Optimization of water-urban-agricultural-ecological land use pattern:A case study of Guanzhong Basin in the southern Loess Plateau of Shaanxi Province,China

Extensive land use will cause many environmental problems.It is an urgent task to improve land use efficiency and optimize land use patterns.In recent years,due to the flow decrease,the Guanzhong Basin in Shaanxi Province is confronted with the problem of insufficient water resources reserve.Based on the Coupled Ground-Water and Surface-Water Flow Model(GSFLOW),this paper evaluates the response of water resources in the basin to changes in land use patterns,optimizes the land use pattern,improves the ecological and economic benefits,and the efficiency of various spatial development,providing a reference for ecological protection and high-quality development of the Yellow River Basin.The research shows that the land use pattern in the Guanzhong Basin should be further optimized.Under the condition of considering ecological and economic development,the percentage change of the optimum area of farmland,forest,grassland,water area,and urban area compared with the current land use area ratio is+2.3,+2.4,-6.1,+0.2,and+1.6,respectively.The economic and ecological value of land increases by14.1%and 3.1%,respectively,and the number of water resources can increase by 2.5%.

Arsenic Distribution Pattern in Different Sources of Drinking Water and their Geological Background in Guanzhong Basin, Shaanxi, China

To study arsenic （As） content and distribution patterns as well as the genesis of different kinds of water,especially the different sources of drinking water in Guanzhong Basin,Shaanxi province,China,139 water samples were collected at 62 sampling points from wells of different depths,from hot springs,and rivers.The As content of these samples was measured by the intermittent flowhydride generation atomic fluorescence spectrometry method （HG-AFS）.The As concentrations in the drinking water in Guanzhong Basin vary greatly （0.00-68.08 tg/L）,and the As concentration of groundwater in southern Guanzhong Basin is different from that in the northern Guanzhong Basin.Even within the same location in southern Guanzhong Basin,the As concentrations at different depths vary greatly.As concentration of groundwater from the shallow wells （〈50 m deep,0.56-3.87 μg/L） is much lower than from deep wells （110-360 m deep,19.34-62.91 μg/L）,whereas As concentration in water of any depth in northern Guanzhong Basin is 〈10 μg/L.Southern Guanzhong Basin is a newly discovered high-As groundwater area in China.The high-As groundwater is mainly distributed in areas between the Qinling Mountains and Weihe River; it has only been found at depths ranging from 110 to 360 m in confined aquifers,which store water in the Lishi and Wucheng Loess （Lower and Middle Pleistocene） in the southern Guanzhong Basin.As concentration of hot spring water is 6.47-11.94 μg/L; that of geothermal water between 1000 and 1500 m deep is 43.68-68.08 μg/L.The high-As well water at depths from 110 to 360 m in southern Guanzhong Basin has a very low fluorine （F） value,which is generally 〈0.10 mg/L.Otherwise,the hot springs of Lintong and Tangyu and the geothermal water in southern Guanzhong Basin have very high F values （8.07-14.96 mg/L）.The results indicate that high As groundwater in depths from 110 to 360 m is unlikely to have a direct relationship with the geothermal water in the same area.As concentration of all reservoirs and rivers （both contaminated and uncontaminated） in the Guanzhong Basin is 〈10 μg/L.This shows that pollution in the surface water is not the source of the high-As in the southern Guanzhong Basin.The partition boundaries of the high-and low-As groundwater area corresponds to the partition boundaries of the tectonic units in the Guanzhong Basin.This probably indicates that the high-As groundwater areas can be correlated to their geological underpinning and structural framework.In southern Guanzhong Basin,the main sources of drinking water for villages and small towns today are wells between 110-360 m deep.All of their As contents exceed the limit of the Chinese National Standard and the International Standard （〉10 μg/L） and so local residents should use other sources of clean water that are 〈50 m deep,instead of deep groundwater （110 to 360 m） for their drinking water supply.

