Evaluation of the Bioavailability of Metals in Sediment from the Southern Coastal Wetland of the Qiantang Estuary by Using Diffusive Gradients in Thin Films Technique

Metal pollution has become an major issue governing the wetland ecosystem health.The southern coastal wetland of the Qiangtang Estuary are facing unusual perturbation due to rapid development along the embayment in recent decades.This study evaluated the bioavailability of metals(Cu,Pb,Cd,Cr and Zn)in the sediment of the southern coastal wetland of the Qiangtang Es-tuary using diffusive gradients in thin films(DGT)techniques and compared with several methods based on total metal content.The results showed that the contents of Cr,Pb,Cd and Cu in sediment,as detected using DGT,were considerably correlated with the exchangeable fraction and the content in Phragmites australis roots,while a weak correlation was observed for Zn.Therefore,DGT analysis could be used to evaluate the bioavailability and potential risk of Cr,Cd,Pb and Cu for P.australis.Quantitative indices,such as DGT concentration,bioaccumulation in P.australis,geoaccumulation index(Igeo)and potential ecological risk index(RI),revealed that Cd was a major potential ecological risk factor along the southern coast wetland of the Qiantang Estuary,especially in the upstream region,which is potentially more vulnerable to the anthropogenic pollution.

Determination of Ni^(2+) in Waters with Sodium Polyacrylate as a Binding Phase in Diffusive Gradients in Thin-films

An aqueous solution containing sodium polyacrylate（PAAS） was used in diffusive gradient in thin-films technique（DGT） to measure DGT-labile Ni2＋ concentrations.The DGT devices（PAAS DGT） were validated in four types of solutions,including synthetic river water containing metal ions with complexing EDTA or that without complexing EDTA,natural river water（Ling River,Jinzhou,China） spiked with Ni2＋,and an industrial wastewater （Jinzhou,China）.Results show that only free metal ions were measured by PAAS DGT,recovery=97.36% in the solutions containing only free metal ions,recovery=49.62% in a solution with metal/EDTA molar ratio of 2：1 and recovery=0 in the solutions with metal/EDTA molar ratios of 1：1 and 1：2.These indicated that the complexes of Ni-EDTA were DGT-inert.The DGT performance in spiked river water（recovery=18.24%） and in industrial wastewater（recovery=12.25%） were investigated,which indicated that the measurement of metals by this DGT device did not include the humic substances complexed fractions of metals.The binding properties of PAAS DGT for Ni2＋ were investigated under different conditions of pH value and ionic strength.Conditional stability constants（lgK） of PAAS-Ni complexes were also evaluated.

Evaluation of Cadmium Bioavailability in Soils Using Diffusive Gradients in Thin Film Technique and Traditional Methods

The developed technique of diffusive gradients in thin film( DGT) has been suggested as a promising tool for evaluation of cadmium( Cd) availability in soils,but there exists considerable debate on its suitability. In this study,Cd bioavailability in soils was systemically investigated by comparing this technique with seven traditional methods, including soil solution concentration and six commonly used extraction methods( HAc,EDTA,Na c,NH4Ac,CaCl2 and MgCl2). Two typical plants( wheat and maize) were examined for Cd uptake. Maize was more sensitive to increasing exposure to Cd in soils than wheat when the added amounts of Cd ranged from 3. 5 to 5. 0 mg · kg-1,accompanied by the significant decreases of shoot and root biomasses. Cd concentrations in shoots and roots of two plants increased continuously with increasing levels of Cd in soils. Cd uptake was higher in wheat than that in maize. The bioavailable concentrations of Cd measured by all methods increased nearly linearly with increasing addition of Cd in soils. Positive correlations were observed between various bioavailable indicators of Cd in soils and Cd concentrations in two plants. The extractable Cd by six chemical extractants was considerably higher for maize than for wheat,while the DGT-measured and soil solution concentrations of Cd were lower for maize than for wheat,following the same trend as plant Cd uptake. The results imply that DGT measurement can effectively predict the bioavailable levels of Cd in soil solutions and that it is an ideal tool for prediction of Cd bioavailability in soils.

