Quantifying the effects of climate variability and human activities on runoff for Kaidu River Basin in arid region of northwest China

Much attention has recently been focused on the effects that climate variability and human activities have had on runoff. In this study, data from the Kaidu River Basin in the arid region of northwest China were analyzed to investigate changes in annual runoff during the period of 1960–2009. The nonparametric Mann–Kendall test and the Mann–Kendall–Sneyers test were used to identify trend and step change point in the annual runoff. It was found that the basin had a significant increasing trend in annual runoff. Step change point in annual runoff was identified in the basin, which occurred in the year around 1993 dividing the long-term runoff series into a natural period (1960–1993) and a human-induced period (1994–2009). Then, the hydrologic sensitivity analysis method was employed to evaluate the effects of climate variability and human activities on mean annual runoff for the human-induced period based on precipitation and potential evapotranspiration. In 1994–2009, climate variability was the main factor that increased runoff with contribution of 90.5 %, while the increasing percentage due to human activities only accounted for 9.5 %, showing that runoff in the Kaidu River Basin is more sensitive to climate variability than human activities. This study quantitatively distinguishes the effects between climate variability and human activities on runoff, which can do duty for a reference for regional water resources assessment and management.     

浅析我国地表水与海水环境质量标准存在的问题

我国《水污染防治行动计划》和《近岸海域污染防治方案》中改善水质的工作目标和考核指标都是基于《地表水环境质量标准》和《海水水质标准》提出的,两项标准是我国水环境保护管理的重要抓手,在水污染防治中具有举足轻重的地位。文章对我国现行两项水环境质量标准存在的共性问题和两项标准之间衔接存在的问题进行分析,研究表明:两项标准间存在水质分类不衔接、水质指标设置不衔接、部分指标分析方法不同和部分指标标准限值衔接不科学等问题。基于此,文章建议应加强水质基准研究,尽快启动水质标准修订;针对水体富营养化问题,科学设置氮、磷指标;关注健康、安全,强化有毒有害污染物控制;科学划定河口区范围,制定河口区专属水质标准,旨在为我国水环境质量标准的修订提供参考,使水环境质量标准更好地服务于我国的水环境保护和陆海统筹的水污染防治工作。     

1936年天水南6级地震震害特征与发震构造

通过对历史地震资料的系统收集整理、现场调查及烈度点评估等工作,对1936年天水南6级地震等震线重新进行了改绘,并对此次地震的震害特征、等震线特征及其与活动构造间的关系进行了研究。结果表明,此次地震极震区最大烈度为Ⅷ度,集中位于天水镇及其以北地区;NEE向的礼县-罗家堡断裂中东段基本与此次地震重破坏区长轴线重合,应为此次地震的发震断裂;由于受NWW向西秦岭北缘断裂带与NNW向六盘山断裂带2条区域深大断裂及北部黄土区的影响,低烈度等震线长轴方向逆时针旋转,地震动及烈度向北衰减变缓,地震等震线呈现明显的南北衰减不对称性。     

Temperature and precipitation changes in different environments in the arid region of northwest China

Using 51 meteorological stations in the arid region of northwest China in the mountain, oasis, and the desert areas obtained from 1960 to 2010, this paper conducted a comparative analysis for detecting temperature and precipitation changes in the diverse environments. In recent 50 years, temperature has increased at 0.325, 0.339, and 0.360 °C per decade in the mountain, oasis, and the desert areas, respectively; and also, precipitation has increased at 10.15, 6.29, and 0.87 mm per decade, but in which the increasing trend of precipitation in desert area was not significant. Before the 1990s, the increase in temperature was the fastest in the desert area, up to 0.214 °C per decade, but was the slowest in the mountain area, only 0.103 °C per decade. The temperature rising was faster after the 1990s, 0.606 °C per decade, in the oasis area was fastest, but was the slowest in the desert region with 0.402 °C per decade. The precipitation in each area was stable from 1960 to 1986, but an increase in the oasis and mountain area was larger from 1987 to 2010.     

1961—2016年中国昼夜降水变化的时空格局

全球气候变暖背景下中国降水量变化的区域差异显著。基于1961—2016年期间,全国763个观测台站白昼和夜间的降水观测数据,分别从昼夜降水量、降水日数、降水强度以及对总降水量的贡献率等四个方面,解读中国九大流域昼夜降水变化的时空格局。结果表明：① 昼夜降水量变化的流域差异显著,可归纳为四种类型：昼夜同增型、昼夜同减型、昼增夜减型和昼减夜增型。② 流域总降水量变化与昼夜降水量密切相关。淮河流域降水量减少是由白昼降水量（-0.72 mm/a）减少所致,而黄河流域降水量减少则是由夜间降水量（-0.21 mm/a）减少所致。③ 干旱区、半干旱区及半湿润区的流域,昼夜大雨的雨量要高于昼夜暴雨;湿润区的流域,则表现为昼夜暴雨的雨量要高于昼夜大雨,尤其是珠江流域和东南诸河流域。④ 从全国尺度来看,白昼大雨、夜间大雨和暴雨对总降水量的贡献率超过10%,而白昼暴雨的贡献率约10%。湿润区流域昼夜暴雨对总降水量的贡献率高于昼夜大雨对总降水量的贡献率,而干旱区-半干旱区流域则相反。研究结果有助于深化认识全球变暖对区域日降水循环的影响。     

