Uwe Herpin

Soil carbon storage prediction in temperate hydromorphic soils using A morphologic index and digital elevation model

Because soils are both a source and a sink for atmospheric CO2, there is an increasing need to characterize the spatial distribution of soil C pools. Large amounts of organic carbon (OC) accumulate in hydric bottom-lands soils. In the Armorican Massif (Western France) where these soils represent 20% of the total surface area, the spatial characterization of OC pools is difficult to assess due to methodological problems such as high spatial variability. Soil color indexes, which combine various characteristics of soil horizons or profiles, are an alternative approach for quantifying the differences in OC storage. In addition, terrain attributes derived from Digital Elevation Models (DEM) may be useful in characterizing the distribution of soil color indexes over large areas. Thus, the overall goal of this work was the development and application of a model for use in predicting the organic carbon (OC) content of soil areas. To accomplish this, extensive examination of soil morphology combined with selected terrain attributes measured in the field and calculated from a digital elevation model (DEM) were used. Soil samples were collected in Western France from a 2-ha agricultural parcel that forms the major part of a hillslope. The results indicate that OC stocks of the entire profile were correlated highly to a soil hydromorphic index (HI) (r2 = 0.80). HI is a function of the percent of the total soil profile depth constituted by horizons with some degree of hydromorphic feature development and the moist color of the surface A horizon. Using a stepwise regression technique, we constructed a prediction model of HI distribution by using the relations between HI and (i) the elevation above the stream bank (ES) (r2 = 0.80); (ii) the downslope gradient (DG) (r2 = 0.55); and (iii) the upslope contributing area (AMU) (r2 = 0.60). Validation of this model on a second site showed that topographical attributes explained up to 75% of the profile OC stock variability. These results confirmed that the integration of a soil index and topographical information is a useful tool for prediction of OC distribution. In addition, the use of soil morphologic indexes could significantly improved the construction and the validation of soil-landscape models because it would minimize laboratory measurements of OC reservoirs.

Agricultural use of treated sewage effluents: agronomic and environmental implications and perspectives for Brazil

In many studies worldwide the use of treated sewage effluents (TSE) as water and nutrient sources in agricultural irrigation have been introduced as a viable alternative for wastewater destination in the environment. Considering agronomic and environmental aspects the objectives of this review were: (i) to present an overview of TSE irrigation on different agro-systems (annual crops, orchards, forests and forages); and (ii) to show the principal changes on chemical, physical and microbiological soil characteristics after TSE application. Various studies have revealed that the nutrient supply only by TSE irrigation was not sufficient to meet plant nutrient requirements resulting in yield decreases. The problem could be solved by an adapted effluent/fertilizer management. Moreover, TSE could generally substitute efficiently freshwater for irrigation. Regarding soil quality conditions, TSE irrigation affected mainly: (i) total soil carbon and nitrogen, and mineral nitrogen in soil solution; (ii) microbial activity, composition of microbial communities and their function; (iii) exchangeable calcium and magnesium; (iv) salinity, sodicity, clay dispersion and hydraulic conductivity. Other soil parameters considered in this review (e.g. heavy metals) did not present significant changes over short and medium terms. Due to the often observed accumulation of sodium and nitrogen losses (leaching, volatilization and denitrification) after TSE irrigation, the monitoring of these components is of crucial importance for a sustainable use. Finally, further studies on the technical-economical-environmental viability of TSE irrigation are required to establish reliable recommendations for TSE use particularly in Brazilian agro-systems.

Reclaimed wastewater: Impact on soil-plant system under tropical conditions

This study investigated the ionic speciation of reclaimed urban wastewater (RWW), and the impact of increasing RWW irrigation rates on soil properties and plant nutrition under field conditions. Most RWW elements (>66%) are readily available as NH(4)(+), Ca(2+), Mg(2+), K(+), SO(4)(2-), Cl(-), H(3)BO(3), Mn(2+) and Zn(2+), but in imbalanced proportion for plant nutrition. Lead, Cd, Cr and Al in RWW are mostly bounded with DOM or OH(-).(.)Irrigation with RWW decreased soil acidity, which is beneficial to the acidic tropical soil. Although RWW irrigation builds exchangeable Na(+) up, the excessive Na(+) was leached out of the soil profile after a rainy summer season (>400 mm). Benefits of the disposal of RWW to the soil under tropical conditions were discussed, however, the over irrigation with RWW (>100% of crop evapotranspiration) led to a nutritional imbalance, accumulating S and leading to a plant deficiency of P and K.

