Dust transportation and deposition in a superhumid environment,West Coast,South Island,New Zealand

Contemporary rates of dust deposition monitored along a 300-km section of the superhumid West Coast of New Zealand's South Island are presented. In this setting, dust is entrained primarily from the dry channels of braided glaciofluvial rivers that drain the western slopes of the Southern Alps. Measured dust deposition ranged between 0.21 and 118.9 kg⁻¹ ha⁻¹ month⁻¹, which is similar to dust deposition rates monitored in arid and semiarid environments. However, these are not considered to be sufficient for present day loess genesis. Dust deposition was highest in summer because of the greater frequency of favourable dust transporting winds, and the effect of rainfall was secondary. Dust transportation occurred mainly during the passage of nonprecipitating cold fronts or postfrontal southwesterlies. Transportation also occurred during prefrontal conditions, and in winter föhn southeasterlies were the predominant dust transporting winds to affect the West Coast.     

Predicting watershed acidification under alternate rainfall conditions

The effect of alternate rainfall scenarios on acidification of a forested watershed subjected to chronic acidic deposition was assessed using the model of acidification of groundwater in catchments (MAGIC). The model was calibrated at the Panola Mountain Research Watershed, near Atlanta, Georgia, U.S.A. using measured soil properties, wet and dry deposition, and modeled hydrologic routing. Model forecast simulations were evaluated to compare alternate temporal averaging of rainfall inputs and variations in rainfall amount and seasonal distribution. Soil water alkalinity was predicted to decrease to substantially lower concentrations under lower rainfall compared with current or higher rainfall conditions. Soil water alkalinity was also predicted to decrease to lower levels when the majority of rainfall occurred during the growing season compared with other rainfall distributions. Changes in rainfall distribution that result in decreases in net soil water flux will temporarily delay acidification. Ultimately, however, decreased soil water flux will result in larger increases in soil-adsorbed sulfur and soil-water sulfate concentrations and decreases in alkalinity when compared to higher water flux conditions. Potential climate change resulting in significant changes in rainfall amounts, seasonal distribution of rainfall, or evapotranspiration will change net soil water flux and, consequently, will affect the dynamics of the acidification response to continued sulfate loading.     

Rain,snow and lake water chemistry on and near the Precambrian Shield of Western Canada

Regional surveys of rain, snow and lake water chemistry have been conducted in several locations of western Canada which are considered sensitive to acidic deposition and are within several hundred kilometres of major Canadian point source emitters (664,000 tonne S0₂ in 1981). Snow and rain in the western Precambrian Shield is acidic with pH values generally ranging between 5.0 and 6.4. However, there is little evidence to suggest that the area is receiving significant amounts of acidic deposition. Total deposition of sulphate is approximately 2 kg ha^?1 between the months of April to October in 1983. Environmental impacts at present are minimal with most small lakes in the region having pH values near nuetrality and low concentrations of metals such as Al.     

Metal pollutants in agricultural soils and the St. Louis urban rainfall anomaly

The existence of a rainfall anomaly downwind of the St. Louis urban-industrial areas prompted a survey of area soils for elevated heavy metal concentrations. The goals of this work were to measure concentrations of Zn, Cd, and Ph, and to evaluate the role of the urban rainfall anomaly in their accumulation, in potentially-affected soils. Samples from three soil layers were collected from agricultural fields at 21 sites along two NE-SW transects. The samples were analyzed for pH, texture, cation exchange capacity, and total organic carbon, in addition to the three metals. The highest metal concentrations were observed near Granite City, Illinois, and coincided with an area of maximum Zn deposition in rain found in an earlier study. Only slight increases of the metals over background were found in the area of rainfall anomaly. Present rates of atmospheric deposition can account for these slightly elevated metal concentrations. However, the maximum concentrations found near Granite City cannot be accounted for by present atmospheric deposition rates. Other kinds of sources, or larger atmospheric deposition rates, perhaps during the operation of a local Zn smelter which closed about 1960, must have contributed.     

