Loss on ignition and kjeldahl digestion for estimating organic carbon and total nitrogen in estuarine marsh soils: Calibration with dry combustion

Soils (n=250) were collected from ten salt and brackish-water marshes of North Carolina and analyzed for organic matter content by loss on ignition (LOI) and Kjeldahl nitrogen (KN). Total organic carbon and total nitrogen were determined on the same samples using an elemental CHN analyzer. Regression analyses indicated that LOI and KN were excellent estimators of organic C (R²=0.990) and total N(R²=0.986), respectively, in low clay content (0–11%) marsh soils containing a wide range of soil organic C (0.1–28%) and total N (0–1.6%). A quadratic equation best described the relationship between organic C and organic matter (Organic C=0.40 [LOI] +0.0025 [LOI]²) while a linear model accurately described the relationship between total N and Kjeldahl N (Total N=1.048 [KN]?0.010). The proportion of organic C in organic matter (C/OM) increased with increasing soil organic matter content, probably as a result of aging. Young marshes, which are characterized by low soil organic content contain C/OM ratios similar to emergent vegetation (40–45%). In old organic soils (70–80% organic matter), C/OM increased to 57–60% due to accumulation of reduced organic materials.     

Evolution of organic matter in lignite-containing sediments revealed by analytical pyrolysis (Py–GC–MS)

Newly vegetated sites provide opportunities to enlighten organic matter (OM) transformation mechanisms in soils and sediments at very early stages of development which, in turn, is relevant to better understand general ecosystem functioning. Mine acid soils and sediments in the Lusatian open cast lignite mining district (Germany) contains a high concentration of fossil carbon (lignite) in ad mixture with recent OM from the local vegetation, both contributing to the humified OM pool. In this study, analytical pyrolysis (Py–GC–MS) was used to monitor the different C sources (lignite or plant derived) in developing mine tailing soils and sediments and their degree of degradation in contrasting environments. Representative vegetation and the organic carbon (OC) rich soil/sediment fraction (humus fraction) were sampled at two depths (0–5 and 5–10 cm) in three plots along a transect covering an upland forest soil, a partially submerged sediment at the land–water interface and a constantly submerged sediment. The analysis of plant (lipds, isoprenoids, methoxyphenols and carbohydrates) and possible lignite (alkyl napththalenes, alkyl benzenes and PAHs) biomarkers released after pyrolysis supports previous findings in the area using other proxies. It was possible to discern OM sources in soil/sediment humus fractions, both from the substrate (lignite) as well as from the prevailing vegetation of the area. Environmental conditions in the submerged sediment seem to favour OM protection and the accumulation of decomposing plant material, whereas more intense OM degradation seems to prevail in the land–water interface areas characterized by fluctuating water level. In addition, a well resolved series of organic sulfur compounds (OSCS) found in the submerged sediments of rehabilitated acid lakes, indicates the possible occurrence of particular mechanisms of C preservation in this extreme anoxic S rich environment, i.e. via sulphur “quenching” with plant derived lipids during early diagenesis.     

Characterization and quantification of biomarkers from biomass burning at a recent wildfire site in Northern Alberta,Canada

The composition of organic matter (OM) in pine vegetation and soil samples from a pine forest which was charred by a wildfire was analyzed using solid-state nuclear magnetic resonance (¹³C NMR) and gas chromatography–mass spectrometry (GC–MS) of solvent extracts to study the effects of thermal alteration on soil organic matter (SOM). The NMR data revealed the presence of unaltered biomolecules (cellulose, proteins) and low contents of aromatic C (15%) in the charred pine wood and cones while the charred soil samples exhibited higher contents of aromatic C (39–56%). The solvent extraction of charred and uncharred plant and soil samples yielded diterpenoids, triterpenoids, steroids, a series of aliphatic lipids, phenols and carbohydrates indicating the predominant input of higher plant OM and minor contributions from microorganisms and/or fauna. The lower yield of solvent extractable aliphatic lipids in the charred samples versus the uncharred samples suggests that these compounds are thermally degraded during a wildfire. Molecular markers for the burning of cellulose (levoglucosan, mannosan, galactosan) were detected in all charred samples. The comparison of charred and uncharred samples allowed the identification of unaltered pine derived biomolecules and their thermal alteration products in the charred samples. Terpenoid and steroid biomolecules were in part altered during incomplete combustion to aromatic, unsaturated and polar derivatives (“pyromolecules”) that still retained the characteristic skeleton of their precursors. Since some of the polar degradation products found in the charred soils can be generated either from thermal or microbial degradation, the aromatic and unsaturated hydrocarbon products are preferred as molecular markers for SOM burning. Ratios of biological precursors to aromatic (diterpenoids) or unsaturated products (steroids) indicate that the cyclic lipids in the pine wood and the soil surface horizon were highly altered. In conclusion, the solvent extractable lipids and carbohydrates in charred SOM are valuable, source-specific molecular markers for the burning of plant biomass and for tracing the biogeochemistry of charred residues in soils.     

