沉积物中溶解性有机质的垂直分布光谱特性

采用紫外光谱和三维荧光光谱结合平行因子分析（PARAFAC）方法对瀛湖沉积物中溶解有机质（dissolved organic matters,DOM）垂直分布的光谱特性进行了分析,利用荧光指数（fluorescence index,FI）、腐殖化指数（humification index,HIX）和生物源指数（biological index,BIX）解析了沉积物中DOM荧光组分、空间分布特征和来源。紫外光谱结果表明：瀛湖沉积物的UV254值在0.14~0.30之间,最大值出现在深度10~11 cm处,深层（20 cm以下深度）沉积物UV254值趋于稳定。A250/A365比值在3.69~9.98之间,均值为5.36,表明瀛湖沉积物DOM以富里酸为主。三维荧光光谱结合平行因子分析结果表明：沉积物DOM包含3类4个荧光组分,即类腐殖质组分（C1和C2）、类蛋白组分（C3和C4）,其中,类腐殖质组分的荧光强度约占全部组分荧光强度的60.7%;随着深度的增加,3个采样点的类蛋白质组分（C3和C4）的荧光强度均呈现下降趋势。FI、HIX和BIX都表明瀛湖沉积物DOM的来源主要是由沉积物中自生微生物活动产生。其中,FI在1.73~2.10范围内,BIX处于0.72~0.96范围内,HIX在1.39~4.72范围内。     

Sedimentary record of hydrophobic organic compounds in relation to regional economic development: A study of Taihu Lake, East China

Sediment cores taken from Taihu Lake, East China were analyzed for polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs) and polybrominated biphenyl ethers (PBDEs). The results showed a general sharp increase of HCH, DDT, PAH and PBDE concentrations in the surface layers, corresponding to a sedimentation time of 1980 and 1990 onward in the Meiliang Bay and Xukou Bay, respectively. The source of PAHs has largely transferred from petrogenic to pyrogenic origin, and good relationships were observed between sediment PAH concentrations and the regional gross domestic product. The sharp increase of DDTs in recent years may be related to the mobilization and migration of these chemicals from surface soil to lake sediment, as a result of enhanced soil run-off due to large scale land transform, as well as the contribution of current usage of dicofol and DDT-containing anti-fouling paints.     

Spatial and temporal distribution of polycyclic aromatic hydrocarbons (PAHs) in sediments from Daya Bay, South China

The spatial and temporal distribution of polycyclic aromatic hydrocarbons (PAHs) has been investigated in Daya Bay, China. The total concentration of the 16 USEPA priority PAHs in surface sediments ranged from 42.5 to 158.2 ng/g dry weight with a mean concentration of 126.2 ng/g. The spatial distribution of PAHs was site-specific and combustion processes were the main source of PAHs in the surface sediments. Total 16 priority PAH concentration in the cores 8 and 10 ranged from 77.4 to 305.7 ng/g and from 118.1 to 319.9 ng/g respectively. The variation of the 16 PAH concentrations in both cores followed the economic development in China very well and was also influenced by input pathways. Some of the PAHs were petrogenic in core 8 while pyrolytic source was dominant in core 10. In addition, pyrolytic PAHs in both cores were mainly from the coal and/or grass and wood combustion.     

垃圾渗滤液有机物特征及臭氧对其结构的影响

为分析不同填埋龄的垃圾渗滤液中有机物的组分特征及臭氧氧化对其结构的影响,选取成熟和年轻的垃圾渗滤液,利用液相色谱-有机碳-有机氮-紫外吸收(LC-OCD-OND-UVD)、紫外可见光谱、三维荧光光谱和树脂分离技术表征了不同填埋龄垃圾渗滤液中有机物的组分特征。结果表明：在2种垃圾渗滤液有机物中,主要组分为以类富里酸为代表的憎水性腐殖质类和亲水的中性小分子有机化合物,且其组分比例随着填埋龄增加可分别提高至60%和28%。年轻渗滤液中的高含量生物多聚物组分(BP)是其最显著特征。臭氧氧化可快速分解BP并最终生成类腐殖质的分解产物,但TOC去除率<10%。对于含量低于4%的腐殖质类小分子酸,因其含氮杂环结构成为最难矿化的有机物,故较低臭氧投加量无法将其氧化分解。LC-OCD-OND-UVD结合其他表征方法印证分析是获取有机物信息的有效手段,可为深入了解有机物的氧化分解过程提供参考。     

