多氯联苯复合污染土壤的微生物群落结构多样性变化

土壤微生物群落结构多样性是指示土壤生态系统稳定性及其功能的重要传感器。采用磷脂脂肪酸(Phospholipid fatty acids,PLFAs)方法,对长江三角洲地区某POPs高风险区PCBs长期复合污染土壤的微生物群落结构多样性进行了初步研究。结果表明,PCBs重度污染土壤中格兰氏阴性菌(16:1w9、cy17:0等)和厌氧微生物(18:1w7)的PLFAs组分含量较多,而格兰氏阳性菌(如i15:0、i17:0等)、放线菌(16:0(10Me))及真菌(18:2ω6,9)和好氧性微生物的PLFAs含量较低,表明PCBs污染土壤中微生物群落结构与组成发生了明显变化。这一结果为PCBs降解微生物资源的定向筛选提供了科学依据。     

Contaminant source apportionment by PIMMS lead isotope analysis and SEM-image analysis

By combining scanning electron microscopy (SEM) image analysis and laser ablation plasma ionisation multi-collector mass spectrometry (LA-PIMMS), high precision lead isotope analyses can be obtained from individual metal-rich particles. Soils from Wolverhampton and Nottingham were sampled on the basis of high Pb concentrations or brownfield location. Pressed powder pellets of each were rastered by LA-PIMMS to obtain a bulk Pb-isotope signature. The results plot along an apparent mixing line between the major sources of lead contamination in the UK, that is UK ore deposits and alkyl-lead from petrol additives (Australian ore). Two particularly lead-rich soils were chosen to investigate the lead distribution and isotope variability between size and density fractions. The fine-grained and low-density fractions contained most of the lead and have Pb-isotope ratios comparable with the bulk soils. By contrast, the small, lead-enriched denser fractions contained only a minor proportion of the total lead but Pb-isotope signatures indicating relative enrichment in one or other of the end-members from the mixing line. Further characterisation of individual Pb-rich grains is in progress.     

Elevated Levels of Cadmium and Zinc in Paddy Soils and Elevated Levels of Cadmium in Rice Grain Downstream of a Zinc Mineralized Area in Thailand: Implications for Public Health

Prolonged consumption of rice containing elevated cadmium (Cd) levels is a significant health issue particularly in subsistence communities that are dependent on rice produced on-farm. This situation is further exacerbated in areas of known non-ferrous mineralization adjacent to rice-based agricultural systems where the opportunity for contamination of rice and its eventual entry into the food chain is high. In the current study, an assessment of the degree of soil Cd and Zn contamination and associated rice grain Cd contamination downstream of an actively mined zone of Zn mineralization in western Thailand was undertaken. Total soil Cd and Zn concentrations in the rice-based agricultural system investigated ranged from 0.5 to 284 mg kg⁻¹ and 100 to 8036 mg kg⁻¹, respectively. Further, the results indicate that the contamination is associated with suspended sediment transported to fields via the irrigation supply. Consequently, the spatial distribution of Cd and Zn is directly related to a field’s proximity to primary outlets from in-field irrigation channels and inter-field irrigation flows with 60–100% of the Cd and Zn loading associated with the first three fields in irrigation sequence. Rice grain Cd concentrations in the 524 fields sampled, ranged from 0.05 to 7.7 mg kg⁻¹. Over 90% of the rice grain samples collected contained Cd at concentrations exceeding the Codex Committee on Food Additives and Contaminants (CCFAC) draft Maximum Permissible Level for rice grain of 0.2 mg Cd kg⁻¹. In addition, as a function of demographic group, estimated Weekly Intake (WI) values ranged from 20 to 82 μg Cd per kg Body. This poses a significant public health risk to local communities. The results of this study suggest that an irrigation sequence-based field classification technique in combination with strategic soil and rice grain sampling and the estimation of WI values via rice intake alone may be a useful decision support tool to rapidly evaluate potential public health risks in irrigated rice-based agricultural systems receiving Cd contaminated irrigation water. In addition, the proposed technique will facilitate the cost effective strategic targeting of detailed epidemiological studies thus focusing resources to specific ‘high risk’ areas.     

