Eneas Salati

Amazon Basin: A System in Equilibrium

Despite the very active deforestation of the last decade, the Amazon Basin is still primarily covered with trees and is a system in equilibrium. The Andes form a barrier at the western end of the basin and, coupled with the prevailing easterly winds, ensure an almost unique precipitation and water-recycling regime. On average 50 percent of the precipitation is recycled, and in some areas even more. The soils are poor. Most of the nitrogen and phosphorus is found in the soil, and the remaining nutrient elements are found in the standing biomass. There is some nutrient recycling and little loss from the intact ecosystem, and the small input of nutrients from precipitation maintains a small positive nutrient balance. Continued large-scale deforestation is likely to lead to increased erosion and water runoff with initial flooding in the lower Amazon, together with reduced evapotranspiration and ultimately reduced precipitation. Reduced precipitation in the Amazon could increase the tendency toward continentality and adversely affect climate and the present agriculture in south-central Brazil.

Storage and Remobilization of Suspended Sediment in the Lower Amazon River of Brazil

In the lower Amazon River, suspended sediment is stored during rising stages of the river and resuspended during falling river stages. The storage and resuspension in the reach are related to the mean slope of the flood wave on the river surface; this slope is smaller during rising river stages than during falling stages. The pattern of storage and resuspension damps out the extreme values of high and low sediment discharge and tends to keep them near the mean value between 3.0 x 106 and 3.5 x 106 metric tons per day. Mean annual discharge of suspended sediment in the lower Amazon is between 1.1 x 109 and 1.3 x 109 metric tons per year.

Organic Carbon-14 in the Amazon River System

Coarse and fine suspended particulate organic materials and dissolved humic and fulvic acids transported by the Amazon River all contain bomb-produced carbon-14, indicating relatively rapid turnover of the parent carbon pools. However, the carbon-14 contents of these coexisting carbon forms are measurably different and may reflect varying degrees of retention by soils in the drainage basin.

Confirmation of nitrogen fixation in two tropical grasses by 15N2 incorporation

Intact soil cores containing plants of Paspalum notatum or Digitaria decumbens were selected with the acetylene reduction method, and then exposed to 15N15 to confirm nitrogen fixation in tropical grass-bacteria associations. In a preliminary experiment with P. notatum15N2 incorporation was slow but progressive during 24 h in roots but translocation to rhizomes and leaves ceased after 17h. With improved assay chambers, enrichments of 0.151 and 0.563 15N atom % excess were obtained in roots of D. decumbens cv transvala and P. notatum systems respectively, after 3 days. Enrichments in rhizomes were similar to those of roots; however in the leaves only 8% of root enrichment was observed. The addition of sucrose to the soil doubled N2-fixation in roots in both grass species studied, but did not result in increased incorporation into the leaves of P. notatum.

Climatology of the Amazon region

During the many colonization cycles in the Amazon, serious difficulties hampered the development of intensive agricultural activity which would lead to expansion and the economic independence of its populations. Many investigators have tried to explain the reasons for such difficulties and frequently associate environmental factors with agricultural production problems.

PRECIPITATION IN THE CENTRAL AMAZON BASIN: - THE ISOTOPIC COMPOSITION OF RAIN AND ATMOSPHERIC MOISTURE AT BELÉM AND MANAUS

In order to improve the understanding of the water in the Amazon Basin, samples of rain and moisture were collected daily at Belem and Manaus from August 78 to January 80. All isotope data are presented. The most depleted values, sometimes lower than — 10‰ in δ18O at Belem or Manaus, were encountered during the rainy season (January-April). Possible causes of the seasonal differences in tne isotope pattern are discussed.

Temas ambientais relevantes

NESTE trabalho, sao indicados os principais temas ambientais para o Brasil, num futuro proximo (2022). Impactos do aumento da temperatura sao estudados atraves de cenarios, que podem modificar o balanco hidrico em algumas regioes, tendo sido observado um aumento da ordem de 0,78oC no periodo de 1917 a 2003, na regiao de Piracicaba. Para a regiao amazonica, foi observado um aumento de 0,56oC durante o seculo XX. Tanto o desmatamento quanto as Mudancas Climaticas Globais atuam na direcao de um aumento da temperatura, enquanto o desmatamento influi na direcao de uma diminuicao das precipitacoes. O desmatamento provoca, ainda, uma grande perda de biodiversidade, sendo estimadas em uma perda entre 8.000 ate 34.000 especies, considerando-se que o desmatamento aumenta em 1% ao ano.

Balanço hídrico de pequena bacia hidrográfica em floresta amazônica de terra firme

It was evaluated the annual transpiration, evapotranspiration and runoff rates from a 1.3 km2 watershed, located at Ducke Reserve, which is 26 km far from Manaus. The results showed that, from the total rainfall about 62% were transpired, 80.7% evapotranspired, and 19.3% runoff.

Unusual Isotopic Composition of Carbonates from the Irati Formation, Brazil

Samples of dolomite and limestone from the Permian Irati Formation collected in the Parana Basin, southern Brazil, have been analyzed for δC13 and δO18. The δC13 ranges from +18.3‰ to −17.4‰ PDB, while the δO18 ranges from −2.6‰ to −12.5‰ PDB. In some quarries where the exposures are especially good, a large variation in δC13 can be found. The lower, dense gray dolomite has light carbon (−17 to +2.6‰), whereas the overlying intermediate zone of interbedded organic-rich shale and black dolomite has dolomite containing heavy carbon (+4.8 to +14.9‰PDB). We believe that the dolomite represents diagenetically altered limestone, and that light CO2 produced by decomposing organic matter was involved in the diagenesis of the lower units, while heavy CO2 produced by the isotopic exchange between CO2 and methane was involved in the alteration of the upper, organic-rich layers. The original environment of deposition may be represented by the few limestone outcrops from the southern part of the basin, which have somewhat light (−2.6 to −7.6‰) carbon and light (−6.7 to −11.1‰) oxygen that may be the result of precipitation in a lake or inland sea.

Wetland projects developed in Brazil

The first studies with constructed wetlands undertaken in Brazil were the result of observations made from the Amazon flood plains. The first attempt to use this capacity to change the quality of the water, in the sense of purification performed in Brazil using constructed wetland systems, was made by Salati et al. (1982) After that, new technologies were developed in a focused attempt to increase the efficiency of the system and reduce investments. Over these 18 years, persuading the Brazilian scientific community as well as the environmental control agencies to give due attention to this kind of research has required endless efforts. Only in recent years have major institutions responsible for sewage treatment and potable water supply been concerned with this type of technology for solving real problems. These institutions are as follows: SABESP (Basic Sanitation Company of Sao Paulo State), SANEPAR (Sanitation Company of Parana State) and CESP (Electric Company of Sao Paulo State). One of the private institutions that has systematically worked in the design and projects of constructed wetlands is the Institute of Applied Ecology. This institution has enhanced and developed a water depuration system based on the purifying capacity of the soil. The wetlands with filtering soils are systems formed by overlapping layers of crushed stone, gravel and soil planted with rice. This technology has been used in sewage treatment and also in water supply systems.