Radionuclide Content in the Upper Vistula River Sediments in a Coal Mining Region in Poland (East-Central Europe)

Hard coal mining activity is one of the Technologically Enhanced Natural Radiation sources introduced more than a hundred years ago in the southern part of Poland. This study of radionuclides (K-40, Ra-226, Ra-228) in river sediments showed the principal factors determining the specific activity of radionuclides are distance from mines and sorption by clay particles in river sediments. The K-40 specific activity varies between 185 and 595 Bq/kg. The highest Ra-228 and Ra-226 specific activities, 280–610 and 205–415 Bq/kg, respectively, were detected in sediments of the Vistula in the vicinity of Silesia region.     

Dissolution and spatial distribution of resin acids and retene in sediments contaminated by pulp and paper industry

Purpose

Wood extractives in sediments originating from the wood industry may interfere with benthic biota in aquatic environments. The research area was the Äänekoski watercourse in Central Finland, which has been affected by the chemical wood industry for over a century. The goal was to determine the dissolution potency of resin acids (RAs) and their derivative, retene, in the sediment, and their current vertical and spatial stratification to assess the load due to potential erosion.

Materials and methods

Sediments were collected from two upstream reference sites and three lake-like basins, located as far as 33 km downstream from the mills. The dissolution potency was studied by two different agitation times and temperatures from sediment-water (1+4 v/v) elutriates. The vertical distribution of extractives was determined from the uppermost 20 cm of sediment. Using spatial interpolation, the distribution of extractives was estimated from two upper sediment layers (0–2 and 2–5 cm) downstream from the source. According to the interpolation, the total amount of dehydroabietic (DHAA) and isopimaric acids (IPA) were calculated as kg/ha in the whole sediment area.

Results and discussion

The total concentration of RAs in the surface sediment reached up to 168 µg/g dw, and they were found to desorb to water up to 77 µg/l. The concentrations of retene were low both in the sediment (<51 µg/g dw) and elutriate (<0.53 µg/l). Spatial interpolation showed that the highest calculated amounts of the most abundant RAs were in Kuhnamo basin, in the sediment layer 2–5 cm; the estimated amount of DHAA and IPA were approximately 440 and 85 kg/ha, respectively.

Conclusions

Disturbances may change the exposure situation, causing desorption of sediment-associated compounds in levels that may be harmful to aquatic animals. The amount of desorption varies depending on the concentration of contaminants in sediment, the nature of disturbance, and the sediment organic carbon content. Low retene concentrations can be explained by oxic conditions and low abundance of RAs in the sediments.

     

Estimation of soil organic carbon stock and its spatial distribution in the Republic of Ireland

Data scarcity often prevents the estimate of regional (or national) scale soil organic carbon (SOC) stock and its spatial distribution. This study attempts to overcome the data limitations by combining two existing Irish soil databases [SoilC and national soil database (NSD)] at the national scale, to create an improved estimate of the national SOC stock. Representative regression models between the near‐surface SOC concentration and those of deeper depths, and between SOC concentration and bulk density (BD) were developed based on the SoilC database. These regression models were then applied to the NSD derived SOC concentration map, resulting in an improved SOC stock and spatial distribution map for the top 10 cm, 30 cm and 50 cm depths. Western Ireland, particularly coastal areas, was found to have higher SOC densities than eastern Ireland, corresponding to the spatial distribution of peatland. We estimated the national SOC stock at 383 ± 38 Tg for the near‐surface of 0–10 cm depth; 1016 ± 118 Tg for 0–30 cm depth; and 1474 ± 181 Tg for 0–50 cm depth.     

