High Amounts Of Organic Matter Research Articles

The stability of tidal flats in Venice Lagoon—the results of in-situ measurements using two benthic, annular flumes

Seabed properties in Venice Lagoon were examined in situ in two multidisciplinary field campaigns. The purpose of this study was to understand the mechanisms controlling the stability of bed types. Two benthic annular flumes (Sea Carousel and Mini Flume) were deployed simultaneously from a floating pontoon at 24 sites during summer (1998), which were considered representative of the range in bed/habitat types. As well, bottom sampling and coring, water-column monitoring and benthic habitat analyses were carried out. All but three sites were on cohesive sediments. Bed types included bare shelly mudflats and regions colonised by the seagrasses Cymodocea nodosa and Zostera noltii, by filamentous cyanobacteria, and by patches of the macrophytes Ulva rigida and Chaetomorpha sp. A subset (13) of these sites was visited during the subsequent winter to evaluate seasonal changes. Six of the sites were intertidal, the remainder were in the sublittoral zone. Water temperature varied between 5 and 30 °C, and salinity varied between 20 and 38 psu. In the absence of waves, turbidity was generally low (<10 mg/l) and was composed of high amounts of organic matter (25–50%). This indicates that the tidal flows were not competent to support estuarine sediment. Higher levels of turbidity were measured during wind events or boat passage as a result of resuspension from the bed. Bed (saturated) density was, on average, 1770 kg/m 3, which was extremely high for estuarine sediments. Sea Carousel and Mini Flume provided comparable results, despite large differences in instrument footprints. Trends from the two instruments were similar and showed that summertime bed strength exceeded the winter by up to five times. Mean summer erosion thresholds for Sea Carousel and Mini Flume were 1.10 and 0.82 Pa, respectively, whereas during winter, they were 0.69 and 0.74 Pa. The northern lagoon had the most resistant tidal flats due to the stabilizing effect of filamentous cyanobacteria (Biostabilization Index: BI=244%), microphytobenthos (BI=153%) and Z. noltii (BI=206%). The stabilizing effects of C. nodosa (BI=74%), U. rigida (BI=115%) and shell debris (BI=115%) were intermediate, while bare sublittoral mud beds were the least resistant (BI=58%). Summer erosion rates (as a function of applied stress) were lower than winter ones, probably due to water temperature changes. The algorithm E= χτ s β , yielded good results and indicated that erosion rates in Venice Lagoon were high, notwithstanding the high erosion thresholds. The mean summertime friction coefficient was φ=62° and was highest in the central lagoon. The wintertime φ=69° showed that there was no seasonal fluctuation in bed stability. Mass settling in Venice Lagoon was a strong function of suspended sediment concentration ( S) and a decay constant ( k) of the exponential function S( t)= S o e − kt ; it was found to be in continuity with examples from other locations worldwide (and therefore normal).

Do co-occurring plant species adapt to one another? The response of Bromus erectus to the presence of different Thymus vulgaris chemotypes.

Local modification of the soil environment by individual plants may affect the performance and composition of associated plant species. The aromatic plant Thymus vulgaris has the potential to modify the soil through leaching of water-soluble compounds from leaves and litter decomposition. In southern France, six different thyme chemotypes can be distinguished based on the dominant monoterpene in the essential oil, which is either phenolic or non-phenolic in structure. We examine how soils from within and away from thyme patches in sites dominated by either phenolic or non-phenolic chemotypes affect germination, growth and reproduction of the associated grass species Bromus erectus. To do so, we collected seeds of B. erectus from three phenolic and three non-phenolic sites. Seeds and seedlings were grown on soils from these sites in a reciprocal transplant type experiment in the glasshouse. Brome of non-phenolic origin performed significantly better on its home soil than on soil from a different non-phenolic or a phenolic site. This response to local chemotypes was only observed on soil collected directly underneath thyme plants and not on soil in the same site (<5 m away) but where no thyme plants were present. This is preliminary evidence that brome plants show an adaptive response to soil modifications mediated by the local thyme chemotypes. Reproductive effort was consistently higher in brome of phenolic origin than in brome of non-phenolic origin (on both thyme- and grass-soil), indicating that life-history variation may be related to environmental factors which also contribute to the spatial differentiation of thyme chemotypes. Moreover, we found that brome growing on thyme-soil in general was heavier than when growing on grass-soil, regardless of the origin of the brome plants. This is concordant with thyme-soil containing higher amounts of organic matter and nitrogen than grass-soil. Our results indicate that patterns of genetic differentiation and local adaptation may modify competitive interactions and possible facilitation effects in natural communities.

