Sedimentary and diagenetic features in saline lake deposits of the Monegros region, northern Spain

The Monegros region in northern Spain is marked by the occurrence of a large number of ephemeral to dry lake basins, occupying small karstic depressions. The lacustrine sediment fill of these basins contain various carbonate and silicate minerals whose origin and palaeoenvironmental significance is poorly understood. For the present study, 14 lake basins were sampled in order to establish vertical, lateral and regional variations in mineralogical and textural characteristics, aimed at determining the mode of formation of the various mineral phases present. In nearly all basins, the same sequence of three lithological units is recognized, including a basal clayey unit, a middle magnesite-bearing and gypsum-rich unit, and a calcite- and dolomite-dominated surface unit. Distribution patterns of carbonate minerals indicate that magnesite is a synsedimentary precipitate, dolomite formed as a diagenetic authigenic phase, and calcite is partly authigenic and partly allogenic. All clay minerals, including sepiolite and smectite, appear to be allogenic. Regional variations are marked by similarities between groups of neighbouring basins, but no overall trend related to regional drainage patterns is recognized. The middle lithological unit records a lake stage with predominantly chemical sedimentation (Unit II), overlying a less well documented interval corresponding to a perennial lake stage with lower salinity (Unit III), whereas the surface unit formed during a period with predominantly clastic sedimentation. Based on a comparison with other regional records, the middle unit is attributed to an Early Holocene humid stage, separated from the overlying Late Holocene deposits by a hiatus that corresponds to a Mid Holocene arid stage.     

Assessment of Bacterial and Fungal Aerosol in Different Residential Settings

The concentration and size distribution of bacterial and fungal aerosol was studied in 15 houses. The houses were categorized into three types, based on occupant density and number of rooms: single room in shared accommodation (type I), single bedroom flat in three storey buildings (type II) and two or three bedroomed houses (type III). Sampling was undertaken with an Anderson six-stage impactor during the summer of 2007 in the living rooms of all the residential settings. The maximum mean geometric concentration of bacterial (5,036 CFU/m³, ± 2.5, n?=?5) and fungal (2,124 CFU/m³, ± 1.38, n?=?5) aerosol were in housing type III. The minimum levels of indoor culturable bacteria (1,557 CFU/m³, ±1.5, n?=?5) and fungal (925 CFU/m³, ±2.9, n?=?5) spores were observed in housing type I. The differences in terms of total bacterial and fungal concentration were less obvious between housing types I and II as compared to type III. With reference to size distribution, the dominant stages for culturable bacteria in housing types I, II and III were stage 3 (3.3–4.7 μm), stage 1 (7 μm and above) and stage 5 (1.1–2.1 μm), respectively. Whereas the maximum numbers of culturable fungal spores were recovered from stage 2 (4.7–7 µm), in housing type I, and from stage 4 (2.1–3.3 μm) in both type II and III houses. The average geometric mean diameter of bacterial aerosol was largest in type I (4.7 μm), followed by type II (3.89 μm) and III (1.96 μm). Similarly, for fungal spores, type I houses had the highest average mean geometric diameter (4.5 μm), while in types II and III the mean geometric diameter was 3.57 and 3.92 μm, respectively. The results indicate a wide variation in total concentration and size of bioaerosols among different residential settings. The observed differences in the size distributions and concentrations reflect their variable airborne behaviour and, as a result, different risks of respiratory exposure of the occupants to bioaerosols in various residential settings.     

Coastal wetland vegetation features and digital Change Detection Mapping based on remotely sensed imagery: El-Burullus Lake,Egypt

