Wastewater Reuse for Alfalfa Production in the Gaza Strip

Geography, population growth, and politics combine to make the Gaza Strip a worst-case scenario for water resource planners. Potable water sources are shrinking while at the same time, the proportion of potable water used for irrigation is increasing. To assess whether water from wastewater treatment plants could be safely used for irrigation, this study collected 51 treated wastewater, 51 sludge, 44 soil, 30 alfalfa, and 24 oranges and lemon samples and analyzed the samples for major and trace elements. Both Inductively Coupled Plasma - Optical Emission Spectroscopy (ICP/OES) and X-ray fluorescence (XRF) were used for the determination of Ag, Al, As, B, Ba, Br, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Mg, Mn, Na, Ni, P, Pb, Rb, Se, Sr, Zn, Zr, Th, and U in digested and solid samples, respectively. Treated wastewater characteristics showed a very good agreement with the guidelines of many developed countries. Moreover, none of the tested parameters in soil showed concentrations exceeding their corresponding background values. For alfalfa, both ICP/OES and XRF showed Zn concentrations in leaves (36–42 mg/kg, respectively) higher than in root (19–31 mg/kg, respectively). The Cu showed also the same trend as Zn. No significant variation was observed between the concentrations of Cr and Mn in plant parts; concentrations of Co and Pb were two times higher in roots than in leaves and stems. The findings confirm that treated wastewater is safe to use for irrigation in Gaza. Collecting and reclaiming this water can contribute to wise use of each drop of water available.     

Occurrence,Degradation and Fate of Pesticides During Composting

This paper reviews the findings of research reported in the currently available literature regarding the occurrence and transformations of pesticides through the composting process and the use of compost. Part I summarizes the composting process, pesticides and mechanisms of pesticide degradation. Part II reviews research studies concerning the occurrence and fate of pesticides during composting. Investigations of pesticide residues in composting feedstocks and finished compost detected few of the target pesticides. The compounds that were found occurred at low concentrations. The majority of the compounds detected were insecticides in the organochlorine category, including chemicals that have been banned from use in the U.S. for many years. Generally, organophosphate and carbamate insecticides and most herbicides were rarely detected. Comparisons of pesticide concentrations before and after composting also showed organochlorine compounds to be most resistant to biodegradation during composting. With some exceptions, pesticides in other categories decomposed moderately well to very well. Studies that followed the mechanisms of degradation indicate that mineralization accounts for only a small portion of pesticide disappearance. Other prominent fates include partial degradation to secondary compounds, adsorption, humification, and volatilization. In general the research results suggest that the pattern of pesticide degradation during composting is similar to the degradation observed in soils. With a few important distinctions, composting can be considered a biologically active soil environment in which degradation is accelerated. However, as some studies noted, composting does not always speed the degradation of all pesticides. The nature of the pesticide, specific composting conditions and procedures, the microbial communities present, and the duration of composting affect the extent and the mechanisms of degradation.     

Literature Review: Occurrence,Degradation and Fate of Pesticides During Composting: Part II: Occurrence and Fate of Pesticides in Compost and Composting Systems

This paper reviews the findings of research reported in the currently available literature regarding the occurrence and transformations of pesticides through the composting process and the use of compost. Part I summarizes the composting process, pesticides and mechanisms of pesticide degradation. Part II reviews research studies concerning the occurrence and fate of pesticides during composting. Investigations of pesticide residues in composting feedstocks and finished compost detected few of the target pesticides. The compounds that were found occurred at low concentrations. The majority of the compounds detected were insecticides in the organochlorine category, including chemicals that have been banned from use in the U.S. for many years. Generally, organophosphate and carbamate insecticides and most herbicides were rarely detected. Comparisons of pesticide concentrations before and after composting also showed organochlorine compounds to be most resistant to biodegradation during composting. With some exceptions, pesticides in other categories decomposed moderately well to very well. Studies that followed the mechanisms of degradation indicate that mineralization accounts for only a small portion of pesticide disappearance. Other prominent fates include partial degradation to secondary compounds, adsorption, humification, and volatilization. In general the research results suggest that the pattern of pesticide degradation during composting is similar to the degradatiion observed in soils. With a few important distinctions, composting can be considered a biologically active soil environment in which degradation is accelerated. However, as some studies noted, composting does not always speed the degradation of all pesticides. The nature of the pesticide, specific composting conditions and procedures, the microbial communities present, and the duration of composting affect the extent and the mechanisms of degradation.     