Effect of soil composition on adsorption of lead as reflected by a study on a natural forest soil profile

The adsorption characteristics of lead on each genetic horizon of a natural brown forest soil profile were studied to recognize the possible immobilizing effect of a mineralogical diverse soil profile in the case of a possible lead contamination. Lead adsorption experiments were carried out on whole soil samples, soil clay fractions, as well as on their carbonate and organic matter free variant. TEM-EDS analyses were performed to characterize the adsorption capacity of individual mineral phases. The most important lead adsorbents in order of importance are the organic matter, the clay minerals, and the iron oxides. The most significant process is the ion exchange of calcium by lead with the respect to adsorption. The organic matter adsorbs more lead than clay minerals, and clay fractions adsorb more lead as compared to the whole soil samples. Among mixed layer clay minerals, those containing swelling component have the highest lead adsorption capacity, but the exact distinguishing of the individual clay mineral particles with the respect to their adsorption capacity is not possible. The calcite influences the lead adsorption through its buffering capacity: high calcite content results in lead precipitation. Soils characterized by high amount of organic matter, swelling clay mineral accumulation horizon and calcareous subsoil are suitable medium to immobilize a significant lead pollution.

Simultaneous determination of fluoroquinolone, sulfonamide, and trimethoprim antibiotics in wastewater using tandem solid phase extraction and liquid chromatography–electrospray mass spectrometry

A robust and sensitive method for the detection of fluoroquinolones, sulfonamides and trimethoprim has been developed. Wastewater samples were acidified and extracted through an anion-exchange cartridge in tandem with a hydrophilic–lipophilic balance (HLB) cartridge, a procedure that reduced interferences from wastewater organic matter. The extracted antibiotics were analyzed using liquid chromatography electrospray mass spectrometry and selected ion monitoring. Quantification of antibiotics was assessed both by internal standard and standard addition methods. Average recoveries for a range of wastewater matrices were 37 to 129% for a 1 μg/L spiking concentration. The method detection limits (MDLs) of antibiotics in deionized water, final and secondary effluent ranged from 2 to 7 ng/L, from 20 to 50 ng/L, and from 30 to 90 ng/L, respectively. Assessment of matrix interference shows that signal suppression and MDL increases with higher amounts of organic matter in the sample. Analyses of samples from two municipal wastewater treatment plants indicate that ciprofloxacin, ofloxacin, sulfamethoxazole and trimethoprim are present in the secondary effluents at median concentrations of 100–160, 205–305, 395–575, and 40–705 ng/L, respectively.

Deep macrobenthic communities from Nazaré Submarine Canyon (NW Portugal)

Macrofauna community structure within Nazare Submarine Canyon is analysed and used to assess the potential effects of natural enrichment in this area subjected to accumulation of coastal sediments. A transect including three stations (2894, 3514 and 4141 m) was carried out in the Nazare Submarine Canyon (NW Portugal) during a cruise of OMEX II programme (Ocean Margin Exchange), in the winter season of 1999. Although data was not collected in order to calculate sedimentation rates, sampling station at 2894 m is located in an area characterised by high levels of sedimentation, thus a high amount of organic matter is expected to be available for the local communities. Faunistic data are discussed in the context of the different features of the stations sampled. Multivariate analysis clearly separates the shallowest station from the other ones, which otherwise appear to be very similar. It also revealed a perceptible gradient along sediment depth at all stations, from shallow to deeper layers. Exceptionally depressed species richness and low evenness values were observed at the 2894 m station. The high number of individuals of a single species, Cossura sp. A, and the atypical diversity, dominance and evenness values obtained for this station support the hypothesis of community disturbance due to organic enrichment.