Indication of hydrogen and oxygen stable isotopes on the characteristics and circulation patterns of medium-low temperature geothermal resources in the Guanzhong Basin,China

Guanzhong Basin is a typical medium-low temperature geothermal field mainly controlled by geo-pressure in the west of China.The characteristics of hydrogen and oxygen isotopes were used to analyze the flow and storage modes of geothermal resources in the basin.In this paper,the basin was divided into six geotectonic units,where a total of 121 samples were collected from geothermal wells and surface water bodies for the analysis of hydrogen-oxygen isotopes.Analytical results show that the isotopic signatures of hydrogen and oxygen throughout Guanzhong Basin reveal a trend of gradual increase from the basin edge areas to the basin center.In terms of recharge systems,the area in the south edge belongs to the geothermal system of Qinling Mountain piedmont,while to the north of Weihe fault is the geothermal system of North mountain piedmont,where the atmospheric temperature is about 0.2℃-1.8℃in the recharge areas.The main factors that affect the geothermal waterδ18O drifting include the depth of geothermal reservoir and temperature of geothermal reservoir,lithological characteristics,water-rock interaction,geothermal reservoir environment and residence time.Theδ18O-δD relation shows that the main source is the meteoric water,together with some sedimentary water,but there are no deep magmatic water and mantle water which recharge the geothermal water in the basin.Through examining the distribution pattern of hydrogen-oxygen isotopic signatures,the groundwater circulation model of this basin can be divided into open circulation type,semi-open type,closed type and sedimentary type.This provides some important information for rational exploitation of the geothermal resources.

Oxygen and hydrogen isotope exchange of geopressured thermal water in the central Guanzhong basin

Geothermal water of Xi＇an and Xianyang in the central Guanzhong basin is typically geopressured thermal water in China. 5180 and 5D data of geopressured thermal water＇in Xi＇an and Xianyang, combined with data from the perimeter of the basin, are analyzed to study features of hydrogen and oxygen shifts. The results show that ^18O exchange of geothermal water at the perimeter of the basin and in the non-geopressured thermal water in the center of the basin is not evident, while in most of the geopressured thermal water in the central basin, in cities such as Xi＇an and Xianyang, significant oxygen exchange had taken place as well as hydrogen exchange, suggesting that isotope exchanges would slowly move the geothermal water system towards equilibrium. Thermal water reservoirs in the central basin have passed through significant water-rock reactions. Moreover, the geothermal reservoir of Xianyang city is relatively much more enclosed than that of Xi＇an city. It has been observed that the more enclosed the geological environment of geothermal water is, the more obvious the oxygen shifts are. With the increasing of the depth, residence time, total amounts of dissolute solids and temperatures of geothermal waters, the oxygen exchange accelerates.

Impacts of Aerosol−Radiation Interactions on the Wintertime Particulate Pollution under Different Synoptic Patterns in the Guanzhong Basin,China

The effects of aerosol-radiation interactions(ARI)are not only important for regional and global climate,but they can also drive particulate matter(PM)pollution.In this study,the ARI contribution to the near-surface fine PM(PM_(2.5))concentrations in the Guanzhong Basin(GZB)is evaluated under four unfavorable synoptic patterns,including“northlow”,“transition”,“southeast-trough”,and“inland-high”,based on WRF-Chem model simulations of a persistent heavy PM pollution episode in January 2019.Simulations show that ARI consistently decreases both solar radiation reaching down to the surface(SWDOWN)and surface temperature(TSFC),which then reduces wind speed,induces sinking motion,and influences cloud formation in the GZB.However,large differences under the four synoptic patterns still exist.The average reductions of SWDOWN and daytime TSFC in the GZB range from 15.2%and 1.04°C in the case of the“transition”pattern to 26.7%and 1.69°C in the case of the“north-low”pattern,respectively.Furthermore,ARI suppresses the development of the planetary boundary layer(PBL),with the decrease of PBL height(PBLH)varying from 18.7%in the case of the“transition”pattern to 32.0%in the case of the“north-low”pattern.The increase of daytime near-surface PM_(2.5)in the GZB due to ARI is 12.0%,8.1%,9.5%,and 9.7%under the four synoptic patterns,respectively.Ensemble analyses also reveal that when near-surface PM_(2.5)concentrations are low,ARI tends to lower PM_(2.5)concentrations with decreased PBLH,which is caused by enhanced divergence or a transition from divergence to convergence in an area.ARI contributes 15%-25%toward the near-surface PM_(2.5)concentrations during the severe PM pollution period under the four synoptic patterns.

