Unexpected nationwide nitrate declines in groundwater of Korea

Elevated levels of nitrate in groundwater are an important concern for health and the environment. The overapplication of nitrogen fertilizer to croplands is one of the major sources of high nitrate content in groundwater. In this study, we analyse the nitrate concentrations in Korean groundwater based on data from groundwater quality monitoring wells (n = 1,022–2,072), which were sampled twice annually over a recent 13‐year analysis period (2001–2013). We report that groundwater nitrate levels are decreasing, despite steadily increasing groundwater use. The maximum nitrate concentration decreased from 168.91 to 48.11 mg/L, whereas the mean values also show a gradual decreasing trend. Non‐parametric Mann–Kendall tests on nitrate concentrations also confirm the decreasing trend. The nitrate decrease is more clearly evident in agricultural groundwater as compared to domestic and drinking groundwaters. This decrease of nitrate in groundwater coincides with a large decline in nitrogen fertilizer application due to reduced cropland areas, more sustainable agricultural practices, and progressive improvement of sewage disposal services. This study proposes that the long‐term adoption of best practices in agriculture has had a positive impact on groundwater nitrate control.     

干旱胁迫下钠复合肥对霸王(Zygophyllum xanthoxylum)根系生长的促进作用

霸王(Zygophyllum xanthoxylum)是荒漠区广为分布的一种多浆旱生植物。采用盆栽育苗的方法,初步评价了干旱胁迫下Na+对霸王根系生长的贡献,探讨了一种新型钠复合肥对霸王根系形态、生理学指标的影响。结果显示,钠复合肥能显著促进霸王根系的生长并提高其抗旱性:(1)正常浇水时,钠复合肥对霸王的促进作用主要体现在株高的增加和侧根的增长上,根系活力显著增强;(2)自然干旱15d后,钠复合肥使得霸王根系活跃吸收面积显著提高24%,促进主根的加粗和伸长以吸收更多的水分和矿质养分;(3)干旱胁迫下,钠复合肥处理使霸王根部Na+浓度保持较高水平,K+浓度下降42%。因此认为,干旱前钠复合肥显著促进了霸王侧根的生长和根系活力的提高,干旱后钠复合肥通过促进根系活跃吸收面积的扩大和主根的生长以提高霸王的抗旱性,其主要原因是根和叶中积累了较多的Na+、而非K+。     

控释海水植物肥中氮、磷的测定

为评价控释肥的肥效，探讨、建立了相应的氮、磷测定方法。用硫酸作消解剂，消解液可以同时被用来测定氮、磷。钼锑抗坏血酸络合物作为显色剂，用紫外可见分光光度计测定磷的浓度；用改良式微量凯氏定氮蒸馏滴定法测定氮的含量。该方法灵敏、准确，易操作。用海水浸泡自制的控释海水植物肥样品(编号：MRF-0201．中速型)，运用建立的氮、磷测定方法测定浸取液中的氮、磷含量，实验证明该方法可以用于研究控释海水植物肥在海水中的氮、磷的化学动力学行为。     

实施“油盐(钾)兼探”是加速我国找钾工作的重要途径

从理论和实践阐述了油气和钾矿的共存关系和特点,指出在油气勘查中,实施“油盐（钾）兼探”,加强钾矿的综合找矿,是加速我国找钾工作的重要途径。     

富钾海绿石的新发现:钾肥资源的评价研究的新方向

我国是一个人口众多的发展中国家,农业是国民经济的基础,农用钾肥主要都来自天然矿物资源,特别是我国东中部人口密集的主要农业基地的大部分省份,富钾的矿产资源十分贫乏。过去几十年来把蒸发盐建造的钾盐作为钾资源研究主要目标,到目前为止进展不大。根据最新矿产资...     