El-Burullus Lake is one of the four Egyptian Ramsar sites that constitute internationally important wetlands as they contain a rich biodiversity and have a large number of water bird species. But the valuable resources in El-Burullus Lake and its surrounding area have faced various threats to wetlands over recent decades. This study was carried out to evaluate the dynamics of land cover change using three change scenes of recent and past satellite data from 1990 to 2019. The study utilized ArcGIS10.7, ERDAS Imagine 14, Landsat TM (1990, 1999, and 2010), Landsat OLI-TIRS (2019) to analyze the land-use/land-cover (LULC) of El-Burullus wetland. Normalized Difference Vegetation Index (NDVI) and Normalized Difference Water Index (NDWI) were employed to assess the change scenario of the area. Results indicated that vegetated land has increased significantly with a concomitant shrinkage in the water body and open soil during the study period. Approximately 53 km² (7.0%) of water body and 8.7 km² (1.3%) of open soil were lost, while vegetation areas expanded to approximately 29.9 km² (7.4%). Factors that underpin the observed changes in the area are; reclamation projects and fish-farms which are creating the danger of drying up of the southern coastal parts of the lake, as well as spreading of reed beds (mainly: Phragmites australis) that covers about 20% of El-Burullus lake which led to dry up the lake parts. Therefore, the study suggests the need for urgent attention on conservation of remaining wetland resources for sustainable utilization for the next generation.     

Soil chronosequence and biosequence on old lake sediments of the Burdur Lake in Turkey

The Burdur Lake is located in the southwest of Turkey, and its area has decreased by 40% from 211 km² in 1975 to 126 km² in 2019. In this study, we investigated how the soil has changed in the lacustrine material. Three soil profiles were sampled from the former lakebed (chronosequence profiles: P1, 2007; P2, 1994; and P3, 1975), and three soil profiles under different land use types (biosequence profiles: P4, native forest vegetation; P5, agriculture; and P6, lakebed) were sampled. The chronosequence and biosequence soil profiles represented various distances from the Burdur Lake and showed different stages of lacustrine evolution. Soil electrical conductivity (EC; 18.1 to 0.4 dS m_-1), exchangeable Na⁺ (34.7 to 1.4 cmol kg^-1) and K⁺ (0.61 to 0.56 cmol kg^-1), and water-soluble Cl^- (70.3 to 2.1 cmol L^-1) and SO₄^2- (275.9 to 25.0 cmol L^-1) decreased with increasing distance from the Burdur Lake, whereas the A horizon thickness (10 to 48 cm), structure formation (0 to 48 cm), gleization-oxidation depth (0 to 79 cm), and montmorillonite and organic matter (OM; 25.9 to 46.0 g kg^-1) contents increased in the chronosequence soil profiles. The formation of P3 in the chronosequence and P5 in the biosequence soil profiles increased due to longer exposure to pedogenic processes (time, land use, vegetation, etc.). Changes in EC, exchangeable cation (Na⁺ and K⁺) and water-soluble anion (Cl^- and SO₄^2-) concentrations of the salt-enriched horizon, OM, gleization-oxidation depth, A horizon thickness, and structure formation of the chronosequence and biosequence soil profiles (especially the topsoil horizon) were highly related to the distance from the Burdur Lake, time, and land use.     

Status of tiger and leopard in Rajaji-Corbett Conservation Unit, northern India

Rajaji-Corbett Tiger Conservation Unit (RCTCU), in northern India, is one of the 11 Level-I Tiger Conservation Units (TCU) identified in the Indian subcontinent for the long-term conservation of the tiger. This TCU of about 7500 km² stretches from the Yamuna River in the west to Sharda River in the east and includes portions of the Outer Himalaya and the Shivalik hills. Little less than one third of this TCU comes under protected area status (Rajaji National Park—820 km², and Corbett Tiger Reserve—1286 km²) and the rest are under 12 reserve forest divisions, five of which have largely been converted into monoculture plantations. Between November 1999 and March 2000, we evaluated the status of tiger and leopard in RCTCU by counting the number of different pug marks on 3-5 km transect walks along 52 dry stream beds (‘raus’), for a total distance of 479 km in these reserve forests and plantations. People and cattle seen along the transects, were also counted, as an index of disturbance. In this TCU, the tiger occurs in three isolated populations: between the west bank of River Ganges and River Yamuna, from the east bank of Ganges to Kathgodam-Haldwani-Lalkuan Highway and between the Highway and River Sharda. Owing to increasing biotic pressures, the tiger has become rare in Rajaji-Corbett corridor and has become extinct in four divisions. There is a growing threat of further degradation and fragmentation of its habitat. To implement a recovery programme, we suggest several management measures such as control of poaching, resettlement of local tribes (gujjars) and five villages, creation and strengthening of forest corridors, conversion of monocultures into polyculture plantations and establishment of several mini-core areas including Nandaur Valley National Park. We recommend the reliable and user-friendly method used by us to evaluate and monitor the status of leopard and tiger in this conservation unit. A suggested Greater Corbett Tiger Reserve (2000 km²) should be kept as inviolate as possible.     

