南京市地表水溶解氧分布特征及低氧成因初探——以外秦淮河七桥瓮为例

于2018—2021年对南京市及国考断面七桥瓮进行水质调查,分析其溶解氧变化特征,采用水质水量联合评价及皮尔逊相关分析法,并结合水文气象等相关信息,对南京市地表水溶解氧分布特征及国考七桥瓮断面低氧成因进行研究分析。结果表明,南京市地表水溶解氧浓度夏季最低,中心主城区及附近区域溶解氧浓度均相对较低。七桥瓮断面溶解氧浓度在2.25~11.07 mg/L,其中5—9月溶解氧易出现超标波动。溶解氧浓度昼间高于夜间,与pH值呈正相关关系,与水温、高锰酸盐指数、氨氮、总磷均呈负相关关系。水温和上游来水带入的耗氧污染物是七桥瓮断面溶解氧偏低的主要成因,其中,溶解氧浓度与水温相关性最为显著。研究结论可为七桥瓮断面稳定达标提供基础支撑,为秦淮河流域精准治污提供技术依据,为南京市水环境多源同治提供治理思路。     

阅海湿地叶绿素a季节变化特征及其与环境因子的关系

2020年春、夏、秋、冬四季对阅海湿地进行水样采集并测定叶绿素a(Chl-a)等10种环境因子，采用相关分析、逐步回归分析和通径分析进行分析评价。结果表明：阅海湿地深水区与浅水区的Chl-a质量浓度季节差异较大，夏、秋季较高，春、冬季较低；空间上深水区高于浅水区。对深水区Chl-a质量浓度影响的环境因子依次为水温、I_Mn、DO,其中水温为正向直接作用，I_Mn、DO为负向直接作用；对浅水区Chl-a质量浓度影响的环境因子依次为TP、BOD₅,均为正向直接作用。TN对阅海湿地Chl-a质量浓度影响不大，控制水体含磷营养盐类物质及有机物的输入量是防止阅海湿地Chl-a质量浓度过高的主要措施。     

三峡库区大宁河2010年春季水华特征

以大宁河春季水华期间调查数据为基础,运用数理统计分析手段,通过描述大宁河春季水华期藻类及主要理化因子分布特征,揭示出影响藻类生长的主要因子。结果表明:大宁河春季水华期水华河段水体氮、磷含量较高,总氮浓度为1.2～4.11mg/L,平均值为1.748mg/L,总磷浓度为0.027～0.615mg/L,氮磷比均值为17.5。春季水华藻类适宜的光照强度为1400～3800lx,水温为13.0～14.0℃时叶绿素a含量有最大增长,平均水温为13.4℃,藻密度与总氮、总磷、水温、DO、pH、浊度、高锰酸盐指数呈显著正相关关系,与透明度呈负相关关系。回水河段流速小于0.05m/s,流速是藻类生长最主要的限制因子。大宁河回水河段春季水华藻类分布较广,主要有甲藻门、绿藻门、硅藻门、隐藻门、蓝藻门、裸藻门和黄藻门7门28属,其中甲藻门分布最广,其次是绿藻门。春季水华优势种主要有甲藻门的拟多甲藻,绿藻门的衣藻、小球藻,硅藻门的直链藻,蓝藻门的色球藻等。     

南亚热带特大型水库季节性分层特征研究

新丰江水库是典型的南亚热带深水贫营养水库。为了解其水库的季节性分层特征，于2020年3月—2021年2月，对水库的水温，溶解氧（DO），pH值，总磷（TP），总氮（TN），高锰酸盐指数（I_Mn）和叶绿素a浓度（Chl.a）季节动态和垂直分层结构进行分析。结果表明，水库分层时间较短，混合期为1—4月和11—12月，热分层期为5—10月，夏季和秋季出现明显分层现象。水体分层结构对DO，pH值，TN，I_Mn和Chl.a的垂直分布有一定影响作用。水库未出现较明显的DO分层和季节性缺氧现象，水库表层水体DO值大于《地表水环境质量标准》（GB 3838—2002）中I类水质标准值（7.5mg/L），但是水体温跃层内DO值从Ⅰ类下降为Ⅱ—Ⅲ类，说明其可能面临潜在的生态风险，不利于水生态环境系统的稳定。     

藻型湖泊大量藻类衰亡后致嗅物的分析以及水质变化的研究

藻类大量死亡后极易产生致嗅物.我们模拟了藻类的生长死亡过程,观测除藻后水体理化性质和生物性质的改变情况以及致嗅物的成分及浓度,以确定致嗅物质产生的途径.由于藻类死亡后细胞解体,藻类细胞中的氮、磷物质释放到水体中,导致水体的富营养化程度反而升高,而叶绿素-a也呈现下降趋势,整个试验过程后期溶解氧为0,水体产生嗅味物质,可采用吹扫捕集/固相微萃取—气相色谱—质谱法和顶空固相微萃取气质联用法分析致嗅物质.实验证明,当藻型湖泊的藻类被基本去除后,整个水体的初级生产力受到严重的破坏,威胁到水生态系统的安全性,可导致水体进一步恶化.     

