School of Environment and Technology, University of Brighton, Cockcroft Building, Lewes Road, Brighton, East Sussex BN2 4GJ, UK.
Water Res. 2012 May 1;46(7):2324-32. doi: 10.1016/j.watres.2012.01.055. Epub 2012 Feb 8.
It is generally well recognised that suspended particulate matter (SPM), from nano-scale particles to sand-sized sediments, can cause serious degradation of aquatic ecosystems. However, at present there is a poor understanding of the SPM conditions that water quality managers should aim to achieve in contrasting environments in order to support good ecological status. In this article, we analyse long-term SPM data collected from a wide range of reference-condition temperate environments in the UK (638 stream/river sites comprising 42 different ecosystem-types). One-way analysis of variance reveals that there is a statistically significant difference (p < 0.001) between the background SPM concentrations observed in contrasting ecosystems that are in reference condition (minimal anthropogenic disturbance). One of the 42 ecosystems studied had mean background concentrations of SPM in excess of the current European Union (EU) water quality guideline, despite being in reference condition. The implications of this finding are that the EU's current blanket water quality guideline (25 mg L(-1) for all environments) is inappropriate for this specific ecosystem-type which will be non-compliant with the guideline regardless of the intensity of land-use. The other 41 ecosystems studied had mean concentrations below the current EU water quality guideline. However, this does not necessarily mean that the guideline is appropriate for these ecosystems, as previous research has demonstrated that detrimental impacts can be experienced by some freshwater organisms, of all trophic levels, when exposed to concentrations below 25 mg L(-1). Therefore, it is suggested here that it is likely that some ecosystems, particularly those with mean concentrations in the 0.00-5.99 mg L(-1) range, require much lower guideline values in order to be effectively protected. We propose a model for predicting environment-specific water quality guidelines for SPM. In order to develop this model, the 638 reference condition sites were first classified into one of five mean background SPM ranges (0.00-5.99, 6.00-11.99, 12.00-17.99, 18.00-23.99 and >24.00 mg L(-1)). Stepwise Multiple Discriminant Analysis (MDA) of these ranges showed that a site's SPM range can be predicted as a function of: mean annual air temperature, mean annual precipitation, mean altitude of upstream catchment, distance from source, slope to source, channel width and depth, the percentage of catchment area comprised of clay, chalk, and hard rock solid geology, and the percentage of the catchment area comprised of blown sand as the surface (drift) material. The MDA technique, with cross-validation (Wilks-Lambda 0.358, p 0.000), can predict the correct or the next closest SPM range of a site in 90% of cases. This technique can also predict SPM range membership in a probabilistic manner, allowing for an estimate of uncertainty to be made in the allocation of a site to an environment-specific SPM range.
一般公认,悬浮颗粒物(SPM),从纳米级颗粒到沙粒大小的沉积物,都会严重破坏水生生态系统。然而,目前对于水质管理者在不同环境中应达到的 SPM 条件,以支持良好的生态状况,了解甚少。在本文中,我们分析了从英国广泛的参考条件温带环境中收集的长期 SPM 数据(638 个溪流/河流站点,包括 42 种不同的生态类型)。单因素方差分析表明,在处于参考状态(人为干扰最小)的不同生态系统中,观察到的背景 SPM 浓度存在统计学上显著差异(p < 0.001)。在所研究的 42 个生态系统中,有一种生态系统的背景浓度超过了目前的欧盟(EU)水质准则,尽管它处于参考状态。这一发现的意义是,欧盟目前的全面水质准则(所有环境为 25 毫克/升)不适合这种特定的生态系统类型,无论土地利用强度如何,该准则都将不适用。其他 41 个研究的生态系统的平均浓度低于目前的欧盟水质准则。然而,这并不一定意味着该准则适用于这些生态系统,因为先前的研究表明,所有营养级别的一些淡水生物在暴露于低于 25 毫克/升的浓度时,可能会受到不利影响。因此,这里建议,一些生态系统,特别是那些平均浓度在 0.00-5.99 毫克/升范围内的生态系统,可能需要更低的准则值才能得到有效保护。我们提出了一种用于预测特定于环境的 SPM 水质准则的模型。为了开发这个模型,首先将 638 个参考条件站点分为五个平均背景 SPM 范围之一(0.00-5.99、6.00-11.99、12.00-17.99、18.00-23.99 和>24.00 毫克/升)。对这些范围进行逐步判别分析(MDA)表明,站点的 SPM 范围可以作为以下因素的函数进行预测:年均空气温度、年均降水量、上游集水区的平均海拔、距源头的距离、到源头的坡度、渠道宽度和深度、集水区由粘土、白垩和坚硬岩石组成的面积百分比、以及由吹沙组成的集水区表面(漂移)材料的百分比。MDA 技术(交叉验证 Wilks-Lambda 0.358,p < 0.000)可以在 90%的情况下预测站点的正确或下一个最接近的 SPM 范围。该技术还可以以概率方式预测 SPM 范围的成员资格,从而可以对站点分配给特定于环境的 SPM 范围的不确定性进行估计。