略论宋代海盐生产的技术进步——兼考《熬波图》的作者、时代与前身

从海水中制取食盐,属于我国最古老的手工业之一。古人称之为“煮海”、“煮水”或“熬波”。制取海盐,是一项综合性的工业技术。它包括气象观测、潮汛监察、海岸水利工程、耕垦田土、冶铁铸造、化学工艺等诸多劳作。中唐以后,特别是五代与两宋时期,我国海岸盐民在总结前人经验的基础上,根据当地水土特征,形成了几种颇为有效的取卤、验卤方法和一整套煮盐工序。

海水灌溉农田

目前,科学家们正在探索直接采用海水灌溉农作物的方法:一方面寻找既可用海水灌溉,又可作为粮食的天然作物;另一方面是利用咸土生长的盐生植物基因,改良现有的甜土粮食作物的品种,使之能适应海水浸泡的生态环境 美国亚利桑那大学的研究人员坚持10多年的野外考察研究”,从沿海地区的1000多种靠海水浇灌生长的天然植物中,挑选出一种学名叫SOS—7的品种。这种原生的海洋植物广泛分布在海滨湿地,其形状似海草,其生产速度快,根底牢,既不怕海水浸泡,又经得起海浪冲击。尽管SOS—7不像海带那样可供人直接食用。

Research on the Critical Conditions for Clay Particle Release During Saline Aquifer Freshening Process

Water sensitivity phenomenon occurs during saline aquifer freshening process in seawater intrusion area, and clay particles released in the phenomenon can damage the infiltration capacity of the aquifer. In order to find out the factors and mechanisms for clay particle release, laboratory column infiltration experiments simulating saline aquifer freshening process were designed to measure the critical conditions(critical flow velocity, critical salt concentration and critical ionic strength) and force analysis for clay particle according to DLVO electric double layer theory was employed to illustrate the mechanisms for particle release. The research results showed that critical flow velocity for clay particle release is influenced by salt concentration of injecting solution. When salt concentration of injecting solution is very high, clay particles are not released, indicating that there does not exist a critical flow velocity in this situation. As salt concentration of injecting solution decreases, particles start to be released. The critical salt concentration for clay particle release is 0.052 mol L-1 in our work, which was determined by a constant-flux experiment for stepwise displacement of high concentration Na Cl solution. The critical ionic strength for clay particle release decreases as Ca2+ molar content percentage of the mixed solution of Na Cl and Ca Cl2 increases following the first-order exponential decay equation y = 0.0391e-0.266 x + 0.0015.

Effect of Saline Water on Cadmium Uptake and Remediability of Soil with Brassica Napus

Phytoremediation is a new technique for cleaning contaminated soils. This method in comparison with the other techniques is very simple and low cost. Among the pollutants, heavy metals and specially cadmium （Cd） is very important because of its high movement in soil and high toxicity. Bioavailability of metals in the soil is affected by various factors including saline solution. In fact there are symptoms for increasing Cd uptake due to increasing C1＂1 concentration in soil solution. The objective of this study was to investigate the effect of saline irrigation water on cadmium uptake and remediability of soil with Brassica napus （rapeseed） in greenhouse experiment. Saline waters of 0, 1.5 and 2.5 dS/m was applied on soil with different concentrations of Cd （5, 10, 20, 30 and 50 ppm） during the cultivation period of Okapi （fall rapeseed variety）. The results of this study showed that there are no significant differences in shoot dry matter exposed to Cd, but root dry matter decreased with increasing Cd concentration （p〈5%）. Salinity had a significant effect （p〈l%） on Cd concentration in roots and increased from 26.83 （in control） to 36.46 mg.kg-1 dry wt （in 2.5 dS.m＂l treatment）. The significant effect （p〈5%） was found in shoots as well and the Cd uptake was increased from 2.14 to 3.25 mg.m^-1dry wt in control and 2.5 dS＇m^-1 treatments respectively. Likewise, salinity increased bioaccumulation coefficient, whereas had no significant effect on transport factor. The obtained results showed that Cd metal tend to accumulate more in the roots ofBrassica napus than in the shoots.

