城市景观组分影响水质退化的阈值研究

运用景观格局与水质监测方法评价城市景观变化对河流水质的影响,是当前景观格局-效应研究的热点问题.为实现城市发展目标与水环境保护目标的统一,需要科学判断城市景观变化对水质的影响程度与范围,特别是以城市不透水表面为代表的景观组分变化,是目前水质退化研究中的核心对象,而对水质退化的景观阈值研究目前尚存争论.基于截面数据进行统计分析,构建阈值判定方法,选择深圳市为案例研究区,研究快速城市化地区的河流水质退化的景观阈值水平.结果表明,在深圳市,河流缓冲区宽度为100-200 m时,景观变化对水质显著性影响最高(P＜0.001).缓冲区内,景观变化与耗氧、营养盐等类指标呈指数关系,具有显著性,是这类指标变化的最主要影响因素;同时,景观变化与有毒物质及重金属等类指标呈指数关系,具有显著性,但并非这类指标变化的最主要因素.影响水质退化的不透水表面比例阈值水平介于38.2％-50％之间,最小阈值水平为38.2％,即当流域缓冲区内不透水表面百分比超过38.2％时,河流水质显著退化.     

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。     

基于灰水足迹的中国城市水资源可持续利用综合评价

随着城市化的快速发展,中国城市水资源面临着水资源短缺与水环境恶化等挑战,因此加强城市水资源可持续利用对于中国可持续发展具有重要意义。基于灰水足迹核算对2016年中国地级市水资源可持续利用情况进行综合评价。研究结果表明：（1）中国城市灰水足迹水平差异大,平均值为23.40×10⁸ m³,主要集中在20.00×10⁸ m³以下。中国城市农业源灰水足迹比例占比主要在70%以上,工业源比例占比主要在20%以下,而生活源比例占比在40%以下;（2）全国灰水经济生产率在12.45-857.31元/m³范围内,地区差异明显。33%城市灰水足迹荷载系数均大于1,全国地级市灰水足迹荷载系数平均值为1.16,城市水资源利用已对水环境产生污染压力,用水不可持续;（3）城市水资源开发率与灰水足迹荷载系数呈一定程度的正相关关系,说明了城市发展对水资源利用的"量"和"质"的压力作用具有一定的协同关系;（4）水资源可持续利用程度呈现大型城市 > 特大型城市 > 超大型城市 > 中小型城市,城市发展一定程度上有助于水资源的可持续利用,但发展规模过大可能会造成用水高产而护水低效的现象。因地制宜的实行水资源循环经济发展模式以及适时纳入灰水足迹核算与管理体系,是当前城市化大背景下实现水资源可持续利用的重要途径。     

Application of modified water quality indices as indicators to assess the spatial and temporal trends of water quality in the Dongjiang River

The Dongjiang River plays an important role in southern China, as a source for irrigation and potable water of Hongkong and the other parts of the Pearl River Delta (PRD). The water quality index (WQI) was calculated to assess the spatial and temporal variability and identify the classification of water quality in the river. In order to simplify the procedure and reduce the analytical costs of the water quality evaluation, a modified WQI (defined as WQI_min) was introduced based on Principal Component Analysis (PCA) and correlations analyses of the water parameters detected in dry and wet seasons during 2011–2012. Compared with the previous index, similar spatial changing trend and classification of the water quality were obtained by WQI_min, which was composed of pH, temperature, total suspended solid, NH₄⁺-N, and NO₃⁻-N. The results showed an excellent water quality in the tributary site near the reservoir, a good water quality in the upstream of the river, and medium water quality in the downstream of the river, which suggested that the urban wastewater originated from increasing population size and industry development in the downstream mainly led to the deterioration of water quality along the river. Moreover, WQI_min could more adequately reflect the seasonal changes of water quality which was slightly worse in dry season than wet season. Our results also suggest that continuous monitoring should be conducted to prevent pollution from industry and anthropogenic activities.     

