Heavy metals are known to be among one of the major environmental pollutants, especially in urban areas, and, as generally known, can pose environmental risks and direct risks to humans. This study deals with the spatial distribution of heavy metals in different pavement joints in the inner city area of Marburg (Hesse, Germany). Pavement joints, defined as the joint between paving stones and filled with different materials, have so far hardly been considered as anthropogenic materials and potential pollution sources in urban areas. Nevertheless, they have an important role as possible sites of infiltration for surface run-off accumulation areas and are therefore a key feature of urban water regimes. In order to investigate the spatial variability in heavy metals in pavement joints, a geospatial sampling approach was carried out on six inner city sampling sites, followed by heavy metal analyses via inductively coupled plasma–mass spectrometry (ICP–MS) and additional pH and organic matter analyses. A first risk assessment of heavy metal pollution from pavement joints was performed.Pavement joints examined consist mainly of basaltic gravel, sands, organic material and anthropogenic artefacts (e.g. glass and plastics), with an average joint size of 0.89 cm and a vertical depth of 2–10 cm. In general, the pavement joint material shows high organic matter loads (average 11.0 % by mass) and neutral to alkaline pH values. Besides high Al and Fe content, the heavy metals Cr, Ni, Cd and Pb are mainly responsible for the contamination of pavement joints. The identified spatial pattern of maximum heavy metal loads in pavement joints could not be attributed solely to traffic emissions, as commonly reported for urban areas. Higher concentrations were detected at run-off accumulation areas (e.g. drainage gutters) and at the lowest sampling points with high drainage accumulation tendencies. Additional Spearman correlation analyses show a clear positive correlation between the run-off accumulation value and calculated exposure factor (ExF; Spearman correlation coefficients (rSP) – 0.80; p<0.00). Further correlation analyses revealed different accumulation and mobility tendencies of heavy metals in pavement joints. Based on sorption processes with humic substances and an overall alkaline pH milieu, especially Cu, Cd and Pb showed a low potential mobility and strong adsorption tendency, which could lead to an accumulation and fixation of heavy metals in pavement joints. The presence of heavy metals in pavement joints poses a direct risk for urban environments and may also affect environments out of urban areas if drainage transports accumulated heavy metals. Finally, we encourage further research to give more attention to this special field of urban anthropogenic materials and potential risks for urban environments. Overall urban geochemical background values, and the consideration of run-off-related transport processes on pavements, are needed to develop effective management strategies of urban pavement soil pollution.

中文翻译：

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城市人行道缝中重金属浓度的空间变异性-一个案例研究

众所周知，重金属是主要的环境污染物之一，尤其是在城市地区，并且众所周知，重金属可能对人类构成环境风险和直接风险。这项研究研究了马尔堡（德国黑森）市区内不同路面缝隙中重金属的空间分布。迄今为止，路面缝被定义为铺路石之间的缝，并用不同的材料填充，这种缝一直未被认为是人为材料和城市地区的潜在污染源。然而，它们在地表径流积聚区可能的渗透位置中起着重要的作用，因此是城市供水制度的关键特征。为了研究路面缝隙中重金属的空间变异性，在六个城市内采样点进行了地理空间采样，然后通过电感耦合等离子体质谱法（ICP-MS）对重金属进行了分析，并进行了附加的pH和有机物分析。进行了路面接缝对重金属污染的首次风险评估。检查的路面接缝主要由玄武砾石，沙子，有机材料和人为人工制品（例如玻璃和塑料）组成，平均接缝尺寸为0.89厘米，垂直深度为2-10厘米。通常，路面连接材料显示出较高的有机物负荷（平均11.0质量％）和中性至碱性pH值。除了高含量的铝和铁外，重金属Cr，Ni，Cd和Pb也是造成路面缝隙污染的主要原因。正如城市地区普遍报道的那样，已确定的人行道连接处最大重金属负载的空间格局不能仅归因于交通排放。在径流积聚区（例如排水沟）和具有高积聚趋势的最低采样点检测到较高浓度。其他Spearman相关分析表明，径流累积值与计算的暴露因子之间存在明显的正相关性（ExF； Spearman相关系数（rSP）– 0.80；p < 0.00）。进一步的相关分析表明，路面中重金属的积累和迁移趋势不同。基于腐殖质和整体碱性pH值环境的吸附过程，尤其是Cu，Cd和Pb的势垒低，吸附趋势强，这可能导致重金属在路面缝隙中的聚集和固定。人行道缝中重金属的存在对城市环境构成直接风险，如果排水输送积累的重金属，也可能影响市区以外的环境。最后，我们鼓励进一步研究，以更加关注城市人为材料这一特殊领域以及城市环境的潜在风险。总体城市地球化学背景值，以及与人行道上径流有关的运输过程的考虑，