土壤侵蚀物理模型中紫色土细沟侵蚀参数研究

以长江中上游典型侵蚀性土壤紫色土为研究对象,采用变坡限定性细沟土槽,研究不同流量、坡度和沟长情况下,紫色土细沟侵蚀特征,并量化了细沟侵蚀参数。结果表明:细沟侵蚀受水流水力特征、土壤性质和坡面影响,随着水流含沙量的增大,细沟侵蚀速率呈现减小趋势;流量越大,坡度越陡,细沟水流的剥蚀率越大,造成细沟侵蚀速率也越大。在5L/min的小流量下,细沟侵蚀速率受剥蚀率限制与含沙量没有出现线性关系,15,25L/min流量下,细沟侵蚀速率与含沙量呈线性相关。侵蚀速率在细沟开始处最大,随沟长的增大,水流能量消耗于挟带泥沙而迅速减小,相关性分析得到侵蚀速率与沟长呈指数递减,相关系数R2变化于0.45~0.98之间。通过回归分析得到试验条件下,紫色土细沟土壤可蚀性均值为0.005 3s/m,临界剪切力均值为2.92Pa。研究结果对于坡面土壤侵蚀物理模型的建立和推广应用提供数据支撑,为紫色土坡面侵蚀研究提供借鉴。     

Microbial uptake of low‐molecular‐weight organic substances out‐competes sorption in soil

Low‐molecular‐weight organic substances (LMWOS) such as amino acids, sugars and carboxylates, are rapidly turned over in soil. Despite their importance, it remains unknown how the competition between microbial uptake and sorption to the soil matrix affects the LMWOS turnover in soil solution. This study describes the dynamics of LMWOS fluxes (10 µm ) in various pools (dissolved, sorbed, decomposed to CO₂ and incorporated into microbial biomass) and also assesses the LMWOS distribution in these pools over a very wide concentration range (0.01–1000 µm ). Representatives of each LMWOS group (glucose for sugars, alanine for amino acids, acetate for carboxylates), uniformly ¹⁴C‐labelled, were added to sterilized or non‐sterilized soil and analysed in different pools between 1 minute and 5.6 hours after addition. LMWOS were almost completely taken up by microorganisms within the first 30 minutes. Surprisingly, microbial uptake was much faster than the physicochemical sorption (estimated in sterilized soil), which needed 60 minutes to reach quasi‐equilibrium for alanine and about 400 minutes for glucose. Only acetate sorption was instantaneous. At a concentration of 100 µm , microbial decomposition after 4.5 hours was greater for alanine (76.7 ± 1.1%) than for acetate (55.2 ± 0.9%) or glucose (28.5 ± 1.5%). In contrast, incorporation into microbial biomass was greater for glucose (59.8 ± 1.2%) than for acetate (23.4 ± 5.9%) or alanine (5.2 ± 2.8%). Between 10 and 500 µm , the pathways of the three LMWOS changed: at 500 µm , alanine and acetate were less mineralized and more was incorporated into microbial biomass than at 10 µm , while glucose incorporation decreased. Despite the fact that the LMWOS concentrations in soil solution were important for competition between sorption and microbial uptake, their fate in soil is mainly determined by microbial uptake and further microbial transformations. For these substances, which represent the three main groups of LMWOS in soil, the microbial uptake out‐competes sorption.     

Trace metals and lanthanides in a tropical river environment

The river Periyar in the State of Kerala, India is subjected to pollution from a number of industrial units such as zinc smelter, rare earth plant, phosphatic fertilizer unit etc. The levels of Zn and Cd in water and sediments in the river have in recent years increased ten fold as compared to a study conducted earlier during 1970. The levels of these trace metals in water increase at the backwater zone under high salinity in summer due to solubilisation from the sediments. Among the lanthanides Ce is the most predominant in water. Elements such as Ce, La, Sm, Gd and Y show a concentration factor of 10³ in sediments. The trace metals show maximum concentration at the top layer of sediment column extending up to 20 cm from the surface. Particle size analysis of river sediments in the industrial outfall area shows a mass median diameter of 11 μm with a geometric standard deviation of 2.4 for Zn and Cd.     