Microbial community changes in contaminated soils in response to phenanthrene amendment

Leachate and reclaimed wastewater have become the important sources of polycyclic aromatic hydrocarbons in soils. However, the information on bioremediation of leachate and reclaimed wastewater-contaminated soils is still lacking. Identification of changes in microbial structure or of enriched genera related to biodegradation could aid identification of particular organisms or consortia capable of degrading polycyclic aromatic hydrocarbons in these contaminated soils. In this study, terminal restriction fragment length polymorphism, coupled with 16S Ribosomal ribonucleic acid clone library analysis, was applied to investigate the composition of bacterial community in leachate-contaminated soil or grassland soil irrigated reclaimed wastewater and the response to phenanthrene amendment. Results showed that phenanthrene amendment had significant but different impacts on microbial community structure, dependent on soil source. Several greatly enriched terminal restriction fragments with phenanthrene biodegradation were identified. Moreover, genus rhizobacteria, possibly linked to phenanthrene biodegradation, was firstly reported in this study. This work might provide some new insights into bioremediation of polycyclic aromatic hydrocarbons-contaminated soils.     

Spatial variability of reconstructed soil properties and the optimization of sampling number for reclaimed land monitoring in an opencast coal mine

Drastically disturbed soils caused by opencast mining can result in the severe loss of soil structure and increase in soil compactness. To assess the effects of mining activities on reconstructed soils and to track the changes in reclaimed soil properties, the variability of soil properties (soil particle distribution, penetration resistance (PR), pH, and total dissolved salt (TDS)) in the Shanxi Pingshuo Antaibao opencast coal-mine inner dump after dumping and before reclamation was analyzed using a geostatistics method, and the number of soil monitoring points after mined land reclamation was determined. Soil samples were equally collected at 78 sampling sites in the study area with an area of 0.44 km². Soil particle distribution had moderate variability, except for silt content at the depth of 0–20 cm with a low variability and sand content at the depth of 20–40 cm with a high variability. The pH showed a low variability, and TDS had moderate variability at all depths. The variability of PR was high at the depth of 0–20 cm and moderate at the depth of 20–40 cm. There was no clear trend in the variance with increasing depth for the soil properties. Interpolation using kriging displayed a high heterogeneity of the reconstructed soil properties, and the spatial structure of the original landform was partially or completely destroyed. The root-mean-square error (RMSE) can be used to determine the number of sampling points for soil properties, and 40 is the ideal sampling number for the study site based on cross-validation.     

Ditching and Ditch-Plugging in New England Salt Marshes: Effects on Hydrology, Elevation, and Soil Characteristics