云南干热河谷不同坡面整地方式对土壤水分环境的影响

云南干热河谷高温少雨．水土流失严重，土壤水分严重亏缺，人工植被“土壤干化”现象严重。通过在坡面采用不同的整地方式．对微地形进行塑造，强化降雨入渗．结果表明，不论是雨季还是早季，水平台和水平沟整地后，水平台、台间坡面、水平沟、沟间坡面的土壤水分环境均比同一等高水平上自然坡面好，旱季水平台和水平沟与自然坡面的差距从分水岭到坡脚逐渐减小，雨季差距最大值出现在坡的中部．水平台整地后，西坡的含水率比北坡和南坡高。在一定的坡度范围内，坡度越缓．水平台整地改善土壤水分的效果越明显．偏粘性土壤水平台整地后，改善土壤水分环境的效果要比偏沙性的土壤好，水平台和水平沟整地后，增加了水分在土壤中蓄存的时间．对植物的吸收利用非常有利。     

冻融期温带草地土壤呼吸和土壤异养呼吸的日变化特征及对水氮添加的响应

探讨冻融期土壤呼吸和土壤异养呼吸如何响应降雨变化和氮沉降增加,对于准确预估未来全球变化背景下陆地生态系统土壤碳动态有着重要意义。选择内蒙古温带典型草地开展增雨和氮沉降增加野外模拟实验,分析水氮变化条件下冻融期土壤呼吸及土壤异养呼吸的日变化特征。冻融期,土壤呼吸及土壤异养呼吸通量（CO₂排放速率）最大值出现在温度最高的午后或是土壤发生冻融后的早晨,最小值则出现在昼夜内温度最低的时间段。在秋季和春季两个昼夜观测日期内,水氮增加对呼吸通量的促进效应均不显著（P > 0.05）,但却促使土壤呼吸累积通量分别增加了约145 mg m?2和70 mg m?2。由于异养呼吸在土壤呼吸中占比高（> 70.3%）,因此,这两个观测时段内,水氮增加促使土壤异养呼吸日累积通量增加的值与土壤呼吸增加的值十分接近。呼吸通量与土壤水分、氮含量以及5 cm和10 cm地温的相关性不显著（P > 0.05）,与气温和表层地温的相关性显著,且呈现显著的一元二次非线性拟合关系（P < 0.01）,其中,气温可以解释呼吸通量日变化的53% ~ 84%。温度是控制呼吸通量日变化的主要因子,水氮添加在昼夜观测尺度上对土壤呼吸和土壤异养呼吸的日累积通量的促进效应不容忽视。     

Quantification of In Situ Denitrification Rates in Groundwater Below an Arable and a Grassland System

Growing season rain and cloud events were sampled between 1984–2010 at Lakes of the Clouds (LOC) (1,540 m above sea level (ASL)) which is 1.6 km SW of the summit of Mount Washington, NH (1,914 m ASL). Mount Washington's summit is in the clouds ca. 51 % of the time. All samples were measured for pH, while cations and anions were measured consistently from 1996 to 2010. Annual mean cloud and rain water hydrogen ion concentrations declined significantly from 1984–2010. Nighttime cloud and rain hydrogen, sulfate, ammonium, and nitrate ion concentrations were significantly greater compared to daytime. Ion mean concentrations declined over the 1996–2010 timeframe and more rapidly since 2005. Co-located filter-based aerosol measurement (PM_2.5) at LOC had higher ratios of ammonium to sulfate in summer daytime samples post (1995–2010) full implementation of the 1990 Clean Air Act Amendments. This suggests a shift towards more neutralized sulfate aerosol dissolution into clouds with relatively more ammonium and declines in acidity. The origin of cloud water sampled, which ranges from regional fronts to orographic lower elevation air mass uplift, along with the diurnally shifting nocturnal boundary layer that often puts the LOC site in and out of the mixed layer, likely contributes to the diurnal and inter-annual variability observed.     

ACID DEPOSITION DURING TWO CONTRASTING FRONTAL RAINFALL EVENTS

Analysis of the chemical composition of rain at high temporal resolution provides additional information on wet deposition processes. High resolution data was obtained using a microprocessor-based acid rain monitor at two sites in SW Scotland and SE England. Meteorological details of the transport and wet deposition processes during two frontal rain events were examined and related to rainfall composition. Rapid depletions of ion concentrations during heavy rainfall in the first event were interpreted using a rainfall scavenging model. The sub-event data for the second event showed the influence of frontal discontinuities. Increasing ionic concentrations during this second event were attributed both to the change in air mass, and to diminished upwind precipitation scavenging.     

