采用两级物化法去除黄磷废水中的氟化物

采用向含氟废水中加入适量石灰和聚合氯化铝，然后投加适量钙盐、磷酸和聚丙烯酰胺的二级处理工艺除氟，通过控制合适的pH、钙盐和磷酸的投加量、反应时间、反应温度、搅拌强度和絮凝剂的投加量，可使黄磷废水中氟的质量浓度降至5mg/L，氟的去除率达到99％以上，出水中氟的质量浓度达到GB8978－1996一级排放标准。     

Effects of Starch Moisture on Properties of Wheat Starch/Poly(Lactic Acid) Blend Containing Methylenediphenyl Diisocyanate

Methylenediphenyl diisocyanate was found to improve the interfacial interaction between poly(lactic acid)(PLA) and granular starch. The objective of this research was to study the effect of starch moisture content on the interfacial interaction of an equal-weight blend of wheat starch and PLA containing 0.5% methylenediphenyl diisocyanate by weight. Starch moisture (10% to 20%) had a negative effect on the interfacial binding between starch and PLA. The tensile strength and elongation of the blend both decreased as starch moisture content increased. At 20% moisture level, the starch granules embedded in the PLA matrix were observed to be swollen, resulting in poor strength properties and high water absorption by the blend.     

Use of Natural 35S to Trace Sulphate Cycling in Small Lakes,Flattops Wilderness Area,Colorado, U.S.A.

Measurements of the cosmogenically-produced ³⁵S, a radioisotope of sulphur (t_1/2 = 87 days), are reported for the Ned Wilson Lake watershed in Colorado. The watershed contains two small lakes and a flowing spring presumed to be representative of local ground water. The watershed is located in the Flattops Wilderness Area and the waters in the system have low alkalinity, making them sensitive to increases in acid and sulphate deposition. Time series of ³⁵S measurements were made during the summers of 1995 and 1996 (July–September) at all three sites. The system is dominated by melting snow and an initial concentration of 16–20 mBq L^-1 was estimated for snowmelt based on a series of snow samples collected in the Rocky Mountains. The two lakes had large initial ³⁵S concentrations in July, indicating that a large fraction of the lake water and sulphate was introduced by meltwater from that year's snowpack. In 1995 and 1996, ³⁵S concentrations decreased more rapidly than could be accounted for by decay, indicating that other processes were affecting ³⁵S concentrations. The most likely explanation is that exchange with sediments or the biota was removing ³⁵S from the lake and replacing it with older sulphate devoid of ³⁵S. In September of 1995 and 1996, ³⁵S concentrations increased, suggesting that atmospheric deposition is important in the sulphate flux of these lakes in late summer. Sulphur-35 concentrations in the spring water were highly variable but never higher than 3.6 mBq L^-1 and averaged 2 mBq L^-1. Using a simple mixing model, it was estimated that 75% of the spring water was derived from precipitation of previous years.     

PRECIPITATION CHANGES FROM 1956 TO 1996 ON THE WALNUT GULCH EXPERIMENTAL WATERSHED1

ABSTRACT: The climate of Southern Arizona is dominated by summer precipitation, which accounts for over 60 percent of the annual total. Summer and non‐summer precipitation data from the USDA‐ARS Walnut Gulch Experimental Watershed are analyzed to identify trends in precipitation characteristics from 1956 to 1996. During this period, annual precipitation increased. The annual precipitation increase can be attributed to an increase in precipitation during non‐summer months, and is paralleled by an increase in the proportion of annual precipitation contributed during non‐summer months. This finding is consistent with previously reported increases in non‐summer precipitation in the southwestern United States. Detailed event data were analyzed to provide insight into the characteristics of precipitation events during this time period. Precipitation event data were characterized based on the number of events, event precipitation amount, 30‐minute event intensity, and event duration. The trend in non‐summer precipitation appears to be a result of increased event frequency since the number of events increased during nonsummer months, although the average amount per event, average event intensity, and average event duration did not. During the summer “monsoon” season, the frequency of recorded precipitation events increased but the average precipitation amount per event decreased. Knowledge of precipitation trends and the characteristics of events that make up a precipitation time series is a critical first step in understanding and managing water resources in semiarid ecosystems.     

A GAME-THEORETIC APPROACH TO ACID RAIN ABATEMENT: CONFLICT ANALYSIS OF ENVIRONMENTAL LOAD ALLOCATION1

ABSTRACT: The detrimental impacts of acid rain have become widely publicized, but effective and equitable methods to mitigate the acid rain problem remain to be found. This paper focuses on conflicts involved in allocation of the total emission loads to be reduced to respective pollution sources of acid rain, and proposes a game-theory approach to the resolution of the conflict. With an example abstracted from a hypothetical case study in the United States of America and Canada, a systematic analysis is performed and policy implications of the results examined to assess the applicability of the proposed model.     

Agenda setting and acid precipitation in the United States

The objective of this research was to analyze the retention of acid precipitation as a viable policy issue on the Congressional agenda during the 1980s. Issue maintenance (a term borrowed from Barbara Nelson's discussion of the four stages associated with agenda decision making) was examined in relation to a set of issue characteristics originally developed by Roger Cobb and Charles Elder, i.e., concreteness, social significance, temporal relevance, complexity, and categorical precedence. Each issue attribute was found to be somewhat useful in explaining the longevity of acid rain as an agenda item although the direction of influence for two factors, complexity and temporal relevance, was contrary to expectations. It was suggested that a conceptual merger of this sort could contribute to the comparative analysis of agenda policy decisions by providing a clearer and more restricted set of decision points to be explained.     

PROBABLE MAXIMUM PRECIPITATION FOR THE LOWER RIO GRANDE1

To aid in planning and design of additional flood protection on the Lower Rio Grande, the Hydroraeteorological Branch prepared a probable maximum precipitation study for the International Boundary and Water Commission (United States and Mexico) and the Republic of Mexico. Five drainages from 2,000 to over 17,000 square miles in area between Falcon and Anzalduas Dams including Rio San Juan and Rio Alamo in Mexico are the areas of concern. The great rains of hurricane Beulah, September 19–24, 1967 verified that additional protection is needed. Procedures for estimating probable maximum precipitation (PMP) are described. A particular problem was to estimate rainfall potential for the Sierra Madre Oriental in Rio San Juan and Alamo drainages. These mountains form a north-south windward-facing slope and barrier of over 7000 feet in elevation. A detailed study was made of rains from hurricane Beulah. The storm produced the greatest known rain depths in North America for 50,000 square miles or greater, and durations longer than 48 hours.     

CLOUDS AND PRECIPITATION IN THE TEXAS HIGH PLAINS1

A study of the relationship among cloudiness, precipitable water vapor, stability and precipitation is presented for the Texas High Plains. A study of clouds during periods of above-normal rainfall indicates that precipitation during late fall and winter is associated with stratiform clouds which develop in conjunction with cyclonic activity. Spring and summer precipitation is most highly correlated with cumuliform clouds characteristic of convective activity. Investigation of other macroscale atmospheric features indicates that wet periods are further characterized by atmospheric instability and above-normal amounts of precipitable water vapor and water-vapor flux. Dry periods are associated with atmospheric circulation patterns which either serve to cut off the supply of low-level moisture, produce subsidence and consequent atmospheric stability, or both.     

石灰-聚铁法处理硫酸厂废水的研究

对各种处理硫酸厂废水的方法者了探讨,选择了以百石灰和聚合硫酸铁为药剂去除废水中砷,硫等污染物的方法。该法工艺简单,混凝剂投加量少,运行费用低,处理后的废水可达到排放标准。