简易式工厂化循环水对虾养殖系统构建及试验

为探索低换水量的对虾养殖生产方式,该研究构建了一种简易式工厂化对虾养殖系统,试验组利用自行研发的蛋白分离器和新型集污盘去除系统总悬浮颗粒物和老化微藻,对照组不设置蛋白分离器和集污盘,进行对虾养殖和水质调控试验,结果表明:试验组平均总氨氮浓度、平均亚硝氮浓度、平均TSS(Total Suspended Solids)浓度、平均副溶血弧菌数量分别为(0.4±0.16)、(0.53±0.23)、(68.33±39.72)mg/L和(140±113.83)cfu/mL,显著低于对照组(0.96±0.62)、(1.17±0.59)、(147.14±94.18)mg/L和(661.34±473.96)cfu/mL(P0.05);试验组成活率及单位产量分别为82.62%±5.64%和(3.44±0.85)kg/m~3,显著高于对照组18.29%±4.63%和(1.09±0.23)kg/m~3(P0.05)。该研究构建的简易式循环水工厂化系统,设置蛋白分离器流量10 m~3/h且不间断运行,养殖前45 d不换水、后55 d利用集污盘进行强排污保持日换水量5%的情况下能够有效调控对虾养殖水质。     

草地植被覆盖度坡度及雨强对坡面径流含沙量影响试验研究

为研究植被修复状态下径流含沙量变化。该试验运用人工模拟降雨试验方法,分析了径流含沙量草被调控效益变化。结果:1)不同降雨强度或坡度下,平均径流含沙量随草被盖度的增大而减小,草被盖度从30%~70%,含沙量分别降低约10或5 kg/m3,可用线性方程显著描述。草被消减雨强对径流含沙量影响大于草被消减坡度的。平均径流含沙量随降雨强度或坡度的增大而增大,分别可用幂函数或指数函数方程显著描述,决定系数在0.5或0.8以上。2)基于单位水流功率建立幂函数模型决定系数为0.940,模型有效系数为0.986,说明模型模拟精度都较高。3)基于坡度、雨强和盖度建立指数函数模型决定系数为0.937,模型有效系数为0.894,说明模型模拟精度都较高。该研究可以预测草地坡面含沙量,为生态建设和流域管理提供指导。     

Leaching of potassium,magnesium, manganese and iron in relation to porosity of tilled and orchard loamy soil

Abstract

The aim of this study was to examine the leaching of potassium, magnesium, manganese and iron in tilled and orchard silty loam soil. The experimental treatments were: conventionally tilled field (CT) with main tillage operations including pre-plough (10 cm)+harrowing followed by mouldboard ploughing to 20 cm depth, and a 35-year-old apple orchard (OR) with a permanent sward. Leaching of the cations was determined in soil columns of undisturbed structure, 21.5 cm diameter and 20 cm height, from a depth of 0–20 cm. All the columns were subjected to spray irrigation at a level of 1110 ml (30 mm), and leachate in 50-ml increments was collected. Concentration of the cations in the leachate was determined using a spectrophotometer ICP-AS. Pore size distribution data showed that the volume of pores >20 µm under CT was greater at a depth of 0–10 cm and lower in the 10–20 cm soil layer under OR, and the reverse was true with respect to pores <6 µm. At each 50-ml leachate, concentration of all the cations was greater under CT than OR. In most leachates the differences were more pronounced for potassium and magnesium than iron and manganese. Percolation of the leachate was considerably faster in orchard than tilled soil.     

Vertical Distribution and Fate of Trace Metals and Persistent Organic Pollutants in Sediments of the Seine and Marne Rivers (France)

