Margarita Osterrieth

Fate of organochlorine pesticides in soils and terrestrial biota of “Los Padres” pond watershed, Argentina

Abstract Concentrations of organochlorine pesticides (OCPs) in soils and associated biota around “Los Padres” pond watershed were determined by gas chromatography with electron capture detector (GC–ECD). Pesticides were analyzed in different horizons (upper 0–15, middle 15–30, lower 45–55 cm) of natural and horticultural soils, developed in highlands and lowlands. Physical and chemical characteristics (organic matter content, pH, moisture, texture, etc.) were determined. Higher concentrations of total OCPs were found in highlands, because of the high content of clay material and organic matter. Lindane, heptachlor, aldrin, DDT and metabolites were found in soils. Depending on physical and chemical characteristics of pesticides and soils, different behaviours were found. Lindane could leach down to lower horizons, rich in clays, while hydrophobic pesticides remain in the upper horizons, retained by organic matter. Vegetables (carrots and potatoes) accumulated lindane with important contributions of DDTs and heptachlor. OCPs were taken up, accumulated and metabolized efficiently by terrestrial invertebrates (earthworms and beetles). The results obtained testify the pollution by OCPs in “Los Padres” pond watershed.

Phytolith analysis of Cyperaceae from the Pampean region, Argentina.

Cyperaceae, along with Poaceae, is the main silica accumulator. Although the anatomical-taxonomic and palaeobotanical relevance of phytoliths has been well established, there are no studies that deal with the qualitative and quantitative aspects of the phytolith production or differentiate phytoliths from the different organs in Cyperaceae. Toward the construction of a detailed database of phytolith production, we describe in the present paper the phytoliths of leaves, culms and fruits of Cyperaceae from Pampean region (Argentina). Phytoliths were extracted by a calcination technique. Qualitative and quantitative characters and percentages of phytolith morphotypes were subject to principal component analysis to analyse their taxonomic relevance. For some sedges, values of phytolith content and a comparative analysis of leaves, culms and fruit phytoliths are presented here for the first time. Diverse tissues such as epidermis, xylem, parenchyma and sclerenchyma produced phytoliths. The most abundant morphotypes were conical phytoliths, which showed differences in the base shape and in their size between organs. Leaf/culm cones have a rounded, rectangular or square base; typical fruit cones have a polygonal base and they are bigger and more robust. PCA showed that quantitative and qualitative characters of cones, along with the percentages of morphotypes, allowed group distinction.

Agricultural soil as a potential source of input of organochlorine pesticides into a nearby pond

A study was conducted in the southeastern region of Buenos Aires province, Argentina, to assess an agricultural soil as a potential source of organochlorine (OC) pesticides for the aquatic biota of a nearby pond. We analyzed γ-HCH (lindane), still in use, and the following banned compounds: DDT, DDE, DDD heptachlor, heptachlor epoxide, aldrin, dieldrin and endrin in soil, bulrush, grass shrimp and fish using gas chromatography with electron capture detection (GC-ECD). Among the OC pesticides, lindane was most dominant in the soil (32.6 ng/g dry wt in the upper and 173.9 ng/g dry wt in the lower horizon) and bulrush (1.9 μg/g lipid). Macrophyte also accumulated high levels of heptachlor epoxide (1.5 μg/g lipid). Heptachlor, although present in the soil, was below the detection limit in all aquatic biota studied. Its primary degradation product, heptachlor epoxide, was found in both soil and biota samples. DDT was found at low levels in the surface soil (6.8 ng/g dry wt), but at higher concentrations in fish (3.6 μg/g lipid), although levels were still below permissible levels for human consumption. Since most of the compounds were found in both soil and aquatic biota, our study suggests that agricultural soil could be an important source for OC pesticides in the nearby pond.

