Structural characteristics of clay-dominated soils of a marsh and a palaeosol in a crossed diagram

Although the shrink‐swell phenomenon of clays has been thoroughly studied, the in situ relation of the shrinkage curve to the structure profile is rarely presented from the shrinkage limit to the liquid limit. We studied the consolidated structure of clay‐dominated (<2 μm) soils formed on ‘pseudo‐liquid’ marsh sediments in the ‘Marais de l’Ouest’ (France). The profiles were studied in a grassland field and in a sunflower field from unsaturated surface soils down to deeper, saturated, levels characterized by a very large water content (100% by weight). The consolidation states were quantified recording cone resistance (Qd) profiles using a dynamic penetrometer in successive seasons. These Qd profiles were compared with the associated wet density and gravimetric water‐content profiles. Two consolidation depths were evident, the surface soil and a 130‐cm deep palaeosol. The seasonal Qd profiles demonstrate the partial irreversibility of the consolidation peaks associated with the surface soil and with the palaeosol. The shrinkage properties were established through drying curves of undisturbed test samples. In the void ratio (e)‐water content (W) and water content (W)‐saturation index (Sr) diagrams, the profiles as a whole exhibit only one clay soil behaviour from their pseudo‐liquid to plastic to solid states. Each Qd profile is represented by a hyperbolic curve in the e/Qd diagram. Represented in a (e – W – Qd —Sr) crossed diagram, the vertical evolution of the successive profiles shows the soil structure behaviour from the initial pseudo‐liquid sediment to the consolidated soil. A simple cone resistance recording associated with gravimetric water‐content profiles, characterizes the evolution of structural layers of soils for the seasonal drying‐wetting cycles, for the over‐consolidation associated with the palaeosol, and also for the effect of ploughing.     

Metabolism of metamitron in goat following a single oral administration of a nontoxic dose level: a continued study

Disposition kinetic behavior and metabolism studies of metamitron and its metabolite in terms of the parent compound were carried out in black Bengal goats after a single oral administration of a nontoxic oral dose at 30 mg kg(-1) of body weight. Metamitron was detected in the blood sample at 5 min (2.23 +/- 0.04 microg mL(-1)), maximum at 1 h (3.43 +/- 0.02 microg mL(-1)) and minimum at 12 h (0.41 +/- 0.01 microg mL(-1)), after a single oral administration. Metabolite [3-methyl-6-phenyl-1,2,4-triazin-5(4H)-one] in terms of the parent compound was detected in the blood sample at 5 min (0.47 +/- 0.006 microg mL(-1)), maximum at 6 h (5.12 +/- 0.02 microg mL(-1)) and minimum at 96 h (1.06 +/- 0.016 microg mL(-1)), after a single oral administration. The t(1/2 K) and Cl(B) values of metamitron were 3.63 +/- 0.05 h and 1.36 +/- 0.016 L kg(-1) h(-1), respectively, whereas the t(1/2K)(m) and Cl(B)(m) values of the metabolite were 38.15 +/- 0.37 h and 0.091 +/- 0.001 L kg(-1) h(-1), respectively, which suggested long persistence of the metabolite in blood and tissues of goat. Metamitron was excreted through feces and urine for up to 48 and 72 h, whereas the metabolite was excreted for up to 168 and 144 h, respectively. Metabolite alone contributed to 96 and 67% of combined recovery percentage of metamitron and metabolite against the administered dose in feces and urine of goat, respectively. All of the goat tissues except lung, adrenal gland, ovary, testis, and mammary gland retained the metabolite residue for up to 6 days after administration.     

Use of a 6-steps microcosm for studying a wastewater discharge in a freshwater ecosystem: a multidisciplinary study

An experimental microcosm has been designed for simulating and studying impacts of a wastewater treatment plant (WTP) discharge on a freshwater/sediment ecosystem. The study was focused on the changes in biodiversity of benthic populations, especially bacteria and oligochaetes. Effluents were discharged in the Saône river, near Lyon (France) from a small treatment plant which treated domestic raw water by an activated sludge process. Freshwater and sediments were sampled in the Saône river upstream of the discharge point and placed in microcosms. Following the WTP discharge, physicochemical parameters of the overlying water column and sediments exhibited only a slight change, as compared to a reference. Characterization of the sediment bacterial populations was conducted with the Biolog and API systems. Strain identification and interpretation of data was difficult using thesetwo systems. Bacterial taxa in the sediments increased slightly below the WTP discharge. Gram negative strains dominated in the effluents, but G+ and G- bacteria were balanced in the sediments. Pseudomonas sp. and Bacillus sp., were the dominant strains. Invertebrate populations indicated an effect of the WTP discharge, with increasing of pollution resistant strains (Tubificidae) and disappearance of pollution intolerant strains such as Limnodrilus udekemianus and Quistadrilus multicoetosus. Taken as a whole, biological parameters indicated an environmental changes despite only slight changes in the physicochemistry of water. This experimental microcosm has proven to be a useful tool for studying impact of wastewater discharge on benthic populations.     