3种烟碱类杀虫剂在土壤中的降解吸附特性及对地下水的影响

采用室内模拟实验方法,以太湖水稻土、江西红壤和东北黑土为代表性土壤,研究了噻虫啉等3种烟碱类杀虫剂在土壤中的降解、吸附特性,并利用GUS（Ground Ubiquity Score）指数分析了其对地下水污染的影响。结果表明,3种烟碱类杀虫剂在3种土壤中均较易降解,降解半衰期在5～31d之间,属于易降解农药,降解特性与土壤理化性质及农药本身性质有关。3种烟碱类杀虫剂在江西红壤、太湖水稻土与东北黑土中的吸附较好地符合Freundlich方程,Kd值在0.30～14.70之间,KOC在42.8～1750.9之间,属难吸附农药。吸附性强弱与农药本身溶解性和土壤有机质含量有关,水溶性越强吸附越弱,有机质含量越高,吸附性越强。3种烟碱类杀虫剂在太湖水稻土中的GUS值均小于1.8,而在江西红壤中,其GUS值均大于1.8,这3种杀虫剂在江西红壤中均有一定的淋溶性,对地下水均有一定的污染风险。     

Occurrence and Geochemistry of Arsenic in Groundwater of Punjab,Northwest India

Abstract

Arsenic (As) is a deadly poison at high concentrations. It is mysterious in the sense that people are exposed to it most of the time through drinking groundwater, fortunately at much lower concentrations than the deadly levels, and usually without knowing it. Arsenic content in alluvial aquifers of Punjab varied from 3.5 to 688 µg L^?1. Arsenic status of groundwater is classified into low (<10 µg L^?1), moderate (≥10 to <25 µg L^?1), high (≥25 to <50 µg L^?1), and very high (>50 µg L^?1). In zone I, the concentration of As in groundwater varied from 3.5 to 42 µg L^?1 with a mean value of 23.4 µg L^?1. On the basis of these limits, only 8% of samples were low, whereas 51 and 41% of the total samples collected from this region fall in the moderate and high As categories. The concentration of As in groundwater of zone II varied from 9.8 to 42.5 µg L^?1 with a mean value of 24.1 µg L^?1. Arsenic concentration in the alluvial aquifers of the central plain of zone II is 2 and 52% in the low and moderate limits. In this region, 46% of groundwater sites contain high As concentrations. Arsenic concentrations in the aridic southwestern parts are significantly different from other two provinces. The As concentration ranged from 11.4 to 688 µg L^?1 with average value of 76.8 µg L^?1. Eleven percent of the aquifers of the southwestern region of zone III are in the moderate category, 54% in the high, and 35% in the very high. According to safe As limits (<10 µg L^?1), only 3 and 1% of the groundwater samples collected from zones I and II were fit for dinking purposes with respect to As content. In the aridic southwest, zone III, all water samples contained As concentrations greater than the safe limits and thus are not suitable for drinking purposes. The presence of elevated As concentrations in groundwater are generally due to the results of natural occurrences of As in the aquifer materials. The concentration of other competitive oxyanions in waters such as phosphate, sulfate, and borate also depressed the adsorption of As on the sorption sites of aquifer materials and thereby eventually elevate the As concentration in groundwaters. In groundwater of alluvial aquifers of Punjab, released from sulfide oxidation and oxyhydroxide of iron, elevated (>10 µg L^?1) concentrations of As were widespread because of high pH (>8.0) and higher concentrations of phosphate, borate, sulfate, and hydroxyl anions. It is conclusively evident that geochemical conditions, such as pH, oxidation–reduction, associated or competing ions, and evaporative environments have significant effects on As concentration in groundwater. These conditions influence how much As is dissolved or precipitated into the water and how much is bound to the aquifer materials or the solid particles in water.     