Paleosols on Late Cainozoic loessic sequences in the northeastern side of Tandilia Range, buenos aires, Argentina

Abstract The purpose of this work is to describe and characterize paleosols from Late Cainozoic loessic sequences in the northeastern flank of Tandilia Range. Pedological and non-pedological levels are described, considering the vertical (thickness, color, texture and structure) and horizontal (lateral pattern) development. Mineralogical, grain size, physico-chemical features are analyzed in type profiles. This study recognizes two groups of paleosols associated with distinct paleoenvironmental conditions: (I) paleosols which are regionally continuous and extensive, related to moisture conditions wetter than the present ones, showing truncated and superimposed profiles; (II) paleosols related to water bodies, showing uneven distribution which are mainly topographically controlled. Sediments that have undergone pedogenesis are identified by their morphological, physico-chemical, textural and mineralogical characteristics and bioturbation features. The history of pedogenesis and erosion is related to the alternating humid-arid climatic cycles, that have affected the region since the Plio-Pleistocene, to the present.

Trichoderma koningii as a biomineralizing fungous agent of calcium oxalate crystals in typical Argiudolls of the Los Padres Lake natural reserve (Buenos Aires, Argentina).

The aim of the present study, performed on typical Argiudolls in a natural reserve with little or no anthropic impact, was to characterize the fungous biomineralizing process of calcium oxalate crystals in organic horizons of the soil. The chosen sites possessed different plant cover, identified as acacia woods and grassy meadows with particular micro environmental conditions that have differing effects in the process of biomineralization. The contribution of the plant material in the soil is a key factor since 1) it generates the particular composition of the organic horizons, 2) it determines the nature of decomposing organisms, and 3) it affects the presence, composition and development of biominerals. According to the results obtained, the acacia woods prove to be a site comparatively more favorable to the fungous biomineralizing process. This makes itself manifest in the greater abundance and development of crystals in the organic horizons of the soil, resulting in whewellite (CaC2O4.H2O) and weddellite (CaC2O4.(2+x) H2O) regarding biomineral species developed, the latter being the major component. The observation of both species of biominerals is noteworthy since it represents the first cited in the country. The isolated fungous organisms were Trichoderma koningii, and Absidia corymbifera. T. koningii was identified as the most active biomineralizing organism thus constituting the first reference to indicate this species as a biomineral producing agent.

Trace metal pyritization variability in response to mangrove soil aerobic and anaerobic oxidation processes

The degree of iron pyritization (DOP) and degree of trace metal pyritization (DTMP) were evaluated in mangrove soil profiles from an estuarine area located in Rio de Janeiro (SE Brazil). The soil pH was negatively correlated with redox potential (Eh) and positively correlated with DOP and DTMP of some elements (Mn, Cu and Pb), suggesting that pyrite oxidation generated acidity and can affect the importance of pyrite as a trace metal-binding phase, mainly in response to spatial variability in tidal flooding. Besides these aerobic oxidation effects, results from a sequential extraction analyses of reactive phases evidenced that Mn oxidized phase consumption in reaction with pyrite can be also important to determine the pyritization of trace elements. Cumulative effects of these aerobic and anaerobic oxidation processes were evidenced as factors affecting the capacity of mangrove soils to act as a sink for trace metals through pyritization processes.

Silicification of the adaxial epidermis of leaves of a panicoid grass in relation to leaf position and section and environmental conditions

Many studies relate silica content in plants with internal or external factors; however, few works analyse the effect of these factors on the silicification of different cell types. In this study, we examined the effect of leaf section and leaf position, and environmental conditions on the percentages of silicified epidermal cells of a native Pampean panicoid grass, Bothriochloa laguroides D. C. Pilger. Two different environmental situations were selected for the collection of plants: a natural wetland and a quartzite quarry, located in the southeast Buenos Aires province, Argentina. Clarification and staining methodologies were applied so as to study the distribution of silicified cells in different sections of leaves of the plants collected. Two and three-factor anovas were applied to the data. Between 13% and 19% of total cells of the adaxial epidermis of leaf blades were silicified. Typical silica short cells were the largest contributor to total silicified cells (53-98%), while the second largest contributor was bulliform cells (0-30%). Percentages of total silicified cells were higher in superior than in inferior leaves, while values from leaf sections varied. When collection sites were compared, plants growing in Los Padres pond, where the silica content in soils is higher, had the higher percentage of silicified cells. Among all types of cell, bulliform cells showed differences in the proportion of silicified cells between leaf position and section and collection site. These results show that silica availability in soils is an important factor that conditions silica accumulation and overlaps with the transpiration effect.

