研究表明,，干旱條件會(huì)對(duì)水質(zhì)產(chǎn)生不利影響，并使得包括殺蟲(chóng)劑在內(nèi)的某些化學(xué)物質(zhì)毒性變高,，且更容易在魚(yú)體內(nèi)累積,。
當(dāng)中國(guó)的部分地區(qū)正在經(jīng)歷最為嚴(yán)重的旱情的時(shí)候，美國(guó)南部的部分地區(qū)則正在遭受自1887年以來(lái)最長(zhǎng)的干旱期,，發(fā)表在《綜合環(huán)境評(píng)估與管理》（Integrated Environmental Assessment and Management）上的一篇最新研究表明,，干旱條件會(huì)使得環(huán)境中的某些化學(xué)物質(zhì)對(duì)魚(yú)類和水生生物產(chǎn)生更高的毒性。
該研究發(fā)現(xiàn),，干旱條件會(huì)提高水中自然pH值的變化幅度,。由于諸如氨等一些污染物會(huì)根據(jù)pH值的水平高低而對(duì)水生生物產(chǎn)生更高的毒性，這樣就會(huì)造成危險(xiǎn),。另外,，逾75%的由世界衛(wèi)生組織規(guī)定的基本藥物以及大約三分之一的現(xiàn)代殺蟲(chóng)劑具有化合物的離子化基團(tuán)。當(dāng)擴(kuò)散到環(huán)境中的時(shí)候,，如果表面pH值很高,，這些“弱堿”化合物會(huì)對(duì)魚(yú)類產(chǎn)生更高的毒性。
“該研究表明,，我們可能會(huì)低估或高估某些化學(xué)物質(zhì)對(duì)魚(yú)類的不良影響,，”本研究的共同作者，美國(guó)德克薩斯州的貝勒大學(xué)（Baylor University）環(huán)境衛(wèi)生科學(xué)主任Bryan Brooks博士說(shuō)道,。“對(duì)于使得某些化學(xué)物質(zhì)毒性變高且更容易在魚(yú)體內(nèi)累積的現(xiàn)象來(lái)說(shuō),，干旱條件，特別是受氣候變化影響的那些干旱條件,，如何影響水的pH值變化目前已經(jīng)成為一個(gè)備受關(guān)注的領(lǐng)域,。”
在兩年的時(shí)間內(nèi)，研究人員在不同的時(shí)期內(nèi)從美國(guó)南部的23條溪流中,，采集樣本并測(cè)定一天內(nèi)生態(tài)系統(tǒng)生產(chǎn)與呼吸如何溶解氧含量,，以及磷與氮的含量和pH值如何變化。研究人員發(fā)現(xiàn),，在有史以來(lái)最為干旱的一年當(dāng)中,，水的pH值波動(dòng)范圍很極端，同時(shí)還伴有對(duì)水生生物更高的毒性,。
“全球氣候變化和降水類型變化引起的未來(lái)水資源短缺可能會(huì)對(duì)半干旱地區(qū)的溪流流量產(chǎn)生深遠(yuǎn)的影響,，這會(huì)直接影響水資源管理，”共同作者Ted Valenti博士介紹道,。“氣候多變性對(duì)污染物危險(xiǎn)度的累積影響作用的預(yù)測(cè)可能要求淡水系統(tǒng)的環(huán)境評(píng)估與管理方法的重大轉(zhuǎn)變,。” （生物谷Bioon.com）
生物谷推薦原文出處：
Integrated Environmental Assessment and Management DOI: 10.1002/ieam.202
Influence of drought and total phosphorus on diel pH in wadeable streams: Implications for ecological risk assessment of ionizable contaminants
Theodore W Valenti, Jason M Taylor, Jeffrey A Back, Ryan S King, Bryan W. Brooks
Climatological influences on site-specific ecohydrology are particularly germane in semi-arid regions where instream flows are strongly influenced by effluent discharges. Because many traditional and emerging aquatic contaminants (e.g., pharmaceuticals) are ionizable, we examined diel surface water pH patterns (i.e. change in pH over a 24?h period) at 23 wadeable streams in central Texas, USA, representing a gradient of nutrient enrichment during consecutive summers of 2006 and 2007. The years of our study were characterized by decidedly different instream flows, which likely affected production: respiration (P:R) dynamics and lead to distinctions in diel pH patterns between 2006 and 2007. Site-specific ambient water quality criteria for ammonia, aquatic toxicity of the model weak base pharmaceutical sertraline, and bioaccumulation of select weak base therapeutics were predicted using continuous water quality monitoring data from the sites. Drought conditions of 2006 significantly increased (p?<?0.05) diel pH changes compared to high instream flows of 2007 and the magnitude of diel pH variability was most pronounced at nutrient enriched sites in 2006. Differences in diel pH change patterns between 2006 and 2007 affected predictions of the environmental fate and effects for model weak base pharmaceuticals and ammonia. Overall, site-specific diel pH was more variable at some sites than the difference in mean surface water pH between the two summers. Diel pH variability affected regulatory criteria as 20% of the study sites in 2006 experienced greater than 5-fold differences in National Ambient Water Quality Criteria (NAWQC) for ammonia over 24-h periods. Our study emphasizes the potential uncertainty that diel pH variability may introduce in site-specific assessments and provides recommendations for environmental assessment of ionizable contaminants. Integr. Environ. Assess. Manag. 2011 SETAC.