Occurrence of PPCPs at a Wastewater Treatment Plant and in Soil and Groundwater at a Land Application Site

Pharmaceuticals and personal care products (PPCPs) can reach soil and aquatic environments through land application of wastewater effluent and agricultural runoff. The objective of this research was to assess the fate of PPCPs at field scale. PPCPs were measured systematically in a wastewater treatment plant (WWTP), and in soil and groundwater receiving treated effluent from the WWTP. A land application site in West Texas was used as the study site; it has received treated wastewater effluent from the WWTP for more than 70 years in order to remove additional nutrients and irrigate non-edible crops. Target compounds (estrone, 17??-estradiol, estriol, 17??-ethynylestradiol, triclosan, caffeine, ibuprofen, and ciprofloxacin) in wastewater, sewage sludge, soil, and groundwater were determined using HPLC/UV with qualitative confirmatory analyses using GC/MS. Samples were collected quarterly over 12 months for wastewater and sludge samples and over 9 months for soil and groundwater samples. Results indicated that concentrations of PPCPs in wastewater influent, effluent, sludge solid phase, and sludge liquid phase were in the range of non-detected (ND)-183 ??g/L, ND-83 ??g/L, ND-19 ??g/g, and ND-50 ??g/L, respectively. Concentrations in soil and groundwater samples were in the range of ND-319 ng/g and ND-1,745 ??g/L, respectively. GC/MS confirmation data were consistent with the results of HPLC/UV analyses. Overall, data indicate that PPCPs in the wastewater effluent from the WWTP transport both vertically and horizontally in the soil, and eventually reach groundwater following land application of the effluent.     

小麦/蚕豆间作系统中施氮对小麦氮营养及条锈病发生的影响

小麦/蚕豆间作在云南较普遍,而条锈病是小麦的主要病害.为研究小麦氮营养及条锈病发生,在云南玉溪和陆良两地同时布置田间试验,在小麦单作(Wm)、小麦/蚕豆间作(Wi)和小麦/蚕豆间作且覆膜隔根(Wp)3种植方式中对小麦设0、150、300kg· hm-2(分别N0、N150、N300)3个氮水平处理,测定了小麦叶片氮含量和条锈病病情指数,结果表明:(1)不论是单作小麦(Wm)还是间作小麦(Wp或Wi),施氮(N150和N300)比不施氮(N0)都显著提高了小麦叶片氮含量,但N150与N300间小麦叶片氮含量差异不显著;综合Wm、Wp、Wi不同种植方式,两地小麦叶片氮含量都随施氮量增大而显著提高(P＜0.0001),N150、N300分别比N0提高了52.7％、74.1％,N300比N150提高了14.0％.(2)在相同氮用量下,Wm、Wp、Wi间的小麦叶片氮含量只在玉溪点N0条件下Wp和Wi比Wm有显著提高(增加52.3％),而玉溪点N150、N300以及陆良点N0、N150、N300下都没明显差异.(3)施氮对小麦条锈病的影响在玉溪和陆良两地表现不同,在玉溪,施氮对小麦条锈病病情指数有增加作用,小麦条锈病病指与叶片氮含量间呈显著正相关;而在陆良,不同种植方式下N150和N300的小麦条锈病病指比No都有显著降低,N150与N300间差异不显著,小麦条锈病病指与叶片氮含量间的最优回归曲线显示小麦条锈病病指先随叶片氮含量升高而显著降低,达最低点后,又随叶片氮含量升高而呈增加趋势.(4)Wp和Wi发病中期的小麦条锈病病指相比Wm降低了10.9％,但发病盛期时降低微弱.总的结果表明,在本田间试验条件下,小麦蚕豆间作只在缺氮时对小麦氮营养有改善作用,小麦蚕豆间作相对单作对小麦条锈病有一定的控制效果,但小麦蚕豆根系相互作用对小麦氮营养及小麦条锈病病指无明显影响;氮肥施用显著改善了小麦氮营养,小麦条锈病发生既受氮营养的影响,又可能与品种特性、种植方式、环境条件等多因素有关.     