Research on quality changes and influencing factors of groundwater in the Guanzhong Basin

This paper studies the distribution features, the chemical elements beyond standards and the influencing factors of shallow groundwater quality in the Guanzhong Basin through the data monitored in the last twenty years. The final purpose is to comprehensively evaluate the divisions of groundwater quality in the Guanzhong Basin. Results show that, the groundwater quality is in good shape, and suitable for drinking. Drinking accounts for 16.02% of the total, most of which are distributed in the lubotan of Weibei. Some come from loess plateau of Qian-Liquan County and some are generated by the industrial pollution of Xingping City. Materials exceeding standards include chloride, sulfate, three nitrogen, fluoride, manganese, iron, hexavalent chromium and so on. The main factors influencing the quality of shallow groundwater include groundwater exploitation, natural background value of special components and precipitation, among which the groundwater exploitation poses the greatest impact. The depth of water is positively correlated with the concentration of sulfate, nitrate and total hardness.

Processes of hydrogeochemical evolution of groundwater in the Guanzhong Basin, China

This paper analyzed regional hydrogeochemical evolution characteristics of groundwater with respect to hydrogeological conditions in the Guanzhong Basin, China. Coefficient variation in the subregion between the Shichuan River and Luo River of the Guanzhong Basin is larger than other subregions, reflecting the more complicated hydrogeological conditions of this subregion. The hydrochemical components and hydrodynamic conditions of this area have distinct horizontal zoning characteristics, and hydrodynamic conditions play a controlling role in the groundwater’s hydrochemistry. The relationship between ions, and between ions and TDS（total dissolved solids） can give an indication of many charteristics of grounwater such as evaporation intensity, ion exchange, and the sources of chemical components. Results indicated that for the coefficient of variation（the coefficient of variation is a statistical measure of the distribution or dispersion of data around mean. This measure is used to analyze the difference of spread in the data relative to the mean value. Coefficient of variation is derived by dividing the standard deviation by the mean）, the minimum value of pH parameters is 0.03-0.07, the minimum value of HCO3-parameters is 0.24, while the maximum is the SO42-coefficinet at 1.67. A PHREEQC simulation demonstrated that different simulation paths roughly have the same trend in dissolution and precipitation of minerals. Along the direction of groundwater flow, the predminant precipitation is of calcite and gypsum and the cation exchange of Na+ and Ca2+ in some paths. However, in other paths, the precipitation of calcite and dissolution of gypsum and dolomite are the main actions, as well as the exchange of Mg2+ and Ca2+ in addition to Na+ and Ca2+.

LA-ICP-MS U-Pb Geochronology of Detrital Zircon in the Guanzhong Basin, China and Its Tectonic Response

Objective The Guanzhong Basin in the transitional zone of the Qinling orogenic belt and the southern margin of the Ordos Basin has been extensively studied in recent years.Although some results have been obtained,some problems such as whether the materials from the North China craton and the Qinling orogenic belt are detrital sedimentary rocks of the Guanzhong Basin still remain unresolved.

Heavy metal pollution from copper smelting during the Shang Dynasty at the Laoniupo site in the Bahe River valley,Guanzhong Basin,China

