水气环境变化对混凝土中钢筋宏电池腐蚀的影响

基于宏电池腐蚀理论,将阴极钢筋和阳极钢筋分别浇筑在两个独立的混凝土试块中,用导线的连接或断开来模拟宏电池腐蚀或微电池腐蚀,通过往混凝土试块的预留孔中加水或将混凝土试块完全浸入水中来改变混凝土的水气环境,通过分析宏电池电位差、宏电池极化比率、宏电池电流密度和微电池电流密度,研究不同水气环境对混凝土中阴、阳极钢筋宏电池腐蚀行为的影响。结果表明:在阴极和阳极钢筋面积比为1的情况下,阴极钢筋和阳极钢筋周围混凝土的水气环境变化,对宏电池腐蚀电流、宏电池腐蚀极化比率及控制模式影响显著。当阴极或阳极钢筋周围的混凝土,由气中环境转为浸水环境后,宏电池腐蚀电流密度和微电池腐蚀电流密度的比率显著降低,且阴极钢筋周围混凝土的浸水状态要比阳极钢筋周围混凝土的浸水状态,更能有效地抑制宏电池腐蚀。当阴极钢筋和阳极钢筋周围的混凝土都完全浸入水中后,可最大限度地降低宏电池腐蚀速率,此时宏电池腐蚀的控制模式为典型的阴极控制。

Effect of Water Resources Allocation on Groundwater Environment and Soil Salinity Accumulation under Climate Change

The combined surface and groundwater allocation practice by wells and canals had contributed to the safety of groundwater environment and agriculture sustainable production. The typical area in the People＇s Victory Canal irrigation district was taken as a case, drawing together the irrigation district agriculture water consumption and precipitation from 1954 to 2014 in the People＇s Victory Canal irrigation district, ratios of surface to groundwater irrigation amount, dynamic of groundwater depth and hydrochemical characteristic of groundwater from 2008 to 2014 in the research area, the relationship between groundwater depth and ratio of surface to groundwater irrigation amount was analyzed, in order to ascertain the influence of precipitation on ratios of surface to groundwater irrigation amount and its effect on soil and groundwater environment. The results indicated that positive correlation between the ratios of surface to groundwater irrigation amount and annual precipitation was appeared, affected by climate change, average irrigation amount from surface in the recent 5 years was 2.90 x 108 cubic meters, accounted for 75.52% of total irrigation amount, on the other hand, decreasing tendency of precipitation was obvious, and groundwater depth dynamic in upstream of the branch canals was more dramatic than downstream because of surface water irrigation infiltration, under the unified condition of water use efficiency, ratio of surface to groundwater irrigation amount was negative correlation with area of the groundwater depth beyond 11 m, meanwhile, groundwater depth demonstrated negative correlation with the ratio of surface to groundwater irrigation amount, moreover, alkaline trend of groundwater hydrochemistry during the normal season in the research area was obvious because of phreatic evaporation and the agricultural irrigation from wells, along with irrigation from surface inflow of Yellow River, quality of groundwater hydrochemistry during the dry season was ameliorative greatly. Consequently, it was very important to the agriculture sustainable production that well-canal combined irrigation patterns alleviated extremely alkaline trend of the groundwater hydrochemistry and played a positive role of root layer soil salinity leaching.

The Microclimatic Influence of a Water Body on an Urban Environment

The paper aims to investigate the potential of a water body to influence in lowering the warmth in the city of Sao Jose do Rio Preto, Brazil, due to the evaporative cooling effects. In order to verify its potential, three collecting points of temperature and humidity were placed in an urban area close to the municipal dam. The first one was placed on the dam margin, the second one, 50 m distant of the margin and, the third one, 100 m distant. The data were taken during December 2010 and then compared to the climate data of the Climate Station of CIIAGRO-Integrated Center of Agro Meteorological. The results show that the closer the collection point is to the water body, and the lower is the temperature variation. The humidity taxes verified at the closest point to the water body indicate values higher than those ones collected at the most distant point. The insertion of moisture through the water bodies in an urban environment demonstrated to be a strategy that improved the thermal conditions and has to be considered for urban planners to establish strategies of urban occupation.

Calibration of the U37K index of long-chain alkenones with the in-situ water temperature in Lake Qinghai in the Tibetan Plateau

Long-chain alkenones (LCAs) can potentially be used as indicators to understand past variations in lacustrine environments.Previous research has suggested that the relationship between the temperature and the unsaturation index of LCAs should be calibrated individually,because of the possible variations in the alkenone-producing algal species in the lacustrine environment.In this work,we have calibrated U37K' of water filter samples against the in-situ water temperature in Lake Qinghai,Tibetan Plateau.There are significant relationships between U37K' and the water temperature,a non-linear relationship was derived.Because the U37K' values did not respond sensitively at lower temperatures,we suggested that a quadratic regression (U37K' =0.0011×T2-0.0201×T+0.1959,n=15,r2=0.74) was appropriate than linear regression to represent the relationship between the in-situ temperatures and U37K'.Meanwhile,the U37K correlation relationship was not more significant than U37K' index in our study.Because of the C37:4 effects by salinity change,we suggest U37K is not as robust as the U37K' index as a temperature proxy,at least for the salt lake in the Tibetan Plateau.The calibration of the U37K' index in this work has provided a new understanding of historic climatic changes in the Tibetan Plateau.