电压对电动修复Cr(Ⅵ)污染高岭土的影响研究

试验选用重铬酸钾作为污染物,配制高岭土中Cr(Ⅵ)初始质量分数为500mg·kg-1.试验研究了不同电压下的电动修复效率和单位能耗,并结合经济效益找出合适的电压范围.试验结果表明:当电压为20V时,去除效率达到89.9%,单位能耗仅为93.04KW·h·g-1.当电压再增大的时候,去除效率提高较小,单位能耗增大迅速,不符合经济效益的要求.由于适宜的施加电压和土壤本身性质有很大联系,如何通过简单的方法确定适宜的施加电压,还需进一步研究.     

Two‐Stage Agricultural Ditch Sediments Act as Phosphorus Sinks in West Michigan

Phosphorus (P) and sediment inputs from agricultural drainage contribute to the development of hypereutrophic conditions in lakes across the world. Two‐stage (2‐S) ditches, an agricultural best management practice gaining acceptance in the Midwestern United States, increase floodplain area within drainage ditches to help capture nutrients and sediment. While denitrification has been shown to increase on 2‐S benches, less is known about their P retention ability. This study assessed the abiotic and biotic P retention of two separate 2‐S ditches compared to their corresponding traditional reaches directly upstream within the Macatawa watershed, located in West Michigan. Soluble reactive P export was significantly reduced in 2‐S baseflow of both ditch systems. Equilibrium P concentration values suggest retention of P within the 2‐S sediment. P was bound within stable fractions in both 2‐S and traditional reaches. An analysis of P stock within the ditches revealed sediment held over 96% of total P (TP) within each reach compared to <4% in bench vegetation and periphyton combined. Turbidity, but not TP, was reduced in one study ditch, whereas TP, but not turbidity, was reduced in the other study ditch. Geomorphic stability may have been responsible for differing P retention between ditches. Ability to retain P appears to be impacted by physical as well as biogeochemical characteristics; hence, structure and age of 2‐S reaches influence P retention.     

Restoration of Riparian Buffer Function in Reclaimed Surface Mine Soils

Ecosystem processes such as water infiltration and denitrification largely determine how riparian buffers function to protect surface water quality. Reclaimed mine areas offer a unique opportunity to study the restoration of riparian function without the confounding influence of past land use. Between 1980 and 2000 in southern Illinois, agricultural fields with forest buffers were established along three restored stream reaches in reclaimed mine land. Our research objective was to compare common indicators of soil quality (infiltration, soil C and N, bulk density, and soil moisture) between forest and cultivated riparian zones to determine if riparian function was being restored. Soil bulk density was significantly lower in the forest buffers compared to the agricultural fields. The forest buffers had greater soil total C, total N, and moisture levels than agricultural fields likely due to greater organic matter inputs. Soil total C and N levels in forest buffers were positively related to age of restoration, indicating soil quality is gradually being restored in the buffers. Restoration success of riparian buffers should not be estimated by the return of structure alone; it also includes reestablishment of functions such as nutrient cycling and water retention that largely determine water quality benefits. Watershed planning efforts can expect a lag time on the order of decades between riparian restoration activities and surface water quality improvement.     

电子废物拆解区农业土壤中PCNs的污染水平、分布特征与来源解析

用GC-NCI-MS法测定了路桥农业表层土壤中46种多氯萘(PCNs)的含量.目的是了解该地区表层土壤中PCNs的污染水平、空间分布特征和来源.结果表明,所有表层土壤样品中ΣPCNs的含量为0.062～2.92 ng.g-1,平均值为0.630 ng.g-1.多数样品中tetra-CNs和penta-CNs是最主要的同族体,分别占18.4%～88.8%(平均值为46.7%)和8.40%～53.1%(平均值为30.7%),其次是tri-CNs,范围为0～47.3%,平均值为10.6%.聚类分析和燃烧指示物分析表明,采样点主要受Halowax1014和Halowax 1013工业品污染,PCBs工业品和电子废物燃烧也可能对污染有贡献.与国内外其它研究相比,研究区域内土壤中PCNs污染处于中等水平.     