Some Physico-chemical characteristics of soils influenced by Taal Volcano in reference to soil productivity

Soils of the northwestern part of the Taal Volcano in the Philippines representing four geomorphological units (upper, middle, and lower slopes and alluvial plains) were investigated and related to soil productivity. Results revealed that the soils on the upper and middle slopes contained higher amounts of organic matter and available P and displayed a low P retention together with more favorable physical properties such as loamy soil texture, loose and friable and well-drained soils compared to those on the lower slopes and in the alluvial plains. Due to these favorable soil characteristics, sustained agricultural production was higher at the upper elevations than at the lower elevations. Year-round multistorey / mixed cropping systems of cultivation in the upper and middle landscapes were also made possible because the higher precipitation was evenly distributed coupled with cooler temperatures compared the conditions on the lower slopes and in the alluvial plains. On the other hand, the soils on the lower slopes and in the alluvial plains had a clayey texture and contained a lower amount of organic matter and available P, in addition to the lower precipitation, resulting in reduced land utilization, as indicated by the limited types of crops grown and lower yield of crops.

Bacterial populations of the floodplain of a South Carolina (USA) stream: A comparison of two species

The distributions of two bacterial populations (Acinetobacter calcoaceticus and Pseudomonas putida) across the floodplain of a coastalplain stream (Four Mile Creek in South Carolina) were examined. In addition, populations in two areas of the floodplain with different vegetation were compared. One site (FOU 1) featured a typical bottomland hardwood forest with abundant stocks of leaf litter and the other site (FOU2) featured a plant community dominated by grasses/shrubs/herbs with limited amounts of leaf litter. Despite a higher amount of organic matter in the soil at FOU1, total bacterial numbers were greater at FOU2. A. calcoaceticus numbers peaked in the water saturated portion of the floodplain while P. putida numbers peaked at the more elevated edge of the floodplain. Differences in floodplain populations were not apparently related to differences in populations within the stream channel.

Seasonal and spatial heterogeneity in the water chemistry of two sewage-affected saline shallow lakes from central Spain

The seasonal features of the water chemistry in the saline shallow lakes Laguna de Manjavacas and Laguna del Pueblo (Castilla – La Mancha, Central Spain) were studied during 1990–1991 and in 1997. These lakes were both affected by sewage inputs driving them to a high trophic status. However, whereas sewage inputs entered Laguna del Pueblo directly, wastewater reached Laguna de Manjavacas after running for 8 km through a small riverbed, where natural processes caused partial mineralisation of organic matter. Moreover, water quality was further improved before entering the main water body of Laguna de Manjavacas, since water crossed through a wetland and high amounts of organic matter and inorganic nutrients were retained there. Anyway, in both lakes spatial heterogeneity was mainly associated with the distance to sewage inputs, and this was also reflected by the sediment chemistry. The patterns of water evaporation and precipitation-dissolution of salts strongly determined the salinity of their waters. During the warmest period (which coincided with the main drought period) water losses by evaporation increased water salinity, whereas a higher dilution was found during the cold rainy period. However, the relatively higher amount of low-salinity sewage inputs in Laguna del Pueblo allowed this lake to maintain its hyposaline characteristics. In contrast, Laguna de Manjavacas shifts from hyposaline to hypersaline following the seasonal cycle with different rain and temperature regimes, as the relative importance of the permanent wastewater inputs was lower here than in Laguna del Pueblo. Inorganic nutrient dynamics was determined in both lakes both by the sewage supply and by consumption by phytoplankton, with soluble P depletion following algal blooms.