Caesium-137 dating applied to slackwater flood deposits of the Llobregat River, NE Spain

During a palaeoflood study of the Llobregat River (NE Spain), analysis of ¹³⁷Cs was carried out on slackwater flood deposits to obtain an improved flood chronology for the most recent flood sediments. At the Monistrol study reach, ¹³⁷Cs was measured in flood deposits preserved in valley side rock alcoves, with a range of ¹³⁷Cs concentrations of 2.80–10.06 mBq/g measured. The ¹³⁷Cs was associated with sediment mobilised from the upstream catchment by erosion and transported to the alcoves during floods. The onset of measured caesium activity in the sedimentary profiles permitted the deposits to be divided between those from floods that occurred before the mid-1950s and those from events after this period. Combining the information derived from the slackwater flood stratigraphy, the minimum discharge estimates associated with the flood deposits, ¹³⁷Cs analysis and the instrumental peak discharge series, it was possible to identify the particular flood events responsible for the majority of the slackwater flood units. At Vilomara, however, ¹³⁷Cs activity was measured in palaeoflood deposits dated to the Late Bronze Age and located at an elevation not reached by the floodwaters of the largest modern events. The data from this site indicated that the ¹³⁷Cs was not associated with sediments transported by floods but was rainfall-derived, the rainwater reaching the deposits through fissures in the rock. To ensure the successful application of caesium dating to slackwater flood deposits preserved within rock alcoves, or caves, some general guidelines are proposed. The technique is best applied: (1) when there is a sedimentary profile of greater than 1 m depth; (2) when the profile is sampled away from zones affected by direct percolation or springwater entering the alcove; and (3) where there are various levels of contrasting textures within the profile.     

Chemistry of soft-water seepage lakes in the upper midwest: Lacustrine alkalinity production in summer

A total of 26 soft-water, seepage lakes in the Northern Highlands (NH) of Wisconsin (N =16) and the Upper Peninsula (UP) of Michigan (N=10) were sampled four times between early May and mid October 1984 as part of the ‘PIRLA’ Project (Paleolimnological Investigations of Recent Lake Acidification). Because of low antecedent recharge of the local water-table, this ‘summer’ interval likely featured minimal groundwater inputs (<2 cm over lake surface) to most of these seepage lakes. Based on this hydrogeologic relationship, and on regional deposition data, I evaluated short-term net epilimnetic (June–August) and whole-lake (May–October) sediment-water exchange of ANC, base cations, acid oxy-anions, Al, DOC and silicic acid in these lakes using a simplified mass balance algorithm. Silica, nitrate and ammonium were all efficiently retained in these seepage lakes. The assimilation of NO₃ ^? (19±4 meq m^?2) slightly exceeded assimilation of NH₄ ⁺ (16±4), resulting in a net internal ANC production of only +3 meq m^?2 over 161 d between early May and mid October 1984. Over this same interval ANC production resulting from lacustrine S retention averaged +35±8 meq m^?2 in the NH, but was too variable to be statistically significant (+21±21 meq m^?2) in the UP. Epilimnetic S retentions in mid summer were more comparable (21±4 in NH; 14±5 meq m^?2 in UP). McNearney Lake (UP) illustrates how high sulfate, linked to low alkalinity, high Al, low P, and low productivity, can become a negative correlate of lacustrine S retention. Temporal changes in base cations in the 26 lakes were generally small and erratic compared with uncertainties in deposition inputs and analytical errors, rendering estimates of related ANC production inconclusive. Even small analytical biases can be critical when designing and interpreting lake monitoring studies.     