浙江饮用水源地浮游动物群落特征及环境响应

2010年1月至2011年10月,对浙江省16个饮用水源地(H1—H8为河网型,K1—K8为水库型)的浮游动物群落进行季节调查。共记录浮游动物优势种(属)21种(轮虫8种、枝角类5种、剑水蚤5种和哲水蚤3种),各类群第一优势种分别为针簇多肢轮虫(Polyarthra trigla)、长额象鼻溞(Bosmina longirostris)、粗壮温剑水蚤(Thermocyclops dybowskii)和汤匙华哲水蚤(Sinocalanus dorrii)。2年间,河网和水库浮游动物平均密度分别为345.2 L-1和199.4 L-1,生物量分别为0.667 mg/L和0.421mg/L。各类群密度百分比例均以轮虫和桡足类无节幼体为主,甲壳动物以剑水蚤为主。经逐步回归分析表明,浮游动物群落密度(生物量)与河网水质因子(P0.01)之间相关性比水库(P0.05)更密切,总磷和氨氮分别入选了河网和水库所有有效的回归方程中。通径分析和决策系统分析表明,河网的总磷和叶绿素a含量对浮游动物群落变动具有正效应,溶解氧具有负效应;总磷含量是影响河网群落变动的最重要因子,叶绿素a含量则是影响群落增长最主要的限制因子。河网剑水蚤、无节幼体和轮虫群落的密度(生物量)与水体综合营养指数TLIc密度(TLIc生物量)之间有显著的线性回归关系(P0.001),无节幼体密度构成了TLIc密度变动的限制因子,轮虫生物量成为TLIc生物量变动的限制因子,而剑水蚤是一类最重要、稳定的水质指示群落,这对于筛选浮游动物群落的一些拓展性监测指标具有重要的参考作用。     

北京市妫水河浮游动物群落结构与水质评价

由于浮游动物对水体环境变化敏感,可表征水体污染程度,因此在2017年对妫水河浮游动物群落结构进行调查研究,分析了浮游动物群落结构时空变化特征及其与环境因子的关系,并利用生物学评价方法对水质进行评价。结果表明:妫水河浮游动物有4门22属88种,其中原生动物种类最多,为42种,主要以轮虫和原生动物为主,浮游动物平均细胞密度和生物量分别为5041.58个/L和2.88 mg/L。浮游动物群落结构与环境因子的CCA分析显示,水温、pH、DO和氨氮是影响妫水河浮游动物群落结构变化的重要因素,其中裂痕龟纹轮虫、冠饰异尾轮虫和螺形龟甲轮虫等对水体中氮磷的相关性极为显著,具有富营养化指示作用,可作为监测水质的指示生物。妫水河浮游动物多样性指数H、均匀度指数J和丰富度指数D全年平均值分别为0.43、0.31和0.41,整体评价结果显示,妫水河水体处于中到富营养型水平,尤其是下段城区段污染严重,表明妫水河水体生态功能遭到破坏,水质还需进一步改善和治理。本研究结果可为妫水河水质评价、水环境监测及水污染治理提供基础数据资料和理论依据。     

Soil water availability for plants as quantified by conventional available water, least limiting water range and integral water capacity

There are different approaches to define the soil available water (SAW) for plants. The objectives of this study are to evaluate the SAW values of 12 arable soils from Hamadan province (western Iran) calculated by plant available water (PAW), least limiting water range (LLWR) and integral water capacity (IWC) approaches and to explore their relations with Dexter’s index of soil physical quality (i.e., S-value). Soil water retention and mechanical resistance were determined on the intact samples which were taken from the 5–10 cm layer. For calculation of LLWR and IWC, the van Genuchten-Mualem model was fitted to the observed soil water retention data. Two matric suctions (h) of 100 and 330 cm were used for the field capacity (FC). There were significant differences (P?<?0.01) between the SAW values calculated by PAW₁₀₀, PAW₃₃₀, LLWR₁₀₀, LLWR₃₃₀ and IWC. The highest (i.e., 0.210 cm³ cm^?3) and the lowest (i.e., 0.129 cm³ cm^?3) means of SAW were calculated for the IWC and LLWR₃₃₀, respectively. The upper limit of LLWR₃₃₀ for all of the soils was h of 330 cm, and that of LLWR₁₀₀ (except for one soil that was air-filled porosity of 0.1 cm³ cm^?3) was h of 100 cm. The lower limit of LLWR₃₃₀ and LLWR₁₀₀ for five soils was h of 15,000 cm and for seven soils was mechanical resistance of 2 MPa. The IWC values were smaller than those of LLWR₁₀₀ for two soils, equal to those of LLWR₁₀₀ for three soils and greater than those of LLWR₁₀₀ for the rest. There is, therefore, a tendency to predict more SAW using the IWC approach than with the LLWR approach. This is due to the chosen critical soil limits and gradual changes of soil limitations vs. water content in the IWC calculation procedure. Significant relationships of SAW with bulk density or relative bulk density were found but not with the clay and organic matter contents. Linear relations between IWC and LLWR₁₀₀ or LLWR₃₃₀ were found as: IWC?=??0.0514 + 1.4438LLWR₁₀₀, R ²?=?0.83; and IWC?=??0.0405 + 2.0465LLWR₃₃₀, R ²?=?0.84, respectively (both significant at P?<?0.01). Significant relationships were obtained between the SAW values and S indicating the suitability of the index S to explain the availability of soil water for plants even when complicated approaches like IWC are considered. Overall, the results demonstrate the importance of the choice of the approach to be used and its critical limits in the estimation of the soil available water to plants.     