生产建设项目表土保护与利用

表土富含有机质、土壤酶和微生物等物质,具有较好的营养和环境条件来供应和协调植物生长;然而,随着经济的快速发展,各类生产建设项目扰动地表,导致大量表土被占压和流失,威胁生态安全和粮食安全。《中华人民共和国水土保持法》《开发建设项目水土保持技术规范》等法律、规范对生产建设项目表土保护与利用做了明确规定,生产建设活动应尽量减少地表扰动,对无法避免扰动的地区应进行表土剥离;但是,目前生产建设项目表土保护与利用存在建设单位保护意识不强、法律不健全、技术不完善等问题,相关政府部门应尽快确立有效的表土剥离补偿机制,将表土剥离作为水土保持方案的审查要点,同时加强表土剥离工艺等技术的研究。通过综述国内外现有的表土保护和利用成熟经验及科学方法,旨在为以后生产建设项目减少扰动、合理利用表土提供借鉴。     

河北省表层土壤可侵蚀性K值评估与分析

利用河北土系调查成果中的土壤颗粒组成、土地利用及土壤化学性质等资料,利用EPIC模型中土壤可蚀性K值算法以及结合地统计学方法,研究了不同土壤类型、不同质地及不同土地利用类型的土壤可侵蚀性K值和土壤可侵蚀性K值的空间变异特征。结果表明:1河北土壤可侵蚀性K值平均为0.27,其变化范围为0.12~0.40,土壤可蚀性K值在0.30~0.35之间易蚀性土壤面积占总土地面积的63.71%,土壤可蚀性K值在0.25~0.3之间较易蚀性土壤面积占总土地面积的21.52%,这说明该省易蚀性土壤面积较大。2不同质地的K值之间显著性差异,粉砂黏壤质的可侵蚀性K值最大,为0.37;壤砂质的可侵蚀性K值最小,为0.13。而在不同的土地利用类型之间的K值差异性不显著,耕地的K值最大,为0.33;草地的K值最小,为0.22。3河北土壤可侵蚀性K值存在较强的变异性,其变异系数为29%。因此,在土壤侵蚀定量监测、评价水土流失时,应考虑土壤可蚀性K值的这种空间变异状况。块金值/基台值为37.3%,表明在变程内具有中等强度的空间相关性。步长为23 km,变程为440 km,变程远大于步长,表明在小流域尺度下有较好的空间相关性,进行Kriging插值能得到较准确的结果。4河北土壤可蚀性K值大体呈现南高北低的空间分布特征,南部主要是耕作栽培区,北部主要是自然植被区。该研究结果为宏观大尺度土壤资源可持续利用与制定水土保持规划提供科学依据。     

青海省表层土壤属性数字制图

对于土壤景观复杂的大区域,样点往往较为稀疏,如何准确地进行土壤预测制图仍是一个需要研究的问题。本文以青海省为研究区,基于近年采集205个土系调查点数据,采用随机森林模型,分别建立了表层(0～20 cm)土壤全氮、有机碳、粉粒含量和pH四个基本土壤属性与环境协同变量(海拔、坡度、地形湿度指数、年降水量、年平均气温、归一化植被指数、地表温度和地表反射率)之间的定量关系模型,对该地区进行了土壤多要素预测制图,分析了影响土壤空间变异的控制性因素。交叉验证结果显示,全氮、有机碳、粉粒含量和pH的R~2分别是0.61、0.53、0.47和0.54,这说明随机森林模型可解释47%以上的土壤空间变异。表层土壤全氮和有机碳空间分布趋势东南高,西北低,pH呈现出相反的空间模式;粉粒含量东高西低,预测结果高值出现在柴达木盆地和南部玉树、果洛地区。环境变量的重要性分析表明,年降水量对表层土壤全氮、有机碳、pH空间分布模式具有控制性影响,夜间地表温度与表层土壤粉粒含量空间变异具有较强的协同关系。     