Trace metals: Cd, Cu, Cr, Ni, Pb and Zn and persistent organicpollutants: polycyclic aromatic hydrocarbons (PAHs) and polychlorobiphenyls (PCBs) were investigated in a fraction ofsediments characterized by a granulometry < 200 μm. Coresfrom 17 to 54 cm depth, were collected at two sites of theSeine river upstream (Port à l'Anglais) and downstream (Saint-Cloud) from Paris and at one site of the Marne river (Saint-Maurice). Marne river sediments displayed higher Cu andPb levels than those of the Seine river. Except for Cd and Cr,contents did not vary notably in the Seine river sediments.Metal contents, except Pb, were significantly correlated withthe sediment fraction which granulometry is < 50 μm,particularly at Port à l'Anglais (p < 0.001). Correlationcoefficients between Cr, Cu, Ni and Zn contents and clayfractions of the cores ranged from 0.85 to 0.99 at both sitesof the Seine river. PCB levels varied widely, ranging from 27to 689 μg kg^-1 and were highly correlated with bothsediment fraction < 50μm and particulate organic carbon(POC) ratio. PAH levels ranged from 2.30 to 41.3 μg g^-1 and displayed the highest values close to dams; theyshowed no correlations with sediment fraction < 50 μm and POC.     

不同宽度冲刷槽对崩岗崩积体产流产沙的影响

为了解不同宽度冲刷槽对坡面冲刷侵蚀过程中产流产沙的影响,该研究以崩岗崩积体为对象,通过不同冲刷槽宽度(10、20、30、40、50 cm)和不同单宽流量(1.2×10-2、2.4×10-2、3.6×10-2、4.8×10-2 m2/min)相结合的室内模拟冲刷试验,研究不同宽度冲刷槽对崩积体产流产沙的影响。结果表明:1)单宽流量为1.2×10-2,2.4×10-2,3.6×10-2 m2/min时,不同冲刷槽宽度之间径流率、产沙率存在显著差异(P0.05);单宽流量为4.8×10-2 m2/min时,不同冲刷槽宽度之间径流率、产沙率差异不显著。2)单宽流量一定,不同冲刷槽宽度下径流率随时间变化趋势相同;单宽流量为1.2×10-2 m2/min时,不同冲刷槽宽度条件下产沙率和含沙量随时间变化趋势不同,其他单宽流量下产沙率和含沙量随时间变化趋势相同。3)单宽流量相同,不同冲刷槽宽度下累积径流量差异不显著;单宽流量为1.2×10-2,2.4×10-2,3.6×10-2 m2/min条件下,不同冲刷槽宽度下累积产沙量和平均含沙量差异显著(P0.05)。该研究揭示了冲刷槽宽度对崩积体产流产沙的影响,为今后试验冲刷槽宽度的选择提供参考。     

Comparison of Hg and Pb Fluxes to Hummocks and Hollows of Ombrotrophic Big Heath Bog and to Nearby Sargent Mt. Pond,Maine, USA

Two hummock cores (separated by 1 m), two hollow cores (separated by 1 m and both within 5 m of the hummock) from ombrotrophic Big Heath, and a single core from Sargent Mountain Pond (12 km north-northeast of the bog), Mt. Desert Island, Acadia National Park, Maine, USA were collected in 1983 and dated using 210Pb and analyzed for a suite of major and trace metals. The hummock cores correspond closely in terms of dating profiles, concentrations of Hg and Pb, and thus trends and values for accumulation rates. The hollow cores agree generally with each other but give more subdued peaks in concentration and lower integrated anthropogenic burdens of Hg and Pb and 50% lower unsupported 210Pb than the hummock cores. Σ210Pbuns. (Bq/cm2), ΣHganth. (ng/cm2), and ΣPbanth. (µg/cm2) for the two hummock cores were 0.744 and 0.773, ≈ 130 and 130 (ng/cm2), and ≈ 159 and 138 (µg/cm2), respectively. The values for Sargent Mountain Pond were 0.411, 269, and 72, respectively. Hummock cores agree closely with the lake sediment core with respect to timing of maximum accumulation rates which occurred in the 1970s; Background atmospheric deposition rates of Hg and Pb to coastal Maine appear to have been about 2.5 to 3 ng/cm2/yr and <0.2 µg/cm2/yr, respectively. Atmospheric deposition of Hg and Pb increased to as much as 20 ng/cm2/yr and 2 µg/cm2/yr, respectively, by the 1970s and has decreased since then. Probably more than 50% of the Hg and Pb are deposited in dry and occult deposition.     