供水工程影响下中国北方地区耕地后备资源开发潜力

灌溉水源是北方地区耕地后备资源能否有效开发的关键。当前,中国正在推动国家水网工程规划建设,为北方地区耕地后备资源开发提供了新的机遇。在以往研究基础上,该研究考虑北方地区已建、在建及规划的供水工程,基于自然适宜、利用高效、发展稳定三方面评价准则,结合三维魔方空间分类方法,开展了雨养情景和供水灌溉情景下耕地后备资源开发潜力分析。结果表明：雨养农业情景下,北方地区勉强适宜（Ⅱ级）、中度（Ⅲ级）和高度（Ⅳ级）适宜的耕地后备资源面积分别为2.9万、1.0万和0.6万km²。灌溉农业情景下,耕地后备资源面积明显增加,勉强适宜（Ⅱ级）、中度（Ⅲ级）和高度（Ⅳ级）适宜的耕地后备资源面积将分别达到5.4万、7.6万和6.5万km²,主要集中于新疆、内蒙古和甘肃3省（自治区）。该研究结果可为中国耕地后备资源开发利用及国家水网工程效益发挥提供参考。     

Use of landslide-dammed lake deposits and pollen tracing techniques to investigate the erosional response of a small drainage basin in the Loess Plateau, China, to land use change during the late 16th century

A major landslide that occurred in 1569 in the Huangtuwa gully catchment within the Rolling Loess Plateau region of China, resulted in the creation of a landslide-dammed lake at the outlet of the small 0.1 km² tributary valley of the Houxiaotan Gully. All the sediment transported to the outlet of this catchment was deposited in the lake. After about 30 years the dam failed and the lake deposits were dissected as the stream cut down to its former base level. Substantial remnants of the sediment deposits that accumulated over the ca. 30 year period are, however, preserved as terraces near the outlet of the catchment and a vertical section through these sediment deposits was investigated using stratigraphic and pollen tracing techniques. Individual flood couplets could be clearly distinguished and these permitted the establishment of a chronology for the sediment deposits and the estimation of the sediment yields associated with individual events and individual years. Pollen analysis undertaken on samples collected from the individual flood couplets also provided information on the variation of the pollen content of the sediment and the proportion of Artemisia pollen during the period represented by the deposits. Interpretation of the information assembled from the sediment section has made it possible to reconstruct the erosional history of the Houxiaotan catchment during the 31 year period following the landslide. The average sediment yield of the catchment in the late 16th century was very similar to its present-day sediment yield. The sediment yield from the catchment and the relative contribution of the inter-gully areas, as compared to the gully system, declined immediately after the landslide as a result of abandonment of the cultivated land within the catchment. The restoration of cultivation in the catchment after about 17 years resulted in an increase in sediment yield from ca. 9000 t km^− 2 yr^− 1 to ca. 30,000 t km^− 2 yr^− 1 and a substantial increase in the proportion of sediment contributed by the cultivated inter-gully areas. Scope exists to apply a similar approach to the sediment deposits that accumulated in other former landslide-dammed lakes within the Rolling Loess Plateau region of China, in order to develop an improved understanding of the erosion history of the region.     

基于GIS的延河流域滑坡崩塌地质灾害空间分布及其引发因素分析

[目的]以更符合滑坡崩塌发生发展规律的延河流域为例,进行地质灾害空间分布及引发因素分析研究,为防灾减灾提供依据。[方法]依据区县地质灾害详细调查资料,建立GIS地质灾害数据库,包含地理数据、基础地质数据、地质灾害点数据和栅格数据。统计分析坡度、坡高、坡型、河谷发育期等引发因素;选取坡度、坡型、植被、河谷地貌、地层、降雨量、道路距离、居民点8因素,采用加权信息量法进行地质灾害易发性分区阐述地质灾害空间分布。[结果]坡高50~100m,坡度30°~45°易形成滑坡;老年河谷灾害点密度为壮年期的2倍,幼年期的3倍;凸型和直线型斜坡更容易产生滑坡和崩塌灾害,阶梯型和凹陷型斜坡稳定程度明显增高。延河流域滑塌高易发面积1 664.96km2,灾害点密度0.29处/km2;中易发3 102.02km2,密度0.10处/km2;低易发3 888.99km2,密度0.04处/km2。[结论]以流域为单位进行地质灾害研究,引发因素、空间分布规律更为明显,指导防灾减灾更加实用。     