江苏表层土壤有机碳密度和储量估算和空间分布分析

基于1:50万的江苏土壤图和江苏土壤的数据,运用地理信息系统技术,对江苏表层土壤有机碳密度及储量做出估算,并且分析了土壤有机碳密度的空间分布差异。结果表明:土壤有机碳密度介于4.2kgm-2到20.32kgm-2之间,土壤有机碳储量为673892.8×106kg;土壤有机碳密度具有高度的空间变异性,兴化、南通和无锡的有机碳密度最高,沿海地区的有机碳密度比较高,最低的为淮阴及其附近地区。     

川西地区表土磁学性质及其环境意义

通过对川西地区表土样品进行系统的岩石磁学分析,并且结合气候要素探讨表土磁学性质与环境要素之间的关系。结果表明:(1)川西表土在成土过程中生成的细粒超顺磁(SP)和单畴(SD)的亚铁磁性矿物是磁化率增强的主导因素。该地区表土磁性增强机制与黄土高原类似。(2)在空间上,川西高原西部和南部地区的磁性矿物含量要高于东部和北部地区,而成都平原西部地区成土作用最强,磁颗粒细且含有较多高矫顽力磁性矿物。(3)川西表土的磁学参数和气候要素的研究发现年平均降水量(MAP)在600～1000 mm之间磁化率、频率磁化率与MAP呈正相关关系,而磁学参数组合χ_(fd)%/HIRM、ARM/HIRM、χ_(ARM)/SIRM与MAP在这一降雨区间也呈正相关关系,然而这些磁学参数与MAP的相关系数不如黄土高原,可能与研究区复杂的地形、相对湿润的成土条件有关。     

Source Identification and Speciation of Metals in the Topsoil of the Khli Ti Watershed, Thailand

The enrichment factor, multivariate analysis and metal speciation studies were used to identify degree, source and dispersal of metal contamination in Khli Ti watershed, Thailand. Topsoil samples were collected throughout the watershed, analyzed for total metal concentration. Sequential extraction was also carried out to determine geochemical phases of metals which were identified as exchangeable and bound to carbonates, Fe–Mn oxides, organic matter and residuals. Soil characteristics including pH, total organic carbon, redox potential, cation exchange capacity and texture were also analyzed. Principal component analysis yielded three metal groups which explained 83% of the variance. The concentrations of metals which were derived from lithogenic origin, such as Co, Cr, Fe, Ni and V were in natural background levels and were mostly bound to the residual phase. The remaining elements (i.e. Ba, Cd, Cu, Pb, Sb and Zn) were associated with the contamination from previous activities of the Pb-ore concentrator and Zn–Pb mining. Anthropogenic contamination mainly increased Pb and Zn bound to Fe–Mn oxides at the expense of residual fraction. Even though low exchangeable Pb contents in Khli Ti soils indicated low availability to plants, Pb bound to Fe–Mn oxides fraction might increase its mobility under reducing conditions.     

沈阳市耕地表土层厚度与耕地产能关系研究

表土对于作物生长至关重要,表土层厚度影响着耕地产能的大小,然而二者之间的关系尚缺乏具体的研究,明晰耕地表土层厚度与耕地产能之间的关系,对于提升耕地产能促进耕地质量提升具有重要意义。当前大量耕地被建设占用,表土遭到破坏,研究表土厚度与耕地产能间的函数关系,促进表土资源的保护与利用是十分必要与紧迫的。本研究以沈阳市浑南区、康平县等四区三县市为研究区,对研究区内耕地土壤质地、灌排能力、化肥使用强度、表土层厚度、有机质含量、耕作方式、耕地产能等情况进行实地调查,获得调查样点数据491份。通过统计分析方法确定影响耕地产能的其他因素的稳定水平,筛选出只有表土层厚度作为自变量样本点容量,运用非线性回归方法构建函数方程分析表土层厚度与耕地产能间的关系。结果表明:在表土层厚度在5 cm至24.5 cm之间时,表土层厚度与耕地产能存在对数函数关系,所构建函数方程为y=5144.6 ln(x)-2995.2(5≤x≤24.5);耕地产能随表土层厚度增加逐渐增加,在表土层厚度为24.5 cm时,耕地产能达到最高为13960.59 kg hm-2;对表土层厚度薄的耕地进行表土层厚度增加,耕地产能提高效果更加明显。     