西安市景观水体营养状态调查及浮游藻类多样性研究

对西安市城区景观水体浮游藻类状况及生物多样性进行了研究。结果表明,7个景观水体中有5个水体的水质未达到Ⅴ类水质标准,主要超标项目为pH值和TN;7个水体的ρ(N)/ρ(P)为16.6~43.6,磷为限制性因子;其中2个水体富营养化严重,DO含量低,水质达不到要求,其优势藻种为蓝藻门,含量占浮游藻类总数的64.3%~93.4%;而水质较好的贫营养水体优势种为黄藻门,含量占到浮游藻类总数的54.3%;通过6种生物多样性指数与景观水体营养状态的拟合,发现MeNaughton's多样性指数适合城区景观水体的富营养化评价。     

渔洞水库值异常成因分析及水资源保护建议

文章结合水环境监测与评价工作实际,分析了渔洞水库水体pH值变化成因,藻类的生长与pH及藻类与营养盐之间的关系,认为水体pH值变化存在两个方面因素,内因方面是渔洞水库水体中含有较为丰富的氮磷等营养元素,外因方面是气温,气温升高引起水温的升高和水库水体的分层现象,导致水体上下水层间好氧和厌氧加剧,从而引起水环境的周期性污染。针对近年来渔洞水库治理的实际,提出外源和内源污染治理措施及水库管理建议;同时对渔洞水库pH值异常变化及水资源保护作一小结。     

杭州市钱塘江干支流水质多元统计分析

运用多元统计方法分析了杭州市钱塘江干支流上26个断面的水质监测指标。利用系统聚类分析方法将断面所在河流分为3组,与钱塘江流域污染空间分布现状基本一致。对各组水质的主成分分析表明,第1组河流水质以有机污染为主,水体中氮、磷营养盐浓度较高,水体污染程度较轻,污染来源相对单一;第2组河流水体受有机物、重金属、石油类等多个污染指标的影响,水体水质较第1组差,污染来源相对复杂;第3组河流水体既有一般有机污染,也有重金属、有毒有害物质的污染,水体水质污染严重。     

梅梁湖水体浮游植物与环境因子的关系

根据2008年的4月—11月梅梁湖水域应急监测数据,探讨了梅梁湖水体浮游植物与环境因子的关系。相关性分析结果表明,蓝绿藻含量与TP、pH值和DO呈极显著正相关;与TN、SD和EC呈极显著负相关;与NH3-N呈显著负相关。多元逐步回归分析结果表明,梅梁湖浮游植物生长受多个环境因子的共同影响,但主要为TP、TN、水温和风速。     

SP模型缺陷及改进的研究

SP模型应用于高污染河流的水质分析时,因起始BOD浓度大,得出负数的DO临界值,而导致SP模型失效。本研究以BOD浓度L与自净系数f、氧亏值D乘积fD的比较为判据,分析耦合微分方程的性质及大气复氧速率之间的变化关系,通过将BOD—DO变化划分为三个阶段,完成了BOD浓度衰减及大气复氧过程的求解,这一改进可以有效弥补SP的模型缺陷。     

Analysis of hypoxia in the western interior parts of the Ariake Sea, Japan, using a box model

To clarify the mechanism of hypoxia in the western interior parts of the Ariake Sea (WIAS), field observation data collected in the period of 1972-2004 were analyzed using a two-layer box model. Monthly averages of advection velocity, vertical diffusion coefficient (K(z)), and biochemical oxygen consumption rate (R) in WIAS were evaluated quantitatively during the above period. The estimated advection velocity comparatively corresponded to the observed residual flow pattern of bay head in summer and winter. The estimated K(z) was relatively high (0.6-5.3 cm(2) s(?-1)) from September to March but lower (0.2-0.4 cm(2) s(?-1)) from April to August. The estimated R ranged from 0.30 to 0.46 mg L(?-1) day(?-1) during May to August. In summer, the temporal variation of dissolved oxygen (DO) concentration in the lower layer was controlled largely by K ( z ) and R. Monthly variations of K(z), R, and degree of density stratification (P) in the 1970s, the 1980s, and the 1990s-early 2000s were analyzed. P, K ( z ), and R were not significantly different among the calculated periods (p = 0.93, 0.23, and 0.49). However, the variations of R in summer between the 1970s and the other calculated periods changed. DO consumption period was longer in the 1980s and the 1990s-early 2000s than in the 1970s. R in the 1980s was highest among the calculated periods. The increase in R in the 1980s was caused by the increase in organic matter load originating from red tide phytoplankton due to a decrease in the suspension feeders.     

