Metal forms and dynamics in urban stormwater runoff from a polluted creek system in Melbourne, Australia.

Stormwater runoff contains significant quantities of metal contaminants that enter urban waterways over short durations and represent a potential risk to water quality. The origin of metals within the catchment and processes that occur over the storm can control the partitioning of metals between a range of different forms. Understanding the fraction of metals present in a form that is potentially bioavailable to aquatic organisms is essential for environmental risk assessment.

To help provide this information, the forms and dynamics of metal contaminants in an urban system were assessed across a storm. Temporal patterns in the concentration of metals in dissolved and total suspended solids (TSS) were assessed from water samples, and diffusive gradients in thin-films (DGTs) were deployed to measure the DGT-labile time-integrated metal concentration.

Water samples were collected during baseline, during storm (inclusive of rising and falling storm limbs) and post storm conditions using grab sampling and rising stage sampler methods. Grab samples were collected as triplicates and rising stage samples were collected as duplicates. All DGTs were deployed in triplicates.

All water samples were filtered (0.45 um) and sample filtrate was collected to assess the dissolved metal concentration, dissolved organic carbon concentration, dissolved organic matter characterisation and the concentration of major ions (including alkalinity). The 0.45 um filter was used to determine the TSS metal concentration.

All sampling timepoints along the storm hydrograph were modified into stormtime by calculating the difference in hours (h) or days (d) of the sampling timepoints from the beginning of the storm (time = 0).

雨水径流携带着大量金属污染物，这些污染物会在短时间内进入城市河道，对水体质量构成潜在风险。流域内金属的来源以及暴雨过程中发生的水文过程，决定了金属在多种不同形态间的分配比例。明确金属中可被水生生物潜在利用的形态占比，是开展环境风险评估的核心前提。
为获取相关数据，本研究针对一场暴雨过程中的城市系统内金属污染物的赋存形态与动态变化展开评估。通过水样分析溶解态与总悬浮颗粒物（total suspended solids, TSS）中金属浓度的时间分布特征，并部署薄膜扩散梯度（diffusive gradients in thin-films, DGTs）以测定DGT可提取的时间积分态金属浓度。
本研究在暴雨前基线期、暴雨过程中（包含涨水与退水阶段）以及暴雨后三种工况下，采用瞬时采样法与水位上升阶段采样法采集水样。瞬时采样样品设置三组平行样，水位上升阶段采样样品设置两组平行样，所有DGT装置均设置三组平行部署。
所有水样均经0.45 μm滤膜过滤，收集滤液以测定溶解态金属浓度、溶解有机碳浓度、溶解有机质表征特征及主要离子（包括碱度）浓度；留存0.45 μm滤膜上的截留物以测定TSS结合态金属浓度。
本研究通过计算各采样时间点距暴雨起始时刻（时间=0）的小时（h）或天数（d）差值，将暴雨流量过程线上的所有采样时间统一转换为暴雨时长。