Distribution and origin of shallow gas in deep-sea sediments of the Ulleung Basin, East Sea (Sea of Japan)

A synthesis of high-resolution (Chirp, 2–7 kHz) subbottom profiles in the Ulleung Basin reveals patchy distribution of shallow (<90 m subbottom depth) gassy sediments in the eastern basin plain below 1,800-m water depth. The shallow gases in the sediments are associated with acoustic turbidities, columnar acoustic blankings, enhanced reflectors, dome structures, and pockmarks. Analyses of gas samples collected from a piston core in an earlier study suggest that the shallow gases are thermogenic in origin. Also, published data showing high amounts of organic matter in thick sections of marine shale (middle Miocene to lower Pliocene sequence) and high heat flow in the basin plain sediments are consistent with the formation of deep, thermogenic gas. In multi-channel deep seismic profiles, numerous acoustic chimneys and faults reflect that the deep, thermogenic gas would have migrated upwards from the deeper subsurface to the near-seafloor. The upward-migrating gases may have accumulated in porous debrites and turbidites (upper Pliocene sequence) overlain by impermeable hemipelagites (Quaternary sequence), resulting in the patchy distribution of shallow gases on the eastern basin plain.

Assessing the recovery potential of solid waste in Mauritius

A study was initiated to assess the recovery potential of solid waste in Mauritius. The solid waste generated in a residential area has been quantified and characterized using direct weighing, physical testing and truckload sampling methods. Data on quantities of solid waste and waste composition has been collected for six months to assess for seasonal variation in solid waste generation rates. The current situation concerning resource recovery and disposal of solid waste in Mauritius is also described. Alternative decisions of solid waste appropriate with local conditions are discussed. It has been seen that the average solid waste generation rate is around 1.3 kg/capita per day and that wastes generated in winter were significantly different from wastes generated in the summer seasons. The composition (on a weight basis) of the solid wastes sampled was as follows: food wastes 25%, yard waste 43%, plastics 13%, paper 12%, textiles 3%, metals 1% indicating a high amount of organic matter. Vegetable and food wastes from the kitchen and yard wastes accounted for more than 60% of the waste stream. The moisture content was around 48% and the calorific value of the mixed wastes around 18 800 kJ/kg on a dry weight basis. The nature of the wastes indicate that amongst the recovery options, composting at household level would be most appropriate as it would divert more than 60% of the wastes from the traditional waste stream and provide households with compost which could be used to enrich soils in the kitchen gardens.

Effect of earthworm cast formation on the stabilization of organic matter in fine soil fractions

To study the effects of earthworm casting on organic matter dynamics, control soil and casts were added as a surface layer ( Horizon I) to perspex cylinders containing a ‘base’ soil depleted in organic C ( Horizon II). Three treatments with different Horizon I were used; a control containing uningested soil and oak litter ( Quercus petraea (Mattuschka) Lieblein), cast derived from the same substrates, and a third ( Ew+cast) where cast as well as endogeic ( Aporrectodea caliginosa Savigny, Allolobophora chlorotica Savigny) and anecic ( Lumbricus terrestris L.) earthworms were included. These were monitored over a 2 1 2 year period. Moisture fluctuations were reduced and higher amounts of organic matter and C were present in Horizon I with the cast treatment after 2 years. In addition, the proportion of clay C (and to a lesser extent light fraction) in Horizon I decreased significantly in the control and cast treatments while there was a corresponding increase in the proportions of silt C. Overall, earthworm activity had a limited effect on C distribution in the particle size fractions studied, though the dynamics of organic matter/particle associations may require more than 2 1 2 years before clear patterns emerge.

