Trace elements influenced by environmental changes in Lake Biwa: (II) Regime shifts in the hypolimnion over the last half-century
Trace elements influenced by environmental changes in Lake Biwa: (II) Regime shifts in the hypolimnion over the last half-century
复制标题
琵琶湖环境变化对微量元素的影响：（二）半个世纪以来低水位的变化
DOI：
10.1007/s10201-015-0477-0
复制
发表时间：
2016
期刊：
影响因子：
1.6
通讯作者：
Maruo M
中科院分区：
文献类型：
--
作者：
Sohrin Y;Nakashima Y;Maruo M
琵琶湖北部深部盆地的历史长达43万多年。尽管它自形成以来可能一直是氧化和贫营养的，但人类的影响一直在改变湖泊的条件。在这篇文章中，我们通过汇编文献和我们自己的数据，讨论了过去半个世纪底水化学的长期变化。长期的记录显示，温度上升，溶解氧(DO)减少，底层水中营养物质增加。氧和养分之间的化学计量比表明，其变化与有机物的好氧分解基本一致。这些变化很可能是全球变暖和局部富营养化的结果。特别值得注意的是，自1999年以来，每年最低DO浓度&50微克/公斤−1开始频繁出现在约90微米的深度。底水中的锰浓度在每年的更替期间最低，在层化后期达到最高。在过去的30年里，锰的年最低浓度一直在一个狭窄的范围内(0.25g±0.07g/kg−1，n=0.12)。然而，2007年观察到异常高的锰浓度(高达9.3万微摩尔/公斤−1)，这是由于亚氧沉积物中大量锰的还原释放以及随后底层水的氧化造成的。砷(As)的浓度在过去20多年中以类似的方式逐渐增加，磷(P)是相应的元素，导致2010年的观测范围为17-29nmoL/kg−1。As和P的累积速率分别为0.8nmoL/kg−1年−1和6nmoL/kg−1年−1。
The history of the deep north basin of Lake Biwa extends over 430,000 years. Although it has probably been oxic and oligotrophic since its formation, human impacts have been changing lake conditions. In this paper, we discuss long-term changes in the chemistry of bottom water by compiling literature and through our own data over the last half-century. Long-term records show an increase in temperature, decrease in dissolved oxygen (DO), and increase in nutrients in bottom water. The stoichiometry among oxygen and nutrients indicates that changes are basically consistent with aerobic decomposition of organic matter. These changes are most likely the result of global warming and local eutrophication. Of particular note, yearly minimum DO concentrations <50 µmol kg−1have started to occur frequently at ~90 m depth since 1999. Manganese (Mn) concentrations in bottom water are at their minimum during the turnover period and at a maximum during the late stratification period each year. Yearly minimum Mn concentration has been within a narrow range over the last 30 years (0.25 ± 0.07 µmol kg−1,n= 12). However, abnormally high Mn concentrations (up to 9.3 µmol kg−1) were observed in 2007, caused by reductive release of a substantial amount of Mn from suboxic sediments and subsequent oxidation in bottom water. The concentration of arsenic (As) has gradually increased over the last 20 years in a similar manner, with a homologous element of phosphorus (P), resulting in an observed range of 17–29 nmol kg−1in 2010. The accumulation rate was ~0.8 nmol kg−1year−1for As and ~6 nmol kg−1year−1for P.