Relationship between river water quality and land use in a small river basin running through the urbanizing area of Central Japan

In this study, the relationship between water quality (as represented by major inorganic ion concentrations) and land use characteristics is examined for a small river basin which runs through the urbanizing area of central Japan. Water samples were taken from 24 sites at base flow and analyzed, and the proportions of the various land uses associated with the respective drainage basins were calculated using a digital land-use map (scale: 1:25000). The electrical conductivity (EC) of the water ranged from 84.5 to 600 μS cm⁻¹. Ca²⁺ and Na⁺ were the major cations, accounting for 77% of all cations. Among the anions, HCO₃ ⁻ was dominant (56%), followed by Cl⁻ (24%), SO₄ ²⁻ (13%) and NO₃ ⁻ (7%). Applying principal component analysis to land use in the drainage basin yielded three principal components. The first principal component expressed the degree of occupation by residential areas, the second indicated the degree of urban developing area (i.e., fast-developing and industrial areas), and the third showed the degree of coverage with farmland and green space. The residential area showed significant positive correlations with K⁺, Mg²⁺, Ca²⁺, NO₃ ⁻, HCO₃ ⁻, EC and TMI (total major ions). Urban developing area showed significant positive correlations with Ca²⁺, Cl⁻, HCO₃ ⁻, EC and TMI as well as weak negative correlations with NO₃ ⁻ and SO₄ ²⁻. Industrial area showed weak positive correlations with Na⁺ and Cl⁻ and a moderate negative correlation with NO₃ ⁻. Farmland showed significant positive correlations with NO₃ ⁻ and SO₄ ²⁻; these ions are present due to fertilizers and the biological activity of plants. Forest area is inversely related to almost all ions, indicating the need for this form of land use in order to maintain river water quality.     

桂江流域附生硅藻群落特征及影响因素

研究了桂江流域水质、土地利用、地理因素对河流附生硅藻群落的影响。结果显示,桂江流域电导率(Conductivity,Cond.)由下游至源头呈降低趋势,其它水质参数变化趋势不明显。主成分分析(Principle Component Analysis,PCA)显示前两个主成分共解释了56.2%的水质特征,第一轴反映了氨氮(NH4-N)、硝氮(NO3-N)、总氮(Total Nitrogen,TN)的变化梯度,第二轴反映了水温(WT)、pH、Cond.、溶解氧(Dissolve Oxygen,DO)的变化梯度。桂江流域硅藻特定污染敏感指数(Specific PolluoSensitivity Index,IPS)和硅藻生物指数(Biological Diatom Index,IBD)下游低于源头,差异不显著,与多项水质、土地利用以及地理因子呈线性显著相关。24个样地共发现112种硅藻,丰富度大于5%的37种,丰富度最大的几个种类依次为Achnanthidium minutissimum,A.pusilla,A.tropica,Cymbella laevis。对应分析(Corresponding Analysis,CA)显示桂江流域存在3个差异较大的硅藻群落,流域下游以Nitzschia recta为优势种,A.lanceolata、Amphora montan、Planothidium frequentissimum在中下游丰度较高,上游区域种类较多。典型相关分析(Canonical Correspondence Analysis,CCA)排序前两轴解释了硅藻群落变异程度的28.60%,CCA排序轴1与水质(Cond.、WT、NH4-N、NO3-N、TN)和土地利用(城市面积、农田面积、植被覆盖)显著负相关,与地理因素(流域面积、海拔、坡度)显著正相关,第二轴与浊度(NTU)显著正相关(P<0.05)。偏典型相关分析(Partial CCAAnalyses)显示,土地利用、地理因子、水质分别解释了桂江流域硅藻群落变异的7.20%,17.50%,48.50%。结果表明,桂江流域附生硅藻群落结构是水质、地理因子和土地利用共同作用的结果,水质起决定性作用,电导和不同形态的氮是影响附生硅藻群落结构的主要水质因素。     

