Correlation of the methylating capacity of river and marine sediments to their organic sediment index

Methylation experiments of the metals Sn, Pb and Hg were carried out using representative terrestrial and marine sediment samples from the Axios river and Thermaikos Gulf in northern Greece. GC-FID, GC-TCD and GC-MS were used. The experiments were carried out on sterilised and bioactive samples by adding pure metals and metal salts (chloride, nitrate, oxalate, acetic, penicillaminic, methioninic and cysteinic). Except for sterilised HgCl2, methylated derivatives of Sn, Pb and Hg were produced only from bioactive sediments, and therefore higher yields were measured when nutrients were added to the sediments. Volatile products (CH4, CO2, H2S) of biological activity range between 35 and 250 mg l-. The correlation of methylation yield with organic sediment index (OSI), determined as the wt% product of [organic carbon] × [organic nitrogen], is positive for all the metals and metal salts added in the sediments. Methylation yields for Hg are found to be four orders of magnitude higher than those of Pb and Sn. In low OSI (terrestrial) sediments, the rate of Hg-methylation is higher than those of Pb and Sn. In high OSI (marine) sediments, where methylation of most of the contained Hg has taken place, methylation of Pb is slightly faster than Sn.     

HCI改性沸石和方解石复合覆盖层控制底泥氮磷释放的效果及机理研究

提出了HCl改性沸石和方解石复合覆盖控制底泥氮磷释放的新方法,利用摇床振荡试验和底泥氮磷释放控制模拟试验,设计了5种底泥处理方案,重点针对HCl改性沸石和方解石复合覆盖技术研究了其抑制底泥氮磷释放的效果及机理.结果表明,方解石覆盖层可以较好地抑制底泥磷的释放,而对底泥氨氮释放的抑制效果较差.天然沸石和方解石复合覆盖层不仅可以有效地抑制底泥氨氮的释放,而且可以有效地抑制底泥磷的释放.采用HCl对沸石进行改性,可以提高沸石和方解石复合覆盖层抑制底泥磷释放的效率,模拟期间复合覆盖层对底泥磷释放通量的抑制率由天然沸石的84%提高到HCl改性沸石的91%.采用HCl对沸石进行改性,降低了沸石和方解石复合覆盖系统有效控制底泥氨氮释放的持续时间,与天然沸石相比,相同投加量条件下HCl改性沸石有效控制底泥氨氮释放的持续时间缩短了1/3左右.采用HCl对沸石进行改性增强了复合覆盖系统抑制底泥磷释放效率的机理与HCl改性降低了沸石Na 的交换量并提高了沸石H 的交换量相关.     

桑沟湾沉积物中磷的赋存形态及生物有效性

以桑沟湾表层沉积物为研究对象,利用连续提取法对8个采样点沉积物中磷的赋存形态、含量及分布特征进行了研究,并探讨了磷的生物有效性.结果表明：①无机磷（IP）是桑沟湾表层沉积物中磷（TP）的主要形态,平均占总磷的73.33%,有机磷（OP）只占较小的比例.②无机磷中钙结合磷占的比例相对较大,平均占总磷的45.22%,是沉积物中磷的主要赋存形态,可交换磷、铁结合磷、碎屑磷占总磷的比例分别为9.92%、4.74%、13.46%.③对各形态磷的相关分析结果表明,总磷的含量及空间分布主要受有机磷的影响与控制(P<0.05),无机磷受自生钙结合磷的影响较大(P<0.01).④磷的生物有效性分析结果表明,桑沟湾表层沉积物中潜在生物有效性磷的含量为358.05～448.39 μg/g,平均占总磷的86.54%,具有很强的释磷潜力.     

