沉积物中重金属铅的释放动力学模拟

采用扩散通量模型(DIFS)模拟了沉积物中Pb从固相向液相释放的动力学过程.模拟结果表明,对于扩散梯度膜(DGT)测定的Pb浓度CDGT与孔隙水Pb浓度比值(R)接近1的S1样品,靠近DGT的液相Pb被消耗后,固相吸附态Pb迅速补给消耗;其解吸速率常数k-1较大,而且非稳态Pb含量较大,在放置时间(t)内,DGT表面孔隙水Pb浓度一直维持在初始浓度.而对于R接近0的S2样品(无补给情况),靠近DGT孔隙水Pb被消耗后,固相的补给很少,反映在相关参数上便是非稳态Pb含量较低,而且解吸速率常数k-1很小,DGT表面处孔隙水Pb浓度随放置时间的增加而降低.对于R值等于0.39的S3样品(部分补给情况),非稳态Pb含量和解吸速率常数k-1介于S1和S2样品之间,固相的补给能力介于S1和S2之间.由以上模拟结果可知,沉积物中重金属释放动力学过程受到非稳态Pb含量和释放动力学参数共同影响.     

聚丙烯酸钠为结合相的梯度扩散薄膜技术预测甘蔗田土壤中镉的生物有效性

DGT技术一直以固态结合相原位采集和测量水体、土壤或沉积物中有效态重金属,液态结合相的DGT主要应用于现场水体中金属离子的检测.本研究分别采用固态结合相梯度扩散薄膜(chelex100-DGT)装置和改进的液态结合相梯度薄膜扩散(CDM-PAAS-DGT)装置,对广西甘蔗田土壤中有效态Cd进行了测定.结果表明,2种装置提取的土壤有效态Cd含量与甘蔗(根、茎、叶)体内Cd含量都呈极显著正相关,改进的CDM-PAAS-DGT装置对土壤中有效态Cd的提取能力更强;融合土壤pH、阳离子交换量(CEC)、有机质(OM%)和土壤颗粒组成等理化指标影响,运用多元统计分析,提取出2种主成分因子,建立了多元回归模型.液态结合相DGT技术能较好地预测甘蔗田土壤中Cd的生物有效性,拓展了其应用范围.     

不同方法测定沉积物中生物可利用性磷对铜绿微囊藻生长量的影响

采用梯度扩散薄膜(DGT)技术,以太湖9个采样点所采集的27个沉积物柱样为研究对象,研究沉积物中DGT所测量的磷浓度(DGT-P)与铜绿微囊藻生长量之间的关系,同时与4种常规的生物可利用性磷方法[(水溶性磷(WSP)、易解析磷(RDP)、藻可利用磷(AAP)和NaHCO3提取磷(Olsen-P))]进行比较,评价不同提取方法获得的太湖沉积物生物可利用性磷与铜绿微囊藻生长量的关系.结果表明,DGT-P与藻生长量的相关系数为R2=0.941(P<0.01),高于4种生物可利用性磷提取法的相关系数(WSP,0.780、RDP,0.806、AAP,0.849、Olsen-P,0.910).结果表明DGT技术可以作为预测原位沉积物磷的生物可利用性的工具.     

DGT和传统化学法比较研究复合污染土壤中Cd的生物有效性

以小麦和玉米2种陆生植物为金属吸收材料,利用盆栽试验比较研究了新型DGT(diffusive gradients in thin films,薄膜扩散梯度技术)法与5种传统化学法评价土壤中Zn复合存在下Cd的生物有效性. 结果显示:①土壤中w(Cd)为4 mg/kg时明显抑制了2种植物的生长,与对照组相比,小麦的地上部和根系生物量分别降低了26.2%和23.4%,玉米的分别降低了23.5%和30.9%. ②Zn的添加能够减轻Cd对植物的毒害,并促进植物生长;Cd污染土壤中Zn的复合存在会抑制2种植物对Cd的吸收,并随w(Zn)的增加其抑制作用更加明显;DGT法、土壤溶液法测定的土壤溶液中ρ(Cd)和4种化学提取法(HAc、EDTA、CaCl₂和NaAc)测定的土壤中w(有效态Cd)均随w(Zn)的增加而明显降低. ③Pearson相关分析显示,2种植物体内w(Cd)与6种方法表征的土壤中w(有效态Cd)均呈显著正相关(R>0.900,P<0.01),但植物体内w(Cd)与DGT和土壤溶液法测定的土壤溶液中ρ(Cd)的R(>0.940)大于其他4种化学提取法. 可见,对于评价Cd-Zn复合污染土壤中Cd的生物有效性而言,DGT与土壤溶液法均优于传统的化学提取法.      

