中中新世秦安黄土-古土壤序列磁性增强机制及其环境意义

中中新世黄土高原风尘堆积序列磁化率显著增高,在区域内已成为地层对比标志,然而其磁性增强机制依然不清楚.本文对秦安地区QA-I剖面约14~17.1 Ma期间的黄土-古土壤样品进行了系统的环境磁学、岩石磁学（热磁性质、磁滞性质、非磁滞剩磁与饱和等温剩磁比值χ_ARM/SIRM等）和色度指标分析.结果表明,QA-I剖面黄土-古土壤序列样品中磁性矿物为准单畴（PSD）磁铁矿、超顺磁/单畴（SP/SD）磁赤铁矿和赤铁矿,古土壤中细粒磁赤铁矿含量高于上下相邻黄土层.CBD（Citrate-Bicarbonate-Dithionite）处理方法显示,中中新世风尘序列中碎屑成因的PSD磁铁矿含量变化不大,约14.5~16.0 Ma期间成壤成因SP/SD磁赤铁矿含量的增多,是导致该时期风尘堆积序列磁化率增强的主要原因;这与该时期较低的土壤发育程度并不一致,表明CBD处理方法虽然可有效获取成壤成因SP/SD磁赤铁矿信息,却无法区分其为当地还是源区成壤成因.低温磁学研究表明,QA-I剖面约14.5~16.0 Ma期间SP/SD磁赤铁矿可能为碎屑磁铁矿颗粒的风化外壳,其含量高低变化与风尘样品中值粒径粗细变化一致,揭示出此类磁性颗粒含量受控于风力强弱,可能为源区风化成因.尽管中中新世古土壤样品的磁化率与上下黄土层相比可反映其成壤强度,但约14.5~16.0 Ma期间SP/SD磁赤铁矿含量变化可能同时受到当地成壤强度以及源区风化的影响,导致磁化率与当地成壤强度之间关系较为复杂.因此,中新世风尘堆积序列长尺度的磁化率趋势并不反映东亚夏季风强度的变化.

     

Major-ion bulk deposition around an active volcano (Mt. Etna, Italy)

Bulk atmospheric deposition of major cations (Na, K, Ca, Mg) and anions (Cl, F, SO₄) were measured at 15 sites around an active volcano, Mount Etna, from 2001 to 2003. Their composition indicates several natural sources, among which deposition of plume-derived volcanogenic gas compounds is prevalent for F, Cl and S. Plume-derived acidic compounds are also responsible for the prevailing acidic composition of the samples collected on the summit of the volcano (pH in the 2.45–5.57 range). Cation species have complex origin, including deposition of plume volcanogenic ash and aerosols and soil-dust wind re-suspension of either volcanic or carbonate sedimentary rocks. Variation of the deposition rates during the March 2001–March 2003 period, coupled with previous measurements from 1997 to 2000 (Appl Geochem 16:985–1000, 2001), were compared with the variation of SO₂ flux, volcanic activity and rainfall. The deposition rate was mainly controlled by rainfall. Commonly, about 0.1–0.9% of HF, HCl and SO₂ emitted by the summit crater's plume were deposited around the volcano. We estimate that ∼2 Gg of volcanogenic sulphur were deposited over the Etnean area during the 2002–2003 flank eruption, at an average rate of ∼24 Mg day⁻¹ which is two orders of magnitude higher than that typical of quiescent degassing phases.     

The Tectonic Uplift and Its Environmental Effects of the Qinling Mountains During the Cenozoic Era: Progress and Problems

The Qinling Orogen, a majestic high mountain, is located in the center of China mainland. Qinling Mountains is nearly 2 500 km from the west to the east. It holds a very prominent role not only in the geological but also in the geographical study. In geology, it was built through collision between the North China and South China Blocks. It became the backbone of the tectonic framework of China mainland. In the other way, Qinling is the geographical boundaries in ecological and cultural environment between the northern and the southern China. Many previous studies have dealt with the tectonic system dynamics and structural evolution of Qinling, but most work has focused on the tectonic evolution of the Qinling from the Paleozoic to the Mesozoic. However, the Cenozoic tectonic uplift evolution of Qinling has caused less attention, and little research has been done on the environmental effect of Qinling. And there are still debates about these two questions. The purpose of this paper was to provide an overview of the current studies about the Cenozoic tectonic uplift and its environmental effects of the Qinling Mountains. Finally, this paper pointed out the existing research achievements and the problems to be solved in future research.     

