Subscriber access provided by UB + Fachbibliothek Chemie | (FU-Bibliothekssystem)
Article
Quantifying diffuse contamination: Method and application to Pb in soil Karl Fabian, Clemens Reimann, and Patrice De Caritat Environ. Sci. Technol., Just Accepted Manuscript • Publication Date (Web): 28 Apr 2017 Downloaded from http://pubs.acs.org on May 1, 2017
Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
Environmental Science & Technology is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.
Page 1 of 23
Environmental Science & Technology
Quantifying diffuse contamination: Method and application to Pb in soil Karl Fabian ,∗,† Clemens Reimann,† and Patrice de Caritat‡ 1
†Geological Survey of Norway (NGU), P.O. Box 6315 Sluppen, N-7491 Trondheim, Norway ‡Research School of Earth Sciences, Australian National University, Canberra ACT 2601, Australia E-mail:
[email protected] Phone: +47 7390 4203
2
Abstract
3
A new method for detecting and quantifying diffuse contamination at the conti-
4
nental to regional scale is based on the analysis of cumulative distribution functions
5
(CDFs). It uses cumulative probability (CP) plots for spatially representative data
6
sets, preferably containing >1000 determinations. Simulations demonstrate how dif-
7
ferent types of contamination influence elemental CDFs of different sample media. It
8
is found that diffuse contamination is characterized by a distinctive shift of the low-
9
concentration end of the distribution of the studied element in its CP plot. Diffuse con-
10
tamination can be detected and quantified via either
11
of the contaminating element to that of an element with a geochemically comparable
12
behavior but no contamination source (e.g., Pb vs. Rb), or (2) comparing the top soil
13
distribution of an element to the distribution of the same element in sub-soil samples
14
from the same area, taking soil forming processes into consideration. Both procedures
15
are demonstrated for geochemical soil data sets from Europe, Australia, and the USA.
16
Several different data sets from Europe deliver comparable results at different scales.
1
(1) comparing the distribution
ACS Paragon Plus Environment
Environmental Science & Technology
17
Diffuse Pb contamination in surface soil is estimated to be 1000 determinations. These are
58
provided by geochemical mapping projects from various geological surveys.
59
Data sets and method
60
Data sets
61
Five published data sets from different soil geochemical mapping projects at the continental
62
(10,000,000 km2 ) to regional (25,000 km2 ) scale are used:
63
1. The continental scale GEochemical Mapping of Agricultural Soil project (GEMAS) 18 ,
64
2. The sub-continental scale Baltic Soil Survey project (BSS) 19 ,
65
3. The continental scale North American Soil Geochemical Landscapes project (NASGL) 20 ,
66
4. The continental scale National Geochemical Survey of Australia project (NGSA) 21,22 , 3
ACS Paragon Plus Environment
Environmental Science & Technology
Page 4 of 23
5. The regional scale Nord Trøndelag project (NTR) 23 .
67
68
Sampling and analytical procedures are described in the cited sources. All data sets contain
69
between 750 and almost 5000 samples. Further requirements for the investigated elements
70
are low detection limits and high analytical precision at the lower end of the data distribution
71
.
72
CDF signatures of contamination and sample media
73
Three different types of contamination will be distinguished: (1) diffuse, (2) strong local to
74
regional, and (3) from scattered local sources. All three processes lead to over-abundant con-
75
centrations of the studied element which characteristically distort its pristine CDF (Fig. 1a-
76
c).
77
Diffuse contamination results from large scale atmospheric transport and mixing of ma-
78
terial from many different sources of local or widespread anthropogenic activities at present
79
and in the past, e.g., industrial and traffic emissions, or the use of fertilizers , including
80
manures, sewage sludges, and other wastes. In contrast, local contamination is deposited in
81
the vicinity of the source and causes a clear, most often exponential (e−d ) or power-law ( e.g.,
82
1/d2 ) concentration gradient in the vicinity of a point source
83
at the continental scale will not necessarily create such a concentration gradient and should
84
not be expected to result in exceedingly high element concentrations.
2,4,24,25
, diffuse contamination
85
How diffuse contamination affects the pristine CDF of an element can be modeled in
86
a simple way. To do this, Fig. 1a first shows the distribution of Ce, an element that is
87
to date not significantly influenced by anthropogenic activities. Its CP plot is based on
88
the GEMAS data 18 for European agricultural soil (Ap horizon) with a median of about 30
89
mg/kg. The other curves in Fig. 1a show the effects of adding various amounts of constant
90
‘diffuse contamination’ to all data points (2, 5 and 10 mg/kg). They demonstrate that even
91
minor amounts of diffuse contamination ( 50 ppm) and at low (1% of determinations with Pb concentration
256
below the detection limit, whilst the CDF for P btop shows few samples with concentration
257
of