Heavy metal pollution is hazardous for the environment and human health.However,there are few studies of heavy metal pollution caused by historic metallurgical activity.The Laoniupo site in the Bahe River valley,Guanzhong Basin,China,was an important settlement of the Shang Culture(1600-1046 BCE).We studied two stratigraphic profiles at the Laoniupo site,which were used for measurements of magnetic susceptibility,heavy metal concentrations,and AMS 14C ages to provide evidence of copper smelting activity at the site during the Shang Dynasty.The Nemerow Pollution Index and Geoaccumulation Index were calculated to assess the heavy metals record(Cu,Zn,Ni,Pb,Cr,and As)in the topsoil on the loess tableland.According to the Single Pollution Index,the topsoil was slightly polluted by As and unpolluted by Cu,Zn,Ni,Pb and Cr;according to the Nemerow Composite Pollution Index the topsoil was mildly polluted;and according to the Geoaccumulation Index,the topsoil was moderately polluted by As,slightly polluted by Cu,and unpolluted by Zn,Ni,Pb and Cr_The main cause of the heavy metal pollution in the topsoil is the presence of copper slag in the cultural layers that was disturbed by modern farming activity.

关中盆地新石器时期水沟遗址人类活动与自然地理环境适宜性研究

本研究通过对关中盆地西部新石器时期水沟遗址人类活动的灰坑、文化层、房址、陶窑和陶器等遗迹、遗物做了详细的梳理分析,理解区域古人类活动的特征,系统地开展水沟文化层剖面环境磁学和AMS14C年代学研究,恢复该区全新世以来气候变化和古人类活动历史,结果表明:水沟新石器时期古人类活动时间为全新世中期5 530~4 300 a B.P.的气候适宜期,其文化发展处在寒冷干燥向温暖湿润转换的过渡阶段。在GIS空间分析技术支持下提取影响水沟遗迹分布的海拔、坡度、坡向和距水源距离因子,构建指数模型,分析新石器时期水沟遗址古人类活动的自然地理环境适宜性分布规律,主要集中在海拔900~960 m,坡度小于6°,坡向朝南,距水源距离小于200 m的自然环境条件优越的区域,并进一步探讨了古人类活动对环境变化的响应与适应的过程和机制。

关中盆地新近系泥岩地球化学特征:物源和古沉积环境恢复

目前关中盆地开发利用的地热资源主要为新生界砂岩、砂砾岩孔隙裂隙型地热资源,开发利用层位主要为新近系热储层。地热资源赋存特征、地热资源开发有利区展布、地热资源量等与物源、古沉积环境密切相关,查明关中盆地新近系泥岩物源和古沉积环境特征,有利于指示同沉积时期砂岩物源和古沉积环境特征,对于关中盆地地热资源的开发利用重点层位确定、有利区预测及资源量计算具有指导意义。沉积岩中的元素地球化学特征记录了重要物源和沉积环境信息。依据关中盆地新近系泥岩岩心样品主量、微量和稀土元素特征对物源和沉积环境进行了综合研究,研究结果表明:关中盆地新近系泥岩的源区构造背景主要为活动大陆边缘,源岩主要为关中盆地南缘太白岩体正长花岗岩、华山岩体黑云母二长花岗岩,含有一定的中—基性火成岩;化学蚀变指数(CIA)介于61.34~76.78之间,平均值为70.78,反映新近系泥岩经历了中等程度风化作用,指示高陵群和蓝田-灞河组沉积期处于暖湿气候环境,张家坡组沉积期气候发生了转型,由暖湿气候转变为冷干气候;地球化学指标综合反映,新近系泥岩沉积期主要处于还原环境,水体古盐度整体表现为淡水、半咸水环境。

关中盆地新近系蓝田-灞河组热储层物性及渗流特征研究

关中盆地地热资源丰富,开发利用地热能有助于调整能源结构、降低雾霾及改善环境。新近系蓝田-灞河组是目前地热开采的主要热储层,明确储层物性及渗流机理对地热资源的高效规模开发利用及回灌具有重要意义。通过钻井岩心及测井资料,结合压汞、铸体薄片、核磁共振等相关测试手段,对渭河盆地新近系主要层位蓝田-灞河组的物性特征、孔隙结构特征、渗流特征进行了详细分析。研究结果表明:①基于地热井及钻孔测井资料,西安凹陷蓝田-灞河组孔隙度为20%~25%,渗透率为100~200 mD,固市凹陷孔隙度为10%~20%,渗透率为1~100 mD,西安凹陷物性条件优于固市凹陷,在平面上孔渗均表现为由盆地边缘向盆地中部增大的趋势。②蓝田-灞河组孔隙以原生粒间孔、粒间残余孔隙为主,局部见少量微裂缝发育,见少量长石溶孔。孔喉分布比较均匀,主要介于10~16μm之间,渗透率贡献值高。出水量大,单位厚度砂岩单位涌水量高,富水性及渗流特征好。③蓝田-灞河组砂岩储层类型属于Ⅱ类储集层,综合评价为高孔隙度渗透层,是最有利的地热开发层段。