国际海底区域环境保护制度分析与中国实践

为促进国际海底区域资源开发和环境保护的协调可持续发展,提高我国在相关领域的话语权和执行力,文章系统分析国际海底区域环境保护制度的发展特征及其存在的问题,总结我国对国际海底区域环境保护的实践和展望,并提出对策建议。研究结果表明:国际海底区域环境保护制度经历萌芽、成形、发展和充实4个阶段,发展特征主要包括理念的更新、原则的完善以及义务和责任的明确,然而至今在规章环境保护条款、《联合国海洋法公约》非缔约国的环境保护权责和相关利益平衡等方面仍存在问题;我国从参与制定相关制度和开展国内法探索等方面积极实践国际海底区域环境保护;未来应从制定环境保护标准、探索政策环境和平衡各方利益等方面完善国际海底区域环境保护制度,我国应继续参与相关国际法律制度的制定以及完善国内海洋环境保护制度。     

煤矸石的环境危害及综合利用研究

针对我国矿区煤矸石大量排放的现状,介绍了煤矸石的形成以及煤矸石大量堆放对环境所产生的危害和影响,并概述了煤矸石污染的防治措施及其综合利用途径。     

广东沿海经济带海洋环境与经济增长的协调关系实证研究

环境与经济的关系是社会发展中不可忽视的重要问题。文章基于环境库茨涅兹理论构建广东沿海经济带主要海洋污染物排放量与人均GDP的线性回归模型,探索海洋环境随经济增长的变化规律,并采用熵变方程法进一步描述海洋环境与经济增长的协调关系。研究结果表明:广东沿海经济带以第二和第三产业为主导,经济增长速度快,但海洋污染物排放量逐年增加,其中珠三角是海洋污染物排放的主体区域;广东沿海经济带海洋环境与经济增长的EKC曲线因主要海洋污染物类别和地区的差异而呈现线型、"倒U"型、"N"型和"倒N"型等不同形式,整体海洋环境污染与人均GDP的拟合趋势表现为单调递增的线性变化,海洋环境污染程度随经济增长而显著加剧;广东沿海经济带海洋环境与经济增长处于严重不协调状态,经济增长与海洋环境质量的变化方向相反;亟须优化调整广东沿海经济带的产业分工布局,强化海洋环境保护制度保障,构建和完善海洋环境与经济增长的协调机制。     

Uranium and Thorium Isotope Distribution in an Offshore Bottom Sediment Core of the Selenga Delta, Lake Baikal, Siberia

Distribution of uranium and thorium isotopes in a short sediment core obtained offshore of the Selenga Delta in Lake Baikal, Siberia, was investigated to establish their sedimentary behaviors and to look for a linkage to paleoenvironmental changes. The sediments were composed of dominantly fine detrital materials (70–85%) and a relatively high sedimentation rate (ca. 0.03 cm y⁻¹). The depth profile of ²³⁸U content in bulk sediment samples showed a large variation of 70–123 Bq kg⁻¹, while ²³²Th profile showed a relatively narrow range from 36 to 56 Bq kg⁻¹. The observed ²³⁴U/²³⁸U activity ratios revealed a marked disequilibrium ranging from 1.53 to 1.84 with a mean value of 1.71 ± 0.07, demonstrating the presence of 50–80% authigenic ²³⁸U in the bulk sediments. The distribution of this authigenic ²³⁸U did not display any clear correlation with variations in sediment composition (organic, carbonate, Bio-SiO₂ and mineral contents) including grain size median. The profile of terrigenous ²³⁸U showed a relatively similar pattern to that of ²³²Th. Results of sequential leaching indicate that ²³⁸U in Fe–Mn oxyhydroxides fractions were responsible for the distribution of authigenic ²³⁸U rather than in Bio-SiO₂ fraction. The distribution of authigenic ²³⁸U in the bottom sediments may be explained by the fluctuation of U adsorption capacity on particles including organic matter and Fe–Mn oxyhydroxides before they entered the lake. This study highlights the potential use of authigenic and terrigenous U (Th) signatures in sediments to trace the behavior of U (Th) and to reconstruct environmental (e.g., hydrological) changes in the lake catchment area.     