DGT和CaCl2提取下冶炼场地及周边土壤Cd固液分配特征

通过梯度扩散薄膜(DGT)和CaCl₂等提取方法,研究了典型冶炼场地及周边多种类型土壤中Cd有效态含量和固液分配特征,并构建回归预测模型. 结果表明: 场地渣土混合土壤、林地表层和深层土壤中Cd有效态含量较高,DGT提取结果分别为23.2, 1.90和2.53μg/kg,农田深层土壤、杂填土和素填土较低,分别为0.03, 0.05和0.03μg/kg. 土壤Cd固液分配系数(K_d)在杂填土、素填土、渣土混合土壤中最高,黏土、农田土壤次之,全风化土和林地土壤最低. 总体上DGT测定的K_d值高于CaCl₂测定结果,CaCl₂土液比、提取液pH值显著影响K_d值结果(P<0.05). CaCl₂提取结果能够通过线性回归有效预测DGT测定的K_d (R²=0.89~0.93).     

湖泊沉积物孔隙水磷酸盐含量原位监测技术研究进展

传统的沉积物孔隙水磷酸盐含量测定方法通常是采用离心法获取沉积物柱芯孔隙水,然后再进行磷酸盐含量测定。这种常规测定方法不仅破坏了沉积物的原本物理化学结构,而且分样间距多为厘米级,无法满足沉积物-水界面磷酸盐的高分辨率分布特征研究和释放通量的高精度估算要求。为克服传统监测技术破坏系统原始状态和分辨率低的弊端,近年来沉积物孔隙水磷酸盐原位监测技术迅猛发展,较为成熟的有透析装置技术(Dialysis peepers)、薄膜扩散平衡技术(Diffusive equilibrium in thin-films technique,DET)和薄膜扩散梯度技术(Diffusive gradients in thin-films technique,DGT)等。本文综述了透析装置技术、薄膜扩散平衡技术和薄膜扩散梯度技术的基本原理和应用实例,对比分析了他们各自的优缺点和发展应用前景。DGT作为一种新型、廉价的原位被动采样技术,具有原位和高分辨率监测的优点,被广泛应用于水体、沉积物和土壤等研究,在获取沉积物孔隙水磷酸盐含量及时空分布特征等方面优势突出。如何延长DGT胶体的使用寿命、提高监测的空间分辨率和实现多元素同步监测是其主要发展方向。大量研究表明,沉积物内源磷释放与沉积物中Fe-S的耦合循环存在密切联系,深入了解湖泊沉积物P-Fe-S的耦合生物地球化学循环过程是揭示湖泊内源磷释放机制的一把钥匙。快速发展的薄膜扩散梯度(DGT)技术及其与DET技术联用无疑为P-Fe-S耦合循环研究提供了有效手段,亟待在不同类型湖泊中应用和完善,为深刻揭示P-Fe-S耦合循环过程与机制提供独特信息。     

柘林湾海水养殖区底泥中重金属生物有效性及生态风险评价

采集柘林湾海水养殖区8个位点表层沉积物样品,考察了沉积物样品中重金属含量、生物有效性和形态分布,并分别利用基于总量的Hakanson指数法和基于形态的风险评价指数(RAC)评价了沉积物中重金属的生态危害风险.结果表明,柘林湾海水养殖区大部分位点沉积物中重金属含量符合海洋沉积物质量Ⅰ类标准限值,少数位点Zn和Pb含量超过Ⅰ类限值但低于Ⅱ类限值.沉积物中重金属的薄膜扩散梯度技术(DGT)测定浓度(C_(DGT))与间隙水中的浓度(C_(IW))对重金属生物可利用性评估状况基本一致,Zn、Ni和Pb生物可利用性较高.沉积物中Cr、Ni、Zn和Cu以残渣态为主,Cd和Pb以弱酸提取态为主.柘林湾沉积物中重金属总体存在轻度到中度生态危害风险,Cd和Pb生态危害风险较高.沉积物中Cr、Ni、Zn、Cu和Cd的C_(DGT)与其弱酸提取态含量明显正相关,重金属弱酸提取态能较好反映其生物可利用性.     