浙江近岸海域春季表层溶解氧饱和度分布及影响因素

根据2014年春季对浙江省近岸海域溶解氧的调查结果,结合现场的温度和盐度,得出溶解氧饱和度的平面分布,并在此基础上探讨了饱和度与温度、盐度、化学需氧量、浮游植物丰度之间的关系。结果显示,浙江省近岸海域溶解氧饱和度范围为92.1%~120%,均值为100%。总体呈西部沿岸低,东部外海高的平面分布趋势。溶解氧饱和度高值区与浮游植物丰度的高值区一致。低饱和区域化学需氧量含量基本高于1 mg/L。陆源径流和有机物质耗氧分解是沿岸低饱和区域主要控制因素,外海水和浮游植物光合作用是高饱和区域主要控制因素。径流和外海水对有机物质分解和浮游植物光合作用有一定的调控作用。     

Monitoring sediment oxygen demand for assessment of dissolved oxygen distribution in river

Sediment oxygen demand (SOD) has become an integral part of modeling dissolved oxygen (DO) within surface water bodies. Because very few data on SOD are available, it is common for modeler to take SOD values from literature for use within DO models. SOD is such an important parameter in modeling DO that this approach may lead to erroneous results. This paper reported on developing an approach for monitoring sediment oxygen demand conducted with undisturbed sediment core samples, where the measured results were incorporated into a water quality model for simulating and assessing dissolved oxygen distribution in the Xindian River of northern Taiwan. The measured results indicate that a higher freshwater discharge results in a lower SOD. Throughout a 1-year observation in 2004, the measured SOD ranged from 0.367 to 1.246 g/m(2)/day at the temperature of 20°C. The mean values of the measured SOD at each station were adopted in a vertical two-dimensional water quality model to simulate the DO distribution along the Xindian River. The simulating results accurately depict the field-measured DO distribution during the low and high flow conditions. Model sensitivity analyses were also conducted with increasing and decreasing SOD values for the low and high flow conditions and revealed that SOD had a significant impact on the DO distribution along the Xindian River. The present work combined with field measurements and numerical simulation should assist in river water quality management.     

Dissolved oxygen content as an index of water quality in San Vicente Bay,Chile (36 degrees 45'S)

The present report describes some effects of industrial and municipal effluents on the waters of San Vicente Bay. Analyses ofthe main substances contained in the fishing industry effluentsuggest rating criteria based on the oxygen saturation of thewater as an assessment of organic pollution. Six cruises were carried out throughout the Bay, from June to December 1996. Watersamples were analyzed for dissolved oxygen, oil and grease content, and sediment samples for organic matter content. Waterparameters (salinity, temperature) were used to characterize theBay's hydrography, and to calculate values for oxygen saturation. The measurements demonstrated a local broad range of oxygen deficit, with a maximum of 45% in the winter to 95% in the spring. In November more than 65% of the Bay's area showed oxygendeficits greater than 40%. Organic matter was unusually high insediments along the northern sector of the Bay. The results suggest that the oxygen depletion was a representative parameterfor establishing a relative scale of water quality in this Bay.     

Heavy metal concentrations in water and sediments in Tasik Chini, a freshwater lake, Malaysia

The purpose of this paper are to determine the concentration of heavy metals namely cadmium (Cd), copper (Cu) and lead (Pb) in water and sediment; and to investigate the effect of sediment pH and sediment organic matter on concentration of cadmium, copper and lead in sediment at oxidation fraction. For this purpose the concentration of heavy metals were measured in water and sediments at 15 sites from Tasik Chini, Peninsular Malaysia. The sequential extraction procedure used in this study was based on defined fractions: exchangeable, acid reduction, oxidation, and residual. The concentration of heavy metals in residual fraction was higher than the other fractions. Among the non-residual fractions, the concentration of heavy metals in organic matter fraction was much higher than other fractions collected from all sampling sites. The pH of the sediment in all sites was acidic. The mean pH ranges from 4.8 to 5.5 with the higher value observed at site 15. Results of organic matter analysis showed that the percentage of organic matter present in sediment samples varies throughout the lake and all sites of sediments were relatively rich in organic matter ranging from 13.0% to 34.2%. The highest mean percentage of organic matter was measured at sampling site 15, with value of 31.78%.     