Microbially available organic carbon, phosphorus, and microbial growth in ozonated drinking water

Ozonation is a disinfection technique commonly used in the treatment of drinking water. It destroys harmful microbes, but it also degrades organic matter in water, increasing the bioavailability of organic matter. Recently, it was found that not only organic carbon but also phosphorus can limit the microbial growth in drinking water, which contains high amount of organic matter. We used a bioassay to analyze whether ozone could also increase the microbially available phosphorus (MAP) in drinking water, and whether MAP in ozone-treated water was associated with the growth of heterotrophic microbes. We found that both assimilable organic carbon and MAP concentrations were increased by ozone treatment. In ozonated water, microbial growth was mainly limited by phosphorus, and even minor changes in MAP concentration dramatically increased the growth potential of heterotrophic microbes. In this study, ozonation increased the MAP by 0.08–0.73 μg P/l, resulting in an increase of 80,000–730,000 CFU/ml in water samples. In contrast to MAP, the content of assimilable organic carbon (AOC potential) did not correlate with microbial growth. The results show that in water treatment not only AOC potential but also MAP should be considered as an important factor that can limit microbial growth in drinking water.

The Posidonia Shale (Lower Toarcian) of SW-Germany: an oxygen-depleted ecosystem controlled by sea level and palaeoclimate

The Lower Toarcian Posidonia Shale is famous for its excellently preserved fossils and its high amount of organic matter (up to 16%). Both quality of preservation and accumulation of organic matter have been explained by permanent anoxic bottom water conditions. High-resolution geochemical, sedimentological and palaeoecological investigations of various sections of the Posidonia Shale in SW-Germany, however, indicate that oxygen availability was variable and ranged from short oxygenated periods to longer-term anoxia. The benthic macrofauna consists of nine fossil communities and was used, in combination with geochemical data, to reconstruct a time-averaged oxygen curve. Anoxic conditions prevailed during the deposition of the Toarcian black shales; they were, however, punctuated by various short periods (weeks to years) with oxygenated bottom water conditions. Sedimentological (e.g. distinctiveness of microlamination, siliciclastic content) and geochemical parameters (e.g. organic matter content, isotopic signatures: δ 18O and δ 13C, molecular redox parameters: pristane/phytane ratio, arylisoprenoids) exhibit a remarkable covariation and seem to be controlled by sea level fluctuations. Maximum oxygen depletion and an extreme negative shift of δ 13C org values (−34‰) occurred during the early falciferum-zone. This is explained by the recycling of 12C-enriched carbon derived from remineralization of organic matter on and within the substrate during low sea level stand and a highly elevated redox boundary including photic zone anoxia. The subsequent transgression permitted enhanced water exchange with the Tethyan Ocean and caused improvement of living conditions at the end of the falciferum-zone. Other important factors controlling the depositional environment are the overall palaeogeographic situation and climate. The early Jurassic is the latest period before break-up of Pangaea and probably was ruled by a strong meridional atmospheric circulation system with pronounced seasonal changes of prevailing trade- and monsoon-wind systems. An estuarine circulation with a positive water balance and surface water with slightly reduced salinity in the summer alternated with an anti-estuarine circulation and a negative water balance in the winter. During the summer months a stratified water column with anoxic conditions below the halocline developed. δ 18O data indicate low salinity in the surface water during the monsoon-influenced summer. High productivity was then located in the photic zone and the corresponding isotopically light δ 18O-signal was fixed in the calcareous nannoplankton. During the winter months a saline circulation system brought oxygen to the benthic environment, favouring temporary benthic colonization, especially during times of relative sea level high stand.

Sedimentological and biostratigraphical analyses of short sediment cores from Hagelseewli (2339 m a.s.l.) in the Swiss Alps

Several short sediment cores of between 35 and 40 cm from Hagelseewli, a small, remote lake in the Swiss Alps at an elevation of 2339 m a.s.l. were correlated according to their organic matter content. The sediments are characterized by organic silts and show in their uppermost part a surprisingly high amount of organic matter (30-35%). Synchronous changes, occurring in pollen from snow-bed vegetation, the alga Pediastrum, chironomids, and grain-size composition, point to a climatic change interpreted as cooler or shorter summers that led to prolonged ice-cover on the lake. According to palynological results the sediments date back to at least the early 15th century A.D., with the cooling phase encompassing the period between late 16th and the mid-19th century thus coinciding with the Little Ice Age. Low concentrations of both chironomid head capsules and cladoceran remains in combination with results from fossil pigment analyses point to longer periods of bottom-water anoxia as a result of long-lasting ice-cover that prevented mixing of the water column. According to our results aquatic biota in Hagelseewli are mainly indirectly influenced by climate change. The duration of ice-cover on the lake controls the mixing of the water column as well as light-availability for phytoplankton blooms.