关中盆地蓝田—灞河组地热水化学特征及形成机制

采用水化学及同位素分析等方法对关中盆地蓝田—灞河组水文地球化学特征及形成机制进行了研究。结果表明:研究区地热水以Cl—Na和Cl—SO_(4)—Na—Ca型水为主,地热流体水化学由浅到深,从HCO_(3)·SO_(4)—Na型→SO_(4)·HCO_(3)—Na型→SO_(4)·Cl—Na型→Cl·SO_(4)—Na型→Cl—Na型,水化学类型由单一型向复合型过渡,最终演变为单一型Cl—Na型。研究区热储层温度较高,分布范围较宽,为40~105℃,大部分水样温度高于60℃,平均温度为72.8℃。pH值均大于7,属于弱碱性水;TDS(矿化度)普遍高于1 g/L。地下热水14 C年龄在7000~28000 a之间,从盆地南北两侧向中部逐渐变老,在盆地南北两侧存在地表水的补给。盆地中部新生界孔隙裂隙型地热流体的赋存环境相对封闭,盆地形成过程中早期地层的部分地下水由于新生代地层的快速沉降和堆积而在孔隙中封存,随着盆地的不断沉降和堆积,逐渐加压和封存了孔隙中的地下水。

关中地区十六国墓葬分布研究

关中地区十六国时期墓葬已发掘46处200余座,主要集中在长安城西北的咸阳石安原及南郊少陵原一带。这些茔地是以都城及居住地为中心集中分布,单点或多点成组出现;尤其是中、小型家族墓地占据了族群墓茔的大宗,个别族群茔地前后延续三百余年,人群属性特殊。高等级墓葬多分布于石安原,晚期(约后秦至北魏初年)在少陵原亦有发现,家族墓地多见于石安原、少陵原、高阳原。墓葬形制在沿袭“汉、晋”礼制的基础上,又增加了仿木结构的土雕门楼建筑。

关中盆地6000～2100cal.aB.P.期间黍、粟农业的植硅体证据

黍、粟是我国北方两种重要的旱作农作物,对中华文明起源和发展产生过重要的影响。长期以来由于受到考古样品保存及研究方法的限制,早期考古发掘报道的我国关中盆地新石器遗存的农作物多是以粟为主或粟、黍不分,统称粟类作物,缺少对该区新石器时期粟、黍农业状况的深入研究。本文利用植硅体方法,分别对现代黍、粟和水稻种子的植硅体产量以及关中盆地新石器考古样品中的植硅体进行分析。结果表明,等重量的黍、粟种子稃片的植硅体产量基本相等,其植硅体含量所反映的是黍、粟的相对产量(重量);水稻双峰型植硅体的百分含量比水稻实际含量相对偏低。关中盆地泉护、杨官寨、浒西庄、案板、王家嘴,水沟等6个考古遗址17个^(14)C年龄和47个植硅体样品分析结果显示,约6000～2100cal.aB.P.期间,关中盆地黍子的植硅体含量一直占优势(3.4%～34.5%),粟次之(0～6.2%),即使在气候相对暖湿的阶段,黍的产量仍超过粟。泉护、杨官寨、浒西庄,案板等遗址的个别样品中保存水稻植硅体。这些结果为重新认识关中地区新石器时期农业生产与社会经济形态以及与气候环境条件的关系提供了新的参考资料。

全新世黄土-古土壤序列色度特征及气候意义——以关中平原西部梁村剖面为例

利用K-MinoltaCR-400色度仪分别测试研究剖面土壤色度指标(亮度、红度和黄度),并与研究剖面其他常用气候替代指标磁化率、CaCO3和Rb/Sr比等进行对比分析,结果发现:红度和亮度指标对气候响应敏感,能够揭示全新世早中晚三个阶段千年尺度的季风演变和气候变化,对于次级变化即百年尺度的变化也有明显指示;红度指标对气候响应更为敏感,变化幅度大,波动多,有助于揭示气候的转折和弱成壤古土壤的存在,但也具有一定的气候局限性;亮度指标大致可揭示区域降水量的多少;黄度指标在本剖面对气候的响应有限.