Soil microbial recolonisation after a fire in a Mediterranean forest

The capacity of different microbial groups to recolonise soil after a fire event will be decisive in determining the microbial community after the fire. Microbial recovery after a wildfire that occurred in Sierra la Grana (Alicante province, southeast Spain) was tracked for 32 months after the fire. Colony forming units (CFUs) of different microbial groups, microbial biomass, soil respiration, bacterial growth (leucine incorporation) and changes in the microbial community structure (phospholipid fatty acid (PLFA) analysis) were determined directly after the fire and four times during the recovery period. Direct effects were reflected by low values of most microbiological variables measured immediately after the fire. Microbial biomass increased during the first year after the fire but was below the unburned reference site 32 months after the fire. Bacterial activity and soil respiration showed the highest values immediately after the fire, but decreased to values similar to that of the unburned reference site or even lower (respiration) 32 months after the fire. Colony forming units of bacterial groups estimated by the plate count method peaked 8 months after the fire, but then decreased, showing values similar to the unburned reference site at the end of the study, with the exception of spore formers, which were 20 times higher than the reference site 32 months after the fire. Fungal CFUs were more sensitive to the fire and recovered more slowly than bacteria. Fungi recovering less rapidly than bacteria were also indicated by the PLFA pattern, with PLFAs indicative of fungi being less common after the fire. The recovery of microbial biomass and activity was mirrored by the initially very high levels of dissolved organic carbon being consumed and decreasing within 8 months after the fire. The wildfire event had thus resulted in a decrease in microbial biomass, with a more bacteria-dominated microbial community.     

Surface-bound phosphatase activity in ectomycorrhizal fungi: a comparative study between a colorimetric and a microscope-based method

For the quantification of surface-bound phosphomonoesterase activity (SBPA) of fungi, roots, or mycorrhiza, a colorimetric method based on p-nitrophenyl phosphate (pNPP) is widely used. Unfortunately, this method does not reveal information about the localization of the surface-bound phosphomonoesterase (SBP). We introduce a method that localizes and quantifies SBPA in living hyphae of ectomycorrhizal fungi using confocal laser scanning microscopy of the hydrophilic substrate enzyme-labelled fluorescence (ELF-97) and compare it to the pNPP assay. ELF-97 turns into a strongly fluorescent precipitate upon activation by SBPA and forms bright fluorescent centres on the outer cell wall of the hyphae. Our data show that the enzymatic reaction is not substrate-limited during an incubation period of 15 min in fungal hyphae of Pisolithus tinctorius, Cenococcum geophilum, and Paxillus involutus. Image-processing routines determined the total intensity and the average number of the fluorescent ELF-97 centres per micrometre fungal hyphae of C. geophilum and Paxillus involutus. ELF-97 and pNPP detected similar variations of the SBPA at different pH values (3–7) during the measurement and different phosphorus (P) concentrations during the growth period of the fungi. The ELF-97 method revealed that C. geophilum and Paxillus involutus adapt in different ways to the variation of the P concentrations during the growth period by varying the number, the activity, or both properties of the SBP centres. The phosphatases show peak activities at different pH values, so the response of the fungal mycelium to varying P concentrations in soils is pH selective. In conclusion, ELF-97 is a promising substrate to reveal SBPA and adaptation strategies on a structural–physiological level.     

Improvement of a Gravity Oil Separator Using a Designed Experiment

Several authors have pointed out the need to improve the design procedure of conventional oil-water separator. In this work, a batch test and various continuous runs based on a Plackett-Burman statistical plan were performed, in order to optimize a small (10 L/min) gravity oil-water separator technology intended to pre-treat wastewaters from vehicle service facilities. The results from the tracer tests realized did not show a coherent relationship between the performance of the separator (E) and the mixing regime qualified by means of the variable ε (ratio between the actual and nominal mean residence times). The statistical analysis showed that the oil removal efficiency variations (69-82%) were mainly dictated by the way the separator is configured. A two-step design procedure alternative of small gravity separators was suggested.     