Use of landslide-dammed lake deposits and pollen tracing techniques to investigate the erosional response of a small drainage basin in the Loess Plateau,China, to land use change during the late 16th century

A major landslide that occurred in 1569 in the Huangtuwa gully catchment within the Rolling Loess Plateau region of China, resulted in the creation of a landslide-dammed lake at the outlet of the small 0.1 km² tributary valley of the Houxiaotan Gully. All the sediment transported to the outlet of this catchment was deposited in the lake. After about 30 years the dam failed and the lake deposits were dissected as the stream cut down to its former base level. Substantial remnants of the sediment deposits that accumulated over the ca. 30 year period are, however, preserved as terraces near the outlet of the catchment and a vertical section through these sediment deposits was investigated using stratigraphic and pollen tracing techniques. Individual flood couplets could be clearly distinguished and these permitted the establishment of a chronology for the sediment deposits and the estimation of the sediment yields associated with individual events and individual years. Pollen analysis undertaken on samples collected from the individual flood couplets also provided information on the variation of the pollen content of the sediment and the proportion of Artemisia pollen during the period represented by the deposits. Interpretation of the information assembled from the sediment section has made it possible to reconstruct the erosional history of the Houxiaotan catchment during the 31 year period following the landslide. The average sediment yield of the catchment in the late 16th century was very similar to its present-day sediment yield. The sediment yield from the catchment and the relative contribution of the inter-gully areas, as compared to the gully system, declined immediately after the landslide as a result of abandonment of the cultivated land within the catchment. The restoration of cultivation in the catchment after about 17 years resulted in an increase in sediment yield from ca. 9000 t km^− 2 yr^− 1 to ca. 30,000 t km^− 2 yr^− 1 and a substantial increase in the proportion of sediment contributed by the cultivated inter-gully areas. Scope exists to apply a similar approach to the sediment deposits that accumulated in other former landslide-dammed lakes within the Rolling Loess Plateau region of China, in order to develop an improved understanding of the erosion history of the region.     

修正的通用土壤流失方程中各因子单位的确定

[目的]明确和规范修正的通用土壤流失方程(RUSLE)中各因子的单位,使得RUSLE在中国具体应用过程中更加科学和便捷。[方法]通过对国内外RUSLE应用实践的总结和对比研究,并分析其科学合理性,找出最为普遍应用的、准确的RUSLE各因子的单位,明确不同单位类型之间的转化系数。[结果]国内RUSLE的应用,大部分是通过各地区建立的各因子统计模型转换成国际制单位系统,最后相乘得到的是以国际制单位表示的土壤侵蚀量,另一部分则是通过相应的各因子统计模型计算得到各个因子以美制单位系统表示的计算结果,最后再乘以224.2将土壤侵蚀量转换为国际制单位。国内主流侵蚀估计中使用的单位焦耳系统,单位面积有两种即km^2和hm^2。土壤流失量A常用的国际制单位为t/hm^2或t/km^2;降雨侵蚀力因子R常用的国际制单位为(MJ·mm)/(hm^2·h·a)或(MJ·mm)/(km^2·h·a);土壤可蚀性因子K的常用国际制单位为(t·hm^2·h)/(hm^2·MJ·mm)或(t·km^2·h)/(km^2·MJ·mm)。不同地区建立的计算方法通过相应的转换系数转换成国际制单位。最后,R和K因子的单位系统的一致性是RUSLE应用的关键步骤。[结论]R和K因子通过相应的单位转换系数转换为国际制单位以及两者的单位一致性是土壤侵蚀评估的重要基础。     

THE MECHANISM OF PHOSPHATE ADSORPTION BY KAOLINITE, GIBBSITE, AND PSEUDOBOEHMITE

The adsorption isotherms (20°C) of phosphate on two potassium kaolinites and two aluminium oxides have been determined at pH values from 3 to 10 and at concentrations ranging from 10^?4 to 10^?2M. The reversibility of the adsorption with respect to pH and concentration has also been examined. The isotherms result from at least three types of adsorption site (regions I, II, and III) of widely different reactivities. The number of adsorption sites increases to a limit with decrease in pH for regions I and II. The behaviour of region III is more complex. The different adsorbents behave in essentially the same manner and differ only in the number of adsorption sites. It is tentatively suggested that regions I and II are located on an edge –Al(OH)₂ of the adsorbents, while region III results from penetration into some amorphous region of the crystal surface.     