Impact of anthropogenic activity on the Hg concentrations in the Piracicaba river basin (São Paulo State, Brazil)

A sampling and analysis program has been completed between 1995 and 1998 in order to determine mercury concentrations in water, sediments, soils and fish in the Piracicaba river basin, one of the most populated and industrialized regions in Brazil. In sediment, the average Hg concentrations varied between 33 ± 17 ng g^?1 and 106 ± 78 ng g^?1, in samples collected during the rainy and dry season, respectively. The same averages were also found for soil samples (35 ± 14 and 109 ± 61 ng g^?1). In water, the total Hg concentration varied between < 1.1 and 24.0 ng L^?1. In piscivore fish, up to 943 μ g Hg kg^?1 was found. Our results show that all compartments undergo Hg contamination, in view of the levels found in pristine environments. Water contamination seems to be due mainly to diffuse processes of soil erosion and suspension of river bed sediment during the rainy season. Also untreated wastewaters generated by industrial activities and from domestic sewage appear to be potential non-point sources in the most industrialized and populated part of the basin. On the other hand, atmospheric transport of mercury originating from the Campinas Metropolitan Region could be another source of mercury contamination, especially in the basin headwaters.     

The significance of various sediment magnetic mineral fractions for tracing sediment sources in Killimicat Creek

The mineral magnetic properties of sediment are increasingly being used to determine the sources of sediment, and associated nutrients and contaminants in drainage basins. This study was undertaken to measure the relative contributions of the magnetic mineral components in sediment (i.e., components associated with surface bound Fe, the heavy mineral fraction, and as inclusions in particles) to determine the extent to which they represent the bulk of the sediment. Deposited channel sediment samples from the tributaries and downstream reach at the first major confluence in the headwaters of Killimicat Creek, New South Wales, were sieved to separate 6 particle size fractions, and the mineral magnetic properties measured to determine the relative contribution of sediment from the smaller tributary basin. The finest sand component (63–125 μm) was then separated into light and heavy mineral fractions, and magnetic measurements made on each fraction. Magnetic parameter data from the 63–125 μm fraction, measured before density separation, show a dominance of sediment (70±12%) derived from the smaller tributary basin. Measurements of the light sediment fraction give a similar result (73±13%). The proportion of the heavy mineral fraction delivered from the smaller tributary is 78±38%. The light mineral fraction of all of the samples were treated with HCl to remove surface bound Fe, and subsequent magnetic measurements show that 41–94% of the mass specific magnetic susceptibility is attributable to magnetic minerals associated with surface bound Fe. The heavy mineral component, while <4% by weight of the 63–125 μm fraction, contributes 5–40% of the total magnetic susceptibility. The results show that most of the magnetic mineral component (>60%) is associated with sediment particles, rather than the discrete heavy mineral component.     

Atmospheric Lead Deposition from 12,400 to ca. 2,000 yrs BP in a Peat Bog Profile,Jura Mountains,Switzerland

The bog at Etang de la Gruère (Jura Mountains, Switzerland) consists of 420 cm of Sphagnum-dominated bog peat overlying 230 cm of Carex-dominated fen peat. One hundred cm below the bog surface, there is a pronounced peak in lead (Pb) concentration (approx. 10 µg/g) which has been dated at 2110 ± 30 BP and can be attributed to Roman Pb mining and smelting. Lead concentrations in peats from deeper, much older layers were measured using ICP-MS and found to be low and relatively constant (0.28 ± 0.04 µg/g, n = 17) from 405 cm to 235 cm which corresponds to the period from approx. 8,000 and 5,500 years before present (BP). In this same interval, scandium (Sc) concentrations (measured using INAA) were 0.07 ± 0.02 µg/g, yielding an average Pb/Sc ratio of 4.1 ± 1.2. These values are assumed to represent the true "background" Pb and Sc concentrations and Pb/Sc ratios of pre-anthropogenic aerosols. At 205 cm the Pb concentrations began to increase by 2 to 3 times, but these are proportional to the increases in aluminum (Al), titanium (Ti), silicon (Si), and Sc, and reflect an increase in Pb deposition supplied by silicate-derived soil dust. This depth, dated at 5,230 BP, coincides with the development of agriculture and indicates the impact of soil cultivation on metal fluxes to the air. At 115 cm, however, the Pb concentrations increase out of proportion with Sc; this point was dated at 3,000 BP and reflects the beginning of Pb contamination by mining and metallurgy in Europe and the Middle East. There are two pronounced peaks in Pb concentrations centered at 435 cm and 555 cm, corresponding with local maxima in ash and ash-forming major elements at the same depths. These samples have been dated at 8,230 BP and 10,590 BP, respectively, indicating the Vasset/Killian volcanic events (Massif Central, France) and Younger-Dryas cold phase as the most likely explanations.     