High-Resolution Profiles of Dissolved Reactive Phosphorus in the Porewaters of Lake Sediments Assessed by DGT Technique

The technique of DGT (diffusive gradients in thin films) was applied to obtain high-resolution vertical profiles of dissolved reactive phosphorus (DRP) in sediment porewater of Lake Chaohu, a shallow eutrophication lake. Three kinds of DGT probes (with three thicknesses of diffusive gel: 0.38 mm, 0.78 mm and 1.18 mm) measured vertical concentration and induced flux from solid to solution phase which had intricate variations with depth. The results indicated that higher concentrations and induced fluxes of DRP were achieved by using DGT probe with thicker diffusion layer (CDGT1.18 > CDGT0.78 > CDGT0.38) and relatively stable DRP concentration profiles using DGT probes with 0.78 mm diffusive gel were obtained in each sediment core. The DRP concentrations displayed a clear gradient from Core C1 to Core C3 in sediment porewaters due to different sources and exchange degrees of reactive phosphorus. Compared to the concentrations obtained by the centrifugation technique, the concentrations of DRP resulting from the DGT technique were higher because some dissolved reactive phosphorus compounds have always been neglected using conventional centrifugation method.

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.

Diffusive gradients in thin films using molecularly imprinted polymer binding gels for in situ measurements of antibiotics in urban wastewaters

Urban wastewater is one of main sources for the introduction of antibiotics into the environment.Monitoring the concentrations of antibiotics in wastewater is necessary for estimating the amount of antibiotics discharged into the environment through urban wastewater treatment systems.In this study,we report a novel diffusive gradient in thin films(DGT)method based on molecularly imprinted polymers(MIPs)for in situ measurement of two typical antibiotics,fluoroquinolones(FQs)and sulfonamides(SAs)in urban wastewater.MIPs show specific adsorption toward their templates and their structural analogs,resulting in the selective uptake of the two target antibiotics during MIP-DGT deployment.The uptake performance of the MIP-DGTs was evaluated in the laboratory and was relatively independent of solution pH(4.0-9.0),ionic strength(1-750 mmol/L),and dissolved organic matter(DOM,0-20 mg/L).MIP-DGT samplers were tested in the effluent of an urban wastewater treatment plant for field trials,where three SA(sulfamethoxazole,sulfapyridine,and trimethoprim)and one FQ(ofloxacin)antibiotics were detected,with concentrations ranging from 25.50 to 117.58 ng/L,which are consistent with the results measured by grab sampling.The total removal efficiency of the antibiotics was 80.1%by the treatment plant.This study demonstrates that MIP-DGT is an effective tool for in situ monitoring of trace antibiotics in complex urban wastewaters.

Diffusive gradients in thin films(DGT) probe for effectively sampling of per-and polyfluoroalkyl substances in waters and sediments

The passive sampling technique, diffusive gradients in thin films(DGT) has attracted increasing interests as an in-situ sampler for organic contaminants including per-and polyfluoroalkyl substances(PFAS). However, its effectiveness has been questioned because of the small effective sampling area(3.1 cm^(2)). In this study, we developed a DGT probe for rapid sampling of eight PFAS in waters and applied it to a water-sediment system. It has a much larger sampling area(27 cm^(2)) and as a result lower method quantification limits(0.15 –0.21 ng/L for one-day deployment and 0.02 – 0.03 ng/L for one-week deployment) and much higher(by > 10 factors) sampling rate(100 m L/day) compared to the standard DGT(piston configuration). The sampler could linearly accumulate PFAS from wastewater, was sensitive enough even for a 24 hr deployment with performance comparable to grab sampling(500m L). The DGT probe provided homogeneous sampling performance along the large exposure area. The use of the probe to investigate distributions of dissolved PFAS around the sediment-water interface was demonstrated. This work, for the first time, demonstrated that the DGT probe is a promising monitoring tool for trace levels of PFAS and a research tool for studying their distribution, migration, and fate in aquatic environments including the sediment-water interface.