Anthropogenic activities in New England salt marshes have altered hydrologic flows in various ways, but unintended consequences from some types of habitat modifications have received little attention. Specifically, ditches have existed on salt marshes for decades, but the effects of these hydrologic alterations are only poorly understood. Ditch-plugging is a more recent methodology used for salt marsh habitat enhancement and mosquito control, but the long-term effects from this management practice are also unclear. The interactions involving marsh surface elevation, soil characteristics, and hydrologic regimes result in feedbacks that regulate the salt marsh self-maintenance process, and these interactions vary with hydrologic modification. Using natural tidal creeks and pools as controls, we examined the effects of ditching and plugging, respectively, on hydrology, surface elevations, and soils. Results showed the most apparent effects of altered hydrology from ditching are prolonged pore-water retention in the rooting zone and significantly lower soil bulk density and mineral content when compared with natural creek habitat. From a management perspective, the important question is whether the combined alterations to physical and biological processes will hinder the marsh’s ability to keep pace with increasing rates of sea level rise, especially in more heavily ditched marshes. In contrast, ditch-plugging results in the decoupling of feedback processes that promote salt marsh self-maintenance and in doing so, threatens marsh stability and resilience to climate change. High surface water levels, permanently saturated soils, marsh subsidence, and significantly lower bulk density, carbon storage, soil strength, and redox levels associated with hydrologic alterations from ditch-plugging all support this conclusion.     

Accretion and canal impacts in a rapidly subsiding wetland II. Feldspar marker horizon technique

Recent (6–12 month) marsh sediment accretion and accumulation rates were measured with feldspar marker horizons in the vicinity of natural waterways and man-made canals with spoil banks in the rapidly subsiding environment of coastal Louisiana. Annual accretion rates in aSpartina alterniflora salt marsh in the Mississippi deltaic plain averaged 6 mm in marsh adjacent to canals compared to 10 mm in marsh adjacent to natural waterways. The rates, however, were not statistically significantly different. The average rate of sediment accretion in the same salt marsh region for a transect perpendicular to a canal (13 mm yr^?1) was significantly greater than the rate measured for a transect perpendicular to a natural waterway (7 mm yr^?1). Measurements of soil bulk density and organic matter content from the two transects were also different. This spatial variability in accretion rates is probably related to (1) spoil bank influences on local hydrology; and (2) a locally high rate of sediment input from lateral erosion associated with pond enlargement. In a brackishSpartina patens marsh on Louisiana’s Chenier plain, vertical accretion rates were the same along natural and canal waterways (3–4 mm yr^?1) in a hydrologically restricted marsh region. However, the accretion rates for both waterways were significantly lower than the rates along a nonhydrologically restricted natural waterway nearby (11 mm yr^?1). The vertical accretion of matter displayed semi-annual differences in the brackish marsh environment.     

Laboratory and pilot studies on reclamation of a salt-affected alluvial soil

Soil column experiments showed that a surficial sodic soil is efficiently reclaimed using freshwater, after the addition of saturated gypsum solution. Gypsum application in the field was beneficial in terms of maintaining high soil permeability, increased water infiltration and neutral pH after a rainfall event. In the present paper, two different reclamation techniques for the plough layer of a sandy loam sodic soil were tested in laboratory columns, 25 cm long and 10 cm in diameter; the first using freshwater alone and the second using a saturated gypsum solution. The dynamics of salt removal were studied by continuous analysis of the water drained from the bottom of the columns. When freshwater was used, sodium presented the lower removal rate and adversely affected soil permeability. When gypsum solution was used, calcium was present in the flushing solution and the effect of sodium dominance on clay dispersion and soil clogging was limited. The results presented in this study are of practical importance with respect to the reclamation of sodic soils found in the coastal area of the east Nestos Delta, Greece, where freshwater is limited, due to seawater intrusion, and saline groundwater is used for irrigation.     

Freshwater impacts in normally hypersaline marshes

Heavy rainfall in 1978 and 1980 caused flooding of southern California salt marshes. Examination of three marshes demonstrated a broad range of freshwater effects which correlated with the degree of change in soil salinity. At Tijuana Estuary (1980), a short-term reduction in the salinity of normally hypersaline soils was followed by a 40% increase in the August biomass of Spartina foliosa. At Los Penasquitos Lagoon (1978), a longer period of brackish water influence was followed by a 160% increase in August biomass of Salicornia virginica. At the San Diego River (1980), flood flows were augmented by major reservoir discharge. Continuous freshwater flow leached most of the marsh soil salts and caused replacement of halophytes by freshwater marsh species. The first two cases probably fell within the normal range of flooding events, even though the hydrology of both watersheds has been modified. The vegetation response was functional; productivity increased but there was no major change in species composition. As expected, vegetation rapidly returned to preflood conditions. However, the long-term freshwater flow in the Dan Diego River was unnatural. Floral composition changed as soils were leached of salts. Recovery following the return of saline soils has been slow because many native halophytes are not good colonizers. The system's resilience is limited, and modification of natural stream discharge can cause permanent changes in coastal wetlands.     