Physiological interpretation of a hyperspectral time series in a citrus orchard

Hyperspectral remote sensing for monitoring horticultural production systems requires the understanding of how plant physiology, canopy structure, management and solar elevation affect the retrieved canopy reflectance during different stages of the phenological cycle. Hence, the objective of this study was to set up and to interpret a hyperspectral time series for a mature and healthy citrus orchard in the Western Cape province of South Africa considering these effects. Based on the remotely sensed data, biophysical parameters at the canopy level were derived and related to known observed physiological and phenological changes at the leaf level and to orchard management. Fractions of mature fruit, flowers, and sunburnt leaves were considered, and indices related to canopy structure chlorophyll content and canopy water status were calculated.Results revealed small cover fractions of mature fruit, flowers and sunburnt leaves of respectively 2.1%, 3.1% and 7.0%, but the high spectral contrast between flowers and leaves allowed a successful classification of flowering intensity. Furthermore, it was shown that canopy level time series of vegetation indices were sensitive to changes in solar elevation and soil reflectance which could be reduced by applying an empirical soil line correction for the most affected indices. Most trends in vegetation indices at the canopy level could be explained by a combination of changes at the leaf level (chlorophyll, carotenoids, dry matter), changes in canopy structure (leaf area index and leaf angle distribution) and changes in cover fractions of vegetative flushes, flowers and sunburnt leaves. The transformed chlorophyll absorption ratio index over the optimised soil adjusted vegetation index (MCARI/OSAVI) was best related to leaf level trends in chlorophyll content. Seasonal changes in the photochemical reflectance index (PRI) were linked to inverse changes in the carotenoid-to-chlorophyll ratio. Canopy structure indices (the modified triangular vegetation index or MTVI2 and the standardized leaf area index determining index or sLAIDI) were sensitive to changes in leaf area index, average leaf angle as well to management interactions (pruning and harvest). Canopy water status was highly impacted during the spring flush due to expanding leaves that concealed trends in the underlying mature leaves. Seasonal trends in soil and weeds reflectance were related to changes in volumetric soil water content and to the earlier and reduced growth period of non-irrigated weeds.     

Cyanides in a soil of a former coking plant site

Soils of former coking plant sites are frequently contaminated with cyanide, which mainly occurs as the pigment Berlin blue, Fe^III4 [Fe^IICN)₆]₃, and soluble iron cyanide complexes, Fe(CN)₆^3-/4?. Berlin blue is only slightly soluble under acidic conditions. The cyanide mobility in a strongly acid soil (pH about 3) of such a site was studied by assessing the distribution of cyanides in the soil and sediment and by conducting batch experiments at different pH levels. The soil is based on a disposal layer (0–32 cm) overlying sandy loess (32–145 cm) overlying glaciofluvial sand (145–250 cm) overlying marlstone (250–500 cm). Highest cyanide concentrations were found in the disposal layer (62–2865 mg CN^? kg^?1), medium concentrations in the sandy loess (16–29 mg CN^? kg^?1), concentrations of about 100 mg CN^? kg^?1 in the glaciofluvial sand and lowest concentrations in the marlstone (0.22–0.49 mg CN^?1 kg^?1). The surfaces of macropores, which occur in the sandy loess and finish in the glaciofluvial sand, are dark-blue dyed and have much higher cyanide concentrations than the surrounding bulk soil. Thus, the accumulation of cyanides in the sand layer may partly be the result of macropore flow. Batch experiments show a strong pH dependence of the solubility of cyanide in the soil as well as of Berlin blue which was found by Mössbauer spectroscopy to be the dominating or sole iron cyanide. The time necessary to transport the cyanides solely as hexacyanoferrate into the undisturbed horizons is estimated to 1000 yr. However, because Berlin blue is known to form colloids, we discuss the possibility of cyanide transport as colloid not requiring dissolution and reprecipitation. We postulate that colloidal Berlin blue transported by macropore flow is responsible for the high mobility of cyanides in this acid soil.     

