基于梯度薄膜扩散技术的广西环江流域桑田土壤中铅的生物有效性研究

梯度薄膜扩散技术（Diffusive gradients in thin-films,DGT）是一种原位连续环境采样和测量方法,自20世纪90年代中期被报道以来,一直以固态结合相采集和测量水体、沉积物和土壤中有效态重金属,目前液态结合相的DGT多应用于水体中金属离子的检测。分别采用固态结合相（chelex100）和改进的液态结合相（sodium polyacrylate,PAAS）的DGT装置,对广西桑田土壤中有效态Pb进行了累积和测定。简单分析结果表明,两种装置提取的土壤有效态Pb含量与桑树老叶和嫩叶中的Pb含量都呈极显著相关关系,改进的PAAS-DGT装置对土壤中有效态Pb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,建立了逐步回归模型。多元统计分析表明,两种结合相的DGT技术所构建的回归模型是可靠的,其调整判定系数R2adj分别为0.87、0.89、0.96和0.95,且预测结果融合了影响土壤有效态Pb含量的pH、CEC、有机质和土壤质地等主要因素。研究结果表明两种结合相的DGT装置均能较好预测桑田土壤中Pb的生物有效性,拓展了DGT技术的应用范围。关键词：梯度扩散薄膜技术（DGT）;聚丙烯酸钠（PAAS）;铅（Pb）;生物有效性;桑田;广西     

不同磷酸盐对污染土壤中镉生物有效性的影响

采用盆栽试验,在镉二级和三级污染的红壤和褐土上添加不同磷酸盐（磷酸二氢铵、磷酸二氢钾、磷酸二氢钙）后种植小油菜40d,测定植株生物量、镉吸收量、土壤有效态镉含量、pH值,分析不同磷酸盐对污染土壤中镉生物有效性的影响。结果表明,3种磷酸盐使污染红壤和褐土上小油菜生物量分别提高了18.7%～291.1%和31.5%～991.2%,在红壤上提高顺序为磷酸二氢钙〉磷酸二氢钾〉磷酸二氢铵,而在褐土上则表现为磷酸二氢钙≈磷酸二氢钾〉磷酸二氢铵。3种磷酸盐影响下小油菜吸收镉量,在镉二级污染水平的红壤上表现为显著提高8.3%～60.6%,而在镉三级污染水平的红壤上则表现为显著降低了4.6%～58.4%。污染红壤有效态镉含量在加入3种磷酸盐后提高了17.0%～122.7%,提高顺序为磷酸二氢钙〉磷酸二氢钾〉磷酸二氢铵;而磷酸二氢铵使污染褐土有效态镉含量降低了2.4%～13.4%。3种磷酸盐使红壤pH值提高了0.24～0.99。可见,不同土壤类型、不同镉污染水平下,3种磷酸盐对土壤镉的生物有效性的影响存在差异,其机制有待进一步研究。     

秸秆还田对镉污染农田土壤中镉生物有效性的影响

通过温室盆栽试验和土壤培养试验,研究了重金属镉污染水稻土和人为模拟镉污染土壤上不同种类和不同量的作物秸秆还田后,土壤中可提取态镉的动态变化规律以及对白菜生长和吸收重金属镉的影响。结果表明,秸秆还田显著提高了2种镉污染土壤的pH值。镉污染水稻土上还田玉米和菜豆秸秆显著提高了土壤中醋酸铵提取态镉和DTPA提取态镉含量,秸秆还田后2周时醋酸铵提取态镉含量增加了17%~33%,随时间延长,土壤中可提取态镉增加变的不明显。模拟镉污染土壤上还田玉米和菜豆秸秆对土壤中醋酸铵提取态镉和DTPA提取态镉含量影响不明显。镉污染水稻土上秸秆还田量2%时显著降低了白菜体内镉含量,还田菜豆秸秆和玉米秸秆白菜体内镉含量分别降低了18%和27%。还田玉米秸秆影响了白菜生长,降低了白菜的产量;模拟镉污染土壤上还田菜豆秸秆对白菜生长和镉含量影响不明显,但还田2%玉米秸秆降低了白菜生物量,增加了白菜镉含量。     