Vertical distribution of charcoal in a sandy soil: evidence from DRIFT spectra and field emission scanning electron microscopy

This study uses diffuse reflectance infrared Fourier Transform (DRIFT) spectrometry and field emission scanning electron microscopy to investigate the vertical distribution of charcoal in a sandy soil from SE Australia. The soil was sampled to bedrock (120 cm) at varying depths and bulk samples were fractionated into three particle‐sizes: macro‐ (2000–200 µm), micro‐ (200–60 µm) and mineral‐associated organic matter (MAOM, < 60 µm). Charcoal was isolated from 0–30 and 30–60‐cm depths. Soil charcoal was detected by using a DRIFT band centred at 1590 cm^?1 and scanning electron microscopy combined with energy dispersive spectroscopy. Charcoal content as a proportion of soil organic carbon (SOC) was estimated with linear regressions of cumulative DRIFT bands. At 0–30 cm, charcoal content as a portion of SOC did not differ significantly between particle‐size fractions, constituting 5–26% of SOC. At a depth of 30–60 cm, charcoal constituted 19–39% of SOC in the fractions. At 60–100 cm, charcoal was only detectable in the mid‐sized fraction, where it constituted about 17% of SOC. These results support our previous hypothesis of charcoal enrichment in the micro‐fraction inducing a greater SOC stability in this fraction as inferred from radiocarbon ages (Hobley et al., 2013). Our findings indicate that DRIFT spectra can be used to detect the presence and amount of charcoal in soil, which may prove to be a simple and low‐cost alternative to more laborious and costly detection methods.     

Runoff,erosion and sediment particle size from smooth and rough soil surfaces under steady rainfall-runoff conditions

The responses of runoff and erosion to soil surface roughness (SSR) have been extensively studied in the past decades; however, most of these studies were conducted at the early stage of rainfall, whereas few studies were specifically conducted during steady runoff conditions. In this study, runoff, soil losses and sediment particle sizes from smooth and rough surfaces were measured after surface runoff stabilisation to improve the understanding of the relationship between SSR and soil erosion. A cascade of two independent soil boxes in which the runoff samples from upslope and downslope boxes can be collected independently or together was used to perform the experiments. The upslope box supplied runoff to the downslope study box. Three rainfall intensities of 50, 75 and 100 mm/h were applied. The results suggest that SSR has a significant effect on soil erosion when runoff reaches a steady state. Although the difference in the runoff rate was small between the rough and smooth surfaces, the sediment rate and concentration of particles were significantly lower for the rough surface than for the smooth surface. Through analysing the particle size distribution (PSD) of sediment, we found that selective sediment delivery is an important reason for the soil erosion reduction by SSR. The rainfall intensity decreased the difference in the sediment rates between the smooth and rough surfaces. The extra inflow increased the runoff rates, sediment rates and concentration rates for both the smooth and rough surfaces; however, the increasing degrees of the runoff rate, sediment rate and concentration rate had significant differences between the rough and smooth surfaces. A stepwise multiple regression showed that significant linear relationships existed between one or more PSDs of 20–50, 50–100, 100–250 and 1000–2000 µm and the sediment rate.     