悬浮扩散共聚法制备聚合物GRIN小球及对折射率梯度分布的控制

选用 MMA为单体 M1、 3 FEA为单体 M2 ,通过悬浮扩散共聚法制备了可见光透过率为 90 %的聚合物GRIN小球 .采用剪切干涉法测得小球内的折射率基本上呈抛物线型球对称梯度分布 ,折射率差Δn达到0 .0 1 9.

南四湖出湖口沉积物-水界面中营养盐分布特征分析及释放风险评估

为了解决南四湖出湖口沉积物-水界面中磷酸盐、氨氮和硝态氮等营养盐释放风险控制缺乏科学依据的问题,利用薄膜扩散梯度技术、高分辨率孔隙水采样技术分析南四湖出湖口沉积物-水界面中营养盐浓度的垂直剖面分布特征,并根据有效态磷、有效态氨氮和有效态硝态氮的浓度,计算三者的净扩散通量,评估三者的释放风险。结果表明:非泄洪期南四湖出湖口上覆水中的溶解态磷浓度低于孔隙水中的,表明沉积物孔隙水中的溶解态磷可能会因浓度梯度的存在而向上覆水中扩散;根据连续分级提取法,钙结合态磷是南四湖出湖口沉积物中磷元素的主要赋存形态,表层沉积物中的不稳定磷元素含量高于深层沉积物中的;有效态磷与有效态铁呈显著正相关,说明南四湖出湖口沉积物-水界面中有效态磷的释放受铁氧化物还原释放影响;有效态磷、有效态氨氮和有效态硝态氮的净扩散通量分别为17.58、1.16、-40.72 ng/(cm^(2)·d),说明有效态磷和有效态氨氮有从沉积物向上覆水中释放的潜在风险。

基于DGT和化学提取法研究浙西北地质高背景区土壤镉生物有效性

地质高背景区相较于人类活动引起的土壤镉污染影响范围更广,在区域尺度上对生态系统和人类健康构成危害。土壤镉生物有效性是决定其生物可利用性、生物毒性的关键因素,因此探寻可行的土壤镉生物有效性评价方法对污染农用地安全利用和风险管控具有重要的理论和实际意义。DGT技术、单一提取法、连续提取法和土壤溶液法常用于测定土壤有效镉,但已有研究成果主要基于同种土地利用类型土壤的室内盆栽实验,难以代表自然污染土壤中的复杂情况。为探明各土壤重金属有效态提取技术对地质高背景区不同土地利用类型土壤Cd生物有效性评估效果,本文以浙江西北部土壤Cd高地质背景区水田土壤-水稻籽实和旱地土壤-小白菜样品为研究对象,实验应用DGT技术、单一提取法(0.01mol/L氯化钙提取)、连续提取法(七步连续提取)和土壤溶液法评价土壤中镉生物有效性。结果显示:①研究区水田和旱地土壤Cd平均含量分别为1.07mg/kg和0.73mg/kg,显著高于浙江和全国土壤平均水平,Cd的异常富集主要与浙西北地区广泛分布的黑色岩系有关。②相较于碳酸盐岩区,黑色岩系区土壤中Cd的生物有效组分占比较高,水田和旱地土壤Cd的活动系数(MF)高达59.9%和51.8%,Cd易在土壤-作物系统中发生迁移富集;③植物体内镉含量Cd-P与不同方法测定的有效镉含量均呈显著正相关,但Cd-P与DGT技术测定的有效镉含量相关性优于其他三种方法,水田土壤测得的有效Cd与水稻籽实相关关系:C_(soln)>C_(DGT)>C_(Cacl_(2))>C_(F_(1)+F_(2)+F_(3)),旱地土壤测得的有效Cd与小白菜相关关系:CDGT>C_(Cacl_(2))>C_(F_(1)+F_(2)+F_(3))>C_(soln)。综合比较不同土壤有效Cd测定方法的优缺点,DGT技术可以模拟植物体对Cd的动态吸收过程,更能准确地反映土壤Cd生物有效性,预测作物Cd含量水平,这与已有研究成果一致。此外,本文研究成果表明DGT技术评价土壤Cd生物有效性,不仅适用于人为污染区,也可应用于地质高背景区。

