Abstract：
The remnants of historical industrial contamination can be detected in many aquatic ecosystems worldwide even at present time. Mrežnica is a river in Croatia that has been, for more than a hundred years, continually exposed to effluents of various industries, which have, in modern time, mostly ceased to operate. Our aim was to establish the level of current contamination and pollution of the Mrežnica river-water and sediments. The study of river contamination at three sites (reference site; site nearby former cotton industry facility in Duga Resa - DRF; industrial zone of Karlovac town - KIZ) in three sampling campaigns (May 2020, April and September 2021) encompassed analyses of physico-chemical water parameters, screening of 369 pesticides, measurement of metal (loid) concentrations in the sediments, and in the dissolved and particulate phases of the river-water. The sediment pollution was assessed through the analyses of total bacteria abundance (by targeting 16S rRNA genes), and their associated metal resistance genes (cnrA, pbrT and czcD) and class 1 integrons (intl1). At the DRF site, industrial organic contaminants that can be traced to textile production were detected (dye and nylon components), as well as increased levels of some metals bound to suspended particulate matter and sediments. At the most downstream KIZ site, occasional high level of industrial herbicide neburon was measured in the river-water, and metal contamination of suspended particulate matter and sediments was evident. Although, based on the comparison with legislation and literature data, the level of contamination was rather mild, the effects on microbial communities were unquestionable, confirmed by increased abundance of the czcD gene at DRF site and the intI1 gene at both industrially impacted sites. Obtained results indicated long-term sediment retention of some industrial contaminants at the places of historical freshwater contamination, and, thus, the necessity for their monitoring even after the termination of contamination sources.
摘要：
即使在目前，也可以在全球许多水生生态系统中检测到历史工业污染的残留物。Mreznica是克罗地亚的一条河流，一百多年来，不断暴露在各种行业的废水中，其中有，在现代,大多停止了操作。我们的目标是确定当前污染水平和Mreznica河水和沉积物的污染水平。在三个采样活动（2020年5月，2021年4月和9月）中对三个地点（参考地点；DugaResa的前棉花工业设施附近的地点-DRF；Karlovac镇工业区-KIZ）的河流污染研究包括对物理化学水参数的分析，筛选369种农药，沉积物中金属(类)浓度的测量，在河水的溶解和颗粒相中。通过分析总细菌丰度（通过靶向16SrRNA基因）来评估沉积物污染，以及它们相关的金属抗性基因(cnrA，pbrT和czcD)和1类整合子(intl1)。在DRF站点，检测到可以追溯到纺织品生产的工业有机污染物（染料和尼龙成分），以及某些金属与悬浮颗粒物和沉积物结合的水平增加。在最下游的KIZ站点，偶尔在河水中测量到高水平的工业除草剂neburon，悬浮颗粒物和沉积物的金属污染很明显。虽然,在与立法和文献资料比较的基础上，污染程度相当轻微，对微生物群落的影响是毋庸置疑的，通过DRF位点的czcD基因和两个工业影响位点的intI1基因的丰度增加来证实。获得的结果表明，在历史淡水污染的地方，一些工业污染物的沉积物长期保留，and,因此，即使在污染源终止后，也有必要对其进行监测。