黄土丘陵区林地干化土壤降雨入渗及水分迁移规律

基于近年来黄土丘陵区林地形成大规模土壤干层的事实,为了探索降雨在黄土丘陵区枣林地干化土壤中的入渗、迁移规律,明确干化土壤的修复能力,在陕北米脂试验站建立野外10m大型土柱模拟枣林地干化土壤,采用CS650—CR1000土壤水分自动监测系统对其进行连续定位观测。观测数据分析表明:(1)独立降雨的入渗、迁移深度主要取决于降雨量,大、中、小雨的水分影响深度分别达90~140,70~80,40cm,降雨量一定时还与降雨强度、初始土壤含水量等因素有关,降雨强度越大、初始土壤含水量越高,水分的入渗深度及迁移深度也越大。(2)间歇降雨中几次降雨交互对水分的入渗、迁移产生促进作用。相同雨量下,其入渗深度较独立降雨可提高100%~160%,迁移深度可提高91%~197%。(3)黄土丘陵区并非所有降雨都对土壤水分有影响。观测期内降雨次数与降雨量的有效率分别为36.4%和72.7%。(4)土壤垂向剖面在多次降雨的累积作用下具有层次性,本试验期间降雨影响范围内的土壤剖面主要可以分为3层,0—90cm为降雨入渗敏感层,90—160cm为降雨入渗迟缓层,160—240cm为雨水迁移层。研究结果对于促进黄土丘陵区林地干化土壤的治理与修复,加强土壤水分的科学管理与改善具有重要的理论和实践意义。     

全膜双垄沟不同覆膜时期对玉米土壤水分和产量的影响

针对甘肃省旱作农业区年降水量少、季节分布不均匀、玉米生产中春旱严重的问题,采用田间试验的方法研究了全膜双垄沟4种不同覆膜时期对旱地玉米生育时期、土壤水分变化、水分利用效率、产量及经济效益的影响。结果表明:秋覆膜优于早春顶凌覆膜、玉米播前覆膜和晚春播种时覆膜,即早覆膜优于晚覆膜。全膜双垄沟秋覆膜增加了降水利用率和水分利用效率,降水利用率为70.21%,产量为10039.34kg/hm2,比播前覆膜8036.67kg/hm2增产24.92%,水分利用效率36.01kg/hm2·mm,比播前覆膜27.10kg/hm2·mm提高32.88%。全膜双垄沟秋覆膜可明显减少冬春季土壤水分的无效蒸发,增产效果明显,是旱作区进一步挖掘降水潜力和高产田创建的有效途径。     

Atmospheric sulfur deposition for a red soil broadleaf forest in southern China

A two-year study in a typical red soil region of Southern China was conducted to determine 1) the dry deposition velocity (Vd) for SO2 and particulate SO4^2- above a broadleaf forest, and 2) atmospheric sulfur fluxes so as to estimate the contribution of various fractions in the total. Using a resistance model based on continuous hourly meteorological data, atmospheric dry sulfur deposition in a forest was estimated according to Va and concentrations of both atmospheric SO2 and particulate SO2^4-. Meanwhile, wet S deposition was estimated based on rainfall and sulfate concentrations in the rainwater. Results showed that about 99% of the dry sulfur deposition flux in the forest resulted from SO2 dry deposition.In addition, the observed dry S deposition was greater in 2002 than in 2000 because of a higher average concentration of SO2 in 2002 than in 2000 and not because of the average dry deposition velocity which was lower for SO2 in 2002. Also,dry SO2 deposition was the dominant fraction of deposited atmospheric sulfur in forests, contributing over 69% of the total annual sulfur deposition. Thus, dry SO2 deposition should be considered when estimating sulfur balance in forest ecological systems.     

辽西风沙半干旱区旱作农田水资源研究

辽西风沙半干旱区年降水量多为二、三年左右的丰枯交替,并有持续4年以上的连续干旱,尤其是1980年以后连续干旱的年份较多。区域内春旱严重,夏季降水明显集中,秋季水分收支基本平衡。以土壤水分季节变化情况可分为:冬季土壤水分凝聚、冻结、累积阶段,春季解冻、返浆、土壤水分大量蒸散阶段,夏季土壤水分大量累积阶段,秋季土壤水分缓慢蒸发阶段。     

蒸发与降水入渗过程中不同水体氢氧同位素变化规律

为了研究土壤水蒸发与降水入渗非饱和带过程中不同水体氢氧同位素的变化规律,该文选用2种不同性质的土壤-砂土和黄土,设计了土壤水蒸发和降水入渗室内试验。结果表明:对于砂土,土壤水蒸发过程中剩余水体氢氧同位素分馏遵从瑞利模式;对于黄土,随着蒸发时间的延长,剩余土壤水氢氧同位素值越来越远离瑞利分馏关系线;在降水入渗非饱和带的初期,相对于风干砂土,风干的黄土颗粒对土柱出流水的氢氧同位素值产生了影响,并且出流水的氢氧同位素亦受到土壤原水同位素值的影响,只有入渗的降水达到了一定数量,土柱出流水才能与降水的同位素值相同。该研究可为运用氢氧同位素研究降水能否通过非饱和带补给地下水提供数据分析的依据。     