Hurricane Katrina induced nutrient runoff from an agricultural area to coastal waters in Biscayne Bay,Florida

Water quality surveys conducted in Biscayne Bay, Florida, indicated enhanced nutrient input coupled with increased runoff as a result of precipitation associated with Hurricane Katrina. Nutrient concentrations before Katrina ranged from 0.06–24.2 μM (mean 3.3 μM) for nitrate and 0.01–0.18 μM (mean 0.1 μM) for soluble reactive phosphate. Five days after Katrina, nitrate concentrations ranged from 0.87–80.0 μM (mean 17.0 μM), with a bay-wide mean increase of 5.2-fold over pre-hurricane levels. Soluble reactive phosphate concentrations ranged from 0.07–0.62 μM (mean 0.2 μM), with a bay-wide mean increase of 2-fold over pre-hurricane levels. The maximum concentrations for both nitrate and soluble reactive phosphate were found at a water quality monitoring station near the mouth of Mowry Canal, which drains an agricultural area in the southern Biscayne Bay watershed near Homestead, Florida. At this station, nitrate and soluble reactive phosphate concentrations increased 7- and 10-fold, respectively. Storm-induced fertilizer runoff from this agricultural area caused a bay-wide increase in nutrient concentrations after Hurricane Katrina. Nutrient concentrations in the bay returned to pre-hurricane levels within three months after Hurricane Katrina, showing the resiliency of the Biscayne Bay ecosystem.     

Multivariate statistical analysis to identify the major factors governing groundwater quality in the coastal area of Kimje,South Korea

The main purpose of this study is to identify the major factors affecting groundwater quality by means of multivariate statistical analysis of the physico‐chemical compositions. Cluster analysis results show that the groundwater in the study area is classified into four groups (A, B, C and D), and factor analysis indicates that groundwater composition, 81·9% of the total variance of 17 variables, is mainly affected by three factors: seawater intrusion, microbial activity and chemical fertilizers. These results might be related to the geographical characteristics of the study area. The main influence on groundwater in groups B, C and D, which are close to the Yellow Sea and contain reclaimed areas, is the seawater intrusion by the present seawater, the trapped seawater, and microbial activity. Group A, however, has been used for agriculture for a long time, and thus groundwater in this group has been largely affected by chemical fertilizers. As groundwater flows from group A to group D according to its path, the governing factor of the groundwater quality gradually changes from chemical fertilizers to microbial activity and seawater intrusion. Copyright © 2004 John Wiley & Sons, Ltd.     

Toward a Synthesis: Lessons from Thirteen Cropland Watershed-Scale Studies

To integrate lessons from the U.S. Department of Agriculture (USDA), National Institute of Food and Agriculture–Conservation Effects Assessment Project (NIFA CEAP) program, key informant (KI) interviews were conducted in all 13 project areas. The purpose of these interviews was to supplement technical information about watersheds, their contaminants, modeling, economics, and key findings. We interviewed a wide range of people to develop a systematic look at individual project results, synthesize meanings, and derive principles useful in guiding future watershed management. Findings revealed common themes, which tended to align with KI categories, regardless of location. For instance, farmers and ranchers often understood water quality problems as well as federal and state personnel and university employees do. Conservation adoption by farmers was related to perceived need, cost, and convenience of the practice, as well as practice specifics and individual situations. Possible implications of these findings are advanced.     

沸石长效多元素复混肥的开发应用

试验证明,施用沸石长效多元素复混肥可以抗旱、提高产量、改善生态环境,为发展我省绿色农业、绿色无公害农产品将起到积极的、不可低估的促进作用,同时促进我省非金属矿产的开发和应用。     

国内难溶性钾矿资源及其开发利用

国内难溶性钾矿资源较丰富,可分为含钾岩石和含钾矿物两大类及若干亚类。含钾沉积岩有:富钾火山沉积凝灰岩(绿豆岩),含钾砂、页岩,含钾泥灰岩,含钾石膏泥,含钾磷块岩等;含钾岩浆岩有:霞石正长岩、霓辉石石英正长岩、流纹斑岩、正长斑岩、花岗伟晶岩、钾长粗面凝灰熔岩等;含钾变质岩有:钾长浅粒岩、云母片岩、钾长混合片麻岩等;可作钾矿资源的含钾矿物有:钾长石、明矾石、伊利石、白榴石、海绿石等。目前,绿豆岩,含钾砂、页岩,流纹岩,海绿石,白榴石等已可单独开采利用,制作钾肥;霞石正长岩、伊利石、钾长石、明矾石等可被综合回收利用;粗面岩、响岩、粗玄岩,含钾泥灰岩、钾长浅粒岩等尚待开发利用。