硝酸钙添加和锆改性膨润土覆盖联用控制底泥中磷释放的效果及机制

通过底泥培养实验,研究了硝酸钙添加和锆改性膨润土覆盖联用控制底泥中磷释放的效果及机制.结果发现,在缺氧条件下,底泥中磷会先释放出来进入间隙水中,而后穿越底泥-水界面扩散进入上覆水中,导致上覆水中溶解态活性磷（SRP）和薄膜扩散梯度（DGT）有效态磷浓度较高.但是,联合使用硝酸钙添加和锆改性膨润土覆盖可有效控制底泥中磷释放出来进入上覆水中,导致上覆水中SRP和DGT有效态磷浓度处于很低的水平.此外,该组合技术还可有效降低底泥中间隙水SRP和DGT有效态磷浓度以及最上层底泥中氧化还原敏感态磷（BD-P）含量,这对于其控制水体内源磷释放会起到至关重要的作用.与单一的硝酸钙添加技术相比,组合技术对上覆水中SRP的去除效果较优,对底泥间隙水中SRP及底泥-水界面SRP扩散速率的削减效果较佳,对最上层底泥中BD-P的削减率也较高.与单一的锆改性膨润土覆盖相比,组合技术在底泥修复后期对上覆水中SRP的削减效果较佳.另外,组合技术对底泥中间隙水SRP和DGT有效态磷的削减率要高于单一的锆改性膨润土覆盖技术,前者对底泥-水界面SRP扩散速率以及表观磷扩散速率的削减效果也好于后者.硝酸钙添加/锆改性膨润土覆盖组合是一种很有希望的水体内源磷释放控制技术.     

Investigation of potential interferences on the measurement of dissolved reactive phosphate using zirconium oxide-based DGT technique

A diffusive gradients in thin films (DGT) technique based on hydrous zirconium oxide (Zr-oxide) has been recently developed for the measurement of dissolved reactive phosphate (DRP). In this study, the detailed performance of the DGT technique is reported. Spiking experiments revealed that several orthophosphate monoester compounds contributed to the Zr-oxide DGT measurements of DRP. However, such a phenomenon is unlikely to occur during field conditions due to the low concentration of organic P in typical natural waters. The presence of Cl- (up to 106 g/L), SO42- (up to 16 g/L), HCO3- (up to 817 g/L), and AsO2- and AsO 3 4 (both up to 1 mg As/L) in solutions had negligible effects on the measurement of DRP. The threshold concentrations of Cl-, SO42- and HCO3- have been increased from previous reports for the measurements of DRP using other adsorbent-based DGT techniques. The capacity for DGT measurements of DRP decreased with increasing solution pH (4.2-9.2). The lowest capacity (95 μg P/m2 at pH 9.2) was still greater than that of other DGT techniques that are usually used for the measurement of DRP (2-12 μg P/cm2 ). The Zr-oxide binding gel could be stored for up to 2 years without any aging effect. This period of validity was considerably longer than the ferrihydrite binding gel that is commonly used in present DGT devices (6 months). The field application revealed that the concentrations of DRP measured in three fresh water samples using the Zr-oxide DGT technique were in agreement with those of the traditional colorimetric method.     

巢湖沉积物有效磷的原位高分辨分析研究

将两种原位被动采样技术——高分辨平衡式间隙水(HR-Peeper)与氧化锆薄膜梯度扩散技术(Zr-oxide DGT)相结合,分别对巢湖西半湖7个点位溶解态反应性磷(cPW)和有效磷(cDGT)进行原位测定分析,cPW和cDGT在大部分沉积物剖面的分布相似或局部相似,说明不同深度沉积物固相有效磷组分对间隙水SRP的缓冲能力较接近.利用界面扩散通量和cDGT/cPW比值(R)表征沉积物磷的活性,从巢湖湖心向南淝河入湖口方向,界面以下6 mm的cPW、cDGT和扩散通量的变化基本一致,均呈递增趋势,表明沉积物磷的污染水平在增加;R值变化较小,说明沉积物界面处的缓冲能力差异不明显.     

