Distinct effects of temperature change on discharge and non-point pollution in subtropical southern China by SWAT simulation

Abstract

Climate change impacts on the availability of water resources. Projection of hydrological response to temperature change is valuable for water management. Such response may be complex and uncertain at the watershed scale and differences may exist between low and high latitudes. A simulation experiment was achieved by using SWAT modelling in the upstream watershed of Dongjiang River, South China. After calibration, the model was found appropriate for hydrological simulation in the study area and was run from 1995 to 2004 under a series of temperature change scenarios to reveal the response of streamflow and loads of sediment and nutrients. For a temperature increase of 3°C, streamflow, sediment and total phosphorus decreased by 5.2, 7.7 and 2.2%, respectively. Linear temperature change seemed to have a linear hydrological response. Nutrient deficiency was still the primary vegetation stress compared with water availability and temperature stress under rising temperatures. Comparison with previous research showed that two southern subtropical watersheds (one upstream and one downstream) gave different hydrological responses. Sediment and inorganic nitrogen loads decreased in the upstream watershed, but increased in the downstream one, when temperature increased. Under the warming scenarios, streamflow and sediment loads decreased throughout the year, especially during the wet season, which is different from results at high latitudes. Nutrient export decreased in April–June, but increased in the remaining months. Simulation results should be applied with caution in water resources management, as simulated climate change had variable hydrological influence in different regions and seasons.

Citation Xu, H. and Peng, S.L., 2013. Distinct effects of temperature change on discharge and non-point pollution in subtropical southern China by SWAT simulation. Hydrological Sciences Journal, 58 (5), 1032–1046.

Editor Z.W. Kundzewicz; Associate editor C.-Y. Xu     

Exploitation of Landsat data for snow zonation mapping in the Hindukush,Karakoram and Himalaya (HKH) region of Pakistan

Abstract

In the Hindukush, Karakoram and Himalaya (HKH) region of Pakistan, many glaciological variables are still not known due to the remoteness and harsh weather conditions of the area. A remote sensing technique is therefore applied to map the snow zonation in the HKH region. Landsat 7 ETM+ data for the year 2003 are used in this study. Image classification and image processing techniques are applied to map, for the first time, the major snow zones in the HKH region. Six classes are identified: the results show that the area covered by the highest-altitude snow (Snow I), lower-altitude snow (Snow II), bare ice, debris-covered ice, wet snow and shadow is 21 529.42, 22 472.58, 8696.41, 8038.75, 12 159.37 and 7322.30 km², respectively. The study also indicates that the equilibrium line altitude (ELA) lies between 5000 and 5500 m above sea level, with an accumulation area ratio (AAR) of 0.60.

Citation Butt, M.J., 2013. Exploitation of Landsat data for snow zonation mapping in the Hindukush, Karakoram and Himalaya (HKH) region of Pakistan. Hydrological Sciences Journal, 58 (5), 1088–1096.     

Cenozoic tectonic jumping and implications for hydrocarbon accumulation in basins in the East Asia Continental Margin

Tectonic migration is a common geological process of basin formation and evolution. However, little is known about tectonic migration in the western Pacific margins. This paper focuses on the representative Cenozoic basins of East China and its surrounding seas in the western Pacific domain to discuss the phenomenon of tectonic jumping in Cenozoic basins, based on structural data from the Bohai Bay Basin, the South Yellow Sea Basin, the East China Sea Shelf Basin, and the South China Sea Continental Shelf Basin. The western Pacific active continental margin is the eastern margin of a global convergent system involving the Eurasian Plate, the Pacific Plate, and the Indian Plate. Under the combined effects of the India-Eurasia collision and retrogressive or roll-back subduction of the Pacific Plate, the western Pacific active continental margin had a wide basin-arc-trench system which migrated or ‘jumped’ eastward and further oceanward. This migration and jumping is characterized by progressive eastward younging of faulting, sedimentation, and subsidence within the basins. Owing to the tectonic migration, the geological conditions associated with hydrocarbon and gashydrate accumulation in the Cenozoic basins of East China and its adjacent seas also become progressively younger from west to east, showing eastward younging in the generation time of reservoirs, seals, traps, accumulations and preservation of hydrocarbon and gashydrate. Such a spatio-temporal distribution of Cenozoic hydrocarbon and gashydrate is significant for the oil, gas and gashydrate exploration in the East Asian Continental Margin. Finally, this study discusses the mechanism of Cenozoic intrabasinal and interbasinal tectonic migration in terms of interplate, intraplate and underplating processes. The migration or jumping regimes of three separate or interrelated events: (1) tectonism-magmatism, (2) basin formation, and (3) hydrocarbon-gashydrate accumulation are the combined effects of the Late Mesozoic extrusion tectonics, the Cenozoic NW-directed crustal extension, and the regional far-field eastward flow of the western asthenosphere due to the India-Eurasia plate collision, accompanied by eastward jumping and roll-back of subduction zones of the Pacific Plate.     

