屋面径流水质的影响。结果表明,从径流水质层面上分析,绿色屋面是总悬浮物(TSS)的汇,对p H值有较好的中和作用,对于总磷(TP)、溶解态铜(DCu)和溶解态锌(DZn)是非源非汇,是电导率(EC)、总氮(TN)、氨态氮(NH+4-N)、硝态氮(NO-3-N)、化学需氧量(COD)、5日生化需氧量(BOD5)和溶解态铅(DPb)的源;从污染负荷的角度分析,绿色屋面是NH+4-N、TSS和BOD5的汇,对于TN、DPb、DCu、DZn、TP和COD是非源非汇,是NO-3-N的源;与控制屋面相比,绿色屋面可以消减TSS、TP、BOD5、COD、NH+4-N、DZn和DPb的污染负荷,分别消减了90.53%、49.38%、41.31%、36.48%、35.45%、28.27%和14.20%;但是增加了NO-3-N和TN的污染负荷,分别增加了821.02%和275.48%;绿色屋面径流污染物的浓度与降雨量、降雨历时和降雨强度呈负相关关系,而与降雨间隔呈正相关关系。研究结果为绿色屋面的科学设计及正确评价绿色屋面对径流水质的影响提供依据。     

Impact of Yangtze River Water Transfer on the Water Quality of the Lixia River Watershed,China

To improve water quality and reduce the negative impacts of sudden inputs of water pollution in the Lixia River watershed, China, a series of experimental water transfers from the Yangtze River to the Lixia River were conducted from 2 December 2006 to 7 January 2007. Water samples were collected every six days at 55 monitoring sites during this period. Eight water parameters (water temperature, pH, dissolved oxygen (DO), chemical oxygen demand (COD), potassium permanganate index (COD_Mn), ammonia nitrogen (NH₄ ⁺-N), electrical conductivity (EC), and water transparency (WT)) were analyzed to determine changes in nutrient concentrations during water transfers. The comprehensive pollution index (Pi) and single-factor (Si) evaluation methods were applied to evaluate spatio-temporal patterns of water quality during water transfers. Water quality parameters displayed different spatial and temporal distribution patterns within the watershed. Water quality was improved significantly by the water transfers, especially for sites closer to water intake points. The degree of improvement is positively related to rates of transfer inflow and drainage outflow. The effects differed for different water quality parameters at each site and at different water transfer times. There were notable decreases in NH₄ ⁺-N, DO, COD, and COD_Mn across the entire watershed. However, positive effects on EC and pH were not observed. It is concluded that freshwater transfers from the Yangtze River can be used as an emergency measure to flush pollutants from the Lixia River watershed. Improved understanding of the effects of water transfers on water quality can help the development and implementation of effective strategies to improve water quality within this watershed.     

Study on ecological protection and rehabilitation technology of a reservoir-type water source in the northeastern region of China

ABSTRACT

Surface water is the main source of water for human life and production. The quality of water affects living conditions and the overall health of people. Ecological protection and restoration engineering technology, combining ecological revetment and an ecological floating bed, is applied to a selected shallow beach experimentation area of a reservoir water source area in Northeast China. According to local conditions, the ecological revetment plants were identified as Goosegrass, sedges, and water grasses, and other local species of Polygonum hydropiper bagen, reeds, and bulrushes were identified as ecological floating bed plants. Regular monitoring of water quality in the experimentation area and a control area showed that the ecological protection and restoration technology can effectively reduce the concentrations of BOD₅ (five day biochemical oxygen demand), COD (chemical oxygen demand), TN, NH₃-N, NO₃^?-N, TP, TDP, Mn, Zn, Fe, Pb, total coliforms, and other indicators of surface water in the experimentation area. The BOD₅, COD, Max TN, NH₃-N, NO₃^?-N, TP, and TDP reduction rates were 84.76%, 57.14%, 86.76%, 83.78%, 89.26%, 94.02%, and 95.89%, respectively, with the implementation of water pollution prevention and the purifying shoal.     

