Netshiongolwe Ndivhuwo R, Cuthbert Ross N, Maenetje Mokgale M, Chari Lenin D, Motitsoe Samuel N, Wasserman Ryan J, Munyai Linton F, Dalu Tatenda
Aquatic Systems Research Group, Department of Ecology and Resource Management, University of Venda, Thohoyandou 0950, South Africa.
GEOMAR, Helmholtz-Zentrum für Ozeanforschung Kiel, 24105 Kiel, Germany.
Plants (Basel). 2020 Jul 4;9(7):846. doi: 10.3390/plants9070846.
Metal pollution is pervasive across terrestrial and aquatic ecosystems owing to anthropogenic activities. Sediments can accrue high concentrations of metals and act as secondary sources, and thus may be valuable indicators of metal contamination across spatiotemporal scales. In aquatic systems, the extent of metal pollution may be further mediated by transference among sediments and living organisms, with plant metal contaminants potentially predictive of underlying sediment concentrations. The present study thus quantifies the extent of metal pollutants (Na, K, Ca, Mg, Cu, Zn, Mn, B, Fe) across multiple study sites and seasons (cool-dry, hot-wet, hot-dry) in a subtropical river system. Furthermore, uptake by a key macrophyte species, , was examined and correlated with sediment pollution levels among different plant parts. Overall, sediment pollution load indices differed seasonally, being significantly highest during the cool-dry season irrespective of sampling location, suggesting that periods with reduced water flows can exacerbate metal pollution levels in riverine sediments. Also, metal concentrations were highest in upstream wetland sites, indicating a capacity for metal sink effects in these areas. Overall, macrophytes contained high concentrations of select metals, however composition and concentrations differed across plant parts, with roots containing particularly high concentrations of Fe and B. Correlations between sediment and macrophyte concentrations were mostly non-significant, whilst stem Mn and Fe concentrations correlated significantly negatively and positively to sediment concentrations, respectively. The present study identifies key spatiotemporal differences in multiple metal contaminants in an understudied subtropical aquatic system that align with hydrological regime differences. Whilst macrophytes were not found to be major accumulators, or predictors, of metal contaminants in this study, they may collectively play a central role in concentration regulation in aquatic systems.
由于人为活动，金属污染在陆地和水生生态系统中普遍存在。沉积物会积累高浓度的金属并成为二次污染源，因此可能是跨时空尺度金属污染的重要指标。在水生系统中，金属污染的程度可能会通过沉积物和生物之间的转移进一步得到调节，植物中的金属污染物可能预示着潜在的沉积物浓度。因此，本研究量化了亚热带河流系统中多个研究地点和季节（冷干、湿热、干热）的金属污染物（钠、钾、钙、镁、铜、锌、锰、硼、铁）的污染程度。此外，还研究了一种关键大型植物物种对金属的吸收情况，并将其与不同植物部位的沉积物污染水平进行了关联。总体而言，沉积物污染负荷指数随季节变化，无论采样地点如何，在冷干季节均显著最高，这表明水流减少的时期会加剧河流沉积物中的金属污染水平。此外，上游湿地地点的金属浓度最高，表明这些地区具有金属汇效应。总体而言，大型植物含有高浓度的特定金属，然而不同植物部位的金属组成和浓度有所不同，根部含有特别高浓度的铁和硼。沉积物和大型植物中金属浓度之间的相关性大多不显著，而茎中锰和铁的浓度分别与沉积物浓度呈显著负相关和正相关。本研究确定了一个未被充分研究的亚热带水生系统中多种金属污染物的关键时空差异，这些差异与水文状况差异一致。虽然在本研究中未发现大型植物是金属污染物的主要积累者或预测指标，但它们可能在水生系统的浓度调节中共同发挥核心作用。