基于不同模型不同指纹因子的东北黑土区小流域泥沙来源分析

基于指纹识别技术计算了东北黑土区典型小流域不同侵蚀产沙源地的泥沙贡献比。通过分析农地、林地、草地表层土以及侵蚀沟样品中的33种物质,使用非参数检验和多元判别分析筛选出包括P、Ce、Ga、Rb和137Cs组成的最优复合指纹因子,并将放射性核素137Cs和210Pbex作为第2组指纹因子,将最优复合指纹因子中的单个因子分别作为单因子,作为第3组指纹因子,分别利用多元混合线性模型、Bayesian模型和单因子解析解等泥沙来源指纹分析方法计算了表层土和侵蚀沟的相对泥沙贡献比。结果表明:基于不同模型不同指纹因子的泥沙来源贡献比结果虽不尽相同,但无重大差别。利用多元混合线性模型计算时,由放射性元素137Cs和210Pbex作为指纹因子计算的泥沙来源(表层土47.5%,侵蚀沟52.5%),与最优复合指纹因子计算的泥沙来源(表层土44.6%,侵蚀沟55.4%)基本一致;利用Bayesian模型计算时,由放射性元素137Cs和210Pbex作为指纹因子计算的表层土和侵蚀沟的泥沙贡献比约各占1/2,而利用最优复合指纹因子计算得到的泥沙贡献比中,表层土(58.8%)多于侵蚀沟(41.2%);以复合指纹因子中单个因子为指纹因子计算解析解,P、Ga、Ce、137Cs 4个因子的判别能力较强,能有效判别泥沙物源区;为保证泥沙贡献比计算结果的精确性,有必要确定各模型的计算精度,并挖掘具体的影响因素,调整参数或算法,为模型改进提供依据。研究发现,面积占比不足1%的侵蚀沟贡献了流域近1/2的泥沙,表明侵蚀沟发育引起的土壤流失不容小觑,应加强对该区侵蚀沟道的治理。     

望谟县特大山洪泥石流灾后重建分区与功能定位

贵州省黔西南自治州望谟县灾后重建关系到灾区群众的切身利益和长远发展,必须全面贯彻落实科学发展观,坚持以人为本,尊重自然,科学规划,合理布局,要立足灾区实际,做好重建分区与功能定位.在灾区范围内根据流域的生态环境背景,通过对其资源环境承载能力进行综合评价,充分考虑其国土开发强度、产业发展方向以及人口集聚和城镇建设的适宜程度,对其指标体系进行分层聚类,以定量为主,定性为辅进行生态环境建设分区,同时兼顾行政单元的完整性,将灾区范围国土空间分为生态保护区(面积376.07 km2)、适度重建区(面积716.06 km2)、适宜发展区(面积407.47 km2),分析其功能定位,使管制原则与城镇建设更趋于合理,为灾后重建的规划布局工作提供理论支撑.     

Late Quaternary alluvial fans and paleosols of the Kangra basin,NW Himalaya: Tectonic and paleoclimatic implications

The paper describes Late Quaternary pedosedimentary sequences of the alluvial fans from the Kangra basin of NW Himalayas for tectonic and paleoclimatic implications. In the proximal part of the Kangra basin three coalescing alluvial fans, namely Rait-Rihlu fans (~ 65 km²), Kangra fans (~ 200 km²), and Palampur fans (~ 170 km²) from west to east evolved due to reactivation of longitudinal and transverse faults and climatic changes during the Late Quaternary. The fans are characterised by subsidence of Rait-Rihlu fans, uplift of Kangra fans and tilting of Palampur fans. The thick (~ 90 m) pedosedimentary sequences exposed along the rivers characterise the dominant formative processes over the fans. The stream flow sediments dominate the Rait-Rihlu fans, whereas the debris flow sediments dominate the Kangra and Palampur fans. The fan sequences are also marked by the formation of strongly developed paleosols on loess (L1–L3 loess paleosols) and weakly developed paleosols on fluvial deposits in response to the tectonics and climate change in NW Himalayas.     