原位生物技术对城市重污染河道底泥的治理效果

以扬州市典型城市内河河道为例研究了人工曝气、生态砖覆盖、生物填料覆盖、低位植物浮床(简称低位浮床)等原位生态处理技术对河道底泥污染释放及其对上覆水污染负荷贡献的治理效果.研究结果表明:经不同原位生态处理后,1)底泥中氨氮的释放速率下降50.3％-89.64％,平均为59.27％;底泥污染释放对上覆水氨氮负荷贡献量的去除率为36.59％-82.67％,平均为53.33％;2)底泥中总氮的释放速率下降20.96％-88.94％,平均为42.32％;底泥总氮释放对上覆水污染负荷贡献量的污染去除率为38.00％-67.06％,平均为54.96％;3)底泥中总磷的释放速率下降27.49％-91.00％,平均为55.31％;底泥总磷释放对上覆水总磷污染负荷贡献量的去除率为67.14％-98.46％,平均为84.33％;4)底泥中CODMn的释放速率下降11.84％-79.32％,平均为41.16％;底泥上覆水中CODMn的释放速率下降-1.25％--70.74％,平均为29.83％.研究还发现,原位生态处理技术在运行中对底泥污染治理的效果受该技术对底泥的扰动程度的影响,在进行集成应用的时候,对底泥扰动较大的技术应与对底泥扰动较小的技术相间应用,以减少工程技术运行中对底泥扰动造成的污染爆发式释放,达到更好的整体处理效果.     

Effect of a modular extensive green roof on stormwater runoff and water quality

Runoff quantity and quality from a 248 m² extensive green roof and a control were compared in Connecticut using a paired watershed study. Weekly and individual rain storm samples of runoff and precipitation were analyzed for TKN, NO₃ + NO₂-N, NH₃-N, TP, PO₄-P, and total and dissolved Cu, Pb, Zn, Cd, Cr, and Hg. The green roof watershed retained 51.4% of precipitation during the study period based on area extrapolation. Overall, the green roof retained 34% more precipitation than predicted by the paired watershed calibration equation. TP and PO₄-P mean concentrations in green roof runoff were higher than in precipitation but lower than in runoff from the control. The green roof was a sink for NH₃-N, Zn, and Pb, but not for TP, PO₄-P, and total Cu. It also reduced the mass export of TN, TKN, NO₃ + NO₂-N, Hg, and dissolved Cu primarily through a reduction in stormwater runoff. Greater than 90% of the total Cu, Hg, and Zn concentrations in the green roof runoff were in the dissolved form. The growing media and slow release fertilizer were probable sources of P and Cu in green roof runoff. Overall, the green roof was effective in reducing stormwater runoff and overall pollutant loading for most water quality contaminants.     

广东省水质现状及驱动因素

水质现状评估及其驱动因素分析是实现水生态保护、水资源利用和水污染治理的关键,对于水生态系统的可持续发展具有重要意义。以广东省七大流域为研究区,基于2019-2020年间的溶解氧（DO）、透明度（SDD）、悬浮物（SPM）、叶绿素a （Chla）、氨氮（NH₃N）、总氮（TN）、总磷（TP）7个指标的水质监测数据,综合运用单因子指数法（SI）和综合水质指数（WQI）评价方法,分丰水期（N=66）和枯水期（N=54）评估研究区的水质现状,并探讨水质参数与地形、气象、社会经济和土地覆被类型等驱动因素之间的相关关系。SI评估结果显示广东七大流域主要以工业污水、农业面源等造成的Chla和TN浓度超标、部分水体富营养化严重为主,同时伴有溶解氧浓度偏低的问题;WQI评估结果显示研究区有57%以上的采样点属于中等以下水质。Chla、SPM、NH₃N和TP浓度具有显著的季节和驱动因素差异：丰水期的Chla和TP浓度低于枯水期,但SPM和NH₃N浓度高于枯水期。枯水期DO、TN和WQI的显著性影响因子为丰水期的1/3左右;这种季节差异可能是流域内降雨、营养盐负荷和土地覆被类型导致的复杂地表径流及面源污染所致。珠江三角洲河网区、粤西诸河、韩江下游以及粤东诸河练江流域的水质问题突出。未来水生态系统的可持续发展研究可以借助长时间序列、多频次、高分辨率的遥感监测手段和多种数值模拟方法以及常规水质评估模型,探讨气候变化、河岸带产业结构和流域土地利用方式对面源污染的影响,以进一步厘清降雨强度、三产结构和土地利用方式转变对区域水质变化的影响。     