沉积物-上覆水界面有效铁浓度对内源磷再移动的影响

铁磷耦合关系是控制沉积物磷再移动的主导机制,基于薄膜梯度扩散(DGT)技术测定的沉积物-上覆水界面RFeP(有效态铁磷摩尔浓度比)可反映内源磷再移动潜力.本文总结了有效铁和磷及IF(磷扩散通量)在沉积物-上覆水界面的区域分布差异,探讨了RFeP、沉积特征和外部环境条件对内源磷再移动的影响机制.结果表明:①有效铁和磷浓度变化范围分别为0.08~10.22和0.02~3.35 mg/L,淡水高于海水;有效铁浓度表现为南方高于北方,有效磷浓度呈相反趋势.②RFeP和IF的变化范围分别为0.09~132.38和0.56~903.67 ng/(cm^(2)·d);RFeP表现为淡水高于海水,平原高于高原;IF则表现为淡水高于海水,高原高于平原.③RFeP与IF成反比,沉积物磷的高污染负荷或水生动植物生理活动会影响判别沉积物内源磷再移动潜力阈值(RFeP=2)的准确性.④对于不同的水域类型,沉积物中Fe^(2+)氧化沉淀或铁氧化物还原溶解均是控制沉积物磷再移动的关键过程,扰动、水生植物、微生物等外部环境条件通过改变沉积特征间接影响磷的再移动.为加深对沉积物内源磷再移动机制的认识,未来研究可关注磷再移动过程的多驱动力耦合作用机制及磷的吸附沉积速率.

薄膜扩散梯度技术与紫外光谱法联合富集、检测rhEPO

以EPO抗体修饰的Fe_(3)O_(4)粉末-聚丙烯酰胺凝胶为结合相,明胶凝胶为扩散层,通过薄膜扩散梯度技术(DGT)与紫外光谱法,对去离子水、人体尿液中的rhEPO进行富集和检测的实验研究。在25℃、常压环境下,DGT中结合相的饱和富集容量为0.0758μg cm^(2),当pH值为5.5~8.0、无机盐浓度为0.3%~1.5%时,rhEPO的检测回收率基本不受影响。对质量浓度为6~15 ng mL的rhEPO水溶液进行检测时,rhEPO检测回收率的平均值为81.9%;对质量浓度为5~20 ng mL的rhEPO人体尿液进行检测时,rhEPO检测回收率的平均值为79.8%。

冰封期湖泊沉积物-水界面氮磷迁移及源汇特征

以查干湖为研究对象,基于原位-高分辨率被动采样技术(DGT),分析关键营养元素(N和P)亚毫米级空间分布规律及其源汇特征.结果表明,冰封期上覆水中有效态NH_(4)^(+)-N和NO_(3)^(-)-N浓度大于沉积物中浓度,而有效态P则呈现相反的趋势.在沉积物-水界面下有效态氮磷表现出不同的分布特征,NH_(4)^(+)-N和NO_(3)^(-)-N浓度随着沉积物深度的增加而逐渐减小,P浓度随着沉积物深度的增加呈先增大后减小的趋势.查干湖NH_(4)^(+)-N和NO_(3)^(-)-N交换通量均值分别-0.135,-0.333mg/(m^(2)·d),呈现“汇”的特征;而P交换通量均值为0.084mg/(m^(2)·d),呈现“源”的特征.冗余分析(RDA)表明,溶解氧解释了沉积物-水界面氮磷释放通量的32.8%(P<0.05).通过对上覆水贡献率估算发现沉积物中P营养盐扩散对上覆水影响较大,个别采样点达到2297%的贡献率,这可能是由于局部微高值点的存在.