Long-term seasonal changes of the Danube River eco-chemical status in the region of Serbia

Seasonal spatial and temporal changes of selected eco-chemical parameters in section of the Danube River flowing through Serbia were analyzed. Data for electrical conductivity (EC), dry and suspended matter, residue on ignition, chemical oxygen demand (COD), biochemical oxygen demand (BOD-5), ultraviolet extinction, dissolved oxygen (DO), oxygen saturation, pH, nitrates, total phosphorus, and nitrogen were collected between 1992 and 2006. The use of monthly medians combined with linear regression and two-sided t test has been proven to be the best approach for resolving trends from natural variability of investigated parameters and for determining trend significance. Patterns of temporal changes between different months were examined. It was also determined that spatial trends of some parameters oscillate in predictable manner, increasing in one part of the year and declining in the other. Regression slope coefficients, an excellent indicator for determining when the water quality is changing the most along the course of the Danube, reach their maximum during summer for temperature (t), electric conductivity, nitrates, and total N, while in the same season suspended matter, COD, BOD-5, DO, and oxygen saturation coefficients reach their minimum. Correlations for used data sets of selected parameters were analyzed for better understanding of their behavior and mutual relations. It was observed that as Danube flows through Serbia, its general eco-chemical status either stagnates or improves, but the rate of river self-purification often depends on the season of the year.     

Spatial and temporal variation in suspended sediment, organic matter, and turbidity in a Minnesota prairie river: implications for TMDLs

The Minnesota River Basin (MRB), situated in the prairie pothole region of the Upper Midwest, contributes excessive sediment and nutrient loads to the Upper Mississippi River. Over 330 stream channels in the MRB are listed as impaired by the Minnesota Pollution Control Agency, with turbidity levels exceeding water quality standards in much of the basin. Addressing turbidity impairment requires an understanding of pollutant sources that drive turbidity, which was the focus of this study. Suspended volatile solids (SVS), total suspended solids (TSS), and turbidity were measured over two sampling seasons at ten monitoring stations in Elm Creek, a turbidity impaired tributary in the MRB. Turbidity levels exceeded the Minnesota standard of 25 nephelometric units in 73% of Elm Creek samples. Turbidity and TSS were correlated (r ²?=?0.76), yet they varied with discharge and season. High levels of turbidity occurred during periods of high stream flow (May–June) because of excessive suspended inorganic sediment from watershed runoff, stream bank, and channel contributions. Both turbidity and TSS increased exponentially downstream with increasing stream power, bank height, and bluff erosion. However, organic matter discharged from wetlands and eutrophic lakes elevated SVS levels and stream turbidity in late summer when flows were low. SVS concentrations reached maxima at lake outlets (50 mg/l) in August. Relying on turbidity measurements alone fails to identify the cause of water quality impairment whether from suspended inorganic sediment or organic matter. Therefore, developing mitigation measures requires monitoring of both TSS and SVS from upstream to downstream reaches.     

Influence of environmental properties on macrobenthos in the northwest Indian shelf

The paper deals with the standing stock of macrobenthic infauna and associated environmental factors influencing the benthic community in the shelf region of the northwest Indian coast. The data were collected onboard FORV Sagar Sampada during the winter monsoon (January–February, 2003) to understand the community structure and the factors influencing the benthic distribution. The environmental parameters, sediment characteristics and macrobenthic infauna were collected at 26 stations distributed in the depths between 30 and 200 m extending from nobreak{Mormugao} to Porbander. Total benthic abundance was high in lower depths (50–75 m), and low values noticed at 30 m depth contour was peculiar. Polychaetes were the dominant group and were more abundant in shallow and middle depths with moderate organic matter, clay and relatively high dissolved oxygen. On the other hand crustaceans and molluscs were more abundant in deeper areas having sandy sediment and low temperature. High richness and diversity of whole benthic groups observed in deeper depths counter balanced the opposite trend shown by polychaete species. Generally benthos preferred medium grain sized texture with low organic matter and high organic matter had an adverse effect especially on filter feeders. Deposit feeding polychaetes dominated in shallow depths while carnivore species in the middle depths. Ecologically, benthos were controlled by a combination of factors such as temperature, salinity, dissolved oxygen, sand and organic matter and no single factor could be considered as an ecological master factor.