青弋江流域土地利用/景观格局对水质的影响

研究不同空间尺度的景观组成与结构对水质的影响对于水质保护具有重要意义。青弋江为长江下游最长的支流,人类活动可能通过多种方式对水质产生影响。以青弋江流域为研究对象,基于Google Earth遥感数据和水质实测数据,采用冗余分析（RDA）和Spearman相关性分析,探讨了土地利用/景观格局对水质的影响。研究结论为：（1）以采样点为中心建立的100、200、500、1000、2000 m 5种尺度缓冲区中,500 m半径圆形缓冲区景观组成对水质的解释率最高,枯水期与丰水期对水质的解释率分别为46.30%和43.10%。（2）土地利用类型中,耕地和建设用地面积与NH₄⁺-N、TP、EC呈正相关,对水质具有负面效应;林地面积与DO呈正相关,对污染物起到净化作用;土地利用综合程度指数与污染指标呈正相关,表明人类活动强的区域,水质变差。（3）景观格局指数中,PRD在丰水期与NH₄⁺-N、TP浓度为负相关,相关系数分别为-0.656、-0.540,表明随斑块丰富度密度的增大,流域生态系统更加稳定;LPI与DO浓度在枯水期为显著负向相关,相关系数为-0.653,SHAPE_AM与NH₄⁺-N、TP呈显著正向相关,表明随人类活动强度的增大,水质恶化;FRAC_AM与水质的关系无法得到合理的解释。通过多角度分析,在一定程度揭示了青弋江流域的生态水文过程,有利于土地利用管理和水质保护,进而促进资源的可持续利用。研究结果可为政府相关职能部门进行决策时提供参考。     

城镇化流域“源-汇”景观格局对河流氮磷空间分异的影响——以天津于桥水库流域为例

随着流域城镇化的加速,流域城镇化景观格局对流域水质的影响逐渐加剧。以城镇化趋势明显的于桥水库流域为例,基于流域"源-汇"景观特征指数,并结合于桥水库流域2013、2014和2015年33个子流域的水质数据,采用空间分析、相关分析和冗余分析等方法,探讨了在城镇化影响下,于桥水库流域景观特征指数和水质指标的定量关系。结果表明:整个流域从上游到下游呈现"汇"景观面积减小,"源"景观面积增大的趋势,居民建设用地面积比在中下游子流域达34.6%,"汇"型景观中林地面积为33.5%;景观空间负荷对比指数(LWLI)全局Moran′s I的值为0.637,P0.01,在空间上存在趋于集群的现象,LWLI高-高聚集区与城镇化集中区域具有一致性。LWLI与流域氮、磷空间分布存在极显著的相关性,平水期TN与LWLI的复相关系数R_2为0.811,丰水期LWLI与TP的复相关系数R_2为0.741;子流域所有水质参数NH_4~+-N、TN、NO_3~--N、TP及LWLI均集中在同一象限,与其它景观特征指数相比,LWLI对河流中氮、磷的影响最大。城镇居民用地与水质指标存在极显著的相关性,是流域水质污染重要的贡献源。流域城镇化发展中,建议提高村镇的景观连通性,便于污染物集中处理,同时增加林地、草地面积,改善流域的生态水文功能。     

Land use disturbance indicators and water quality variability in the Biscayne Bay Watershed,Florida

Rapid land use transformations due to extensive agricultural and urban development in south Florida (USA) threaten water resources such as Biscayne Bay, an oligotrophic estuary draining the Miami metropolitan complex and South Dade Agricultural Area. Biscayne Bay is sensitive to nutrient inputs and this study evaluated watershed land use-water quality relationships from 1995 to 2004. Using eight monitoring sites, three spatial extents were considered: sub-basins, canal buffers, and site buffers. Selected sites represented agricultural, urban, and mixed land use classes. Disturbance indicators (landscape metrics; Landscape Development Intensity (LDI) index; percent imperviousness), nutrient loads (nitrate/nitrite-nitrogen (NO_X-N); total ammonia nitrogen (NH₃-N); total phosphorus (TP)), and multivariate regression models were used to determine land use factors influencing water quality variability. The sub-basin regression model was the best predictor of annual NO_X-N loads in the watershed. Both LDI and largest patch index variables were included in this model, indicating that the relative distribution of dominant land use classes influences NO_X-N loads. There were no significant regression models for total inorganic nitrogen (NO_X-N plus NH₃-N) loads. Total phosphorus loads were more closely related to disturbance indicators at a smaller spatial extent (1000 m canal buffer), which is a function of watershed nutrient transport processes. The relative proportion of directly connected impervious areas (DCIA) was not identified as a significant land use variable for regression models. Positive correlations between LDI and DCIA values suggested both indicators provided similar information regarding the intensity of human disturbance. However, the LDI index incorporates anthropogenic intensity associated with a broad range of land uses while DCIA primarily reflects the impact of watershed urbanization. Watershed managers can use the LDI index with landscape metrics that evaluate spatial patterns to link land use development to water quality parameters.     