A first step towards identification of tannin-derived black carbon: Conventional pyrolysis (Py–GC–MS) and thermally assisted hydrolysis and methylation (THM–GC–MS) of charred condensed tannins

Tannins account for a significant proportion of plant biomass and are likely to contribute to the residues formed by incomplete biomass combustion (black carbon, BC). Nonetheless, the molecular properties of thermally modified tannins have not been investigated in laboratory charring experiments. We applied conventional analytical pyrolysis–gas chromatography–mass spectrometry (Py–GC–MS) and thermally assisted hydrolysis and methylation (THM–GC–MS) to investigate the effects of heat treatment with a muffle furnace on the properties of condensed tannins (CT) from Corsican pine (Pinus nigra) needles. Py–GC–MS showed a decrease in the relative abundance of the 1,2,3-trihydroxybenzenes (pyrogallols) at ⩾300 °C and of the dihydroxybenzenes (mainly catechols) at ⩾350 °C due to dehydroxylation of the CT B ring. Further dehydroxylation led to formation of monohydroxybenzenes (phenols), which showed a strong enrichment between 350 and 400 °C and, at higher temperatures, to a series of monocyclic and polycyclic aromatics [benzene, alkyl benzenes and polycondensed aromatic hydrocarbons (PAHs)]. Degradation of the A ring could not be recognized via Py–GC–MS, probably because of the poor chromatographic behavior of 1,3,5-trihydroxybenzenes (phloroglucinols). The progressive dehydroxylation and eventual polycondensation of the CT B ring was corroborated using THM–GC–MS. In addition, with THM–GC–MS the thermal rearrangement of CT A rings at 300 °C and higher was inferred from the relative abundance of 1,3,5-trimethoxybenzenes (methylated phloroglucinol derivatives). These compounds were observed at moderate/high temperature (up to 450 °C) and can not be produced from THM of lignin, suggesting that they may be markers of CT in natural BC samples.     

平朔露天煤矿复垦区土壤中多环芳烃分布特征、来源解析及风险分析

原煤的开采、储存、运输及其加工利用过程是多环芳烃(PAHs)污染的主要来源。由于缺乏相关系统调查数据,其对煤矿复垦区土壤环境质量的影响尚不明确。平朔煤矿复垦土地主要作为耕地利用,了解其PAHs污染状况直接关系粮食安全和人体健康。该研究通过野外实地调查,开展了平朔煤矿复垦区表层土壤中多环芳烃(PAHs)的毒性风险分析研究。在整个平朔煤矿45 km2范围内,以500 m×500 m间距为基准,按照不同用地类型,采集了0~20 cm深度土壤样品179个,再按照1 km×1 km单元格组合后分析。使用安捷伦高分辨气相色谱低分辨质谱进行目标物的检测。加入代用标准2氟联苯(2 FBP)以进行回收率控制。研究结果表明：土壤中16种EPA PAHs的含量范围为213.60~2 513.20 ng·g-1,均值为717.09 ng·g-1。PAHs成分特征显示主要以3~4环为主(52%),5~6环次之(42%),2环所占比例最低(6%)。使用相关分析法判定,主要污染来源为原煤。毒性风险分析结果显示,平朔煤矿土壤PAHs存在一定生态风险,当土地重新作为农田加以利用时,需要加以关注。     

Organic matter quality in reclaimed boreal forest soils following oil sands mining

