Background quality for coastal marine waters of the North West Shelf, Western Australia

Water quality surveys were undertaken in February and June of 2003 to determine dissolved concentrations of cadmium, chromium, copper, lead and zinc, total mercury, polyaromatic hydrocarbons, phenols, BTEX chemicals and petroleum hydrocarbons in and around the Dampier Archipelago and Port Hedland. Most sampling sites were located in areas unlikely to be contaminated from anthropogenic sources, but for comparative purposes some sites were also located in potentially contaminated areas. This work was undertaken to provide an estimate of background concentrations for selected metals and organics in the marine waters of the North West Shelf, and to ascertain whether the guideline trigger values from ANZECC & ARMCANZ (2000) are relevant to the region. The results of this study indicate that the coastal waters of the North West Shelf are generally of very high quality. The concentrations of metals were low by world standards, with localised elevations of some metals adjacent to industrial centres and ports. Metal concentrations at the time of sampling met the environmental quality guidelines for a very high level of ecological protection (99% species protection) throughout the sampled area, with the exception of the inner harbour at Port Hedland, where copper and zinc levels were elevated above background, but below the 95% species protection guidelines, which represent a high level of ecological protection. No organic chemicals were detected in any of the samples. The reporting limits were well below the guideline trigger values recommended in ANZECC & ARMCANZ (2000) for a very high level of ecological protection for the five organics for which guideline values were available. The findings of this study suggest that ANZECC & ARMCANZ (2000) 99% species protection guidelines are relevant to the region for all metals analysed, except cobalt, for which the 95% species protection guideline is recommended for use. A set of Environmental Quality Criteria is proposed.本研究于2003年2月与6月开展水质调查，旨在检测丹皮尔群岛（Dampier Archipelago）、黑德兰港（Port Hedland）及其周边海域中镉、铬、铜、铅、锌等溶解态金属，总汞、多环芳烃（polyaromatic hydrocarbons）、酚类、BTEX化学品（BTEX chemicals）以及石油烃类的浓度。本研究大部分采样点布设于人为污染源影响概率较低的区域，同时为便于对比分析，亦在潜在受污染区域布设了部分采样点。本研究旨在估算西北大陆架（North West Shelf）海域内目标金属与有机物的背景浓度，并确认ANZECC & ARMCANZ（2000）发布的环境质量指南触发值是否适用于该区域。研究结果显示，西北大陆架近岸海域整体水质极佳。以全球标准衡量，本次检测的金属浓度普遍偏低，仅在工业中心及港口周边局部区域出现部分金属浓度升高的情况。采样期间的金属浓度在所有采样区域均符合极高生态保护等级（99%物种保护）的环境质量标准，仅黑德兰港内港除外——该区域铜、锌浓度高于背景值，但仍低于代表高生态保护等级的95%物种保护指南阈值。所有采样样本均未检出有机污染物。本次检测的报告限（reporting limits）远低于ANZECC & ARMCANZ（2000）针对5种有可用指南值的有机污染物所推荐的极高生态保护等级触发值。本研究结果表明，ANZECC & ARMCANZ（2000）发布的99%物种保护指南适用于本次检测的所有金属，仅钴除外——推荐针对该金属使用95%物种保护指南阈值。本研究同时提出了一套环境质量标准建议。