Sedimentation and sediment core profile of heavy metals in the Owabi reservoir in Ghana

Tropical reservoirs are important for numerous socioeconomic and ecological reasons, including water supply, fishing and flood control. These functions are easily compromised, however, when reservoirs undergo accelerated sedimentation with increased inputs of chemical contaminants. The present study applied the concept of sediment core analysis to evaluate the sedimentation rate in Owabi Reservoir, which has served as a source of drinking water supply in Kumasi, Ghana, for nearly a century. The temporal variation of contamination from heavy metals was also assessed over this period. The sedimentation rate for Owabi Reservoir was estimated to be 6.82 mm/year, suggesting a relatively low rate of sedimentation, which is ecologically healthy in preventing a rapid loss of reservoir water volume. Heavy metal concentrations in the sediment cores taken from the reservoir reflected varying degree of contamination from the 1930s to 2010s. The concentration of iron (Fe) (1,560–1,770 mg/kg) was found to be the highest among the metals in the sediment core, while mercury (Hg) concentration (0.01–0.04 mg/kg) was the lowest. Lead (Pb) contamination peaked in the 1980s. Arsenic (As) and mercury (Hg) contamination exhibited more recent peaks in the 2000s, coinciding with recent widespread issues of artisanal and small‐scale gold mining (ASGM) in Ghana. Thus, even though ASGM activities are known to occur in remote districts, releases from such activities might eventually contaminate reservoirs designated as urban drinking water supplies.     

海河流域典型区域重金属沉积物生态风险研究

针对水库重金属污染及其生态效应问题,分析海河流域北部4座典型水库沉积物中6种重金属(As、Cr、Cu、Ni、Pb和Zn)的分布情况,并评价污染物类型的相关性。采用地累积指数法、潜在生态风险指数法和物种敏感性分布法分析4个水库沉积物中重金属的生态风险。结果表明：沙河水库、密云水库和于桥水库的重金属沉积物生态风险等级为优,官厅水库重金属沉积物生态风险等级为良。不同重金属对5%的底栖生物物种的危害质量分数(HC5)不同,由高到低依次为As(0.210 mg/kg)>Ni(0.071 mg/kg)>Cr(0.052 mg/kg)>Zn(0.050 mg/kg)>Cu(0.006 mg/kg)>Pb(0.005 mg/kg)。研究成果有助于了解水库沉积物中重金属的生态风险,为水库生态管理提供依据。     

高浊度河口颗粒态重金属对泥沙运动的指示作用

作者根据1994年6月长江口、杭州湾的水质调查资料，分析了这类高浊度河口颗粒态重金属的分布规律。研究表明，在长江口和杭州湾内，悬沙和表层沉积物中Cu、Pb、Cd分布特征相似，尤其在杭州湾中部水域，二者重金属含量呈趋同的态势。细颗粒泥沙是颗粒态重金属的主要载体。在高浊度河口，动力沉积过程为控制颗粒态重金属分布和输移的主要因子，颗粒态重金属的分布对泥沙运动具有指示作用，悬沙和表层沉积物中重金属元素的分布反映了长江口泥沙向杭州湾输移的事实。     

Assessment of sediment quality of a tropical lake using sediment quality standards

Sediments are often reservoirs of contaminants in aquatic waterbodies, and their quality can be an indicator of the health of their ecosystems. Heavy metal pollution in sediments is highly significant because of their persistent and bioaccumulative nature. In this regard, sediment quality guidelines (SQG) are useful for categorizing sediment quality with respect to the contaminant level in them. An attempt was made in this study to assess the sediment quality of the Akkulam‐Veli (AV) Lake system on the basis of guidelines that incorporate assessment scales that differ in their approaches. Some link threshold levels of heavy metal concentrations on the basis of their likelihood to cause adverse effects, while others classify the sediment concentration ranges that correspond to the degrees of toxicity caused by them. The sediment quality of the study area was assessed by combining the available guidelines to formulate two new approaches in this study. Based on this approach, AV Lake is highly polluted with respect to chromium (Cr), nickel (Ni) and lead (Pb), while arsenic (As) and cadmium (Cd) are non‐polluting with a negligible potential for adverse effects.     

