Concentration‐Duration‐Frequency Curves for Stream Turbidity: Possibilities for Assessing Biological Impairment1

Abstract: Siltation and subsequent biological impairment is a national problem prompting state regulatory agencies to develop sediment total maximum daily loads (TMDL) for many streams. To support TMDL targets for reduced sediment yield in disturbed watersheds, a critical need exists for stream assessments to identify threshold concentrations of suspended sediment that impact aquatic biota. Because of the episodic nature of stream sediment transport, thresholds should not only be a function of sediment concentration, but also of duration and dose frequency. Water quality sondes can collect voluminous amounts of turbidity data, a surrogate for suspended sediment, at intervals that can be used to characterize concentration, duration, and frequency of elevated turbidity events. To characterize turbidity sonde data in an ecologically relevant manner, a methodology for concentration‐duration‐frequency (CDF) curves was developed using turbidity doses that relate to different levels of biological impairment. To illustrate this methodology, turbidity CDF curves were generated for two sites on Little Pigeon River in the Great Smoky Mountains National Park, Tennessee, using over 30,000 sonde data measurements per site for a one‐year period. Utilizing a Poisson arrival approach, turbidity spikes were analyzed stochastically by observing the frequency and duration of recorded events over a turbidity level that relates to a biological dose response. An exponential equation was used to fit duration and frequency of a specified turbidity level to generate concentric‐shaped CDF curves, where at specific turbidities longer durations occurred less frequently and conversely shorter durations occurred more frequently. The significance of the equation fit to the data was accomplished with a Kolmogorov‐Smirnov goodness‐of‐fit test. Our findings showed that the CDF curves derived by an exponential function performed reasonable well, with most curves significant at a 95% confidence level. These CDF curves were then used to demonstrate how they could be used to assess biological impairment, and identify future research needs for improved development of sediment TMDLs.     

Nutrient Bioassays of Growth Parameters for Algae in the North Bosque River of Central Texas1

Abstract: Nutrient dose‐response bioassays were conducted using water from three sites along the North Bosque River. These bioassays provided support data for refinement of the Soil and Water Assessment Tool (SWAT) model used in the development of two phosphorus TMDLs for the North Bosque River. Test organisms were native phytoplanktonic algae and stock cultured Pseudokirchneriella subcapitata (Korshikov) Hindak. Growth was measured daily by in vivo fluorescence. Algal growth parameters for maximum growth (μ_max) and half‐saturation constants for nitrogen (K_N) or phosphorus (K_P) were determined by fitting maximum growth rates associated with each dose level to a Monod growth rate function. Growth parameters of native algae were compared between locations and to growth parameters of P. subcapitata and literature values. No significant differences in half‐saturation constants were indicated within nutrient treatment for site or algal type. Geometric mean K_N was 32 μg/l and for K_P 7 μg/l. A significant difference was detected in maximum growth rates between algae types but not between sites or nutrient treatments. Mean μ_max was 1.5/day for native algae and 1.2/day for stock algae. These results indicate that watershed‐specific maximum growth rates may need to be considered when modeling algal growth dynamics with regard to nutrients.     

骆马湖及主要入湖河流表层水体中抗生素的赋存特征及风险评价

采用固相萃取-超高效液相色谱-串联质谱法(SPE-UPLC-MS/MS)分析了骆马湖及主要入湖河流表层水体中磺胺类(SAs)、喹诺酮类(QUs)、四环素类(TCs)、大环内酯类(MLs)和青霉素类(PLs)这5类39种抗生素的浓度水平,分析了主要入湖河流的污染贡献率,并评价了抗生素潜在的生态与健康风险.结果表明,42个...     

基于微生物完整性指数的河流健康评价 ——以无锡市为例

生物完整性指数（Index of biotic integrity,IBI）被广泛运用于河流的健康评价.然而,随着人类活动对河流影响的增加,传统指示生物多样性的损失降低了评价的准确性.在高度受影响的水体环境中,微生物群落被证明是更敏感的生态健康指标.本研究采用Illumina高通量测序技术,于2018年冬季和2019年春季对无锡市境内8条河流的微生物群落组成进行了分析,从群落组成/相对丰度、丰富度/多样性、敏感性/耐受性3个角度确定了候选指标.并对传统的核心指标筛选方法进行了改进,通过差异性分析、箱线图检验、Speraman相关性分析,建立了冬、春两季的微生物生物完整性指标框架.评价结果表明,M-IBI能有效区分不同程度的受损位点,且与水质状况和物理生境存在显著的相关性.总体而言,M-IBI为城市河流生态状况提供了一种新的评价工具.     