关中盆地浅层地下水地球化学的形成演化机制

在对关中盆地浅层地下水169个水化学数据分析的基础上,运用图解法、数理统计法及Phreeqc模拟等方法对关中盆地浅层地下水水文地球化学形成演化机制进行系统研究,取得了一些新的认识。按含水介质及地下水循环特征,将浅层地下水系统大致划分为强烈径流区、缓慢径流区、排泄区。不同水动力分区中,地下水化学类型具有一定的分带性,从强烈径流区、缓慢径流区至排泄区,地下水的化学类型由HCO3-Ca·Mg型经过HCO3-Ca·Mg·Na型逐步演化为SO4·Cl-Na型。地下水强烈径流区,地下水化学组分的形成主要以碳酸盐、硅酸盐等矿物岩石风化作用为主,缓慢径流区以多种作用为主,排泄区由Na-Ca阳离子交换及蒸发浓缩作用控制。

关中盆地地下热水环境同位素分布及其水文地质意义

通过对关中盆地地下热水2H、18O、13C、14C、34S分布特征的研究,阐述了关中盆地腹部与其周边地区地下热水环境同位素异同现象及其水文地质意义,论证了关中盆地地下热水的补给循环及其赋存环境特征。研究表明:关中盆地地下热水中环境同位素δ(18O)、δ(D)、δ(13C)、δ(14C)、δ(34S)的分布除δ(D)外均呈现中部富集、周边贫化趋势,指示关中盆地腹部咸阳及西安城区1 500 m以下地下热水赋存环境相对封闭;地下热水滞留时间较长,以碳酸盐矿物溶解为主的水岩反应强烈,热储层中碳酸盐溶解对地热水中的HCO3-、δ(18O)、δ(13C)随深度增加趋势有明显贡献,δ(D)在盆地中部的贫化指示地下热水补给时的温度偏低,根据补给高程计算,西安、咸阳城区地下热水分别为秦岭和北山末次冰期雪水补给。

关中盆地秦岭山前地下水库调蓄功能模拟研究

本文从水资源开发利用与社会经济环境协调发展角度出发 ,分析研究了关中盆地秦岭山前地下水库调蓄条件下调蓄方式 ,依据野外实际调查测试的数据 ,利用有限元和有限分析数值模拟技术对地下水库的调蓄功能进行了模拟 ,在此基础上 ,对地下水库调蓄的效益进行了分析。得出关中盆地秦岭北坡地下水库调蓄条件优越 ,水量丰富 ,蕴藏着巨大的开发利用潜力 ,开展该区地下水库人工调蓄是挖掘水资源潜力、增大可供水量和涵养地下水源、改善生态环境的重要途径 ,对维持黄河流域地下水可再生性 ,缓解黄河断流有重要意义。

陕西关中盆地中部地下热水H、O同位素交换及其影响因素

对关中盆地地下热水δ18O和δD数据的研究表明:盆地中部西安、咸阳深部的地压地热流体发生明显的18O同位素交换,并出现2H同位素交换,表明热储流体发生了强烈的水岩反应,盆地周边及中部的非地压地热流体18O交换则不明显。根据研究区18O同位素的交换程度(用2H过量参数d表征)和水化学资料,可将关中盆地热储流体分为循环型和封闭型热储流体2类。地热水埋深越大、滞留时间越长、TDS和温度越高、地质环境越封闭,18O交换程度就越大。西安和咸阳地下热水分属于不同的地热系统,具有不同的补给来源。