On the road from environmental biomonitoring to human health aspects: monitoring atmospheric heavy metal deposition by epiphytic/epigeic plants: present status and future needs

For the past few years, a strong and intensive combined study by analytical scientists and biologists on bioindication and biomonitoring has developed. To achieve a more public-related prophylactic healthcare feature derived from these biotechniques in the future, the collaboration between analytical scientists, ecotoxicologists and especially human toxicologists has to be strongly intensified and promoted. For this purpose, different forms of education and teaching of students on an international level combined with common research projects encompassing the different scientific fields and philosophies are important keys for common success.

Biogeochemical dynamics following land use change from forest to pasture in a humid tropical area (Rondônia, Brazil): a multi-element approach by means of XRF-spectroscopy

Forest burning for pastures in tropical areas represents an important component of biogeochemical cycles. In order to provide information concerning chemical modifications after forest burning, in this local study the total contents of 29 elements in topsoils were analyzed when forest is changed to pasture land. The work was carried out in 1999 in Rondĵnia state (Brazilian Amazon Basin) focussing on a native forest site and four neighboring pastures established in 1987, 1983, 1972 and 1911 after forest conversion. Chemical fingerprint graphs of the pasture soils related to the forest soil illustrated mainly higher contents for the vast majority of macro- and micro nutrients, but for other elements as well (e.g. Ba, Sr, Cr, Ni, V or Pb). Also increases of pH levels were measured in all pastures, which remained higher than the forest values for decades. After initial increases of most of the elements in pasture of 1987 the decreases of some macro elements (e.g. C, N, K, Mg, S) in pasture 1983 as well as again the enhanced levels in pasture 1972 and 1911 suggest both a persistent leaching of these elements and a function of pasture age where external element inputs exceed outputs. Ash deposition, accumulation of organic matter, animal excreta as well as natural soil conditions are discussed as influencing factors on the element contents of the original forest and the pasture soils. Nevertheless, in this particular area continuous pasturing after forest clearing primarily enriched the soils in elements.

Conversion of cerrado into agricultural land in the south-western Amazon: carbon stocks and soil fertility

Land use change and land management practices can modify soil carbon (C) dynamics and soil fertility. This study evaluated the effect of tillage systems (no-tillage - NT and conventional tillage - CT) on soil C and nutrient stocks in an Oxisol from an Amazonian cerrado following land use change. The study also identified relationships between these stocks and other soil attributes. Carbon, P, K, Ca and Mg stocks, adjusted to the equivalent soil mass in the cerrado (CE), were higher under NT. After adoption of all but one of the NT treatments, C stocks were higher than they were in the other areas we considered. Correlations between C and nutrient stocks showed positive correlations with Ca and Mg under NT due to continuous liming, higher crop residue inputs and lack of soil disturbance, associated with positive correlations with cation exchange capacity (CEC), base saturation and pH. The positive correlation (r = 0.91, p < 0.05) between C stocks and CEC in the CE indicates the important contribution of soil organic matter (SOM) to CEC in tropical soils, although the exchange sites are - under natural conditions - mainly occupied by H and Al. Phosphorus and K stocks showed positive correlations (0.81 and 0.82, respectively) with C stocks in the CE, indicating the direct relationship of P and K with SOM in natural ecosystems. The high spatial variability of P and K fertilizer application may be obscuring these soil nutrient stocks. In this study, the main source of P and K was fertilizer rather than SOM.