Determining cadmium bioavailability in sediment profiles using diffusive gradients in thin films

Cadmium(Cd) uptake by plants or benthic organisms largely depends on its bioavailability in sediments,so it is necessary to understand Cd bio availability for determining its ecological risks in riverine sediments.Pore water is easily disturbed during sample collection,indicating that there was a shortage of traditional methods for investigating Cd bio availability.Here,sediment cores were collected from rivers,after which sequential extraction and diffusive gradients in thin films(DGT) method were employed to determine Cd potential bio availability in the sediments and pore water.We found that Cd concentrations measured by DGT were lower than that in pore water profiles,and Cd distribution in various fractions changed remarkably.Pearson correlation analysis showed significant positive correlations between Cd concentrations measured by DGT and total Cd concentrations(r~2=0.76),exchangeable and weak acid soluble fraction(r~2=0.68),ferromanganese fraction(r~2=0.72) and bound organic matter or oxidizable fraction(r~2=0.54).However,the correlation was relatively low between Cd concentrations measured by DGT and that in pore water profiles(r~2=0.26).These results demonstrated that DGT method could provide more accurate information of Cd bio availability in sediment profiles than traditional methods.     

薄膜扩散梯度技术测量砷的影响因素及其应用

研究了水体中常见无机阴离子和腐植酸对以氧化锆为固定膜的新型薄膜扩散梯度技术(Zr-oxide DGT)测量砷(As)的影响及其在自然地表水体中的应用.结果表明,短期(16h)暴露,SO₄^2-无影响,而HCO₃^-、Cl^-、SiO₃^2-和腐植酸有一定的影响,其忍耐的最高浓度值分别为360mg/L、45g/L、100mg/L和36mg/L.1~4d暴露期间,37~148mg/L的HCO₃^-、1.44~2.88g/L的SO₄^2-、12~24g/L 的Cl^-、8~24mg/L的SiO₃^2-和3~9mg/L的腐植酸均无影响,而高浓度的HCO₃^-(370mg/L)、SO₄^2- (8.64g/L)、Cl^-(72g/L)和腐植酸(27mg/L) 3~4d以及SiO₃^2-(72mg/L) 2~4d的存在明显降低该技术对As的吸收富集,并对As(III)的作用更大.将Zr-oxide DGT技术应用于南京市地表水体,并与传统的主动监测方法进行比较,发现利用Zr-oxide DGT技术测得的溶解态As浓度与传统的主动采样技术测定浓度一致.     

Mobility and sulfidization of heavy metals in sediments of a shallow eutrophic lake, Lake Taihu, China

The technique of DGT (diffusive gradients in thin films) using three diffusive gel thicknesses was applied to estimate the mobility and bioavailability of heavy metals in sediments and porewater of Lake Taihu, China. The DGT results showed significantly positive correlations between Co, Pb, Cd and Mn, and Ni and Fe concentrations in porewater. Cu and Zn showed a significantly negative correlation with Mn, due to Cu combination with carbonates and Zn derived from agricultural pollution, respectively. The rank order of average concentrations of Co, Ni and Cd at each station was DGT_1.92 >DGT_0.78 >DGT_0.39, suggesting stronger resupply from sediments to porewater when using thicker diffusive gels. Comparing centrifugation and DGT measurements, Co, Ni and Cd are highly labile; Mn and Fe are moderately labile; and Cu, Zn and Pb are slightly labile. The variations of AVS concentrations in sediment cores indicate that metal sulfides in deeper layers are easily diffused into surface sediments.     

Mobility and sulfidization of heavy metals in sediments of a shallow eutrophic lake,Lake Taihu,China

The technique of DGT (diffusive gradients in thin films) using three diffusive gel thicknesses was applied to estimate the mobility and bioavailability of heavy metals in sediments and porewater of Lake Taihu, China. The DGT results showed significantly positive correlations between Co, Pb, Cd and Mn, and Ni and Fe concentrations in porewater. Cu and Zn showed a significantly negative correlation with Mn, due to Cu combination with carbonates and Zn derived from agricultural pollution, respectively. The rank order of average concentrations of Co, Ni and Cd at each station was DGT_1.92 > DGT_0.78 > DGT_0.39, suggesting stronger resupply from sediments to porewater when using thicker diffusive gels. Comparing centrifugation and DGT measurements, Co, Ni and Cd are highly labile; Mn and Fe are moderately labile; and Cu, Zn and Pb are slightly labile. The variations of AVS concentrations in sediment cores indicate that metal sulfides in deeper layers are easily diffused into surface sediments.     