Assessment of element distribution and heavy metal contamination in Chilika Lake sediments (India)

Chilika Lake is situated on the Indian east coast. It is one of the largest lagoons in the world, with a unique assemblage of marine, brackish water and freshwater species. Due to the opening of new connections to the sea in the years 2000 and 2008, an environmental change is expected in the lagoon. The study gives an assessment of sediment contamination by heavy metals on the verge of this change (sampling campaign in 2000). Sediment samples from two surface levels (0–5 and 30–35 cm), and from depth profiles, were analysed for mineralogical composition, main and trace element concentrations, and element bonding forms. Background concentrations from a depth profile were also examined. The profile spans a time of ≈13 500 years. Age determinations by radiocarbon dating and the ¹³⁷Cs- and ²¹⁰Pb-method were carried out. The composition of the surface sediments is generally uniform. The heavy metals exhibit slightly decreasing concentrations from NE to SW, thus indicating the supply of contaminants from the Mahanadi River. The anthropogenic portion of the heavy metal supply is mainly bound to Fe-oxide-hydroxides. Phosphorus is enriched in the sediments of the southern lake sector. Changes in element concentrations in the last 13 500 years have occurred mainly in two steps. The long-term variations exceed the anthropogenic changes caused by the Mahanadi River inputs. The very sensitive response of coastal area fabrics on climate changes also causes fast geogenic changes in element concentrations in sediments (similar grain sizes). This prevents the use of element concentrations from deep sediment horizons to define contaminations in those areas.     

洞庭湖流域沉积物重金属分布特征及其生态风险

以洞庭湖流域为研究对象,对比分析水体沉积物中7种重金属质量分数和分布特征,并对其来源和风险进行研究。结果显示:东洞庭湖中7种重金属质量分数在3个湖区中最高,入湖河流Cr、Pb质量分数在湘江较高,Ni、As、Cd质量分数在资水上游最高,Cu质量分数在资水下游最高,Zn质量分数在沅江下游最高,沉积物各元素空间分布差异大;地累积指数法显示,7种重金属污染情况排序依次为CdNiCrCuZnPbAs,东洞庭湖为湖区沉积物污染最严重区域,资水为入湖河流沉积物污染最严重区域,均达到严重污染程度;潜在生态风险指数法显示,单一元素污染危害程度依次为CdNiAsCuPbCrZn,全流域沉积物高风险因子Cd对生物影响最大,其在湖区中东洞庭湖最高,入湖河流中资水最高,流域整体处于高潜在生态风险水平;Pearson相关性分析和主成分分析显示,Cr、Ni、Cu、Pb和As可能属于自然来源,Zn可能来源于锌矿产的开采或矿产的岩石风化、侵蚀,而Cd可能来源于农药、化肥和生活污水,也可能来源于钢材制造、颜料、油漆等方面。     

珠江长州断面底泥重金属污染潜在生态危害评价

测定了珠江广州河段长州断面底泥中重金属镉、铬、铜、铅的质量比,采用Tessier形态分类法对它们在底泥中的存在形态进行了提取和测定。监测分析表明,该断面底泥中镉、铬、铜、铅质量浓度均高于全国湖泊底泥中的平均值。该断面底泥中镉、铬、铜、铅质量比分别为广东土壤背景值的49.50倍、3.62倍、14.24倍、5.51倍,底泥成为这些重金属的富集地。镉以可交换态为主,占总量的比例为47.47%;铬和铅以残渣态为主,占总量的比例分别为42.35%和47.28%;铜主要以有机态及硫化物结合态为主,占49.06%;残渣态较低,占18.26%。采用潜在生态危害指数法对该断面底泥中的镉、铬、铜、铅进行了潜在生态危害评价,结果表明:镉潜在生态危害强,铬、铜、铅的潜在生态危害轻微。     

武汉市湖泊中重金属污染状况

鉴于重金属元素的生理毒害作用,选择武汉市区、近郊、远郊六个代表性湖泊水体研究其水、沉积物、鱼样品中主要毒害重金属元素Hg,Cd,As,Pb,Cu,Cr,Ni,Zn的污染状况。采用原子荧光测试样品中Hg含量,其他元素用ICP-MS测试。结果表明:市区湖泊水、沉积物及鱼中重金属含量多数明显高于郊区湖泊,其中水及沉积物中重金属含量与研究区相应环境背景值对比有显著富集,但湖泊水中重金属含量大多可满足GB 3838—2002《地表水环境质量标准》Ⅲ类水质要求,鱼中重金属含量也可满足相应GB 2736—1994《淡水鱼卫生标准》。市区湖泊与郊区湖泊样品重金属污染程度对比而言,市区湖泊明显表现出受到一定人为污染影响。     