西北干旱区山区融雪期气候变化对径流量的影响

利用8个山区气象站1960-2010年日平均气温、降水和7个出山口水文站的年径流数据(1960-2008),统计分析了山区融雪期开始时间、结束时间、天数、温度和降水的变化趋势及其空间差异性,并定量评估了年径流量对融雪期温度和降水变化的敏感性.结果表明,近50年来,山区融雪期平均提前了15.33天,延迟了9.19天;其中,天山南部山区融雪期提前时间最长,为20.01天,而延迟时间最短,仅6.81天;祁连山北部山区融雪期提前时间最短(10.16天),而延迟时间最长(10.48天).这显示山区融雪期提前时间越长,延迟时间则越短.山区融雪期平均降水量增加了47.3 mm,平均温度升高了0.857℃;其中天山南部山区降水增量最大,达65 mm,昆仑山北部山区降水和温度增量均最小,分别为25 mm和0.617 ℃,而祁连山北部山区温度增量最高(1.05℃).河流径流量对融雪期气候变化敏感,降水变化诱发年径流量变化了7.69％,温度变化使得年径流量改变了14.15％.     

公元前186年甘肃武都地震考证与发震构造探讨

根据历史地震资料的重新考证和野外调查,认为现行地震目录所给出的公元前186年甘肃武都地震的参数不确切,应做如下修正:其重破坏区位于武都县桔柑乡——舟曲县坪定乡之间,震中位于武都县两河口附近,震级为7~71/4级, 烈度达Ⅸ~Ⅹ度. 这次地震重破坏区长轴方向为北西西向,大致与该区的迭部——白龙江断裂带中东段走向相吻合, 时间上与探槽揭露的该断裂段最晚一次古地震事件的年代（83plusmn;46）BC之前可以对比. 该断裂段至今仍保存有部分地震形变带的遗迹. 综合分析认为,公元前186年武都7~71/4级地震的发震构造应为迭部-白龙江断裂带的中东段.      

Effects of forest gaps on some microclimate variables in Castanopsis kawakamii natural forest

The objective of this study was to understand the effects of forest gap and variations in different seasons, gap size, locations and diurnal variations on forest microclimate and soil water content. Spatial and temporal distribution features of air temperature (TA ), soil temperature (TS ), relative humidity (h) and soil water content (Ψ) were measured in Castanopsis kawakamii natural forest gaps created by a severe typhoon or fallen dead trees. The results showed that: (1) the variations of TA , h, and TS in four seasons were extremely significant. The variations of Ψ in four seasons were extremely significant except for those between spring and summer. (2) The diurnal variations of TA and T S were expressed with a single peak curve. The diurnal variations of h and Ψ presented a high-low-high trend. (3) The variations of TA , h, and TS were extremely significant among the large, medium and small gaps in C. kawakamii natural forest. Medium gaps had the highest TA and the lowest h while small gaps were just contrary to medium gaps. The variations of Ψ were extremely significant for large, medium and small gaps except those between the medium and large gaps. (4) The TA , h, TS and Ψ were decreased from the gap center, canopy gap, expanded gap to understory. These results will help further our understanding of the abiotic and consequent biotic responses to gaps in the mid-subtropical broadleaved forests, which also provide a theoretical basis for the scientific management and population restoration of C. kawakamii natural forest.     

Hydrocarbon composition and distribution in a coastal region under influence of oil production in northeast Brazil

Waters and sediments from the Potiguar Basin (NE Brazilian coast) were investigated for the presence and nature of polycyclic aromatic hydrocarbons (PAH) and aliphatic hydrocarbons. The region receives treated produced waters through a submarine outfall system serving the industrial district. The total dispersed/dissolved concentrations in the water column ranged from 10-50 ng L⁻¹ for ∑16PAH and 5-10 μg L⁻¹ for total aliphatic hydrocarbons. In the sediments, hydrocarbon concentrations were low (0.5-10 ng g⁻¹for ∑16PAH and 0.01-5.0 μg g⁻¹ for total aliphatic hydrocarbons) and were consistent with the low organic carbon content of the local sandy sediments. These data indicate little and/or absence of anthropogenic influence on hydrocarbon distribution in water and sediment. Therefore, the measured values may be taken as background values for the region and can be used as future reference following new developments of the petroleum industry in the Potiguar Basin.