Historical trends in contamination of estuarine and coastal sediments: An introduction to the dedicated issue

Abstract

This dedicated issue of ESTUARIES focuses primarily on the use of dated sediment cores for environmental research. The composition of surface waters (river, lake, and coastal) has changed over time. Well known at present are the changes due to the Industrial Revolution, dating from the middle of the last century. These changes are expressed by increased levels of natural components like heavy metals , po lya roma t i c h y d r o c a r b o n s (PAHs), nutrients, and additionally, since the start of this century, xenobiotic compounds like polychlorinated biphenyls (PCBs) and pesticides. Since the early 1960s, regulatory measures have been taken to decrease the amount of pollutants entering our waterways. Because of a lack of data, the extent of past pollution and the effect of recent limitations is often difficult to assess. Befbre the 1960s, metal and nutr ient research was mainly an academic exercise and surface waters were not analyzed on a regular basis. In addition, the analytical methods necessary to analyze the various chemicals enter ing our waterways, in particular, organic compounds, did not exist. The analysis of sediment cores presents a way out of this dilemma. Sediments are continually deposited in lakes, rivers, and estuaries. Most pollutants have an affinity for and adsorb easily onto sediments and fine particles. There tbre , by analyzing cores of undisturlwcl scciinlt'llt, il is I.~s,~ihle to assess the historic P I l u t i ~ m ~1 :~ givcn sysleln and determine the elfi'cl ivt'm.ss <~1' regulalcwy measures, the majority of which were institmt,dsim'r the 1970s. Sedimeu! t:~wes ch~ m~t rt,lh,cl (lilly lilt' history of pollutanl ('ollcr lint, ill a(hlition, the changes in ec~d.gy q~l '.t water b.d),. Igw example, changes il.I t'utrcqflficalic~ll art' relh'cled m organic matter, nil r()gt ' l l , i~h~sphcwc~s, and carbonate content, whih, ]akc m'i~lilicatitu! II'al|sl:tlt's into a change in the ttialcml :lsscmblagcs. I"-r hmger time-related modili,'aliq,ls, c.rt,s can als . Iw used to detect global climale ch:ll|gcs. The use of cored setlimeuls Ic) ret ' ( ) l lS l l ' t l ( ' l t i l t ' chronology of coastal o r es t t i q r i i l ( , ('()lll:tlllin~ltir is not, however, (tev.i(I o1 iw~flfl(,ms aut l cattlioll has to be exercised. Sedimt,.l mixing by biol.gical or physical processes c;m <)hs(' l lr t , lilt' rt'sllits oi)tained by such studies. In a~hliliqm, diagcm.sis and contaminants mobility have Ilit' very carel'ully evaluated in order to exlr;.l('l reliable resHIIs. Studies on dated setlimctll c~wes ]lave many applications and these procec(liugs <fl'tlle Special Session of the Estuarine Rese:lvt'h l"e(h'r:|lion Meelillg held in San Francisco ill N(wemht,r 1991, highlighl some of their current al)lflical iotas ill t,nvironmelltal sciences. One of the m..s t i lnl)()rt ; l l l l restlllS t<) date is the observed declim, in re(ell( yt'ars ()[coll-