Dynamics of a black bear population within a desert metapopulation

Understanding metapopulation dynamics in large carnivores with naturally fragmented populations is difficult because of the large temporal and spatial context of such dynamics. We coupled a long-term database of visitor sighting records with an intensive 3-year telemetry study to describe population dynamics of recolonization by black bears (Ursus americanus) of Big Bend National Park in Texas during 1988-2002. This population, which occurs within a metapopulation in western Texas and northern Mexico, increased from a single pair of known breeding-age animals in 1988 to 29 bears (including 6 females of breeding age) in March 2000 (λ = 1.25/year). A migration and dispersal event in August-December 2000 reduced the population to 2 adult females and as few as 5-7 individuals. One-way movement distances from the study area during this event averaged 76 km for females (n = 7) and 92 km for males (n = 4), and 3 animals conducted migrations of at least 154, 178, and 214 km, respectively. Our observations exemplify the importance of stochastic events on demographics of small populations and highlight the potential scale of bear movement among montane islands of southwestern North America. They also provide insight into the use of dispersal data in parameterizing metapopulation models for large carnivores.     

Comparison of a novel distillation method versus a traditional distillation method in a model gin system using liquid/liquid extraction

This research studied a novel form of distillation (high vacuum distillation) as a method for preserving volatile aroma chemicals important to the organoleptic attributes of a four botanical model gin as well as the degradation products generated during the heating required in traditional methods of gin distillation. A 2 (5) factorial experiment was conducted in a partially confounded incomplete block design and analyzed using the PROC MIXED procedure from SAS. A model gin was made of dried juniper berries (Juniperus communis), coriander seed (Coriandrum sativum), angelica root (Angelica archangelica), and dry lemon peel (Citrus limonum). This was distilled on a traditional still utilizing atmospheric pressure and a heating mantel to initiate phase separation as well as a novel still (high vacuum) utilizing high vacuum pressures below 0.1 mmHg and temperatures below -15 degrees C to initiate phase separation. The degradation products (alpha-pinene, alpha-phellandrene, E-caryophyllene, and beta-myrcene) were present at greater levels (approximately 10 times) in the traditional still-made gin as compared to the novel gin.     

Factors controlling aggregation in a minimum and a conventionally tilled undulating field

Wind and water erosion induce breakdown of soil aggregates and loss of soil organic matter. Whereas most of the relations between aggregation and its driving factors have been established on a plot scale, these relations might be very different within an undulating landscape where both erosion (by wind or water) and deposition occur. The aim of this study was to investigate to what degree spatial patterns in soil variables influence spatial patterns in aggregation under different tillage intensities. We studied an agricultural field of about 3 ha in the silty region of Belgium. The site was split into a conventional tillage (CT) and a minimum tillage (MT) system. Within the field, 396 geo‐referenced surface soil samples (0–5 cm) were taken and analyzed for organic matter content, quantity of aggregates and a number of other soil properties. Under CT, 28.5% of the total sample variation was explained by the occurrence of depositional areas, 20.8% by the amount of soil organic matter, and 13.8% by the presence of a clay‐rich B horizon which surfaced due to progressive water and tillage erosion. Regression analysis revealed that 27% of the variation in the quantity of macroaggregates (>0.25 mm) was accounted for by these three factors. Under MT, 27.1% of the total sample variation was related to the surface cover of Tertiary sand, 22.6% to the amount of soil organic matter, and 13% to erodibility. These three factors explained 53% of the variation in the quantity of macroaggregates. In the CT system, the correlation between grass‐ or maize‐ carbon and the quantity of macroaggregates was strongly linked to erodibility, while this was not the case in the MT system. We concluded that at this site, macroaggregation is dominated by landscape‐scale processes (such as water or tillage erosion) rather than determined by the commonly considered local variables (such as small variations in texture or organic matter content).     

Efficient hydrolysis of tuna oil by a surfactant-coated lipase in a two-phase system

A surfactant-coated lipase (SCL) prepared by mixing Candida rugosa lipase with emulsifier in ethanol was used to hydrolyze tuna oil in a two-phase aqueous-organic system. Both enzyme (SCL) and substrate (tuna oil) were soluble in the organic phase, and the hydrolysis could occur with water molecules from the aqueous phase. This hydrolysis could promptly proceed compared to that catalyzed by native lipases which only occurred at the interface between the two phases. Michaelis-Menten kinetics in the two-phase reactions showed that the K(m) value of the SCL was half that of the native lipase, while the maximum velocity (V(max)) was 11.5 times higher. The hydrolysis method resulted in enrichment of n-3 polyunsaturated fatty acid (n-3 PUFA) content in glyceride mixtures from 26.4% to 49.8% and DHA from 19.1% to 38.9%. The SCL acted as an efficient hydrolytic catalyst for tuna oil.     