Intraspecific differences in effects of co-contamination of cadmium and

A hydroponic experiment was carried out to study intraspecific differences in the effects of different concentrations of cadmium (Cd)(0-10 mg/L) and arsenate (As(V)) (0-8 mg/L) on the growth parameters and accumulation of Cd and As in six wheat varieties Jing-9428, Duokang-1, Jingdong-11, Jing-411, Jingdong-8 and Zhongmai-8. The endpoints of wheat seedlings, including seed germination,biomass, root length and shoot height, decreased with increasing the Cd and As concentrations. Significant differences in seed germination, biomass, root length, shoot height and the accumulation of Cd and As were observed between the treatments and among the varieties (p ＜ 0.05). The lethal dosage 50% were about 20, 80, 60, 60, 80 and 20 mg As/L for Jing-9428, Duokang-1, Jingdong-11,Jing-411, Jingdong-8 and Zhongmai-8, respectively, and the corresponding values for Cd were about 30, 80, 20, 40, 60 and 10 mg Cd/L, respectively. Among the six varieties, Duokang-1 was found to be the most resistant to Cd and As toxicity, and Zhongmai-8 was the most sensitive to Cd and As co-contamination. The resistance of the six varieties was found dependant on the seedling uptake of Cd and As. Duokang-1 was the most suitable for cultivation in Cd and As co-contaminated soils.     

长江三角洲地区海相沉积物母质土壤对Cu的吸附解吸特性

分别以长江三角洲地区海相沉积物母质土壤的表层土和心层土为例,考察了其对重金属Cu的吸附、解吸及固定特性,目的是了解其在不同土壤结构的存在形态和迁移特性。研究表明：不同表层土和心层土的铜吸附容量可用Langmuir,Freundlich和Temkin吸附等温方程拟合,其中以Langmuir方程吻合度最高,回归计算出的最大吸附容量与实验结果基本一致;而其解吸动力学大部分符合指数方式。研究发现,大多数土壤的心层土的最大吸附容量大于表层土,解吸量小于表层土;表层土中对Cu的固定吸附量最大的是滩涂泥,最小的是滩砂泥;心层土中对Cu的固定吸附量最大的是滩潮土,最小的是滩砂泥。不同土壤对Cu的固定吸附量存在差异性,这与土壤自身的pH、OM等多种因素有关, 一般pH值大、OM值高的土壤对Cu的固定吸附量越大.     

In-field variation in 2,4-D mineralization in relation to sorption and soil microbial communities

This study was undertaken to assess 2,4-D mineralization in an undulating cultivated field, along a sloping transect (458 m to 442 m above sea level), as a function of soil type, soil microbial communities and the sorption of 2,4-D to soil. The 2,4-D soil sorption coefficient (Kd) ranged from 1.81 to 4.28 L kg^?1, the 2,4-D first-order mineralization rate constant (k) ranged from 0.04 to 0.13 day^?1 and the total amount of 2,4-D mineralized at 130 days (M₁₃₀) ranged from 24 to 39%. Both k and M₁₃₀ were significantly negatively associated (or correlated) with soil organic carbon content (SOC) and Kd. Both k and M₁₃₀ were significantly associated with two fatty-acid methyl esters (FAME), i17:1 and a18, but not with twenty-two other individual FAME. Imperfectly drained soils (Gleyed Dark Grey Chernozems) in lower-slopes showed significantly lesser 2,4-D mineralization relative to well-drained soils (Orthic Dark Grey Chernozems) in mid- and upper-slopes. Well-drained soils had a greater potential for 2,4-D mineralization because of greater abundance and diversity of the microbial community in these soils. However, the reduced 2,4-D mineralization in imperfectly drained soils was predominantly because of their greater SOC and increased 2,4-D sorption, limiting the bioavailability of 2,4-D for degradation. The wide range of 2,4-D sorption and mineralization in this undulating cultivated field is comparable in magnitude and extent to the variability of 2,4-D sorption and mineralization observed at a regional scale in Manitoba. As such, in-field variations in SOC and the abundance and diversity of microbial communities are determining factors that require greater attention in assessing the risk of movement of 2,4-D by runoff, eroded soil and leaching.