Nutrient dynamics in an alpine headwater stream: use of continuous water quality sensors to examine responses to wildfire and precipitation events

Stream water quality can change substantively during diurnal cycles, discrete flow events, and seasonal time scales. In this study, we assessed event responses in surface water nutrient concentrations and biogeochemical parameters through the deployment of continuous water quality sensors from March to October 2011 in the East Fork Jemez River, located in northern New Mexico, USA. Events included two pre‐fire non‐monsoonal precipitation events in April, four post‐fire precipitation events in August and September (associated with monsoonal thunderstorms), and two post‐fire non‐monsoonal precipitation events in October. The six post‐fire events occurred after the Las Conchas wildfire burned a significant portion of the contributing watershed (36%) beginning in June 2011. Surface water nitrate (NO₃? N) concentrations increased by an average of 50% after pre‐fire and post‐fire non‐monsoonal precipitation events and were associated with small increases in turbidity (up to 15 NTU). Beginning 1 month after the start of the large regional wildfire, monsoonal precipitation events resulted in large multi‐day increases in dissolved NO₃? N (6 × background levels), dissolved phosphate (100 × background levels), specific conductance (5 × background levels), and turbidity (>100 × background levels). These periods also corresponded with substantial sags in dissolved oxygen (<4 mg l^?1) and pH (<6.5). The short duration and rapid rates of change during many of these flow events, particularly following wildfire, highlight the importance of continuous water quality monitoring to quantify the timing and magnitude of event responses in streams and to examine large water quality excursions linked to catchment disturbance. Copyright © 2015 John Wiley & Sons, Ltd.     

盖层与源岩的时空配置关系对油气运聚成藏的控制作用

盖层与源岩是油气成藏不可缺少的两个条件，它们在时空上的配置关系对油气运聚成藏起着重要的控制作用，盖层的空间分布面积只有大于源岩的空间分布面积时，盖层才能封闭住源岩排出的大量油气，尤其覆盖整个盆地或凹陷时效果更好；否则造成油气大量散失，不利于油气的大量聚集与保存，盖层封闭能力形成期只有早于或与其相当时，才能封闭住源岩排出的大量油气，有利于油气的大规模聚集成藏，反之，盖层所能封闭住油气量的大小主要取决于两者之间时间差的相对大小，两者时间差越大，盖层所能封闭住油气量的大小主要取决于两者之间时间差的相对大小，两者时间差越大，盖层所能封闭住源岩排出的油气量相对越小，不利于油气的大相对大小，两者时间差越大，盖层所能封闭住源岩排出的油气量相对越小，不利于油气的大规模聚集成藏；反之，盖层所能封闭住源岩排出的不同气量相对越大，越有利于油气的大规模聚集成藏。     

西藏不同退化高寒草地土壤酶的活性

对退化高寒草原土壤酶活性研究的结果表明:1)相对于正常草地,轻度退化草地土壤纤维素酶、脲酶、碱性磷酸酶活性均呈不同程度的提高;中度退化草地土壤纤维素酶、碱性磷酸酶活性亦呈同一趋势,仅土壤脲酶活性显著降低;严重退化草地中3种土壤酶活性则均呈显著降低。2)不同土壤酶活性对土壤环境变化的敏感性总体呈碱性磷酸酶活性>脲酶活性>纤维素酶活性;土壤酶活性大小则均呈脲酶活性>碱性磷酸酶活性>纤维素酶活性。3)不同土壤酶活性与土壤有机碳均呈极显著正相关(r值为0.728 8~0.980 8,p≤0.01),与土壤全氮、有效氮、有效钾亦呈不同程度的正相关,与土壤有效磷含量则均呈显著或极显著负相关;土壤pH对土壤脲酶活性具有显著影响,对纤维素酶、碱性磷酸酶活性的影响则不甚明显。4)西藏高原高寒、干旱条件下,中度,特别是轻度退化草地一定程度的沙化所导致的土壤通透性能的显著改善对提高土壤酶活性,进而促进土壤有机残体的分解和有机质的形成具有重要作用。5)土壤酶活性不仅可以反映不同程度退化高寒草原土壤肥力水平的差异,同时亦可作为评价草地土壤肥力的一个基本指标。     

海南岛新村湾营养负荷对海菖蒲的影响研究

对海南岛新村湾海草床的优势种——海菖蒲(Enhalus acoroides)的茎枝特征、茎枝密度、生物量和不同组织营养素含量进行了研究,并探讨了海水和沉积物间隙水营养负荷对其的影响。结果表明,(1)海菖蒲的茎枝特征(叶长、宽和枝重)、茎枝密度和地上生物量存在显著的空间差异,这些因子与海水和沉积物间隙水DIN含量呈负相关;(2)海菖蒲TN、TP质量分数随着样区的变化而产生显著差异,海菖蒲TN质量分数与其所在样区海水和沉积物间隙水DIN浓度呈显著正相关;(3)随着水体N负荷的增加,海菖蒲叶单位面积附着藻类生物量显著增加。本次研究的结果表明,网箱养殖引起的营养负荷是导致海草衰亡的潜在原因之一,引起了新村湾网箱养殖区海草床的退化。     

Drought and deluge: Influence of environmental factors on water quality of kettle holes in two subsequent years with different precipitation