Effects of a New-Type Cleaning Agent and a Plant Growth Regulator on Phytoextraction of Cadmium from a Contaminated Soil

In China, great efforts are being made to remediate farmlands polluted by heavy metals. In this study, a soil pot experiment was conducted to examine the effects of a new-type cleaning agent, methylglycinediacetic acid(MGDA), and a plant growth regulator(PGR), diethl aminoethyl hexanoate(DA-6), on plant growth and extraction and detoxification of cadmium(Cd) by ryegrass. The results showed that foliar spray of DA-6 alone improved plant growth, with root length and shoot dry biomass increased by 38.5%–58.6% and 71.1%–89.3%, respectively, whereas addition of MGDA alone decreased root length and shoot dry biomass by 10.3%–18.6%and 9.1%–21.8%, respectively. Diethl aminoethyl hexanoate promoted the binding of Cd to cell walls and thus alleviated the toxicity of Cd and/or MGDA to plants. Applications of DA-6 and/or MGDA resulted in a significant increase in Cd extraction efficiency(P 0.05), and the efficiency decreased in the order of MGDA + DA-6 DA-6 MGDA. The treatment of MGDA + DA-6 achieved 2.2%, 1.7%, and 0.8% Cd extraction efficiency by ryegrass in soils spiked with 25, 50, 100 mg Cd kg~(-1), respectively. Therefore,treatment of MGDA + DA-6 could be an efficient method for enhancing phytoremediation of Cd-contaminated soil by ryegrass.     

Differences in Lead Bioavailability Between a Smelting and a Mining Area

Soils and housedusts were collected from three areas of Pribram,an historic metal mining and smelting town in the Czech Republic. The main objectives of the study were: (i) to assessthe influence of physico-chemical form, particle size, soilproperties and contaminant source on Pb bioavailability andexposure risk; (ii) compare the Pb bioavailability data obtainedfrom the mining and smelting areas and assess whether anydifferences observed could be attributed to the factors thoughtto exert an influence. Lead concentrations were highest in thesmelter area. Mining area garden soils also contained elevatedPb concentrations. Solubility of housedust Pb in 0.12 M HCl (asurrogate for stomach acid) was similar in all study areas andwas similar to values reported in the literature. However, 0.12M HCl solubility of garden soil Pb was low in the mining areacompared to the other study areas and compared to other urbanareas. Blood Pb concentrations were also relatively low in themining area compared to the other study areas and the reducedsoil Pb solubility observed in this area was suspected as aninfluencing factor. However, exposure pathways may also beimportant in explaining the differences observed.     

Cotton lint yield variability in a heterogeneous soil at a landscape scale

Landscape variability associated with topographic features affects the spatial pattern of soil water and N redistribution, and thus N uptake and crop yield. A landscape-scale study was conducted in a center pivot irrigated field on the southern High Plains of Texas in 1999 to assess soil water, soil NO₃-N, cotton (Gossypium hirsutum L.) lint yield, and N uptake variability in the landscape, and to determine the spatial correlation between these landscape variables using a state-space approach. The treatments were irrigation at 50 and 75% cotton potential evapotranspiration (ET). Neutron access tubes were placed at a 15-m interval along a 710 m (50% ET) and 820 m (75% ET) transect across the field. Soil NO₃-N in early spring was autocorrelated at a distance varying between 60 and 80 m. Measured soil volumetric water content (WC), total N uptake, and lint yield were generally higher on lower landscape positions. Cotton lint yield was significantly correlated to soil WC (r=0.76), soil NO₃-N (r=0.35), and site elevation (r=−0.54). Differences of site elevation between local neighboring points explained the soil water, NO₃-N and lint yield variability at the micro-scale level in the landscape. Soil WC, cotton lint yield, N uptake, and clay content were crosscorrelated with site elevation across a lag distance of ±30–40 m. The state-space analysis showed that cotton lint yield was positively weighted on soil WC availability and negatively weighted on site elevation. Cotton lint yield state-space models give insights on the association of soil physical and chemical properties, lint yield, and landscape processes, and have the potential to improve water and N management at the landscape-scale.     