The Southern Ocean silica cycle

The Southern Ocean is a major opal sink and plays a key role in the silica cycle of the world ocean. So far however, a complete cycle of silicon in the Southern Ocean has not been published. On one hand, Southern Ocean surface waters receive considerable amounts of silicic acid (dissolved silica, DSi) from the rest of the world ocean through the upwelling of the Circumpolar Deep Water, fed by contributions of deep waters of the Atlantic, Indian, and Pacific Oceans. On the other hand, the Southern Ocean exports a considerable flux of the silicic acid that is not used by diatoms in surface waters through the northward pathways of the Sub-Antarctic Mode Water, of the Antarctic Intermediate Water, and of the Antarctic Bottom Water. Thus the Southern Ocean is a source of DSi for the rest of the world ocean. Here we show that the Southern Ocean is a net importer of DSi: because there is no significant external input of DSi, the flux of DSi imported through the Circumpolar Deep Water pathway compensates the sink flux of biogenic silica in sediments.     

云南个旧锡矿区矿业活动对土壤重金属的累积贡献

矿业活动是土壤重金属累积的重要原因之一。分析云南个旧锡矿区矿业活动区、与矿业活动区地质条件相同的矿业活动影响区和未受矿业活动影响的参照区表层土壤7种重金属元素之间的相关性,以参照区表层土壤重金属总量、参照区土壤重金属似背景值分别评价矿业活动对矿业活动区和矿业活动影响区土壤重金属的累积贡献量和贡献率。结果表明,矿业活动区重金属累积贡献率排序为PbZnAsCuCdCrHg,影响区重金属累积贡献率排序为PbZnAsCuCdCrHg,Pb、Cd、As、Zn、Cu与矿业活动关系密切,矿业活动区Pb、Cd、As均表现为极高累积和极高风险,应作为矿业活动治理的重点元素。     

某金矿污染区人群头发重金属累积及其变化

矿业活动区环境重金属污染对人群健康的危害是人们关注的重大环境问题。以2009年某金矿区水土环境重金属污染区内的A村村民头发为研究对象,同时以环境相对清洁的B村人群头发中重金属含量为对比值。研究结果表明,污染区不同年龄段人群头发中的重金属平均含量具有一定的统计学意义,不同性别、不同年龄段人群头发中,Hg、Pb、Cd平均含量分别是对照区人发中的7.81倍、6.75倍和4.20倍。总体而言,污染区人发中重金属含量仍在持续累积。人发中高含量的重金属与人体健康存在较好的相关性,金矿区环境污染对人群健康危害严重。     

黑龙江省三江-穆棱河J_2-K_1沉积体系与聚煤模式

研究煤盆地的构造是进行找煤勘查工作的必要基础。本文全面分析了黑龙江省东部三江—穆棱河J2-K1聚煤环境模式及分布特点,为在该区找煤指明了勘查方向和具体目标。     

山东东营凹陷幕式成藏的流体包裹体证据

利用流体包裹体综合分析技术,研究东营凹陷不同构造区带油气成藏方式。结果证明,不同构造区带成藏期古压力及成藏方式具差异性:北部陡坡带沙四段烃源岩上储层油气成藏主要分3期,成藏方式以间歇的幕式充注为主;中央背斜主要分2期,成藏方式以突发式的幕式充注为主;南部缓坡带仅1期,早期成藏方式以持续性充注为主。在凹陷南部缓坡带孔店组的储层中发现沸腾包裹体,分析认为成藏晚期发生过幕式充注,推测在沙四烃源岩下存在新的成藏体系。东营凹陷不同区带成藏模式的确定,可为在高勘探程度地区寻找隐蔽油气藏提供理论依据。     

王集-新庄地区包裹体特征及油气成藏期次

通过采集泌阳凹陷王集-新庄地区岩心样品,对其中包裹体进行盐度特征分析、镜下观察及均一温度测定;结果表明王集-新庄地区包裹体分为两期,与盆地埋藏史和热史研究划分的早、晚两个成藏期相对应。结合生排烃史综合分析,该区油气分两期成藏,早期油气成藏期主要发生在核一段末期~廖庄组沉积期,为小规模油气成藏,该期主要生成低熟油;晚期油气成藏期主要发生在廖庄末抬升期,为大规模油气成藏,是形成现今油田的主要成藏期。利用油气包裹体进行油气成藏研究,必须和宿主矿物的矿物岩石学分析及其他成藏期次分析方法结合使用,才能使分析结果更加客观可信。     

沾化凹陷孤北洼陷沙四上亚段油气成藏组合特征

通过油源对比及储层特征、盖层特征、油气藏特征研究,将孤北地区沙四上亚段划分为自源自生自储油气成藏组合和混源旁生侧储油气成藏组合,解释了孤北地区沙四上亚段存在的3类油气成藏模式:自源侧向运聚模式、自源垂向运聚模式、混源混向运聚模式。构造圈闭、不整合面和断层发育是成藏组合油气成藏的关键因素。在异常高压的作用下,油气沿断层、不整合面和骨架砂体共同组成油气二次运移的立体网络,使陡坡、低隆起、缓坡各构造岩相带都能够成为油气运移的有利指向。