华中地区水旱轮作酸性土磷、铁形态转化及机理

为探讨华中地区水旱轮作体系酸性土壤磷与铁的形态转化以及磷生物有效性变化,本研究于2018年和2019年水稻收获后采集该区域典型酸性红壤（低磷铁比）和黄棕壤（高磷铁比）,采用张守敬-杰克逊无机磷分级方法和梯度扩散薄膜（DGT）技术,对干湿交替培养样品磷形态、生物有效性磷（DGT-P）与铁（DGT-Fe）、Fe（Ⅱ）及无定形氧化铁（Fe_ox）等进行定量分析。结果表明：淹水过程中黄棕壤和红壤pH逐渐升高趋于中性;二者氧化还原电势（Eh）在淹水期间降低,土壤环境呈明显的还原条件。淹水过程黄棕壤和红壤中Fe²⁺与Fe_ox均增加,干燥后均明显降低。黄棕壤与红壤磷形态以铁结合态磷（Fe-P）与闭蓄态磷（Oc-P）为主,干湿交替过程中黄棕壤Oc-P向Fe-P转化,红壤Fe-P向Oc-P转化。在水-土界面以下120 mm土壤垂直剖面内,黄棕壤DGT-P和DGT-Fe释放水平先增加后减少;红壤DGT-Fe增加,DGT-P减少,黄棕壤P和Fe的同步释放相关性更显著。研究表明,干湿交替条件下酸性土壤磷形态主要是Fe-P与Oc-P之间转化,低P/Fe红壤以磷闭蓄化为主,高P/Fe黄棕壤Fe-P增加,以铁吸附磷为主;淹水导致DGT-P含量增加,生物有效性增加;干燥过程磷闭蓄化加深,但磷有效性并无明显降低,这与土壤磷水平有关。     

Monitoring of subaqueous depots with active barrier systems for contaminated dredged material using dialysis samplers and DGT probes

Background, Aims and Scope  Disposal of dredged material in subaqueous depots is increasingly considered an economic and ecologically sound option in managing contaminated dredged material. The concept of subaqueous disposals capped with active barrier systems has been developed to minimize this risk of contaminant release. As such a depot represents a permanent installation within a sensitive ecosystem, it requires a thorough monitoring concept. It is the goal of this work to develop such a concept regarding general considerations and results of laboratory and field investigations. Methods  In addition to the state-of-the-art techniques developed for other under-water constructions, this monitoring concept is developed with particular respect to the chemical isolation of the dredged material from the overlying water body. It comprises the use of seepage meters, dialysis samplers, and DGT gel probes for determining the migration of selected target solutes. The capability of the dialysis samplers is demonstrated by comparing field results with model calculations. The appropriateness of DGT probes to assess the impact of humic substances on trace metal speciation and on copper toxicity is demonstrated with the aid of laboratory experiments. Results and Discussion  The experimental results show that, by using dialysis samplers, the temporal changes in concentration-depth-profiles of heavy metals in the pore solution can be monitored. Additionally, the application of DGT probes facilitates the in situ detection of labile species of a metal in the presence of dissolved humic substances, which serves to reflect its toxicity. Conclusions. Three subsequent monitoring phases are distinguished on the basis of both general considerations and the findings from field results: A hydraulic phase that is characterized by compaction and pore water expulsion, a geochemical phase in which the demobilization of pollutants can occur due to substantial changes in the physico-chemical conditions (pH, EH), and a steady-state-phase where pore water flow and geochemical conditions are approaching their minimum. Recommendations and Outlook  The monitoring concept suggested here provides a versatile tool to assess the chemical isolation of subaqueous sediment depots and other contaminated sediment sites. This is of great importance as subaqueous disposal is increasingly considered a future management strategy as space for upland disposal is limited and treatment, in general, proves to be too costly.     

太湖梅梁湾沉积物中的重金属生物可利用性及生态风险评价

[目的]研究太湖梅梁湾沉积物中重金属的污染状况和生态风险。[方法]对重金属总量和生物有效浓度进行了分析,采用发光细菌法进行了沉积物毒性研究,并对重金属环境风险进行了评价。[结果]梅梁湾沉积物中Cr处于无污染状态,Zn、Cu、Pb和Ni属于轻度污染水平。DGT测定的有效态浓度和释放通量结果表明,Ni、Zn和Cu的生物可利用性高于Cd和Pb。发光细菌毒性测试和Hakanson潜在生态风险指数评价也表明,梅梁湾沉积物不具有生物毒性,属于低生态风险。[结论]需对梅梁湾沉积物中的Ni污染进行控制。     

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.     