Thirty kettle hole ponds located in agricultural landscape of western Poland were studied with respect to physico-chemical (temperature and pH) and chemical (SC, dissolved oxygen, concentration of nutrients) variables of surface water quality during two subsequent years. Most of the ponds selected for the study host populations of endangered large branchiopod crustaceans, thus the aim of the study was to find out the rules governing these ecosystems and infer the best ways to protect them. Precipitation during the first year of the study was close to the average for the region, whereas severe drought was recorded during the second year. The influence of water regime, morphological parameters, catchment characteristics and vegetation on the parameters of water (pH, conductivity, contents of O₂, N-NH₄, N-NO₂, N-NO₃, SRP and TP) separately for both years was tested using redundancy analyses (RDA). The results showed that the factors significantly explaining the variance in water chemistry differed between years of the study. In the year of average precipitation, the most important factors were related to the morphology of the pond and its catchment. In contrast, under drought conditions the factors connected with pond vegetation and water depth were significant. However, in general, hydroperiod length of the pond was the most important factor, significant in all the models created.     

用成岩模型计算沉积物-水界面营养盐的交换通量--以渤海为例

根据沉积物中营养盐的再生对水体中营养盐的收支循环动力学的作用.利用1998年秋季和1999年春季沉积物间隙水中营养盐的分析结果,建立了沉积物中营养盐的成岩模型,并由此计算了沉积物-水界面营养盐的交换通量.结果表明,硝化速率、反硝化速率、有机氮含量、硅质成分的溶解速率、生物扰动作用、孔隙率明显影响沉积物间隙水中营养盐的分布和沉积物-水界面的交换通量.对比了实验室培养法和扩散通量计算法测得沉积物-水界面营养盐的交换通量,表明2种方法所得NO3通量较一致,但NH4 ,PO43-,SiO32- 2种方法所得通量有一定差异,文中讨论了可能的原因.以渤海为例阐明了在用扩散通量法研究沉积物-水界面营养盐的交换通量时,表层沉积物分割厚度对界面交换通量影响显著,为了得到合理的与现场接近的结果表层沉积物的分割厚度以不超过1em为宜.     

长江口区浮游植物营养限制因子的研究 1. 秋季的营养限制情况

1998年11月在长江口及周围海域进行了一个航次的环境调查,并在室内以中肋骨条藻为实验藻种,应用营养加富生物测定法对本海域浮游植物的营养需求状况进行了研究．结果表明,可大致根据离河口的远近将此海域分为3个部分：近河口光限制区、过渡带光和磷酸盐限制区、远河口氮盐限制区．P与N分别为潜在营养限制因子的界线大致沿盐度为31的盐线．并指出,以溶解无机氮磷比的判断标准,在悬浮物浓度较高的区域会高估磷的限制作用．     

西藏拉果错卤虫：2营养成分

卤虫包括成体,无节幼体和卤虫卵,蛋白质,氨基酸,脂肪酶等营养成分的含量是评价卤虫质量的主要标准,因为摄食动物饵粒效果取决于氨基酸,脂肪酸的组成与含量,西藏拉果错卤虫的营养成分含量较高,１９９６、１９９７年盐湖研究中心连续取样测定,其蛋白质含量成本接近２０％,无节幼体约５５％,脱壳卵近５０％;粗脂肪成体３％,无节幼 和脱壳超过８７％,三种高级不饱和脂肪酸（２０：３,２０：４,２０：５）ＨＵＦＡ含量。     

浙江嘉善土壤地球化学背景及生态质量评价

通过嘉善全县域4点／km^2密度的表层土壤调查采样调查,取得土壤地球化学元素含量背景值,并依据相关标准进行土壤养分质量和环境质量评价。统计分析表明：全县表层土壤地球化学元素含量空间变异小;土壤养分元素中,有机质、氮、钾总体丰富,磷在该县东南部丰富、西北部缺乏,钼在较多地区缺乏,铁、锰、铜、锌均属丰富,硼为中等含量,有效性钙、有效镁含量丰富,有效态硫、有效硅绝大部分为丰富区;表层土壤的环境质量总体为轻度污染,中度污染区零星分布。     

黑河流域中游土地利用变化的环境影响

以黑河流域中游地区为例 ,选取土壤质量、土壤有机碳损失以及河流N、P负荷特征与变化等环境要素 ,分析了干旱内陆地区草地耕种利用和耕地荒漠草原化等现阶段主要的两种土地利用变化形式下这些环境要素的响应特征 .结果表明 :1)耕种利用情况下 ,主要草地类型土壤养分含量显著下降 ,但在 10a左右山地草甸草地养分含量呈亚稳定态 ,而荒漠草地土壤养分有所增加 ;弃耕所导致耕地向荒漠化草原草地转化时 ,平均N、P流失率可达 2 76 .4kg·hm-2 ·a-1和 5 6 3.1kg·hm-2 ·a-1;2 )区域草地转化耕地的利用方式造成土壤有机质含量显著变化 ,并使得土壤有机碳排放达 16 7.73× 10 4 tC ,耕地弃耕转化为荒漠草原草地方式导致有机碳排放 5 5 .14× 10 4 tC ,说明干旱内陆地区土地利用变化对土壤C源汇性质产生明显影响 ;3)土地利用变化形成严重的面源污染问题 ,N负荷平均增加了 5 3.1%～ 73.5 %,TP增加了 34 .1%,初步研究认为黑河中游地带水体N、P富集并呈现不断递增的现象 ,与土壤N、P大量流失变化有关 ,成为内陆地区严重的环境问题之一 .