Impacts of microbial redox conditions on the phase distribution of pyrene in soil-water systems

Variations in the soil/sediment organic matter (SOM)-hydrophobic organic contaminant (HOC) bindings upon microbially mediated redox conditions were examined. While the extractability of pyrene associated with soil declined after its biodegradation began during aerobic incubation, its variations were almost constant (±3.0-4.4%) during anoxic/anaerobic incubations. The dissolved organic matter released from the soil incubated under highly reduced conditions became more humified and aromatic, had a higher average molecular weight, and was more polydispersed compared to that obtained from oxic incubation, similar to the SOM alterations in the early stage of diagenesis (humification). The concentrations of pyrene in the aqueous phase increased significantly during the soil incubations under highly reduced conditions due to its favorable interaction with the altered DOM. Our results suggest that the microbially mediated redox conditions have significant impacts on SOM and should be considered for the transport, fate, bioavailability, and exposure risk of HOCs in the geo-environments.     

Impact of soil organic matter on the distribution of polycyclic aromatic hydrocarbons (PAHs) in soils

The knowledge on the distribution of hydrophobic organic contaminants in soils can provide better understanding for their fate in the environment. In the present study, the n-butanol extraction and humic fractionation were applied to investigate the impact of SOM on the distribution of polycyclic aromatic hydrocarbons (PAHs). The results indicated that 80.5%-94.8% of the target PAHs could be extracted by n-butanol and 63.1%-94.6% of PAHs were associated with fulvic acid (FA). Concentrations of un-extracted PAHs increased significantly with the increasing soil organic matter (SOM), however, such an association was absent for the extractable fractions. The results suggested that the sequestration played a critical role in the accumulation of PAHs in soils. SOM also retarded the diffusion of PAHs into the humin fractions. It implied that sequestration in SOM was critical for PAH distribution in soils, while the properties of PAH compounds also had great influences.     

Soil organic carbon storage in a mountain permafrost area of Central Asia (High Altai,Russia)

The thawing and subsequent decomposition of large stocks of soil organic carbon (SOC) currently stored in the northern circumpolar permafrost region are projected to result in a ‘positive’ feedback on global warming. The magnitude of this feedback can only be assessed with improved knowledge about the total size and geographic distribution of the permafrost SOC pool. This study investigates SOC storage in an under-sampled mountain permafrost area in the Russian High Altai. SOC stocks from 39 soil pits are upscaled using a GIS-based land cover classification. We found that the top 100 cm of soils in Aktru Valley and the adjacent Kuray Basin only holds on average 2.6 ± 0.6 kg C m⁻² (95% confidence interval), of which only c. 1% is stored in permafrost. Global warming will result in an upward shift of alpine life zones, with new plant cover and soil development at higher elevations. As a result, this type of mountain permafrost area might act as a net C sink in the future, representing a ‘negative’ feedback on global warming.Electronic supplementary materialThe online version of this article (10.1007/s13280-020-01433-6) contains supplementary material, which is available to authorized users.     

Pollution topography of chlorobenzenes and hexachlorobutadiene in sediments along the Kaohsiung coast, Taiwan--a comparison of two consecutive years' survey with statistical interpretation

Forty sediments were analyzed for chlorobenzenes (CBs) and hexachlorobutadiene (HCBD) to investigate their pollution topography along the Kaohsiung coast, Taiwan. Maximum CB concentrations found, varied from 15.4 ng/g dw for 1,2,3-TCB to 56.8 ng/g dw for 1,2,4-TCB, while higher HCBD concentrations were detected among north-bound stations (around the exit of the Tsoying outfall pipe) and its concentration decreases from north to south. Compared to a previous survey executed a year before, there is no statistically significant difference in CB and HCBD congeners between these two surveys (p = 0.68–0.87, two-tailed paired t-test). The spatial distribution of toxic index reveals that biological effects might occur near Tsoying and Dalinpu outfall pipe outlets which dispose of petro-chemical wastewater. Evidence found in this study also shows distinct CB patterns from the two nearby sources, the Dalinpu outfall pipe outlet and the Kaoping estuary. Principal component analysis shows that four principal components conducting CBs and HCBD distribution were extracted. Both the first two components (accounted for 58.8% of the total variance), comprised all of the CBs except HCB (DCBs to PeCB), were found not capable of differentiating any distinct pollution source. On the other hand, HCBD and HCB were extracted as third and fourth components, respectively, pointing out their distinct sources in this area.     