海河干流表层沉积物总磷、总铁和有机质的含量及相关性分析

采用深水表层沉积物采样器采集海河干流8个断面的表层沉积物,测定不同粒径表层沉积物的总磷(TP)、总铁(TFe)和有机质(OM)含量,并采用多元线性回归分析方法对TP与TFe和OM含量进行相关性分析.结果表明:海河干流表层沉积物的颗粒组成除光华桥断面分布较均匀外,其余各断面主要以砂粒(>54%)为主;沉积物的TP含量为29.00～78.99 μmol/g,TFe含量为595.67～719.91 μmol/g,w(OM)为3.77%～8.79%;同一断面不同粉砂粒之间的TP,TFe和OM含量没有显著性差异(P>0.05),而不同断面之间的差异十分显著(P<0.01).TP与OM和TFe的相关分析结果显示:除金刚桥、外环河桥与中心桥外,其余断面的TP与TFe和OM均具有良好的相关性(R2>0.85).      

洞庭湖表层沉积物中重金属污染特征、来源与生态风险

选择洞庭湖9个有代表性的样点,研究了洞庭湖表层沉积物中重金属的空间分布特征、主要来源与生态风险。结果表明,洞庭湖Cd、Hg、As、Cu、Pb、Cr的含量分别为0.60~20.70、0.090~0.640、10.4~83.7、17.9~70.9、16.9~95.8、59.0~199.0 mg/kg,Cd、As出现超过土壤环境质量三级标准的现象,是主要重金属污染物;Cd、Hg的空间分布相似,表现为南洞庭湖区西洞庭湖区东洞庭湖区;As、Cu、Pb、Cr的空间分布相似,表现为南洞庭湖区东洞庭湖区西洞庭湖区。相关分析结果显示:As、Cd、Hg、Cu、Pb之间呈显著正相关,Cr与其它重金属之间没有显著的相关性。主成分分析结果表明,第一主成分的Hg、As、Cd主要受工矿业采冶支配,第二主成分的Cr、Pb、Cu主要与生活污水排放和农业生产有关。沉积物质量基准法初步评价结果表明,洞庭湖Cd、Hg、As、Cu、Pb、Cr等重金属均具有引起较低生态风险的可能性,部分点位Cd、As、Cr具有引起较高生态风险的可能性。受Cd、As含量较高的影响,南洞庭湖区具有较高的生态风险。     

RECOVERY: A Contaminated Sediment-Water Interaction Model

This paper describes the U.S. Army Corps of Engineers screening-level water quality model (RECOVERY version 3.0) for assessing long-term impacts of contaminated bottom sediments on surface waters. The model couples contaminant interaction between the water column and the bottom sediment, as well as between contaminated and clean bottom sediments. The analysis is intended primarily for organic contaminants with the assumption that the overlying water column is well mixed vertically. The contaminant is assumed to follow linear, reversible, equilibrium sorption and first-order decay kinetics. The system is physically represented as a well-mixed water column (i.e., zero-dimensional) underlain by a vertically-stratified sediment column (i.e., one-dimensional). The sediment is well-mixed horizontally but segmented vertically into a well-mixed surface (active) layer and deep sediment. The deep sediment is segmented into variably contaminated and clean sediment regions. Processes incorporated in the model are sorption, decay, volatilization, burial, resuspension, settling, bioturbation, and pore-water diffusion. The solution couples contaminant mass balance in the water column and in the mixed sediment layer along with diffusion in the deep sediment layers. The model was verified against laboratory and field data, as well as against an analytical solution for the water and mixed sediment layers. These comparisons indicate that the model can be used as an assessment tool for evaluating remediation alternatives for contaminated bottom sediments.     