品种和土壤对水稻镉吸收的影响及镉生物有效性预测模型研究进展

稻田受重金属镉(Cd)污染后,土壤中的Cd可能被植物吸收通过食物链进入人体,威胁人类健康。而水稻品种和土壤类型对Cd吸收和积累有着深远的影响,因此在进行Cd的农产品安全阈值制定和人体健康风险评价时,需考虑土壤Cd的生物有效性和不同水稻品种对Cd吸收的影响。本文综述了水稻品种和土壤类型对Cd吸收和积累的影响,并重点介绍了目前常用于预测重金属生物有效性的模型,以期为环境风险评价、土壤环境质量标准及农产品安全阈值制定提供有效的工具,并为生产安全(无公害)稻米提供参考。     

菜地土壤铅、镉有效态与生物有效性研究

通过野外采样、室内测试分析,探讨重庆市北碚区菜地土壤铅、镉的有效态含量及生物有效性。结果表明：研究区菜地土壤铅、镉有效态平均含量为3.114,0.051mg/kg,生物有效性系数分别为7.7%,25.1%;小白菜可食部分铅、镉平均含量分别为0.123,0.021mg/kg,富集系数分别为0.4%,9.8%;从富集系数和生物有效性系数看,研究区菜地土壤镉的潜在生态风险要大于铅的。研究区菜地土壤理化性质中pH对有效态镉有显著影响;砂粒、粘粒和有机质对有效态铅含量有显著影响;铅、镉有效态与全量变化一致,全量是有效态含量的主要影响因素;土壤类型对铅、镉有效态含量有影响;在人类活动中交通对有效态铅含量有影响,肥料的施用对有效态镉含量有影响。菜地土壤中铅、镉有效态含量与小白菜可食部分铅、镉的含量相关性优于全量的,用土壤中铅、镉的有效态表征铅、镉的生态风险更准确。     

薄膜扩散梯度技术测定水体中砷及其影响因素研究

薄膜扩散梯度技术（Diffusive Gradientsin Thin Films Technique,DGT）是近年来应用于水体、沉积物和土壤中的铜镉等重金属生物有效性研究的一种新技术。采用标准溶液培养方法研究了以氧化铁作为吸附剂的DGT测定水环境中无机砷含量的可行性,并探讨了待测介质的pH和As价态对DGT测定结果的影响。结果表明,研究所用DGT装置中的吸附凝胶对砷吸附的最大容量≤42μg,其有效容量≤13μg,为确保DGT测定值的准确性,需要对DGT装置的放置时间加以控制;当水体中砷浓度为0.1～11.0mg·L-1时,DGT测定的溶液中无机砷浓度与直接用HG-AFS测定待测水体中无机砷浓度之间有较好的响应关系,DGT测定水体中无机砷的浓度能较好反应水体中无机砷的真实浓度;当溶液的pH值为2.95～8.18时,不同pH下吸附凝胶对砷的吸附量间差异不显著,溶液pH值在一定范围不影响DGT的测定结果;As（V）、As（Ⅲ）在进行DGT试验时不存在竞争吸附关系,砷离子的价态对DGT测定水体中的无机砷的浓度没有显著影响。总之,在各种环境相关的条件下,DGT是一种可以用于测定水体中总无机砷的有效方法。     

镉在水稻根际的生物有效性

综合介绍了水稻根际土壤中的ｐＨ值、Ｅｈ值、有机质和微生物、其它金属元素及根分泌物等因素同隔的生物有效性之间的关系。提出水稻根系具有泌能力,使其根际微环境呈氧化状态。因而,溶液中一些还原性物质被氧化,如Ｆｅ＾２＋、Ｍｎ＾２＋形成的氧化物在根表沉积成胶膜。胶膜及其根际环境对水稻吸收镉都有一定的影响。     