SILURIAN — LOWER DEVONIAN BLACK SHALES IN MOROCCO: WHICH ARE THE ORGANICALLY RICHEST HORIZONS?

Lowermost Silurian (Rhuddanian, lower Llandovery) black shales represent the main Palaeozoic petroleum source rock throughout North Africa and Arabia. The unit also occurs in parts of Morocco with recorded TOC values of up to 10.5%. However, in contrast to many other North African and Arabian countries, the Silurian‐Lower Devonian shale‐dominated succession in Morocco also contains a number of other horizons with elevated organic contents. In order to evaluate the organic richness and better understand the depositional mechanisms of this shale succession in Morocco, samples were collected from petroleum exploration wells, from the spoil heaps of shallow water wells and from outcrops, and were subsequently analysed. Graptolite biostratigraphy provided a high‐resolution correlation framework. The data was integrated with that from published and unpublished studies, and the results may help in improved predictions of the source quality of Silurian—Lower Devonian strata in Morocco.An Aeronian (middle Llandovery) shale sample with a high organic content (4.35% TOC) was recovered from the NE margin of the Tadla Basin, central Morocco. Based on gamma‐ray data from the subsurface, however, this horizon appears to be laterally discontinuous within the basin. Secondly, late Telychian‐Wenlock shales from the eastern Atlas Mountains were found to have TOC values of around 2.5%, and may be correlated with age‐equivalent organic‐rich strata in the Ghadames Basin (eastern Algeria, western Libya, southern Tunisia) and Iraq. Late Silurian shale‐limestone alternations in Morocco apparently do not contain major amounts of organic mattel; although comparable deposits in parts of western Algeria are believed to be organic rich. Early Devonian graptolitic black shales from the Tadla Basin and its margins contain high amounts of organic matter (around 5% TOC); however; the lateral continuity of this unit is at present unclear.We propose that high primary productivity during the Silurian‐Early Devonian provided the basis for the formation of these organic‐rich shales in Morocco. Sea level changes may have been an important additional factor. For example, the Rhuddanian organic‐rich shales were deposited during the initial stages of a transgression, when circulation was still restricted due to the pronounced pre‐Silurian relief. At other times during the Silurian‐Early Devonian in Morocco, deposits with elevated organic content seem to have been formed during periods of high sea level, which may have been associated with high primary productivity and/or a rise in the oxygen minimum zone onto the shelf.

Sorption of trichloroethene onto stylolites

Batch and double reservoir diffusion cell experiments are used to investigate sorption of trichloroethene onto stylolites. Stylolites are common features in carbonate rock formations, and might contain high amounts of organic matter. Due to the hydrophobic character of TCE, its transport in fractured carbonate aquifers could be significantly affected due to these aforementioned features. No research has been carried out to evaluate the impact of stylolites on organic pollutant transport. The main objectives of this experimental research are to verify TCE sorption onto stylolites, and to derive sorption and diffusion parameters describing the solute/rock interaction. Test results show that stylolites from the Lockport Formation in Southern Ontario, Canada contain significant amounts of organic carbon. Discrepancies are noted between carbon analyzer data and estimates from batch experiments and these might be due to TCE sorption also onto a clay mineral phase in stylolites or due to selective sampling. Adsorption and desorption behavior of TCE is investigated in specially designed double reservoir diffusion cells made out of stainless steel and Teflon. Three semi-analytical solutions for one-dimensional, reactive tracer migration through a porous medium are derived and used to evaluate TCE time–concentration profiles. Experimental data can best be modeled using a kinetic Langmuir sorption formulation with a maximum sorption capacity of 1.3 to 4.6 μg/g and a kinetic sorption constant of 4×10 −7 to 5×10 −7 l/mg s −1. TCE desorption into the exit reservoir is found to be a very slow kinetic process. No retardation is observed during TCE migration through a clay and organic matter free dolostone sample. TCE seems not to interact with calcareous mineral phases and moves conservatively. Bromide diffusion curves yield geometry factors ( γ) for dolostone ranging between 0.05 and 0.13. From this study it can be concluded that TCE sorption is of importance when modeling TCE migration in fractured, stylolitic limestone aquifers where diffusion into the rock matrix takes place. Temporal TCE storage in rock matrix stylolites and fracture wall stylolites has to be taken into consideration when evaluating actions of remediation at organic spill sites.