Phosphorus fractions and adsorption characteristics of floodplain sediments in the lower reaches of the Hanjiang River, China

The phosphorus fractions and adsorption characteristics of seven floodplain sediment samples collected in the lower reaches of China’s Hanjiang River were studied. Most phosphorus fractions showed a marked downstream increase in response to point-source inputs from urban areas. Total phosphorus (TP) contents in the sediments ranged from 603.68 to 945.25 mg.kg⁻¹. Inorganic phosphorus (IP) was the major component of TP, and calcium-bound phosphorus (Ca–P) was the major fraction of IP. The distribution characteristics of the phosphorus contents were affected by sediment grain size and hydrodynamic conditions. The maximum phosphorus adsorption capacities (Q _max) and the half-saturation concentration (k) were obtained using an improved Langmuir model. Native adsorbed exchangeable phosphorus content (w _NAP) and the zero-equilibrium phosphorus concentration value (c _EPC0) were subsequently calculated. The effects of sediment grain size, temperature, and disturbance on the phosphorus adsorption isotherms were also studied. The results showed that phosphorus adsorption on floodplain sediments was primarily chemisorption; the particle concentration effect played a more important role at a disturbance intensity of 150 r.min⁻¹ (on a shaker table) than at 100 r.min⁻¹.     

海洋沉积物中多种重金属的X射线荧光分析法

建立了海洋沉积物中包括砷、铜、铅、锌、镍和总铬在内的多种重金属X射线荧光分析法,测量不需要任何消解前处理过程,可在约1h内测量1个样品中的50余种元素,用该方法分析了8个海洋沉积物标准样品,还与原子荧光光谱法或原子吸收分光光度法比对分析了2个实际样品,结果表明,该方法可信度较高,且具有快速、简便、高效等特点,是一种非破坏性分析方法。     

合肥市南淝河不同排口表层沉积物磷形态分布特征

对合肥市南淝河不同排口处表层沉积物进行了采样,并采用修正后的标准测试程序SMT和钼锑抗紫外分光光度法测定了其中的总磷(TP)、无机磷(IP)、有机磷(OP)、铁/铝磷(Fe/Al-P)和钙磷(Ca-P),同时分析了各形态磷之间以及与沉积物有机质之间的相关性。结果表明,由于各排口附近不同的水动力条件,污染状况以及沉积环境,各排口表层沉积物总磷(TP)的质量分数存在显著差异,其值在771.23~3 065.36 mg/kg之间,除二里河排口(S15)沉积物磷以钙磷(CaP)为主外,其他采样点表层沉积物磷均以铁/铝磷(Fe/Al-P)为主,各形态P的最低值均在位于南淝河上游的S4点,TP、IP、Fe/Al-P的最大值均出现在位于望塘污水厂排口下游60 m处的S6点,潜在释放磷比例最大值在南淝河上游受农业面源污染影响较大的S3点。沉积物各形态磷之间存在着不同程度的相关性,各形态磷与有机质存在着显著的正相关。以上结果表明,南淝河沉积物磷形态分布特征受排口类型影响显著,其中城市污水处理厂尾水可能是受纳水体沉积物重要的磷源。     

巢湖入湖河流沉积物中有机磷的形态分级研究

为识别巢湖流域污染物的特征、来源及其沉积物有机磷各形态分布与富营养化的关系,测定了7条巢湖入湖河流沉积物中有机磷各形态的含量,分析不同污染类型人湖河流沉积物中有机磷各形态分布的差异及与其他因素间的相关性。研究发现,不同污染类型人湖河流沉积物中水土保持控制型河流沉积物中有机磷各组分的相对含量顺序为残渣态Po〉富里酸-Po〉HCl-Po〉胡敏酸-Po〉NaHCO3-Po,平均的相对比例为7．5：3．1：1．9：1．5：1．0,而城市污染控制型和面源污染控制型河流沉积物中有机磷各组分的相对含量顺序恰好相同,面源污染控制型河流沉积物Po各形态含量低于城市污染控制型和水土保持控制型河流。中活性P。和OM、TP、Pi、Po、TN、NaHCO3-Pi、NaOH—Pi呈正相关,非活性Po与Po、NaOH-Pi呈显著正相关关系,反映了中活性Po很容易转化为生物可利用磷和非活性Po,且非活性Po仍然具有潜在的生物活性。