Following surface mining of the Athabasca Oil Sands deposits in northeastern Alberta, Canada, land reclamation entails the reconstruction of soil-like profiles using salvaged soil materials such as peat and mining by-products. The overall objective of this research was to assess soil organic matter (SOM) quality in different reclamation practices as compared to undisturbed soils found in the region. Soil samples (0–10 cm) were taken from 45 plots selected to represent undisturbed reference ecosites and reclamation treatments. Soil OM pools were isolated using a combination of acid hydrolysis and physical separation techniques. Chemical composition of the low density fractions was characterized using ramped cross polarization (RAMP-CP) ¹³C nuclear magnetic resonance (NMR). Differences between disturbed and undisturbed sites reflected the influence of different botanical inputs (peat vs. forest litter) to SOM composition. Reconstructed soils were characterized by significantly lower alkyl over O-alkyl carbon (ALK/O-ALK) ratios (0.3) than undisturbed sites (0.5). For these reconstructed soils, a significantly higher proportion of soil carbon was present in the sand associated (Heavy sand) pool (49.2 vs. 37.3) and in the acid-unhydrolyzable residue (AUR) fraction (61.3 vs. 54.7). These SOM parameters were significantly related to time since reconstruction, with the AUR (p value = 0.012) and Heavy sand (p value = 0.05) fractions decreasing with time since reconstruction, while the ALK/O-ALK ratio increased (p value = 0.006). These findings suggest that the ALK/O-ALK, AUR, and Heavy sand parameters are suitable indicators for monitoring SOM quality in these reconstructed soils following oil sands mining.     

Salt Marshes on Substrate Enriched in Organic Matter: The Case of Ombrogenic Atlantic Salt Marshes

Ombrogenic Atlantic salt marshes are defined as areas of halophytic, terrestrial vegetation which are periodically flooded by the tide and have a predominant underlying organic substrate comprising of wood and/or Sphagnum peat that formed under freshwater conditions. The objective of this study was to determine to what extent salt marsh plant ecology and, specifically, vegetation composition and zonation relate to this underlying substrate of organic matter (peat). A vegetation survey was carried out on nine salt marshes, three on peat substrate and two on sand, mud and sand/mud, respectively. In parallel, key edaphic variables were measured including pH, conductivity, organic content, moisture content and nutrients: ammonium, nitrate and phosphorus. Salt marshes on peat substrate are distinct. Ammonium content was twice the maximum reported in other salt marsh studies, while the vegetation composition of salt marshes on peat substrate was significantly different from that of other salt marshes. Salt marshes on peat substrate were found to be higher in species diversity and richness and characterised by a predominantly forb and rush community. However, some common salt marsh species, such as Atriplex portulacoides and Spartina anglica were absent from salt marshes on peat. Ordination analysis revealed that zonation was primarily associated with conductivity on peat substrates. In contrast, moisture plays a greater role in zonation within non-peat salt marshes. The findings confirm that the high organic matter content of ombrogenic Atlantic salt marshes is associated with distinct vegetation composition.     

Accumulation behavior of toxic elements in the soil and plant from Xinzhuangzi reclaimed mining areas,China

The concentration and distribution characteristics of toxic elements in soil and plant were investigated in the coal refuse reclaimed areas of Huainan, China. Ninety soil samples from different depth (0–20, 20–40, 40–60 cm) and 120 plant samples were collected based on grid sampling method. The concentrations of the selected toxic elements (As, Cd, Cu, Ni, Pb and Zn) in the soil and plant samples were determined by using inductively coupled plasma mass spectrometry. The elevated concentrations of toxic elements in the soils at the depth of 20–40 and 40–60 cm suggested that the coal refuse reclamation may lead to potential environmental impacts. The toxic element tolerance could be observed in all the selected plant samples. The concentrations of toxic elements in the underground tissues were higher than that of aboveground tissues. Conclusively, the present study provided a comprehensive evaluation of soil and plant toxic element implications from coal refuse reclaimed areas in China and was also helpful for environmental protection and monitoring the safety of plant.     