7条环太湖河流沉积物氮含量沿程分布规律

2009年9月采集7条主要环太湖河流沿程37个断面的沉积物样,测定了表层沉积物中总氮(TN)、氨氮(NH4+-N)、硝氮(NO3--N)和有机氮(ON)含量,揭示分布特征,旨在为太湖水体富营养化防治提供基础数据.结果表明,这些表层沉积物TN平均1 303.49 mg.kg-1,最大和最小值分别在社渎港和长兜港;NH4+-N和ON的空间分布与TN基本一致,其平均含量分别为221.57 mg.kg-1和1 095.71 mg.kg-1,各沉积物中NO3--N含量较低,均不足TN的1%,平均含量0.79 mg.kg-1.7条河流沉积物整体上以ON为主,NH4+-N为无机氮主要存在形式,多数河流表层沉积物氮含量沿程变化明显.     

潮汕地区入海河流及水生生物中PPCPs分布特征及风险评估

为了解南海海岸带地区河流及其生物体中药物及个人护理用品（pharmaceuticals and personal care products,PPCPs）的污染水平、空间分布特征及其潜在风险,本研究采用固相萃取和高效液相色谱-串联质谱测定了潮汕地区7条河流水样及生物样品中的20种PPCPs.结果表明,高达16和18种PPCPs分别能在潮汕入海河流和生物体中检测出,河流和生物体中目标物的含量范围分别为0.30~2223 ng ·L^-1和0.143~80.3ng ·g^-1,且多种污染物检出率较高.PPCPs在潮汕各河流和生物中的含量差异较大,PPCPs浓度最高的河流为黄冈河、练江和黄江,磺胺甲（口恶）唑和咖啡因是主要的污染物;黄冈河、韩江、练江和螺河生物体中的PPCPs总浓度较高于龙江和溶江生物中PPCPs的含量,甲氧苄氨嘧啶、磺胺噻唑和咖啡因是生物中主要的污染物,鱼类的PPCPs含量总量明显高于蟹类和贝类.计算所得河流生物浓缩系数（BCF）值显示多种目标物在潮汕生物体内具有累积性,其中鱼类中的BCF值较高,比蟹类和贝类更易形成生物累积.运用风险商值模型（RQ）评价12种PPCPs在潮汕地区河流生态环境中的潜在风险,发现蚤类和藻类遭受的风险明显高于鱼类,若以二者为保护对象,磺胺甲（口恶）唑、红霉素和磺胺嘧啶的RQ值均大于1,分别对黄冈河藻类生物、练江藻类生物以及黄江蚤类生物具有潜在生态风险.     

三峡入库河流澎溪河回水区消落带与岸边土壤磷形态及其分布特征研究

应用沉积物中磷形态的分级提取法对三峡入库河流澎溪河回水区消落带和岸边土壤不同形态P进行分级测定,分析了各形态磷之间以及各形态磷与样品理化性质.结果表明,消落带土壤总磷含量在283.3～3281.6mg.kg-1之间,平均为780.6mg.kg-1,岸边土壤中总磷含量在395.0～1751.5mg.kg-1之间,平均含量...     

Clean-up and disposal process of polluted sediments from urban rivers

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基于国际河流开发的国家水质标准差异对比分析

就国际河流相邻国家用水特点,分析我国与俄罗斯在地表水用于生活饮用水和农田灌溉水2个方面的水质标准进行对比分析,具体分析这2个标准在两国之间的总体差异和具体指标差异。分析的总体结论是俄罗斯的水质标准在项目分类、具体评价指标方面比我国丰富,具体指标的限值要稍严于我国标准。针对两国水质标准的不同,分析在国际河流开发利用中可能导致的冲突及这种差异对我国的影响,并从社会经济发展需求、水资源开发及相关政策关注重点等方面揭示两国水质标准存在差异的原因,为有效解决由于水质标准差异导致的争端提供科学依据。     

潜流-表面流复合人工湿地的河道水质净化效果

针对太湖流域的小河道水环境污染普遍较重的现状,结合潜流和表面流人工湿地系统技术的优点,设计并制作了阶梯式的复合人工湿地系统,前端采用潜流,后端采用表面流,试验区种植密度为25株/m2的茭草,研究其组合工艺对河道水质的净化效果,以期为河道人工湿地的设置提供技术参数。结果表明,复合人工湿地系统具有较强的污染物去除能力,HRT为3.4d时,7—12月对TN、TP、NH+4-N和高锰酸盐指数的平均去除率分别达到了64.3%、63.9%、74.6%、51.1%,较同期相同HRT下潜流人工湿地去除率分别提高了12.1、10.6、1.8、5.1百分点。其中,前端0.25距离分数的去除率占各自总去除率的74.5%～91.2%。