湖泊底泥微生物燃料电池中磷形态分布及释放研究

针对沉积物中沉积磷(P)通过微生物活动再释放,致使湖泊富营养化反复的问题,采集郑州大学眉湖上覆水和沉积物,搭建一个沉积式微生物燃料电池(Sediment Microbial Fuel Cell,SMFC)系统,研究了通过SMFC限制沉积磷向上覆水体释放的方法。实验周期内监测SMFC的电压和阳极电极电位、上覆水温度pH、沉积物磷的Standards Measurements and Testing(SMT)法分级提取;并在实验开始与结束收集阳极微生物样进行微生物群落及基因分析;首次使用氧化锆薄膜扩散梯度技术(Zr-Oxide Diffusive Gradients in Thin-films,Zr-Oxide DGT)可视化了SMFC沉积物中不稳定磷亚毫米分辨率的浓度分布。结果表明:SMFC阳极电极电位从-100 mV升至230 mV;上覆水pH从7.15升至7.46;SMFC沉积物烧失量(Loss on Ignition,LOI)从18.31%±0.7%降至13.09%±1.10%,低于对照组的14.29%±2.10%;SMFC显著促进了孔隙水磷向沉积物磷的矿化过程,在沉积物垂向方向上,Na OH-P和HCl-P出现了明显的区域性增加;根据沉积物DGT磷的二维(2D)图像,SMFC使沉积物DGT磷的浓度最低降至初始值的66%;基于京都基因与基因组百科全书(Kyoto Encyclopedia of Genes and Genomes,KEGG)数据库的功能基因分析,SMFC使磷相关功能基因丰度显著增加。证明SMFC对于沉积物磷和水相磷分布有显著影响,通过基质竞争、提高阳极电位等方式减弱固相磷的溶解,促进水相磷向沉积相磷的转化,可用于富营养化水体原位底泥磷稳定化。该文深入研究了SMFC固磷作用机理,为修复水体内源磷污染提供了一种新思路。

纳米LDHs-DGT用于土壤环境无机砷提取检测技术研究

为有效测量土壤环境中的砷污染,本研究开发了一种基于纳米层状双金属氢氧化物(LDHs)为结合膜的梯度扩散薄膜设备(LDHs-DGT)。对设备的基本性能以及适用条件进行了探究,对不同水分管理下土壤As(Ⅲ)和As(Ⅴ)的动态变化进行监测,探究了不同水分管理下的不同深度砷的形态变化情况,实验结果表明,该技术能够在较宽的pH(4~8)和离子强度(CNaNO_(3)<0.7 mol·L^(-1))范围内对As(Ⅲ)和As(Ⅴ)进行有效的提取和检测,其中,LDHs结合膜对As(Ⅲ)和As(Ⅴ)的吸附容量分别为30μg·cm^(-2)和85μg·cm^(-2),结合膜在6 h内实现全解离;且LDHs-DGT具有较好的抗干扰特性,As(Ⅲ)和As(Ⅴ)在结合膜上没有明显的竞争吸附效应,对实际样品测定结果也能较好地反映DGT设备的实用性。综上所述,LDHs-DGT具有制备简单、适用范围广、检测效果好等特点,可为环境监测和评估提供新的解决方案。

基于薄膜扩散梯度技术对耕地土壤砷生物有效性评价及影响因素研究

通过采集耕地土壤样品及盆栽农作物(小白菜)试验,基于薄膜扩散梯度技术(DGT)研究了耕地土壤砷生物有效性。研究结果表明:通过回归分析比较传统Tessier法和DGT技术评价As生物有效性,两种方法测定耕地土壤As含量与农作物As含量都呈显著相关关系,但DGT技术相关性更高,能够更科学地反映出耕地土壤中As的生物有效性及耕地土壤的环境质量。温度为15~25℃时,As生物有效性随温度升高而升高,温度为25~30℃时,As生物有效性随温度升高略有降低。土壤pH与As生物有效性呈显著正相关关系,随着土壤pH的升高,土壤中As生物有效性增强,植物中As含量也随之增加。固化剂可以降低土壤As生物有效性,对降低土壤As污染具有一定作用。本研究进一步提升了对耕地土壤中As生物有效性的认识,可为耕地土壤As治理及农产品安全种植开发提供参考。