有机物料对土壤中外源镉形态与生物有效性的影响研究

盆栽试验研究稻草与紫云英对土壤中外源Cd形态及其生物有效性的影响结果表明 ,添加稻草与紫云英可降低水稻分蘖期潮土和红壤交换态镉含量 ,且二者在不同土壤的影响不同。 2种有机物料在水稻分蘖期固定作用并不稳定 ,随时间的推移 ,氧化锰结合态和紧有机质结合态吸附的镉将随紧有机质的分解和活性锰的还原被释放出来 ,并向交换态镉转化 ,提高Cd的生物有效性。水稻对外源Cd吸收与Cd在土壤中形态密切相关 ,水稻分蘖期稻草与紫云英均可抑制水稻根和茎叶对外源Cd的吸收 ,至成熟期水稻根、茎叶和糙米中Cd含量迅速增加 ,其根本原因是由于土壤中交换态镉含量提高和紧有机质结合态镉含量降低所致     

生物炭对复合污染土壤—作物中镉砷累积和转运的影响

针对镉砷复合污染土壤中小麦籽粒重金属积累问题,采用生物模拟方法,以镉砷复合污染区土壤为研究对象,探究杏核生物炭(C1和C2分别表示3%和6%生物炭添加量)对复合污染土壤—小麦/玉米系统中镉砷累积和转运的影响。结果表明：添加生物炭(C1、C2)显著降低了小麦季根际/非根际土壤Cd、As有效性,并且小麦籽粒中Cd、As含量分别比CK平均降低19.25%和50.70%,但前者差异不显著。对玉米而言,生物炭C1、C2处理显著降低穗中Cd和As含量,降幅分别为85.67%,61.28%和98.36%,96.48%;此外,施用生物炭显著降低了小麦—玉米体系中镉砷的转运和累积,但对小麦镉由秸秆向籽粒转运及籽粒中镉累积的影响未达显著水平。总之,添加3%生物炭可降低小麦籽粒和玉米穗中镉、砷含量,且对玉米穗中重金属镉、砷降低效果更明显,综合分析生物炭对镉、砷在复合污染石灰性土壤—小麦/玉米体系中迁移和累积的阻控效应,推荐施用3%生物炭为宜。     

关于土壤-作物生态系统中镉的研究

系统地介绍了国际上有关土壤-作物生态系统中镉的含量、形态、分布及其对生物危害等方面的研究成果。     

氧化节杆菌生物降解苯并芘

A pot experiment was conducted with multi-metal (Pb, Cd, Cu, and Zn) contaminated acidic soil to investigate changes in available metal burden resulting from the application of industrial wastes (fly ash and steel slag). The efficiency of amendments-induced metal stabilization was evaluated by diffusive gradients in thin films (DGT), sequential extraction, and plant uptake. The stability of remediation was assessed by an acidification test and by chemical equilibrium modeling. Addition of fly ash (20 g kg-1 ) and steel slag (3 g kg-1 ) resulted in similar increase in soil pH. Both amendments significantly decreased the concentrations of metals measured with DGT (C DGT) and the metal uptake by Oryza sativa L. Significant correlations were found between C DGT and the concentration of a combination of metal fractions (exchangeable, bound to carbonates, and bound to Fe/Mn oxides), unraveling the labile species that participate in the flux of metal resupply. The capability of metal resupply, as reflected by the R (ratio of C DGT to pore water metal concentration) values, significantly decreased in the amended soils. The C DGT correlated well with the plant uptake, suggesting that DGT is a good indicator for bioavailability. Acidification raised the extractable metal concentration in amended soil but the concentration did not return to the pre-amendment level. Equilibrium modeling indicated that the soil amendments induced the precipitation of several Fe, Al and Ca minerals, which may play a positive role in metal stabilization. Chemical stabilization with alkaline amendments could be an effective and stable soil remediation strategy for attenuating metal bioavailability and reducing plant metal uptake.     

梯度扩散薄膜技术（DGT）的理论及其在环境中的应用I：工作原理、特性与在土壤中的应用

根据文献资料,详细阐述了梯度扩散薄膜技术（DGT）的原理、影响DGT技术测量的因素和它的应用特性,同时回顾了DGT技术问世以来在土壤中的应用实例,并认为DGT技术为研究土壤重金属的生物可利用性提供了可行可靠而又有效的方法。     

Soil Organic Matter Impacts upon Fluxes of Cadmium in Soils Measured using Diffusive Gradients in Thin Films