Sources and transformations of organic matter in surface soils and sediments from a tidal estuary (North Inlet, South Carolina, USA)

Surface soil and sediment samples collected along a forest-brackish marsh-salt marsh transect in a southeastern U.S. estuary were separated into three different fractions (sand, macro-organic matter, and humus) based on size and density. Elemental, stable carbon isotope, and lignin analyses of these samples reveal important contrasts in the quantity, composition, and sources of organic matter, between forest and marsh sites. Elevated nitrogen contents in humus samples suggest nitrogen incorporation during humification is most extensive in forest soils relative to the marsh sites. The lignin compositions of the macro-organic and humus samples reflect the predominant type of vegetation at each site. Lignin phenol ratios indicate that woody and nonwoody litter from, gymnosperm and angiosperms trees (pines and oaks) is the major source of vascular plant-derived organic matter in the forest site and that angiosperm, grasses (Juncus andSpartina) are the major sources of lignin at the marsh sites. The phenol distributions also reveal that oxidative degradation of lignin is most extensive in the forest and brackish marsh zones whereas little lignin decay occurs in the salt marsh samples. In forest soils, most organic matter originates from highly altered forest vegetation while at the brackish marsh site organic matter is a mixture of degradedJuncus materials and microbial/algal remains. Organic matter in the salt marsh appears to be composed of a more complex mixture of sources, including degradedSpartina detritus as well as algal and microbial inputs. Microbial methane oxidation appears to be an important process and a source of¹³C depleted organic carbon in subsurface sediments at this site.     

Comparison of elements of environmental concern in regular and reclaimed soils,near abandoned coal mines Ptolemais–Amynteon,northern Greece: Impact on wheat crops

A comparative study related to the concentrations of trace elements especially those of environmental concern, occurring in regular and reclaimed soils on abandoned coal mines as well as on their respective wheat crops has been undertaken in the vicinity of Ptolemais–Amynteon, Greece. The aim was to assess the impact of land reclamation on the crops.The results of elemental analysis show that the concentration of As is 1.5 to 1.7 times higher in the regular soils than in the reclaimed ones, similarly Co is 2.4 to 2.6 times higher, Cr is 1.7 to 2.8 times higher, Ni is 1.9 to3.1 times higher, Pb is 0.8 to 4.6 times higher, and Hg is equal to or 1.7 times higher. Cu, Cd and Se have the same concentration in both kind of soils and Mo and U are 1.7 to 2.0 times lower in the regular soils as compared to the reclaimed soils. Nevertheless, all concentrations are within the reported range for regular soils.Moreover, the concentrations of the studied elements in wheat grains harvested from both types of soils are approximately the same. The reason for the uniform uptake of elements by the plants is the very low solubility of the elements in the soil solutions. This is attributed to the high soil pH and the nature of the occurrence or bonding of the elements in soil minerals.     

Nitrogen,phosphorus and organic carbon pools in natural and transplanted marsh soils

Total nitrogen, phosphorus and organic carbon were compared in natural and transplanted estuarine marsh soils (top 30 cm) to assess nutrient storage in transplanted marshes. Soils were sampled in five transplanted marshes ranging in age from 1 to 15 yr and in five nearby natural marshes along the North Carolina coast. Dry weight of macroorganic matter (MOM), soil bulk density, pH, humic matter, and extractable P also were measured. Nutrient pools increased with increasing marsh age and hydroperiod. Nitrogen, phosphorus and organic carbon pools were largest in soils of irregularly flooded natural marshes. The contribution of MOM to marsh nutrient reservoirs was 6–45%, 2–22%, and 1–7% of the carbon, nitrogen and phosphorus, respectively. Rates of nutrient accumulation in transplanted marshes ranged from 2.6–10.0, 0.03–1.10, and 84–218 kmol ha^?1yr^?1 of nitrogen, phosphorus and organic carbon, respectively. Accumulation rates were greater in the irregularly flooded marshes compared to the regularly flooded marshes. Approximately 11 to 12% and 20% of the net primary production of emergent vegetation was buried in sediments of the regularly flooded and irregularly flooded transplanted marshes, respectively. Macroorganic matter nutrient pools develop rapidly in transplanted marshes and may approximate natural marshes within 15 to 30 yr. However, development of soil carbon, nitrogen and phosphorus reservoirs takes considerably longer.     