Adirondack headwater lake chemistry relationships with watershed characteristics

The Adirondack Region of New York State has been identified as having surface waters sensitive to acidic deposition and as receiving large annual inputs of acidic deposition. The large amount of data available for this region makes a quantitative study of the region possible. Compiled from a variety of sources, the Adirondack Watershed Data Base (AWDB) contains information on lake chemistry; lake elevation, area, and volume; and associated watershed data, such as size, slope, aspect, elevation, vegetation and wetland types, beaver activity, fire and logging history, and soils data. Bivariate and multivariate procedures were used to examine relationships between watershed attributes and lake chemistry. Because the variables in the data base are being refined and modified, the current relationships should be considered preliminary. Preliminary results indicate that wet deposition, lake elevation, and forest cover are the principal variables that are associated with variance in the data for lake pH and acid neutralizing capacity (ANC) in the Adirondacks. For headwater lakes in the Adirondacks, we estimate approximately 50% have a total ANC ≤ 40 μeq L^?1 and 40% have a pH ≤ 5.5.     

The influence of paleofloods on archaeological settlement patterns during A.D. 1050–1170 along the Colorado River in the Grand Canyon,Arizona, USA

Excavations at four archaeological sites consisting of the material remains of A.D. 1050–1170 era farmers along the Colorado River in Grand Canyon National Park, yield geomorphic information used to address questions related to settlement patterns. Archaeological excavation units, test pits, feature fill, and natural exposures contain sediments used to interpret geomorphic history that can, in turn, shed light on archaeological site selection in a challenging environment. The Grand Canyon experiences dramatic geomorphic events such as catastrophic floods and destructive debris flows that are preserved in the stratigraphic record, and can be used to understand cultural/landscape interactions. By combining new geomorphic, stratigraphic, and archaeological data collected during recent excavations with results from previous geomorphic and sediment transport studies, observed trends can be interpreted regarding the possible influence of paleofloods on past settlement patterns. For example, at each of the four sites, reconstructed paleoflood elevations (from existing HEC-RAS virtual shorelines), flood recurrence intervals, site layout, and site stratigraphy/geomorphic setting suggests a temporal trend in site location. The two early sites (Early Pueblo II period: A.D. 1050–1080) contain habitation features located above the approximately 6–8 year high flood (3500 cubic meters per second [cms]) recurrence interval; larger floods (4800 to 5900 cms) of a longer recurrence interval between 40 and 80 years inundate these features. The two later sites in the sample (Late Pueblo II; A.D. 1080–1170) contain habitation features located well above the 40–80 year recurrence high flows. We suggest that early farmers (Early Pueblo II period: A.D. 1050–1080) may not have had adequate experience with flood magnitudes and frequencies and therefore their habitation structures were located in risk-prone areas relatively close to the river. Later habitations (Late Pueblo II; A.D. 1080–1170) were positioned in more protected areas further from the river, perhaps reflecting an acquired knowledge of river dynamics. These trends, although currently based on a limited data set, provide insights into site selection decisions and settlement patterns of early farmers along the Colorado River through Grand Canyon.     

红壤区稀土矿开发导致河流泥沙淤积量的估算--以江西省信丰县崇墩沟小流域为例

不合理的人为活动是侵蚀产沙的主要原因之一。在江西省信丰县崇墩沟小流域内由于稀土矿产的无序开发,导致河流泥沙严重淤积。通过实测河流淤积泥沙断面,计算出在7 500 m长的河道共淤积泥沙30 193 t,考虑到输移比,整个流域内土壤流失量可达3 500 t/km2,平均侵蚀模数也高达1 150 t/(km2.a)以上,属于中等强度的土壤侵蚀。调查结果发现,河流中淤积的泥沙主要来源于稀土矿开发的尾矿流失;土壤流失量高到99 730 t/km2,年平均侵蚀模数为34 000 t/(km2.a)以上,属于极强度的水土流失。治理水土流失,须加强对稀土矿开发的管理,防止形成新的水土流失;将已废弃的稀土尾矿作为治理的重中之重,可有效地降低流域内土壤侵蚀的强度。