Seasonal Variations and Aeration Effects on Water Quality Improvements and Physiological Responses of Nymphaea Tetragona Georgi

Seasonal variations and aeration effects on water quality improvements and the physiological responses of Nymphaea tetragona Georgi were investigated with mesocosm experiments. Plants were hydroponically cultivated in six purifying tanks (aerated, non-aerated) and the characteristics of the plants were measured. Water quality improvements in purifying tanks were evaluated by comparing to the control tanks. The results showed that continuous aeration affected the plant morphology and physiology. The lengths of the roots, petioles and leaf limbs in aeration conditions were shorter than in non-aeration conditions. Chlorophyll and soluble protein contents of the leaf limbs in aerated tanks decreased, while peroxidase and catalase activities of roots tissues increased. In spring and summer, effects of aeration on the plants were less than in autumn. Total nitrogen (TN) and ammonia nitrogen (NH₄ ⁺-N) in aerated tanks were lower than in non-aerated tanks, while total phosphorus (TP) and dissolved phosphorus (DP) increased in spring and summer. In autumn, effects of aeration on the plants became more significant. TN, NH₄ ⁺-N, TP and DP became higher in aerated tanks than in non-aerated tanks in autumn. This work provided evidences for regulating aeration techniques based on seasonal variations of the plant physiology in restoring polluted stagnant water.     

Concentration of nutrients in selected lakes in the High Tatra Mountains, Slovakia: effect of season and watershed

Concentrations of total phosphorus (TP), inorganic and organic nitrogen, organic matter, and chlorophyll-a were studied in ten mountain lakes at various stages of acidification, trophy, and type of watershed during each July and October from 1987 to 1990. Concentrations of TP and total organic matter were higher in July than in October. Concentrations of NH4₄ ⁺-N decreased and NO₃ ^–-N increased from July to October. The relative composition of total nitrogen (TN) and its concentration were strongly dependent on the type of watershed: the lowest TN concentrations were observed in lakes with forested watersheds, increasing above the timberline and reaching maximum values in acidified lakes with rocky watersheds. In the pool of TN, nitrate was most important in lakes above the timberline (70–86% of TN), and organic nitrogen in forest lakes (> 90% of TN). Lakes with rocky watersheds were characterized by high ratios of TN:TP (> 250 by mass). The concentration of chlorophyll-a varied widely, from 0.01 to 22.6 µg l^–1, without any consistent change between July and October, and were P limited.     

Estimation of nitrogen dynamics in a vertical-flow constructed wetland

The vertical-flow constructed wetland (VFCW) is a promising engineering technique for removal of excess nutrients and certain pollutants from wastewater and stormwater. The aim of this study was to develop a model using the STELLA software for estimating nitrogen (N) dynamics in an artificial VFCW (i.e., a substrate column with six zones) associated with a growing Cyperus alternifolius species under a wetting (wastewater) -to-drying ratio of 1:3. The model was calibrated by our experimental data with a reasonable agreement prior to its applications. Simulations showed that rates of NH₄⁺-N and NO₃⁻-N leaching decreased with increasing zone number (or column depth), although such a decrease was much more profound for NH₄⁺-N. Our simulations further revealed that rate of NH₄⁺-N leaching decreased with time within each zone, whereas rate of NO₃⁻-N leaching increased with time within each zone. Additionally, both the rates of NH₄⁺-N and NO₃⁻-N leaching through zones followed the water flow pattern: breakthrough during wetting period and cessation during drying period. In general, the cumulative amounts of total nitrogen (TN) were in the following order: leaching > denitrification > uptake > settlement. About 54% of the TN from the wastewater flowed out of the VFCW system, 18% of TN lost due to denitrification, 6% of TN was taken up by roots of a single plant (one hill), and the rest of 22% TN from the wastewater was removed from other mechanisms, such as volatilization, adsorption, and deposition. This study suggested that to improve the overall performance of a VFCW for N removal, prevention of N leaching loss was one of the major issues.     

赣江流域土地利用方式对河流水质的影响

赣江是鄱阳湖的最大支流,是鄱阳湖水污染物的主要来源,查明流域土地利用方式对赣江水质的影响和鄱阳湖的水环境保护具有重要意义。基于2012年对赣江7个主要支流NH+4-N、TP、CODMn和DO浓度的每月测定结果,通过不同空间尺度和土地类型等级划分,利用相关分析和冗余分析研究土地利用方式对赣江流域河流水质的影响。研究结果表明,子流域的土地利用方式对TP的影响大于缓冲区;对CODMn的影响在丰水期大于缓冲区,在枯水期小于缓冲区;对NH+4-N的影响在丰水期与缓冲区接近,在枯水期小于缓冲区;DO受土地利用方式的影响较小。水田中的丘陵水田是赣江水体TP和丰水期CODMn的主要来源;平原水田是枯水期CODMn的主要来源。居民建设用地中的城镇用地是赣江水体TP、NH+4-N和丰水期CODMn的主要来源,农村用地是CODMn的主要来源。水域中的水库坑塘是赣江水体TP和丰水期NH+4-N、CODMn的主要来源。     