汤浦水库泥沙冲淤分布数值模拟

泥沙淤积不仅影响水库库容,其中大量污染物还会影响水库水质。运用MIKE21软件对汤浦水库泥沙分布进行模拟研究。结果表明:泥沙在库区分布不均,河流入库位置淤积较少,局部甚至有冲刷;库区中部是泥沙淤积主要地带,模拟最大淤积厚度约30 cm;坝前位置淤积最小,厚度约为12 cm。模拟结果与沉积物淤积厚度采样结果一致,说明该模型能合理模拟汤浦水库沉积物分布状况。模型提供的沉积物分布状况对控制汤浦水库内源污染有一定参考价值。     

不同水动力扰动下沉水植物对沉积物重金属释放的影响

在风浪扰动条件下,沉积物再悬浮会造成重金属的二次释放。沉水植物可以有效地改变水流条件并抑制颗粒物再悬浮,从而一定程度地改善水体的生态环境。该文通过室内环形风动水槽模拟实验,利用ADV测流技术与悬浮颗粒物(SPM)浓度表征悬浮量的方法,分析不同水动力条件下沉水植物苦草对水流条件的影响及再悬浮过程8 h内SPM的浓度变化,并测定试验周期(35天)内重金属(Ni、Cd)于上覆水、间隙水及沉积物中的分布情况,研究不同水动力下水生植物对重金属再悬浮的影响规律。结果表明,在风速分别为3.21 m/s(小风)、5.95 m/s(中风)和8.78 m/s(大风)时3种风力的扰动作用下,植物有效高度内流速低且流速梯度小,而冠层至水面高度内流速梯度较大,水流结构以植物冠层为拐点,呈"S"形分布。上覆水SPM浓度与无植物时相比显著降低,沉积物再悬浮率下降量(W)与风速(v)呈对数关系(W=0.2194ln(v)-0.2445)。不同水动力条件下,重金属(Ni、Cd)在上覆水、间隙水及沉积物中分布情况及变化规律相似。试验期间间隙水与沉积物中重金属含量变化整体呈现下降趋势,上覆水重金属含量上升。间隙水重金属释放量与风速呈对数关系,Ni、Cd释放量分别为39.55 ng(小风)/77.91 ng(中风)/110.04 ng(大风),以及1.10 ng(小风)/1.81 ng(中风)/2.80 ng(大风)。     

广州车陂涌底泥重金属污染及生态风险评价

合理处置重金属污染超标的底泥,是河道清淤工程的重点。以车陂涌清淤工程为例,通过原位测试、化学检验等,掌握河道清淤段不同位置底泥的污染特征。采用潜在生态危害指数法进行底泥污染潜在生态风险评价,得出河涌底泥低风险占31.71%、中等风险占29.27%、较高风险占2.44%、极高风险占36.59%,说明大多底泥需要处理。采用内梅罗综合污染指数法来评价底泥作为农用地土壤的适宜性,73.2%样点属于清洁,尚清洁、轻微污染各占9.8%,中度及严重污染共占7.2%,说明大部分底泥可用于农田。最后提出了该清淤工程应注意的问题,为车陂涌水环境治理提供科学依据。     

湖泊底泥中磷释放的随机动力学模型

本文从随机过程的观点出发，推导出湖泊底泥磷相对释放量概率密度函数的随机微分方程，并给出了相应的定解条件。利用隐式差分法进行求解，分析了磷释放的均方差系数(D)、吸附系数(K1)、解吸系数(K2)及其对磷相对释放量概率函数分布的影响情况。所建立的磷释放随机动力学模型计算结果与实验数据吻合良好。     

东湖沉积物中重金属垂向分布特征及污染评价

为了掌握武汉东湖的水环境状况,以沉积物为研究对象,使用电感耦合等离子体质谱仪(ICP-MS)测定了不同湖域沉积物柱状样中9种重金属(Cd、Zn、As、Cu、Co、Pb、Mn、Cr、Ni)含量,对重金属元素的垂向分布特征进行了研究,并采用地累积指数法对重金属的污染程度进行评价。结果表明:沉积物中9种重金属元素含量排序为MnCrPbZnNiCuCoAsCd;垂向分布特征为Cr、Ni的含量随沉积物深度增加而增加,Cu、As、Cd的含量随沉积物深度增加而减少。地累积指数评价表明,郭郑湖西岸污染最为严重,汤菱湖最轻,累积较为严重的是Cr、Mn、Cd和Pb,其中Cd和Pb达到中度污染程度。     