太湖梅梁湾沉积物中氮铁硫转化细菌的毫米级垂向分布及对氮磷迁移转化的潜在影响

本研究在太湖梅梁湾采集沉积柱,采用一种自制的毫米级柱状沉积物自动垂向分层切割装置对表层50 mm沉积物进行垂向切割(间隔2 mm),结合高通量测序技术分析沉积物中细菌群落的毫米级垂向分布;同时采用毫米级高分辨透析技术和薄膜扩散梯度技术(DGT)分析溶解态和DGT可获取态铵态氮(NH_(4)^(+)-N)、硝态氮(NO_(3)^(-)-N)、Fe、P的垂向分布特征。结果显示,沉积物中细菌群落与溶解态和DGT可获取态氮铁磷浓度在垂向上呈现显著的异质性。细菌硝酸盐还原主要发生在-16~0 mm沉积物深度,这可能导致了溶解态和DGT可获取态NO_(3)^(-)-N含量在该沉积物深度的明显减少。细菌铁还原主要分布在-32~-18 mm沉积物深度,细菌硫酸盐还原主要分布在-50~-34 mm的沉积物深度;细菌硫酸盐还原是导致沉积物溶解态和DGT可获取态铁磷浓度从-32 mm随沉积物的深度增加而显著增加的主要原因。本研究加深了对富营养化湖泊沉积物中细菌影响氮磷在垂向上迁移转化的认识。

生物炭对土壤和孔隙水性质以及Zn形态的影响

为了探究施用生物炭后土壤性质和重金属形态随时间变化过程,通过5种矿区土壤的玉米(Zea mays L.)盆栽实验,研究施用生物炭后土壤和孔隙水性质、梯度扩散薄膜(diffusive gradients in thin films,DGT)技术测定的Zn浓度(CDGT-Zn)和欧共体标准物质局共识(Bureau of Community right-to-know,BCR)有效态Zn含量(弱酸提取态Zn^(+)可还原态Zn,C_(BCR-Zn))随时间变化的过程。施用生物炭后,随土壤培养时间的增加,土壤阳离子交换量(cation exchange capacity,CEC)增加了20.35%~65.65%,孔隙水pH上升0.34~1.02个单位,溶解性有机碳(dissolved organic carbon,DOC)浓度CDOC先升后降,最终下降了8.21%~33.23%,孔隙水Zn浓度(C_(pw-Zn))下降了17.46%~49.67%,C_(DGT-Zn)、C_(BCR-Zn)分别下降了18.64%~50.00%、23.33%~64.71%。随玉米栽培时间的增加,土壤CEC增加了7.94%~28.97%,C_(DOC)、C_(pw-Zn)、C_(DGT-Zn)、C_(BCR-Zn)分别下降了10.43%~41.26%、9.62%~34.21%、10.42%~30.70%、14.68%~61.62%,孔隙水pH无明显变化。生物炭能明显改变土壤和孔隙水性质,降低Zn的生物有效性,从而降低土壤中过量Zn对玉米的危害。

基于LDHs-DGT的环境中活性态Cr原位提取检测方法研究

为原位监测土壤Cr的形态变化,本研究开发了一种以纳米Mg/Al双层氢氧化物(Mg/Al-LDHs)作为结合膜的梯度扩散薄膜(LDHs-DGT)装置,并通过ICP-MS和超痕量六价铬分析仪联用,实现对环境中活性态Cr含量及Cr(Ⅲ)、Cr(Ⅵ)的原位提取、测定。实验结果表明,该装置中LDHs结合膜对Cr(Ⅲ)和Cr(Ⅵ)均有较快的吸附速率,其最大吸附量分别是181.27μg·cm^(-2)和176.29μg·cm^(-2),该装置可在pH为5~8、离子强度小于50 mmol·L^(-1)的环境中对Cr(Ⅲ)和Cr(Ⅵ)实现准确提取,能够有效避免干扰离子对装置的影响,空白背景值为4.9 ng,方法检出限为0.22 ng·mL^(-1),Cr(Ⅲ)和Cr(Ⅵ)在扩散膜中的扩散系数分别为(3.58±0.02)×10^(-6)cm^(2)·s^(-1)和(7.03±0.09)×10^(-6)cm^(2)·s^(-1)。LDHs-DGT可以高效侦测土壤活性态Cr的时空变化态势,并能对Cr(Ⅲ)和Cr(Ⅵ)的价态变化进行动态监测。