Performance of an ecological treatment system at three strengths of dairy wastewater loading

Ecological treatment systems, which rely on renewable resources, have successfully treated municipal and industrial effluents with reduced costs compared to conventional methods, but their capacity to treat dairy wastewater is unknown. In order for ecological treatment systems to be practical for agriculture they must be able to treat a significant portion of a dairy's daily wastewater production. In this study, the impact of three strengths of dairy wastewater on effluent water quality was assessed. Three ratios of wastewater and city water—(1) one part wastewater:three parts city water, (2) one part wastewater:one part city water, and (3) two parts wastewater:one part city water—were each pumped into an ecological treatment system. Influent and effluent water samples were analyzed for PO₄-P, TP, TN, NH₄-N, NO₃-N, total suspended solids (TSS), and carbonaceous biochemical oxygen demand (CBOD₅). Influent dairy wastewater volumetric loading rates were much greater than those of municipal wastewater. Regardless of influent wastewater strength, concentrations of all measured variables were significantly reduced between the influent and effluent of the ecological treatment system. At the lowest wastewater strength, PO₄-P was reduced 39%, TN 83%, and NH₄-N 89%, while at the highest wastewater strength, PO₄-P was reduced 41%, TN 79%, and NH₄-N 70%. Increased wastewater strength required greater aerobic treatment volume to reduce concentrations of NH₄-N and CBOD₅.     

不同氮处理下速生柳对水体氮的吸收、分配及生理响应

采用水培法,研究了旱柳苗在外源添加不同氮水平(贫氮、中氮、富氮、过氮)的铵态氮(NH+4-N)和硝态氮(NO-3-N)的生长、氮吸收、分配和生理响应。结果表明:一定范围氮浓度的增加能够促进旱柳苗的生长,但过量氮会抑制其生长,且NH+4-N的抑制作用大于NO-3-N;两种氮处理下,旱柳表现出对NH+4-N的吸收偏好,在同一氮水平时,旱柳各部位氮原子百分含量Atom%15N(AT%)、15N吸收量和来自氮源的N%(Ndff%)均为NH+4-N处理大于NO-3-N处理,且随着氮浓度的增加,差异增大,且在旱柳各部位的分布为根﹥茎﹥叶;2种氮素过量和不足均会对旱柳根和叶生理指标产生不同的影响,其中在过氮水平时,NH+4-N和NO-3-N处理下根系活力比对照减少了50.61%和增加了19.53%;在过氮水平时,NH+4-N处理柳树苗根总长、根表面积、根平均直径、根体积和侧根数分别对照下降了30.92%、29.48%、19.44%、27.01%和36.41%,NO-3-N处理柳树苗相应的根系形态指标分别对对照下降了1.66%、5.65%、1.49%、5.06%和25.72%。可见,高浓度NH+4-N对旱柳苗的胁迫影响大于NO-3-N,在应用于水体氮污染修复时可通过改变水体无机氮的比例,削弱其对旱柳的影响,从而提高旱柳对水体氮污染的修复效果。     

菹草种群内外水质日变化

对菹草(Potamogeton crispus)种群内外水体进行了昼夜连续监测,分析菹草种群内外水质的日变化趋势.结果显示,种群内DO自日出后增加,日落后持续下降,且与水温变化一致,于19:30左右出现1次明显低谷,后略有恢复,后一直降至日出前后;开阔水域DO变化与水温呈现一定相关性,但变化幅度较小;交界处DO含量兼有种群内与开阔水域的变化特点.种群内水体pH值自日出前后升高,日落时达最高值,后开始下降,直至次日出前后;交界处与种群变化趋势一致;开阔水域pH总体变化幅度较小,白天高于夜间,总体DO含量及pH分布:种群区＞交界处＞开阔水域.种群及交界处TN含量均在日出前后达最高,日出后递减,开阔水域夜间含量较高,日出前后达最高;各点NH+4-N变化规律不显著;种群内水体TP含量夜间较高,日出前后达最高值,日出后递减,日落后递增;开阔水域TP含量夜间较高,白天略低;交界处正午前后达最低值,傍晚达最高值,TN、TP总体分布:种群＜交界处＜开阔水域.菹草种群存在对水体DO、pH等环境因子均产生重要影响,继而影响水体内源性氮磷的迁移,其中对pH影响较小,其变化未能影响水体氮磷迁移,而DO昼夜变化较大,对水体内源性氮磷的迁移起重要影响.