Effect of Combined Use of Brackish Water and Nitrogen Fertilizer on Biomass and Sugar Yield of Sweet Sorghum

Soil salinization and non-point source pollution are among the most important and widespread environmental problems in European Mediterranean regions. Sweet sorghum （Sorghum bicolor （L.） Moench var. saccharatum） is a moderate to high salinity tolerant crop with low water and nutrient needs, seen as an alternative to grow in the water scarce regions. A three-year multifactorial study was conducted in southern Portugal to evaluate the combined effects of saline water and nitrogen application on the dry biomass （total, stems, and leaves）, sugar content （total reducing sugars and sucrose eontents） and sugar yield （here defined as the product of total reducing sugars and stems dry biomass） functions of sweet sorghum. Sorghum dry biomass and sugar yield showed diminishing returns for each incremental change of nitrogen. The use of saline irrigation waters also led to yield reduction. Exception was sucrose content which increased with increasing levels of sodium in the soil. Nitrogen need decreased as the amount of sodium applied increased. Stem dry biomass, sucrose content, and sugar yield progressively increased with progress in the experiment. The effect could be attributed to the increase of the amount of irrigation applied throughout the years, thus increasing the leaching fraction which promoted salt leaching from the root zone, reduced the salinity stress, increased plant transpiration, nitrogen uptake and biomass yield.

Soil Erosion as Affected by Polyacrylamide Application Under Simulated Furrow Irrigation with Saline Water

The reduction of soil and water losses under furrow irrigation with saline water is important to environmental protection and agricultural production. The objective of this study was to determine the effect of polyacrylamide (PAM) application on soil infiltration and erosion under simulated furrow irrigation with saline water. Polyacrylamide was applied by dissolving it in irrigation water at the rates of 1.5, 7.5, and 15.0 mg L-1 or spreading it as a powder on soil surface at the rates of 0.3, 1.5, 3.0, and 6.0 g m-2, respectively. The electrolyte concentration of tested irrigation water was 10 and 30 mmolc L-1 and its sodium adsorption ratio (SAR) was 0.5, 10.0, and 20.0 (mmolc L-1)0.5. Distilled water was used as a control for irrigation water quality. Results indicated that the electrolyte concentration and SAR generally did not significantly affect soil and water losses after PAM application. Infiltration rate and total infiltration volume decreased with the increase of PAM application rate. Polyacrylamide application in both methods significantly reduced soil erosion, but PAM application rate did not significantly affect it. The solution PAM application was more effective in controlling soil erosion than the powdered PAM application, but the former exerted a greater adverse influence on soil infiltration than the latter. Under the same total amounts, the powdered PAM application resulted in a 38.2%-139.6% greater infiltration volume but a soil mass loss of 1.3-3.4 times greater than the solution PAM application.

Soil Properties and Wheat Growth and Nutrients as Affected by Compost Amendment Under Saline Water Irrigation

A greenhouse experiment was conducted to test and compare the suitability of saline compost and saline irrigation water for nutrient status amendment of a slightly productive sandy clay loam soil, to study the macronutrient utilization and dry matter production of wheat （Triticum aestivum c.v. Gemmiza 7） grown in a modified soil environment and to determine the effects of compost and saline irrigation water on soil productivity. The sandy clay loam soil was treated with compost of five rates （0, 24, 36, 48, and 60 m3 ha-1, equivalent to 0, 3, 4.5, and 6 g kg-1 soil, respectively） and irrigation water of four salinity levels （0.50 （tap water）, 4.9, 6.3, and 8.7 dS m-l）. The results indicated that at harvest, the electrical conductivity （EC） of the soil was significantly （P 〈 0.05） changed by the compost application as compared to the control. In general, the soil salinity significantly increased with increasing application rates of compost. Soluble salts, K, C1, HCO3, Na, Ca, and Mg, were significantly increased by the compost treatment. Soil sodium adsorption ratio （SAR） was significantly affected by the salinity levels of the irrigation water, and showed a slight response to the compost application. The soil organic carbon content was also significantly （P 〈 0.05） affected by application of compost, with a maximum value of 31.03 g kg-1 recorded at the compost rate of 60 m3 ha-1 and the irrigation water salinity level of 8.7 dS m-1 and a minimum value of 12.05 g kg-1 observed in the control. The compost application produced remarkable increases in wheat shoot dry matter production. The maximum dry matter production （75.11 g pot-1） occurred with 60 ma ha-1 compost and normal irrigation water, with a minimum of 19.83 g pot-1 with no addition of compost and irrigation water at a salinity level of 8.70 dS m-1. Significant increases in wheat shoot contents of K, N, P, Na, and C1 were observed with addition of compost. The relatively high shoot N values may be attributed to increases in N availability in the tested soil caused by the compost application. Similarly, significant increases in the shoot contents of Na and C1 may be ascribed to the increase in soil soluble K and Cl. The increases in shoot P, N, and K contributed to the growth stimulation since P supplied by the compost was probably responsible in saline and alkaline soils where P solubility was very low.