Copper and zinc adsorption by sewage sludge‐treated soil in southern Spain

Heavy metal accumulation in soil due to the application of sewage sludge may induce changes in its ionic retention capacity. In this work, sludge application effects on copper (Cu) and zinc (Zn) adsorption by the surface horizon of a calcareous soil in Southern Spain have been studied. Sludge from the urban waste water treatment plant in Cordoba was applied at rates of 0,40, and 80 Mg sludge ha‐1 for two consecutive years. Despite the low metal content of this sludge and the high amount of organic matter added, a decrease in the soil adsorption levels for both Cu and Zn was detected in the sludged samples. Differences were observed, though, in the behavior of each metal, relative to the main adsorption mechanism involved. Copper adsorption was related to carbonate surfaces in soil. Values up to 400 mmol adsorbed Cu kg‐1 soil were obtained for the three treatments, in equilibrium with 13.6, 16.7, and 17.4 mmol Cu m‐3 in solution for 0, 40, and 80 Mg sludge ha‐1, respectively, the first year, and 13.9, 21.2, and 52.2 mmol Cu m‐3 in solution the second year. However, an increase of soil Cu availability is not likely to arise during or after continuous application of these sludge doses, due to the high calcium carbonate content of this soil. In the case of Zn, adsorption took place in CEC sites, with values up to 40 mmol adsorbed Zn kg‐1 soil in the 0 and 80 Mg sludge ha‐1 samples, in equilibrium with 158.3 and 164.5 mmol Zn m3 in solution, respectively the first year, and 196.1 and 505.8 mmol Zn m3 in solution the second year, whereas in the 40 Mg sludge ha‐1 samples adsorption was below 25 mmol Zn kg‐1 soil, in equilibrium with 171.1 mmol Zn m3 in solution the first year, and 231.0 mmol Zn m‐3 the second year. As soil CEC values and its organic matter content are positively related, Zn availability in this soil could be expected to increase after the cessation of sludge applications, due to the mineralization of the organic matter added.

Origin and transformation of organic matter in Pliocene–Pleistocene Mediterranean sapropels: organic geochemical evidence reviewed

Drilling of deep-water post-Messinian sedimentary sequences by ODP Legs 160 and 161 in the Mediterranean Sea has shown that occurrence of organic-carbon-rich sapropels and sapropel-like sediments extends from the Levantine Basin westward into the Alboran Basin. In the eastern Mediterranean, sapropel deposition started in the Early Pliocene, whereas in the Western Basin the onset of sapropel formation occurred later, in the Early Pleistocene. Precessional cycles are apparently the primary external forcing for sapropel formation. Nevertheless, the pattern of sapropel occurrence suggests that the precessional influence is modulated by the glaciation cycles. Large differences were observed in the organic carbon contents of sapropels recovered in the eastern and western Mediterranean. Correspondence between organic carbon contents, Rock-Eval hydrogen index values and elemental C/N ratios indicate that both variations in the production and preservation of marine organic matter have led to the accumulation of high amounts of organic matter in sapropels. Molecular organic geochemical compositions of sapropels from the eastern Mediterranean further confirm that the major fraction of organic matter in sapropels is derived from marine algal sources and has undergone variable oxidation. Enhanced marine productivity and improved preservation of organic matter is central to sapropel formation. Accumulation of increased amounts of land-derived material at times of sapropel formation is also evidenced, supporting the hypothesis of significant periodic freshwater discharges.