A comparison of bulk and wet-only precipitation collectors at rural sites in the United Kingdom

Co-Located wet-only and bulk precipitation collectors have been used to measure precipitation amount and ionic composition at nine rural sites in the United Kingdom. The wet-only collector collects less rain, particularly at more exposed, windier sites. This is believed to arise primarily from aerodynamic blockage rather than from late opening of the collector at the onset of rain. In general, agreement between the two types of collector for ionic composition is good. However, at two sites which experience low rainfall and elevated concentrations of primary and secondary pollutants in easterly airflow, the bulk collector yields larger concentrations of non-marine sulphate. Measurements of particulate sulphate suggest that dry deposition of particles is sufficient to explain the observed differences. In contrast, larger ammonium concentrations are measured with the wet-only collector. The observations are consistent with loss of ammonium from the bulk collector, particularly at sites of low annual mean acidity. These differences are greater in summer than in winter suggesting a biological loss mechanism.     

Tillage practices for soil and water conservation in the semi-arid zone I. Management of fallow during the rainy season preceding cotton

Field and laboratory experiments were conducted on a crusting loess soil in the northern Negev (Israel) with the aim of improving the efficiency of the use of rain by row crops, either in dryland or irrigated farming, and to decrease erosion. The specific objective of the experiments described was to develop methods that enhance infiltration of rainfall during the winter fallow season in an area with a mean annual rainfall of 400 mm which is subject to wide variation.It was found that the traditional tillage system consisting of deep ploughing (35–45 cm) of dry soil in the fall followed by disking, smoothing and ridging is the worst choise as it could result in runoff losses of as much as 60% of the rainfall, accompanied by accelerated erosion. This water loss can be critical to the success of dryland cotton and also determines whether or not a pre-irrigation of about 25% of the total annual water allotment must be given to irrigated cotton.The traditional practice was compared with: deep ploughed land left fallow during the entire rainy season; ridging after subsoiling instead of deep ploughing; subsoiling and ridging carried out in one minimum tillage operation; direct ridging without primary tillage and basin tillage of ridges following either deep ploughing, subsoiling or minimum tillage.This study showed that by far the most effective method for enhancing infiltration and eliminating runoff was the basin tillage system. The method is adaptable both to mechanized farming and to farming based on animal power or manual labour, and its application can ensure success where rainfall is limiting.It was found that laboratory characterization of soil hydraulic properties with a static rainfall simulator allows prediction of runoff on crusting soils. This means that the need for, and the effectiveness of, conservation measures may be estimated using disturbed soil samples, which is quicker and cheaper than field tests.     

皇甫川流域水利水保工程减沙效益分析

皇甫川流域,50年代降雨量、径流量和产沙量偏丰,80年代偏枯,70年代暴雨次数多、雨量大、雨强高。采用“水保法”计算,水利水保工程平均每年减沙444.7万t,占多年于均产沙量的7.9%;采用“降雨-产沙公式法”计算,平均每年减沙276～332万t,约占多年平均产沙量的5％。水利水保工程起到了减沙作用。为进一步减少入黄泥沙,今后仍需继续加强流域综合治理工作。     

The application of210Pb inventories in soil to measure long-term average wet deposition of pollutants in complex terrain

The radionuclide²¹⁰Pb derived from gaseous²²²Rn is present in particle form in the atmosphere attached to the same aerosols which contain the bulk of the pollutant sulphur and nitrogen. When scavenged from the atmosphere by precipitation, the²¹⁰Pb is readily attached to organic matter in the surface horizons of soil. The inventory of²¹⁰Pb in soil can be used to measure the spatial variation in wet (or cloud) deposition within a region due to orography or land use, averaged over several decades (half life of²¹⁰Pb is 22.3 years). Measurements of soil²¹⁰Pb inventories along a transect through complex terrain in north Britain were made to quantify the orographic enhancement of wet deposition, at Great Dun Fell in Cumbria. At the hill summit (～800m asl) precipitation of approximately 2000 mm year^?1 exceeds that on the low ground upwind by a factor of 2.0. The inventory of²¹⁰Pb increases along the same transect by a factor of 3.3, due to seeder-feeder scavenging of orographic cloud. The measurements show that the average ratio of concentrations in scavenged orographic cloud to rain upwind of the hills is 2.2. These data are entirely consistent with the studies of the variation in major ion concentration with altitude at Great Dun Fell and elsewhere. The modelling procedures developed to provide estimates of wet deposition throughout the UK uplands are shown to be consistent with these new field data.     

