Forest management and biomass in the U.S.A.

There are a variety of opportunities to change land and forest management and, at the same time, create a positive impact on the current use of fossil energy. To the extent that these opportunities can be captured, they address the root cause of greenhouse warming-fossil fuel emissions-while, at the same time, improving economic opportunities, ecosystem productivity, and environmental conditions over broad areas. The need for better markets to absorb biomass energy, plus research to make biomass conversion more efficient, is probably the most important deterrent to achieving these possibilities.     

Soil-geomorphology relations in mountains of Oregon,U.S.A.

The development and distribution of soils in the Coast Range and Klamath Mountains are related to geomorphic surfaces and slope gradients. Soils over basalt, studied in the Coast Range, were formed in transported materials and include examples of more than a half dozen great groups of the Alfisol, Inceptisol, Mollisol, and Ultisol orders. Distribution patterns of the soils can be related to active slopes, metastable slopes, pediments, ridge tops, flood plains, and alluvial fans. Variables among the factors of soil formation in the Coast Range are chiefly geomorphic surfaces and parent materials.Soils of a lithosequence of pyroclastics, granite and schist in the Klamath Mountains include examples of great groups in the Entisol, Inceptisol, and Mollisol orders. All soils from pyroclastics have argillic horizons, those from granite lack argillic horizons, and those from schist lack argillic horizons except on relatively stable surfaces. Average thicknesses of soils over saprolite range from 76 cm over granite and schist to 150 cm over pyroclastics.Lithologic discontinuities are common in both mountain areas. Field techniques for identification, described briefly, include stone lines, irregular distribution of rock fragments with depth, thicknesses of weathering rinds on rock fragments, and the lateral extensions of soil horizons.     

美国非点污染源及其治理对策

本文扼要介绍了美国非点源污染现状,指出农业是最大的非点污染源,并导致地表水、地下水污染和水质下降;美国环保局和农业部治理非点污染源的对策。持续农业正受到美国朝野的关注。实践表明,持续农业是一种经济上可行、对环境无损害的农业     

Modeling Cl concentration in Cayuga Lake,U.S.A.

The annual average concentration of Cl in Cayuga Lake, NY, has decreased from a value of approximately 102 mg L^?1 in 1970, when the discharge of NaCl fines from an adjoining rock salt mine was discontinued, to a concentration of approximately 46 mg L^?1 in 1988. A complete-mixed model for Cl concentration accurately simulated this decrease in concentration, establishing that the decrease was the result of an abrupt reduction in loading. The time course of the decrease strongly supports the position that the high Cl concentrations that prevailed in the lake in the late 1960's were largely a result of the discharge from the mining facility, and not due to the input of enriched groundwater as previously hypothesized. The predicted steady-state Cl concentration associated with the complete flushing of the mining facility input, expected in about the year 2000, is approximately 32 mg L^?1. Further, the model analysis supports previous speculation that the major source of material loading to the lake, the Seneca River, ‘short-circuits’ to the outlet; i.e., this tributary should not be included in material budgets for the lake.     

Density stratification in ionically enriched Onondaga lake,U.S.A.

Denstity stratification was characterized in ionically enriched Onondaga Lake for a 7 mo period of 1980, based on paired profiles of temperature and cloride collected at 1 m depth intervals from a single deep water location on 54 different occasions. The lake was both thermally and chemically stratified. The chemical component represented 38.5% of the density stratification for the study period. It was most often the dominant component in establishing the depth of the upper mixed layer, which was unusually shallow in the lake. Further, the presense of the chemical component prolonged the stratification period. The chemical component of stratification decreased progressively through the study. The altered stratification characteristics of the lake may have negative effects on the level of biomass in the upper waters and the oxygen resources of the lower waters.     

Changes in water content in and under frozen soil in Iowa,U.S.A.

Water contents were measured in a soil profile during the winter from the time of harvest until soil temperatures were greater than 0°C through this profile in the spring. Water movement between successive layers was predicted using the Darcy flow law and changes in water flux. These values were then compared with the changes in soil water content observed in field measurements. Results showed that water content changes (accumulation or loss) below the frozen layer were greater than predicted but that the differences between predicted and measured contents were small, much smaller than the amounts reported in previous experiments.     

Sediment Quality in Burlington Harbor,Lake Champlain,U.S.A.

Surface samples and cores were collected in 1993 fromthe Burlington Harbor region of Lake Champlain. Sediment samples were analyzed for trace metals(cadmium, copper, lead, nickel, silver and zinc),simultaneously extracted metal/acid volatile sulfide(SEM-AVS), grain size, nutrients (carbon and nitrogen)and organic contaminants (polycyclic aromatichydrocarbons (PAHs) and polychlorinated biphenyls(PCBs)). The concentrations of cadmium, copper,silver and zinc from the partial sediment digestion ofthe surface samples correlated well with each other(r ²>0.60) indicating that either a commonprocess, or group of processes determined the sedimentconcentrations of these metals. In an analysis of thespatial distribution of the trace metals and PAHs,high surficial concentrations were present in thesouthern portion of the Harbor. The trace metal trendwas strengthened when the concentrations werenormalized by grain size. A sewage treatment plantoutfall discharge was present in the southeasternportion of the Harbor at the time of this study and isthe major source of trace metal and PAH contamination. Evaluation of sediment cores provides a proxy recordof historical trace metal and organic inputs. Thepeak accumulation rate for copper, cadmium, lead, andzinc was in the late 1960s and the peak silveraccumulation rate was later. The greatestaccumulation of trace metals occurred in the late1960s after discharges from the STP began. Subsequentdeclines in trace metal concentrations may beattributed to increased water and air regulations. The potential toxicity of trace metals and organiccontaminants was predicted by comparing contaminantconcentrations to benchmark concentrations andpotential trace metal bioavailability was predictedwith SEM-AVS results. Surface sample results indicate lead,silver, ΣPAHs and ΣPCBs are potentially toxicand/or bioavailable. These predictions were supportedby studies of biota in the Burlington Harborwatershed. There is a clear trend of decreasing PAHand trace metal contaminant concentrations withdistance from the STP outfall.     

A review of bromine determination in foods.

Organic compounds containing bromine, including methyl bromide, ethylene dibromide, and 1,2-dibromo-3-chloropropane, have been used extensively for the fumigation of foods, or soils in which foods grow, making it necessary to determine residues of bromine and bromine-containing organic compounds. A large number of methods for the determination of bromine in foods, as organic, inorganic, and combined total bromide, have been developed. In methods for organic bromide, the bromine is converted to the inorganic form for measurement by titration, photometry, or other means. In recent years, instrumental methods have been developed in which the total bromine in the sample is determined, regardless of the state in which it exists. X-ray fluorescence and neutron activation analysis are the 2 instrumental methods used most widely. Residue data are presented for some typical bromine-containing samples.