First report of phytoliths in the air of Argentina

A first analysis of airborne phytoliths was carried out in Mar del Plata, Argentina. Its primary aims were to characterize the phytolith morphotypes present in the atmosphere, to quantify their abundance and to detect whether seasonal variations exist throughout the year. The standard method was used for monitoring airborne particulate matter applying a Hirst-type suction bioaerosol sampler. The mean daily phytoliths concentrations (p/m3) were calculated for eight selected days from the driest year, 1993, bearing in mind that its atmospheric conditions could favour the presence of biomineralizations in the air. The amount of phytoliths reached was of 1,543. It was composed of 61% isolated and 1% articulated types. The rest were unknown or unidentified phytoliths (38%). The most abundant morphotypes (72.1% of those identified) were elongates, followed by rondels (16.1%) already described for Poaceae subfamilies, such as Pooideae and Stipoideae. Finally, trapeziform and point shaped were identified with 3.8 and 3.4%, respectively. A lower abundance of silica particles was detected on high wind speed days from the south (sea coast) and under wetter conditions. Maximum phytoliths concentrations were recorded in winter when pasture burning is carried out alongside ploughing; this also coincides with the period in which soils were not covered by vegetation. These results shed light on the importance of considering the potential ways of phytoliths dispersion and the factors that could be affecting their aerial transport, especially when they are applied to the interpretation of paleovegetation from phytolith fossil records.

Amorphous silica biomineralizations in Polytrichum strictum Menzies ex Brid. (Bryophyta)

Abstract In this study, the presence of amorphous silica biomineralizations (silicophytoliths) in individuals of Polytrichum strictum collected from Tierra del Fuego, Argentina was analysed. Gametophyte and sporophyte samples were subjected to calcination and staining techniques, through which the biomineralizations obtained were observed and described by optical and scanning electron microscopes. Lastly, their composition was analysed by energy dispersive spectroscopy. In both gametophyte and sporophyte silica skeletons comprising thin elongated silicophytoliths with blunt, round or acute ends were observed. These morphologies may correspond to the silicification of the costa or midrib region of the leaves (in the gametophyte) and the seta (in the sporophyte) and to the silicification of the awns of the leaves. The other morphologies found were silica skeletons comprising silicified walls of tabular polygonal cells, probably derived from the silicification of the cells of the unistratose lamina of leaves. Energy dispersive spectroscopy analyses and the use of a phenol-staining technique confirmed the silicon composition of these biomineralizations. The results obtained comprise the first description of amorphous silica biomineralization in mosses and the implications of the silicification process in this taxon are discussed. The data obtained will be relevant not only for anatomical, but also for palaeobotanical studies, since the preservation of these structures in the soil after the decomposition of organic matter, might allow the identification of mosses in the fossil record.

Calcium Oxalate Crystals in Plant Communities of the Southeast of the Pampean Plain, Argentina

Calcium oxalate crystals (COC) are one of the most prevalent and widely distributed biomineralizations in plants. The aim of this work is to analyze and compare the data previously reported about the presence and production of COC in leaves of plant species from forests, wetlands, and agroecosystems of the southeast of the Pampean Plain. Diaphanization, clearing of tissues with 50% sodium hypochlorite, and cross sectioning of the leaves were realized. The material was mounted with gelatin–glycerin, and COC were identified and described with optical, polarization, and scanning electron microscopes. Crystal size and density were calculated. Calcification mainly occurred in leaf mesophyll. In terrestrial species, crystals were closely associated with vascular bundles, while in aquatic species, they were associated with aerenchyma. Druses, prisms, and raphides were observed in the leaves of all species analyzed. Average crystal size was smaller in terrestrial species than aquatic ones (12 and 80 μm, respectively), but average crystal density was higher (246 and 23 crystals/mm2, respectively). These different patterns in COC production and distribution may be related to taxonomical characteristics, the types of cells where crystals precipitate, their function, and the differential transpiration rates, among other factors.