保护性措施对农田土壤风蚀影响的室内风洞模拟

为寻求合理的保护性耕作措施,试验设计了砾石覆盖、秸秆覆盖、覆盖与留茬组合的措施和4个风速等变量,研究风速、覆盖物和覆盖度与风蚀量、抗风蚀效率、风沙流结构的关系,比较多种措施之间的抗风蚀效果优劣.结果表明:1)4个设定风速下30％ ～ 90％覆盖度的秸秆覆盖的抗风蚀效率在54％ ～ 92％之间,砾石覆盖为26％～72％,30％的砾石覆盖或30％的秸秆覆盖与3种留茬高度的组合措施下,平均抗风蚀效率均在70％ ～ 78％之间;2)随着覆盖度的增加,砾石覆盖措施最小可抑制的有效风速值从8.0 m/s逐渐增大到12.5 m/s,秸秆覆盖措施从10.1m/s增加到了14.3 m/s;3)覆盖处理下0～62 cm高度内的输沙量大部分集中在0～26 cm;4)覆盖与留茬组合措施的输沙量多集中在60 cm以内.     

Intensive organic vegetable production increases soil organic carbon but with a lower carbon conversion efficiency than integrated management

Intensive vegetable production in greenhouses has rapidly expanded in China since the 1990s and increased to 1.3 million ha of farmland by 2016, which is the highest in the world. We conducted an 11‐year greenhouse vegetable production experiment from 2002 to 2013 to observe soil organic carbon (SOC) dynamics under three management systems, i.e., conventional (CON), integrated (ING), and intensive organic (ORG) farming. Soil samples (0–20 and 20–40 cm depth) were collected in 2002 and 2013 and separated into four particle‐size fractions, i.e., coarse sand (> 250 µm), fine sand (250–53 µm), silt (53–2 µm), and clay (< 2 µm). The SOC contents and δ¹³C values of the whole soil and the four particle‐size fractions were analyzed. After 11 years of vegetable farming, ORG and ING significantly increased SOC stocks (0–20 cm) by 4008 ± 36.6 and 2880 ± 365 kg C ha^?1 y^?1, respectively, 8.1‐ and 5.8‐times that of CON (494 ± 42.6 kg C ha^?1 y^?1). The SOC stock increase in ORG at 20–40 cm depth was 245 ± 66.4 kg C ha^?1 y^?1, significantly higher than in ING (66 ± 13.4 kg C ha^?1 y^?1) and CON (109 ± 44.8 kg C ha^?1 y^?1). Analyses of ¹³C revealed a significant increase in newly produced SOC in both soil layers in ORG. However, the carbon conversion efficiency (CE: increased organic carbon in soil divided by organic carbon input) was lower in ORG (14.4%–21.7%) than in ING (18.2%–27.4%). Among the four particle‐sizes in the 0–20 cm layer, the silt fraction exhibited the largest proportion of increase in SOC content (57.8% and 55.4% of the SOC increase in ORG and ING, respectively). A similar trend was detected in the 20–40 cm soil layer. Over all, intensive organic (ORG) vegetable production increases soil organic carbon but with a lower carbon conversion efficiency than integrated (ING) management.     

Distribution of Heavy Metals in Marine Sediments of Palermo Gulf (Sicily, Italy)

Concentrations of Cr, Cu, Hg, Pb and Zn have been measured, by atomic absorption spectrophotometry, in the fine fraction (<63 μm) of surface sediments collected in 30 sites in the Palermo Gulf (Sicily, Italy) in order to assess the levels and the spatial distribution of these elements. Enrichment factors calculated with respect to clean areas have been considered to discriminate between levels due to background or to pollution contributions. The sampling stations, which form a grid inside these areas, are characterized by geographic proximity and by the presence of pollution sources. Ratio matching technique along with hierarchical clustering, minimum spanning tree and principal component analysis have been used for the statistical analysis of data, allowing to better describe the spatial distribution of metal levels. Our work allowed to assess the anthropogenic contribution to the pollution of the area under investigation through industrial and domestic wastes, presence of an harbour area and river inflow.