滕州表层土壤硒异常特征及来源分析

为确定影响滕州地区表层土壤硒含量变化的因素,对研究区土壤的地球化学指标进行统计分析,结果显示,研究区土壤硒背景值为0.08mg/kg,异常下限值为0.17 mg/kg,表层土壤硒平均含量为0.23 mg/kg,标准差为0.144 mg/kg,变异系数为62.6%。综合相关性分析、主成分分析以及富集因子分析结果,表明表层土壤硒异常主要受人为因素的影响。不同区域表层土壤硒含量由高到低依次为煤矿区交通繁忙区农田区。在土壤垂直方向上,煤矿周边土壤中硒含量自下而上增加的趋势要明显快于不受煤矿直接影响的区域,同时前者的变化速率和转折端的出现均快于后者。因此,滕州地区表层土壤硒异常主要受煤矿开发的影响。     

森林次生演替过程中有机质层和矿质层土壤微生物残体的变化

微生物对土壤有机质(SOM)转化和形成具有重要作用,然而微生物残体对SOM贡献的评估仍是目前的热点。以长白山5个森林次生演替序列(20 a、80 a、120 a、200 a和≥300 a)和2个土壤深度(0～5 cm有机质层和5～15 cm矿质层)为对象,利用氨基糖和中红外光谱技术,探究森林次生演替过程中微生物残体变化及其对土壤有机碳(SOC)的贡献。森林次生演替序列80～200 a显著增加了有机质层和矿质层微生物残体含量及其对SOC的贡献,而在演替300 a均显著降低。森林演替80～200a有机质层和矿质层土壤芳香族碳组分/多糖较低,有利于微生物生物量碳(MBC)产生和微生物碳利用(高的MBC/SOC),促进微生物残体积累及其对SOC的贡献;而演替300 a芳香族碳组分/多糖较高,抑制MBC产生和微生物碳利用,导致微生物残体及其对SOC贡献的下降。SOC含量差异导致不同土壤深度微生物残体含量的变化,有机质层高的SOC产生高的MBC,进而刺激微生物残体积累;此外,有机质层难利用SOM组分高于矿质层,导致真菌残体对SOC的贡献比例下降,而细菌残体的贡献增加。     

Occurrence of Pesticides in Water, Sediments, and Fish Tissues in a Lake Surrounded by Agricultural Lands: Concerning Risks to Humans and Ecological Receptors

Lake Vela (Littoral Centre of Portugal) is considered a natural habitat with community interest and consequently was included in the Natura 2000 Network. However, this freshwater ecosystem has been potentially exposed to diffuse pollution generated by agricultural and livestock activities, which seriously compromise its ecological balance. As part of the Ecological Risk Assessment (ERA) proposed for Lake Vela, this study aimed to evaluate the occurrence of pesticides in different compartments: surface water, groundwater, sediments, and fish tissues. Moreover, to assess potential concerning effects on ecosystem and human health, the measured concentrations of pesticides were compared with regulatory and toxicological benchmarks. The results confirmed the presence of high concentrations of pesticides, including organochloride pesticides banned decades ago, in surface water, groundwater, and sediment. The measured concentrations of pesticides, compared with toxicological benchmarks, indicated that harmful effects are likely for aquatic species due to the presence of alachlor, aldrin, and dieldrin. Additionally, the concentrations of pesticides detected in groundwater were also above the recommended safety levels for drinking water, which constitutes a concern for the local population’s health. Results also showed an accumulation of alachlor in predator and benthic fish species which could represent a risk to human consumers and particularly to the regular fish predators (e.g., otters and birds). This study, as the first exposure characterization performed on the Lake Vela system, constitutes valuable and useful information for the ERA process. Although this preliminary assessment of risks should be continued and confirmed through a weight-of-evidence approach, it had already unraveled how concerning are the problems in this ecosystem and the urgency of implementing restoration measures to guaranty its sustainability. Furthermore, this study reinforces the importance of evaluating similar freshwater ecosystems that are also highly threatened by diffuse pollution.     