Organic Acids in the Atmosphere and Bulk Deposition of Hong Kong

Results from the first study in Hong Kong, Southern China, to investigate the concentrations of organic acids in bulk deposition, aerosol and gas phase samples are presented. 57 daily bulk deposition samples were collected in central Kowloonand analyzed by ion chromatography, from May 1999 to May 2000. The volume-weighted (vw) mean concentrations for formate, acetate, propanoate and oxalate were 6.1, 4.5, 0.4 and 1.4 μeq dm^-3, respectively, with vw mean pH being 4.65.The maximum acidity contributions by formic and acetic acidsfor bulk deposition samples collected on a daily basis, withpH < 5.0, were 17 and 14%, respectively. The concentrationsof these acids were significantly correlated with each other, butnot with pH. Higher organic acid concentrations were foundin the dry, winter season, and for the synoptic weather systemtypes: approaching cyclone and cold front. Oxalate levels weregenerally higher in bulk deposition samples for north/northeasterly air masses, higher surface windspeeds, and low rainfall amounts. Formic and acetic acids were present at higher concentrations in the gas phase (mean concentrations at two sites were in the range from 3.2 to 6.5 μg m^-3, with formate usually < acetate), than in aerosols (mean concentration of formate, acetate or oxalate ≤2.2 μg m^-3). Higher levels of organic acids both in aerosols and in the gas phase were found at a busy roadside site than at a residential site. Deposition fluxes for formic and acetic acidsare reported.     

Wet and Dry Deposition Fluxes of Polychlorinated Biphenyls (PCBs) in an Urban Area of Turkey

Atmospheric polychlorinated bihenyls (PCBs) deposit by dry and wet deposition mechanisms, and therefore they constitute a significant polluting source for lands and surface waters. Various samplers have been used to determine the PCB pollution level resulting from deposition. In the presented study, a modified wet deposition sampler (WDS) was used for sampling both wet and dry deposition samples with the same instrument by which wet deposition reservoir of the WDS is opened and dry deposition reservoir is closed when rain starts. Wet and dry deposition samples were collected between June 2008 and June 2009. In the samples taken from BUTAL which is known as an urban area with heavy traffic, ??PCB dry deposition fluxes were determined as 18?±?10 ng/m²??day, and wet deposition fluxes for dissolved and particle phase were measured as 480?±?1,185 and 475?±?1,000 ng/m²??day, respectively. The dissolved and particle-phase PCB concentrations in rain were 10?±?13 and 13?±?14 ng/l, respectively. The contribution of wet deposition to total PCB deposition was determined as 52%. PCB concentrations in the ambient air were measured to be 370?±?200 and 20?±?20 pg/m³ for gas and particle phases, respectively. Washout ratio was determined by proportioning rain concentration to concentration in air. The washout ratios of the samples were between 1,675?C311,800 and 12,775?C2,511,120 for dissolved and particulate phases, respectively.     

苏南丘陵区毛竹林坡面土壤水分对降雨的响应

[目的]研究苏南丘陵区毛竹林涵养水源机制,降低由于毛竹集约经营而导致水土流失的影响。[方法]选取南京市铜山林场的毛竹林,采用ECH2O土壤含水率检测系统于2012年6月5号至2013年8月28号以每0.5h监测1次的频率在坡面土壤深度为10,15,40,60cm的4个深度层次进行土壤水分定位监测,分析了不同降雨强度条件下苏南丘陵区毛竹林地各土壤层次水分变异过程,得到各土壤层次体积含水率变化过程对降雨强度的响应曲线,并提出侧向流以及分析其对不同雨强的响应特征。[结果]10,15cm层次土壤含水率变化趋势与降雨量变化趋势具有一致性,40,60cm层次土壤含水率的峰值相对延迟0.5~1.5h;小雨条件下,土壤含水率的变化幅度自表层到40cm土层呈现逐渐减小的趋势,中雨和大雨条件下,15—60cm层次土壤含水率的变化幅度表现出随深度增加而增大的趋势,大雨条件下此趋势更加明显;小雨、中雨和大雨条件下最大侧向流分别为10.17,60.26和95.92mm。[结论]随着深度的增加,土壤含水率与降雨量的同步性呈现下降趋势;不同雨强条件下各层土壤含水率的变化幅度存在明显差异;降雨入渗表现为非饱和入渗,每场降雨垂直面上都有不同程度的侧向流存在,主要集中在40—60cm层次,其主要受土壤结构和降雨强度的影响。