黑臭河流沉积物磷、铁、硫的DGT同步分析研究

沉积物中磷(P)、铁(Fe)、硫(S)之间存在密切的耦合关系,但大部分研究并未提供直接的原位证据,需要借助高分辨的获取技术才能表征.为了探索三者之间的耦合关系,本文利用Zr O-Ag I DGT和Chelex DGT对东莞市黑臭河流沉积物中有效态P、Fe、S进行了高分辨分析.结果表明:应用DGT技术能够获得黑臭河流沉积物中有效态P、Fe、S的高分辨率浓度分布,并且实验结果可靠,有效地避免了主动采样方法和沉积物空间异质性对P、Fe、S同步分析的影响.各采样点沉积物中有效态P、S在垂向上的空间分布趋势基本相似,部分采样点出现有效态P、Fe、S同步变化的现象,同步获得的微界面浓度分布较好地反映了三者的耦合关系.对P、Fe、S在水-沉积物界面附近的含量分布进行相关性分析,结果表明三者之间具有显著正相关(p0.05),进一步证实了黑臭河流沉积物中也存在P、Fe、S同步释放的现象.大部分样点沉积物-水界面有效态P、Fe、S的扩散通量为正值,表现为由沉积物向上覆水释放P、Fe、S.沉积物中P、Fe、S的耦合释放表明其对黑臭的形成和内源磷释放至关重要.     

Mobility and sulfidization of heavy metals in sediments of a shallow eutrophic lake, Lake Taihu, China

The technique of DGT (diffusive gradients in thin films) using three diffusive gel thicknesses was applied to estimate the mobility and bioavailability of heavy metals in sediments and porewater of Lake Taihu, China. The DGT results showed significantly positive correlations between Co, Pb, Cd and Mn, and Ni and Fe concentrations in porewater. Cu and Zn showed a significantly negative correlation with Mn, due to Cu combination with carbonates and Zn derived from agricultural pollution, respectively. The rank order of average concentrations of Co, Ni and Cd at each station was DGT_1.92 > DGT_0.78 > DGT_0.39, suggesting stronger resupply from sediments to porewater when using thicker diffusive gels. Comparing centrifugation and DGT measurements, Co, Ni and Cd are highly labile; Mn and Fe are moderately labile; and Cu, Zn and Pb are slightly labile. The variations of AVS concentrations in sediment cores indicate that metal sulfides in deeper layers are easily diffused into surface sediments.     

大辽河水系表层沉积物中重金属的迁移特征及生物有效性研究

为了研究大辽河水系表层沉积物中重金属的迁移特征和生物有效性,采集了9个表层沉积物样品,测定了沉积物的理化性质、重金属Cu、Pb、Zn和Ni的总量及化学形态,并利用DGT方法和离心方法测定了沉积物孔隙水中Cu、Pb、Zn和Ni的浓度.结果表明,沉积物中Cu、Pb、Zn和Ni的总含量分别为16.8～49.2、 12.9～55.8、 38.7～152.8和18.1～39.0 mg/kg;DGT测定的孔隙水中重金属的浓度c(DGT)与离心方法测定的孔隙水中重金属浓度的比值低于0.5,表明沉积物中重金属从固相到液相的再补给能力和生物有效性比较低.相关分析表明,碳酸盐结合态Cu对DGT测定的Cu的浓度c(DGT)的贡献较大(r=0.633,p<0.05);对于Pb,可交换态含量对c(DGT)的贡献较大（r=0.617,p<0.05）;而对于Ni,可交换态、锰氧化物结合态、有机质结合态和铁氧化物结合态对c(DGT)浓度的贡献都比较大(r>0.650,p<0.05).此外,pH也是影响重金属元素从固相到液相的释放重要因素.