Application of an unsupervised artificial neural network technique to multivariant surface water quality data

Surface water contamination from agricultural and urban runoff and wastewater discharges from industrial and municipal activities is of major concern to people worldwide. Classical models can be insufficient to visualise the results because the water quality variables used to describe dynamic pollution sources are complex, multivariable, and nonlinearly related. Artificial intelligence techniques with the ability to analyse multivariant water quality data by means of a sophisticated visualisation capacity can offer an alternative to current models. In this study, the Kohonen self-organising feature maps (SOM) neural network was initially applied to analyse the complex nonlinear relationships among multivariable surface water quality variables using the component planes of the variables to determine the complex behaviour of water quality parameters. The dependencies between water quality variables were extracted and interpreted using the pattern analysis visualised in component planes. For further investigation, the k-means clustering algorithm was used to determine the optimal number of clusters by partitioning the maps and utilising the Davies–Bouldin clustering index, leading to seven groups or clusters corresponding to water quality variables. The results reveal that the concentrations of Na, K, Cl, NH₄-N, NO₂-N, o-PO₄, component planes of organic matter (pV), and dissolved oxygen (DO) were significantly affected by seasonal changes, and that the SOM technique is an efficient tool with which to analyse and determine the complex behaviour of multidimensional surface water quality data. These results suggest that this technique could also be applied to other environmentally sensitive areas such as air and groundwater pollution.     

三峡库区古夫河水质时空分异特征

以湖北省神农架林区和兴山县境内长江三峡库区香溪河支流古夫河为研究对象,于2010年8月-2011年7月在整条河流中选取20个采样点,进行样本采集,并测定溶解氧、碱度、硬度、电导率、总磷、总氮、化学需氧量、二氧化硅、总有机碳共9项水质指标,运用多元统计方法,分析水质的时空分异特征.依据研究区土地利用类型差异,将20个采样点分成4组,即森林(A组)、耕地(B组)、水库(C组)和村镇(D组);根据该区域的水文节律,将5-10月归为湿季,其余月份为干季.判别分析和方差分析结果表明,古夫河水质具有时空显著性差异:总磷、二氧化硅、电导率、化学需氧量、总硬度和总碱度等指标具有空间显著性差异;总氮、化学需氧量、溶解氧、二氧化硅和总有机碳与季节存在显著相关性,所测9项水质指标在不同空间类别上呈现出显著的季节变化.主成分分析表明,不同空间类别上的干湿季节引起水质变化的主导因子是不同的:A组中,湿季主要体现为二氧化硅和总有机碳,干季主要体现为总磷、二氧化硅、总有机碳和化学需氧量,该组水质主要受地表径流、地质成因和风化作用等自然因素的影响;B组中,湿季主要体现为硬度和总有机碳,干季主要体现为总磷、化学需氧量、总碱度和总硬度,该组除了受自然因素的影响,还受如农业径流、未处理的生活污水排放等人为因素影响;C组中,湿季主要体现为二氧化硅、总氮和总磷,干季主要体现为总氮、总有机碳和二氧化硅,该组主要受农业径流、地表径流以及未经处理的生活污水等的影响;D组中湿季主要体现为二氧化硅、总氮和总磷,干季主要体现为碱度、硬度、总氮和总有机碳,该组主要受村镇生活污水和农业径流等的影响.结果表明,古夫河水质受自然和人为因素影响而发生变化,其中受人为因素影响更大.因此,加强水资源的管理和保护,改善水质,做好水源地的长期水质监测显得尤为重要.     