雨滴直径对表土结构和入渗特征的影响

为探究雨滴击溅对表层土壤结构和入渗特征的影响,揭示土壤微结构与入渗间的深层关联,以黄土高原土为对象,采用模拟降雨、同步辐射CT扫描和入渗试验,系统地分析了不同雨滴击溅作用下土壤结构变化与入渗速率间的关系。结果表明:(1)击溅土壤结构发生变化,团聚体数量和三维分形维数显著增加,孔隙体积和大孔隙率显著减小。雨滴直径越大,击溅后的团聚体破碎程度越强,孔隙堵塞率最高达46.40%。(2)雨滴击溅下,破碎的团聚体堵塞孔隙,在土壤表层形成致密低渗的结皮层,结皮强度随雨滴直径和击溅次数的增加逐渐增加。(3)土壤入渗速率随雨滴直径和击溅次数的增加逐渐减小,经过3次雨滴击溅后减渗效应最高可达91.81%。(4)土壤稳渗速率与雨滴直径和土壤结构特征参数呈显著指数关系变化。研究表明,雨滴直径显著影响表层土壤结构和入渗特征,雨滴直径越大,土壤结构越分散,土壤入渗能力越低。     

黄河三角洲表层土壤重金属空间分布与潜在生态风险评价

研究黄河三角洲表层土壤中重金属空间分布特征,评价其潜在生态风险。结果表明:表层土壤(0-20 cm)Cu、Zn、Cr、Cd、Pb、Ni、As和Hg的平均含量为27.87,79.19,69.01,0.383,21.98,33.42,13.76,0.025 mg/kg。除Cd外,其他重金属含量平均值均小于国家二级标准值;各重金属空间分布均呈现自西北向东南递减的趋势,且实验区含量最高,核心区含量最小;Hakanson潜在生态风险指数评价表明,Cd为中等-较强生态危害,其余重金属单项均为轻微生态危害,潜在风险程度由高到低依次为Cd>Hg>As>Ni>Cu>Pb>Cr>Zn;保护区综合潜在生态风险为轻微-中等生态危害,呈实验区>缓冲区>核心区的规律。重金属受人类活动影响较大,距离人类活动较近区域含量高,较远区域含量低。     

陕北典型农地表层土壤物理性质季节变化

土壤物理性质是影响土壤水文、侵蚀过程的重要因素。为此系统研究了陕北安塞4种典型农地（玉米、谷子、大豆和土豆）的土壤含水量、容重、水稳性团聚体和粘结力的季节变化特征。结果表明:4种农地表层土壤物理性质随季节变化的趋势大致相同,土壤含水量随降雨量的变化呈现出明显的峰谷。土壤容重和土壤粘结力在农作物生长阶段大体呈上升趋势,翻耕和收获后显著下降。水稳性团聚体则呈现单调递增趋势。在0.05显著性水平下的配对样本T检验显示:土壤含水量除玉米地和谷子地外（P=0.04）,其他农地土壤含水量之间无显著差异（0.29≤P≤0.99）;土壤容重除谷子地和大豆地外（P=0.03）,其他农地之间无显著差异（0.07≤P≤0.86）;土豆地与其他农地的水稳性团聚体之间有显著性差异（0.01≤P≤0.03）;各农地土壤粘结力之间无显著性差异（0.16≤P≤0.53）。土壤含水量的变化趋势与降雨的变化趋势基本一致,农事活动所引起的土壤扰动是土壤容重和粘结力变化的主要原因。研究结果对于分析农地水文、侵蚀过程的季节变化特征具有重要的意义。