Changes in tolerance of soil microbial communities in Zn and Cd contaminated soils

Trace metals are present in the soil matrix in different forms, and this obscures the relationship between the amounts of metals, their biological availability and effects. Chemical methods have been devised to directly measure the biological available pools of trace metals, but such methods need to be validated against measured exposure of organisms in the soil. We studied acquired Zn- and Cd tolerance of the soil microbial community as a reporter of its exposure, and compared it with chemical determination of Zn and Cd in 10 soils differing in pH, organic matter content, texture, vegetation-/cultivation history and metal contamination. The tolerance was measured as LC₅₀ (i.e. the metal concentration which inhibits 50% of the activity) in suspensions of extracted soil bacteria, by measuring the incorporation rate of [³H] thymidine at different metal concentrations. Chemical determination of Cd and Zn in soils included total concentrations by aqua regia extractions (AR), and total concentrations in extracted pore water (PW). In addition was the ‘effective concentration’ (C_E) determined using the Diffusion Gradients in Thins films method (DGT). The LC₅₀ values correlated better with PW (r²=0.90 for Cd and r²=0.97 for Zn) and C_E (0.90 for Cd and 0.98 for Zn) compared to the correlation with AR (0.72 for Cd and 0.82 for Zn). After excluding a single extremely contaminated soil from the analysis, the correlation of LC₅₀ with AR was much poorer (r²=0.03 (ns) for Cd and r²=0.48 for Zn), whereas correlations remained significant for both PW (0.90 for Cd and 0.87 for Zn) and C_E (0.54 for Cd and 0.84 for Zn). In conclusion, PW fraction of Cd and Zn appear to be the best predictor of trace metal exposure of the soil microorganisms.     

沉积物中重金属铜的解吸动力学模拟

采用DIFS模型模拟了DGT在沉积物中放置过程中,吸附态铜从固相解吸的动力学过程。结果表明,对于模拟的三个样品,R值均小于1,均属于部分补给情况(固相的补给不能使DGT界面处孔隙水浓度维持在初始水平)。对于R值为0.74的M1样品,Kd值较高,解吸速率常数k-1较大,在DGT放置时间T内,吸附态铜可以迅速解吸并补给DGT的消耗,DGT界面处孔隙水Cu浓度基本维持在一个稳定的值,但低于初始浓度,吸附态铜的消耗范围较小(<0.15 cm);对于M2和M3样品,R值、Kd和k-1均小于M1,固相的补给很小,DGT界面处孔隙水浓度随着放置时间的增加而降低,且吸附态铜的消耗范围也较大。由模拟结果可知,沉积物中重金属释放动力学过程受到生物有效态铜的容量和解吸动力学参数共同影响。对于稳定状态部分补给的情况(M1样品),典型特征是较高的Kd和适中的k-1;而对于非稳定态部分补给的情况(M2和M3样品),典型特征是较低的Kd值和适中或者较高的k-1。     

Changes in Cd and Cr fluxes during the bioremediation of phenanthrene

Abstract. Different types of contaminants such as polycyclic aromatic hydrocarbons (PAHs) and metals coexist in different chemical forms in soil. Although bioremediation of organics has been widely studied, little attention has been paid to changes in metal behaviour during the bioremediation process. In this study, the diffusion gradient in thin-film (DGT) technique was used to assess changes in potentially bioavailable Cd and Cr fluxes in soil during the bioremediation of phenanthrene. Fluxes of Cd were low (< 0.2pgcm⁻² s⁻¹) and increased to 0.4–0.9 pg cm⁻² s⁻¹, while Cr(III) fluxes showed an approximately tenfold increase. Results showed that there was increased mobilization of metals associated with the fungal reduction of phenanthrene concentrations by Penicillium frequentans.     

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.     

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.     

薄膜扩散梯度技术评价土壤砷生物有效性研究

【目的】探讨薄膜扩散梯度技术（Diffusive Gradients in Thin Films Technique, DGT）在表征土壤砷生物有效性方面的准确性与优势,为正确评价土壤砷污染风险提供新技术。【方法】采用盆栽试验研究DGT方法测定土壤砷有效浓度（CE）、土壤孔隙水中砷含量、NaHCO3提取态砷含量、NH4Cl提取态砷含量及土壤总砷含量与油菜体内吸收砷量之间的关系,并初步尝试利用DGT测定结果和DIFS（DGT Induced Fluxes in Sediments and Soils）模型对土壤中砷的迁移过程进行模拟。【结果】DGT测定土壤砷有效浓度（CE）与植物吸收砷量之间均存在极显著相关关系,决定系数（R2）为0.990,DIFS模型模拟结果表明砷生物有效性高的土壤,具有较高的解析速率（kb）和较短的特征响应时间（Tc）。【结论】 DGT能较准确地表征土壤砷生物有效性,并可根据DIFS模型计算出土壤中砷迁移动力学参数,有助于进一步阐释土壤中砷的生物有效性。