Determination of ochratoxin a with a DNA aptamer

This work describes the identification of an aptamer that binds with high affinity and specificity to ochratoxin A (OTA), a mycotoxin that occurs in wheat and other foodstuffs, and a quantitative detection method for OTA based on the use of this aptamer. Aptamers are single-stranded oligonucleotides selected in vitro to bind to molecular targets. The aptamer selected in this work exhibited a dissociation constant in the nanomolar range and did not bind compounds with structures similar to OTA such as N-acetylphenylalanine or warfarin. The aptamer bound with a 100-fold less affinity to ochratoxin B. The selected aptamers could be used for the determination of ppb quantities of OTA in naturally contaminated wheat samples. Further work is ongoing to broaden the application demonstrated here with the development of sensors, affinity columns, and other analytical systems for field and laboratory determination of this toxin in food and agricultural products.     

生物表面活性剂及Tween-80在一株菲降解菌降解过程中的作用研究

Numerous studies have been devoted to the physical-chemical weathering processes leading to the creation of unique soil formations having their own history that induce soil-biotic diversity. However, the extent to which unique geomorphic formations influence soil biotic seasonal variation is not clear. Our aim was to define seasonal variations of soil biota in soils of different-aged terraces of the Makhtesh Ramon anticline erosional cirque in southern Israel. The strong effect of Makhtesh Ramon (Ramon Crater) erosional fluvial terrace age initiated by climatic changes during the Late Pleistocene–Early Holocene period on seasonal variations in both soil properties and the abundance and composition of soil biota were demonstrated. However, age dependence was not constant and values for observed soil properties and microbial activity were negligible between younger and older terraces for certain seasons, while free-living nematodes along with bacteria-feeding group were strongly dependent on the geomorphic features of the ages throughout the study period.     

DOC leaching from a coniferous forest floor: modeling a manipulation experiment

The DyDOC model simulates the C dynamics of forest soils, including the production and transport of dissolved organic matter (DOM), on the basis of soil hydrology, metabolic processes, and sorption reactions. The model recognizes three main pools of soil C: litter, substrate (an intermediate transformation product), and humic substances. The model was used to simulate the behavior of C in the O horizon of soil under a Norway spruce stand at Asa, Sweden, that had been subjected to experimental manipulations (addition and removal) of above‐ground litter inputs and to removal of the Oi and Oe layers. Initially, the model was calibrated using results for the control plots and was able to reproduce the observed total soil C pool and ¹⁴C content, DOC flux and DO¹⁴C content, and the pool of litter C, together with the assumed content of C in humic substances (20% of the total soil C), and the assumed distribution of DOC between hydrophilic and hydrophobic fractions. The constant describing DOC exchange between micro‐ and macropores was estimated from short‐term variations in DOC concentration. When the calibrated model was used to predict the effects of litter and soil manipulations, it underestimated the additional DOC export (up to 33%) caused by litter addition, and underestimated the 22% reduction in DOC export caused by litter withdrawal. Therefore, an additional metabolic process, the direct conversion of litter to DOC, was added to the model. The addition of this process permitted reasonably accurate simulation of the results of the manipulation experiments, without affecting the goodness‐of‐fit in the model calibration. The results suggest that, under normal conditions, DOC exported from the Asa forest floor is a mixture of compounds derived from soil C pools with a range of residence times. Approximately equal amounts come from the litter pool (turnover time 4.6 yr), the substrate pool (26 yr), and the humic‐substances pool (36 yr).     

Halide analysis in soils with a chloride titrator and a bromide electrode

Abstract

An araperometric titration method for Cl was suitable for reproducible analysis of equimolar Cl. Br and I in all possible combinations in the range 0.125 to 2.50 millimolar (mM). A solid state Br specific ion electrode exhibited a reproducible Nernstian response to Br over the range 0.005 to 1 mM, with minimal Cl interference. Bromide and Cl added to a lysimeter and a field were quantitatively recovered by estimation of (Cl + Br) amperometrically and Br potentiometrically.     

Should the Sediment Quality Triad Become a Tetrad, a Pentad, or Possibly even a Hexad?

Background, Aim and Scope  

The Sediment Quality Triad (SQT) as originally developed 20 years ago involved three lines of evidence (LOE): sediment chemistry, sediment toxicity, and benthic community structure. The first two LOE have been consistently included in all SQTs conducted to date, however the last LOE has been changed to 'alteration of resident communities' and, in some cases has been excluded or replaced. In other cases additional LOE have been added to the SQT. Materials and Methods