黄河干流主要重金属污染特征及其与流量关系

黄河流域重金属污染是水资源利用的一个制约因素。本文利用黄河干流站点1992~1998年实测监测数据,对黄河干流重金属污染变化特征进行初步分析,并分析这些变化与流量之间的内在关系。研究表明,黄河干流重金属在空间和时间上变化比较复杂,没有很明显的规律性。从与流量关系看,非汛期随着流量增加而增加,汛期反而减少。其原因与泥沙(重金属的载体)浓度变化一致。     

Assessment of heavy metals in sediments and aquatic organisms in West Lake (Ho Tay), Hanoi, Vietnam

West Lake (Ho Tay) is the largest freshlake in Hanoi, Vietnam. It has a surface area of ≈ 500 ha and a total volume of >10⁷ m³, and is 1–3.5 m in depth. West Lake has been classified as needing protection because of its valuable freshwater genetic resources. Noting that it has been extensively affected by pollution, the objective of the present study was to examine the extent of heavy metal contamination of the sediments and commercially important biota in the lake. Heavy metal concentrations in the sediment from most of 24 samples in West Lake exceeded the Ontario Ministry of Environment Screening Level for chromium (Cr), copper (Cu), manganese (Mn), lead (Pb) and zinc (Zn) concentrations. Aquatic organisms from the lake also were found to be contaminated by heavy metals. The average Zn concentrations in snails and mussels tissues ranged between 174 and 415 µg g⁻¹, and the Pb concentrations between 3.5 and 5.2 µg g⁻¹. The Cu concentration in shrimp (52 µg g⁻¹) and snail (189 µg g⁻¹), and the Pb concentration in all fish species and shrimp from the lake (2.0–5.2 µg g⁻¹) exceeded the Food Standard Australia‐New Zealand (FSANZ) health standards for human consumption. The Cd concentration in Cyprinus carpio also exceeded the FSANZ standard. The implications of these study findings for the effective management of the food and ecological resources of West Lake are discussed.     

利用水库泄空冲刷形成高含沙水流的机理

利用黄河干支流水库运用的实测资料,对高含沙水流的产生条件进行了研究。结果表明,水库水位的迅速下降并泄空,可使水库的淤泥流动并产生高含沙水流。水库淤土抗剪强度参数(C和Φ)依排水条件而异,抗剪强度一般不排水不固结的最小。水库淤积物在水下处于饱和状态,库水位迅速降低时,淤土中的孔隙水来不及排出,摩擦角值低,Φ=0,只要下滑的剪力大于黏着力淤泥便开始流动。当库区淤积物抗冲性较强时,溯源冲刷纵剖面调整又具有自动调整的特性,使冲刷以“局部跌坎”的形式向上游发展,使水流能量集中,加强冲刷能力,随着主槽冲深,滩槽差增大,促使淤土向主槽内滑塌,为高含沙水流形成创造了有利条件。     

粤北乐昌铅锌矿区水道底泥重金属污染评价

以粤北乐昌铅锌矿区水道（包括铅锌矿废水排泄沟、霜降河段及武江段）底泥为研究对象，通过野外采样和室内分析，分析了底泥中重金属含量，对其污染特征进行评价。结果表明：重金属在各采样点含量均超过清洁对照点；底泥重金属内梅罗综合污染指数范围是为2．25-60．5，平均为35，综合评价等级为Ⅳ级，属于重度污染。     

青狮潭水库底泥重金属污染特征及潜在生态风险

广西桂林青狮潭水库由东湖和西湖两部分组成,为了研究青狮潭水库底泥重金属污染分布特征及潜在生态风险,测定了青狮潭水库不同位置底泥中5种重金属(As,Cd,Cr,Hg,Pb)的含量,并通过地累积指数法和潜在生态风险指数法评价了重金属的污染程度和潜在生态风险。结果表明:东湖底泥中As和Cd含量较西湖高,西湖Hg和Pb含量高于东湖;底泥中Cr主要来源于成土母质,船只通行是造成Pb污染的主要原因;东湖底泥中As和Cd可能主要来源于东江上游煤矿开采;西湖底泥中As,Cd,Hg与营养元素间存在显著相关性,其来源可能与周边农业活动和前期水库内网箱养鱼有关;根据地累积指数,重金属污染强度排序为Cd,As,Pb,Hg,Cr,Cd和As为主要污染元素;重金属潜在生态风险大小排序为Cd,Hg,As,Pb,Cr;东湖底泥重金属潜在生态风险强于西湖。