Abstract

Classical analytical methods limit understanding of the dynamics of geochemical processes in soils. The technique of diffusive gradients in thin films (DGT) allows the quantification of the mobilization fluxes of traces metals in soils and more specifically the metal supply from the soil's solid phase. Diffusive gradients in thin films, measuring fluxes from soil solids to solutions, were reported in three different cadmium (Cd)–contaminated soils with different levels of soil organic matter (SOM). The soil solution concentration ratio between the labile Cd, determined using differential pulse anodic stripping voltammetry, and the total Cd obtained by inductively coupled plasma–atomic emission spectrometry was compared. The data suggest that SOM affected the complexation of Cd in the soil solution, and the values obtained by DGT also demonstrated that the sorption of the Cd to the solid phase was also affected. The fluxes of Cd into the DGT were decreased when organic matter was added to the soils but were also decreased when SOM was reduced using hydrogen peroxide (H₂O₂).     

Wheat yield prediction by zero sink and equilibrium-type soil phosphorus tests

Diffusive gradients in thin films (DGT) measurements have been shown to outperform other phosphorus (P) tests in soils with strong P sorption, but this has not been confirmed for moderately weathered European soils. We compared the performance of DGT in predicting wheat grain yield in Swedish long-term fertility experiments with those of standard intensity (water-extractable P (P-H₂O)) and quantity (ammonium lactate-extractable P (P-AL)) tests. A Mitscherlich-type model was used to fit wheat yield response to P application rates (0, 15, 30 or 35, and 45 kg P ha^-1 year^-1) in each individual trial replicate to estimate the maximum yield. For trials with clear plateau-type yield responses and the goodness of fit (R²) > 0.75, relative yields (RYs) were calculated for each P treatment and plotted against the soil P test results (n=143). The goodness of the Mitscherlich-type fits decreased in the following order:DGT-measured P (P-DGT) (R²=0.35) > P-H₂O (R²=0.18) > P-AL (R²=0.13). When excluding soils with P-AL:P-DGT ≥ 0.1 L g^-1, R² was considerably improved to 0.55 for P-AL, 0.46 for P-H₂O, and 0.65 for P-DGT (n=61). At 95% of maximum yield, the upper limit of P deficiency for P-DGT was 44.8 (the soils with P-AL:P-DGT < 0.1 L g^-1) and 61.9 μg L^-1 (all soils), falling within the range reported for other European and Australian soils (6.0-142 μg L^-1). We show that in the investigated Swedish soils, DGT performed better than the quantity and intensity tests, which is attributed to its ability to capture P diffusion and resupply from the soil solid phase, similar to plant roots in the rhizosphere.     

天津农田土壤镉和汞污染及有效态提取剂筛选

采集天津3条排污河污灌区重金属污染农田的22个土壤及油麦菜样品,测定镉（Cd）和汞（Hg）的浓度,筛选两种重金属生物有效性的最佳提取剂,并分析了混合提取剂（M3）及DTPA对两种重金属生物有效性的预测能力。结果表明,22个土壤采样点中有9个样点Cd超标,7个样点Hg超标,60%以上的油麦菜受到Cd的污染,但大部分处于轻污染级别,且M3、DTPA都能够很好地表征油麦菜中Cd的生物有效性,相关系数分别为：RM3=0.92（P〈0.0001）,RDTPA=0.88（P〈0.0001）,其中M3预测能力强,提取用时短,可推广应用;100%的油麦菜都受到Hg污染,且都处于重污染级别,油麦菜中Hg与M3、DTPA提取结果具有显著负相关,相关系数分别为：RM3=-0.82（P〈0.0001）,RDTPA=-0.47（P〈0.05）,这可能是因为可提取态Hg的增加对植物吸收产生负面影响。     

The role of sediment-feeding oligochaeteTubifex on the availability of trace metals in sediment pore waters as determined by diffusive gradients in thin films (DGT)