Spatio-temporal variability of phytoplankton assemblages in the Pearl River estuary, with special reference to the influence of turbidity and temperature

The Pearl River Estuary is among the largest estuaries in the subtropical areas of the world. Along the salinity and turbidity gradient between the freshwater reach of the Pearl River and the marine water of the South China Sea, the spatial and temporal composition and abundance of phytoplankton was examined in relation to physic-chemical variables during the dry and wet seasons of 2009. Water samples for phytoplankton and environmental parameters were collected from 18 stations during two seasons along a transect from upper estuary to estuarine and marine sectors. A total of 162 species belonging to 7 phyla were identified, with diatoms dominated in both seasons while dinoflagellates proliferated in autumn. Two main clusters and three sub-clades under each main cluster corresponding to seasons and water sectors were defined with multivariate analysis (cluster and nMDS). Based on the species composition and abundance of phytoplankton, both seasonal and spatial variability were observed at a significant level (ANOSIM: season effect, R=0.896, P<0.01; station effect, R=0.463, P<0.01). The correlation analysis between biotic and abiotic variables indicated that instead of the “proverbial” anthropogenic nutrients loading and salinity gradient, the best 2-variable combination (temperature and turbidity) showed a significant effect on the pattern of phytoplankton assemblages (ρ_w=0.49, BIOENV analysis) between wet and dry seasons in the Pearl River Estuary. This result suggests that physical disturbance either natural or manmade is a more important factor in regulating the phytoplankton community structure within the hydrologically distinct zone of estuaries.     

Biodegradation of Herbicide Propanil and Its Subproduct 3,4‐Dichloroaniline in Water

The rational use of pesticides generates an impact which is normally reversed and eliminated by the environment itself. However, the indiscriminate use of pesticides makes its natural degradation rhythm difficult, prolonging their presence in the soil for a great deal of time. Aiming towards a decrease in the environmental impact of pesticides, soil microorganisms capable of degrading pesticides, such as propanil, were investigated. An Enterobacter cloacae strain, isolated from rice field soil, was exposed to the herbicide propanil alone and in a mixture containing also bentazone, clomazone, quinclorac, and 2,4‐D. This bacterium was able to eliminate 100% of the applied propanil in 28 days. Propanil degradation in the 5‐herbicide mixture was much lower than that of individual pesticide degradation. The aeration of the system helped to degrade propanil and its subproduct 3,4‐dichloroaniline much faster. LC with UV detection was used to determine the remaining concentrations of the herbicides and their subproducts.     

Study of shallow groundwater quality evolution under saline intrusion with environmental isotopes and geochemistry

Evolution of the shallow groundwater quality under saline intrusion in porous aquifer system has been studied with environmental isotopes and geochemistry in the Laizhou Bay area, China. Two campaigns of water sampling from various sources were carried out in spring and winter for environmental isotopic and chemical analyses. The origin of groundwater salinity from intrusion of both modern seawater and deep brine water was identified by analysing the correlations between ¹⁸O, D, T, Cl⁻, SO₄²⁻ and electrical conductivity. The results indicate that the brine is originated from evaporating and concentrating of intruded seawater and its δD and δ¹⁸O are different from modern seawater but similar to those of mixture of seawater with fresh groundwater. It is hard to distinguish the salinity origin in this area by the δD–δ¹⁸O relationship alone. The relations between δ¹⁸O and conductivity, Cl⁻ and SO₄²⁻ have been used to identify the salinity origin due to the distinct difference in salinity between the brine and seawater, conjunctively with use of T. A threshold of T = 12 TU was adopted to identify the origin of saline groundwater.