Relationship between phytoplankton and environmental factors in landscape water supplemented with reclaimed water

The water quality of Feng-qing Lake, which is a landscape lake supplemented with reclaimed water, was surveyed to investigate the relationship between phytoplankton and environmental variables. A total of 29 water samples were collected to analyze temporal variations of phytoplankton and environmental factors from July 2013 to June 2014. Six phyla and 39 genera of phytoplankton were identified when the lake was supplied with reclaimed water. Among these, Cyanophyta and Chlorophyta account for 38.46% and 30.77% of phytoplankton, respectively. The dominant species in the lake are Pseudanabaena limnetica and Chlorella vulgaris, which are present the entire year. Other leading species include Cosmarium sp. and Raphidiopsis curvata. Principal component analysis (PCA) was conducted to analyze the relationship among environmental factors. Canonical correspondence analysis (CCA) was performed to investigate the relationship between environment factors and dominant species. The PCA result showed that temperature (T), total phosphorus (TP), total nitrogen (TN), transparency, and dissolved oxygen are the main factors that affect the eutrophication level of the lake. The CCA result revealed that TN, PO₄³⁻–P, chemical oxygen demand (COD), T, and chlorophyll a exhibit a close relation with dominant species. In particular, TN, salinity, and COD influence the growth of P. limnetica; T and COD influence the growth of R. curvata; and T, PO₄³⁻–P, NH₃–N, and pH influence the growth of C. vulgaris and Cosmarium sp.     

Warming and water deficit impact leaf photosynthesis and decrease forage quality and digestibility of a C4 tropical grass

Global warming is predicted to cause more intense extreme events such as heat waves, flooding and severe droughts, producing significant effects on agriculture. In tropics, climate change will severely impact livestock production affecting water availability, forage quality and food for cattle. We investigated the isolated and combined effects of soil water deficit (wS) and + 2°C increase in canopy temperature (eT) on leaf gas exchange, chlorophyll fluorescence, carbohydrate content, forage quality and in vitro dry matter digestibility (IVDMD) of a field‐grown C4 tropical forage grass Panicum maximum Jacq. using a temperature‐free air‐controlled enhancement (T‐FACE) system. The wS and eT treatments showed no effects on photosystem II photochemistry. However, wS under ambient temperature decreased net photosynthesis rate (A), stomatal conductance (g_s) and maximum rate of carboxylation of Rubisco (V_cmax), leading to a reduced starch content in leaves. A 16% reduction in leaf dry mass (LDM) and reduction in forage quality by increasing fibers, reducing crude protein (CP) and decreasing the IVDMD was also observed by effect of wS. Warming under adequate soil moisture (eT) significantly increased LDM by 25% but reduced the forage quality, increasing the lignin content and reducing starch, CP and digestibility. The combined wSeT treatment reduced A, g_s, V_cmax and the forage quality. When compared to control, the lignin content in leaves increased by 43, 28 and 17% in wS, eT and wSeT, respectively, causing a significant reduction in IVDMD. We concluded that despite physiological mechanisms to acclimate to warming, both warming and water deficit will impair the quality and digestibility of C4 tropical pastures.     

Larval development of Culex quinquefasciatus in water with low to moderate

Population growth and urbanization have increased the potential habitats, and consequently the abundance of Culex quinquefasciatus, the southern house mosquito, a vector of West Nile Virus in urban areas. Water quality is critical in larval habitat distribution and in providing microbial food resources for larvae. A mesocosm experiment was designed to demonstrate which specific components of water chemistry are conducive to larval Culex mosquitoes. Dose–response relationships between larval development and NO₃, NH₄, and PO₄ concentrations in stream water were developed through this experiment to describe the isolated effects of each nutrient on pre‐adult development. The emergence pattern of Culex mosquitoes was found to be strongly related to certain nutrients, and results showed that breeding sites with higher PO₄ or NO₃ concentrations had higher larval survival rates. High NO₃ concentrations favor the development of male mosquitoes and suppress the development of female mosquitoes, but those adult females that do emerge develop faster in containers with high NO₃ levels compared to the reference group. The addition of PO₄ in the absence of nitrogen sources to the larval habitat slowed larval development, however, it took fewer days for larvae to reach the pupal stage in containers with combinations of NO₃ and PO₄ or NH₄ and PO₄ nutrients. Results from this study may bolster efforts to control WNV in urban landscapes by exploring water quality conditions of Culex larval habitats that produce adult mosquitoes.     