Phytoremediation of lead by jack beans on a Rhodic Hapludox amended with EDTA

Este estudo teve como objetivo avaliar, em condicoes de casa de vegetacao, os efeitos do acido etilenodiamino tetraacetico (EDTA) no potencial fitoextrator do feijao-de-porco (Canavalia ensiformis L.). Amostras de um Latossolo Vermelho distrofico foram tratadas com seis doses de Pb (0, 100, 200, 350, 1.200 e 2.400 mg kg-1 de solo) aplicadas como Pb(NO3)2 com e sem a aplicacao de EDTA (0 e 0,5 g kg-1, respectivamente) e colocadas em vasos. A concentracao de Pb2+, Cl-, NO3-, NH4+, SO42-, H2PO4-, Zn2+, Cu2+, Fe3+, Al3+, Ca2+, Mg2+, K+ e COD (carbono orgânico dissolvido) foram determinadas no extrato de saturacao (razao solo:agua de 1:0,3) e utilizadas para especiacao ionica atraves do software Visual-Minteq 2.30. A disponibilidade de Pb foi avaliada com solucao extratora de acido dietilenotriamino pentacetico (DTPA). O solo tratado com EDTA apresentou maior concentracao de Pb (como PbEDTA2-) e Fe (como FeEDTA-) na solucao do solo levando a maior absorcao destes elementos pelo feijao de porco. Por outro lado reduziu a concentracao das especies Pb-COD e Fe-COD. O EDTA tambem contribuiu com melhor nutricao da planta devido ao aumento da concentracao de outros nutrientes (Ca, K, Mg, Zn, Cu, Fe e Mn) na parte aerea. A producao de materia seca foi constante mesmo para as doses mais altas de Pb no solo. O feijao-de-porco possui potencial fitorremediador. O extrator DTPA foi efetivo em avaliar a disponibilidade de Pb para as plantas para todas as doses de Pb aplicadas.

Heavy metals in emergent trees and pioneers from tropical forest with special reference to forest fires and local pollution sources in Sarawak, Malaysia

Leaf samples of tropical trees, i.e. Dryobalanops lanceolata (Kapur paji), Dipterocarpaceae and Macaranga spp. (Mahang), Euphorbiaceae were analyzed for 21 chemical elements. The pioneer Macaranga spp. exhibited higher concentrations for the majority of elements compared to the emergent species of Dryobalanops lanceolata, which was attributed to the higher physiological activity of the fast growing pioneer species compared to emergent trees. Lead showed rather high concentrations in several samples from the Bakam re-forestation site. This is suggested to be caused by emissions through brick manufacturing and related activities in the vicinity. A comparison of Dryobalanops lanceolata samples collected in 1993, 1995 and 1997 in the Lambir Hills National Park revealed that certain heavy metals, i.e. Co, Cu, Mn, Ni, Pb and Ti showed higher values in 1997 compared to the previous years, which could indicate an atmospheric input from the haze caused by the extensive forest fires raging in Borneo and other parts of Southeast Asia.

Nitrogen forms, pH and total carbon in a soil incubated with treated sewage effluent

In this study, an experiment under controlled conditions was carried out to determine the effects of secondary-treated sewage effluent (STSE) application on soil nitrogen concentrations (mineral and total), total carbon and soil pH. The soil and STSE used were collected at Lins, Sao Paulo State, Brazil. A completely randomized design was used, in completed factorial 4x11 (weekly application rates of 0, 100, 150 and 200 mL STSE per kg soil; and, eleven soil incubation periods from 0 to 10 weeks) with four replicates. The STSE was applied simulating common surface irrigation. Seven days after each incubation period, ammonium and nitrate contents were determined. Additionally, pH and total carbon and nitrogen contents were measured in the soil after 10 weeks. STSE application increased the nitrogen content (total and mineral - mainly as nitrate) and soil pH. For the total carbon content no differences were observed.

Expansão dos solos hidromórficos e mudanças na paisagem: um estudo de caso na região Sudeste da Amazônia Brasileira

In the Southwestern Brazilian Amazon, a detailed study on the pedological cover of a representative toposequence for the region, characterized by lowered plateaus with topographic depressions, was carried out. The results indicated that pedogenic processes can be considered to be responsible for topographic smoothing and changes of the natural landscape. The main factor involved in this transformation process represents the upwards expansion of hydromorphic soil conditions from the topographic depressions developed in lower parts of the plateaus. This process includes internal transformations and degradations of the soil matrix leading to changes in soil structure, chemical composition and, diminishment of the original soil volume.