Background  Available fractions of metal concentrations in sediment pore water are difficult to measure without disturbing the sediment core. The available fraction is an important parameter in understanding the risks for benthic organisms. Not much is known about the influence of the presence of benthic organisms to the available fraction. Objectives  The aim of this study was to discuss the dynamics of metal behaviour in natural sediments and the influence of the presence ofTubifex on sediment chemistry using DGT. Methods. DGT-probes were added to six beakers to cover a depth profile of 0 to 13 cm. The six beakers contained three different sediments. For each sediment, one beaker had 1 g ofTubifex added, the other beaker contained noTubifex. After two weeks of exposure, the probes were withdrawn and strips were analysed for their content of cadmium, copper and zinc. Results and discussion  Available concentrations were higher in the upper layer (0–1 cm) of the sediment core, where conditions are generally more oxic. The presence ofTubifex worms led to a decrease of the available concentrations in the upper layer, due to the competition of the worms with the DGT for the available metal fraction. On the other hand, the presence of the worms led, via bioturbation, to an increased oxygen penetration depth in the sediment, and, as a consequence, to an increase of the available fraction in the next-higher sediment layer. Conclusions  In sediment cores without organisms, very steep gradients of the available metal concentration in pore water have been found. The change from a high to low amount of available fraction corresponds to the change from oxidised conditions in the surficial sediment layer to reduced conditions in the lower sediment layers. The tunnelling behaviour ofTubifex worms leads to a penetration of oxygen to deeper sediment layers, and to an increase of the available metal fraction in the pore water.Tubifex competes with DGT for the available fraction, resulting in lower metal amounts accumulated in the DGT probe. Competition is the prevailing effect in the top 1 cm layer of all sediments. In the second 1 cm layer, competition, in most cases, is not strong enough to compensate the increase in metal availability due to the broadening of the oxidised zone. Recommendations  The effects of sediment organisms on the deepening of the oxidised layer and on the availability of metals in pore water need further investigations and quantification. DGT is recommended as an instrument for measuring available metal concentrations in these studies.     

干旱区绿洲土壤Cd／Pb复合污染下重金属形态转化与生物有效性

采用盆栽试验及连续浸提形态分级方法,研究了Cd和Pb在土壤中的形态分布规律及其对油菜的生物有效性的影响。结果表明,当土壤受外源Cd/Pb污染后,重金属的形态分布特征发生了变化,以可交换态（EXC）响应最大,Cd、Pb的赋存形态分别以碳酸盐结合态（CAB）、铁锰氧化态（FMO）和碳酸盐结合态（CAB）为主;一定浓度范围内的Cd/Pb复合胁迫能促进油菜的生长,油菜根系和茎叶的Cd、Pb含量均随着Cd/Pb复合胁迫水平的升高而持续增加。茎叶中的Cd含量远远高于根系,Pb含量反之。油菜可将更多的Cd从根系转移至茎叶,而将更多的Pb滞留在根系中;对油菜根系吸收Cd最重要的形态为可交换态（EXC）和碳酸盐结合态（CAB）,而对茎叶吸收Cd以及油菜吸收Pb贡献最大的则为碳酸盐结合态（CAB）。     

利用薄膜扩散梯度技术研究不同土壤性质影响下镉对黑麦草的生物有效性

A generally accepted method for predicting the bioavailability and transfer of cadmium (Cd) from soil to plants has not yet been established. In this study, the diffusive gradients in thin films (DGT) and conventional extraction methods for metal fractions were used to investigate how effective these methods were at predicting Cd bioavailability to ryegrass (Lolium perenne) and to assess whether these holistic variables were independent of the soil property variables. The influences of soil properties on the predictive capabilities of the different methods were evaluated using multivariate statistics. The Cd concentrations in the shoots and roots of ryegrass correlated more closely with the effective Cd concentration measured by DGT (C_E), compared with those with soil total Cd, pore water Cd, and ethylenediaminetetraacetic acid disodium salt (Na₂EDTA)- and acetic acid (HOAc)-extractable Cd. When soil properties were included in a stepwise multiple linear regression, Cd transfer to L. perenne was negatively influenced by pH and positively influenced by organic matter (OM). The multivariate statistics showed that the adjusted correlation coefficients for the plots involving soil total Cd, pore water Cd, and Na₂EDTA- and HOAc-extractable Cd had been significantly improved after considering the influences of soil properties, which suggested that these methods were pH and OM dependent. For C_E, the relationship was pH independent or only dependent in strongly acidic soils. These results suggested that the main soil factors affecting bioavailability had the lowest impact on the DGT technique. Therefore, the DGT technique provided significant advantages over conventional methods when assessing Cd bioavailability.