Distribution of Enteric Pathogens in Wastewater Secondary Effluent and Safety Analysis for Urban Water Reuse

Through a 1-year monitoring of enteroviruses and pathogenic bacteria in the secondary effluent using real-time polymerase chain reaction (real-time PCR), the pathogen removal requirement was evaluated for safeguarding the reclaimed water quality for urban reuse. The distribution of each pathogen in the secondary effluent was found to follow a log-normal relationship, although 50% cumulative concentrations differed much from each other (1.4 GEC/L of infectious enteroviruses, 3.1 × 10² CFU/L of Salmonella typhi, 1.0 × 10³ CFU/L of Shigella, and 3.3 × 10⁵ CFU/L of Escherichia coli). By exposure analysis regarding two reuse scenarios (golf course irrigation and recreational impoundment), risks were analyzed for pathogens in reused water based on monitoring data and dose–response relation. For enteroviruses and pathogenic bacteria, there were obvious differences in the relationship between the reliability and removal efficiency. Under an acceptable annual risk level (10^–4/a), the pathogen removal requirement depends on the manner of water reuse. In the golf course irrigation, the removal efficiency of enteroviruses, Salmonella typhi, Shigella, and Escherichia coli reach to 3.8～4.0-log, 1.4-log, 3.3-log, and 2.0-log, respectively, in order to ensure 95% reliability. However, if wastewater is reused for recreational impoundment, only a further increase around 1.5-log removal efficiency of pathogens can meet the requirement for the same reliability.     

七项河流附着硅藻指数在东江的适用性评估

综合运用因子分析、聚类分析、箱型图分析等统计方法评估了河流附着硅藻生物指数(Biological Diatom Index,IBD)、硅藻营养化指数(Trophic Diatom Index,TDI)、斯雷德切克指数(Sládecˇek’s Index,SLA)、特定污染敏感指数(Specific Polluosensitivity Index,IPS)、硅藻属指数(Generic Diatom Index,IDG)、戴斯指数(Descy Index,DESCY)和欧盟硅藻指数(European Economic Community Index,CEE)在东江流域河流水质评价中的适用性。结果显示:SLA与IPS,CEE显著相关(P<0.05),CEE与TDI不相关,其余指标间均极显著相关(P<0.01)。SLA与13项水质理化指标均无相关性,TDI与含氯度(Cl)显著负相关,CEE与溶解氧(DO)、电导率(Cond.)、总氮(TN)显著正相关(P<0.05),其余指标与氨氮(NH4-N)、pH不存在线性相关,与五日生化需氧量(BOD5)、高锰酸盐指数(CODKMnO4)、亚硝氮(NO2-N)、硝氮(NO3-N),总磷(TP)具极显著相关性(P<0.01)。13项水质理化指标中主成分负荷贡献大于50%的八项理化参数DO、BOD5、CODKMnO4、TN、NO3-N、NO2-N、TP和SiO2将试验区水质分为四组。IPS、IBD、IDG和CEE与水质物化分类一致性较好。IPS、IBD、IDG和CEE的逐步判别分析(引入P=0.20,剔除P=0.25)显示IPS和CEE都只选出了NO2-N,分类判别的正确率分别为55.6%和48.1%;IBD引入了NO2-N,CODKMnO4和DO 3个解释变量,判别正确率74.1%;IDG引入BOD5和NO3-N两个变量,分组正确率63.0%。硅藻群落聚类显示,IBD和IDG在水质物化分类的箱型图中呈现出明显合理的趋势。以上研究表明IBD和IDG硅藻指数最适合用于东江河流水质生物监测与评价。     

Integrated stream and wetland restoration: A watershed approach to improved water quality on the landscape

Water quality in Upper Sandy Creek, a headwater stream for the Cape Fear River in the North Carolina Piedmont, is impaired due to high N and P concentrations, sediment load, and coliform bacteria. The creek and floodplain ecosystem had become dysfunctional due to the effects of altered storm water delivery following urban watershed development where the impervious surface reached nearly 30% in some sub-watersheds. At Duke University, an 8-ha Stream and Wetland Assessment Management Park (SWAMP) was created in the lower portion of the watershed to assess the cumulative effect of restoring multiple portions of stream and former adjacent wetlands, with specific goals of quantifying water quality improvements. To accomplish these goals, a three-phase stream/riparian floodplain restoration (600 m), storm water reservoir/wetland complex (1.6 ha) along with a surface flow treatment wetland (0.5 ha) was ecologically designed to increase the stream wetland connection, and restore groundwater wetland hydrology. The multi-phased restoration of Sandy Creek and adjacent wetlands resulted in functioning riparian hydrology, which reduced downstream water pulses, nutrients, coliform bacteria, sediment, and stream erosion. Storm water event nutrient budgets indicated a substantial attenuation of N and P within the SWAMP project. Most notably, (NO₂⁻ + NO₃⁻)-N loads were reduced by 64% and P loads were reduced by 28%. Sediment retention in the stormwater reservoir and riparian wetlands showed accretion rates of 1.8 cm year⁻¹ and 1.1 cm year⁻¹, respectively. Sediment retention totaled nearly 500 MT year⁻¹.     