Pollution history of a tropical estuary revealed by combined hydrodynamic modelling and sediment geochemistry

Hydrodynamic modelling of water movement in Hunts Bay, a protected part of Kingston Harbour, Jamaica, shows that depth averaged tidal flows are very low. In the northeast corner of Hunts Bay, water is essentially stagnant. Even under high flow conditions, much of the Bay bottom water is `bypassed' by buoyant, lower salinity surface flows. The muddy sediments of Hunts Bay reflect these sluggish to stagnant conditions; sediment cores from the northeast corner of the Bay contain progressively higher amounts of organic matter in their upper parts (∼last 15–20 years sedimentation). Combined C/N ratios and stable carbon isotope compositions of this organic matter imply a sewage origin. Both lead and chromium metal concentrations and enrichment factors relative to average crustal shales show geographically related patterns that reflect hydrodynamic circulation predicted by modelling. In particular, metal concentrations and enrichment factors are highest at the northern end of the bay, especially in the northeast corner. Modelling confirms that stagnant conditions would occur in the northeast part of the bay even without the presence of a major causeway. The causeway may contribute to low flow conditions, but is not the principal cause of organic contamination, which is simply an excessive input of sewage.

Sedimentary and diagenetic markers of the restriction in a marine basin: the Lorca Basin (SE Spain) during the Messinian

The Lorca Basin (southeastern Spain) is part of a chain of small marginal Neogene basins located in the structurally active Betic area. The Upper Miocene (Messinian) sequence is composed of a thick diatomite-bearing series (Tripoli Unit) overlain by the Main Evaporites, analogous to the classical succession that records the main events during the Salinity Crisis in the Mediterranean region. The shallow restricted conditions of this region amplified the sedimentary responses to local and global forcings. An integrated approach using sedimentology, micropalaeontology, stable isotope geochemistry and organic geochemistry has been applied to the Tortonian/Messinian succession of the Lorca Basin, in order to obtain a continuous record of the environmental changes. The sediments record two major events which affected the whole Mediterranean: (1) high levels of productivity that led to the formation of the diatomite-bearing deposits in the early Messinian (Tripoli); and (2) the Messinian Salinity Crisis with its two major stages, represented by the Halite and Gypsum Units, both mainly precipitated from marine-derived brines. The rapid reflooding of the Mediterranean by normal marine waters at the base of the Pliocene did not reach the Lorca Basin, nor other basins of this part of the Betic area. Instead, continental sediments were deposited as a consequence of the regional uplift of SE Iberia, which started close to the Messinian/Pliocene boundary. The most prominent feature of this basin concerns the record of its restriction by the time of the deposition of the Tripoli Unit, which led to intercalations of precursor evaporitic layers, consisting of Ca-sulphate deposited in sub-aqueous and sabkha conditions, interbedded with diatomites. This alternation of evaporites and diatomites proves that the Lorca Basin was periodically restricted and reflooded by marine waters, a possible cause for this being relative sea-level fluctuations in the Mediterranean. This strengthens evidence of diachronism that suggests that the onset of the first Messinian evaporitic deposition was not synchronous, but was dependent on bathymetry and local tectonics. High productivity during the early Messinian in this basin is demonstrated by the thick deposits of diatomites. However, stagnation episodes may have occurred during this interval, as suggested by the preservation of high amounts of organic matter (organic-rich shales) and the extent of bacterial sulphate reduction which apparently occurred during early diagenesis. The formation of organo-sulphur compounds, replacement of sulphates by carbonates and the high levels of elemental sulphur are by-products of diagenetic processes occurring in a restricted hypersaline environment.