Changes in the chemical composition of water-extractable organic matter during composting: distribution between stable and labile organic matter pools

Aerobic decomposition and stabilization of organic matter during the composting of waste materials is primarily due to the biochemical transformation of water-soluble compounds in the liquid phase by the microbial biomass. For this reason water-soluble organic matter represents the most active fraction of compost, both biologically and chemically, and thus should directly reflect the biochemical alteration of organic matter. This work aims to elucidate the microbial-mediated processes responsible for the distribution of soluble organic matter between stable and labile pools with composting time. Accordingly, chemical analysis as well as UV absorption, and ¹H and ¹³C-NMR spectroscopy of samples collected during the industrial composting of urban waste revealed microbial induced transformation of water-extractable organic matter over time. The chemical composition changed from labile, hydrophilic, plant-derived organic compounds in the beginning to predominately stable, hydrophobic moieties comprising lignin-derived phenols and microbially-derived carbohydrates at later stages of composting.     

东部平原湖区沉积物中溶解性有机氮分布特征

选择东部平原湖区11个湖泊进行水质和表层沉积物调查,采用综合营养状态指数（TLI）对各湖泊营养状态进行评价,研究了沉积物溶解性有机氮（DON）和游离氨基酸（FAA）的含量分布及DON分子质量分级特征,并探讨了不同湖泊沉积物有机质来源。结果表明：除固城湖和骆马湖处于中营养水平外,东部平原湖区其他湖泊均处于富营养化状态。沉积物DON浓度差异较大,在9.98~182.00 mg·kg-1之间波动,均值为57.25 mg·kg-1,太湖、滆湖、阳澄湖沉积物DON含量较高,均在140 mg·kg-1以上,其他湖泊沉积物DON含量均在50 mg·kg-1以下。区域内氨基酸（FAA）分布比较均匀,FAA浓度在3.58~13.28 mg·kg-1之间,平均值是8.14 mg·kg-1。沉积物DON和FAA含量与沉积物其他形态氮、溶解性有机碳（DOC）等污染指标均表现出显著正相关性。东部平原湖区沉积物分子质量分级结果表明：该湖区沉积物DON、DOC和SUV254基本都分布在 30 kDa 2个范围内。东部平原湖区C/N比的值介于2.31~89.02之间,除滆湖外其他湖泊沉积物C/N值均大于10,说明该地区湖泊沉积物有机质主要来自外源。     

Characteristics of organic phosphorus fractions in different trophic sediments of lakes from the middle and lower reaches of Yangtze River region and Southwestern Plateau, China

In this study, the characteristics of organic phosphorus (Po) fractions in sediments of six lakes from the middle and lower reaches of Yangtze River region and Southwestern China Plateau, China were investigated using a soil Po fractionation scheme, and the relationships between Po, inorganic phosphorus (Pi) and pollution status were also discussed. The results show that the rank order of Po fractions was: residual Po>HCl-Po>fulvic acid-P>humic acid-P>NaHCO3-Po, with their average relative proportion 8.7:4.6:3.2:2.1:1.0. Po fractions, especially nonlabile Po, were significantly correlated with organic matter, Po and NaOH-Pi. Different distribution patterns of P fractions were observed in those two different regions. Po fractions in the heavily polluted sediments were higher than those in moderately and no polluted sediments, it is suggested that Po should be paid more attention in the lake eutrophication investigation.     