Spatial and seasonal variation of salt ions under the influence of halophytes,in a coastal flat in eastern China

The high salinity of coastal saline field is a key factor limiting the reclamation. Halophytes have been utilized in the reclamation of saline land. The study area is in Yancheng, China. An analysis of the concentrations of Rb, Cs, Sr, and Ba, the ratio of Rb/Cs, and Sr/Ba in soils in autumn shows that the soil of this study area has great homogeneity. Artemisia halodendron, Gossypium hirsutum, and Sesbania cannabina were selected as the reclamation plants in the present study. In order to know the spatial-temporal distribution of soil salinity, the influence of plant-specific vegetation, and the difference of desalination among these halophytes in coastal flat, the authors analyze the soil-layers and seasonal variation in salt ions. Sodium chloride was accumulated in 0–5 cm topsoil with no vegetation during the winter and spring. The effect of desalinization of halophytes is significant. Of the three plant species, Sesbania cannabina has the greatest desalinization. The difference of ions composition of soils covered with various plant species is significant. It can be concluded that halophytes have better amelioration of coastal soil salinity. Special attention should be paid to the selection of plant species and measures to plant and cultivate crops in the reclamation of saline land.     

Wetland soil organic matter composition in a Mediterranean semiarid wetland (Las Tablas de Daimiel, Central Spain): Insight into different carbon sequestration pathways

Wetland soils from a Mediterranean semiarid wetland (Las Tablas de Daimiel, Central Spain) were studied to characterize the organic matter (OM) and determine its origin and transformation. Cross polarization magic angle spinning (CPMAS) ¹³C nuclear magnetic resonance (NMR) spectroscopy and mathematical molecular mixing allowed analysis of the organic fraction in terms of six generic components (carbohydrate, protein, lignin, lipid, char and “carbonyl”). Las Tablas is an active carbon sink, with total organic carbon (TOC) content independent of soil OM quality; the TOC content of the upper sediment is 10.0 ± 7.8%. The inorganic carbon content is also high (5.4 ± 3.3%) and is associated mainly with OM of aliphatic character. The OM composition is variable; samples predominantly aliphatic (carbohydrate, lipid and protein) are characteristic of the northern sector, whereas predominantly aromatic samples are typical of the southern Tablas. A strong negative relationship between protein content and lignin content was found, interpreted as a consequence of different proportions of vascular vs. non-vascular (mostly charophyte) litter input. The effect of perturbation is apparent in the extended presence of char, particularly abundant in fire-prone areas. OM quantity and quality do not seem to depend on hydrology (although seasonal flooding is associated with lower TOC wetland soils) or soil characteristics. Dominant vegetation and fire are the main drivers of OM content and composition. Structural carbohydrate, protein and lipid (>60% of total organic fraction) dominate. Widespread anaerobic conditions and the recent character of the sediments could explain the preservation of different fractions of the original detritus composition (due to different vegetation and presence of microbes).     

Spatial distribution and source of heavy metals in reclaimed lands of Homebush Bay: The venue of the 2000 Olympic Games,Sydney, New South Wales

A large part of the Sydney 2000 Olympic Site at Homebush Bay was reclaimed over several decades using an estimated 9 Mt of domestic, commercial and industrial waste. Past activities, such as reclamation of wetlands, land clearing, shoreline remodelling and industrial practices, have caused an adverse environmental impact on the Homebush Bay site. Core samples (n = 4513) collected from the reclaimed lands of Homebush Bay show that, prior to remediation, soil contaminated by heavy metals (Cr, Cu, Pb, Zn) may have posed a threat to groundwater in the area. Mean Pb concentrations from the three land types at the Olympic site range from 65 to 374 μg/g in reclaimed areas, 78–167 μg/g in landfill areas and 44–52 μg/g in non‐infilled areas, respectively. Heavy‐metal concentrations in soils from non‐infilled areas indicate that these parts of the site were uncontaminated. The distribution of heavy metals in soil samples revealed a close association between elevated concentrations and the presence of fill materials at the site. Metal concentrations were frequently above Australian and New Zealand Guidelines for Fresh and Marine Water Quality. The Olympic Coordination Authority's remediation strategy to clean up the Homebush Bay site included consolidating contaminated waste into landscaped hills, which were capped with impermeable clay and thermal destruction of scheduled waste on site. The primary aims of the current study were to provide a scientific foundation for the remediation/rehabilitation of natural systems, and to make a contribution to the Olympic Coordination Authority's Development Plan and Environmental Management System for the site.