Steroid hormone concentrations and physiological toxicity of water from selected dams in Namibia

Namibia is a semi-arid to arid country and has most of its surface water in dams built on ephemeral rivers. Whilst water quality is often measured in terms of bacterial contamination and general physico-chemical characteristics, this study extends water quality assessment to include steroid hormone presence and potential physiological toxicity. This is the first study to determine these parameters in dams in Namibia at various stages of the seasons. Seven bioassays were used to determine oestradiol (E₂), oestrone (E₁) and testosterone (T) concentrations, as well as neurotoxicity, cytotoxicity and immunotoxicity, in water sampled during 2010 and 2011. Oestradiol and E₁ concentrations of up to 7.2 pg ml^–1 and 7.6 pg ml^–1, respectively, were recorded. Testosterone concentrations measured up to 19 pg ml^–1. No cytotoxic effects were detected, while acetylcholinesterase (AChE) inhibition assays indicated low neurotoxic effects in Goreangab Dam (18% AChE inhibition) and no neurotoxic effects in other samples. The immune system biomarker interleukin-6 was high in all samples (457 pg ml^–1; SD 54), with interleukin-10 being high only at Avis (46 pg ml^–1), Goreangab (74 pg ml^–1) and Swakoppoort (81 pg ml^–1) dams. The results suggest that water from Goreangab and Swakoppoort dams may have the potential to modulate endocrine systems, and shows physiological toxicity.     

Prediction of hydraulic conductivity loss from relative water loss: new insights into water storage of tree stems and branches

More frequently occurring, drought waves call for a deeper understanding of tree hydraulics and fast and easily applicable methods to measure drought stress. The aim of this study was to establish empirical relationships between the percent loss of hydraulic conductivity (PLC) and the relative water loss (RWL) in woody stem axes with different P₅₀, i.e. the water potential (Ψ) that causes 50% conductivity loss. Branches and saplings of temperate conifer (Picea abies, Larix decidua) and angiosperm species (Acer campestre, Fagus sylvatica, Populus x canescens, Populus tremula, Sorbus torminalis) and trunk wood of mature P. abies trees were analyzed. P₅₀ was calculated from hydraulic measurements following bench top dehydration or air injection. RWL and PLC were fitted by linear, quadratic or cubic equations. Species‐ or age‐specific RWLs at P₅₀ varied between 10 and 25% and P₈₈, the Ψ that causes 88% conductivity loss, between 18 and 44%. P₅₀ was predicted from the relationship between Ψ and the RWL. The predictive quality for P₅₀ across species was almost 1:1 (r² = 0.99). The approach presented allows thus reliable and fast prediction of PLC from RWL. Branches and saplings with high hydraulic vulnerability tended to have lower RWLs at P₅₀ and at P₈₈. The results are discussed with regard to the different water storage capacities in sapwood and survival strategies under drought stress. Potential applications are screening trees for drought sensitivity and a fast interpretation of diurnal, seasonal or drought induced changes in xylem water content upon their impact on conductivity loss.     

Grey water biodegradability

Knowing the biodegradability characteristics of grey water constituents is imperative for a proper design and operation of a biological treatment system of grey water. This study characterizes the different COD fractions of dormitory grey water and investigates the effect of applying different conditions in the biodegradation test. The maximum aerobic and anaerobic biodegradability and conversion rate for the different COD fractions is determined. The results show that, on average, dormitory grey water COD fractions are 28% suspended, 32% colloidal and 40% dissolved. The studied factors incubation time, inoculum addition and temperature are influencing the determined biodegradability. The maximum biodegradability and biodegradation rate differ between different COD fractions, viz. COD_ss, COD_col and COD_diss. The dissolved COD fraction is characterised by the lowest degradation rate, both for anaerobic and aerobic conditions. The maximum biodegradability for aerobic and anaerobic conditions is 86 and 70% respectively, whereas the first order conversion rate constant, k ₂₀, is 0.119 and 0.005 day⁻¹, respectively. The anaerobic and aerobic conversion rates in relation to temperature can be described by the Arrhenius relation, with temperature coefficients of 1.069 and 1.099, respectively.