Tracing the sources of refractory dissolved organic matter in a large artificial lake using multiple analytical tools

Structural and chemical characteristics of refractory dissolved organic matter (RDOM) from seven different sources (algae, leaf litter, reed, compost, field soil, paddy water, treated sewage) were examined using multiple analytical tools, and they were compared with those of RDOM in a large artificial lake (Lake Paldang, Korea). Treated sewage, paddy water, and field soil were distinguished from the other sources investigated by their relatively low specific UV absorbance (SUVA) values and more pronounced fulvic-like versus humic-like fluorescence of the RDOM samples. Microbial derived RDOM from algae and treated sewage showed relatively low apparent molecular weight and a higher fraction of hydrophilic bases relative to the total hydrophilic fraction. For the biopolymer types, the presence of polyhydroxy aromatics with the high abundance of proteins was observed only for vascular plant-based RDOM (i.e., leaf litter and reed). Molecular weight values exhibited positive correlations with the SUVA and the hydrophobic content among the different RDOM, suggesting that hydrophobic and condensed aromatic structures may be the main components of high molecular weight RDOM. Principal component analysis revealed that approximately 77% of the variance in the RDOM characteristics might be explained by the source difference (i.e., terrestrial and microbial derived) and a tendency of further microbial transformation. Combined results demonstrated that the properties of the lake RDOM were largely affected by the upstream sources of field soil, paddy water, and treated sewage, which are characterized by low molecular weight UV-absorbing and non-aromatic structures with relatively high resistance to further degradation.     

Effect of microbial activity, soil water content and added copper on the temporal distribution patterns of HCB and DDT among different soil organic matter fractions

Temporal changes in the distribution of exogenous HCB and DDT among different soil organic matter fractions were studied under sterile and non-sterile conditions, different soil water contents, and different concentrations of added Cu(2+). The residence time was 311days. Soil organic matter was fractionated into fulvic acid (FA), humic acid (HA), bound-humic acid (BHA), lipid, and insoluble residue (IR) fractions by a methyl isobutyl ketone (MIBK) method. Results revealed that there is a mass transfer tendency of DDT and HCB from FA, HA and BHA to IR and lipid fractions with increasing residence time. Microbial activity accelerated the mass transfer, while the addition of Cu(2+) slowed it down. The HCB and DDT transfer rate decreased as the soil moisture increased from 1.9% to 60%, but increased when soil moisture increased further to 90%. A two-compartment first order kinetic model was used to describe the mass transfer from FA, HA and BHA.     

Polybrominated diphenyl ethers in sediments of the Daliao River Estuary, China: levels, distribution and their influencing factors

The concentrations, compositional profiles, possible sources of polybrominated diphenyl ethers (PBDEs) in sediments of the Daliao River Estuary as well as the factors influencing the distribution of PBDEs were investigated. The total concentrations of PBDEs ranged from 0.13 to 1.98 ng g⁻¹ d.w. BDE209 was the dominating congener in all sediment samples, indicating the pollution of PBDEs in the Daliao River Estuary mainly came from the use of deca-BDE commercial mixtures. The intrusion of sea waters promoted the deposition of the colloid-associated PBDEs in the estuary. There were significantly negative correlations between PBDE concentration in sediment with pH value and salinity in the bottom water. The higher river flow in the flood season (summer) obviously accelerated the transport of PBDEs, and thereby increased the risk of PBDE contamination to the deep ocean. Moreover, a positive correlation between TOC and PBDE distributions was observed, suggesting that TOC regulated the distributions of PBDEs in sediments of Daliao River Estuary.     

Environmental–geochemical characteristics of Cu in the soil and water in copper-rich deposit area of southeastern Hubei Province, along the middle Yangtze River, Central China

In this study, the natural Cu background concentration and Cu natural and anthropogenic contamination in soil, water and crop were investigated systematically in Huangshi area. The results show that regional geology is the dominant factor controlling the natural Cu background concentration in soil and water, and that pH is important to control the vertical distribution of Cu in soil under the same geographical and climatic conditions. The mineralization of rock bodies causes the natural Cu increase in soil and water, whereas, a large number of mining–smelting plants and chemical works are the main sources of Cu anthropogenic contamination. Cu in naturally and anthropogenically polluted soil displays differences in total and available contents, vertical distribution patterns and physico-chemical properties, the same happens in water.